Reproduction rate and viability of Nilagiri and Nilagiri synthetic sheep Chaudhari A.B., Ramanujam R.*, Ragothaman V.1, Sundaram S. Meenakshi2 Department of Animal Genetics and Breeding, Madras Veterinary College, Chennai-600 007, Tamil Nadu 1Post Graduate Research Institute in Animal Sciences, Kattupakkam-603 203, Tamil Nadu 2Centre for Animal Production Studies, Tamil Nadu Veterinary and Animal Sciences University, Chennai-600 051, Tamil Nadu *E-mail address: drrajjam@gmail.com
Online Published on 12 February, 2024. Abstract Reproduction data of 4527 Nilagiri and 5950 Nilagiri Synthetic breeding ewes maintained at Sheep Breeding Research Station, Sandynallah (Tamil Nadu), spread over 27 years (1989 to 2015) were used to evaluate the replacement rate, reproduction rate, flock structure and dynamics. The replacement rate was significantly higher (P<0.001) in Nilagiri (0.29) than Nilagiri Synthetic sheep (0.26). The age-specific death rate ranged from 0.026 (3.5 to 4.5 years) to 0.191 (6.5 to 7.5 years) with highest of 0.191 and 0.134 in Nilagiri and Nilagiri Synthetic sheep from 1.5 to 7.5 years of age, respectively. The retention period of five years of age with a net reproduction rate of 1.024 in Nilagiri and six years of age with a net reproduction rate of 1.196 in Nilagiri Synthetic was found ideal to meet replacement requirement of flock. Nilagiri ewes in intermediate ages had more multiple births and older ewes weaned more lambs. The retention of Nilagiri ewes up to fifth lambing and Nilagiri Synthetic ewes up to third lambing in the flock was found ideal to maintain flock strength. The results of Ro and rm showed that the flock must consist of six age groups to maintain its size and replacement. It may be recommended to cull the breeding ewe at the age of six years to accelerate genetic improvement. Based on the findings, suitable breeding policy of selection and culling should be formulated. Top Keywords Age-specific death rate, Flock dynamics, Multiple births, Replacement rate, Sheep, Viability. Top |