The effects of castration (ram lambs versus wether lambs) on animal growth, feed efficiency, carcass characteristics,...

The aim of this experiment was to investigate the differences between intact (ram) and castrated (wether) lambs by evaluating animal growth pre- and post-weaning, feed efficiency, carcass characteristics, and carcass cutability. A total of 144 lambs were used for this feeding experiment (ram; n = 72 and wether; n = 72) and 70 lambs (ram; n = 35 and wether; n = 35) were slaughtered at the end of an 8-wk finishing period. Treatment (ram or wether) was randomly assigned shortly after birth. During the finishing period, lambs were weighed every 14 d. Lambs were slaughtered over five harvest dates based on live weight targets, evaluated for carcass characteristics 24-h postmortem, and fabricated into subprimal cuts 48-h postmortem, with weights collected from each subprimal. Results for the finishing period were analyzed using PROC MIXED in SAS with a fixed effect of sex with random effects of group (location and lambing season) and block. Carcass and economic value data were analyzed using PROC GLIMMIX in SAS with a fixed effect of sex and random effects of pen, block, and season. In terms of animal growth, there was a sex × time interaction (P < 0.01) for lamb body weight (BW), resulting in rams having heavier BW throughout the 8-wk finishing period. In addition, ram lambs also had a greater gain to feed (G:F) ratio (P < 0.01) and average daily gain (ADG) (P < 0.01). Furthermore, there was a sex × time interaction for dry matter intake (DMI) (P = 0.04) as ram lambs consumed more feed when compared with wether lambs. In the abattoir, ram lambs retained heavier carcasses (P < 0.01), with larger ribeyes (P < 0.01) and were trimmer (backfat thickness; P < 0.01 and bodywall thickness; P = 0.02), with overall lamb quality being equivalent between treatments as indicated by similar overall quality grades (P = 0.99) and degree of fat flank streakings (P = 0.53). Moreover, ram lambs were higher yielding for several meat cuts including neck, shoulder, foreshank, breast, trotters, and leg (P < 0.05) when compared with wether lambs. Within the context of this experiment, ram lambs exhibited greater weight gain, feed efficiency, carcass yield, and cutability. With uncertainties remaining as to the consumer acceptability of meat produced from ram lambs, coupled with increased DMI required by growing ram lambs; further investigation is needed to support the production of ram lambs for meat production.