Abstract:
Objectives were to compare growth and female reproductive performance of Landim and Africander breeds and to estimate the genetic and phenotypic variance components for growth and reproductive traits using data collected from 1968 to 1981 at the Chobela Research Station in Mozambique. Breeds were managed together and grouped bay age and sex, except when separated for breeding. Growth traits were body weights at birth, weaning at 7 mo (WW), 18 mo (W18), first calving (WFC), and pre-and post-weaning daily growth rates. Reproductive traits were age at first calving (AFC), first calving interval (FCI), and 2nd and subsequent calving intervals (CI). Growth traits were analyzed using a fixed least squares model, containing breed (B), year-season of birth (YS), sex, YS X B interaction, parity/B, and linear regression on dam’s age/B. The model for the genetic analyses also included the random effect due to sire for each trait (sire model). Africander exceeded Landim in all early body weights being about 15 + 3 kg heavier at 18 mo than Landim which average 238kg. The africander calves were 15%, 11% and 6% heavier than the Landim for birth, weaning and 18 mo adjusted weights (P≤.01), but no difference was detected for age-adjusted WFC and post-weaning daily growth (P>.5). In contrast, Landim females were 4% younger at first calving and had 47± 7 d (or 10%) shorter FCI than the Africander average of 480 d. The mechanism for this superior reproductive performance was the greater probabilities of conception for Landim females at first breeding exposure as heifers and as cows (P≤.04). Weaner and yearling productivity indices containing WW or W18. WFC and rates pf survival and calving showed that the Landim were 21% to 25% superior to the Africander in terms of weaner (P≤.01) and yearling (P≤.01) calf off take per kg of cow weight per year. In a restrictive environment like Chobela Research Station, where the expression of genetic variances should be expected to be compressed, larger components of genetic variance for early body weighs and reproduction were estimated for the Landim breed, which may signal one mechanism (i.e., additive genetic) of greater adaptation, especially in reproduction, of this breed to conditions of the local environment. Africander was widely disseminated in the tropics based on large mature size. However, the indigenous Landim was more productive in the Chobela environment partly due to diminishing weight differences with advancing age, and especially because they were more likely to conceive at first exposure as heifers and as cows. As a result Landim gained advantage by being younger at first calving and having shorter calving intervals.
