D. R. Campion

Composition and quality characteristics of 1,121 steer carcasses obtained after mating Hereford and Angus cows to Hereford, Angus, Jersey, South Devon, Limousin, Charolais and Simmental sires were compared at a (1) constant age, (2) constant weight, and (3) constant percentage of fat in the longissimus muscle. Taste panel evaluation was made on a sub-sample of 496 carcasses. Growth rate of retail product, fat trim and bone differed significantly among sire breed groups. Breed group differences in relative proportions of retail product, fat trim and bone were largest when compared at a constant carcass weight and smallest when compared at equal fat in the longissimus. There was a positive association between growth rate of breed groups and percentage of retail product or bone. A negative association was observed between growth rate of breed groups and percentage of fat trim. A negative association between growth rate and percentage of fat in the longissimus resulted in breed groups attaining the same percentage of fat in the longissimus at significantly different average carcass weights. Conformation and marbling attributes of quality grade differed significantly among breed groups, but color, texture and firmness of lean and maturity differences were small. Tenderness differences among breed groups were small with all breed groups well above minimum levels of acceptance. Breed group means for taste panel tenderness and marbling were positively associated. Within breed groups, the desirable influence of increased marbling associated with time on feed was essentially counteracted by the undesirable influence of increased age. Breed groups did not differ significantly in flavor or juiciness scores.

Effects of fiber vs starch energy supplements on endogenous growth hormone (GH), insulin-like growth factor (IGF-1) and animal performance from weaning to breeding age were evaluated in 18, 9-mo-old beef heifers. Heifers had ad libitum access to wheat silage plus an average daily supplement intake of 1) 4.08 kg corn-soybean meal (SBM) (high energy-starch, HS), 2) 4.54 kg soyhulls (SH)-SBM (high energy-fiber, HF) or 3) 1.36 kg SH-SBM (low energy-fiber, LE). Serum samples were collected via jugular puncture every 10 d and were analyzed for IGF-1 by RIA. On d 45 and d 176, four heifers per treatment were fasted 18 h and serial blood samples collected via jugular cannulas every 15 min for 6.5 h. Arginine (.5 g/kg BW) was administered intravenously (ARG) to induce release of GH, and four additional samples of blood were collected. Samples were analyzed by RIA for GH. Mean fasted GH (6.4 +/- .4, 8.3 +/- .4 and 13.8 +/- .4 ng/ml for HS, HF and LE, respectively) varied with energy source and level (P less than .01). Mean GH following ARG was higher (P less than .01) in heifers receiving LE (46.2 +/- 4.7) than in those receiving HS and HF (23.5 +/- 4.4 and 24.1 +/- 4.6 ng/ml). Basal GH concentration and peak amplitude were higher (P less than .05) in LE than in HS and HF treatments. Diet did not influence number or frequency of GH peaks.(ABSTRACT TRUNCATED AT 250 WORDS)

The objective was to evaluate the effect of feeding oxidized corn oil with or without a dietary antioxidant (AOX) on performance, tissue oxidative status, and meat quality in barrows. One hundred sixty barrows were arranged in a 2 × 2 factorial of treatments in a complete randomized block design with 8 pens per treatment and 5 pigs per pen. Diets contained 5.0 mg/kg of 1 of 2 types of corn oil (fresh or oxidized) with or without antioxidant. Final oxidized oil was produced in a heated container by continuously bubbling air heated to 95°C at a rate of 80 L/min to reach a target peroxide value of approximately 150 and 7.5 mEq/kg in the final diet. After 56 d, barrows fed diets formulated with fresh oil had increased ADG (P = 0.03) and ADFI (P = 0.04) and heavier final BW (P = 0.03) than barrows fed oxidized oil. Increased G:F (P = 0.07) was observed for barrows fed diets with AOX after 28 d of feeding but not after 56 d of feeding (P = 0.67) when compared with barrows not fed AOX. An increase (P = 0.06) in plasma thiobarbituric acid reactive substances (TBARS) values, a decrease (P = 0.03) in plasma glutathione peroxidase (GPx) enzyme activity, and a decrease (P = 0.01) in liver vitamin E concentrations were observed in barrows fed diets with oxidized oil. Dietary AOX reduced plasma protein carbonyl content regardless of oil type (P = 0.04). Barrows fed fresh oil had 4.4% heavier HCW (P = 0.01) and 0.7 percentage units increase in dressing percentage (P = 0.01) compared with barrows fed oxidized oil. Loin TBARS values from barrows fed AOX were lower (P < 0.001) after 14 and 21 d of storage in both fresh and oxidized oil groups. In summary, oxidized oil impaired growth performance and caused oxidation stress. Dietary AOX partially ameliorated the negative effects of oxidized oil in finishing pigs by reducing protein oxidation and improving shelf life.