3. Biology of reproduction, suckling regimes, growth and development

Transcription

1 Sexual maturity of Awassi ram lambs 3. Biology of reproduction, suckling regimes, growth and development In Awassi ram lambs in Iraq, puberty as defined by the presence of spermatozoa in the testes and epididymides is attained during the first half of the eighth month at a weight of kg. At Abu-Ghraib in Iraq, Ghannam, Madhat and El-Shobokshy (1978a) and Ghannam, Madhat and Eltawil (1978b) examined the onset of sexual maturity and the development of the sex organs of 18 male Awassi lambs which from the age of days and a weight of kg were kept on a ration of lucerne and concentrates supplying normal requirements of energy and protein, and of 18 others on a ration containing 20 percent more protein. Three lambs of each group were slaughtered at the age of 133 days, followed by three more of each group slaughtered at monthly intervals from 171 to 325 days. After slaughter the weight of the reproductive organs and endocrine glands was recorded, and a section of each gland was studied histologically. The epididymis was examined microscopically for the presence of spermatozoa, and the fructose content of the seminal vesicles was estimated. The increase in protein intake of 20 percent above the normal requirements had no influence on the age at which sexual maturity was attained. There was no detectable difference between the two groups in the average weights of body, endocrine glands and reproductive organs at the various ages, save for an increase in the weight of the seminal vesicles and their secretory activity at seven months of age in the group on the higher protein plane. The weight of the testicles increased threefold from seven to eight months of age. At eight months it represented 29 percent of the adult weight. There was little change in the weight of the testes at nine months, but at ten months a greater weight increase occurred, bringing their weight up to 51 percent of the adult weight. The average weight of the epididymis increased similarly. At eight months it was twice the seven-month weight, representing 30 percent of the adult weight, and at ten months it attained approximately 45 percent of the adult weight. The weight of the seminal vesicles markedly increased from seven to eight months, at the latter age coming to twice their seven-month weight and representing 44 percent of the adult weight. From eight to eleven months the weight increased almost linearly to 85 percent of the adult weight. The pituitary, adrenals and thyroid increased gradually in weight until the age of seven months. At eight months the weight of all three glands, but especially of the thyroid, showed a rapid increase. At nine months the weight of the pituitary and adrenals dropped, while that of the thyroid continued its marked increase, to decline only at 11 months. There was no difference in weight between the left and the right testes. The growth of the testes and epididymides at different ages was as shown in Table 3-1. Awassi ram lambs have a well-defined prepubescent period. In all testes examined at days of age, the seminiferous tubules were non-canalized cords, their lining consisting of large genocytes, with relatively large nuclei, and of small supporting cells. The genocytes were located in the centre and the supporting cells around the periphery of the cords. At days a distinct lumen appeared in the majority of the seminiferous tubules. The diameters of the tubules were much larger and the mitotic activity of the genocytes was more in evidence than at the previous test age.

2 TABLE 3-1. Growth of testes and epididymides of male Awassilambs in Iraq at different ages Age at slaughter (days) Live weight Weight of testes (g) Weight of Diameter of epididymis seminiferous (g) tubules ( ) Source: Ghannam, Madhat & Eltawil, 1978b At days and higher ages, all stages of spermatogenesis were evident in the majority of the seminiferous tubules and spermatozoa were present in the cauda of the epididymis. As the transit of spermatozoa through the epididymis of the râm takes about days, sexual maturity was attained during the first half of the eighth month. The growth pattern of the endocrine glands indicated an activation of the pituitary, thyroid and adrenals at seven to eight months, followed by a declining phase of activity at nine months of age. The endocrinological age of sexual maturity, as determined by the peak of the fructose content of the seminal vesicles and the presence of elongated spermatids in the seminiferous tubules, sets in about three weeks before spermatogenesis. At the age of seven months the weight of the seminal vesicles and the content and concentration of fructose were considerably larger in the group on the higher protein level of nutrition than in the control group; this was the only notable difference between the two groups. At eight months the content and concentration of fructose in the seminal vesicles of both groups significantly exceeded that obtaining at other ages, but at nine months a sharp decline occurred and at eleven months the fructose content and concentration were significantly lower than in adult rams. In Lebanon the onset of sexual maturity in Awassi ram lambs occurred at days, two months earlier than in Iraq, but at a similar body weight (29-36 kg). Barr (1969) studied the growth and development of the testes and epididymides of male Awassi lambs kept on a fair plane of nutrition from birth to the age of 48 weeks. At interváls of four weeks two lambs were weighed, slaughtered and their sex organs removed for examination. (See Figs 3-1 to 3-4.) Until the age of 12 weeks the growth rate of the testes and epididymides was slow. Thereafter their weights markedly increased, their rates of growth exceeding that of the body. At the age of one Figure 3-1. Testicular slice from a 1 -week-old Awassi ram lamb (G-gametocytes). (Source: Barr, 1969)

3 Figure 3-2. Testicular slice from a 20-week-old Awassi ram lamb (SG-spermatogonia; Spspermatazoa). (Source: Barr, 1969) Figure 3-3. Epididymal slice from a 1-week-old Awassi ram lamb. (Source: Barr, 1969) Figure 3-4. Epididymal slice from a 20-week-old Awassi ram lamb (Sp-spermatozoa). (Source: Barr, 1969) week the weight of the testis was 2.87 g and of the epididymis 1.62 g on average. At 12 weeks the average weights of the two organs had increased to and 4.57 g, and at 20 weeks to and 12.8 g, respectively. The average length of the testis was 1.62 cm and its breadth 0.75 cm at the age of one week, 3.7 and 2.0 cm, respectively, at 12 weeks, and 8.87 and 5.00 cm at 20 weeks. The epididymides reached maturity at 12 weeks; at this age their previously high columnar

4 epithelium had lowered and the pseudo-stratified epithelium appeared. Until the age of 16 weeks the testes remained in an infantile state. At this age the gametocytes had almost completely disappeared and spermatogonia made their appearance in the sex cords. At 20 weeks the proliferation stage and spermatogenesis commenced and spermatozoa were found in the seminiferous tubules and the lumina of the epididymal coils. The author concluded that under conditions in Lebanon, male Awassi lambs should be separated from the females at not later than five months of age and that they could be used for service at seven months. Well-fed male Awassi lambs of the improved dairy type first show signs of sexual desire at weaning time at the age of three or four months, when they weigh kg. At five to six months they produce normal spermatozoa, and at eight months, when they have reached a weight of kg, they can be employed for service. Management of Awassi rams After weaning, the Awassi ram lambs of the improved dairy type, reserved for breeding, are pastured for four or five months until June. From July to the end of September they are penned up with free access to hay of which they consume approximately 500 g a day. In addition to grazing or hay, they receive unlimited quantities of concentrates until the age of l½ years. The length of the breeding season varies among Awassi flocks according to the flock-master's decision to restrict lambing to a relatively short period or to extend it over eight months or even the whole of the year, and to have their ewes lamb only once a year or more than once. A teaser ram, provided with an apron, is employed to pick out the ewes in heat. The rams serve in the morning before the ewes leave for pasture, and in the evening after their return to the fold. If many ewes come into heat simultaneously, adult rams may also be used for service at adequate intervals during the day. Between the first two services an interval of ten minutes is sufficient. If more than two services are required of a ram, intervals of half an hour are recommended. Young rams, seven to eight months old, should not serve more than three or four times a week. Shepherds of Awassi sheep hold that it is easier to train a ram than a ewe. Every stud ram is given a name early in life and he is trained to come to the sheepman when called by name and to leave again when told to. This training is particularly useful at breeding time when the ewes in heat have to be served according to the mating plan worked out prior to the breeding season. In hand-mating the ewes located by the teaser are trapped in a milking stand. The rams appointed to serve are called one after the other. The ram whose turn has come approaches the ewe and endeavours to push her fat tail with his right foreleg upwards and sideways while mounting. This often requires several attempts. If the fat tail is too heavy to be moved with the leg, the ram dismounts and uses his chest to lift the ewe's tail up. To facilitate service and not to tire the ram, the sheepman will assist by keeping the ewe's tail out of the way. On its introduction into the vagina the penis of the Awassi ram is not horizontal as it is more or less in thin-tailed breeds, but is curved bow-like downward (Hinrichsen & Lukanc, 1978). After service the ram is told to return to his pen. From October on, when the main mating season (during which approximately 85 percent of the ewes are served) is over, the rams go out to pasture with the pregnant ewes. For the ewes not yet in lamb, hand-mating is replaced by pasture-mating. In commercial flocks several rams may accompany them. In stud flocks, where it is important to know the sire of every lamb, a single ram, usually the best one, goes out with the unfertilized ewes. In addition to the pasturage, the rams are given 500 g of concentrates a day. An outstanding ram may be employed in the same or other flocks until its death. One improved ram, whose dam had excelled in both fecundity and milk production, still served in an experimental flock at the age of 14 years without showing any signs of deterioration in libido or fertility. His twin brother, too, was employed in a stud flock to a very great age. Generally, however, rams are culled when they are six or seven years old. Seasonal variations in sexual activity of Awassi rams The principal breeding season of Awassi sheep is in summer. However, in improved flocks breeding begins one or two months earlier than in the flocks of the Arab bedouin and fellahin. To a large extent this may be attributed to a rigorous selection for milk since the lactation yield of ewes lambing early in

5 Figure 3-5 a andb. Seminiferous tubules of an unimprpved Awassi ram in April. (Source: Volcani, 1957) Figure 3-6 a and b. Seminiferous tubules of an unimproved Awassi ram in June and July. (Source: Volcani, 1957) the cool, rainy winter season is less depressed by the heat and drought of the summer than that of latelambing ewes, a large part of whose lactation period coincides with the summer months. In unimproved Awassi rams an examination of the testes reveals maximum spermatogenic activity during the summer months, signs of degeneration of the seminiferous tissue in autumn, and regeneration in spring (Volcani, 1953, 1957). The mean weight of the testes of unimproved Awassi rams is 140 g, and of the epididymis 23 g. During the month of April the mean diameter of the seminiferous tubules is 105, in June and July , in September , and in December close to the June and July figures. In April the seminiferous tubules are lined with a single layer of epithelial cells with acidophile material in the centre, while the connective material between them is sparse. In this month the tubules show very little activity or none at all (Fig. 3-5 and b). In June and July the number of all epithelial cell layers as well as of the sperm cells in the Sertoli cells and the centre of the tubules is large. The hollow of the tubules does not contain round cells, but is filled with the acidophile secretion enveloping the tails of the ripening sperm cells. The connective tissue between the tubules is highly developed (Fig. 3-6 and b). In September spermatogenetic activity is reduced. The cell layers in the tubules show a lack of organization and the presence of primary spermatocytes, but few other forms. Mature sperm cells are seen only around the hollow of the tubules. The latter display a marked degree of destruction, with sparse interstitial tissue (Fig. 3-7 and b). In December the destruction has progressed still further. The division is negligible and there are very few sperm cells or none at all. The lack of organization in the various layers is most conspicuous. There are numerous round cells in the hollow of the tubules and the connective tissue is well developed (Fig. 3-8 and b).

6 Figure 3-7a and b. Seminiferous tubules of an unimproved Awassi ram in September. (Source: Volcani, 1957) Figure 3-8 a and b. Seminiferous tubules of an unimproved Awassi ram in December. (Source: Volcani, 1957) In the epididymis no seasonal differences parallel to those that occur in the testes between the months of high and low spermatogenic activity are found in the diameter of the tubules or the height of the epithelium. In June and July numerous sperm cells are arranged vertically. In September the vortexes are sparser and in December only a few, partly degenerated sperm cells are found. Again, in July secretion is copious, but in September it is moderate to negligible. In the histological structure of the connective tissue between the seminiferous tubules there are no phenomena parallel to those characteristic of the different seasonal activities of the testes (Volcani, 1953). The level of androgens, indicative of sexual activity and a balance between the gonadotrophins, is closely related to fructose and citric acid concentrations as well as to semen voume (Mann & Parsons, 1947; Humphrey & Mann, 1949). Rams in an unimproved bedouin flock pastured with the ewes throughout the year, and improved Awassi rams, either completely isolated from ewes, separated from them merely by a fence or pastured with them throughout the year just as in the unimproved flock but with an additional ration of hay and concentrates all showed the lowest fructose and citric acid concentrations in the semen from March to June. The highest citric acid concentrations, about twice as large as the lowest, occurred from September to November. Peak fructose concentrations varied. In the two flocks, one unimproved and one improved, in which the rams were pastured with the ewes during the whole year, the maximum concentration was observed in October and November, and in the rams completely isolated or fenced off from the ewes, in July and August. The presence of ewes in heat causes a more pronounced difference between peak and minimum fructose concentrations than does isolation of the rams. The practice of introducing the

7 rams into the flock after a period of separation in order to obtain a high frequency of oestrus in a short span of time early in the season makes the peak of fructose concentration appear earlier than it does in rams kept continuously with the ewes or in those fenced off from them (Amir, 1964; Amir & Volcani, 1965a). With regular semen collections, the volume of the ejaculate is largest in autumn and smallest in spring. From the fructose and citric acid concentrations in the semen and the volume of the ejaculate, it may be concluded that the androgenic activity of adult Awassi rams attains its highest level in autumn and its lowest in spring (Amir & Volcani, 1965b). In rams completely isolated from ewes, the highest sperm density obtains from March to June and the lowest from August to January. In rams fenced off from ewes or pastured together with them, fluctuations in sperm density are greater than in isolated rams, with the maximum level occurring from March to May and the minimum in the breeding season from June to November. Again, in isolated rams the maximum sperm number, as calculated from the volume and density of the ejaculate, is found from August to January and the least from March to June. In unimproved Awassi rams that run with the ewes throughout the year, a converse seasonal pattern is observed, with the highest sperm number in spring and the lowest in autumn. In improved rams, fenced off from, or running with, the ewes, there are marked fluctuations in sperm number over the year. Sperm motility is highest in summer and autumn, and lowest, generally, in winter. Occasionally a reduction in sperm motility may occur in bedouin rams in summer too, probably owing to poor pasturage and a Vitamin A deficiency (Amir & Volcani, 1965c). In the semen of Awassi rams isolated from ewes, highly positive correlations exist between fructolysis and semen density and also between fructolysis and initial fructose concentration, while density and initial fructose concentration show a highly negative correlation. Amir and Volcani (1965d) believe that the seasons of the year do not directly influence the fructolytic activity of the sperm cells of Awassi rams, but that this depends on the seasonal changes in sperm density and initial seminal fructose concentration. The oxygen consumption of the spermatozoa rises in the summer and falls in winter and spring. The decrease in the respiratory activity of the spermatozoa, without influence on their motility, seems to be a result of the low winter and high spring temperature prior to shearing, both of which may inhibit the cytochrome oxidase of the cells. To ascertain whether or not some of the seasonal changes in the spermatogenic activity of the testes observed in unimproved rams are owing to malnutrition and Vitamin A deficiency during the dry period of the year, Amir and Volcani (1965e) examined the spermatogenic activity of two improved Awassi rams kept on a high plane of nutrition by regular sperm collection once a week. In the course of two years the rams were subjected to exhaustion tests four times a year during the months of July, October, January and April. On the test days semen collections were made within two or three hours. The maximum number of spermatozoa was obtained in October and the least in January, while the fructose and citric acid contents of 13 ejaculates rose in October and November and decreased in March and April. The lowest mean motility of the spermatozoa occurred in January. Considering a lapse of time of approximately two months between the onset of the spermatogenic cycle and the resultant ejaculate, the authors concluded that the maximum spermatic reserves obtained in October resulted from a pronounced spermatogenic activity in August and the minimum reserves in January from that of November. Hence, the seasonal fluctuations observed in spermatogenic activity appear to be similar in unimproved and improved Awassi rams, albeit smaller in adult improved rams on a high plane of nutrition than in unimproved males pastured throughout the year. In both the unimproved and improved Awassi rams, irrespective of the level of nutrition, regeneration of the seminiferous tubules apparently begins in winter under the influence of increasing daylight. The first signs of this were noticed in the exhaustion tests in March and April. Regeneration continues until the longest days, resulting in the collection of the maximum number of spermatozoa in September. With decreasing daylight, degeneration leads to the lowest level of spermatogenesis in December, followed by the minimum number of spermatozoa in February. The semen does not show the largest fructose and citric acid contents in the month of highest spermatogenic activity, nor the smallest contents at the lowest level of activity. Rather, the fructose and citric acid contents of the semen reflect maximum androgenic activity in October-November, and lowest in March- April. It seems that the FSH secretion influencing spermatogenesis increases and decreases with the changes in daylight length, whereas the changes in LH secretion influencing androgenic activity occur three or four months later. Notwithstanding the observed fluctuations in their sexual activity owing to season or management,

8 Awassi rams may be employed for breeding at any economically advantageous time of the year. At Abu- Ghraib in Iraq, Juma and Dessouky (1969) examined 147 ejaculates collected at fortnightly intervals from four fat-tailed and three docked five-year-old Awassi rams in the course of a year to study the effects of season and docking on volume, mass activity, individual motility, sperm concentration, sperm number, methylene blue reduction time, the hydrogen-ion concentration (ph) and the percentages of dead and abnormal sperm (Fig. 3-9 and Table 3-2). The number of ejaculates collected from undocked rams varied between five and ten, and from docked rams between four and seven a month. All rams were born within a week and received the same feed and management. In both groups the volume of the ejaculates was lowest during winter and highest in the undocked rams in autumn and in the docked ones in summer. Mass activity and individual motility were not affected by docking; the lowest estimates were obtained during winter and the highest from May to September. In both groups the concentration and number of spermatozoa also showed their highest levels from May to September. Docking increased sperm production, in particular in summer. The authors suggest that the superiority in this respect of the docked rams may be because of anatomical or metabolic changes, such as the thickness of subcutaneous fat and the ability of maintaining a lower

9 TABLE 3-2. Seasonal averages of semen characteristics in undocked and docked Awassi rams in Iraq Semen characteristics Group Spring March-May Summer June- August Autumn Sept-Nov Winter Dec- February Volume (ml) normal docked Mass activity (%) normal docked Individual motility (%) normal docked Sperm concentration ( 10 6 ) normal docked Sperm per ejaculate (x 10 6 ) normal docked Methylene blue reduction time (min) normal docked Abnormal sperm (%) normal docked Dead sperm (%) normal docked ph normal docked Source: Juma & Dessouky, 1969 body temperature and respiration rate. In both groups the percentages of abnormal and dead spermatozoa were highest in winter and lowest in summer, but in the semen of the docked rams, as a result of their superior heat regulation, the percentage of abnormal cells in spring and summer was only half that of the intact animals. The ph of the semen of both undocked and docked rams maintained practically the same level throughout the year. Somewhat different results from a study of the characteristics of 155 ejaculates from four fat-tailed sheep and of 121 ejaculates from four docked two-year-old Awassi rams, collected once a week over a period of a year, have been obtained by Majid et al. (1977) in Iraq. The rams were kept during the trial in a semi-open pen and fed green lucerne or hay ad libitum, without pasture or concentrates. Docking attributed to a slight, insignificant increase in semen volume; the effect of month on volume, as shown in Table 3-3, was also insignificant. The highest sperm concentration in the semen of the intact rams was in March and in that of the TABLE 3-3. Monthly variation in average semen volume of undocked and docked Awassi rams in Iraq (ml) Group Fat-tailed Docked December January February March April May June July August September October November Average Source: Majid et al., 1977

10 docked rams in November; in both groups the lowest concentration was in December. Again, the highest motility in the semen of both groups was recorded in March, and the lowest in the intact rams in February and in the docked ones in December. The semen of the docked rams was superior in mass activity and sperm concentration to that of the undocked ones. Docking had no significant effect on the fructose and ascorbic acid contents of the semen. The highest fructose contents were observed during October and the lowest during August, the highest ascorbic acid contents during the late summer and autumn and the lowest during March. Nevertheless docking improved the quality of the semen, as indicated by the significant ph reduction. Generally, the semen was of the highest quality in the period from March to June. The ph tended to drop in the intact Awassi rams from April to June, and in the docked rams from October to November. Management of the female lamb After weaning, the female lambs accompany the ewes in lamb to pasture. During the first week, when they are not yet used to grazing, they are still given unlimited quantities of hay and concentrates at night; thereafter, until the beginning of the rainy season in November, only concentrates. After the first rains the lambs remain in the shed where they receive 1 kg of concentrates, 300 g of hay and an unlimited quantity of straw each day until there is sufficient new pasturage, generally in January. With the renewed grazing, their ration is reduced to 500 g of concentrates a day. Female lambs born early in the season come into heat in August at the age of nine or ten months, and are served or inseminated at the first heat. Those in which natural oestrus is delayed are given a hormone treatment in September or October, on condition that they weigh not less than 50 kg. About 70 percent of the young ewes lamb as yearlings, the rest at the age of two years. From January on the yearlings that conceived in August, September or October are prepared for their first lactation by a daily ration of g of concentrates in addition to natural or sown pasture In unimproved Awassi flocks the ewes lamb for the first time at the age of two years or more; lambing at the age of one year is practically unknown. In improved flocks the same condition continued for many years. Hirsch (1933) reported that in the early 1930s in a well-managed flock of a communal settlement and in a year of rich pastures, the female lambs came into heat prematurely and lambed at the age of one year, with the result that their growth was retarded. In the following years the rams were therefore separated from the female lambs with which they had previously gone to pasture. Eventually, as a result of improved feeding and management and selection for high milk yields, the age of first lambing was advanced by a year in part of the young females without detriment to their growth. In 1942, only two of 158 registered ewes, or 1.26 percent, lambed as yearlings, but in 1953 already 165 of 916 registered ewes (or percent) lambed as yearlings (Finci, 1957). In a large flock belonging to a communal settlement, the first instances of the lambing of yearlings occurred in two isolated years, 11 and 19 years after the foundation of the flock. However, 22 years after its establishment, lambing at one year of age became a regular feature, rising, with annual fluctuations, to a peak of one-third of all first-lambing ewes. During a period of 30 years, from 1929/30 to 1959/60, when the use of hormones to induce early oestrus had not yet been introduced, the percentage of lambings of yearlings within the total number of first lambings in this flock was as shown in Fig Figure Number of lambings of yearling ewes as a percentage of total number of first lambings. (Source: Epstein & Herz, 1964) In one flock, newly established with 250 two-month-old lambs purchased from four different farms, 169 (or 67.6 percent) lambed as yearlings (Finci, 1957). In another, medium-sized flock, set up in 1953 at an agricultural school in the south of Israel with foundation stock of highly improved two-month-old lambs, 85 percent lambed for the first time at the age of one year without hormone

11 TABLE 3-4. Average age of yearling ewes on lambing day Age Yearlings (days above 1year) Number % Total Source: Finci, 1957 application (Epstein & Herz, 1964). In 17 registered flocks, the mean age of yearlings at lambing was 15 1 / 2.months. The distribution of their ages on the day of parturition is shown in Table 3-4. The sexual season of the Awassi ewe In unimproved Awassi flocks the breeding season is to a large extent determined by the conditions of pasture. The ewes come into heat only when spring and summer grazing has restored the weight lost in the preceding period of drought and has brought them back to a fair condition. The mating season lasts approximately from June to September, so that lambs are born when there is enough pasture for the ewes in milk and for the young lambs. Occasionally oestrus occurs earlier in the season and since the rams are running with the ewes all year round, lambs may be born before the pastures provide sufficient nourishment for the ewes to have enough milk and for their lambs to develop normally. Nor is oestrus at the usual breeding time always a success, for delayed or scanty winter rains and poor pasture growth in spring may be calamitous for the whole flock, but especially for ewes in lamb or in milk, young lambs and aged animals. In 391 adult Awassi ewes of an experimental flock in Israel, the first oestrus in the mating season was observed toward the end of June, rising to a peak in the first half of August, to fall again by the first week of October, after which no animal with first oestrus was left (Table 3-5). In Lebanon, in an experimental flock of 50 well-fed Awassi ewes accompanied by mature teaser rams which were changed at weekly intervals, oestrus reached its peak with regular cycles in August and September, but was still maintained on a fairly high level until December. From January to April the heats markedly decreased in number, and from May to July ceased altogether. The number of heats for each ewe ranged from five to 15, with an average of ten. The length of the mating season varied between 150 and 255 days, with an average of 165 days (Barr, 1968). In Israel, the sexual season of 11 improved Awassi ewes, two-and-a-half to four-and-a-half years old, which were not mated for a whole year, was studied by Amir (1964) and Amir and Volcani (1965a). The animals were kept on a high plane of nutrition and their pens were lit at night in accordance with general practice in improved Awassi dairy flocks in Israel. The ewes exhibited an average of 12 (9-15) heats from June to April. The authors suggest that the sexual season of the improved Awassi ewe may be even longer than that found in their trial since accurate observation began only a month after the beginning of the normal breeding season. It would therefore appear that in conditions of good feeding and sound management, a large percentage of Awassi ewes may be bred practically throughout the year. This may be attributed to the origin of the Awassi in a subtropical region where the seasonal variation in daylight length is relatively small. In stud and commercial dairy flocks of improved Awassi sheep, the breeding season generally lasts from May to December. The spread of lambing in adult and yearling ewes over two-thirds of the year avoids the excessive burden of work of a restricted lambing period. From January to April the rams are separated from the ewes and service is discontinued, although some females may come into heat during this time. Discontinuance of mating is due to the undesirability of having lambs born during the hot season of the year when the young lambs do not thrive well, digestive troubles are

12 frequent, and the milk production of the ewes is adversely affected by the heat. However, there are also many commercial flocks in which the rams accompany the ewes for a major part of the year and are separated from them for only a month before the beginning of the mating season in the middle of June or in July, depending on local conditions. The onset of the breeding season of Awassi ewes may be advanced by the introduction of rams, until then separated from the females, into the flock of ewes when their ovaries are already active. The ewes react to the sudden exteroceptive stimulus aroused by the presence of the males by coming into heat after a short time. A study in a number of Awassi flocks extending over several years has shown that there are two main waves of oestrus following the introduction of rams, each lasting from two to six days. The peak of the first wave occurs about the eighteenth day and that of the second one on the twenty-fifth to twenty-sixth day of the presence of the rams. Between the two peaks there is an interval of seven to ten days. The incidence of the first oestrus following the joining of both sexes increasingly lessens with the growing interval between the introduction of the rams into the flock and the onset of the natural breeding season (Eyal, 1958). No statistically significant trend for the onset of oestrus to be centred around a certain time of day was found by Schindler and Amir in 403 Awassi ewes observed from August to January in three consecutive years (Table 3-6). But in an Awassi flock in Lebanon, 67 percent of heats were detected in the morning and 33 percent in the afternoon (Barr, 1968). TABLE 3-5. Distribution of first oestrus in adult Awassi ewes in the mating season by fortnights Period Percentage of first oestrus June, 2nd fortnight 1.2 July, 1st fortnight 10.8 July, 2nd fortnight 18.7 August, 1st fortnight 37.2 August, 2nd fortnight 17.4 September, 1st fortnight 8.4 September, 2nd fortnight 4.3 October, 1st fortnight 2.0 Source: Goot, 1966 TABLE 3-6. Time of onset of oestrus in 403 Awassi ewes Hour of day Number of ewes Source: Schinder & Amir, 1972 In the same Awassi flock in Lebanon, the length of the oestrous cycle in 288 normal heats varied between 15 and 20 days, with an average of 18 days. The duration of cycles was regular in August and September, becoming irregular toward the end of the breeding season (Barr, 1968). In improved Awassi dairy ewes in Israel, the mean length of the oestrous cycle has been reported by different workers to be 17.4 days in August and 17.3 in September. In 11 ewes that were not mated for a whole year, the average duration of the oestrous cycle was 18 days, varying between 16 and 21 days. During the months from September to November, the interval between two successive heats was shorter than from December to February (Amir, 1964; Amir & Volcani, 1965a). In a study on the length of 252 oestrous cycles of 64 Awassi ewes, Schindler and Amir (1972) found an average duration of 17 days and ten hours, ranging from 15.5 to 20 days (Fig. 3-11). At an experiment station, about 70 percent of recurrent heats had intervals of days, the remaining 30 percent abnormally shorter or longer intervals (Table 3-7). Excessively long intervals may be a result of silent heats or the death of a fertilized ovum or embryo. In an Awassi flock in Lebanon, the duration of 347 heats ranged from 16 to 59 hours, with an average of 29 hours. Nine percent of the heats were silent as manifested by the occurrence of multiple cycles accompanied by the absence of a mating response (Barr, 1968). In a study on the length of 320 oestrous cycles in 65 adult Awassi ewes, Schindler and Amir established an average duration of 35.3 hours, varying between a minimum of 16 hours and a maximum of 84 hours (Fig. 3-12). The Awassi ewe displays few outward signs of oestrus. She stands quietly in front of the ram for mounting. Loss of appetite is marked. The os uteri opens at the onset of the oestrus, sometimes 4-52 hours earlier or a few hours later. The vulva is slightly swollen, and the vaginal mucosa, varying

13 Figure Average oestrous cycles of 64 Awassi ewes (3-5 cycles per ewe). (Source: Schindler &Amir, 1972) TABLE 3-7. Oestrous intervals in adult Awassi ewes Interval (days) Recurrent heats Number % Total Source: Goot, 1966 TABLE 3-8. Monthly distribution of lambings in an Awassi flock in Lebanon Month No. of lambings November 22 December 299 January 529 February 107 March 29 April 10 May 2 June 2 Source: Choueiri, Barr & Khalil, 1966 Figure Average duration of oestrus in 65 Awassi ewes (4-6 cycles per ewe). (Source: Schindler & Amir, 1972)

14 between pale rose and red in colour, is congested until a short time after ovulation. Two to three days before the beginning of oestrus a thick, creamy white or yellowish mucous secretion accumulates around the external os of the slightly dilated cervix, indicating the rise of the oestrogen level. At the onset of oestrus, or a little before or shortly after, this is usually replaced by a copious, cloudy or clear secretion. Its presence indicates that the ewe is still in the first part of the oestrous period. The flow of mucus is strongest at the height of the heat. The cloudy or transparent secretion generally disappears after a lapse of about two-thirds of the total oestrous period, giving way to a white, more viscous discharge which indicates the decline of oestrogen concentration, the approach of the end of oestrus, and the nearness of ovulation. Toward the end of the heat the viscous secretion is followed by a thick creamy or cheesy one, which remains for two or three days after completion of oestrus (Barr, 1968; Schindler & Amir, 1972). In an experimental Awassi flock in Lebanon, 25 ewes were slaughtered after four successive oestrous cycles at different phases of the fifth cycle and their reproductive organs examined. Pro-oestrus was found to be short and rather indefinite and the onset of oestrus abrupt, while the cessation was gradual. The Graafian follicles were fully mature and bulged above the ovarian surface, displaying a tense structure to the touch for 4-29 hours, with an average of 16 hours. There were 11 ovulations from the right, 12 from the left, and two from both ovaries. During heat, the uterine horns and musculature were tonic and erect. In the course of five to eight days after the onset of heat, the corpus luteum developed to maturity, being conical in shape, about 1 cm in diameter and greyish-red in colour. Its regression commenced on the thirteenth day after the commencement of oestrus, taking a gradual course until its termination with the sudden manifestation of heat (Barr, 1968). Observations with a universal peritoneoscope of follicular changes preceding and following ovulation in adult Awassi ewes, beginning 24 hours after the onset of oestrus and continuing at intervals of six hours until the rupture of one follicle, showed that six hours before the final inspection, the follicle had grown considerably, bulging above the surface of the ovary. In its translucent centre there was a net of tiny blood vessels. After rupture of the follicle, a small blood stain and a slight depression were observed in its centre, and sometimes a small blood clot was prominent above the surface of the ovary. The time range of ovulation was from 12 hours before to eight hours after the end of oestrus, with an average occurrence within an hour after the termination of heat. In Awassi ewes with long oestrous cycles there was a tendency for ovulation to precede the end of oestrus, while in ewes with shorter heat periods ovulation usually occurred after the end of oestrus (Schindler & Amir, 1972). In unimproved Awassi sheep with pasture feeding throughout the year, the height of the lambing season is generally one or two months later than in the improved dairy type. But in a well-fed flock in Lebanon, more than half of lambings had already occurred by January (Table 3-8). In a stationary Awassi flock at the American University farm in Lebanon in which the rams were kept with the ewes throughout the year, the lambing percentages given in Table 3-9 were recorded for the period (Rottensten & Ampy, 1971a). The same authors compared the lambing performance of Awassi ewes under two different breeding systems: I - During the period , rams were kept with the ewes throughout the year; and II - In they joined the ewes for periods of two months each, in October-November, February-March and June-July, and were separated from them during the other months of the year. Under the latter system a considerable proportion of the ewes conceived outside the normal breeding season and 63 percent of the lambings occurred at eight-month intervals, thus increasing the annual lambing performance. The conception rate amounted to TABLE 3-9. Bimonthly lambing percentages in Awassi ewes in Lebanon Months Lambing % January-February 59.4 March-April 10.4 May-June 1.9 July-August 0 September-October 7.9 November-December 20.4 Source; Rottensten & Ampy, 1971 a TABLE Annual lambing performance under two different breeding systems in Lebanon Breeding system I II No. of ewe-years No. of lambings Annual lambing percentage Source: Rottensten & Ampy, 1971 b

15 TABLE Monthly lambing percentage in Awassi ewes in Syria Month Lambing percentage November 6 December 47 January 37 February 8 March 0 April 2 Source: Juma & Faraj, 1966 TABLE Distribution of lambings throughout the lambing season in Iraq Month Lambings Number % October November December January February Source: Husnaoui & Fox, 1967 TABLE Distribution of lambings in improved Awassi sheep in Israel by fortnights Adult ewes Yearlings Month Date Numb er % Numb er % October November December January February March April May June Total Source: Finci, percent of available ewes in October-November, 58 percent in February-March, and 43 percent in June- July (Table 3-10). In Syria, at the University of Aleppo School of Agriculture, the main lambing month in an Awassi flock derived from various desert flocks and regions was December, followed by January (Table 3-11). In Iraq, the main Awassi lambing season appears to be still earlier than in Lebanon and Syria, namely in November. At the Abu-Ghraib Experiment Station, Juma and Faraj recorded the monthly distribution of lambings in five consecutive lambing seasons given in Table In improved Awassi flocks in Israel the distribution of lambings, with one lambing a year, ranges around the peak month of December for adult ewes and April for yearlings (Table 3-13 and Fig. 3-13). In an Awassi flock in Lebanon, the average interval between lambing and the following oestrus was 214 days. After the birth of male lambs, the interval was found to be three days shorter than with female lambs, but the difference was not statistically significant (Choueiri, Barr & Khalil, 1966). In the improved type of Awassi in Israel, ewes lambing early in the season may come into heat again toward the end of the year, approximately 40 days after lambing, and on many farms these are then mated or inseminated. Of the adult ewes of a flock percent may thus lamb once more, increasing the total annual milk yield and number of lambs for each ewe.

16 Figure 3-13, Seasonal distributioni of lambing. (Source: Finci, 1957) Trials to obtain two lambings a year in improved Awassi ewes were conducted by Morag and Eyal (1971) in a flock of 700 Awassi ewes in the northern Negev, and in another one of 450 ewes in the Plain of Esdraelon. The level of feeding and management of the two dairy flocks was similar. The ewes received 0.8 feed unit a day for maintenance and 0.8 feed unit for the production of each kilogramme of milk, including an estimated daily quantity of 900 g of milk consumed by the lambs of one of the two flocks until weaning at 40 days. In the fourth month of pregnancy a supplement of 0.4 feed unit, and during the fifth month 0.6 feed unit, were added to the daily ration. In the first trial, 166 ewes which had lambed at the end of November or the beginning of December were separated from their lambs six hours after parturition and the lambs were reared artificially. Between the twelfth and eighteenth day after lambing, 71 of the 166 ewes received five intramuscular injections of 16 mg of progesterone in an oily solution on five consecutive days and a final injection of 500 IU of PMS on the sixth day. The remaining 95 ewes did not receive hormone treatment. Rams stayed with the ewes for 100 days after lambing, except at milking time. The conception rate was lower in the ewes treated with hormones than in the control group, namely 49 percent as against 59 percent. The interval between previous lambing and conception was 52 days in the ewes without hormone application and 49 days in those that were treated. With hormone treatment, the average number of live births from two consecutive pregnancies in a single year was 2.59, as against 2.34 without hormone treatment. The second trial included 83 ewes that had lambed during the first fortnight of September. The lambs stayed with their dams for suckling during the night until weaning at 40 days. Rams accompanied the ewes for 100 days from the time of lambing. Seventy-four ewes (or 89 percent) conceived during this time, while nine (or 11 percent) did not become pregnant. The average interval between lambing and conception was 65 days. The mean number of live births from the two consecutive pregnancies within one year was 2.78 as against 1.33 lambs from the single pregnancies of the nine ewes that did not conceive in the 100 days after lambing (Morag & Eyal, 1971). Artificial insemination of Awassi ewes Artificial insemination has been practised in many Awassi flocks in Israel in the past and is still continued in several of them as a labour-saving device at mating time and as a means of genetic improvement. It permits the employment of a small number of the best proven sires and the wide application of progeny-testing. A single ejaculate can fertilize a large number of ewes independent of location and the time of ejaculation or oestrus. Finally, the artificial insemination of Awassi ewes is indispensible in cross-breeding with thin-tailed rams, such as the East Friesian, which are unaccustomed to lifting the fat tail of the ewe for mating. The semen, ejaculated into an artificial vagina, is commonly used in the fresh undiluted state. Table 3-14 gives the characteristics of semen from five two- to five-year-old Awassi rams, examined by Schindler, Volcani and Eyal during five consecutive breeding seasons (June-August) for the purpose

17 of artificial insemination. Considerable individual differences in semen quality, concentration and total number of spermatozoa were found by the authors in 11 Awassi rams with at least four ejaculates each (Table 3-15). A highly significant correlation exists between the volume of an ejaculate and the number of spermatozoa it contains ; there is no correlation, however, between the volume of an ejaculate and the concentration of spermatozoa. Since the volume occupied by the spermatozoa is relatively small (l/10 9 sperm cells occupy l), it may be inferred that a larger volume of an ejaculate is mainly the result of an additional quantity of secretions from the accessory glands and only to a small extent is it because of a larger number of spermatozoa. However, as large ejaculates generally contain more sperm than less voluminous ones, they are superior for artificial insemination. A larger number of spermatozoa in an ejaculate is also usually accompanied by a higher quality of spermatozoa, as indicated by the positive correlation between the number of spermatozoa in an ejaculate and the percentage of sperm with progressive motility. TABLE Average characteristics of Awassi semen Characteristics Number of samples Mean value Volume of ejaculate (cc) No. of spermatozoa/cc (millions) No. of spermatozoa/ejaculate (millions) Motile spermatozoa (%) Life span of spermatozoa to 30% motility (days) Source: Schindler, Volcani & Eyal, 1957 TABLE Average values of semen volume, concentration and total number of spermatozoa for individual rams Average value Volume (cc) Spermatozoa/cc (millions) Spermatozoa/ ejaculate (millions) Highest Lowest Source: Schindler, Volcani & Eyal, 1957 The quality of Awassi semen decreases with a reduction of the interval between ejaculations from four or more days to one. For artificial insemination, semen quality also declines rapidly with repeated ejaculations at intervals of only one or two days (Fig. 3-14; Table 3-16). A higher percentage of abnormal sperm tailless, misshapen or with tapering heads, enlarged middle pieces, or adhered, coiled or bent tails appears in the ejaculates. In addition, such increased use of Awassi rams reduces their libido (Schindler, Volcani & Eyal, 1957). The success of artificial insemination depends to a marked degree on its timing in the hours of oestrus. Amir and Schindler (1972, 1974), using a single dose of 0.1 cc of fresh undiluted semen with