Effect of breed and castration on production and carcass traits of male lambs following an intensive finishing period

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 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 with 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 with SB, while wether lambs had greater dressing percentages compared with 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 with 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.

The effect of genotype and sex on growth and carcass traits of lambs

“…Purebred lambs had significantly lower daily gains compared with Texel crossbreds which agrees with results of this study. As in our study, Claffey et al (2018) observed that crossbreds with Texel had significantly higher carcass weights, dressing percentages, and carcass conformation scores than purebred lambs. In their study, Texel crossbreds had significantly lower carcass fat scores than purebred Scottish Blackface lambs, while the present study found no difference in subcutaneous fat and internal fat between purebred JSR lambs and crossbreds with Texel.…”

“…These results are similar to findings of the present study, where crossbreds with Texel were ranked in the U-class, while purebred lambs were categorized in class R-. Claffey et al (2018) also used Texel rams as the terminal breed for commercial crossbreeding. They compared growth and carcass traits of purebred Scottish Blackface lambs and crossbreds with Texel.…”

Examining the Effects of Whole Crop Wheat Silage on Ewe Performance during Late Gestation Compared to Traditional Grass Silage across Three Prolific Breed Types

“…The lower DM (and subsequent nutrient) intake in Mule ewes compared to both Belclare X and Lleyn X ewes reported in the current study aligns with Arnold [35] who reported that Leicester X ewes had lower OMD intake per kg of BW than Merino and Dorset horn ewes. The dams of the Mule ewes in the current study were Scottish blackface, which Claffey et al [36] reported had lower intakes (kg FW) compared to Scottish blackface × Texel lambs. Regarding the findings from the current study, Arnold [35] and Claffey et al [36] suggest that Mule ewes are genetically predisposed to lower feed intakes compared to other breed types.…”

“…The dams of the Mule ewes in the current study were Scottish blackface, which Claffey et al [36] reported had lower intakes (kg FW) compared to Scottish blackface × Texel lambs. Regarding the findings from the current study, Arnold [35] and Claffey et al [36] suggest that Mule ewes are genetically predisposed to lower feed intakes compared to other breed types. However, the performance of the Mule ewes remained similar for both BW and BCS compared to the other breed types, which had increased feed intake.…”

Effect of forage to concentrate ratio and duration of feeding on growth and feed conversion efficiency of male lambs

“…Recent studies have outlined the superior growth rate and feed conversion of Texel cross Scottish Blackface ( SB ) ( TXSB ) ram and wether lambs compared with purebred SB ram and wether lambs ( Claffey et al, 2017 ). In Ireland, hill lambs (lambs from mountain regions) require an intensive feeding period to achieve 16- to 22-kg carcasses required for current market specification ( Diskin et al, 2016 ).…”