Effect of breed, season, year and parity on reproductive performance of dairy cattle under smallholder production system in Bukoba district, Tanzania
Livestock Research for Rural Development
Department of Animal Science and Production, Sokoine University of Agriculture, P.O.Box 3004, Morogoro, Tanzania
A study was conducted to evaluate the effects of breed level and non-genetic factors on reproductive performance of dairy cattle under smallholder production system. The study focused on assessing the reproductive efficiency of dairy cattle under smallholder farms in Bukoba district, Tanzania. Data on age at first calving (AFC), calving to first service interval (CFSI), number of services per conception (NSC), days open (DO) and calving interval (CI) were collected from Kagera Dairy Development Trust (KADADET) in Bukoba district. General Linear models procedure of Statistical Analysis System (SAS) computer software was used to analyse the data. The fixed effects considered in the analyses were genetic group, parity, season and period of birth or of calving. The overall mean for AFC was 35.1±9.7 months with a coefficient of variation of 18.6%, for CFSI it was 196.95±1.8 days with a coefficient of variation of 20% while the mean for NSC was 1.66±0.0 with a coefficient of variation of 21%. Further, the mean DO was 205.2±2.6 days with coefficient of variation of 19%, and CI averaged 480.4±2.4 days with a coefficient of variation of 22%. AFC was significantly affected by period of birth (P<0.001), level of exotic blood (P<0.05) and season of birth (P<0.05). Genetic group significantly influenced CFSI, NSC, CI (P<0.05) and DO (P<0.001). F1 crosses performed better than high-grades in all the traits with 34.6 months of AFC, 171 days of CFSI, 182 days of DO, and 455 days of CI. Season of calving significantly influenced CFSI (P<0.01), CI (P<0.001), NSC and DO (P<0.05). Cows calving in the long rain season were superior with 17 days of CFSI, 21 days open and had shorter (by 27 days) CI than those calving in the long dry season. Parity and period of calving significantly affected CFSI (P<0.05 and P<0.001), NSC (P<0.05), DO (P<0.01 and P<0.001), CI (P<0.05 and P<0.001) respectively. For these traits, performance was improving by advancement in age of cows. Milk yield in the first 100 days of lactation had no significant influence on post-calving reproductive traits. It was concluded that reproductive performance was best in the long rain season and that with respect to reproductive traits F1 crosses were better than high grades in Bukoba district.