198. Effects of Rumen Protected Fat and Vitamin E Supplementation on I: Growth, Efficiency and Marbling Deposition in Wagyu X Angus Cattle.

Abstract Angus cows (n = 40) were inseminated with Wagyu ‘Oh-No’ semen. All calves from this Wagyu x Angus (n = 23; 11 heifers and 12 steers) mating were used in this study to examine the effects of rumen protected fat and vitamin E supplementation on growth, efficiency and marbling deposition. After weaning and 45-d backgrounding, calves were allotted randomly to one of two treatments within sex: 1) control, high concentrate diet (CON) or 2) high concentration diet containing 2.5% Megalac and 0.145% vitamin E (RPE). Calves were fed in 4 pens (n = 5-6/pen) with an individual SmartFeed bunk to measure individual intake by sex and treatment. Calves were fed in 3 phases: phase 1 (135 d feedlot) fed via SmartFeed (C-Lock) for individual intake measurement with treatments, phase 2 (78 d pasture), and phase 3 (74 d feedlot) with treatments fed via SmartFeed bunks. Data were analyzed with phase, sex, treatment and all interactions in the model. All interactions were non-significant. Dry matter intake (DMI) did not differ by treatment or phase. Average daily gains were greater (P < 0.05) and feed efficiency (FCR and RFI) improved (P < 0.05) for RPE than CON in both phase 1 and 3. Marbling scores was higher (P < 0.05) by 71 points for RPE than CON. Crude fat content of the longissimus muscle (LM) was greater (P < 0.05) by 32% for RPE than CON. Longissimus muscle color did not differ; however, subcutaneous fat L* (lightness) was lower (P < 0.05) for RPE than CON. Conjugated linoleic acid (cis-9 trans-11 isomer) concentration was greater (P < 0.05) for RPE than CON. The correlation between RFI values between phase 1 and phase 3 was 0.65 indicating that there was some reranking of RFI based on finishing phase. The correlations between RFI and feed efficiency were 0.84 and 0.52 for phase 1 and phase 3, respectively. Supplementation of rumen-protected fat and vitamin E to finishing cattle improved average daily gain, feed efficiency, and marbling deposition in Wagyu x Angus cattle.