Wether Lambs Research Articles

Effects of protein and energy supplementation of wheat straw-based diets on site of nutrient digestion and nitrogen metabolism of lambs.

A 4 x 4 Latin square metabolism trial with 2 x 2 factorial arrangement of treatments was conducted with lambs to determine effects of energy and CP supplementation of wheat straw-based (WS) diets on apparent N digestion, retention, and flow to the abomasum. Four wether lambs (average weight, 32 kg) fitted with ruminal and abomasal cannulas were fed 70 vs 42% WS (remainder of the diet was concentrate) and 9.5 vs 12.5% CP. Ruminal and total tract DM and OM digestion was 41 and 33% greater (P less than .03) for high-energy than for low-energy diets. Apparent N digestibility was greater (P less than .05) for 12.5% CP than for 9.5% CP diets (69.2 vs 62.0%, respectively) and also greater (P less than .03) for high-energy than for low-energy diets (67.4 vs 63.7%, respectively). High-energy diets resulted in a 23% greater (P less than .03) N retention (percentage of N intake) than did low-energy diets; 12.5% CP diets resulted in a 9% greater N retention (P less than .10) than did 9.5% CP diets. Nitrogen retention (percentage of N digested) was 15% higher (P less than .03) for high-energy than for low-energy diets. Protein level had no effect (P greater than .10). Nitrogen retention (grams/day) was 5.65, 6.97, 5.28, and 7.43 for low-energy, high-energy, low-protein, and high-protein diets, respectively; there were responses to energy level (P less than .03) and protein level (P less than .05). Total N flow (grams/day) to the abomasum did not differ (P greater than .10) due to treatment.(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)

Towards optimum grazing management for sheep production on crownvetch (Coronilla variaL.)

The performance of wether lambs on crownvetch (Coronilla varia L.) pasture was determined for three seasons under five grazing procedures. These included continuous grazing and rotational grazing with a 7‐day period‐of stay and periods‐of‐absence of 7, 21, 35 or 49 days. Performance was the same with all five systems. Supplementary measurements involving oesophageal‐fistula samples and quadrat harvests indicated that the quality and amount of grazable herbage in the different systems were similar. Weeds increased noticeably in the third season and were more prevalent with continuous and near‐continuous grazing. The grazing capacity for a five‐month grazing season was estimated at 3.0–3.5 LSU (about 30–35 weaner lambs) ha−1. Under local conditions, livemass gains in the order of 20 kg lamb−1 in a period of 130–160 days can be achieved.

Effects of bovine somatotrophin on insulin-like growth factor-I, insulin, growth and carcass composition of lambs

The effect of different doses (0.0, 0.05, 0.15, 0.25 and 0.55 mg/kg/day) of recombinant bovine somatotrophin (BST) on plasma concentrations of growth hormone (GH), insulin-like growth factor-I (IGF-I), insulin, plasma metabolites, growth and body composition were studied by treating five groups ( n=8/group) of pasture-fed wether lambs (6–7 months of age) with daily subcutaneous injections of saline or BST for 62 days. Lambs ( n=4/group) were bled from 09.00 to 06.00 h on day 59–60. Plasma GH concentrations rose to a maximum (914 ± 184 ng/ml) by 2 h following administration of an injection of BST (0.55 mg/kg/day) and after 24 h had decreased to 30–40 ng/ml GH in 0.25 and 0.55 mg/kg/day BST groups or to control concentrations in 0.05 and 0.15 mg/kg/day BST groups. Long-term BST treatment increased ( P<0.001) plasma concentrations of IGF-I, insulin, non-esterified fatty acids and glucose. Body and carcass weights were also increased ( P<0.05) by BST and there was a major ( P<0.01) effect on body and carcass components, particularly fat depot weights. The results from this study suggest that the growth/compositional responses to BST treatment are related to increases in plasma IGF-I and insulin concentrations.

Effect of ruminal escape protein and fat on nitrogen utilization in lambs exposed to elevated ambient temperatures.

Eight wether lambs (mean BW = 28.8 kg) with ruminal and abomasal cannulas were assigned to either thermally neutral or high ambient temperature treatments. Within each temperature, lambs were randomly allotted to dietary treatments consisting of a basal diet (60% corn and 24% cottonseed hulls) either with (high; 11.4% CP) or without (control; 10.1% CP) added ruminal escape CP as fish meal and with (high) or without (control) 5% added ruminally inert fat in a 2 x 2 factorial treatment arrangement using a Latin square design. Lambs were fed 606 g of DM/d in each period, which consisted of a 10-d adjustment followed by 6 d of sample collection. High temperature increased (P less than .05) respiration rate, evaporative water loss, and rectal temperature. When compared with controls, lambs fed high escape CP retained more N when exposed to high temperatures (2.8 vs 3.6 g of N/d) and less N at neutral temperatures (3.3 vs 3.1 g of N/d; temperature x escape CP; P less than .05). Retention of N was greater (P less than .05) in lambs fed high than in those fed control fat (3.8 vs 2.7 g/d). Lambs fed high vs control escape CP had greater abomasal feed N flow (percentage of intake) when fed high-fat diets (77.3 vs 56.1%) but similar dietary N flow when fed control fat diets (55.8 vs 54.3%; fat x escape CP; P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of treating corn stover with wood ashes and sodium hydroxide on nutrient digestibility by sheep and goats

In expt I, twelve lambs (average BW 30 kg) were fed diets containing 85% corn stover (CS) treated with 0, 10, 20 and 30% solutions ( w/v) of wood ash (WA). Digestibility of DM was increased ( P < 0.01) from 56.3% to 62.0%, CP, ADF and NDF digestibilities increased ( P<0.05) from 57.3, 53.0, 60.5% to 66.2, 61.3 68.6% for 0 to 30% WA, respectively. In expt II, nine wether lambs (average BW 29.2 kg) were fed diets containing untreated CS or stover treated with a 20% solution ( w/v) of WA or a solution of NaOH (4 g/100 g CS). There were no differences ( P>0.05) in ADF and NDF digestibilities between sheep fed diets containing CS treated with WA (56.6, 65.7%) or NaOH (55.7, 63.5%), but both were greater ( P<0.05) than ADF and NDF digestion in control lambs (43.4, 50.5%). In expt III, nine male castrated goats (average BW 32.6 kg) were fed the same diets as sheep in experiment II. Goats responded to treatments in a similar manner to sheep. Results suggest that treating CS with a 20% solution of WA can increase fiber digestibility in sheep and goats to a degree comparable to that observed with NaOH treatment.

Effects of zeranol and two dietary levels of calcium and phosphorus on performance, carcass and bone characteristics, and calcium status in growing lambs.

Seventy-two crossbred wether lambs (average initial weight, 25.1 kg) were used to determine the interaction between zeranol treatment and two dietary levels of Ca and P (.8 and .6% vs .4 and .3% Ca and P, respectively) in a 2 x 2 factorial arrangement on performance, carcass and bone characteristics, and serum concentrations of parathyroid hormone (PTH) and Ca. Lambs were implanted on d 0 and 56 with 12 mg of zeranol. Lambs had ad libitum access to feed for 105 d. On d 99, blood samples were collected. Implanted lambs had 12% greater (P less than .01) daily feed intake, 26% greater (P less than .10) ADG, and a 12% improvement in (P less than .10) feed efficiency compared with nonimplanted lambs. Zeranol-treated lambs had increased (P less than .05) bone cortical area, breaking load, and width of the metacarpal compared with nonimplanted lambs. Lambs fed the .8% Ca and .6% P diet had a higher (P less than .05) percentage of bone ash than lambs fed the .4% Ca and .3% P diet. However, there were no differences (P greater than .05) in the percentage of Ca, P, Mg, or Zn in metacarpal bones due either to higher dietary Ca and P or to implant treatments. Serum concentration of PTH was greater (P less than .10) in lambs fed .8% Ca and .6% P than in those receiving .4% Ca and .3% P. Serum concentrations of PTH and Ca pooled across treatments were greater (P less than .05) before feeding than at 1 h after feeding.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of pattern of food supply on performance, compensatory growth and carcass composition of Beulah and Welsh Mountain lambs

AbstractSeventy-eight Beulah (BH) and 78 Welsh Mountain (WM) wether lambs (mature live weights (MLW) 60 and 70 kg respectively), were used to investigate genotypic differences in performance and compensatory growth during the post-weaning period. After an initial slaughter of 12 of each breed, a complete straw-based pelleted diet (122 g crude protein and 10·4 Mj metabolizable energy per kg dry matter (DM)) was offered ad libitum to a further 29 of each which were slaughtered at a range of live weights between proportionately 0·35 andl -00 of ML W. As well as these groups undergoing normal growth (NG), the remaining lambs were given the same diet at a level sufficient to maintain constant live weight (LW) for 3 months. Eight of each breed were then slaughtered and the remaining 29 of each offered the diet ad libitum for a period of post-restricted growth (PRG); these 29 were also slaughtered between 0·35 and 1·00 of MLW. During the periods of ad libitum food supply, voluntary food intake was greater in BH than WM lambs (BH: 38·3, WM: 35·3 g DM per kg LW, P &lt; 0·01) and during PRG as compared with NG although this result was due to a response only in WM lambs (NG - BH: 38·0, PRG-BH: 38·5, NG - WM: 33·3, PRG - WM: 37·2 g DM per kg LW, breed × pattern of food supply interaction, P &lt; 0·05). Daily live-weight gain (LWG) was greater during PRG than NG in both breeds (NG: 3·15, PRG: 4·80 g/kg LWper day, P &lt; 0·05). This effect was greatest in the first 8 weeks of growth but persisted into the period 16 weeks to maturity. WM lambs had overall slightly leaner carcasses and a lower proportion of protein in the fleece-free empty body than BH when compared at the same proportion of MLW; particularly during PRG. The protein in the carcass-weight gain (CWG) was greater in WM lambs during PRG than during NG (NG: 98, PRG: 123 g/kg, P &lt; 0·05), but did not differ significantly in BH (NG: 106, PRG: 118 g/kg). The proportion of fat in CWG was concomitantly smaller during PRG. There are thus breed differences in the performance and carcass composition of lambs during compensatory growth. Genotypes to be finished by continuous feeding or a regimen incorporating food restriction should be carefully chosen for date offinishing in relation to desired carcass composition.

Economies of Lamb Production on Wheatgrasses and Wheatgrass-Sainfoin Pastures

Price trend data since 1978 indicate a seasonal increase in lamb (Ovis aries) prices during spring and early summer. This seasonal price increase occurs over the same period as lamb weight gains observed from previous grazing trials with wheatgrass (Agropyron and Thinopyron spp.) and wheatgrass-sainfoin (Onobrychis spp.) mixtures. Little information is available on the economics of lamb production from these forages on the Southern Great Plains. Our objective was to determine the potential profitability of spring lamb production from three irrigated wheatgrasses, ‘Hycrest’ [A. cristatum (L.) Gaertner × A. desertorum (Fischer ex Link) Snuiters], ‘Luna’ [T. intermedium subsp. barbulatum (Schur) Barkw. and D.R. Dewey], and ‘Jose’ [T. ponticum (Podp.) Barkw. and D.R. Dewey] grown alone and with ‘Renumex’ sainfoin (O. viciifolia Scop.). Replicated pastures grown on a Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll) were rotationally grazed (dry matter allotment of 6.5% of body wt/d) by weaned Rambouillet × Suffolk wether lambs for an average of 77 d in spring of 1987 and 1988. Lamb production ranged between 142 and 420 lb/acre. Gross margins per acre for lamb production were Hycrest, −$85; Luna, −$5; Jose, −$48; Hycrest-sainfoin, $83; Luna-sainfoin, $91; and Jose-sainfoin, $64. Our results showed that despite fluctuations in lamb output price, lamb production from wheatgrasses grown with sainfoin was more profitable than from wheatgrasses grown alone.

Level of nutrition and visceral organ protein synthetic capacity and nucleic acid content in sheep.

Thirty-two crossbred wether lambs were assigned to a feed intake level of either ad libitum (ADLIB) for maximum rate of growth or restricted to maintain body weight (MAINT) throughout a 21-d period. At 7-d intervals (d 0.7, 14, and 21), four lambs per treatment were slaughtered to obtain measurements of visceral organ protein synthetic capacity and tissue composition. Protein synthetic capacity was assessed by in vitro [14C]valine incorporation and tissue RNA, DNA, and protein contents. Concentrations of protein and RNA were not significantly affected in most tissues measured. However, for liver, duodenal, and jejunal tissue, DNA concentrations in ADLIB lambs were lower (P less than .05) than in MAINT lambs. Ratios of protein:DNA in most organs were higher (P less than .05) in ADLIB than in MAINT lambs. During the 21-d period, liver and small intestinal protein and RNA mass were higher (P less than .10) in ADLIB than in MAINT lambs, and DNA mass was unaffected. Also during the 21-d period, the average total mass of ruminal protein, RNA, and DNA in ADLIB lambs was higher (P less than .05) than in MAINT lambs. Estimates of valine incorporation and ratios of RNA:protein seemed to reflect protein synthetic capacity of the visceral tissues measured; however, the effect of level of feed intake on these measurements was equivocal. These data suggest that the level of feed intake affected visceral organ mass through changes in cellular hypertrophy.

Production and biological activity of hybrid growth hormone-releasing hormone propeptides.

Growth hormone-releasing hormone (GHRH), a hypothalamic hormone that stimulates the synthesis and release of growth hormone (GH) from anterior pituitary cells, has been previously produced by synthetic peptide chemistry and recombinant DNA procedures. GHRH is capable of stimulating growth as well as eliciting other anabolic effects on animals and thus may have potential applications in agriculture and human medicine. However, economical production of GHRH by recombinant DNA process has been difficult since GHRH is degraded rapidly by endogenous E. coli proteases. We report here an efficient process to produce hybrid GHRH analogs of higher molecular weight. These hybrid GHRH propeptides (proGHRH) are comprised of an analog of GHRH (44 aa) and the human GHRH carboxy-terminal peptide (33 aa). In E. coli K-12 RV308, the expression levels of the proGHRH analogs were estimated to be 10% of the total cellular protein. An in vitro assay to measure the release of rat growth hormone by GHRH analogs using crude E. coli lysates was also developed. This assay showed that the proGHRH analogs produced in E. coli efficiently stimulated GH release from rat anterior pituitary cells. One proGHRH analog, [alao]-proGHRH, was purified ans shown to efficiently elevate plasma GH levels in wether lambs. Our data indicate that the hybrid proGHRH peptides, unlike other hormone propeptides such as proinsulin, are remarkably bioactive.

Effects of lamb age, muscle type, and 24-hour activity of endogenous proteinases on postmortem proteolysis1

The objectives of this study were to examine the amount of postmortem proteolysis in three different lamb muscles at different ages and to determine whether a relationship exists between the extent of myofibrillar degradation and certain endogenous proteinase activities. Wether lambs were slaughtered at 8 (n = 6) and 26 (n = 6) wk of age. Samples were taken from the longissimus (LM), gluteus medius (GM), and supraspinatus (SS) muscles for determining myofibrillar fragmentation index (MFI) at 1 and 7 d postmortem, cathepsins B and B + L, cystatin(s), mu- and m-calpain and calpastatin 24-h activities, and muscle fiber type and area. Muscle samples were removed for SDS-PAGE analysis at 0, 1, and 7 d postmortem. The SS muscle consisted of more (P less than .05) oxidative fibers, whereas no age effects (P greater than .10) were observed for fiber type. The younger lambs had higher (P less than .01) cathepsins B and B + L, cystatin, and calpastatin 24-h activities but less (P less than .01) m-calpain activity than did the 26-wk-old lambs. Within each age, the SS muscle had the highest (P less than .05) mu-calpain, m-calpain, and calpastatin specific activities. The MFI values and SDS-PAGE results indicate that less proteolysis occurred in the SS muscle. Samples from 26-wk-old lambs tended to have greater MFI values at 1 and 7 d postmortem, especially for the LM and GM muscles. From these results, it seems that less postmortem proteolysis occurs in younger and more oxidative muscles and this may be attributed to the greater calpastatin 24-h activity.

Effects of starch on ruminal fermentation and detergent fibre digestion in lambs fed bermudagrass hay

Twelve cannulated Suffolk wether lambs (30.1 kg) were used in a randomised complete block design experiment to determine the effects of increasing dietary concentrate (corn starch-based) on ruminal digestive kinetics and fermentation characteristics and digestion of bermudagrass hay (BGH) fibre in lambs. Treatments consisted of as-fed concentrate:BGH ratios (C:F) of 10:90, 40:60 and 70:30. Ruminal digestion of neutral detergent fibre (NDF) and hemicellulose (HC) declined linearly ( P < 0.01) with increasing C:F. Quadratic responses to post-ruminal ( P < 0.10) and total tract ( P < 0.05) digestion of HC were obtained with increasing C:F. Total tract digestion of NDF declined linearly ( P < 0.05) with increasing C:F. Extent of acid detergent fibre (ADF) digestion was not affected ( P > 0.10) by C:F at any digestive site. Integrated pH-hours below pH 6.7 declined linearly ( P < 0.01) with increasing C:F and was correlated with ruminal digestion of NDF ( r = −0.75, P = 0.005) and HC ( r = −0.67, P = 0.018). Ruminal volatile fatty acid (VFA) concentrations increased linearly ( P < 0.01) with increasing C:F and were correlated with ruminal digestion of NDF ( r = −0.88, P = 0.001) and HC ( r = −0.82, P = 0.001). Ruminal liquid turnover was not affected ( P > 0.10) by C:F. Ruminal forage particulate passage rate tended ( P = 0.12) to increase with increasing C:F and was correlated with the ruminal digestion of both NDF ( r = −0.67, P = 0.023) and HC ( r = −0.57, P = 0.063). While virtually all potentially digestible ADF (cellulose) was digested in the rumen, ruminal escape of HC increased with increasing C:F. Data suggest that HC is the cell wall fraction of BGH that is the most sensitive to dietary starch level.

Physiological and carcass characteristics of hair and wool breeds of sheep

Physiological, performance and carcass characteristics were studied in hair sheep (three St. Croix (SC), four Barbados Blackbelly (BB) and four Katahdin (K) and wool sheep (four Dorset (D)). Initial weights of the wether lambs ranged from 17.9 (BB) to 21.4 (D) kg. Lambs were fed a 16% CP commercial pelleted diet for 94 d. Ambient temperature averaged 20.9°C. Jugular blood samples collected on days, 1, 14, 28, 56, 70 and 84 were analyzed for hematological and blood chemistry parameters. Feed intake was higher ( P < 0.05) in D and K, and BB lambs consumed less water than D ( P < 0.05). BB gained the least weight and had the highest feed-to-rain ratio ( P < 0.05). Dressing percentage was highest ( P < 0.05) in BB and K, and D lambs had the largest ribeye area and lowest percent kidney-pelvis-heart (KPH) fat ( P < 0.05). Intramuscular fat and cholesterol were highest in K ( P < 0.05). Though significant breed effects were found in PUN, albumin, glucose, hemoglobin, hematocrit and WBC count, none exceeded normal physiological ranges. Plasma epinephrine levels were highest ( P < 0.05) in BB toward the end of the study and norepinephrine levels at the beginning were lowest ( P < 0.05) in D. There were no breed effects on plasma cortisol during the first 14 days, after which values were highest in K and lowest in SC lambs.

Modeling Lamb Weight Changes on Wheatgrass and Wheatgrass‐Sainfoin Mixtures

AbstractPrediction of animal weight change (CUM) with regression models developed from grazing trials typically uses herbage parameters and CUM measured on the same day. We hypothesized that lamb (Ovis aries L.) CUM recorded at time t was a function of herbage quality and/or quantity measured at a previous harvest t − x (where x = days prior to measurement of CUM). Our objectives were (i) to determine if time series regression analysis (TSR) could be used to model CUM from three irrigated wheatgrasses, ‘Hycrest’ [Agropyron cristatum (L.) Gaertner × A. desertorum (Fischer ex Link) Shulters], ‘Luna’ [Thinopyrum intermedium subsp. barbulatum (Schur) Barkw. and D.R. Dewey], and ‘Jose’ [T. ponticum (Podp.) Barkw. and D.R. Dewey] grown alone and with ‘Renumex’ sainfoin (Onobrychis viciifolia Scop.), and (ii) to test the models. Replicated pastures grown on a fine, mixed thermic Torrertic Paleustolls were rotationally grazed by Rambouillet × Suffolk wether lambs for an average of 77 d in spring of 1987 and 1988. Herbage quality, quantity, and plant parts were estimated from pregrazing, after 2 and 4 d of grazing, and postgrazing (7 d) harvests and used as variables in TSR. For TSR models, lagged variables (t − x) were selected more (67–92% of total) than nonlagged variables (t), supporting our hypothesis. Time series regression models described CUM accurately (average R2 &gt; 0.70), but selected variables were not consistent among treatments, time lags, or years. Model testing indicated poor predictive accuracy (r2 = 0.07−0.51), limiting the usefulness of projecting CUM across seasons and demonstrating the necessity of testing regression models.

Effect of long‐term intra‐ruminal infusion of the glucosinolate metabolite allyl cyanide on the voluntary food intake and metabolism of lambs

AbstractThe possible role of allyl cyanide (ACN), the nitrile breakdown product of prop‐2‐enyl glucosinolate, in reducing the voluntary food intake (VFI) of a dried grass pellet diet in sheep was examined in a ruminal infusion experiment. Voluntary food intake of Scottish Blackface wether lambs, infused intraruminally with allyl cyanide (0 mmol day−1, C; 4.8 mmol day−1 L; 9.6 mmol day−1, H) for 9 weeks was significantly depressed (P &lt; 0.05) on H and L treatments compared with the C treatment. Clinical indicators of liver function (plasma gamma glutamyl transpeptidase (GGTP) activity) and kidney function (plasma urea and creatinc concentrations) indicated minor liver damage but no effects on renal function. Plasma GGTP activity was significantly (P &lt; 0.05) higher in the H than in the C group. Liver cytochrome oxidase activity at the end of the infusion period was significantly lower (P &lt; 0.05) in the H than in the C group indicating effects on cellular respiration. In general, sheep showed considerable tolerance to administration of ACN in comparison with previously demonstrated toxicity in monogastrics.

Retail cut yields of Rambouillet wether lambs fed the beta-adrenergic agonist L644,969.

Twenty Rambouillet wether lambs were given ad libitum access to a diet with (BAA, n = 10) or without (control, n = 10) 1 ppm of the beta-adrenergic agonist L644,969. Lambs were fed to a constant slaughter weight end point of 54.5 kg. Carcasses were fabricated to yield bone-in and boneless cuts that were trimmed progressively to 1.27, .64, .32, and .00 cm of s.c. fat remaining. Addition of BAA did not affect growth traits. Actual and adjusted fat thickness, body wall thickness, and percentage of kidney-pelvic fat did not differ between control and BAA lambs. However, BAA increased longissimus muscle area, longissimus muscle depth, and leg score while decreasing USDA yield grade. The BAA increased carcass conformation scores and decreased flank lean color scores. No other carcass quality measurements were affected by BAA. Addition of BAA did not affect overall carcass yields of bone-in retail cuts. However, BAA increased overall carcass yields of boneless retail cuts regardless of fat trim level. The BAA increased bone-in leg yield. Yield of boneless sirloin, bone-in loin and boneless loin were not affected by BAA. For these cuts, the percentage change from the control was highly dependent on fat trim level. There was no difference in short-cut, shank-off, semiboneless leg yield between control and BAA. Addition of BAA did not affect yield of bone-in rack regardless of fat trim level. However, BAA greatly increased yield of boneless ribeye. The BAA did not affect yield of bone-in or boneless shoulder.(ABSTRACT TRUNCATED AT 250 WORDS)

Factors influencing difficulty of removing pelts from lamb carcasses3

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.

Abomasal Casein Infusion and Exogenous Somatotropin Enhance Nitrogen Utilization By Growing Lambs

Growing Dorset wether lambs (23 kg initial body weight) were used to determine whether the magnitude of nitrogen retention response to daily administration of exogenous somatotropin is limited by post-ruminal amino acid availability in growing ruminants. Eight lambs surgically fitted with abomasal cannulae were fed a total mixed ration of 85% of ad libitum intake. All lambs received a continuous abomasal infusion of 2 L of water or casein and twice daily subcutaneous injections of 0 or 100 micrograms recombinant bovine somatotropin (rbST)/kg body wt for 15 d per treatment in a 2 x 2 single reversal design. The casein solution was infused at a rate (4 to 5 g nitrogen/d) to achieve 25% of nitrogen intake observed with ad libitum feeding prior to initiation of treatments. Each lamb received all four treatments. Nitrogen balance was determined on d 8 to 14 of each treatment. Casein infusion increased nitrogen balance 43.4% (P less than 0.001), and rbST increased nitrogen balance 33.5% (P less than 0.001), without significant interaction (P less than 0.88). Combined effects of casein and rbST were additive, resulting in an 89% increase in nitrogen balance when compared with water plus excipient treatment. Results suggest that the quantity or composition of absorbed amino acids, or both, limit nitrogen retention by growing lambs, and that rbST increases the efficiency of utilization of absorbed amino acids for protein deposition.

Effect of the β-adrenergic agonist L644,969 on muscle growth, endogenous proteinase activities, and postmortem proteolysis in wether lambs1

To examine the effect of a beta-adrenergic agonist (BAA) on muscle growth, proteinase activities, and postmortem proteolysis, 16 wether lambs were randomly assigned to receive 0 or 4 ppm of L644,969 in a completely mixed high-concentrate diet for 6 wk. Weight of the biceps femoris was 18.6% heavier in treated lambs. At 0 h after slaughter, treated lambs had higher cathepsin B (35.6%), cathepsins B + L (19.1%), calpastatin (62.8%), and m-calpain (24.6%) than control lambs, but both groups had similar mu-calpain activities. In both longissimus and biceps femoris muscles, treated lambs had higher protein and RNA and lower DNA concentrations. However, total DNA was not affected, indicating that the increase in muscle mass was probably due to muscle hypertrophy rather than to hyperplasia. The pattern of postmortem proteolysis was significantly altered by BAA feeding. In treated lambs, postmortem storage had no effect on the myofibril fragmentation index and degradation of desmin and troponin-T. These results indicate that the ability of the muscle to undergo postmortem proteolysis has been dramatically reduced with BAA feeding. Similar proteolytic systems are thought to be involved in antemortem and postmortem degradation of myofibrillar proteins, so BAA-mediated protein accretion is probably due, at least in part, to reduced protein degradation. To examine whether protein synthesis was altered with BAA feeding, the level of skeletal muscle alpha-actin mRNA was quantified. Longissimus muscle alpha-actin mRNA abundance was 30% greater in BAA-fed lambs. Collectively, these results indicate that dietary administration of BAA increases muscle mass through hypertrophy and that the increase in muscle protein accretion is due to reduced degradation and possibly to increased synthesis of muscle proteins.