Crossbreeding with Africander dam as basis: 1. Duration of gestation, mass at birth and incidence of dystocia in crossbred progeny of various breeds of' sires
The effect of different sire breeds, representing various types of breeds, on duration of gestation, mass at birth and incidence of dystocia in the progeny from Africander cows, was investigated. During a period of five years 838 calves were born and the analytical model furthermore included production status of dam, age. of dam, stage of birth of calf and sex of calf. The duration of gestation of the Bos indicus sired progeny was notably longer than that of Bos taurus sire breeds with 293,65 and 292,76 days for the Africander and Brahman, and 290,39, 289,19 and 286,29 days for the Simmentaler, Charolais and Hereford respectively. The birth mass of the progeny of Africander, Hereford, Simmentaler, Brahman and Charolais sires were 32,83, 34,94, 36,34, 37,33 and 40,41 kg respectively. The incidence of dystocia was the highest in the case of the Charolais progeny ( 16,0%) followed by the progeny of the Brahman (8,2 %), Hereford (7,7 %), Simmentaler (6,9 %) and straightbred Africander (3,0%). The correlation between duration of gestation and birth mass within breed of sire progeny groups was 0,243 (P< 0,05).