Effect of feeding Atriplex browse to lactating ewes on milk yield and growth rate of their lambs

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1 Small Ruminant Research 64 (2006) Effect of feeding Atriplex browse to lactating ewes on milk yield and growth rate of their lambs M.M.W. Abu-Zanat, M.J. Tabbaa Department of Animal Production, Faculty of Agriculture, The University of Jordan, Amman 11942, Jordan Received 14 January 2004; received in revised form 7 March 2005; accepted 12 April 2005 Available online 17 May 2005 Abstract The study was conducted to determine the effect of feeding a diet containing saltbush (Atriplex) on the milk yield of Awassi ewes and BW gain of their lambs. Fifty-four adult Awassi ewes (4 ± 1-year-old, 58.1 ± 2 kg BW, with parities ranging from 1 to 3) in late gestation were randomly selected and distributed into nine equal groups, six animals each. The selected ewes were fed with the dietary treatments for 3 weeks before the projected lambing date and continued until the end of the study, which lasted for 143 days. Three dietary treatments were assigned to the nine groups; each treatment was applied to three groups (pens) of ewes, and each pen contained six ewes fed as a group in the same pen. Each group received a concentrate ration (4.5 kg) and was supplemented with either tibin (shredded barley straws) (6.0 kg); or tibin (3.0 kg) and dried Atriplex browse (3.0 kg); or dried Atriplex browse (6.0 kg). The dietary treatments had a significant (P < 0.01) effect on the overall DMI of ewes. The ewes receiving diets containing the saltbush increased feed intake significantly compared with intake levels of control animals fed with concentrate ration and tibin. The treatments had a significant (P < 0.01) effect on DMI of ewes during the different physiological stages: late gestation, suckling and after weaning. The ewes BW averaged 58.4 kg at lambing, declined to 53.2 kg at weaning and then increased to 56.9 kg at the end of the experiment. The dietary treatments had no significant effect either on the final BW or on the overall BW changes of ewes (the difference between initial and final BW). The control animals showed a positive change in BW (1.5 kg per ewe) whereas the ewes receiving the diets containing saltbush at 50 and 100% lost 0.7 and 4.5 kg in BW, respectively. There was no significant effect of the proportion of saltbush foliage in diet on milk production. Means of daily milk production were 0.27, 0.33 and 0.35 kg per ewe for the diets containing 0, 50 and 100% saltbush, respectively. Milk production of ewes lambing single was higher (0.37 kg per ewe) than the ewes lambing twins (0.27 kg per ewe). The treatments had no significant effect on birth weight, weaning weight and growth rate of lambs. Feeding Atriplex browse with concentrate ration to lactating Awassi ewes did not present any significant problems on milk yield or growth rate of lambs; the most important sources of income for stockmen. Substituting saltbush browse for tibin in diets of sheep will reduce the cost of roughage component by US$ per head per day Elsevier B.V. All rights reserved. Keywords: Milk yield; Saltbushes; Awassi sheep; Shredded barley straw; Growth rate Corresponding author. Tel.: x3011/2577; fax: ; mobile: address: Mahfouz@ju.edu.jo (M.M.W. Abu-Zanat) /$ see front matter 2005 Elsevier B.V. All rights reserved. doi: /j.smallrumres

2 M.M.W. Abu-Zanat, M.J. Tabbaa / Small Ruminant Research 64 (2006) Introduction In Jordan and most West Asia and North Africa (WANA) countries, rangelands occupy large portions of the total surface area. Overstocking had resulted in severe degradation of these lands by about 1975 (Abu-Zanat et al., 2004; Abu-Zanat, 2005; Le Houerou, 1990). These lands are being revegetated, and the main fodder shrubs commonly used for revegetating the degraded rangelands to extend grazing season by small ruminants are Mediterranean saltbush (Atriplex halimus L.), oldman saltbush (Atriplex nummularia L.) and fourwing saltbush (Atriplex canescens L.). According to Le Houerou (1986, 1994), vast areas in the WANA region have been revegetated with saltbushes and represented a significant forage resource for feeding of small ruminants (Clarke, 1982). Fodder shrubs are generally planted to provide feed during the long dry and hot period from June to October during the summer season in the arid and semi-arid areas of the WANA region and Mediterranean Basin (Morcombe et al., 1996; Otal et al., 1991). Sheep and goat flocks graze the established plantations of saltbushes after exploiting most of the companion herbaceous vegetation. During this period, ewes are mated and the browse of fodder shrubs seems able to meet the nutrient requirements of animals for maintenance and often well above (Correal et al., 1990). The severe degradation of native rangelands in Jordan had obliged stockowners to graze their animals, especially during lactation in early spring, in the different range reserves planted with Atriplex plants. During this period, saltbushes are the main forage resource for feeding small ruminants. There are claims that feeding saltbushes to small ruminants has drastic effects on milk production and composition. In Syria, saltbush grazing by sheep affected the quality of fresh milk, with reductions in dry matter and fat (Goodchild et al., 1997). Increasing dietary saltbush (Atriplex amnicola) level led to a significant decrease in milk production of Beetal goats in Pakistan (Raza et al., 2000). Since Atriplex species are commonly used for revegetation of degraded rangelands in the WANA countries, it is important to understand the impact of Atriplex browse on animal production, especially milk yield and body gain of offspring, which are the major sources of income for the pastoral communities. Therefore, the objective of this study was to assess the inclusion of Atriplex browse in the diet of Awassi ewes on milk yield and growth rate of their lambs. 2. Materials and methods 2.1. Animals The study was conducted at Jordan University Station for Agricultural Research (JUSAR) located in the Jordan Valley at 300 m below sea level, 45 km west of Amman. Based on the station records, 54 progesterone synchronized Awassi ewes of 4 ± 1-year-old, weighing kg, during the late gestation period were randomly selected and distributed into nine equal groups, 6 animals each. The ewes had given birth at least once before the experiment. The ewes parity ranged between one and three and was equally represented in the different groups (pens) of ewes. The selected ewes were left to accommodate to the pens for 2 weeks receiving the station s diet (concentrate ration, tibin which is the shredded barley straw, and alfalfa hay) and had access to water free choice. Ewes were fed the treatment diets during last three weeks prior to the projected lambing date to investigate their effects on lambs birth weights. Feeding the dietary treatments lasted for 143 days Dietary treatments The browse (leaves and small twigs) of A. halimus and A. nummularia was brought from Khalideyah nursery at Mafraq Governorate. The routine management of the nursery involves trimming of saltbush seedlings 1 2 months prior to transplant distribution. It was possible to collect large quantities of saltbush trimmings (mainly leaves and small twigs), which were transported to the JUSAR in the Jordan Valley. The browse was dried in the shade and then chopped mechanically similar to tibin before feeding to alleviate selectivity for leaves by animals. On average, twigs up to 5 mm in diameter were included in the diet. Percentage composition of the concentrate ration is presented in Table 1. Chemical composition of concentrate, tibin and saltbush browse is presented in Table 2. Three dietary treatments were assigned to the nine groups; each treatment was applied to three pens (repli-

3 154 M.M.W. Abu-Zanat, M.J. Tabbaa / Small Ruminant Research 64 (2006) Table 1 Ingredient composition of the concentrate part of the ration Ingredient Percentage Barley grains 78.0 Wheat bran 12.5 Soybean meal (44% CP) 7.0 Di-calcium phosphate 1.0 Limestone 0.5 Salt (NaCl) 0.9 Vitamins and minerals a 0.1 Total a One gram contains: 7.7 MIU Vitamin A, 1.9 MIU Vitamin D3, 4 mg Vitamin E, 200 g magnesium sulfate, 6.4 mg iron sulfate, 1.03 mg cobalt carbonate, mg zinc sulfate, 4.84 mg manganese oxide, 0.79 mg potassium iodide, 0.23 mg sodium silinate and 12 mg copper sulfate in addition to anti-oxidant. cates), and each pen consisted of six ewes. The ewes were fed as group in the same pen. The groups of ewes were fed tibin (6.0 kg), tibin (3.0 kg), dried Atriplex browse (3.0 kg), dried Atriplex browse (6.0 kg), and 4.5 kg of concentrate ration was offered to all treatment groups Sampling Daily feed intake of concentrate, tibin and saltbush foliage (the difference between offered feeds and refusals) for each group was recorded throughout the study. Body weights of ewes were recorded one day before starting the experiment (initial BW), after lambing and then biweekly throughout the study. The newborn lambs were weighed at birth and then biweekly until weaning. Milk production was recorded weekly after weaning lambs at 60 days of age. Table 2 Chemical composition of concentrate, tibin (shredded barley straw) and saltbush browse Concentrate Tibin Atriplex DM (g/kg) CP (g/kg DM) NDF (g/kg DM) ADF (g/kg DM) Ash (g/kg DM) ME (kcal/kg DM) 2.89 a 1.74 b 2.21 c a Calculated for the concentrate. b NRC (1985). c Kearl et al. (1979) Statistical analysis The least square analysis of variance was performed on the data using the SAS general linear model (GLM) procedure for a complete randomized design (SAS, 1994). For DMI and ewes BW changes, a split-plot model was used and included the treatment, production stage (gestation, suckling, after weaning), and their interaction: Y = treat + rep(treat) + stage + treat stage. Milk production model included treatment, litter size (single or twin) and their interaction and the model was adjusted for the day of lambing: milk yield = treat + litter + litter treat + day of lambing. Lamb weights and growth rate model included treatment, lamb sex (male or female), litter size (single or twin) and their two-way interactions and the model was adjusted for the day of lambing (birth date): Y = treat + sex + litter + sex treat + sex litter + litter treat + day of lambing. Weaning weight was adjusted for 60 days of age using regression analysis procedure of SAS (SAS, 1994). Initial analysis showed no differences due to parity. This is obvious since all ewes introduced to the study were multiparous. 3. Results 3.1. Feed intake Mean values of daily DMI of ewes during late gestation, suckling and after weaning are presented in Table 3. The dietary treatments had a significant (P < 0.01) effect on overall DMI of ewes. The DMI averaged 1.38, 1.45 and 1.51 kg DM per ewe per day for diets containing tibin, tibin and saltbush, and saltbush, respectively. The ewes receiving diets containing saltbush increased their DMI significantly as compared to control animals. Dry matter intakes of ewes fed the diets containing saltbush foliage were not significantly different. The treatments had a significant (P < 0.01) effect on DMI of ewes during the different physiological stages: late gestation, suckling and after weaning. Dry matter intakes of ewes fed the saltbush diets were higher than those of control animals during late gestation and averaged 1.46 kg DM per ewe per day for animals on 50 and 100% saltbush as compared with 1.40 kg DM

4 M.M.W. Abu-Zanat, M.J. Tabbaa / Small Ruminant Research 64 (2006) Table 3 Least square means ± S.E. of DMI, BW, BW changes and daily milk production of Awassi ewes fed diets consisting of concentrate and different ratios of tibin (shredded barley straw) and Atriplex browse at the Jordan University Station for Agricultural Research Dietary treatments Concentrate + tibin Concentrate + tibin + Atriplex Concentrate + Atriplex DMI (kg per ewe per day) Overall 1.38 ± 0.02 b 1.45 ± 0.02 a 1.51 ± 0.02 a Late gestation 1.40 ± b 1.46 ± a 1.46 ± a Suckling 1.37± c 1.43 ± b 1.53 ± a After weaning 1.38 ± b 1.47 ± a 1.54 ± a DMI (g per kg BW 0.75 ) 63c 68b 70a Ewes BW (kg) Initial 57.5 ± ± ± 1.1 At lambing 59.0 ± ± ± 1.3 At weaning 53.8 ± ± ± 1.7 Final 58.9 ± ± ± 2.1 Ewes BW changes (kg) Overall 1.5 ± ± ± 1.8 Before lambing 0.5 ± ± ± 0.9 Lambing to weaning 3.8 ± ± ± 1.6 After weaning 4.0 ± ± ± 1.0 Daily milk production (kg per ewe) All ewes 0.27 ± ± ± 0.06 Ewes lambing single 0.32 ± ± ± 0.06 Ewes lambing twin 0.23 ± ± ± 0.10 Means in the same line with different letters are different (P < 0.05). per ewe per day of the control group. During suckling, the DMI of ewes receiving the diet containing saltbush were higher than intake levels of control animals. Dry matter intakes averaged 1.37, 1.43 and 1.53 kg DM per ewe per day for diets containing 0, 50 and 100% saltbush, respectively. Dry matter intakes of suckling ewes fed diet containing 100% saltbush were higher than feed intakes of ewes on 50% saltbush diet. After weaning, the DMI of ewes fed diets containing saltbush were higher than feed intakes of the control animals. During this period, means of DMI were 1.38, 1.47 and 1.54 kg DM per ewe per day for diets containing tibin, tibin saltbush and saltbush, respectively. There was no significant difference in DMI after weaning between the ewes groups fed diets containing 50 and 100% saltbush. Dry matter intakes per kg BW 0.75 averaged 63, 68 and 70 g for diets containing 0, 50 and 100% saltbush, respectively. Replacing tibin by saltbush increased DMI from 63 to 70 g per kg BW Dry matter intakes of roughages (tibin, saltbush or both) averaged 0.63, 0.70 and 0.76 kg DM per ewe per day for 0, 50 and 100% saltbush diets, respectively. There was a gradual increase in DMI of ewes fed the 100% saltbush diet throughout the experiment. Percentages of roughages to total DMI varied from 44.1 to Dry matter intakes relative to ewe BW averaged 2.5% and the suggested levels of DMI for ewes weighing kg are between 3.0 and 3.4% in the last 4 weeks of gestation and between 3.8 and 4.2% in the first 6 8 weeks of lactation (NRC, 1985), which are well above the reported levels in our study Ewe live weight The treatments had no significant effect on the final BW of ewes, which averaged 58.9, 57.7 and 53.9 kg for animals receiving diets containing 0, 50 and 100% saltbush, respectively. The overall means of ewes BW were 58.1 kg at the beginning of the experiment, 58.4 kg at lambing, which declined to 53.2 kg at weaning, then increased to 56.9 kg at the end of the experiment. The ewes showed the lowest BW during the suckling period.

5 156 M.M.W. Abu-Zanat, M.J. Tabbaa / Small Ruminant Research 64 (2006) The overall BW changes (difference between initial and final BW) of ewes were not significantly different at P < 0.05, but were different at P = The control ewes gained 1.5 kg per head, whereas the ewes receiving diets containing 50 and 100% saltbushes lost 0.7 and 4.5 kg per head, respectively. The BW changes of ewes were not significantly different before lambing and after weaning. The BW changes of suckling ewes were significantly different at P = Live weight changes of pregnant ewes ranged between 0.5 and 0.9 kg per head. The animals fed diets containing 100% saltbush showed some gain in body weight whereas the animals receiving 0 and 50% saltbush in the diet lost some weight. All ewes exhibited some loss in BW during suckling that ranged from 7.2 to 3.1 kg per head. After weaning, all ewes showed some gain in body weight, which averaged 4.0, 3.1 and 3.2 kg per head for diets containing 0, 50 and 100% saltbush, respectively Milk production The values of milk production given in Table 3 are means of milk yield after weaning lambs at 60 days of age. Statistical analysis of data indicated a nonsignificant effect of the proportion of saltbush foliage in diet on milk production. The overall daily milk production averaged 0.27, 0.33 and 0.35 kg per ewe for diets containing 0, 50 and 100% saltbush, respectively. Daily milk production of ewes lambing single and twins averaged 0.32, 0.40 and 0.39 and 0.23, 0.26 and 0.31 kg per ewe for the control, 50 and 100% saltbush diets, respectively. The computed milk production during the first 60 days of lactation was 62, 64 and 61 kg per ewe compared to 25, 30 and 32 kg per ewe after weaning for sheep receiving diets containing 0, 50 and 100% saltbush, respectively. Total milk yield (the amount of suckled milk and milk produced after weaning) averaged 86, 94 and 93 kg per ewe for the control, 50 and 100% saltbush diets, respectively Lamb weight Table 4 shows birth and weaning weights and growth rate of lambs. Dietary treatments had no significant effect on mean birth weight of lambs. There were significant (P < 0.05) differences in mean birth weight between male (5.17 kg) and female (4.12 kg) lambs and Table 4 Least square means ± S.E. of the birth weight, weaning weight and daily live weight changes of lambs born to Awassi ewes fed diets containing different ratios of tibin (shredded barley straw) and Atriplex browse at the University of Jordan Station for Agricultural Research in the Jordan Valley Dietary treatments Concentrate + tibin Concentrate + tibin + Atriplex Concentrate + Atriplex Lamb birth weight (kg) All 4.52 ± ± ± 0.18 Males 5.24 ± ± ± 0.25 Females 3.79 ± ± ± 0.23 Single 4.54 ± ± ± 0.19 Twin 4.49 ± ± ± 0.30 Lamb weaning weight (kg) All ± ± ± 0.91 Males ± ± ± 1.46 Females ± ± ± 1.06 Single ± ± ± 0.92 Twin ± ± ± 1.59 Lamb daily live weight changes (kg per day) All ± ± ± Males ± ± ± Females ± ± ± Single ± ± ± Twin ± ± ± Means in the same line with different letters are different (P < 0.05).

6 M.M.W. Abu-Zanat, M.J. Tabbaa / Small Ruminant Research 64 (2006) between singles (4.99 kg) and twins (4.30 kg). Overall birth weight of lambs averaged 4.64 kg. The actual weaning weights of lambs were adjusted because of slight differences in lambing time among the synchronized ewes. There were no significant differences in weaning weights of lambs among dietary treatments. However, twinning had a significant effect on weaning weight of lambs. Means of weaning weights were and kg for lambs born single and twin, respectively. Weaning weights of males (17.88 kg) and females (16.21 kg) were not significantly different. The treatments had no significant effect on growth rate of lambs. Daily gains of lambs averaged 0.203, and kg per day for diets containing 0, 50 and 100% saltbush, respectively. Male and female lambs exhibited similar daily gains, and kg, respectively. Daily gains of twin lambs were 0.148, and kg compared to 0.258, and kg for single lambs for diets containing tibin, tibin saltbush, and saltbush, respectively. 4. Discussion 4.1. Dry matter intake The lower levels of DMI by ewes fed concentrate and tibin diet than those fed diets containing concentrate and saltbush could be attributed either to low digestibility of tibin (Bird, 1974) or to protein deficiency (Warren et al., 1990). Cereal straws are known for their low nutritive value and may restrict the DMI. This was demonstrated by Hadjipanayiotou (1988), who reported that feeding concentrate and barley straw to lactating Chios and Awassi ewes resulted in low intake of straw. However, intake of straw increased with gradual increase in concentrate feeding up to a level of 25% of total DM and then declined substantially after reaching this level. Intake of roughages by ruminants is positively correlated with digestibility; DMI of poorly digestible feeds is less than the intake of highly digestible ones (Galyean and Defoor, 2003). It seemed that the low digestibility of tibin limited feed intake of ewes that were fed the concentrate and tibin diet. The decrease in energy and protein intake because of the low quality feed imposes restrictions on microbial growth in the rumen, which have specific nutrient requirements for their growth (Hoaglund et al., 1992). The low N content of tibin (52 g/kg DM) may be depressing microbial activity in the rumen. The levels of DMI (63 70 g/kg BW 0.75 ) were close to DMI (70 73 g/kg BW 0.75 ) of Barbarine wethers fed diets based on cactus (Opuntia ficus indica var. inermis) and A. nummularia (80% of the diet) with restricted amounts of wheat straw (180 g per day) (Nefzaoui, 2000). In a recent study, Ben Salem et al. (2004) used spineless cactus and oldman saltbush as alternative supplements for growing Barbarine lambs given straw-based diets that resulted in DMI between 72 and 123 g/kg metabolic weight. Dry matter intake was higher in sheep given alternative supplements (barley grains Atriplex browse, cactus Atriplex browse) as compared to those receiving common concentrate feeds. However, the values of DMI in our study were lower than the intake levels reported by other researchers (Correal and Sotomayor, 1997; Sotomayor and Correal, 2000). In these two studies, Oldman saltbush browse with or without barley straw was fed to dry Seurena ewes under pen feeding conditions; DMI of ewes receiving the browse and straw mixed diet was higher (102 g/kg BW 0.75 ) than that of the ewes fed solely saltbush diet (88 g/kg BW 0.75 ). The inclusion of saltbush browse in straw-based diets has a positive influence on DMI (Rehman et al., 1994). Differences in DMI between the different studies are expected to be due to variability in plant species, phenological stage, leafiness, type of supplements, feeding strategy (pen feeding or direct grazing), and animal condition (Allison, 1985; Le Houerou, 1991). Previous experience and adaptation of animals to saltbushes considerably affect the intake of browse (Correal and Sotomayor, 1997) Ewes body weight changes Since the DMI of ewes fed diets containing the saltbush were higher than DMI of the control animals, and the nutritive value of Atriplex browse is much better than the nutritive value of tibin, it was surprising that the dietary treatments had no significant effect on final BW, BW changes and milk production of ewes. Daily intakes of CP and ME of ewes were computed for the different physiological stages to explain the above results (Table 5). According to NRC (1985), the recommended daily CP intakes of ewes during the last 4 weeks gestation,

7 158 M.M.W. Abu-Zanat, M.J. Tabbaa / Small Ruminant Research 64 (2006) Table 5 Computed daily intakes of CP (g) and ME (Mcal) by Awassi sheep fed diets containing different proportions of shredded barley straw (tibin) and Atriplex browse during late gestation (LG), suckling (S) and after weaning (AW) Nutrients Concentrate + tibin Concentrate + tibin + Atriplex Concentrate + Atriplex LG S AW LG S AW LG S AW CP (g) ME (Mcal per ewe per day) According to NRC (1985) the daily CP requirements are 182, 309 and 182 g, and daily ME requirements are 3.05, 5.05 and 3.05 Mcal per ewe during late gestation (BW 58 kg), suckling (BW 53 kg) and after weaning (BW 58 kg), respectively. last 4 6 weeks lactation and suckling are 182, 182 and 309 g per head, respectively. The computed CP intakes during late gestation were 137, 167 and 200 g for ewes fed diets containing 0, 50 and 100% saltbush, respectively, which are well below the recommended CP levels (182 g), except for the diet containing the 100% saltbush (200 g). During suckling, the calculated CP intakes were 135, 166 and 209 g for ewes fed diets containing tibin, tibin and saltbush, and saltbush, respectively. The recommended CP intake during suckling is 309 g (NRC, 1985), which is well above the CP levels derived from the dietary treatments. The protein levels of diets containing 0 and 50% saltbush seemed to be inadequate to provide the ewes their CP requirements during late gestation and after weaning. The ewes fed diet containing 100% saltbush were able to obtain their CP requirements during late gestation and after weaning. None of the dietary treatments contained adequate amounts of crude protein to meet the daily requirements of ewes during suckling. The computed intakes and recommended requirements of daily ME exhibited a similar pattern of CP intakes. The calculated daily intakes of ME were 3.3, 3.55 and 3.74 Mcal during late gestation; 3.25, 3.50 and 3.89 Mcal during suckling; and 3.26, 3.59 and 3.91 Mcal per ewe after weaning for ewes fed diets containing 0, 50 and 100% saltbush, respectively. The recommended values of ME are 3.05 Mcal per ewe during late gestation and after weaning compared to 5.05 Mcal per ewe during suckling (NRC, 1985). Since the diet containing 100% saltbush was much better than the other two diets in terms of CP and ME, it was expected that the performance of ewes fed this type of diet should be higher than the performance of other animals fed diets containing 0 and 50% saltbush. The reported results of BW changes and milk production in this study could be attributed to the salt content or secondary chemical compounds present in the Atriplex browse. Leaves of saltbush, particularly Atriplex species, contain high amounts of salts (Malcolm et al., 1988). The seasonal contents of Na ranged between 5.59 and 6.66% in the dry matter of Atriplex foliage for spring and fall seasons, respectively (Abu-Zanat et al., 2003a). The reported intakes of Atriplex browse in this study, which ranged between 0.33 and 0.76 kg per animal per day, suggested that the daily salt consumption were around 20 and 47 g per sheep fed diets containing 50 and 100% saltbush, respectively (Abu-Zanat et al., 2003a). The high levels of salt in Atriplex browse forced animals to increase water intake with consequential influences on rumen physiology and metabolism (Konig, 1993). Saltbush species contain secondary chemical compounds, which may restrict grazing or feed intake by herbivores (Cheeke, 1995). Atriplex species accumulated 6.6% of oxalates and 5.2% DM of hydrolysable tannins (Abu-Zanat et al., 2003b). Plants containing 10% oxalate or more are considered toxic and should not be grazed. The tannins inhibit cellulolytic and protolytic enzymes and decrease the production of volatile fatty acids, microbial DNA and RNA in the rumen. It seems that the impact of tannins on rumen physiology of ewes fed diet containing 50% saltbush was less profound compared to those fed diet containing 100% saltbush. The inclusion of tibin in the diet of ewes plays an important role in diluting the impact of chemical secondary compounds present in the browse of Atriplex. In the literature, it is well documented that energy value of Atriplex spp is low, which ranges between 0.72 and 2.21 kcal/kg DM (Le Houerou, 1991; Kearl et al., 1979), and animals feeding solely on saltbush cannot maintain their BW. Correal and Sotomayor

8 M.M.W. Abu-Zanat, M.J. Tabbaa / Small Ruminant Research 64 (2006) (2000) showed that dry Seurena ewes maintained their BW, when fed saltbush browse with or without barley straw supplement. Sheep could maintain BW for quite long periods feeding saltbush, and these gains in body weight could be illusory because of increased water intake by the animals. The deuterium labelling technique showed that BW comparisons for animals feeding on saltbushes were a misleading indicator of sheep condition (Warren and Casson, 1994). Konig (1993) fed sheep and goats diets containing different proportions of Atriplex and showed that the differences in BW of animals were mainly due to an increase in total body water. The average water gain was 22.3 g per day, mean negative balance of total body solids was 28.9 g per day, and mean mobilized body fat was 29.1 g per day. In our study, the lack of significant differences in BW changes during all physiological stages suggests that the nutritive value of dietary treatments seems to be comparable Milk production The inclusion of saltbush foliage, in spite of their high-energy value and protein content compared to tibin, in the diets of lactating ewes did not result in significant differences in milk production of ewes. Lack of significant differences in milk yield between the ewes groups fed the dietary treatments could be attributed to the negative effects of secondary chemical compounds (oxalates and tannins) present in the browse of Atriplex. The estimated milk production for the first 60 days of lactation was slightly higher than of 53 kg reported by Titi and Lubbadeh (2003). However, these milk yields are below the genetic potential of the Awassi breed when kept under good management condition (El-Shakhret et al., 1996). Nutritional status of ewes in late gestation and lactation is a primary factor influencing total milk yield (Treacher, 1970). In early lactation, when the ewe s energy requirements and other nutrients are high, protein intake is important in affecting the partition of nutrients between milk production and BW loss Lambs body weight The ewes fed treatment diets produced lambs of similar birth weight. Information from various sources indicated that nutritional status of ewes in late pregnancy affects birth weight of lambs, which suggests that dietary treatments fed to ewes in our study were adequate to meet the requirement of nutrients during late pregnancy. Similar to previous studies, male lambs were heavier at birth than female lambs, and single lambs were heavier than twin lambs. Overall birth weight of lambs averaged 4.6 kg and was similar to values reported in previous studies (Louca et al., 1974; El-Shakhret et al., 1996; Titi and Lubbadeh, 2003). The lack of significant differences in weaning weights of lambs, except between single and twin lambs, indicates that the lambs were receiving adequate nutrition during suckling from all dietary treatments. Similar body gains were exhibited by lambs regardless of sex or litter size, which disagrees with the findings of Elyia and Juma (1970), who reported that single lambs grew faster (250 g per day) than twin lambs (185 g per day) based on the fact that more milk nutrients are consumed by single lambs compared to twin lambs. The lack of significant differences in birth and weaning weights, and growth rate of lambs suggests that the nutritive value of treatment diets was comparable Economic significance Based on the current prices of shredded barely straw (JD per kg DM, one JD is equivalent to US$ 1.43) and Atriplex browse (JD per kg DM) in Jordan, it is more economical for the farmer to replace the tibin partially with Atriplex browse (JAZPP, 2001). Replacing tibin by saltbush browse will reduce the cost of roughage component of sheep diets substantially. In Jordan, the average flock size of sheep and goats is around 250 heads (Abu-Zanat, 2002) and the average grazing season, similar to most countries of the WANA region, is around 3 months. In our study, the daily tibin intake of the control animals averaged 0.65 kg. Since the ewes fed diets containing 0 and 50% saltbush showed similar performance; substituting only 50% of tibin by Atriplex browse is more reasonable. The substitution of tibin by saltbush reduced the cost of roughage component in diets of sheep by JD per head per day (price differences between tibin and saltbush 0.65 kg 50% replacement). The saving in feeding roughages for the average flock size is around JD , which is equivalent to US$

9 160 M.M.W. Abu-Zanat, M.J. Tabbaa / Small Ruminant Research 64 (2006) Conclusions Although the nutritive value (CP and ME) of Atriplex browse is better than the tibin (shredded barley straw) it is possible to replace up to 50% of tibin by Atriplex browse in diets of lactating Awassi ewes without any significant problems on milk yield or growth rate of lambs, which are the two major sources of income for stockmen. From economical point of view, substituting tibin by Atriplex browse will reduce the cost of roughage component of sheep diets substantially. Acknowledgements Research was funded by the Government of Jordan and the European Commission as Project No: SEM/03/628/021 (Jordan Arid Zone Productivity Project: JAZPP). References Abu-Zanat, M.M.W., Results of feeding and grazing surveys in Ajloun and Muwaqqar areas in Jordan. Conservation and sustainable use of dryland agrobiodiversity in Jordan. 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