Pregnancy, Parturition and Resumption of Ovarian Cyclicity in Beef Cows

Abstract

Communal farmers find it very difficult to control animal breeding hence fixed Time Artificial Insemination (TAI) is a promising technique. The objective of this study was to determine the effects of bull age and breed on pregnancy rate, and the post-partum interval in extensively managed communal beef cows. A total of 577 female animals with a body condition score between 2.5 and 3, from three breeds; Brahman (189), Nkone (18) and Mashona (370) were used. Fixed time artificial insemination using the ovsynch protocol was done using semen from four different bull breeds (Mashona, Tuli, Brahman and Boran) aged between 3 to 6 years. The percentage of cows identified pregnant were analysed using generalized linear mixed model PROC GLIMIXX of SAS. The effects of cow parity on PPI were evaluated using the general linear model of SAS. Conception rates were 53.2; 57.3 and 75% for Brahman, Mashona and Nguni cows respectively. Animals in their third parity had the highest conception rate. Young bulls less than 3 years of age had the least pregnancy rate while Mashona bulls had the highest pregnancy rate. There was a breed by parity interaction on PPA interval (P < 0.05). It can be concluded that PGF2α and Estradiol Benzoate (EB) could be successfully used to induce and synchronize ovulation in cattle undergoing TAI, sire age significantly influenced conception rate as well as that the post-partum interval is dependent on breed and parity.