Abstract :
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 theRMandMBsheep 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.
© 2005 Elsevier B.V. All rights reserved.
Keywords :
Romney Marsh , fertility , supplementation , Carcass , Merino Branco
