Productive and reproductive performance of Romney Marsh and Merino Branco sheep in the Azores under different feeding regimens

The objective of this study was to compare the productive and reproductive performances of Romney Marsh (RM) and Merino Branco (MB) ewes in the Azores. In a preliminary trial, fertility, prolificacy and fecundity of 25 RM and 27 MB ewes, mortality rate of lambs born and growth rate of lambs (14 RM and 20 MB) from birth to weaning at 24 kg live weight were determined. In a second trial following weaning, the same group of lambs were raised on pasture and supplemented either with concentrate or maize silage until slaughter (101 days later), and growth rate, carcass and meat characteristics were evaluated. Reproductive indices (fertility: 96% versus 93%; prolificacy: 117% versus 140%; fecundity: 112% versus 130%) and mortality rates (18% versus 17%) for RM and MB, respectively, were not significantly different. Pre-weaning gain was higher (P < 0.05) in RM lambs than BM lambs (236 ± 8.6 g/day versus 214 ± 5.8 g/day). After weaning, RM lambs grew 20% faster than MB when supplemented with concentrate, but 16% slower when supplemented with maize silage (P < 0.05). Growth of males was higher than that of females (110.3 ± 10.8 g/day versus 73.3 ± 9.3 g/day, P < 0.001). Lambs supplemented with concentrate grew twice as much as animals supplemented with maize silage (129.9 ± 9.8 g/day versus 60.5 ± 3.8 g/day, P < 0.01). Dressing percentage was not affected by breed, diet or sex. Characteristics of carcass and meat did not differ between breeds. Supplementation with concentrate resulted in thicker, fatter and wider carcasses (P < 0.01) compared to supplementation with maize silage. It was concluded that the RM and MB sheep breeds are not very different in terms of growth potential and carcass characteristics. RM performed better with improved feeding conditions, while MB was less affected when food quality declined. MB appears to be a good alternative breed for exploitation in the Azores.