Effects of implanting ram and wether lambs with zeranol at birth and weaning on palatability and muscle collagen characteristics.

Thirty-five zeranol-implanted (I) and nonimplanted (NI) ram and wether lambs representing four treatments (implanted rams [IR], nonimplanted rams [NIR], implanted wethers [IW], and nonimplanted wethers [NIW]) were evaluated for meat palatability and muscle collagen characteristics. Rib (longissimus muscle, LM) chops from I lambs were juicier (P less than .05) than rib chops from NI lambs. Chops from IR lambs had more (P less than .05) detectable connective tissue and lower myofibrillar and overall tenderness scores than chops from NIR, IW, or NIW lambs. Warner-Bratzler shear (WBS) values tended to be higher (P = .06) for LM chops from rams than for those from wethers, but WBS values for Biceps femoris (BF) chops were similar (P greater than .05) for rams and wethers. Implanting did not affect (P greater than .05) WBS values. Rams had more (P less than .05) LM heat-labile (soluble, SC), nonheat-labile (insoluble, IC), and total collagen (TC) and a higher (P less than .05) percentage of SC (SC/TC) than did wethers. Soluble collagen, TC, and percentage of SC for the BF were higher (P less than .05) and IC tended (P = .09) to be higher in chops from rams than in those from wethers. Implanting did not affect (P greater than .05) collagen amount or solubility. Serum nonprotein hydroxyproline (NPHP) was higher (P less than .05) in rams than in wethers throughout the feeding period and tended (P = .05) to be higher at slaughter. Implanting did not affect (P greater than .05) serum NPHP.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of aluminum citrate and citric acid on mineral metabolism in wether sheep

A 60-d trial was conducted to determine effects of Al citrate and citric acid on DM digestibility (DMD) and metabolism of Mg, Ca, P, K, Na and Al. Eighteen crossbred, yearling wether lambs equipped with ruminal cannulas were fed a basal diet containing .12% Mg and 2.87% K (DM basis) and were allotted to three treatments: 1) control, 2) 2,000 ppm Al as Al citrate and 3) citric acid equivalent to the citrate in treatment 2. Treatments were administered in 200 ml of deionized water twice daily in divided doses via ruminal cannula. Balance trials were conducted during d 0 to 5, 6 to 10, 25 to 35 and 50 to 60. Dry matter digestibility decreased (P less than .05) approximately 3 percentage units in lambs receiving Al. Treatment with Al citrate increased (P less than .01) apparent absorption and retention of Al compared to those receiving citric acid alone. Approximately 30% of ingested and infused Al was apparently absorbed. Compared to citric acid, Al citrate treatment lowered apparent absorption and retention of Mg and Ca during d 0 to 5. Apparent Ca absorption and retention again were lowered during d 50 to 60. Urinary Ca was increased (P less than .01) and apparent P absorption (P less than .10) and retention (P less than .05) were decreased by Al citrate during all measurement periods. Apparent absorption of K decreased (P less than .05) slightly in response to Al treatment. Apparent absorption of Na was not influenced by Al treatment. Serum Mg and P decreased and serum Ca increased in response to Al treatment. Results demonstrate negative effects of ingested Al, but not of citric acid, on DMD and metabolism of Mg, Ca, P and K.     

Utilization of magnesium and other macrominerals in sheep supplemented with different readily-fermentable carbohydrates

Sheep were used to determine the effects of dietary supplementation with readily-fermentable carbohydrates on Mg, Ca, K and P utilization. In each of two metabolism trials, 15 mature, crossbred wethers (average weight, 49.2 kg) were allotted to five dietary treatments consisting of 800 g/d of orchardgrass (Dactylis glomerata, L.) hay alone, or supplemented with 450 g/d of either glucose, sucrose, lactose or starch. Each trial consisted of a 5-d adjustment period, a 10-d preliminary period and a 10-d collection period. Compared with wethers fed hay alone, supplementation with each kind of carbohydrate to the diet decreased (P less than .05) fecal Mg excretion and increased (P less than .05) apparent absorption and retention of Mg. Apparent absorption of the Ca was lower (P less than .05) in wethers fed lactose and tended to be decreased by glucose, sucrose and starch supplementation. Calcium retention was lower (P less than .05) in wethers fed sucrose and lactose, compared with those fed hay alone. All types of supplementary carbohydrates depressed (P less than .05) apparent absorption and urinary excretion of K. Serum Mg and Ca were not affected and serum K was depressed (P less than .05) by carbohydrate supplementation. Ruminal fluid pH was decreased (P less than .05) by glucose and lactose supplementation, and addition of these carbohydrates tended to decrease molar proportions of acetate and increase those of propionate and butyrate, compared with sheep fed hay alone. Sucrose addition decreased (P less than .05) acetate and increased (P less than .05) butyrate molar proportions in the ruminal fluid.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of age, castration, and season on difficulty of pelt removal in lambs

Sixty-four white-faced rams and wethers were dressed with the aid of a commercial pelt puller. The effects of age, castration, and season on difficulty of pelt removal and pelt damage were evaluated. Lambs were divided into two age groups (5 and 12 mo) within gender (ram and whether) and season (spring and fall). A greater force (P less than .05) was required to remove pelts from rams than from wethers in both 5- and 12-mo-old groups. Older lambs slaughtered in the fall required more force (P less than .05) to remove their pelts than did those slaughtered in the spring, but differences by season did not exist for 5-mo-old lambs. The difference between rams and wethers in percentage of live weight that was closely shorn pelt weight was not significant (P greater than .05). The area of grain crack in the flank expressed as a percentage of total area of the skin was lower (P less than .05) for skins from 5-mo-old lambs and ram lambs than it was for skins from 12-mo-old lambs and wether lambs, respectively. Factors involved in difficulty of pelt removal in ram lambs included crosscut shoulder weight, fat firmness, and carcass weight. Difficulty of pelt removal in wether lambs was best predicted by including crosscut shoulder weight and bodywall thickness in multiple regression equations.     

Comparative digestion, rumen fermentation and kinetics of forage diets by steers and wethers

Four rumen fistulated wether and beef steers were used to evaluate differences in dry matter digestibility (DMD) between cattle and sheep. They were fed either perennial ryegrass or switchgrass hay at an ad libitum or restricted level for four experimental periods. Significant ruminant species X forage and ruminant species X level of intake (P less than .05) interactions were observed for digestible dry matter. The steers digested the switchgrass 7 percentage units greater than the wethers while ryegrass was digested equally. Digestibility differences between the steers and wethers were 6 percentage units at the ad libitum level of intake and 1 unit at the restricted level of intake. Crude protein digestibility tended to be greater (P less than .10) for sheep with a 7 unit difference for switchgrass and a 3 unit difference for ryegrass. The mean ruminal solids retention time of the digesta was approximately (P less than .01) 50% greater (26.0 vs 17.4 h) in cattle, with no difference in ruminal liquid dilution rate (LD) between animal species. Total ruminal volatile fatty acid concentration differed (P less than .01) with level of intake; however, no influence due to intake on the molar proportion of acetate (P greater than .10) or propionate (P greater than .10) was evident in spite of a difference (P less than .01) in LD. Rumen pH (P less than .05) and osmolality (P less than .01) were affected by both level of intake and forage, with the ryegrass and high level of intake decreasing pH and increasing osmolality.(ABSTRACT TRUNCATED AT 250 WORDS)     

The role of glucose infusion on the metabolism of nitrogen in ruminants

This work determined the time necessary to stabilize the decrease in urinary N excretion after initiating continuous i.v. glucose infusion and the quantity of glucose required to maximize N balance in growing wether lambs fed a high-protein diet (21.1% CP, DM basis). In the first experiment, six wethers (30 kg) were used in a 10-d crossover design comparing jugular infusion of glucose (600 kcal gross energy/d) plus saline with saline alone. The second infusion experiment was carried out with six wethers (31 kg) assigned to two 3 x 3 plus extra period latin squares, with glucose infusion rates of 0, 300 and 600, and 0, 450 and 900 kcal/d, respectively. Urinary N decreased (P less than .02) by d 2 of glucose infusion, remained stable to the end of the 10-d infusion period, and returned to the preinfusion level within 2 d after glucose infusion was discontinued. Urinary N decreased (P less than .01) and N balance increased (P less than .005) with an increasing level of glucose infusion through 600 kcal/d. Plasma glucose and insulin were elevated (P less than .05) only by infusion of 900 kcal/d of glucose. Glucose was present in the urine of wethers infused with 900 kcal/d of glucose. Glucose infusion had no effect on diet digestibility, hematocrit or plasma urea N. The level of glucose infused into growing wether lambs that maximized reduction of urinary N and was fully utilized for protein deposition without increasing plasma glucose and insulin was about 12 g.Wk-.75.d-1.     

Effects of deficient and adequate dietary magnesium concentrations on body magnesium concentrations in wethers

Effects of 2 dietary Mg concentrations (deficient and adequate: 0.04 and 0.12 g of Mg/100 g of dry matter, respectively) on body fluid and tissue Mg concentrations and performance of wether lambs were evaluated in a 28-day trial. Nine blood and 6 urine samples were collected from each wether. After 28 days, CSF and wool samples were collected, and diet, body fluids, and tissues were analyzed for mineral concentration. Diet effects on serum and urine Mg concentrations were noticed after day 3 (P less than 0.01; P less than 0.05, respectively). Mean serum and urine Mg concentrations for 6 sampling periods were correlated (r = 0.83, P less than 0.001; No. of samples = 12). The effect of dietary Mg on CSF Mg concentrations approached significance (P less than 0.10). Effects of diet on cardiac muscle, liver, and 3rd metatarsal bone Mg contents or hematologic criteria were not observed. Diet affected wool and kidney cortex Mg contents (P less than 0.02). Individual mean 28-day serum Mg concentration was correlated with wool Mg content (r = 0.73, P less than 0.05; n = 8) and with kidney cortex Mg content (r = 0.75, P less than 0.05; n = 8). Wethers fed low Mg diet excreted less urine Ca (P less than 0.001) and had slightly lower serum Ca and K values (P less than 0.10) than did wethers fed high Mg. Significant differences in cardiac muscle, liver, spleen, or kidney cortex Ca contents were not observed. Wethers fed low Mg diet consumed less dry matter and gained less weight (P less than 0.001) than did wethers fed high Mg diet. Body fluid and tissue macromineral concentrations of 1 wether with hypomagnesemic tetany are presented for prognostic and diagnostic purposes.     

Intramuscular collagen and serum hydroxyproline as related to implanted testosterone, dihydrotestosterone and estradiol-17 beta in growing wethers

Relationships of implanted testosterone, dihydrotestosterone and estradiol-17 beta to collagen degradation and intramuscular collagen concentration and stability were determined. Intramuscular collagen content, solubility and shrinkage temperature and serum hydroxyproline were analyzed in groups of six rams, wethers, and wethers implanted with various levels of testosterone or dihydrotestosterone and groups of 10 rams, wethers and wethers implanted with estradiol-17 beta, dihydrotestosterone or a combination of these two steroids. Intramuscular collagen content in both experiments was higher (P less than .05) in muscles of rams than in muscles of wethers. Administration of the highest level of testosterone to wethers raised (P less than .05) total and insoluble intramuscular collagen to concentrations noted in rams. Administration of the testosterone metabolite, dihydrotestosterone, to wethers had no effect on intramuscular collagen. Administration of estradiol-17 beta to wethers tended to raise concentrations of intramuscular collagen so that they were no longer lower (P less than .05) than those in rams. Collagen stability as measured by solubility and thermal shrinkage temperature did not differ among rams, wethers or implanted wethers (P greater than .05). Increases in collagen accretion due to hormone administration were observed to be the result of increases in the insoluble portion of the intramuscular collagen (P less than .05).     

Effects of induced fescue toxicosis on plasma and tissue catecholamine concentrations in sheep

Sixteen crossbred wethers were distributed among four treatments and fed a control ration based on annual rye-orchardgrass (R-O) for 8 days. Indwelling jugular cannulae were installed and experimental regimes begun the following day (experimental day 1). One-half of the wethers were fed a ration based on endophyte-infected Kentucky-31 fescue while the remainder continued to receive the R-O control diet for 10 days. Spiperone, a dopamine antogonist, was administered to one-half of the wethers receiving each ration on days 8 and 9. Plasma prolactin (PRL), dopamine (DA), norepinephrine (NE) and epinephrine (E) were measured in jugular venous blood on days 1, 3, 5 and 7-10 of the trial. On day 10, the animals were decapitated; and DA, NE, E and 3,4-dihydroxyphenylacetic acid (DOPAC) and monoamine oxidase (MAO) were determined in hypothalamic and pituitary tissue. Plasma DA was elevated (P less than .05) following day 8 in wethers fed infected fescue over those fed (R-O), while plasma PRL was reduced (P = .08). Wethers receiving Spiperone had lowered (P less than .05) plasma DA and elevated (P less than .01) plasma PRL. Plasma DA was negatively correlated (P less than .01) with plasma PRL (r = -0.50) following day 8. Plasma NE and E levels and NE, E, DA and DOPAC tissue concentrations were not affected by Spiperone administration or diet. MAO levels in pituitaries were higher (P less than .01) for Spiperone-treated wethers. Wethers receiving the toxic fescue ration exhibited elevated plasma DA concentrations which was associated with depressed prolactin secretion in wethers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bone ossification and carcass characteristics of wethers given silastic implants containing estradiol

Administration of growth promotants with estrogenic activity via hastening closure of the growth plate could have an economic impact on lambs because closure results in ovine carcasses being classified as yearlings. Twelve wether lambs approximately 12 mo old were given silastic implants filled with estradiol-17 beta and allotted randomly to be slaughtered 30, 60, 90, or 220 d after implantation to determine time of growth plate closure in relation to date of implanting. Seven comparable wethers not implanted served as controls. Four wethers implanted at 2 mo of age and slaughtered 220 d later also were included. Implanted wethers had serum concentrations of estradiol averaging 13.9 pg/ml over the 220-d implant period; controls averaged 2.7 pg/ml. Estradiol implants increased carcass maturity scores but fat deposition was not altered. Growth plate widths decreased (P less than .05) as wethers grew older and implants were in place for longer periods of time. Metacarpal growth plates in 12-mo-old lambs were completely ossified 220 d after implanting, but control wethers and wethers implanted at 2 mo maintained growth plate widths. Neither metacarpal nor metatarsal bone lengths differed (P less than .05) between control and implanted wethers. Growth plate ossification was not complete until 570 d of age in implanted lambs, even though bone length had stopped increasing by 408 d. Therefore, even though estradiol and other growth stimulants with estrogenic activity increase rate of ossification of the metacarpal growth plate, bone length or mature size is not limited.(ABSTRACT TRUNCATED AT 250 WORDS)     

Factors influencing difficulty of removing pelts from lamb carcasses.

Forty-eight Suffolk x white-faced ram and wether lambs approximately 5, 7, or 9 mo of age were slaughtered to evaluate the effects of age and gender on difficulty of pelt removal, pelt damage, and leg damage. A commercial belt-type pelt puller and a scale that recorded force required to remove the pelt from the thickest part of the legs was used as lambs hung suspended from their front legs. Rams required more force (P less than .05) to remove the pelt than wethers, and the difference between genders became larger as age increased. Neither pelt damage due to grain crack nor leg damage judged by amount of fell and fat removed by the pelt puller changed with age. Rams possessed thicker pelts (P less than .05) than wethers; this plus a greater amount of collagen crosslinking in ram skins could be responsible for the slightly smaller amount of grain crack observed in ram pelts. Factors involved in difficulty of pelt removal in ram lambs included age, splenius weight, and overall maturity. Difficulty of pelt removal in wether lambs was best predicted by including age and splenius weight in the model. These data tend to support packers' common practice of discounting rams over 5 mo of age because rams develop masculine characteristics and become harder to dress with increasing age.     

Potassium and lasalocid effects on performance and digestion in lambs

Two trials were conducted to evaluate effects of dietary potassium (K) concentration and lasalocid (L) in lamb finishing diets. Treatments were arranged in a 2 X 2 factorial and consisted of a 65% concentrate diet with 1.1% K (C), .9% K + 21.3 mg L/kg (CL), 2.1% K (P) and 2.5% K + 20 mg L/kg (PL). In trial 1, 64 fine-wool lambs (initial wt 35.3 kg) were randomly assigned to the four treatments (two pens of four wethers and four ewes/treatment) for a 56-d feeding trial. Average daily gain was not affected by K, but was increased (P less than .10) by L (.23 vs .26 kg/d). Lasalocid tended (P less than .20) to improve feed:gain ratio (5.6 vs 6.3). A K X L interaction (P less than .06) was noted for feed intake, with values of 1.37, 1.45, 1.49 and 1.51 kg X head-1 X d-1 for the C, CL, P and PL groups, respectively. In trial 2, 16 wether lambs (four/treatment fed at 2% of body weight) were used in a site and extent of digestion and nitrogen (N) balance trial, using the same four diets as in trial 1. Site of digestion was estimated from abomasal samples taken at slaughter, with indigestible acid detergent fiber as a marker. Total tract organic matter digestibility was increased (P less than .05) with added K (80.1 vs 76.4%) and L (80 vs 76.4%). Ruminal starch digestibility was not affected by added K, but was decreased (P less than .10) by added L (71.8 vs 88.2%).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of zeranol implants in ram and wether lambs on performance traits, carcass characteristics, and subprimal cut yields and distribution.

In two separate 2 x 2 factorial arrangements, 69 male, crossbred lambs were allotted randomly to the following treatments: 1) nonimplanted (NI) rams, 2) implanted (I) rams, 3) NI wethers, and 4) I wethers. In Trial 1, 36 lambs were allotted to treatment groups at birth (n = 9) and I lambs were implanted with 12 mg of zeranol between 1 and 3 d of age and again at weaning (average age of 62 d). Lambs were slaughtered at three time-constant end points of 78, 93, and 107 d on feed postweaning (average age of 155 d). Rams grew faster postweaning, were more efficient in their feed conversion, were heavier at slaughter, and had lower numerical yield grades than did wethers (P less than .05). Implanted lambs tended (P = .08) to grow faster and were (P less than .05) more efficient in their feed conversion than NI lambs. Rams produced heavier (P less than .05) trimmed subprimal shoulders, loins, and legs and had (P less than .05) a higher percentage of their carcass weight in the subprimal shoulder than did wethers. During Trial 2, NI rams (n = 8), I rams (n = 8), NI wethers (n = 8), and I wethers (n = 9) were allotted to treatment groups, and I lambs were implanted at average ages of 14, 55, and 98 d. After weaning, lambs were weighed every 14 d and were slaughtered 7 d after reaching a minimum weight of 50 kg (average age of 148 d).(ABSTRACT TRUNCATED AT 250 WORDS)     

Palatability of wethers fed an 80% barley diet processed at different ages and of yearling wethers grazed on native range

Seasonal availability of lamb in the Western United States contributes to a large fluctuation in lamb supply and value. However, alternatives to fall marketing may not be practical unless palatability traits are acceptable. A 3-yr study was conducted to investigate 1) the effects of slaughter age (7 to 8; 10 to 11; or 14 to 15 mo) on carcass and palatability characteristics of wethers fed an 80% barley diet (Exp. 1); and 2) the effects of finishing on range or on an 80% barley diet on carcass and palatability traits of 14- to 15-mo-old wethers (Exp. 2). In Exp. 1, no differences (P = .27) were detected in flavor intensity or longissimus muscle area among slaughter age groups, but fat depth was greater (P < .05) for 7- to 8-mo-old wethers than for 10- to 11- or 14- to 15-mo-old wethers. Year x slaughter age interactions were detected (P < .10) for hot carcass weight, Warner-Bratzler shear value, body wall thickness, and percentage kidney fat. Hot carcass weight was greater (P < .05) for 14- to 15-mo-old wethers than for both groups of younger wethers in yr 1, did not differ (P = .53) among slaughter ages in yr 2, and was greater (P < .05) for 10- to 11- than for 14- to 15-mo-old wethers in yr 3. Warner-Bratzler shear values did not differ (P > .10) among slaughter ages in yr 1 and 3, but shear values for 14- to 15-mo-old wethers were greater (P < .05) than for both younger slaughter age groups in yr 2. Percentage kidney fat was lower (P < .05) for 14- to 15- than for 7- to 8-mo-old wethers in all years. In Exp. 2, flavor intensity of the meat did not differ (P = .35) between finishing systems, but longissimus muscle area was greater (P = .02) for range-finished wethers than for wethers fed an 80% barley diet. Year x finishing treatment interactions were detected (P < .10) for shear values, body wall thickness, percentage kidney fat, and fat depth. Shear values were greater (P = .10) for range-finished wethers than for wethers fed an 80% barley diet in yr 1, but did not differ (P > .55) in yr 2 and 3. Body wall and fat measurements were greater (P < .10) for wethers fed an 80% barley diet than for range-finished wethers in all years except yr 3, when fat depth did not differ (P = .47). Overall, slaughtering wethers fed an 80% barley diet or range-finished wethers at older ages produced acceptable carcasses with desirable meat palatability traits.     

Effect of feeding frequency on forage fiber and nitrogen utilization in sheep

Four crossbred wether lambs (38 kg) with permanent ruminal and abomasal cannulae were used in a 4 X 4 Latin square arrangement of treatments to determine the effect of feeding frequency (FF) on forage fiber and N utilization. Lambs were offered 900 g of good quality (vegetative) Kentucky-31 tall fescue hay in equal portions either 2, 4, 8 or 16 times daily. Water consumption increased (P less than .05; linear) with increased FF. Apparent total tract digestibilities of dry matter, organic matter and cell wall constituents were not affected (P greater than .05) by FF, but apparent total tract digestibility of crude protein decreased (P less than .05; linear) with increased FF. Ruminal and post-ruminal digestion of acid detergent fiber (percent of total tract digestion) differed (P less than .05; cubic) among FF treatments. Although N retention was not affected (P greater than .05) by FF, increased FF decreased (P less than .05; linear) mean ruminal ammonia-N concentrations. Both the quantity of total N reaching the abomasum and the efficiency of microbial crude protein synthesis tended to increase (P greater than .05) with increased FF. In addition, the daily quantity of microbial N reaching the abomasum was affected (P less than .05; cubic) by FF. Ruminal pH was not affected (P greater than .05) by FF, whereas total volatile fatty acid concentrations (VFA) decreased (P less than .05; linear) with increased FF. Responses in molar proportions of individual VFA to FF were variable, and suggest that increasing FF elicits significant changes in the distribution of fermentation end-products.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of bentonite on wool growth and nitrogen metabolism in fauna-free and faunated sheep.

Two experiments were carried out with sheep that originated from a fauna-free flock and were fed a soybean meal-corn silage diet with or without a bentonite supplement. One-half of the sheep fed each diet in each experiment were faunated with a mixed population of ruminal protozoa, whereas the other half of the sheep remained fauna-free until the end of both experiments. Wool growth and daily gain were measured in Exp. 1. (eight rams per treatment), which lasted 110 d, and the metabolic effects in the rumen and intestinal tract of protozoa and dietary bentonite supplement were tested with cannulated wethers (four wethers per treatment) in Exp. 2. The results of Exp. 1 showed decreased wool growth (P less than .05) due to the presence of protozoa in the rumen. Dietary supplementation with bentonite partly offset the decreased wool growth in sheep with protozoa, but there were no effects of dietary bentonite and no protozoa x bentonite interaction (P greater than .05). Daily gain was decreased by the dietary bentonite (P less than .05) supplement but was not affected (P greater than .05) by the ruminal presence of protozoa. In Exp. 2, protozoa increased (P less than .01) the ruminal concentrations of ammonia and decreased (P less than .05) the acetic:propionic acid molar ratio. Fractionation of N in the duodenal digesta flowing from the stomach to the small intestine showed that protozoa decreased (P less than .05) the flow of nonammonia N and bacterial N, and there was a protozoa x bentonite interaction for these effects (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Relationships among intramuscular collagen, serum hydroxyproline and serum testosterone in growing rams and wethers

Concentration and maturation of collagen and serum concentrations of hydroxyproline and testosterone were determined in growing rams and wethers to characterize developmental changes in collagen associated with a representative testicular steroid. Groups of eight rams and eight wethers were slaughtered at 12, 18, 24 and 30 wk of age. Concentrations of collagen in longissimus, supraspinatus and infraspinatus muscles and serum hydroxyproline were greater (P less than .05) in rams than in wethers at all ages. Collagen stability, as measured by collagen solubility and thermal shrinkage temperature, was greater (P less than .05) in wethers than in rams. Differences in collagen stability and serum hydroxyproline concentration indicated that collagen synthesis and turnover were more rapid in rams than in wethers. Serum hydroxyproline decreased (P less than .05) and collagen solubility decreased (P less than .05) with age, indicating that collagen turnover was occurring most rapidly in 12-wk-old lambs and that collagen maturation was predominant in 24- to 30-wk old lambs. Testosterone parameters measured in rams were unrelated within groups to collagen characteristics, possibly reflecting the high variability in testosterone secretion and the slow development of collagen. However, rams as young as 12 wk of age were under the influence of testosterone, and differences in collagen between rams and wethers were apparent at that time.     

Effect of vitamin E and copper on the vitamin E status and performance of growing pigs

A 13-wk trial was conducted with 32 pigs to determine the effects of dietary Cu (250 ppm) and alpha-tocopheryl acetate (ATA, 22 IU/kg) on the performance, serum enzymes, serum and tissue tocopherols, and antibody production in growing pigs. Pigs were fed corn-soybean meal diets containing 21% CP the first 4 wk and 18% CP during the rest of the trial. All feed was stored a minimum of 14 d before it was fed. The addition of Cu decreased (P less than .01) the concentration of alpha-tocopherol in the feed. alpha-Tocopherol concentrations were less than .01 mg/kg in the starter diet and less than 2 mg/kg in the grower diet after 14 d of storage. Supplemental Cu or ATA had no effect on ADG, feed intake, or gain:feed during the first 4 wk. During wk 5 to 13, the addition of Cu to diets containing no ATA increased daily feed intake and decreased gain:feed, but with ATA addition, feed intake decreased and gain:feed increased, resulting in a Cu x ATA interaction (P less than .05). The addition of Cu or ATA had no effect (P greater than .1) on serum glutathione peroxidase or lactic dehydrogenase activity. Serum tocopherols were reduced (P less than .05) by the addition of Cu during wk 1 to 4, 6 (P less than .01), and 7 (P less than .05) and increased (P less than .01) by ATA addition during the entire experiment. The addition of ATA increased the tocopherol concentrations in bile, ham, heart, pancreas, kidney, spleen, liver, psoas and longissimus muscle (P less than .01), kidney fat, backfat, and adrenal gland (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of methionine hydroxy analog on voluntary intake, digestibility, nitrogen balance, and chewing behavior in sheep fed grass silage

Voluntary intake, digestibility, N balance, and chewing behavior of six 6-mo-old (young) and six 30-mo-old (mature) Texel wethers (32.6 and 83.1 kg average BW) given ad libitum access to grass silage and 100 g of top-dressed soybean meal with or without 5 g of methionine hydroxy analog (MHA) in the acid form were examined according to a two-period crossover design. Supplementation level of MHA in the acid form corresponded to .32 and .16 g of MHA/kg BW.75, respectively, in young and mature wethers. There was no effect (P greater than .10) of MHA on mean voluntary DMI. Methionine hydroxy analog supplementation increased (P less than .02) digestibility of DM, OM, and CP by young wethers but not (P greater than .18) by mature wethers. The MHA decreased eating time (P less than .03) in both young and mature wethers and intake level (P = .01) in young wethers during the first 1.5 h of access to grass silage. With MHA, both age groups increased (P less than .05) the daily number of meals and decreased (P less than .02) the mean duration of each meal. There was no effect (P greater than .06) of MHA on daily and unitary eating, ruminating, and masticating times; however, mean duration of consecutive rumination bolus cycles was longer (7.2%; P = .01) in young wethers. Young vs mature sheep ate more (53.4 vs 39.3 g of DM/[d.kg BW.75]; P less than .001) and had shorter unitary mastication times (P = .001). Results suggest that, depending on its relative level of supplementation, MHA in the acid form could act through both palatability and effects on ruminal metabolism.     

Effects of potassium on macromineral absorption in sheep fed wheat straw-based diets

Two experiments were conducted to determine the effect of increasing dietary K on macromineral bioavailability from a wheat straw-hay diet, and to monitor changes in the rumen that could affect mineral availability. In the first experiment, 12 mature wethers were used in a metabolism study to determine the effect of adding potassium chloride (KCl) to a supplement fed with a diet of 55% NH3-treated wheat straw and 45% bromegrass hay. In the second experiment, similar diets were fed to six wethers with ruminal and abomasal cannulae to determine the site of mineral absorption. Dietary K levels were 1, 2 and 3% of the diet dry matter. Increasing K tended to decrease (P less than .06) apparent absorption of Mg. Potassium absorption increased (P less than .01) with increasing dietary K, but retention was not altered. Quadratic effects (P less than .01) of K were observed for Ca and P apparent absorption and retention. Increased K lowered (P less than .05) plasma Mg in Exp. 1 but not in Exp. 2. Ruminal concentrations of K increased (P less than .01), and concentrations of Na decreased (P less than .05), as dietary K increased. Ruminal fermentation was influenced by dietary K level. Molar proportions of acetate in the rumen were increased (P less than .01) by the addition of K to the diet, while molar proportions of butyrate (P less than .01) and valerate (P less than .01) decreased linearly with increasing K. Time X treatment interactions were present for ruminal propionate, butyrate and NH3-N (P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)