Abstract:
For years indigenous cattle breeds in communal areas have been and still are managed in adverse production environments. As a result, their growth and reproduction efficiency have been affected. Poor management, high temperatures and low rainfall generally contribute to low productivity more so in areas where cattle only feed off the veld. Improved management can however boost growth, conception and fertility levels of these animals. The study focused on the effects of breed type, sex, cow age, cow size, previous parous state, month and year of calving on reproduction and general growth traits of extensively managed Tswana and Composite beef cattle in a communal production system. A total of 6725 BWT, 5779 WWT, 5258 18MWT, 6753 CPWT, 5747 CWWT and 5313 ICP records were included in the analyses. Complete growth and reproduction records collected by the Department of Agricultural Research (DAR) of Botswana from 1993 - 2014 were analysed by means of the General Linear Model (GLM) procedure in SAS, and differences between means were tested at P <0.05. Results revealed that Composite calves grew faster and were more responsive to harsh environmental conditions. The Tswana calves showed little weight changes during years when rainfall was above and below average. Bull calves were heavier than heifers at all stages of growth. The study also found significant cow size and age effects on weight traits in both breeds. Calves born early in the season were lighter at birth but heavier at weaning and 18 months in both breeds. The effect of month of calving on cow weights showed that late calving Composite cows lost more weight from parturition to weaning than early calvers. Intercalving period varied between 361.1 - 692.5 days for Composite cows, while for Tswana cows the variation ranged from 395.5 - 705.4 days. Most cows had delayed conception for 6 - 7 months after their last calving.
