Yearly production trends and genetic and environmental influences in a genetically closed Brahman herd. 4. Percentages of pregnancy, calving, weaning, availability at 18 months and production per cow

Abstract

In a Brahman herd, non-genetic effects were evaluated on the procreation percentage when diagnosing pregnancy (P), at calving (N), at weaning (D) and when the calf was 18 months old (X); also on live weight production per cow in herd at weaning (PDVR) and at 18 months (P18VR). The analyzes of variance used Models I and II, which included: year of service (A, 1965-1975); bull in service (T, N=45); lactation status (L, only Model I); age in TS (E, 2-13 years); and weight at the beginning of TS (PS). Significant effects (P<.01) had A, T and E on all four procreative characters in both models; L (Model I) also had them; PS had effects (P<.05) on P and N (Model I) and on D and X (Model II). The adjusted mean percentages of P, N, D (n=2092) and X (n=1877) were: Model I, 72.9±2.1, 67.7±2.2, 62.2±2.3 and 58.3±2.4; Model II, 69.1±1.6, 65.0±1.7, 59.7±1.8, 56.8±1.9. The constants of the bull with the highest value exceeded those of the lower bull in P, N, D and X by 192, 233, 191 and 225%. At 2 years of age, the constants were lower (-28.5, -25.8, -25.3 and -22.7%), while the maximum values ​​corresponded to E = 5 and 6 years. The average BW was 399±1.3kg and for each increase of 10kg the percentages of P and N each rose 0.6. The cumulative mortality of children, from P to N, D and X was 5.5, 11.7 and 13.8%, having a marked tendency to decrease over time. The PDVR and P18VR averages were 93.3 and 167.6kg, with increases between 1965 and 1974 of 221 and 264%. The annual elimination rate of heifers and cows showed averages of 19 and 20%, respectively.