Dietary supplementation with a zilpaterol and natural additive blend on cut yield and meat quality of fattening hair lambs under conditions of high ambient temperature

Forty-eight Pelibuey × Katahdin male lambs (90 ± 18 d age; 25.12 ± 3.79 kg LW) were fed for 70 d under conditions of high ambient heat load (average Temperature Humidity Index (THI) = 80.6 ± 3.2) to test feed additive strategy supplementation in a high-energy diet, as follows: 1) no feed additives (control), 2) a blend of essential oils (EO) plus vitamin D3 offered throughout 70 d of fattening (EOD3), 3) zilpaterol hydrochloride (ZH) offered during the final 35 d of fattening, and 4) a combination of EOD3 with ZH (EOD3+ZH). The experimental design used was a randomized complete-block design in a 2 × 2 factorial arrangement of treatments (ZH and EOD3 factors). The ambi-ent temperature and relative humidity during the experiment were 29.2 ± 3.4 °C and 73.1 ± 14.1 % (THI = 80.6 ± 3.2), respectively. These ambient conditions represent a high ambient heat load that can compromise the productivity and quality of the final product. There were no interaction effects (P > 0.38) on the shoulder muscle tissue composition and whole cuts. Except for a reduction in drip loss (interaction, P = 0.05) and an increase in the intensity of yellow col-or (b*), which was increased (interaction, P < 0.01), the combination of EOD3+ZH did not affect the rest of the meat quality variables. EOD3 supplementation alone had no effects on meat characteristics but decreased the water-hold-ing capacity by 2.9% (P < 0.01) and increased drip loss by 2.14% vs. 1.65% (P = 0.04) at 24 h. Lambs supplemented with ZH alone showed an increase (P < 0.01) in lean tissue (4.6%), whole cut of leg percentage (3.6%), and a* color value (17%) (P = 0.02), but reduced thawing by 50% (P < 0.03). It was concluded that the EOD3 blend supplemented alone or combined with ZH to fatten lambs under high ambient heat load conditions had no effects on tissue composition and whole cuts and had a small effect on meat quality improvements. ZH supplementation affected fat deposition and meat yield without affecting the meat shear force.