Effect of feed restriction method during rearing on growth and blood indices of stress in broiler breeder

Effect of feed restriction method during rearing on growth and blood indices of stress in broiler breeder R.VAKILI 1 *, F. AKBAROGLI 2 1 Faculty/ Department of Animal Science, Islamic Azad University branch of Kashmar-Iran, 2 Ph.D student of Rural Planning, Ferdowsi University,Mashhad-Iran * Email: rvakili2000@yahoo.com Feed restriction has become a common practice among poultry breeders in order to limit the body weight of breeding birds at sexual maturity and prevent over stimulation of the ovary. Some typical feed restriction methods for broiler breeders are every day, five days a week, six days a week and skip-a-day. The present study was conducted to determine the effect of four feed restriction methods (every day, five days a week, six days a week and skip-a-day) in the rearing of broiler breeders on growth, metabolic status and blood indices of stress. One hundred sixty 1 day old Lohman female chicks were housed in an windowless house. Chicks were raised in floor pens littered with wood shavings.for the first 2 weeks of life, food and water provided ad libitum. At the age of 3 weeks chicks were randomly divided into 4 feeding groups, 40 individuals per group (four replicates with 10 individuals per replicate). Upon arrival, birds were weighed, wing-banded, and fed according to Lohman Breeder Manual until 22 wk of age.effects were compared of four methods of feed restriction during 3 to 22 wk of age on the body weight, uniformity and blood indices of stress pullets. The results showed that body weight, body weight uniformity and feed efficiency in fasted pullets at the age of 22 wk were not affected by feeding regimen. However, pullets treated by skip-a-day feed restriction compared with other treatments reduced body weight and feed efficiency and increased plasma cholesterol (P<0.05) and Heterophil/ lymphocyte ratio. Besides,the highest body weight uniformity was reached at the end of breeding period in the six days a week method. Plasma glucose in fasted pullets at the age of 22 wk was not affected by feeding regimen. Keywords: broiler breeder; Feed restriction; Growth; metabolic status; stress Introduction Broiler breeder stocks have been intensively selected for faster growth rates and higher yields of breast meat. The birds must have the genetic potential for growth as well as the ability to effectively reproduce (Robinson et al.,1993a). It is apparent that the fast growth rate of current broiler strains is not accompanied by a satisfactory level of welfare including health (Report of the Scientific Committee on Animal Health and Animal Welfare of the EU Commission 2000). The management practice of broiler breeder females includes the restriction of feed allowance during rearing to limit the body weight of breeding birds at sexual maturity (about 24 weeks of age), to reduce related health problems, and to increase fertility. Although restricted feeding prolongs the time to reach sexual maturity (Leeson and Summers, 1983), the added values in terms of increased egg production, increased fertility, hatchability, egg quality, reduced number of double-yolked or malformed eggs, and reduced mortality (McDaniel et al., 1981; Leeson and Summers, 1983; Katanbaf et al., 1989; Hocking et al., 1987, 1989; Fattori et al.,1991; Yu et al., 1992a; Hocking, 1993) far outweight this delay in starting lay.some typical feed restriction methods for broiler breeders are every

day, five days a week, six days a week and skip-a-day.the amount of restriction and duration of restriction, however, vary between methods, and, most certainly, the amount of gain differs.the duration of feed restriction to broiler breeder chickens has now become an important issue of animal welfare because feed restriction can act as a stressor on the animal (FAWC, 1998). The main welfare problems of broiler breeders are related to the severe feed restriction method. The aim of this study was to determine the effect of four quantities feed restriction methods (every day, five days a week, six days a week, skip-a-day) during 3 to 22 week of age on the body weight, uniformity, feed efficiency and blood indices of stress in pullets of broiler breeder. Materials and methods One hundred sixty 1 day old Lohman female chicks were used in the experiment. Chicks were housed in an windowless house were raised in floor pens littered with wood shavings and supplied with suspended drinkers. For the first 2 weeks of life they were kept in pens 200 100 100 cm (w d h) (12 individuals per pen) with food and water provided ad libitum. At the age of 2 weeks chicks were randomly divided into 4 feeding groups, 40 individuals per group (four replicates with 10 individuals per replicate).upon arrival, birds were weighed, wing banded, and fed according to Lohman Breeder Manual until 22 wk of age. The amount of feed allowance to birds depended on the experimental method (every day, five days a week, six days a week, skip-a-day). All birds had unrestricted access to water. Birds were fed a starter diet from 0 to 5 wk of age (2,750 kcal/kg metabolizable energy, 18.5% crude protein) followed by chick grower diet (2,700 kcal/kg metabolizable energy, 15.5% crude protein). Four weeks before the expected start of egg laying, the birds were fed prelay feed (2,725 kcal/kg metabolizable energy, 16 % crude protein). The photoperiod was 23 h light (L) and 1 h dark (D) during the first week. Thereafter, light was decreased by 3 to 4 h/wk to 8 L: 16 D at Week 6. Birds were photo stimulated from 19 wk of age onward by increasing the photoperiod by 2 h weekly to reach 14L:10 D at 21 wk of age. Body weight was recorded at 22 week of age. Also coefficient of variation for body weight uniformity and feed efficiency were measured. At the end of the experiment at 22 weeks of age, blood samples from the brachial vein were collected using a heparinised syringe. The blood was transferred into chilled tubes and then centrifuged. The plasma was removed and stored at -20 C until assayed for metabolic parameters. Metabolic parameters in plasma (total protein, uric acid, glucose, triacylglycerols, cholesterol) were determined with the commercially available kits (Pars Azmon, Iran) using the Ependorf Auto Analyzer (Epos 5060).The Heterophil/lymphocyte (H/L) ratio was determined with differential leukocyte count by counting a minimum of 100 consecutively encountered cells as the observer moves across fields within the counting area. The effects feeding treatment on body weight and metabolic parameters were estimated by one-way ANOVA. Statistical differences were assessed by Duncan s multiple range tests (General Linear Models procedure; SAS Institute, 1985). P-values <0.05 were considered statistically significant. Results and discussion The obtained results of the experiment showed that body weight, bodies weight uniformity and feed efficiency in fasted pullets at the age of 22 week were not affected by feeding regimen(p < 0.05).Table1 summarizes the results for body weight at 22 wk. It also shows the body weight uniformity (Coefficient variation) and feed efficiency for the four groups of chickens. The body weights were negatively correlated with days number of starvation in four physical feed restriction methods. The body weight and feed efficiency was highest for the every day group and lowest for the skip-a-day group.the data also show that the highest bodies weight uniformity get at the end of breeding period in six days a week method.

TABLE 1. Body weights, body weight uniformity and feed efficency at 22 week of age for the broiler breeder pullets fed under different feed restriction methods during rearing Every day six days a week five days a week Skip-a-day Body weight (g) Uniformity (%) Feed efficency (%) 2459 8.51 29 2408 8.01 28 2377 12.09 27.75 2270 8.69 26.5 Table 2 summarizes the results for metabolic parameters.the glucose concentration,protein content and triacylglycerols levels in plasma were not changed in pullets exposed to different quantitative food restriction methods. The uric acid content in plasma of the five days a week group was significantly lower in comparison with all other groups.on the other side cholesterol levels in plasma of the skip a- day group were significantly increased in comparison with all other groups. TABLE 2. Glucose concentration,total protein, triacylglycerols levels, uric acid content and cholesterol at 22 week of age for the broiler breeder pullets fed under different during rearing 1 Every day six days a week five days a week Skip-a-day Glucose (mg/dl) Total protein (g/dl) Triacylglycerols(mg/dl) Uric acid (mg/dl) Cholesterol (mg/dl) 176 3.98 142 8.42 a 182 b 177 4.06 76 7.24 ab 192 b 176 3.91 77 6.12 b 201 b 187 3.91 102 7.08 ab 240 a a b Means within a row lacking a common superscript differ (P < 0.05). In pullets treated by skip-a-day feed restriction hetrophil to lymphocyte ratio elevated in comparison with all other groups(figure 1). Hetrophil to lymphocyte ratio 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 every day six days a week five days a week skip a day Feed restriction method Figure 1 Effect of feed restriction method on hetrophil to lymphocyte ratio at 22 week of age for the broiler breeder pullets fed under different feed restriction methods during rearing The results of this study show that subjecting pullets to the skip-a-day method, the body weight and the feed efficiency were lower. Results of body weight correspond with results reported by other authors in broiler breeder pullets(bartov et al. 1988; Bennett et al.1989;peak et al.2000).the body weight in 22 week age for skip-a-day group was nearest to recommended body weight (2265g) than other groups.results from other experiments where birds are fed identical quantities of feed indicating

every day feeding to be 6% more efficient than skip-a-day feeding.when fed skip-a-day,the bird must store nutrients (body fat and some body protein) which must be utilized by the bird for growth and maintenance the following day when it has no access to feed. Unfortunately this deposition and reutilization of nutrients is not 100% efficient (Leeson and summers, 2000). Studies of models of physiological stress in chickens using the treatment with ACTH or corticosterone showed that the metabolic changes associated with stress in chicken are increased plasma glucose, total proteins, triacylglyceroles and cholesterol (Davison et al.1983; Latour et al. 1996; Puvadolpirod and Thaxton 2000 ab). Response in these metabolic parameters to chronic food restriction differs in several respects. However, increased plasma cholesterol characterizes both models. In the experiment, cholesterol levels in plasma of the skip-a-day group were significantly increased in comparison with all other groups. There were no significant differences between feeding treatments in plasma glucose, total protein or triacylglyceroles levels found in present experiment. Dewil et al. (1999) described decrease in plasma glucose induced by the short food restriction (1 day) in chickens. However, glucose returned to normal levels, i.e. similar to those recorded in ad libitum fed hens, after a 7 day restriction. This was interpreted in terms of the effectiveness of the glucose homeostatic mechanisms (Dewil et al. 1999). In summary, there were the signs of reduced welfare detected in pullets fed according to the skip-aday feed restriction method. It was associated with increase in blood indices of stress such as increased plasma cholesterol and hetrophil to lymphocyte ratio so be taken as indicator of reduced welfare. References BARTOV, I., BORNSTEIN, S., LEV, Y., PINES, M., and ROSENBURG, J. (1988) Feed restriction in broiler breeder pullets, skip-a-day versus skip-two-day. Pout. Sci. 67: 809-813. BENNETT, C.D., and LESSON, S. (1989) Growth of broiler breeder pullets with skip-a-day versus daily feeding. Pout. Sci. 68: 836-838. DAVISON, T.F., REA, J., and ROWELL, J.G. (1983) Effects of dietary corticosterone on the growth and metabolism of immature Gallus domesticus. Gen. Comp. Endocrinol. 50:463-468. DEWIL, E., DARRAS V.M., SPENCER G.S.G., LAUTERIO T.J., DECUYPERE, and E. (1999) The regulation of GH dependent hormones and enzymes after feed restriction in dwarf and control chickens. Life Sci. 64: 1359-1371 FAWC, (1998) Report on the welfare of broiler breeders. Farm Animals Welfare Council (FAWC), Sorption, Surrey, U.K. FATTORI, T. R., H. R. WILSON, R. H. HARMS, and MILESS, R. D. (1991) Response of broiler breeder females to feed restriction below recommended levels. 1. Growth and reproductive performance. Poultry Sci. 70:26 36. HOCKING, P.M., GILBERT, A. B., WALKER, M.,and WADDINGTON, D.(1987) Ovarian follicular structure of White Leghorns fed ad libitum and dwarf and normal broiler breeders fed ad libitum or restricted until point of lay. Br. poult. Sci. 28:493-506. HOCKING, P.M., WADDINGTON, D., WALKER, M.A., and GILBERT, A. (1989) Control of the development of the ovarian follicular hierarchy in broiler breeder pullets by food restriction during rearing. Br. Pout. Sci.30:161-174. HOCKING, P. M., (1993) Effects of body weight at sexual maturity and the degree and age of restriction during rearing on the ovarian follicular hierarchy of broiler breeder females. Br.Poult. Sci. 34:793 801 HOCKING,P.M., MAXWELL, M.H. and MITCHELL, M.A.(1996) Relationships between the degree of food restriction and welfare indices in broiler breeder females. Br. Poult. Sci. 37 :263-278. KATANBAF, M. N., E. A. DUNNINGTON, and SIEGEL, P. B. (1989) Restricted feeding in early and late-feathering chickens. 2. Reproductive responses. Poultry Sci. 68:352 358. KUBIKOVA.l,VYBOH,P.,and KOSTAl, L. (2001) Behavioural,endocrine and metabolic effects of food restriction in broiler breeder hens.acta vet.brno. 70:247-257.

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