Effects of zilpaterol hydrochloride and soybean oil supplementation on feedlot performance and carcass characteristics of hair-breed ram lambs under heat stress conditions

Abstract

Forty Dorper × Pelibuey ram lambs initially weighing 31.7 ± 2.30 kg were stratified by BW and randomly assigned to treatments under a completely randomized design with a 2 × 2 factorial arrangement of treatments to evaluate effects of zilpaterol hydrochloride (ZH; 0 or 10 mg/lamb daily) and soybean oil (SBO; 0 or 6%) on feedlot performance, carcass characteristics, and wholesale cut yield of ram lambs under heat stress conditions. After a 34-d feeding period, all lambs were harvested. Climatic conditions were of moderate heat stress (average temperature 35.7°C) for lambs during the study. Interactions ZH × SBO were not observed (P ≥ 0.11) for any of the variables evaluated. During the first 17 d of experiment, ZH increased (P ≤ 0.05) BW, ADG, and G:F without affecting feed intake (P = 0.40), but from d 18 to 34 and the entire 34-d feeding period, feedlot performance was not affected (P = 0.18) by ZH. Also, ZH decreased KPH, dressing percent, LM area, LM pH at 24 h postmortem, and leg perimeter (P ≤ 0.04). Renal fat (P = 0.03) decreased with ZH while other noncarcass components were not affected (P ≥ 0.06) by ZH supplementation. Leg yield (P = 0.01) and plain loin (P = 0.04) decreased with ZH and yields of other wholesale cuts were not affected (P ≥ 0.10) by ZH. Feedlot performance (P ≥ 0.20) and wholesale cut yield (P ≥ 0.21) were not affected by SBO. Additionally, dressing percentage decreased (P < 0.01) with SBO while other carcass characteristics (P ≥ 0.12) were not affected by SBO. In conclusion, inclusion of both ZH and SBO in feedlot finishing diets did not improve feedlot performance, carcass characteristics, or wholesale cut yield of hair-breed ram lambs under moderate heat stress. Feedlot performance responded only to ZH and only during the first 17 d of the feeding period. In addition, some carcass characteristics of economic importance, such as dressing, LM area, and leg yield, were improved by ZH.

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

“…In the present study, feedlot performance of ewe lambs was not altered by the SBO addition at 6% (DM basis) of the finishing diet. These outcomes agree with results found by Dávila-Ramírez et al (2014) in Dorper × Pelibuey ram lambs fed SBO and by Kim et al (2007) in Katahdin × Dorper lambs fed soybean, linseed, or cottonseed oil. Similarly, in wool genotype lambs (Corriedale or Hampshire × Dorset), Choi et al (2006) and Radunz et al (2009) also reported that SBO and linseed oil supplementation in finishing diets did not affect final BW, ADG, DMI, and G:F. Therefore, our results in combination with those of the literature indicate that SBO supplementation has no benefit on growth of sheep finished in feedlot.…”

“…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.…”

“…After recording final BW, all ewe lambs were slaughtered in the meat laboratory of the ICA at the UABC. 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).…”

“…Results from this experiment indicated minor SBO effects on carcass characteristics in ewe lambs, with only pH of the LM changed at 24 h postmortem by SBO supplementation. Other studies also indicated few or no advantages on carcass traits with inclusion of vegetable oils in finishing diets of sheep (Boles et al, 2005;Radunz et al, 2009;Dávila-Ramírez et al, 2014;Ferreira et al, 2014). However, none of these studies reported the effect of SBO or other vegetable oil on the pH of the LM.…”