ANALYSES OF GROWTH CURVE PARAMETERS OF N’DAMA CATTLE RAISED IN THE HUMID TROPICS

Abstract

Individual growth curve parameters are suitable phenotypic variable for the assessment of growth course and early maturity. This study focused on the analyses of growth curves parameters of N’Dama cows derived from the Richarads growth function. Data consist of field records of weight measurements from birth to 36 months old of 98 N’Dama cows born and raised between 1992 and 1998. The coefficient of variation was moderately high in both the curve and predicted parameters except for point of inflation (m). The estimates of heritability for maturing traits ranged from 0.18 to 0.30. While those for body weights and growth traits ranged form 0.21 to 0.47. High correlation coefficients were observed between mature weight parameter (A) and body weight at 180 days. 365days and 550days of age. A negative relationship was observed between A and maturing rate index k,(0.51) and between A and all maturing parameters associated with stages of growth (degrees of maturity and relative growth rates). Sire variation was an important source of variation (P < 0.05) for all the parameters studies except for residual means squares (RMS). Year of birth was also a significant (P < 0.05), source of variation for A, K, RMS, degrees of maturity at 180days of age and the relative growth rates at 180days and 365 of age, while age of dam significantly (P < 0.05) affected the constant of integration b, the maturing rate index k, body weight and degree of maturity at 180days of age. Season of birth affected the point of inflation (m) RMS body weight at 180day and absolute growth rate at 365days of age. The interaction between year of birth and age of dam was significant (P < 0.05), affecting only the A and the K parameters