Factors which affect Gudali and Wakwa calf weights at birth and weaning on the Adamawa Plateau, Cameroon.

Birth and weaning data on zebu cattle (Gudali and Wakwa) of north Central Cameroon were analysed. Calf breed, sire and sex had significant effects (P < 0.01 or 0.001) on birth weight while parity and season of birth were not important. Calf breed, sex, season of birth and birth weight had significant effects (P < 0.05 or 0.01 or 0.001) on 8-month weaning weight. Sire and parity had no significant effects (P > 0.05) on weaning weight. Wakwa calves were heavier at birth (24.30 +/- 0.42 versus 22.6 +/- 0.56 kg) and weaning (158.32 +/- 3.46 versus 148.77 +/- 2.88 kg) than Gudali calves. An increase of 1 kg in birth weight led to an increase of 1.27 kg in weaning weight. Calves born at the end of the rainy season were heavier at birth, but were lighter at weaning than those born at the beginning of the rainy season. These results suggest that under extensive low input husbandry conditions calving should be programmed for the end of dry season/early rainy season (breeding during middle to end of the rainy season).

Genetic and environmental influences on milk and milk component production.

Estimates of genetic parameters and environmental correlations were from deviations from modified contemporary average of standardized records of first lactations of Holsteins in Pennsylvania. Records were extended to 305 days and adjusted for month of calving prior to calculation of deviations. Heritabilities from intrasire correlations among paternal sisters were .23, .26, .22, .71, and .64 for yields of milk, fat, and protein, and percentages of fat and protein. Genetic correlations were positive and generally high between yields and between percentages. Correlations of milk yield with percentages were strongly negative. Environmental correlations among paternal sisters in the same herd were .08, .11, .10, -.04, and -.03 for yields of milk, fat, and protein, and percentages of fat and protein. These statistics will be useful to plan optimum selection programs and to improve sire evaluation procedures, particularly for protein content and yield.