Dietary protein level and ruminal degradability for mohair production in Angora goats.

Twenty-eight Angora goat doelings (average BW 22.1 kg) were used in a 150-d study to examine the effects of dietary CP level and degradability on mohair fiber production. A 2 x 2 factorial arrangement was instituted using conventional, solvent-extracted soybean meal (high degradability) or expelled, heat-treated soybean meal (low degradability) incorporated into low- (12%) or high- (19%) CP diets. Grease and clean mohair weights were greater (P less than .05) in goats fed the diets containing 19% CP. Mohair fiber diameter was not affected (P greater than .10) by dietary CP level. Clean mohair weight tended (P less than .08) to be higher in the goats fed diets containing expelled, heat-treated soybean meal. Body weight gains were not affected (P greater than .10) by CP level or degradability, whereas DMI increased (P less than .01) with increasing CP level. Ruminal fluid pH and total VFA concentrations were not affected (P greater than .10) by diet. Ruminal ammonia N concentration increased (P less than .05) as CP level in the diet increased, and postprandial changes in concentrations were less noticeable in the group fed expelled, heat-treated soybean meal. Plasma urea N (P less than .001) and total protein (P less than .01) concentration increased as dietary CP level increased. Plasma glucose was elevated (P less than .001) 2 h after feeding in the goats fed conventional, solvent-extracted soybean meal, whereas glucagon concentrations were greater at 0 and 4 h in the group fed expelled, heat-treated soybean meal.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of intraperitoneal administration of lysine and methionine on mohair yield and quality in Angora goats.

Eight mature Angora wethers (average BW 47.2 kg) were used in a 4 x 4 replicated Latin square design to evaluate responses to intraperitoneal (IP) administration of amino acids. The IP treatments consisted of saline (Control), methionine 1 g/d (Met), lysine 2 g/d (Lys), and methionine + lysine (Met + Lys). The amino acids dissolved in Control were infused continuously for the first 14 d of each 28-d period using peristaltic infusion pumps. Average d-28 grease and clean mohair yields (grams/100 square centimeters), and fiber diameter (micrometers) and length (centimeters) measurements during Control administration were 8.8, 7.6, 40, and 2.3, respectively. Mean clean mohair yield and fiber diameter increased by 5.3% (P less than .039) and 2.5% (P less than .067), respectively, with Met administration but were decreased by 9.2% (P less than .033) and 3.8% (P less than .001), respectively, by Lys administration; however, mean fiber length was increased (P less than .014) 21.7% by Lys infusion. The goats did not exhibit increased grease (P greater than .939) and clean (P greater than .477) mohair yields and fiber diameter (P greater than .619) when treated with Met+Lys. A N balance trial was conducted during d 10 through 14 of each period. Total retained N (grams per day) during Control administration was 18.4 and 24% greater than Met (P greater than .281) and Lys (P less than .061), respectively. When expressed as a proportion of N intake, retained N was lowest (P less than .127) in the Lys infusion group. Jugular blood ammonia N and plasma glucose and total protein concentrations were not affected (P greater than .10) by treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

山羊绒生长缓慢期日粮适宜氮硫比的综合评定

利用9只安装有永久性瘤胃瘘管和十二指肠瘘管的周岁二狼山型白绒山羊 ,于山羊绒生长缓慢期(1～2月)研究日粮不同硫含量((分别为0.15 %、0.23 %、0.27 %)以及氮硫比(分别为11.02 :1、7.40 :1、6.03 :1)对绒山羊氮代谢、硫代谢、营养物质消化率、消化道食糜流通量的影响。试验结果表明 :在山羊绒生长缓慢期 ,由日粮中添加无机硫调控氮硫比 ,氮硫比为7.40 :1组可消化氮、沉积氮、沉积氮/进食氮及氮的消化率均显著高于氮硫比为6.03 :1组(P<0.05),亦高于未添加硫组(N/S=11.02),但差异不显著(P>0.05);而沉积氮/可消化氮显著高于其它两组(P<0.05)。随着硫的添加 ,硫的沉积量显著提高 ,但利用率降低。OM、DM、ADF的消化率以氮硫比7.40 :1组高于另两组 ,6.03 :1组最低。饲喂不同氮硫比日粮 ,瘤胃和十二指肠总氮流量各组间无显著差异 ,总硫流量随硫的添加而提高。在绒生长缓慢期日粮中添加硫使ADF、CP、DM的瘤胃动态降解率降低。根据沉积氮、硫、DM、OM、ADF的消化率与日粮硫水平之间二次曲线关系得到绒生长缓慢期日粮适宜硫水平为0.213 % ,适宜氮硫比为7.80 :1。     

Effects of bovine somatotropin and ruminally undegraded protein on feed intake, live weight gain, and mohair production by yearling Angora wethers.

Yearling Angora wethers (n = 24; 24+/-1.0 kg BW) were used in an experiment with a 2 x 2 factorial arrangement of treatments to investigate effects of bovine somatotropin (bST) treatment and dietary level of ruminally undegraded protein on DMI, ADG, and mohair production. Untreated casein (UC) or casein treated with formaldehyde (TC) was included at 7% DM of a diet containing 11% CP and 46% concentrate. A slow-release bST form was administered weekly to deliver 0 (Control) or 100 microg/ (kg BW.d) of bST. Plasma concentrations of bST and IGF-I were increased (P < .05) during the 7-d period following bST injection. Ruminal fluid ammonia N concentration was lower (P < .01) for TC than for UC before feeding (6.6 vs 7.5 mg/dL) and 4 h later (8.2 vs 12.2 mg/dL), and total VFA concentration was lower (P < .01) for TC than for UC. Treatment with bST decreased (P = .08) DMI with UC (1.15 vs .91 kg/d) and increased (P = .08) DMI with TC (.95 vs 1.06 kg/d). Formaldehyde treatment of casein increased ADG (65, 74, 55, and 91 g/d; P = .03) and clean fleece production (P < .01; 14.1, 17.3, 15.0, and 18.4 g/d for UC-Control, TC-Control, UC-bST, and TC-bST, respectively), with no effect of bST during the 8-wk period of treatment or for the 8 wk thereafter (P > .10). In conclusion, with yearling Angora wethers, bST does not seem useful to enhance mohair production and may not alter effects of dietary level of ruminally undegradable protein on mohair production.     

Sulfate supplementation of alpine goats: effects on milk yield and composition, metabolites, nutrient digestibilities, and acid-base balance.

Effects of sulfate supplementation on milk yield and composition, ruminal and blood metabolites, acid-base status, and nutrient digestibilities were determined using 30 multiparous, lactating Alpine does. Goats were fed isonitrogenous diets containing .16 (basal), .26, or .36% S (DM basis) during a 13-wk lactation trial that coincided with wk 3 to 15 of lactation. During wk 16 to 17, four does from each treatment were placed in a metabolism crate to measure nutrient digestibility and balance. Feed intake, yield of 4% fat-corrected milk, and milk S content were not affected by added S, but the goats fed the .26% S diet had a trend of higher persistency of lactation (P < .20). During wk 10 and 15 of lactation, milk solids-not-fat percentage was higher (P < .10) for does fed the .26% S diet. Sulfur supplementation resulted in quadratic decreases in ruminal ammonia N (P < .05) in wk 15 and in plasma urea N in wk 10 and 15 (P < .05) but in linear increases (P < .05) in ruminal protein S concentrations throughout the experiment. Added S had little effect on blood acid-base status. Apparent digestibilities of DM, OM, ash, ADF, and GE were increased linearly (P < .10) by added S. The milk N:S ratio remained constant. Increasing S from .16 to .26% of diet DM was beneficial to lactating Alpine goats during early lactation.     

Effects of small peptides or amino acids infused to a perfused area of the skin of Angora goats on mohair growth

The effect of infusing dipeptides or their amino acids on mohair growth of Angora goats was investigated using a skin perfusion technique. Seven Angora wethers (average BW 24 +/- 2.5 kg) were implanted bilaterally with silicon catheters into the superficial branches of the deep circumflex iliac artery and vein and carotid artery. The experiment consisted of three 28-d phases. In the first 14 d of Phases 1 and 3, saline was infused into deep circumflex iliac arteries supplying skin and in Phase 2 a mixture of dipeptides (methionine-leucine [Met-Leu], lysine-leucine [Lys-Leu]) was infused into the artery on one side, and free amino acids were administered on the other side. Infusion rates of peptides were 0.85 mg/h Met-Leu and 0.85 mg/h Lys-Leu in 2.4 mL saline. Infusion rates of amino acids were 0.474 mg/h Lys, 0.483 mg/h Met, and 0.743 mg/h Leu in 2.4 mL saline. A 100-cm2 area within the perfused region was used to determine mohair growth. Two weeks after the cessation of infusions, perfused areas were shorn. Clean mohair production from the dipeptide- and amino acids-perfused regions were similar (4.21 vs 4.35 g/[100 cm2 +/- 28 d], respectively; P > 0.05). However, clean mohair production during dipeptides and amino acids infusions was greater (P < 0.01) than that observed during saline infusions (3.63 g/[100 cm2 +/- 28 d]). There were no significant differences between dipeptides and free amino acids in concentrations of various hormones and metabolites in blood from deep circumflex iliac veins (P > 0.05). In conclusion, the studied small dipeptides and amino acids similarly increased mohair fiber growth, presumably through supplying limiting amino acids directly to the fiber follicle.     

Carcass traits and retail display-life of chops from different goat breed types

Four groups of goats, Boer x Spanish, straightbred Spanish, Spanish x Angora, and straightbred Angora were slaughtered at a constant age according to accepted industry procedures. At 24 h postmortem, various carcass yield and quality measurements were taken. At 48 h postmortem, one side from each carcass was fabricated into major wholesale cuts for dissection into percentage lean, bone, and fat. Rib chops from the opposite side were fabricated, packaged, and displayed in a retail case. Trained panelists evaluated the rib chops over 4 d of retail display for lean color, surface discoloration, and overall appearance; packages were opened and analyzed for off-odor on d 4. When slaughtered at constant ages, Angora goats had lighter (P < .05) live and hot carcass weights than all other breed types, and Boer x Spanish goats had heavier (P < .05) live and carcass weights than Spanish goats. Live and carcass weights for Boer x Spanish and Spanish x Angora goats did not differ (P > .05). Carcasses from Angora goats had considerably smaller (P < .05) longissimus muscle areas than all other breed types. Carcasses from Spanish goats had lower (P < .05) carcass conformation scores than carcasses from Boer x Spanish goats but did not differ (P > .05) from carcasses of the other two breed types. Carcasses from Angora goats had smaller (P < .05) leg circumferences than the carcasses from Boer x Spanish and Spanish x Angora breed types. In general, carcasses from Boer x Spanish and Spanish goats possessed higher (P < .05) percentages of lean and lower (P < .05) percentages of fat for the side than did carcasses from Spanish x Angora and Angora goats. When the Spanish x Angora carcasses were compared to the Angora carcasses, it seemed that the addition of the Spanish breeding tended to increase lean and decrease fatness for most side or primal comparisons. There were no (P > .05) breed type or breed type x day effects for lean color, surface discoloration, overall appearance or off-odor; however, day of display did influence (P < .05) these traits. Crossing Spanish with Angora goats may be an option to improve carcass characteristics over that of straightbred Angora.     

Sulfur and nitrogen metabolism in the bovine fed different forms of supplemental sulfur

Twelve growing Angus heifers averaging 282 kg in weight were fed a tall fescue hay-based diet in a completely randomized design experiment to determine sulfur (S) and nitrogen (N) metabolism and bioavailability of different forms of supplemental S:elemental S (E), sodium sulfate (SU) and DL-methionine (M). The study included a 72-h adaptation phase that was followed immediately by a 5-d retention phase. Control (C) heifers were fed a ground fescue hay diet twice daily throughout the study. Supplementation with .15% S from E, SU or M to the basal diet began at h 0. Differences in total blood S, plasma S and ruminal NH3 N were dependent on sampling time in the 72-h adaptation phase. Urinary S excretion during 0 to 72 h was greater for S-supplemented calves than for C. Mean molar proportions of acetate, butyrate, isobutyrate and valerate were affected by form of S supplementation. No treatment differences (P greater than .10) were noted in total VFA concentrations. Sulfur supplementation increased daily urinary sulfate (P less than .01), total urinary S (P less than .01) and fecal S (P less than .01) excretion during the retention phase. Methionine and SU heifers had the greatest urinary S losses, and fecal S was highest for E (P less than .01). No differences (P greater than .10) in DM digestion occurred among treatments. N retention (g/d) and N retention as a percentage of intake averaged 5.9, 8.5; 13.2, 18.7; 13.8, 20.5; and 11.3, 19.2, respectively, for C, E, SU and M. Sulfur retention (g/d) was increased (P less than .10) by S supplementation. Sulfur supplementation of a basal fescue hay diet increased S retention transitorily, although much of the added S was lost through excretory routes. Supplementing S as E, SU or M appeared to be equally beneficial, despite differences in route and extent of S excretion among the three S sources.     

Effects of bovine somatotropin and thyroid hormone status on hormone levels, body weight gain, and mohair fiber growth of Angora goats.

Forty-eight Angora goats (24 wethers and 24 doelings; 5 mo old; 16 +/- 0.5 kg initial BW) were used in an experiment with a 2 x 3 factorial treatment arrangement (n = 8) to evaluate effects of recombinant bovine somatotropin (bST) administration and thyroid hormone status (euthyroid, hypothyroid, and hyperthyroid) on hormone levels, ADG, and mohair fiber growth. The bST was a slow-release zinc-based suspension, with sustained delivery (100 microg/[kg BW x d]) over a 14-d period. Hyperthyroidism was maintained by daily treatment with thyroxine (T4; 150 microg/[kg BW x d]), and hypothyroidism was achieved by feeding 6 mg/(kg BW x d) of propylthiouracil. The experiment was conducted in July to September and consisted of a 2-wk pretreatment period and 8 wk of bST treatment. Goats were given ad libitum access to a diet with 15% CP and 2.54 Mcal/ kg ME (DM basis). Concentrations of T4 and T3 were greatest (P < 0.01) among treatments for hyperthyroid-bST and hyperthyroid-control (T4: 38.6 and 38.0 microg/dL; T3: 406 and 385 ng/dL, respectively); similar among euthyroid-control, euthyroid-bST, and hypothyroid-bST (T4: 11.1, 11.5, and 9.8 microg/dL, respectively; T3: 232, 252, and 226 ng/dL, respectively); and lowest (P < 0.01) for hypothyroid-control (T4: 5.1 microg/dL; T3: 144 ng/dL). Plasma concentration of insulin-like growth factor-I was greatest (P < 0.01) for euthyroid-bST (596 ng/mL) and hypothyroid-bST (618 ng/mL); however, concentration for hyperthyroid-bST was similar to those for euthyroid-control, hypothyroid-control, and hyperthyroid-control (188, 178, 187, and 191 ng/mL, respectively). Dry matter intake was greatest (P < 0.05) for euthyroid-bST (794 g/d), similar among hypothyroid treatments (693 and 703 g/d for control and bST, respectively) and euthyroid-control (681 g/d), and lowest for hyperthyroid groups (554 and 518 g/d for control and bST, respectively); ADG for hyperthyroid goats (11 g/d) was lower than with hypothyroidism and euthyroidism (72 and 73 g/d, respectively); and mohair fiber growth was greater (P < 0.01) for hyperthyroidism (0.133 g/[100 cm2 x d]) than for hypothyroid and euthyroid goats (0.102 and 0.104 g/[100 cm2 x d], respectively). Hyperthyroidism also increased mohair length growth rate by 15% and decreased fiber diameter by 7.8% (P < 0.01). These results demonstrate interactions between growth hormone administration and thyroid hormone status, although these influences had limited effects on ADG and mohair fiber growth.     

Effects of field bean (Vicia faba L. var. minor) dietary supplementation on plasma thyroid hormones, insulin, insulin-like growth factor-1 concentrations and mohair characteristics in growing Angora goat kids

Twenty-two Angora kids were used to study the effect of a dietary supplementation with field bean (Vicia faba L. var. minor) on hair follicle activity, mohair characteristics and plasma total thyroxine (T4), triiodothyronine (T3), insulin (INS) and insulin-like growth factor-1 (IGF-1) concentrations. At birth, their mothers were divided in two groups (S: supplemented, C: control), the S group being supplemented with 300 g/head/day of whole field bean. At weaning, diet of kids from S group was supplemented with 80 g/head/day of whole field bean. At weaning, secondary hair follicle activity (S: 0.91 ± 0.01, C: 0.84 ± 0.02, p < 0.01) and staple length (S: 5.82 ± 0.13 cm, C: 5.16 ± 0.14 cm, p < 0.001) were greater in the S group. At 155 days of age, secondary fibre diameter (S: 16.54 ± 0.35 μm, C: 18.09 ± 0.31 μm, p < 0.01) was higher in the C kids. Concentrations of total plasma T4 and T3 were higher (p < 0.001) in S (120 ± 12 and 4.87 ± 0.92 ng/ml respectively) than in C kids (92 ± 8 and 2.97 ± 0.77 ng/ml respectively). At weaning, T4 values were negatively correlated (p < 0.05) with the secondary fibre diameter and the T3/T4 ratio was positively correlated (p < 0.05) with the secondary to primary hair follicle ratio. At 155 days of age, both T3 and T3/T4 values were positively correlated (p < 0.01) with staple length. Plasma INS (0.11 ± 0.03 ng/ml) and total IGF-1 concentrations (232 ± 13 ng/ml) were not affected by diet. Improvements of diet quality in kids positively affected fibre diameter and length and follicle activity rate. We suggest that increased circulating thyroid hormones concentrations, but not those of INS and IGF-1, may contribute to the beneficial actions of nutritional supplementation on anatomical growth and mohair production of kids.     

Effects of fiber and virginiamycin on nutrient absorption, nutrient retention and rate of passage in growing swine

Three balance trials, each involving 12 crossbred gilts averaging 35.2 kg body weight, were conducted to determine the effects of dietary fiber and virginiamycin on nutrient digestibility, mineral absorption and retention, and digesta rate of passage (RP). Two levels of fiber (13.5 and 20.2% neutral detergent fiber) and two levels of virginiamycin (0 and 11 ppm) were used in a 2 X 2 factorial arrangement of treatments. All diets were isonitrogenous and isocaloric. The RP was determined by observing the time required for a change in feces color after the addition of .5% chromic oxide to the diet. The high fiber diet had a faster (P less than .01) RP, which was associated with depressions (P less than .001) in the digestibility of dry matter (DM), energy (E), cell contents, neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose (HC), cellulose, permanganate lignin and ash. Virginiamycin supplementation slowed (P less than .004) the RP of both low and high fiber diets, but improved (P less than .05) the DM, E, NDF, ADF, HC and cellulose digestibility of the high fiber diet only. Fiber increased (P less than .06) fecal N excretion, whereas virginiamycin supplementation decreased (P less than .08) fecal N excretion. The addition of virginiamycin improved the absorption and retention of P, Ca, Mg, Cu, Fe, Zn and Mn when added to the high fiber diet, but had little or no effect when added to the low fiber diet even though absorption and retention values for most minerals were similar or slightly higher for the unsupplemented high fiber diet compared with the unsupplemented low fiber diet.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of corn vs corn gluten feed on site, extent and ruminal rate of forage digestion and on rate and efficiency of gain

Three digestion experiments and one growth experiment were conducted to determine site, extent and ruminal rate of forage digestion and rate and efficiency of gain by cattle offered alfalfa haylage supplemented with corn or dry corn gluten feed (CGF). In Exp. 1, eight steers were fed alfalfa haylage-based diets with substitution of corn for 0, 20, 40 or 60% of haylage in a 4 X 4 latin square. Increasing dietary corn substitution increased (P less than .05) OM, NDF and ADF digestion by steers but decreased (P less than .05) rate of in situ alfalfa DM digestion. In Exp. 2, five heifers were fed alfalfa haylage-based diets with increasing dietary levels of CGF in a 5 X 5 latin square. Increasing dietary CGF increased (P less than .05) OM, NDF and ADF digestion by heifers. In Exp. 3 and 4, cattle were fed alfalfa haylage-based diets containing either 20 or 60% corn or CGF. In Exp. 3, supplementation increased (P less than .05) OM and NDF digestion but level X supplement source interaction (P less than .05) occurred, with added CGF increasing OM and NDF digestion more than added corn. In Exp. 4, supplementation improved (P less than .05) DM intake, daily gain and feed efficiency. Dry matter intake and daily gain were greater (P less than .05) for 60% supplementation than for 20% supplementation. Overall, whereas increasing the level of dietary supplement increased (P less than .05) OM, NDF and ADF digestion, only corn addition decreased (P less than .05) rate of in situ alfalfa DM digestion. Daily gains and feed efficiencies were similar in cattle fed either corn or CGF with alfalfa haylage.     

Effects of dietary copper source and concentration on carcass characteristics and lipid and cholesterol metabolism in growing and finishing steers

We conducted an experiment to determine the effects of dietary copper (Cu) source and level on carcass characteristics, longissimus muscle fatty acid composition, and serum and muscle cholesterol concentrations in steers. Sixty Angus and Angus x Hereford steers were stratified by weight and initial liver Cu concentration within a breed and randomly assigned to treatments. Treatments consisted of: 1) control (no supplemental Cu); 2) 20 mg Cu/kg DM from Cu sulfate (CuSO4); 3) 40 mg Cu/kg DM from CuSO4; 4) 20 mg Cu/kg DM from Cu citrate; 5) 20 mg Cu/kg DM from Cu proteinate; and 6) 20 mg Cu/kg DM from tribasic Cu chloride. A corn silage-soybean meal-based diet was fed for 56 d. Steers were then switched to a high-concentrate diet. Equal numbers (n = 5) of steers per treatment were slaughtered after receiving the finishing diets for either 101 or 121 d. Serum cholesterol was not affected by treatment during the growing phase but was decreased (P < .05) in steers supplemented with Cu by d 84 of the finishing period and remained lower (P < . 05) at subsequent sampling periods. Longissimus muscle cholesterol concentration tended to be reduced (P < .11) by Cu supplementation. Hot carcass weight and backfat were lower (P < .05) in animals receiving supplemental Cu. However, Cu-supplemented and control steers had similar marbling scores. Longissimus muscle polyunsaturated fatty acid concentrations (18:2 and 18:3) were increased (P < .07) and saturated fatty acid concentrations tended (P < . 11) to be reduced by Cu supplementation. These results indicate that as little as 20 mg of supplemental Cu/kg diet can reduce backfat and serum cholesterol and increase muscle polyunsaturated fatty acids in steers fed high-concentrate diets.     

Soybean hulls as a dietary fiber source for dogs.

In Exp. 1, soybean hull samples were obtained from nine sources across the United States and analyzed for nutrient content to determine their suitability for inclusion in dog diets. Compositional data revealed variation in both the amount of total dietary fiber (TDF; 63.8 to 81.2%) in the soybean hulls and the ratio of insoluble:soluble fiber (5.0:1 to 15.4:1). Crude protein content varied widely among sources, ranging from 9.2 to 18.7%. An in vivo trial (Exp. 2) was conducted using a premium dog diet containing 3.0, 4.5, 6.0, 7.5, or 9.0% soybean hulls (DM basis). There was a negative linear effect (P < .05) of soybean hull inclusion in the diet on DM, OM, TDF, and GE total-tract digestibilities, as well as on calculated ME. Crude protein and fat digestibilities were unaffected by treatment. Based on these results, ileally cannulated dogs were fed diets containing 6.0, 7.5, or 9.0% soybean hulls (DM basis) in addition to diets containing either 0% supplemental fiber or 7.5% beet pulp (Exp. 3). Nutrient digestion at the ileum was unaffected by inclusion of supplemental fiber. Total tract digestion of DM, OM, and GE was lower ( P < .05) for diets containing supplemental fiber when compared with the diet containing 0% fiber. Crude protein and fat digestibilities were unaffected by treatment. There was no difference in nutrient digestibility between those diets containing soybean hulls and a diet containing beet pulp. Soybean hull inclusion in the diet resulted in a negative linear effect (P < .05) on calculated ME, in addition to lowering ME (P < .05) when compared with the 0% fiber control diet. Calculated ME for dogs fed a 7.5% beet pulp-containing diet was lower (P < .05) than that for dogs fed the soybean hull-containing diets. Results indicate that soybean hulls can be an effective dietary fiber source in dog diets.     

Effects of zinc sulfate concentration and feeding frequency on ruminal protozoal numbers, fermentation patterns and amino acid passage in steers

Effects of zinc sulfate (0 vs 1,142 ppm supplemental zinc from zinc sulfate) and feeding frequency (1 x vs 12x daily) on ruminal protozoa numbers, fermentation patterns and amino acid passage were investigated using four ruminally and abomasally cannulated mature Jersey steers in a 4 x 4 Latin square experiment. Steers (530 kg) were fed a 50:50 roughage:concentrate diet at 1.5 times their NEm requirement. Experimental periods were 14 d in duration; ruminal, abomasal and fecal samples were collected at 6-h intervals during the last 3 d of each period. Protozoa numbers tended to be lowest (1.82 x 10(6)/ml) in steers fed zinc 1 x and tended to be highest (3.83 x 10(6)/ml) in steers fed zinc 12 x daily (P less than .10). Frequent feeding decreased ruminal pH .24 units and increased total VFA 20.7%, ammonia 22.7% and ruminal digestion of dietary amino acids (AA) 61.6% (P less than .05). Zinc supplementation decreased ruminal digestion of dietary AA 35.8% (P less than .05) and the abomasal passage of bacterial OM and AA 21.2% (P less than .05) and increased ruminal output of amino acids as a percentage of intake 15.1% (P less than .05). Although it increased escape of dietary AA, zinc sulfate decreased postruminal passage of bacterial AA and resulted in a net negative effect on total postruminal AA passage as a percentage of intake. The effects of zinc on ruminal AA digestion may be more closely related to an interaction of zinc with dietary CP rather than to an effect of Zn on ruminal microbial populations.     

Dietary copper effects on lipid metabolism, performance, and ruminal fermentation in finishing steers

Sixty Angus steers (391.1+/-6.1 kg) were used to determine the effects of dietary Cu concentration on lipid metabolism and ruminal fermentation. Steers were stratified by weight and randomly assigned to treatments. Treatments consisted of 0 (control), 10, or 20 mg of supplemental Cu (as CuSO4)/kg diet DM. Steers were housed in pens equipped with individual electronic Calan gate feeders. On d 86 and 92, ruminal fluid was collected from two steers/treatment for IVDMD determination. Equal numbers of steers per treatment were slaughtered after receiving the finishing diets for 96 or 112 d. Gain, feed intake, feed efficiency, IVDMD, and ruminal VFA molar proportions were not affected by Cu supplementation. Copper supplementation increased (P < .05) liver Cu concentrations, and steers supplemented with 20 mg Cu/kg DM had higher (P < .05) liver Cu concentrations than steers supplemented with 10 mg Cu/kg DM. Serum total cholesterol concentrations were reduced by d 56 and at subsequent sampling dates in steers receiving supplemental Cu. Longissimus muscle cholesterol concentrations were lower (P < .10) in steers supplemented with Cu. Backfat depth was less (P < .05) in steers receiving supplemental Cu, but marbling scores were similar across treatments. Unsaturated fatty acid composition of longissimus muscle was increased (P < .05) and saturated fatty acid composition tended (P < .12) to be reduced in Cu-supplemented steers. Polyunsaturated fatty acid concentrations were higher (P < .05) in steers receiving Cu. These results indicate that addition of 10 or 20 mg Cu/kg to a high-concentrate diet containing 4.9 mg Cu/kg DM alters lipid and cholesterol metabolism in steers but does not affect ruminal fermentation.     

Effects of supplement sulfate (Dynamate) and thiamin-HCl on passage of thiamin to the duodenum and site of digestion in steers

Effects of dietary supplementation of thiamin-HCl (1 g daily) and a feed grade double sulfate of magnesium and potassium (Dynamate, added at 1.8% of diet dry matter; referred to as sulfate) on ruminal passage of thiamin and site of digestion in dairy steers (464 kg initial weight) fed a 77% concentrate diet were determined in a 4 X 4 Latin square experiment. Sulfate supplementation tended to reduce duodenal thiamin flow with (P less than .08) and without (P greater than .10) added thiamin. Supplementation with thiamin alone decreased ruminal disappearance of fed organic matter and nitrogen (P less than .03) and total tract disappearance of starch (P less than .06) and nitrogen (P less than .02), and increased ruminal microbial efficiency (P less than .04). Sulfate addition to the high thiamin diet alleviated these effects but depressed microbial efficiency (P less than .05). Sulfate included in the diet without added thiamin affected plasma thiamin positively, whereas sulfate added to the diet with supplemental thiamin changed plasma thiamin negatively (interaction, P less than .06). In conclusion, a marked depression of ruminal digestion induced by dietary thiamin-HCl supplementation disappeared upon dietary addition of sulfate and sulfate depressed the quantity of thiamin passing from the rumen. Because preventing thiamin deficiency and optimizing site of digestion in feedlot cattle are desired, these changes deserve further study.     

Effects of dietary protein-energy interrelationships on Holstein steer performance and ruminal bacterial fermentation in continuous culture.

In vivo and in vitro 3 x 2 factorial experiments were conducted concurrently to evaluate the incorporation of 0, 15, or 30% sugar beet pulp (SBP) as an energy source in diets fed to growing Holstein steers with either soybean meal (SBM) or alcohol-treated, defatted soybean flakes (ATSBF) as primary supplemental protein sources. Three groups of 42 Holstein steers each were fed six different diets from 54 kg initial BW to 320 kg in three experimental periods. There were no overall SBP level x protein source interactions (P greater than .05). Beet pulp level tended to decrease ADG (linear, P = .05) and increase feed/gain (linear, P less than .05) and DMI (quadratic, P less than .05). Each grower diet was used in a substrate for ruminal microbial metabolism in six dual-flow, continuous-culture fermenters. Organic matter and carbohydrate digestion were similar (P greater than .05) among diets. Increasing dietary levels of SBP caused a concomitant increase (P less than .05) in acetate and decrease (P less than .05) in butyrate and isobutyrate concentrations. Beet pulp level x protein source interactions (P less than .05) were observed for CP degradation, ammonia and nonammonia N, and dietary N flow. Crude protein degradation was higher (P less than .05) for the 0% SBP with SBM diet (81.3%) than for the 30% SBP with ATSBF diet (64.4%). Efficiency of bacterial synthesis was similar (P greater than .05) among diets. Results indicated that SBP is an effective dietary energy source for high-energy grower diets at 15 or 30% of the DM but may cause a decrease in some performance traits. There were no nutritional benefits of using ATSBF vs SBM as the supplemental N source.     

Interaction of dietary magnesium level on the feeding value of supplemental fat in finishing diets for feedlot steers

A feeding trial involving 160 crossbred steers (357 kg) and a metabolism trial involving eight Holstein steers (189 kg) cannulated in the rumen and proximal duodenum were conducted to evaluate the interaction of dietary Mg level (.18 vs .32%, DM basis) and supplemental fat (0% supplemental fat vs 4% tallow [T], yellow grease [YG], or griddle grease [GG]) on growth performance and NE value of the diet. Dietary Mg level did not influence (P > .10) growth performance. Daily weight gain was lower (11%, P < .05) for steers fed GG than for those fed YG. Supplemental fat decreased (5%, P < .10) DMI and increased (P < .05) gain efficiency (7%). There was a fat x Mg level interaction (P < .01) for dietary NE. The increase in dietary NEg with T and YG supplementation was similar (8.6 vs 8.0%) for diets containing .18 and .32% Mg. In contrast, the increase in dietary NEg with GG supplementation was 8.9% with .18% dietary Mg, but the NEg value of the diet did not increase when GG was added to diets with .32% dietary Mg. Dressing percentage was lower (1.5%, P < .1) and retail yield was greater (2.2%, P < .05) for steers fed GG- than for steers fed YG-supplemented diets. Increasing dietary Mg level increased kidney, pelvic, and heart fat (5.5%, P < .05). There was a fat x Mg level interaction (P < .1) for marbling score. With diets containing no supplemental fat, increasing dietary Mg decreased (15.2%) the marbling score, and with diets containing supplemental fat, increasing dietary Mg increased (7.2%) the marbling score. Fat supplementation decreased (P < .01) ruminal and total tract digestion of OM (10 and 3.5%, respectively) and NDF (37 and 17%, respectively). Supplemental fat did not affect (P > .10) Ca digestion but decreased (41.7%, P < .01) apparent Mg digestion. Increasing dietary Mg level increased (77.7%, P < .05) apparent Mg digestion. There were no treatment effects (P > .10) on postruminal fatty acid digestion. Fat supplementation decreased (17.3%, P < .01) the acetate:propionate molar ratio. Total ruminal protozoal counts were increased (12.7%, P < .05) by increasing dietary Mg level and decreased (12.9%, P < .05) by fat supplementation. We conclude that supplemental fats may depress Mg absorption. Increasing dietary magnesium levels beyond current recommendations may increase marbling scores in cattle fed fat-supplemented diets but may not affect growth performance or dietary NE. The NE value of fat is a predictable function of level of fat intake.     

Effects of mimosine and 2,3-dihydroxypyridine on fiber shedding in Angora goats.

The effects of intravenous infusion of mimosine or 2,3-dihydroxypyridine (2,3-DHP) and the effects of oral dose level of mimosine on fiber shedding in Angora goats were determined. In one experiment, 20 mature Angora wethers (36+/-1.9 kg BW) were infused for 2 d with 79, 102, or 135 mg/(kg BW.d) of mimosine, 90 mg/(kg BW.d) of 2,3-DHP, or saline. At 7 d after infusion began, fiber shedding was observed in all goats receiving mimosine but not in any goats infused with 2,3-DHP or saline. Fiber shedding varied among goats; in some goats, fiber shedding was complete and occurred without hand-plucking, whereas in others fiber was retained by nonshed fibers but could be removed by hand-plucking. Nonshed fibers were larger in diameter and more likely to be medullated (P < .05) compared with hand-plucked fibers. Mean plasma mimosine concentration at 24 and 48 h after infusion began was 79 and 98 micromol/L (P < .05), respectively, and greater (P < .05) for mimosine infused at 135 than at 102 mg/(kg BW.d) (89, 68, and 108 micromol/L for mimosine infused at 79, 102, and 135 mg/[kg BW.d], respectively; SE 9.5). In another experiment, oral dosing of eight Angora bucks (23+/-.5 kg BW) with 400 or 600 mg/kg BW of mimosine rapidly increased plasma mimosine concentration, which reached approximately 100 and 160 micromol/L at 5 h after dosing; however, periods of time during which plasma mimosine concentrations were comparable to those in the first experiment were considerably shorter. Oral mimosine dosing did not induce fiber shedding in 7 d. After 31 d, fiber was retained by nonshed fibers but could be removed by hand-plucking or could only be partially removed with difficulty by hand-plucking. There were no toxic effects of mimosine or 2,3-DHP administration; only minor, short-term inhibitions of feed intake by mimosine were noted in some goats. In conclusion, mimosine holds promise as a safe means to remove fiber of Angora goats; further research is necessary to characterize the seasonality of follicle activity and to develop convenient means of mimosine delivery.