Factors affecting body weight and growth rate of Awassi lambs

J. agric. Set., Camb. (1981), 97, 449-452 Printed in Great Britain 449 Factors affecting body weight and growth rate of Awassi lambs BY P. N. BHAT, G. L. KOUL*, S. K. KOULf, R. KUMARJ AND R. C. GARG Indian Veterinary Research Institute, Izatnagar 243 122, Uttar Pradesh, India {Revised MS. received 7 April 1981) SUMMARY An experiment was carried out to study the effect of early weaning on body weight and growth rate of Awassi lambs raised at Abu-Ghurib Experiment Station, Baghdad, Iraq. Sex, type of birth and weaning age significantly influenced the body weight and growth rate of lambs at all the ages studied. Dam's age and weight at lambing, however, did not affect the growth rate of the lambs. The average body weights of lambs at 4 and 6 months of age were 23-8±0-28 and 32-3+ 0-36 kg. The average daily gain in weight up to 120 and 180 days of age was 162-3 ±2-57 and 153-7 ±1-94 g/day respectively. Males were heavier than females and singles were heavier than twins at all the ages. Lambs weaned at 60 days of age were heavier and had a faster growth rate than those weaned at 90 or 120 days of age. Males born to 2-year-old dams grew fastest while the females born to them had the lowest body weights and growth rate. INTRODUCTION Pre-weaning growth has an important bearing on the market weight of lambs. Fast growth in early stages of life minimizes the cost of lamb production. Lawlor, Louca & Mavrogenis (1974) indicated that weaning Awassi lambs at 35 days of age showed a rapid growth rate and did not affect the lactation performance of ewes. Bhat et al. (1978) reported that Awassi lambs weaned at 60 days of age were heavier at 120 and 195 days than the lambs weaned at 90 and 120 days of age. In this report two body weights at 4 and 6 months and two average daily gains in weight (ADG) up to 120 and 180 days of age are considered. The effects due to age of weaning, age and weight of dam at lambing, type of birth, sex of the lamb and certain interactions between them were studied. MATERIALS AND METHODS Animals This experiment was conducted on 360 lambs born during the first 15 days of October 1974 at the Sheep Division of the Abu-Ghurib Experiment * Present address: Indian Veterinary Research Institute, Mukteswar, Uttar Pradesh, India. t Present address: Raj as than Dairy Corporation, Jaipur, Raj as than, India. % Present address: Indian Council of Agricultural Research, North-East Hill Complex, Ghas-Pani, Dimapur, Nagaland, India. Station, Iraq. They were weaned at three ages, 60, 90 and 120 days, and were raised in confinement till the 4th month. The animals were fed on medium quality hay (lucerne or a mixture of lucerne and berseem) and were given a creep ration from the 15th day onward. After 15 days the lambs were separated from their ewes initially for 2 h/day, which was increased till they were completely weaned. After the 4th month all the lambs were allowed to graze for 5 h/day on pastures of lucerne and berseem. Concentrates were offered ad, libitum. Statistical analysis A least-squares analysis of variance procedure as outlined by Harvey (1966) was used to examine the effects of sex, type of birth, dam's age and weight at lambing and weaning age of the lamb on body weight of lambs at 4th and 6th month of age, and on average daily gain in weight up to the age of 120 and 180 days. The following model was assumed: Yimmn = ft +Si + TBl + DAk + DWl+Wn+S.TBtt +S.DA(k+S.DWu+S.Wim+TB.DWil + TB.Wlm + eiiklmn, where ft is the overall mean; S( is the effect of ith sex, i = 1,2; TBt is the effect of jth type of birth, j = 1,2; DAk is the effect of kth dam's age, k = 1, 2, ..., 8; DWt is the effect of Ith dam's weight, I = 1, 2, 3; JJ'ra is the effect of rnth weaning age, m = 1, 2, 3; S.TBit, S.DAik, S.DWH and S.W(m 450 P. N. BHAT AND OTHERS are the interactions of ith sex with jth type of birth, kth dam's age, Ith dam's weight and with weaning age; TB.DWn and TB.Wim are the interactions of jth type of birth with Ith dam's weight and jnth weaning age; and etjtlmn is the random error with usual assumptions. Other interactions were not considered important. The differences among all possible pairs of leastsquares means of each significant main effect were tested by modified Duncan's multiple range test (Kramer, 1957). RESULTS AND DISCUSSION The mean squares from the analyses of variance for body weight and average daily gain traits are shown in Table 1. The least-squares means with their standard errors for significant main effects and Duncan's multiple range tests are given in Table 2. Males were heavier than females at all ages and gained more per day than the females. Significantly heavier body weights in males than females were also reported by Bhat et al. (1978) and Bhat, Abid & Koul (1979) in Awassi lambs, while Eliya & Juma (1970) did not obtain significant differences due to sex in this breed. Lambs born as singles were consistently heavier than those born as twins at all the ages. The differences in ADG due to the type of birth were significant at both the ages. Washlstrom, McCarty & Ghoneim (1963) and Bhat et al. (1978) also reported significant differences in body weight of single and twin-born lambs. Lambs born to 5-year-old ewes had the highest body weight at 4 and 6 months. Dam's weight at lambing had no significant effect on the body weight Source or growth rate of lambs. It appears that growth is completed in this breed much before the age of 2 years, hence no effect could be observed. Additionally the lambs were introduced to creep feed at an early age, which might have contributed in further diluting the influence of dam's age and weight on the body weight and growth rate of their lambs. It was observed that males born to young dams (2 years of age) were consistently heavier at 4 and 6 months of age and had a faster rate of growth up to 120 and 180 days than the males born to dams of other age groups. Such a trend, however, was not observed in the case of females born to ewes of different age groups. The females born to 2-year-old dams had the lowest body weights and growth rate. However, no such trend was observed in respect of dam's weight at lambing. The reasons for such a result are not obvious. Though sex x type of birth interaction was not significant, single-born males were slightly heavier than twin-born males, and males were heavier than females. The single-born males were heavier at 6 months than twin-born males, single and twinborn females respectively. It was observed that single-born lambs weaned at 60 days achieved the highest body weight at 4 and 6 months of age and a higher growth rate from birth to 120 as well as 180 days than single-born lambs weaned at 90 and 120 days and also than twin-born lambs weaned at all the three ages. Weaning age of lambs significantly influenced their body weights and growth rate subsequent to weaning. Of the three groups weaned at 60, 90 and 120 days, the body weight of lambs weaned at 60 days of age was consistently heavier than that of the other two groups. Lambs at 6 months weaned Table 1. Mean squares from variance analyses for body weights and average daily gains in Awassi lambs 0-6th month 0-4th month (ADG 1) (ADG 2) 6th month 4th month D.F. Sex Type of birth Dam's age group Weaning age group Dam's weight group Sex x type of birth Sex x dam's age group Sex x dam's weight group Sex x weaning age group Type of birth x dam's weight group Type of birth x weaning age group Residual * P < 005; 1 1 7 2 2 1 7 2 2 2 2 224-44** 15606** 9-94 58-58** 14-78 14-33 7-72 618 12-77 7-67 19-80 9-34 (295) 748-30** 214-47** 17-52 156-26** 8-33 10-44 26-70* 1-86 3015 0-99 45-72* 11-33 (273) 7040-97** 2602-44* 501-93 4123-26** 892-35 39004 682-54 229-52 712-20 664-07 20107-58** 2058-60** 462-70* 4561-22** 322-49 16014 787-45* 27-59 796-93 125-37 1753-18 1603-56** 585-65 (273) 333-82 (273) P < 0 0 1 . Figures in parentheses denote error degrees of freedom. Growth rate of Awassi lambs 451 Table 2. Least-squares means with their standard errors for significant main effects affecting body weights and average daily gains in Awassi lambs 6th month 4th month Subclass Overall (/*) Sex Male (1) Female (2) Type of birth Single (1) Twin (2) Weaning age groups (days) 1 (60) 2 (90) 3 (120) 0—4th month (ADG1) 0-6th month (ADG 2) Mean 23-8 S.E. No. 0-28 303 Mean 32-3 0-36 Mean 162-3 2-57 Mean 153-7 S.E. 325 163 162 25-2a 22-4b 0-37 0-41 151 152 35-2a 29-3b 0-43 0-57 171-3a 153-3b 310 414 168-9a 138-5b 2-34 312 164 161 24-7a 22-9b 0-33 0-36 150 153 33-3a 31-2b 0-41 0-45 1660a 158-6b 2-98 3-24 1570a 150-4b 2-25 2-45 109 105 111 24-3a 22-9b 24-2a 0-36 0-39 0-37 101 105 97 33-2a 32-8a 30-8b 0-44 0-46 0-46 168-6a 155-4b 1629a 3-20 3-32 3-35 158-8a 156-6a 145-6b 2-42 2-51 2-53 No. S.E. S.E. 1-94 Least-squares means having same letter within a subclass are not significantly different from each other (P > 005). The results obtained in the present study, thereat 60 days were heavier and gained weight faster than the lambs weaned at 120 days. Ghoneim et al. fore, indicate that the Awassi lambs can be weaned (1973) reported a growth rate of 134g/day up to at 60 days and induced to feed for higher liveweaning and 97 g/day up to yearling stage. Juma weight gains for mutton production. The ewes can et al. (1969) reported these figures to be 166 and be rebred to produce at least three lamb crops in 105 g respectively. In the present study the average 2 years as an added advantage for mutton, milk daily gain in weight up to 120 and 180 days of age and wool production. was 162-3 ±2-57 and 153-7 ± 1-94 g/day. The first author is grateful to Mr Noori Al-Rawi, Wardrop & Coombe (1961) suggested that lambs were capable of existing on solid food after 3 weeks Director-General of Animal Resources, Government of age, whereas Bonelli (1961) observed no differ- of Iraq for the facilities provided to conduct this ences in growth rate of lambs weaned normally and experiment when he was adviser in Animal Prolambs weaned between 17 and 30 days of age. The duction to the Government of Iraq. He is also present findings indicate that weaning at 60 days of thankful to E. F. Badwey for assisting in collection age was most profitable and the lambs convert feed of the data and to other members of the staff of more efficiently into body-weight gain around this Sheep Division, Animal Husbandry Station, Abuage. Bhat et al. (1978) suggested 60 days weaning in Ghurib, Baghdad, for their assistance. Awassi lambs and early creep feeding to be of significant importance in early development of the rumen in lambs. 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