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 ofBoran cows and heifers reared under ranch conditions in Tanzania. Data on reproductionperformance were collected from Kikulula Heifer Breeding Unit (KHBU) in northwesternTanzania. 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. Theoverall means for AFC, CI and DO were 42.2±0.23 months, 463.6±1.93 days and 183.4±1.93days, respectively. AFC was significantly (P<0.001) influenced by year-season and type ofmating whereby heifers and cows bred in the late dry season performed better than thosebred in the heavy rain season. Heifers bred by natural service were about 4 months youngerat 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 theheavy rain season had longest CI and DO than those calving in other seasons. The two traitssignificantly decreased from first to fourth parity and then increased. Artificially bred cowshad poorer performance compared to those naturally bred. The overall mean for NSC forboth heifers and cows was 1.57±0.01. Parity, year-season of mating and type of matingsignificantly (P<0.001) affected NSC. Heifers had the highest NSC (1.73) and weredecreasing with age till fourth parity. Further, cows and heifers mated in the dry season hadsignificantly more NSC than female cattle mated in the wet season; while artificially bredanimals had significantly higher (1.71±0.03) NSC than naturally bred ones (1.53±0.03). Fromthe findings, it is concluded that in order to improve reproductive performance,environmental factors should be accorded more serious consideration.