Genetic aspects of growth and maturing rate in trypanotolerant beef cattle: N'Dama

Abstract

Genetic parameters for Absolute Growth Rate (AGR), Relative Growth Rate (RGR) and Absolute Maturing Rate (AMR) at various age interval from birth to maturity in N'Dama beef cattle raised in the humid tropics of Nigeria were estimated. Performance data used were accumulated between 1948 and 1964 at Fasola cattle ranch in Oyo, Nigeria and the number of records analysed ranged from 44 to 678. preweaning (B – W) growth and maturing rates in N'Dama calves were 0.377 + 0.009 kg/day (AGR), 0.643 + 0.006 %/day (RGR) and 0.120 + 0.003% A/day (AMR) and fluctuate subsequently, following the animals' state of development and certain physiological stress conditions. At post weaning (W – 12), these rates decreased to 0.249 + 0.049kg/day, 0.204 + 0.029%/day and 0.075 + 0.014 % A/day for AGR, RGR and AMR respectively. Estimates of heritability at the various age intervals were considered low in these growth traits with values obtained ranging from 0.03 to 0.24 for AGR, 0.03 to 0.21 for RGR and ).02 to 0.42 for AMR, with high standard errors. The low estimates though, consistent with literature reports were attributed to the poor standard of animal management and production environment at Fasola. It was evident from this study that selection of N'Dama calves based on post weaning (W – 12) growth or maturing rates would yield substantial genetic progress. However, improved animal management and production environment on the ranch would not only improve precision of the genetic parameter estimates but would also enhance N'Dama growth performance generally.
Keywords: Growth rates, maturing rates, genetic parameters, trypanotolerant cattle.