Effects of zilpaterol hydrochloride on growth performance, carcass characteristics, and wholesale cut yield of hair-breed ewe lambs consuming feedlot diets under moderate environmental conditions

Abstract

Twenty-four Dorper × Pelibuey ewe lambs initially weighing 25.1 ± 0.6 kg were used in a 34-d feeding experiment and after slaughter to evaluate the effect of zilpaterol hydrochloride (ZH) on feedlot performance, carcass characteristics, and wholesale cut yield. Ewe lambs were individually housed in pens, blocked by initial BW, and assigned randomly within BW blocks to 1 of 2 treatments: 1) control (no ZH) and 2) supplemented with ZH (10 mg/ewe lamb daily) during 32-d and a 2-d withdrawal preslaughter period. Feeding ZH increased (P < 0.01) final BW, ADG, and G:F of ewe lambs, whereas feed intake was unaffected (P = 0.80). Hot and cold carcass weights, dressing percentage, and conformation score were improved (P < 0.001) when ZH was fed. Likewise, LM area was 3.7 ± 0.41 cm(2) larger (P < 0.001) for ZH than control ewe lambs. Feeding ZH did not affect (P ≥ 0.29) cooling loss, carcass length, fat thickness, or KPH. With exception of peritoneum (P < 0.001), head (P = 0.021), and neck (P < 0.001), ZH did not increase (P ≥ 0.12) noncarcass components or wholesale cut yield percentage. A trend to increase (P = 0.060) loin percentage from HCW was observed in lambs supplemented with ZH. In conclusion, feeding ZH to Dorper × Pelibuey ewe lambs improved feedlot performance and also some carcass traits (HCW, cool carcass weight, dressing percentage, and LM area) of economic importance; however, fat deposition was not affected by ZH.

Feedlot performance and carcass traits of hairbreed ewe lambs in response to zilpaterol hydrochloride and soybean oil supplementation

“…In the present study, ZH increased HCW, CCW, dressing percentage, and LM area. These findings agree with previous studies done in hairbreed ewe lambs (Macías-Cruz et al, 2010;Avendaño-Reyes et al, 2011). Similarly, in male lambs, Mondragón et al (2010) and López-Carlos et al (2011) reported that ZH increased HCW, CCW, dressing percentage and LM area.…”

“…These results suggest that ZH improved carcass weight in ewe lambs by influencing an internal redistribution of nutrients and not by a greater feed intake. This finding also was observed previously in ewe lambs by Avendaño-Reyes et al (2011). Montgomery et al (2009) indicated that differences observed in dressing percentage and HCW due to supplementation with ZH could be attributed to a change in mass from noncarcass to carcass tissue or by a decrease in gut fill caused by a decrease in DMI.…”

“…Perhaps ZH mobilized lung tissue to promote carcass muscle development (Montgomery et al, 2009). However, other studies have not reported a negative effect of ZH on lung weight as percentage of final BW (Avendaño-Reyes et al, 2011;Dávila-Ramírez et al, 2014;López-Carlos et al, 2014). In general, reduced presence of β-AA receptors in smooth muscle has been linked to the absence of effect of ZH on noncarcass components (Reeds and Mersmann, 1991).…”

“…The following procedures have been described in detail in our previous publications (Macías-Cruz et al, 2010;Avendaño-Reyes et al, 2011;Dávila-Ramírez et al, 2014). Briefly, 32 Dorper × Pelibuey crossbred ewe lambs (30.55 ± 2.57 kg and 5 mo of age) were individually housed in pens equipped with shade, feed troughs, and water.…”

“…All carcass (HCW, CCW, dressing, cooling loss, conformation, KPH, fat thickness, LM area, postmortem pH of LM at 45 min and 24 h, carcass length, thorax depth, leg length, and leg perimeter) and noncarcass (head, blood, skin, heart, lungs, liver, kidney, peritoneum, renal fat, rumen, and intestine) data were collected following procedures previously described by Dávila-Ramírez et al (2014). Carcasses were split in half, and the right side was used to obtain wholesale cuts (forequarter, neck, ribs, loin, shoulder, hindquarter, leg, plain loin, and sirloin) following the methodology described by Avendaño-Reyes et al (2011). Noncarcass components were expressed as percentage of the final BW and wholesale cuts were expressed as percentage of HCW.…”