Effects of Vitamin A Supplementation in Young Lambs on Performance, Serum Lipid, and Longissimus Muscle Lipid Composition

¹ Kansas State University, Manhattan, 66506

^* To whom correspondence should be addressed. E-mail: mdikeman{at}ksu.edu.

	Abstract

Forty crossbred wethers (BW = 28.7 kg) were used to evaluate the effects of diets containing high and low levels of vitamin A on LM lipid composition. Four treatments arranged as a 2 X 2 factorial with a completely random design were investigated: backgrounding (BG) and finishing (FN) with no supplemental vitamin A (LL); BG with no supplemental vitamin A and FN with high vitamin A (6,600 IU·kg ^-1 diet) supplementation (LH); BG with high vitamin A supplementation and FN with no vitamin A supplementation (HL); and BG and FN with high vitamin A (HH) supplementation. Diets included cracked corn (62.4%), soybean meal (16.0%), cottonseed hull pellets (14.8%), and supplement (7%) and contained <100 IU vitamin A kg ^-1 from carotenes before vitamin A was added. During the BG period (d 1 to 56), feed intake was restricted to achieve 0.22 kg ADG. During the FN period (d 57 to 112), lambs consumed the same diet ad libitum. Lambs were weighed every 14 d and blood sampled every 28 d to map changes in serum fatty acids (FA) and vitamin A levels. Lambs were humanely slaughtered after 112 d. Lipid composition was determined for liver and longissimus tissues. There were no treatment differences (P > 0.05) in feed intake, ADG, or final BW.. Carcass weights were not affected by vitamin A treatment (P > 0.20), although backfat thickness tended to be different between HL and LL lambs (0.80 vs. 0.64 cm, respectively; P = 0.08). Carcasses from the HH group had higher (P < .05) marbling scores (514 vs. 459), and 25.8 % more extractable intramuscular lipid than LL (3.88 vs. 3.08 % for HH and LL, respectively, P < .05); the LH and HL treatments were intermediate. Interestingly, the LL group had the greatest increase in serum FA throughout the experimental period (change of 127 vs. 41 µg·g^-1 for LL and HH, respectively; P < .01). Degree of saturation of fatty acids was not affected by treatment (P = .18) in the serum but was affected in LT fat. Oleic acid increased and linoleic acid decreased in the LM of HH-treated lambs (P < 0.02). These data suggest that increases in total intramuscular lipid may be achieved with high levels of vitamin A supplementation for 112 d in young lambs.

Key Words: fatty acids, lambs, lipids, meat quality, vitamin A