The objective of this study was to determine whether increasing levels of dietary safflower oil would alter unsaturated fat (especially CLA) and tocopherol content of lamb, animal performance, carcass characteristics, or color stability of lamb muscle tissue. Targhee x Rambouillet wethers (n = 60) were assigned to one of three diets (four pens per treatment with five lambs per pen) in a completely random design. Diets were formulated with supplemental safflower oil at 0 (control), 3, or 6% (as-fed basis) of the diet. Diets containing approximately 80% concentrate and 20% roughage were formulated, on a DM basis, to be isocaloric and isonitrogenous and to meet or exceed NRC requirements for Ca, P, and other nutrients. A subsample of 12 wethers per treatment was selected based on average BW (54 kg) and slaughtered. Carcass data (LM area, fat thickness, and internal fat content) and wholesale cut weight (leg, loin, rack, shoulder, breast, and foreshank), along with fatty acid, tocopherol, and color analysis, were determined on each carcass. The LM and infraspinatus were sampled for fatty acid profile. Increasing safflower oil supplementation from 0 to 3 or 6% increased the proportion of linoleic acid in the diet from 49.93 to 55.32 to 62.38%, respectively, whereas the percentage of oleic acid decreased from 27.94 to 23.80 to 20.73%, respectively. The percentage of oil in the diet did not (P > or = 0.11) alter the growth and carcass characteristics of lambs, nor did it alter the tocopherol content or color stability of meat. Increasing levels of safflower oil in lamb diets decreased (P < 0.01) the weight percentage of oleic acid in the infraspinatus and LM, and increased linoleic acid (P < 0.01). Oil supplementation increased (P < 0.01) the weight percentage of various isomers of CLA in muscle, with the greatest change in the cis-9,trans-11 isomer. Supplementation of sheep diets with safflower oil, up to 6% of the diet, resulted in increasing levels of unsaturated fatty acids and CLA in the lean tissue, without adversely affecting growth performance, carcass characteristics, or color stability of lamb.

Straw from small grains could be an important source of feed for maintenance of ruminants if its nutritive quality could be improved. This study was conducted to determine any differences in straw digestibility among and between cultivars of winter and spring wheats (Triticum aestivum L. var. aestivum, and T. turgidum L. var. durum), barley (Hordeum vulgare L.), and oats (Avena sativa L.) grown in eastern Montana. In vitro dry matter digestibility, crude protein, and P content of straw were measured on 8 to 25 cultivars of each crop for 2 years. Heading date, plant height, lodging severity, and grain yield were also determined to detect whether selecting for higher straw digestibility would adversely affect these important traits for grain production. The average in vitro digestibility of straw of winter wheat, spring wheat, barley, and oats was 36, 36, 40, and 45% the first year, and 40, 42, 47, and 45%,, respectively, the second year. Differences in straw digestibility were greater among cultivars within a crop than between crops. Straw digestibility of winter wheat, spring wheat, and barley cultivars differed by 9 and 14 percentage units, depending on crop and year. Straw of oat cultivars differed by 8 percentage units the first year but only 4 percentage units the second year. Differences in straw digestibility among crop cultivars was as great as some researchers have achieved by chemically treating the straw to improve its digestibility. Cultivars with higher straw digestibility did not have higher lodging or lower grain yield. Neither was straw digestibility consistently associated with heading date, plant height, crude protein, or P content. The first year, the average crude protein of winter wheat, spring wheat, barley, and oat straw was 2.5, 2.7, 4.4, and 3.3%, respectively; the second year, it was 2.5, 4.0, 5.9, and 5.8%, respectively. The first year, the average P content of winter wheat, spring wheat, barley, and oat straw was 0.02, 0.06, 0.15, and 0.07%, respectively; the second year, it was 0.05, 0.05, 0.09, and 0.06%, respectively.

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Prepubertal F1 heifers (n = 246; from crossbred dams bred to either Hereford [H], Limousin [L], or Piedmontese [P] sires) were fed 1.9% (LF) or 4.4% (HF) dietary fat from 254+/-4 d of age until they reached puberty or the breeding season started. Safflower seeds (37% oil with 79% linoleic acid) were the added fat source. Blood samples and backfat thickness measurements were obtained from 60 randomly selected heifers representing the sire breeds and diets studied. In addition, five H-sired heifers from both diets were serially bled at 28-d intervals. Total gain, ADG, body condition score, and backfat thickness were affected by sire breed (P < 0.001) but not diet. Backfat thickness was affected (P < 0.01) by the diet x time on feed interaction. Diet did not affect pubertal age (P > 0.10) but tended (P = 0.08) to affect the percentage of heifers pubertal by the beginning of breeding (June 4). Sire breed effects on puberty age at beginning of breeding, percentage pubertal at the beginning of breeding, and puberty age during the entire study were all highly significant. The effect of the diet x sire breed interaction on percentage of heifers pubertal at beginning of breeding (P < 0.05) was 74.4 vs 76.3% in H-sired, 69.8 vs 60.5% in L-sired, and 76.2 vs 97.6% in P-sired heifers (LF vs HF, respectively). Number of AI services per pregnancy and final pregnancy percentage were not affected by diet or the diet x sire breed interaction. Diet affected progesterone (P < 0.05) and cholesterol (P < 0.001) concentrations, and sire breed tended to affect (P = 0.06) cholesterol concentrations. The effect of the diet x time on feed interaction on cholesterol concentrations was highly significant. There were no effects of diet or sample period on insulin or growth hormone concentrations in serially collected blood samples. We conclude that effects of supplemental dietary fat may be breed-dependent and hypothesize that a feeding period of approximately 60 d duration may be more appropriate than the 162 d used in this study.

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