Reproductive performance of artificially and naturally bred Boran heifers and cows under ranch conditions in Tanzania

Wissenschaftlicher Aufsatz aus dem Jahr 2009 im Fachbereich Biologie - Genetik / Gentechnologie, , Sprache: Deutsch, Abstract: This study investigated the influence of non-genetic factors on reproductive performance of Boran cows and heifers reared under ranch conditions in Tanzania. Data on reproduction performance were collected from Kikulula Heifer Breeding Unit (KHBU) in northwestern Tanzania. Reproductive traits studied were age at first calving (AFC), calving interval (CI), days open (DO) and number of services per conception (NSC). General Linear Models (GLM) procedure of Statistical Analysis System (SAS) was used for data analyses. The overall means for AFC, CI and DO were 42.2±0.23 months, 463.6±1.93 days and 183.4±1.93 days, respectively. AFC was significantly (P<0.001) influenced by year-season and type of mating whereby heifers and cows bred in the late dry season performed better than those bred in the heavy rain season. Heifers bred by natural service were about 4 months younger at first calving than artificially bred ones. With regard to CI and DO, year-season of mating, type of mating and parity were also important sources of variation. Cows that calved in the heavy rain season had longest CI and DO than those calving in other seasons. The two traits significantly decreased from first to fourth parity and then increased. Artificially bred cows had poorer performance compared to those naturally bred. The overall mean for NSC for both heifers and cows was 1.57±0.01. Parity, year-season of mating and type of mating significantly (P<0.001) affected NSC. Heifers had the highest NSC (1.73) and were decreasing with age till fourth parity. Further, cows and heifers mated in the dry season had significantly more NSC than female cattle mated in the wet season; while artificially bred animals had significantly higher (1.71±0.03) NSC than naturally bred ones (1.53±0.03). From the findings, it is concluded that in order to improve reproductive performance, environmental factors should be accorded more serious consideration.