Phosphorylated mannans derived from the yeast cell wall of Saccharomyces cerevisiae may beneficially modulate immune function in the weanling pig, possibly providing an alternative to the use of dietary growth-promoting antibiotics. Therefore, in this study, 32 pigs averaging 19 d of age and 5.7 +/- 0.2 kg initial BW were randomly assigned to 16 pens in an environmentally controlled nursery to determine the effects of dietary supplementation with phosphorylated mannans on growth and immune function. Average daily gain and G:F ratio increased (P < 0.05) when pigs were fed diets supplemented with mannans from d 0 to 14 after weaning and in the overall experiment. Percentage of neutrophils was lower (P < 0.08) and percentage of lymphocytes was higher (P < 0.05) in blood from pigs fed mannans than when pigs were fed the basal diet. Lamina propria macrophages isolated from pigs fed diets containing mannans phagocytosed a greater (P < 0.05) number of sheep red blood cells (2.63 +/- 0.11) than did lamina propria macrophages isolated from pigs fed the basal diet (2.31 +/- 0.11). On d 19 after weaning, pigs fed diets supplemented with mannans tended to have a greater (P < 0.10) percentage of CD14+ lamina propria leukocytes than did pigs fed the basal diet. On d 21 following weaning, the percentage of CD14+MHCII+ leukocytes isolated from lamina propria tissue tended (P < 0.10) to be lower when pigs were fed mannans than when pigs were fed the basal diet. Pigs fed diets containing mannans had a lower (P < 0.05) ratio of CD3+CD4+:CD3+CD8+ T lymphocytes isolated from jejunal lamina propria tissue only on d 21 after weaning compared with pigs fed the basal diet. Supplementation of mannans in the diets of weanling pigs improved gain and efficiency, and intermittently affected selected components of the young pigs' immune function both systemically and enterically.

Holstein steer calves (n = 32; 156 +/- 33.2 kg average BW) were used to evaluate the duration of restraint and isolation stress (RIS) on endocrine and blood metabolite status and the incidence of dark-cutting LM. Calves were blocked by BW and assigned randomly within blocks to one of four stressor treatments: unstressed controls (NS) or a single bout of RIS for 2, 4, or 6 h. Venous blood was collected via indwelling jugular catheters at 40, 20, and 0 min before stressor application and at 20-min intervals during RIS. Unstressed calves remained in their home stanchions and, except for blood sampling, were subjected to minimal handling and stress. Serum cortisol and plasma lactate concentrations were increased (P < 0.01) during the first 20 min after RIS application, and remained elevated throughout the 6 h of RIS. Plasma concentrations of glucose and insulin were greater (P < 0.05) in RIS calves than in NS calves after 80 and 100 min of stressor application, respectively; however, RIS did not (P > 0.80) affect plasma NEFA concentrations. Calves were slaughtered within 20 min of completion of RIS, and muscle samples were excised from right-side LM at 0, 0.75, 1.5, 3, 6, 12, 24, and 48 h after exsanguination for quantifying LM pH, and glycogen and lactate concentrations. The pH of the LM from calves subjected to 6 h of RIS exceeded 6.0, and was greater (P < 0.05) at 24 and 48 h postmortem than the pH of NS calves or calves subjected to 2 or 4 h RIS. Muscle glycogen concentrations did not differ (P = 0.16; 25.58, 10.41, 13.80, and 14.41 micromol/g of wet tissue weight for NS and 2-, 4-, and 6-h RIS, respectively), and LM lactate concentrations tended to be lower (P = 0.08) in calves subjected to 6 h of RIS. At 48 h after exsanguination, the LM from calves subjected to 6 h of RIS had more (P < 0.05) bound and less (P < 0.05) free moisture than did the LM from NS calves or calves subjected to 2 or 4 h of RIS. Additionally, the LM from RIS calves was darker (lower L* values; P < 0.05) than the LM of NS calves. Visual color scores for the LM were greatest (P < 0.05) for calves subjected to 6 h of RIS and least (P < 0.05) for NS calves. Subjecting lightweight Holstein calves to 6, 4, and 2 h of RIS resulted in six (75%), two (25%), and two (25%) carcasses characteristic of the dark-cutting condition, respectively. There were no dark-cutting carcasses produced from NS calves. Thus, RIS may be a reliable animal model with which to study the formation of the dark-cutting condition.

Crossbred pigs, heterozygous for the halothane gene, were used to determine the effects of long-term dietary supplementation of magnesium mica (MM) and short-duration transportation stress on performance, stress response, postmortem metabolism, and pork quality. Pigs were blocked by weight, penned in groups (six pigs per pen), and pens (three pens per diet) were assigned randomly either to a control corn-soybean meal diet or the control diet supplemented with 2.5% MM (as-fed basis; supplemented at the expense of corn). Diets were fed during the early-finisher (0.95% lysine, as-fed basis; 43.7 to 68 kg) and late-finisher (0.85% lysine, as-fed basis; 68 to 103 kg) periods. At the conclusion of the 71-d feeding trial, 12 pigs from each dietary treatment were selected randomly and subjected either to no stress (NS) or 3 h of transportation stress (TS). Dietary MM had no effect (P > or = 0.40) on ADG or ADFI; however, G:F was improved (P < 0.05) during the early-finisher period when pigs were fed MM-supplemented diets. Plasma glucose concentrations were increased in TS pigs fed the control diet, but transportation did not affect plasma glucose in pigs fed 2.5% MM (diet x transportation stress; P = 0.02). Dietary MM did not affect blood lactate, cortisol, insulin, NEFA, Ca, or Mg concentrations in response to TS (diet x transportation stress; P > or = 0.13); however, circulating lactate, cortisol, and glucose concentrations increased in TS pigs (transportation stress x time; P < 0.01). The LM from TS pigs fed MM had higher initial (0-min) and 45-min pH values than the LM from NS pigs fed the control diet (diet x transportation stress x time; P = 0.07). Lactic acid concentration and glycolytic potential were greater in the LM of TS pigs fed MM than TS pigs fed control diets (diet x transportation stress; P < or = 0.01). Although some trends were identified, neither MM (P > or = 0.15) nor TS (P > or = 0.11) altered the color or water-holding capacity of the LM and semimembranosus. The transportation model elicited the expected changes in endocrine and blood metabolites, but dietary MM did not alter the stress response in pigs. Conversely, although pork quality traits were not improved by dietary MM, delaying postmortem glycolysis and elevating 0- and 45-min muscle pH by feeding finishing diets fortified with MM may benefit the pork industry by decreasing the incidence of PSE pork in pigs subjected to short-duration, routine stressors.

Inclusion of fish oil, a source of n-3 fatty acids, in ruminant diets may fortify the fatty acid composition of meats and alter consumer perceptions of taste. Therefore, a 70-d study of 16 crossbred steers (441 +/- 31.7 kg of initial BW; 4 steers/pen; 2 pens/dietary treatment) consuming a high concentrate diet was conducted. Dietary treatments consisted of 1) control (75% corn, 11% soybean meal, and 10% cottonseed hull-based diet) and 2) the control diet with 3% fish oil replacing a portion of the corn. Steers were weighed on consecutive days at d 0 and 70 (i.e., the beginning and end of the trial), and interim weights were taken on d 28 and 56. On d 63, all steers were bled by jugular venipuncture to determine plasma fatty acid profiles. Steers were stratified by treatment and slaughtered on d 71 and 72. Fish oil supplementation decreased ADFI (13.97 vs. 11.49 kg; P < 0.01); however, it had no effect on ADG (P = 0.20) or G:F (P = 0.27). Fish oil supplementation increased (P < 0.01) the concentrations of MUFA, as well as linolenic and eicosapentaenoic acid in the plasma. Fish oil supplementation did not alter (P > 0.24) the color of the LM, LM area, yield grade, dressing percent, marbling, quality grade, or fat thickness. However, after extended (15 mo) storage at -20 degrees C, a professional descriptor panel discerned steaks from steers that had been supplemented with fish oil from a commercially available product or steaks from control steers. In summary, supplementation with fish oil decreased feed intake and subsequent HCW (P = 0.06) and had varying effects on sensory traits. Nevertheless, fish oil supplementation increased the proportions of n-3 fatty acids in the plasma, which may increase acceptability of the meat to the beef consumer.

. Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. Effect of level of surface-spoiled silage on the nutritive value of corn silagebased rations AbstractTwelve ruminally cannulated crossbred steers were used to determine the effects of level of surface-spoiled silages on dry matter (DM) intake and nutrient digestibilities of corn silage-based rations. Irrigated corn was harvested at the 80% milkline stage of maturity and ensiled in 3-ft-deep, pilot-scale, bunker silos and a 9-ftdiameter AgBag®. After 90 days, the bunkers were sealed with a single sheet of polyethylene, and this silage was designated "spoiled". The silage in the AgBag was designated "normal". The four rations contained 90% silage and 10% supplement (DM basis). The silages in the rations were: A) 100% normal; B) 75% normal: 25% spoiled; C) 50% normal: 50% spoiled; and D) 25% normal: 75% spoiled. Dry matter intake decreased in a linear manner as the proportion of spoiled silage increased from 0 to 75%. Steers consuming the normal silage ration had higher DM, OM, CP, NDF, and ADF digestibilities than those fed the three rations that contained spoiled silage. The addition of spoiled silage also had negative associative effects on nutrient digestibilities, and the integrity of the forage mat in the rumen was destroyed partially by even the lowest level of surface spoilage. SummaryTwelve ruminally cannulated crossbred steers were used to determine the effects of level of surface-spoiled silages on dry matter (DM) intake and nutrient digestibilities of corn silage-based rations. Irrigated corn was harvested at the 80% milkline stage of maturity and ensiled in 3-ft-deep, pilot-scale, bunker silos and a 9-ft-diameter AgBag ® . After 90 days, the bunkers were sealed with a single sheet of polyethylene, and this silage was designated "spoiled". The silage in the AgBag was designated "normal". The four rations contained 90% silage and 10% supplement (DM basis). The silages in the rations were: A) 100% normal; B) 75% normal: 25% spoiled; C) 50% normal: 50% spoiled; and D) 25% normal: 75% spoiled. Dry matter intake decreased in a linear manner as the proportion of spoiled silage increased from 0 to 75%. Steers consuming the normal silage ration had higher DM, OM, CP, NDF, and ADF digestibilities than those fed the three rations that contained spoiled silage. The addition of spoiled silage also had negative associative effects on nutrient digestibilities, and the integrity of the forage mat in the rumen was destroyed partially by even the lowest level of surface spoilage.