Effect of Genetic and Non-Genetic Factors on Productive and Reproductive Performances of Dairy Cattle at TALIRI–Tanga

In Tanzania, milk production demands the use of crossbreeding systems that include breeds adapted to harsh conditions with moderate productivity compared to pure exotic dairy breeds. In the present study, the data from 1013 cross-bred cows raised at TALIRI – Tanga, Tanzania grouped in three genotypes, pure Boran (BB), Boran x Friesian (BF), and Boran x Jersey (BJ) were used to determine the effect of genotype, season of calving and parity on age at first calving (AFC), calving interval (CI), 305 days milk yield (MY) and lactation length (LL). The General Linear Models (GLM) procedure of SAS software 2020 was used to estimate the least square means of the traits while the MANOVA procedure in SAS 2020 was used to establish partial correlation coefficients between traits. The VARCOMP of RStudio-2023 was used to estimate variance components to calculate the heritability of the traits. The results revealed that at (P<0.05), BJ heifers had significantly shorter AFC, BF had higher MY, and BB with longer CI compared to other genotypes. The dry season calving resulted in significantly shorter LL while the fourth parity had higher MY compared to the early lactations. Cows in the fourth parity had significantly shorter CI for about 41 fewer days than those in the first parity. Heritability estimated for AFC, LL, and CI were 0.19,0.28,0.32 respectively. While phenotypic correlations (Rp) between AFC and MY were negative and weak and that between LL versus MY was moderately positive. From these findings, it is concluded that crossing of Boran cattle with Jersey or Friesian cattle can significantly improve AFC and milk yield. However, the low to moderate heritability, for reproductive and productive traits under this study, improvement of crossbred cows in hot and humid areas like Tanga should be accompanied by the improvement of the animal husbandry practices to achieve the desired output.