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Effect of breed and castration on production and carcass traits of male lambs following an intensive finishing period
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2018-06-15
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N A Claffey, A G Fahey, V Gkarane, A P Moloney, F J Monahan, M G Diskin, Effect of breed and castration on production and carcass traits of male lambs following an intensive finishing period, Translational Animal Science, Volume 2, Issue 4, October 2018, Pages 407–418, https://doi.org/10.1093/tas/txy070
Abstract
The practice of crossbreeding using a terminal sire and the use of intact rather than
castrated animals has the potential to increase the productivity of lambs produced from the hill sheep
sector. The objective of this study was to compare the production and carcass characteristics of
purebred Scottish Blackface (SB) and Texel cross Scottish Blackface (TXSB) ram and wether lambs
fed on a concentrate diet and slaughtered at different ages. Two hundred spring born male lambs
(average birth age ±SD 9.53 d) were assigned to a 2 × 2 factorial arrangement with two breeds SB
(n=100) and TXSB (n=100)) and two sexes (wether: n=100 and ram: n=100)). Lambs were harvested
following a 36 d ad libitum concentrate indoor finishing period. The study was carried out over five
harvest batches between October and April. The mean ages of the lambs at harvest (n = 40, 20 TXSB
and 20 SB lambs) in October, November, January, March and April were 196, 242, 293, 344 and 385
days, respectively The TXSB lambs were heavier at slaughter than SB lambs (P < 0.001) and ram
lambs were heavier at slaughter than wether lambs (P < 0.01). Improved average daily gain (ADG) (P
< 0.001), lower feed conversion ratio (FCR) (which was calculated by dividing total feed intake by
total weight gain) (P < 0.001) and higher feed intake (P < 0.05) were recorded in TXSB lambs with
consistency across the five harvest time points. Rams had greater ADG (P < 0.001) and FCR (P <
0.05) compared to wether lambs and no differences were observed between sexes for feed intake. The
TXSB (P < 0.001) lambs had higher (P < 0.001) dressing percentages compared to SB while wether
lambs had greater dressing percentages compared to rams. The TXSB lambs had heavier carcass
weights (P < 0.001) with higher conformation grades (P < 0.001) and less fat cover (P < 0.001) than
SB lambs while ram lambs had heavier (P < 0.001) carcasses than wether lambs. There was greater fat
cover on the loin muscles of SB (P < 0.001) and wether (P < 0.001) lambs compared to TXSB and
ram lambs, respectively. The results from this study suggest that TXSB lamb’s offer hill sheep
farmers a potential strategy for improved lamb production efficiency, while ram lambs offer lamb
finishers increased growth rates, higher FCR and produce a more desirable carcass than do wether
lambs.