Growth rate and survival rate up to weaning in Nilagiri and Sandyno lambs

R Anilkumar, C Chandrahasan¹, M Iyue, M Selvaraju² and A Manickavasaka Dinakaran³

Sheep Breeding Research Station, Sandynallah – 643 237.
Tamilnadu Veterinary and Animal Sciences University,
The Nilgiris district, Tamilnadu, India.
ootyanil@yahoo.com
¹Veterinary College and Research Institute, Namakkal. 637001.
²Department of Animal Reproduction, Gynaecology and Obstetrics,
³Department of Veterinary Epidemiology and Preventive Medicine, Veterinary College and Research Institute, Namakkal. 637001.

Abstract

The growth records of Nilagiri (1965) and Sandyno (1915) breeds of sheep for the period from 1993-2002 available at the Sheep Breeding Research Station (SBRS), Sandynallah – 643 237, The Nilgiris District were utilized for the study. The effects of breed, season of birth, litter size and sex of the lambs on birth weight, weaning weight, average daily gain (ADG) and mortality were analyzed.

The lambs born during the second lambing season (SLS) (2.62 ± 0.06 and 11.9 ± 0.33 kg) were significantly (P<0.01) heavier at birth and weaning and the ADG (102.9 ± 3.24 g) was also significantly higher than lambs born during the main lambing season (MLS) (2.21 ± 0.05 and 9.02 ± 0.31 kg; 74.8 ± 3.24 g). Mortality was higher in lambs born during March (8.80%) than in those born during September (7.03%). Sex of the lamb had a highly significant influence on the birth weight, weaning weight and ADG. The males were heavier, weighing 2.46 ± 0.06 kg, 10.8 ± 0.32 kg and gaining 91.7 ± 3.32 g, than females (2.37 ± 0.06, 10.2 ± 0.32 kg and 86.1 ± 3.29 g). Single born lambs (3.07 ± 0.12 and 11.1 ± 0.06 kg) were heavier at birth and weaning than twins (2.25 ± 0.02 and 9.69 ± 0.12 kg) and triplets (1.93 ± 0.16 and 10.7 ± 0.19 kg). Sandyno lambs had a better birth weight, weaning weight and ADG (2.56 ± 0.06, 10.8 ± 0.32 kg and 90.3 ± 3.33 g) than Nilagiri lambs (2.27 ± 0.06, 10.2 ± 0.32 kg and 87.4 ± 3.28 g).  

Keywords: Birth and weaning weight, mortality, litter size

Introduction

Economic efficiency and viability of sheep management depends on the number of lambs born. The lambs born have to grow and survive up to marketing to maintain the economic efficiency. Birth weight is one of the main factors which determine the survivability and future growth of the young lambs (Mukasa-Mugerwa et al 2002). Birth weight of the lambs varied according to the genotype of the parents, sex, litter size and the environment (Rajendran 2005). The environment includes nutrition, breeding and lambing seasons and other uterine factors in the prenatal development. The growth of the lamb from birth to weaning is influenced mainly by the mothering ability of the dam. Similarly the genotype, nutrition, season and other environment factors also had an effect on the weaning weight (Panneerselvam 1993).

Studies on growth rate and survival in Nilagiri and Sandyno lambs are scarce and hence the present study was carried out to analyze factors affecting the birth weight, weaning weight, ADG and survivability in Nilagiri and Sandyno lambs.
 

Materials and methods

The growth records of Nilagiri (2788) and Sandyno (3534) breeds of sheep for the period from 1993-2002 available at Sheep Breeding Research Station (SBRS), Sandynallah – 643 237, The Nilgiris District of Tamilnadu State were utilized for the study. The ewes in this station were bred during two breeding seasons (Main breeding season [September-October] and Off breeding season [March-April]) and correspondingly the lambs were born during the main lambing season (MLS - February-March) and second lambing season (SLS - August-September). The effects of breed, season of birth, litter size and sex of the lambs on birth weight, weaning weight, ADG and mortality were analyzed. 

Management and feeding of the ewes

The ewes in this station are maintained under semi-intensive system of management, with 8 to 9 h of grazing. The ewes are provided with concentrates during the last month of pregnancy and during lactation.  Forty ewes and their lambs are maintained as batch till 45 days and the lambs are introduced to grazing gradually so that they will fully on grazing at 90 days of age when they are weaned. The lambs are provided with concentrates from day 10 with weekly increments of 25 g, till 150 g is reached.   The weaning weight of the lambs was adjusted for ± one week.

Least square procedure (Harvey 1990) was used to study the effects of non genetic factors on various traits. All possible interactions with set of fixed effects were fitted initially and insignificant interaction effects were omitted. The linear statistical model was used for analysis of the traits. The differences between the least square means for subclasses under a particular effect were tested by Duncan’s multiple range test modified by Kramer (1957). A chi square test was applied to the percentage of mortality in lambs. Study of effect of non genetic factors on mortality was done based on frequency of live and dead animals. 
 

Results and discussion

The mean (± SE) birth weight, weaning weight and average daily gain and the least-squares analysis of variance are presented in Tables 1 and 1a. 

Birth weight

Birth weight could be expected to be derived partly from the lamb’s genetic capacity for pre-natal growth and partly from the environmental effects especially season. In this investigation the lambs born during SLS (2.62 ± 0.06 kg) were significantly (P<0.01) heavier than lambs born during MLS (2.21 ± 0.05 kg). This was in agreement with the finding of Dixit et al (2001), Mandal et al (2003) and Rajendran (2005). Since the pregnant ewes had access to rich pasture during the south west monsoon, the birth weight of the lambs increased due to good body condition of the mother. Whereas, the lambs born during MLS were from mothers exposed to poor pasture during winter.

Sex of the lamb had a highly significant influence on the birth weight with the males (2.46 ± 0.06 kg) weighing heavier than females (2.37 ± 0.06 kg). The difference may be attributed to difference in metabolic rate during embryonic stage of life (Mishra 1981) and to difference in the endocrine profile of the two sexes (Singh and Dhillion 1992). This significant difference was confirmed by many authors (Iyue 1993; Dixit et al 2001; Mandal et al 2003 and Rajendran 2005).

Size of litter had a significant influence on the birth weight with single born lambs (3.07 ± 0.12 kg)  weighing heavier at birth than twins (2.25 ± 0.02 kg)  and triplets (1.93 ± 0.16 kg). This finding is in confirmation with Dixit et al (2001), Mandal et al (2003) and Rajendran (2005). The competition for intrauterine space and nutrition between the siblings might have contributed to the difference in birth weight between single and twins.

Sandyno lambs had a better birth weight (2.56 ± 0.06 kg) than Nilagiri lambs (2.27 ± 0.06 kg). Similar difference in birth weight among the Nilagiri and Sandyno lambs were observed by Sundararaman et al (1991) and Rajendran (2005). The birth weight observed for Nilagiri lambs in this study was less than the observations made by Sundararaman et al (1991) and Panneerselvam (1993). Similar observations were made in other breeds like Marwari and Nali (Sharma et al 2003) and Madras Red (Raman et al 2003).

Weaning weight

The mean weaning weight of the lambs born during SLS (11.9 ± 0.33 kg) was significantly (P<0.01) heavier than for lambs born during MLS (9.02 ± 0.31 kg). This finding was in agreement with Swain et al (2004) for Bharat Merino and Rajendran (2005) for Nilagiri and Sandyno lambs. The higher weaning weight of lambs born during SLS might be due to the carryover effect of birth weight, because they were heavier at birth. Similar seasonal effect on weaning weight was observed by Buvanendran et al (1992, Dixit et al (2001) and Rajendran (2005). However, Sridhar et al (1985) did not observe any significant effect of season of birth on weaning weight.

Single born lambs (11.1 ± 0.06 kg) were significantly (P<0.01) heavier than twins (9.69 ± 0.12 kg) and triplet (10.7 ± 0.19 kg). The difference noticed in weaning weight between single and twins might be mostly due to the nutritional inadequacies suffered by the twins sharing milk between the twins. The influence of litter size on weaning weight was also reported by Buvanendran et al (1992), Mandal et al (2003) and Rajendran (2005). The lambs born as single was about 14.8 per cent heavier at weaning than lambs born as twins, which was comparable to the reports of  Buvanendran et al (1992), Dixit et al (2001) and Rajendran (2005).

In the present study, the male lambs (10.8 ± 0.32 kg) weighed heavier at weaning than female (10.2 ± 0.32 kg) lambs. Similar results were reported by Dixit et al (2001), Mandal et al (2003), Sharma et al (2003) and Rajendran (2005). Sandyno lambs (10.8 ± 0.32 kg) were significantly (P<0.01) heavier at weaning than Nilagiri lambs (10.2 ± 0.32 kg). The mean weaning weight of Nilagiri lambs as observed in the present study was comparable to the values observed for Nilagiri (Panneerselvam 1993) and Mandya (Ganeskale 1982) and  it was lesser than Malpura, Chokla, Muzzfarnagari, Marwari, Nali, Madras Red and Sandyno (Ganeskale 1982; Singh et al 1987; Mandal et al 2003; Sharma et al 2003 and Rajendran 2005).The weaning weight of most of the synthetic breeds in India were higher than Sandyno (Singh et al 1987; Singh and Dhillon 1992 and Dixit et al 2001).            

Average daily gain

The average daily gain was significantly higher in lambs born during September (102 ± 3.24 g) than those born during March (74.8 ± 3.24 g). The availability of plenty of green pasture grass from September to November could have improved the daily weight gain in this group of lambs. No significant difference in ADG was observed between single and twin born lambs. The male had significantly higher ADG (91.7 ± 3.32 g) than female lambs (86.1 ± 3.29 g). The ADG was significantly higher in Sandyno lambs (90.3 ± 3.33 g) than Nilagiri lambs (87.4 ± 3.28 g). The Sandyno lambs had better birth weight and the Sandyno ewes weigh better at lambing than Nilagiri ewes and hence the lambs get better pre-weaning nutrition, had better ADG and hence are heavier at weaning. 

Preweaning mortality

The percentage of mortality up to weaning was higher in lambs born during MLS (8.80%) than in those born during SLS (7.03%). However, the difference was not statistically significant. Better birth weight, ADG and good condition of the dam during the pre-weaning period may have reduced the mortality in lambs born during SLS. The mortality was significantly (P<0.01) higher in twins (14.1 per cent) and triplets (33.3 per cent) than single lambs (7.28 per cent). Similar observations were made by Mukasa and Mukerwa 1992, Otesile 1993 and Anilkumar 2005. However, Yapi et al (1990) found that the death of lambs was not influenced by litter size at birth. The better birth weight, ADG and no competition for milk among single born lambs may have contributed for reduced mortality in single lambs. Mortality did not differ bewtween male lambs and female lambs.

Conclusions

• In conclusion it was found that the Sandyno lambs were heavier at birth and weaning, had better ADG than Nilagiri lambs. Similarly the lambs born during SLS were heavier at birth and weaning and mortality were less than those born during MLS, however, the numbers of lambs born during SLS were only 1/5^th of lambs born during MLS. Production of more number of lambs during SLS will improve the birth weight, ADG, weaning weight and survivability.
   

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Received 4 July 2010; Accepted 24 October 2010; Published 5 January 2011

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