Abstract:
The general aim of this thesis was to evaluate how effective crossbreeding could be for increasing productivity in meat and milk production in Rwanda. This was done by assessing performance of Ankole (A) and its crossbreds with exotic breeds: Brown Swiss (B), Holstein Friesian (F), Jersey (J) and Sahiwal (S). Paper I-III were generated from records collected on growth, reproduction and milk yield of cattle genotypes from research stations and paper IV was based on survey data from farms in three agroecological zones.
Birth weight for Ankole-Jersey calves were significantly lower (25.8 kg) than for the other crossbreds, which did not differ from each other (27.5-28.4 kg). Ankole-Friesian calves (AF) were heavier than all other crossbreds at weaning (182 kg vs 152-168 kg) (Paper I).
In Paper II, the breed group had a significant effect on intervals from calving to first or last inseminations (CFI, CLI), calving interval (CI), and conception rate (CR). The cross AF had higher CR than the purebred Ankole and AS (78% vs 71% and 67%), and AS had lower CR than AJxS and AJ (67% vs 75% and 73%). Pure-bred Ankole (AA) had longer CFI and CLI than all crossbreds except AF and hade 54 days longer CI than all crossbreds (498 vs 445 days).
In the study on milk yield (Papers III-IV), AA had the lowest average daily milk yield (2.0 L); AA also tended to have longer lactation length. Among the crossbreds, there was no significant difference in milk yield between AF, AJxS, and ASxJ (4.4-4.7 L), nor between AS and ASxS (3.3 L). Paper IV revealed significant breed effects on the average milk yield, with AF producing less milk per day (8.6 L) compared with purebred Holstein Friesian (14 L). Among zones, Eastern agroeco-logical zone recorded the highest daily milk yield, which was estimated at 14.9 L compared to 9.4, 9.2, and 8.5 L in Birunga, Central and Western agroecological zones, respectively. Generally, a crossbred of Ankole and Holstein Friesian (AF) had good growth, good conception rate, and high production, but still as long calv-ing to first insemination and calving to last insemination intervals as Ankole.
