1929
Zilpaterol hydrochloride modify the fatty acids profile of intramuscular fat of feedlot lambs
The objective of this study was to determine the effects of dietary zilpaterol hydrochloride supplementation on fatty acid profile of lambs´s intramuscular fat. Forty crossbred male lambs (37.7 ± 0.67 kg) were used in a 43-d feeding trial (5 pens per treatment in a randomized complete block design). Lambs were fed with finishing diet (2.57 Mcal/kg of ME) containing cracked corn 60%, sudangrass hay 16%, soybean meal 12%, molasses 9.5%, and mineral premix 2.5%, twice daily. Animals were randomly allotted to pens (6 m2) with full shade and ad libitum water. Treatments were: 1) control, no zilpaterol supplementation (ZIL-0); 2) zilpaterol for 20 d (ZIL-20); 3) zilpaterol for 30 d (ZIL-30); and 4) zilpaterol for 40 d (ZIL-40). Zilpaterol was supplemented at a rate of 0.20 mg/kg of live weight d−1 (as zilpaterol hydrochloride, Zilmax, Intervet México, México City). Twenty Longissimus dorsi muscle samples (50 g, five per treatment) were collected from left side carcass of twenty crossbred male lambs (Pelibuey × Katahdin, 50.3 ± 3.83 kg final live weight). The muscle samples were frozen (-18 ºC) and transported to laboratory for fatty acids analysis. Samples were thawed (4 ºC) and ground to homogenize them. Modified method (Folch et al.,1956) was used for lipid extraction from the muscle samples. The fatty acid composition was determined with gas chromatography (Varian, USA) and column (SP TM-2560 Fused Silica Capilary Column) 100 x 0.25 mm x 0.2 mm filmthickness and flame ionization detector. The results were analyzed with a completely randomized design, comparing means of treatments with orthogonal contrasts and orthogonal polynomials. Zilpaterol hydrochloride supplementation decrease 3.2 % (P=0.01) estearic fatty acid, and increase (P=0.06) 3.6 % linoleic fatty acid of intramuscular fat. ZIL-30 improved fatty acids profile with respect ZIL-20, reducing the level of estearic fatty acid (4.6 %; P<0.01) and increased linoleic (5.2 %; P=0.06) and araquidonic fatty acids (1.8; % P=0.07). The results indicated that zilpaterol hydrochloride supply until 40 days reduced (P=0.01; linear component) estearic fatty acid proportion and increased (P ≤ 0.05) linoleic and araquidonic fatty acids. However, the oleic fatty acid present in greater proportion was not modified by zilpaterol supplementation. Zilpaterol hydrochloride supplementation resulted in increasing the levels of polyunsaturated fatty acids and a reduction in the levels of saturated fatty acids.
Keywords: Zilpaterol chlorhidrate, fatty acids, lambs