Effects of cimaterol on nitrogen retention and energy utilization in lambs

Fifty-two weaned lambs were used in a comparative slaughter feeding trial and six lambs in a concurrent digestibility trial to investigate the effects of cimaterol on nitrogen retention and energy utilization. Cimaterol (CIM) was administered in the feed at 10 ppm for 90 and 14 d, respectively, in a comparative slaughter feeding trial and in a digestibility trial. No difference was found in dry matter digestibility. Nitrogen retention in the CIM group (739 mg/Wkg.75/d) was greater (P less than .01) than that of the control group (321 mg/Wkg.75/d). This difference was accounted for primarily by reduced nitrogen loss in urine of the CIM group. Cimaterol improved growth rate and feed/gain ratio, although these improvements were only evident during the first 42 d of the 90-d feeding trial. The improvement in growth performance of the CIM group was associated with increased protein gain in the empty body (40.2 g/d, P less than .01) as well as in carcass (26.9 g/d, P less than .01), compared with 30.1 and 14.5 g/d of the control group. Cimaterol decreased (P less than .01) fat gain (91.4 vs 109.9 g/d), total daily energy gain (1.08 vs 1.22 Mcal) and energy gain/kg gain (4.17 vs 5.11 Mcal) compared with the control. Feeding CIM increased (P less than .01) estimated fasting heat production (73 vs 64 Kcal/Wkg.75) and metabolizable energy requirement for maintenance (110.2 vs 92.7 Kcal/Wkg.75) over the control.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of dietary palm oil supplementation on serum lipid metabolites, carcass characteristics, and lipid composition of carcass tissues of growing ram and ewe lambs.

The objective of this research was to determine the influence of dietary palm oil supplementation on carcass characteristics and lipid composition of tissues from growing lambs. Twenty-eight Suffolk x Hampshire lambs were weaned at 60 d of age (average 36 kg BW) and assigned to a 2 x 2 factorial arrangement consisting of diet (control [NPO] or 10.6% added dietary palm oil [PO]) and sex (ram vs ewe). The NPO diet (77% forage and 23% concentrate) contained 11.2% CP and 2.66 Mcal of ME/kg. Palm oil replaced molasses in the PO diet. Lambs were individually given ad libitum access to feed for 60 d to a final BW average of 50.1 kg. Lipid composition of the longissimus muscle and corresponding subcutaneous (s.c.) adipose tissue was determined by gas-liquid chromatography (GLC). Lambs fed PO were fatter (P less than .01) than lambs fed NPO (.77 vs .56 cm, s.c. fat). Diet had no effect on cholesterol content of lean tissue; however, feeding PO increased the saturated fatty acids of lean tissue. The s.c. fat from lambs fed PO had less (P less than .01) cholesterol (64.79 vs 89.67 mg/100 g) and more saturated fatty acids than that from lambs fed NPO. Ewes were fatter (P less than .01) than rams, yet they had less cholesterol content in the s.c. adipose tissue (68.71 vs 85.74 mg/100 g). High amounts of dietary palm oil fed to growing lambs caused changes in fatty acid deposition and cholesterol metabolism and may be a useful investigative tool to study lipid metabolism in growing ruminants.(ABSTRACT TRUNCATED AT 250 WORDS)     

Responses to cimaterol in genetically obese and lean pigs

Twenty-four genetically obese and 24 lean barrows were allotted within genotype to either a 16% CP corn-soybean meal basal diet, the basal + .69 ppm cimaterol or the basal + 1.38 ppm cimaterol. Pigs had ad libitum access to their diets from 59.3 kg to 104.5 kg body weight. No genotype x cimaterol interactions were detected (P greater than .05). Neither genotype nor cimaterol supplementation had any effect (P greater than .05) on average daily weight gain or gain-to-feed ratio. Compared with lean pigs, obese pigs had higher fasting plasma urea nitrogen (BUN), a smaller gastrointestinal tract and a greater dressing percentage with a shorter and fatter carcass (P less than .05). Cimaterol produced a higher fasting plasma BUN, a greater dressing percentage with a leaner carcass and a higher shear force value for loin chops (P less than .05). Cimaterol also tended (P less than .10) to increase heart weight. However, no difference was observed in these measurements between pigs fed .69 or 1.38 ppm cimaterol. In lean pigs fed the basal or .69 ppm cimaterol diet, there was no difference (P greater than .05) in the 8 to 24 h postprandial whole-animal heat production. Cimaterol effectively decreased fat deposition and increased lean accretion both in genetically obese and in lean pigs; there were no differential responses to cimaterol in pigs with different propensities to deposit body fat.     

Evaluation of cimaterol for finishing swine including a drug withdrawal period

One hundred fifty crossbred pigs (55 kg) were allotted by weight, sex and litter to a randomized complete-block design with five dietary treatments, six blocks per treatment and five pigs per pen with sex equalized across treatments. Corn-soybean meal-based diets (.65% lysine) with 0, .25 and .5 mg/kg cimaterol were fed, on an ad libitum basis, to pigs slaughtered at an average pen weight of 104 kg/pig. Drug withdrawal prior to slaughter was 1, 3 and 5 d for pigs fed cimaterol at .25 mg/kg and 1 d for those fed cimaterol at .5 mg/kg of diet. Dietary cimaterol level influenced (quadratic, P less than .01) average daily gain during the first 42 d on test; however, daily feed intake and feed conversion ratio were not affected (P greater than .1). Pigs fed .25 mg/kg cimaterol with a 1-d drug withdrawal had 6.8, 7.7 and 13.5% less 10th rib fat depth and 11.1, 6.1 and 13.3% less P2 fat depth than those subjected to either a 3- or 5-d drug withdrawal or those fed the 0 mg/kg cimaterol diet (control), respectively. Overall, pigs fed cimaterol had 7.9% larger longissimus muscle area and 2.6% more kilograms of muscle than pigs fed the control diet. Cimaterol fed at .5 mg/kg resulted in higher (P less than .05) Warner-Bratzler shear force values and altered the proportion of saturation in some long-chain fatty acids, although the total saturated:unsaturated fat ratio was not affected. Pigs fed no cimaterol had less thaw loss (P less than .05) than did those fed other treatments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of dietary canola seed and soy lecithin in high-forage diets on performance, serum lipids, and carcass characteristics of growing ram lambs

Phospholipids (soy lecithin) are important in the emulsification of lipids and may be able to escape the rumen and influence the absorption of fatty acids in the small intestine. The objectives of this study were to determine the influence of dietary canola seed (high in unsaturated fatty acids) and soy lecithin in high-forage diets on performance, serum lipid metabolites, and carcass characteristics of growing ram lambs. Forty-three Hampshire- or Suffolk-sired ram lambs were weaned at 60 d of age (average 23.6 kg BW) and assigned to a 2 x 2 factorial arrangement of the following treatments (% of DM): 1) basal diet (control = BAS); 2) BAS with 6% whole canola seed (CS); 3) BAS with 4.9% deoiled soy lecithin (SL); and 4) BAS with 6% CS and 4.8% SL (CSSL). The BAS diet consisted of 70% forage and 30% concentrate and contained 15% CP and 2.2 Mcal of ME/kg. Lambs had ad libitum access to their diet to an average final BW of 52.1 kg. Lambs were bled by jugular venipuncture on d 0, at 4-wk intervals, and 1 d before slaughter. Dry matter intake was not affected by treatment; however, energy intake (Mcal of ME/d) was greater (P less than .01) for lambs fed SL. Feeding SL and(or) CS to growing ram lambs increased (P less than .02) serum lipid concentrations. Carcasses from lambs fed SL were fatter, as evidenced by greater dressing percentage and subcutaneous fat thickness. Feeding CS to growing lambs had little effect on performance and carcass characteristics compared with feeding SL, which resulted in greater energy intake and fatter carcasses.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of zeranol on live weight gain, feed intake and carcass composition of steers during compensatory growth

To evaluate the effect of zeranol implants in steers on compensatory ++growth, 80 steer calves (9 mo of age; 200 kg) were fed at two feeding levels (RO = 9.2 MJ ME/kg DM; R1 = 6.9 MJ ME/kg DM) for 119 d (Period 1). During Period 2, steers were full-fed to 400 kg BW with (Z1) or without (ZO) zeranol implants. Ten steers were slaughtered at the end of Period 1 to estimate carcass composition. Differences of 100 kg in BW were achieved by restriction in Period 1. Subsequent to restriction, cumulative ADG remained greater (P less than .05) up to the 24th wk of recuperation and implants increased (P less than .001) BW gain by 31% and 24% for RO and R1, respectively. The average daily energy intake (ME/W(.75) in Period 2 was similar for all treatments. Feed conversion was improved by 21.5% (P less than .05) by implants. At the end of Period 2 the R1ZO had 8.6 kg less muscle (P less than .001), 2.9 kg less bone (P less than .001) and 5.9 kg more fat (P less than .05) than the ROZO. In comparison, the carcasses of the implanted animals did not show significant differences (P greater than .05) due to restriction. Carcass daily gains were increased by previous restriction (P less than .01) and implants (P less than .05). Zeranol increased daily live weight gain and feed conversion in animals in continuous growth as well as in those observed in compensatory growth an tended to eliminate a tendency for higher content of fat in carcasses of nonimplanted animals making compensatory growth.     

Myostatin allelic status interacts with level of nutrition to affect growth, composition, and myofiber characteristics of lambs

The objective of this experiment was to determine if growth, carcass composition, and myofiber characteristics of lambs were affected by heterozygosity for a myostatin mutation (g+6723G>A) when offered differing allowances of feed administered with or without ractopamine. Heterozygote [MSTN A/G (n = 40)] and homozygote wildtype [MSTN G/G (n = 39)] castrate male lambs were individually fed ad libitum (HI; 1.8 × estimated ME(m)) or a restricted allowance (LO; 1.1 × estimated ME(m)) of a diet (191 g of CP/kg of DM and 12 MJ of ME/kg of DM), supplemented with (0.4 mg/kg of BW) or without the β-adrenergic agonist ractopamine (RAC or NO RAC) for 47 d. The lambs were scanned by computed tomography at the beginning and completion of the feeding experiment to calculate composition of lean, fat, and bone in the carcass component of the body. The MSTN A/G HI intake lambs had significantly greater total daily carcass growth (P = 0.045) and loin eye depth (P = 0.022) and tended to have a greater daily growth of lean (P = 0.09) in the carcass, compared with MSTN G/G HI intake lambs. Conversely, MSTN A/G LO intake lambs tended to have less daily lean deposition (P = 0.09), significantly less total daily carcass growth (P = 0.045), and had a greater percentage of type IIX myofibers (P < 0.01) and total myofiber area (relative area) of type IIX myofibers (P = 0.013). The inclusion of RAC increased final BW (P = 0.03) and ADG (P = 0.02), percentage of type IIC (P < 0.001) and IIA (P = 0.012) myofibers, cross-sectional area of types I (P = 0.04) and IIAX (P = 0.04) fibers, and the relative area of type IIC (P = 0.003) and IIA (P = 0.01) myofibers in the LM. The experiment demonstrated that including RAC in the diet of lambs increased final BW and ADG, but not HCW, and increased proportion of type IIC and IIA myofibers and cross-sectional area of type I and IIAX myofibers. Our data suggest that RAC and the heterozygous myostatin mutation act together to increase growth of muscle on a high plane of nutrition. The experiment also demonstrated that poor nutritional background of lambs heterozygous for the myostatin mutation may negatively influence their growth rates and myofiber characteristics.     

Interaction between energy level in the diet and environmental temperature on the utilization of energy in growing pigs

Thirty-two pigs weighing approximately 50 kg were maintained in respiration chambers to measure their heat production and the partition of energy retention between protein and fat deposition at two environmental temperatures (23 and 13 C) and with two energy levels in the diet: 3.39 (HE) and 2.92 (LE) Mcal ME/kg. From energy balance data, maintenance requirements (MEm) and the efficiency (k) of energy (ME) utilization for energy deposition were calculated for each treatment. For both diets, MEm averaged 122 kcal ME/kg.75 at 23 C, the rate of increase of MEm being 3.7 kcal ME/kg.75 for each 1 C decrease in the environmental temperature. At 23 C, k was higher with the HE diet (.81 vs .55) and similar for both diets (.78) at 13 C. At comparable ME intakes, heat production was higher with the LE diet at 23 C, and the rate of increase of heat production between 23 and 13 C was lower with the LE diet (1 kcal/kg.75) than with the HE diet (3 kcal/kg.75), resulting in similar heat production at 13 C for both diets. This resulted in an interaction (P less than .01) between temperature and diet on heat production. Protein retention was lower (P less than .01) at 13 C but unaffected by diet at both temperatures. This resulted in an interaction (P less than .01) between temperature and diet on fat retention. Consequently, energy of LE and HE diets was similarly utilized at 13 C, while at 23 C, the HE diet was better utilized. The comparison between these results and those obtained in growth experiments is discussed.     

Effects of dietary canola seed and soy lecithin in high-forage diets on cholesterol content and fatty acid composition of carcass tissues of growing ram lambs.

Phospholipids (soy lecithin) are important in the emulsification of lipids and may escape the rumen and influence the absorption of fatty acids in the small intestine. Our objectives were to determine the influence of dietary canola seed (high in unsaturated fatty acids) and soy lecithin in high-forage diets on total lipid content, cholesterol content, and fatty acid composition of carcass tissues. Forty-three Hampshire or Suffolk-sired ram lambs were weaned at 60 d of age (average 23.6 kg of BW) and assigned to a 2 x 2 factorial arrangement of treatments consisting of 1) basal diet (control = BAS), 2) BAS with 6% whole canola seed (CS), 3) BAS with 4.9% deoiled soy lecithin (SL), and 4) BAS with 6% CS and 4.8% SL (CSSL). The BAS diet consisted of 70% forage and 30% concentrate and contained 15% CP and 2.2 Mcal of ME/kg. Lambs were individually fed and given ad libitum access to feed to an average final BW of 52.1 kg. Longissimus muscle (LM) from the left side of each carcass posterior to the 13th rib (12 to 15 cm in length) was excised and the lean (LM) and corresponding subcutaneous (s.c.) adipose tissue were separated, frozen, and later used for lipid analysis by gas-liquid chromatography. In lean tissue, feeding lambs CS reduced (P less than .01) the proportion of total polyunsaturated fatty acids (PUFA) and feeding SL increased (P less than .01) the proportion of total PUFA. In s.c. adipose tissue, lambs fed CS had lower (P less than .01) saturated fatty acids (SFA) and lambs fed SL had increased (P less than .03) PUFA.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of diet forage:concentrate ratio and metabolizable energy intake on visceral organ growth and in vitro oxidative capacity of gut tissues in sheep

We used 28 crossbred wether lambs to determine the effects of dietary forage:concentrate ratio and metabolizable energy intake on visceral organ growth and oxidative capacity of gut tissues in lambs. Lambs were assigned randomly to a factorial arrangement of dietary treatments consisting of pelleted diets containing either 75% orchardgrass or 75% concentrate fed once daily at either .099 or .181 Mcal ME x (kg BW(.75))(-1) x d(-1). After a 52-d feeding period, lambs were slaughtered to obtain measurements of visceral organ mass and composition and oxidative capacity of isolated epithelial cells. Lamb performance, as measured by DMI, ADG, and efficiency of gain, was greater (P = .0001) for both diets at high ME intake. Likewise, lambs fed 75% concentrate gained faster and more (P < or = .01) efficiently than lambs fed 75% forage. Total digestive tract (TDT; includes rumen, reticulum, omasum, abomasum, and intestines) weight increased (P = .0001) with ME intake and was greater (P = .03) in lambs fed 75% forage than in those fed 75% concentrate. As a percentage of empty body weight (EBW), TDT weight increased with ME intake in lambs fed 75% forage, but it was unaffected by ME intake in lambs fed 75% concentrate (diet x intake, P = .03). Liver weight increased (P = .0001) with ME intake and was greater (P = .005) in lambs fed 75% concentrate vs 75% forage; however, liver weight as a percentage of EBW was increased (P = .0002) with ME intake but was unaffected by diet. Greater ME intake increased (P < or = .02) small intestinal (SI) epithelial and muscle mass of 15-cm sections, whereas jejunal epithelial mass was greater (P = .01) for lambs fed 75% forage vs 75% concentrate. Rumen epithelial concentrations of DNA and RNA increased (P < or = .02) with greater ME intake, whereas SI concentrations of DNA and RNA were largely unaffected by diet or ME intake. The activity of Na(+)-K(+)-ATPase increased in ileal epithelium (P < or = .02) with ME intake and concentrate in the diet, but activity in ruminal epithelium increased (P = .05) with concentrate. Total oxygen consumption by isolated ruminal and intestinal epithelial cells was unaffected by treatment. These data suggest that ME intake and level of dietary forage affect ruminal and intestinal growth via changes in cellular hyperplasia. Additionally, this study supports the concept that ME intake and diet composition alter gut energy expenditure, at least in part, through changes in mass rather than mass specific metabolism.     

Effects of recombinant porcine somatotropin on metabolic rate in growing pigs

Effects of recombinant porcine somatotropin (rpST) on metabolic rate were studied in two trials with 24 crossbred barrows (Yorkshire x Landrace) in each. The barrows weighed about 80 kg (SE within trials 2.2 kg) at the start of the measurements and in each trial 12 pigs received 4 mg of rpST and 12 received a placebo. The diet contained 2.57 Mcal NE/kg and 20% CP (about 1% lysine). Animals were fed approximately 2.8 times maintenance (280 kcal ME.kg-.75.d-1). Heat production (gaseous exchange of CO2 and O2) and activity were measured continuously. Heat production associated with activity was calculated from the regression of heat production on activity. Animals treated with rpST exceeded controls in rate of gain by 252 g/d (P less than .001) and in metabolic rate by 14.5 kcal.kg-.75.d-1 (P less than .01). The rpST treatment increased rectal (+ .2 degrees C) and surface (+ .8 degrees C) temperatures. Activity-related heat production in treated pigs was increased, but this was only partly related to the increase in metabolic rate with rpST. The daily patterns of total and activity-related heat production were similar between pigs in both experimental treatments.     

Reduced calcium-dependent proteinase activity in cimaterol-induced muscle hypertrophy in lambs

The purpose of this study was to reveal the possible relationships between total Ca2+-dependent proteinase (CDP) and micromolar-Ca2+-dependent proteinase (microM CDP) activity and cimaterol-induced hypertrophy of skeletal muscle. Dietary administration of 10 ppm cimaterol to finishing lambs reduced microM CDP activity in longissimus muscle (LD) by 55% (P less than .01) and 70% (P less than .02) after 3 and 6 wk of treatment, respectively. Total CDP activity was unaffected by cimaterol at both treatment intervals. The reduced microM CDP activity was not associated with a reduced yield of enzyme extract from the muscle. Cimaterol treatment increased the cross-sectional area of the LD by 23.5% at 3 wk and by 35.6% at 6 wk (P less than .001). Cimaterol also increased (P less than .001) the masses of semitendinosus, semimembranosus and biceps femoris by 26%, 32.4% and 24.5%, respectively. These results suggest that cimaterol-induced muscle hypertrophy may be attained in part by reduction of myofibrillar protein degradation.     

Energy components of growth in Holstein steers fed formaldehyde- and formic acid-treated alfalfa or orchardgrass silages at equalized intakes of dry matter

Energy retention was compared in Holstein steers fed either alfalfa or orchardgrass silages for 164 d at either 65 or 90 g DM/kg.75 BW daily in a 2 x 2 factorial. Energy retention was estimated by slaughter-balance using an initial kill of eight steers at 216 kg and a final kill of eight steers per treatment at 326 kg. The ADG was not affected (P greater than .05) by silage, but steers fed alfalfa gained less (P less than .001) gut fill (they lost gut fill) and gained more (P less than .001) of the following than steers fed orchardgrass: empty body, 23%; fat, 50%; fat-free matter, 18%; protein, 16%; water, 17%; ash, 43%; gross energy, 31%; and carbon, 38%. With retained energy at 1.15 Mcal/d, retained energy was equally distributed between fat and protein. Increments of daily retained energy greater than 1.15 Mcal were deposited as 76% to fat and 24% to protein; this distribution was not affected by silage. The energy requirement for maintenance, with BW adjusted to equal gut fill, was not different (P greater than .05) at 130 kcal ME/kg.75 BW for steers fed alfalfa vs 125 for steers fed orchardgrass. Although not significant (P greater than .05), retained energy/ME intake above maintenance was 13% greater for steers fed alfalfa (.261) than for steers fed orchardgrass (.230), which supports the difference observed by calorimetry. The difference in dietary protein (25.6 vs 20.5%) did not contribute to the difference in energy retention because the differences in fat and protein retention could be explained totally by differences in daily energy deposition. The higher NDF of orchardgrass, or other fiber components, seems to be the most probable cause of its somewhat lower partial energetic efficiency relative to alfalfa.     

Effect of propionate level in a volatile fatty acid salt mixture fed to lambs on weight gain, body composition and plasma metabolites

Chopped hay supplemented with a volatile fatty acid salt mixture at 20% of metabolizable energy (ME) was fed to 30 Suffolk X Corriedale lambs (mean wt 29.6 kg) to determine the effects of dietary propionate on weight gain, body composition and plasma metabolites. Propionate accounted for 0, 25, 50, 75 or 100% of the salt mixture energy, and acetate accounted for the remainder. Each diet was fed at two levels of daily intake (158.7 and 130.6 kcal ME/W.75). Lambs on the high level of intake lost more (P less than .05) energy in feces, lost less (P less than .05) energy in CH4 and had carcasses with more (P less than .10) water and fat than lambs on the low intake level. Percentage of propionate in the salt mixture had no effect on ME or body composition of lambs. Increasing the percentage of propionate in the salt mixture increased plasma propionate in blood samples taken at 1 and 2 h after feeding (linear, P less than .05). Empty body weight gain per megacalorie of ME above maintenance increased as the percentage of propionate in the salt mixture increased, but not until propionate reached 75% of the salt mixture (linear, P less than .05; cubic, P less than .05). These results show that propionate in the blood has a positive, but nonlinear, effect on weight gain, even when energy intake is held constant.     

Effects of growth hormone-releasing factor and feed intake on energy metabolism in growing beef steers: whole-body energy and nitrogen metabolism.

Effects of growth hormone-releasing factor (GRF) on energy and N metabolism in six growing Hereford x Angus steers were measured using a split-plot design with 4-wk injection periods within 8-wk intake periods. Steers were fed a 75% concentrate pelleted diet at two intakes (low: 50 g/BW.75 and high: 90 g/BW.75 as fed) and injected s.c. with saline or 10 micrograms/kg of BW of human GRF(1-29)NH2 twice daily for 3 wk. Measurements of energy and N balance were obtained during wk 3 of treatments. Diet DM digestibility (%) was decreased by greater intake (P less than .05) and increased by GRF (P less than .06). Treatment with GRF increased (P less than .01) N retention by decreasing (P less than .05) fecal and urinary excretion: N retention averaged 10.0 and 20.8 g/d at low intake and 25.9 and 46.7 g/d at high intake for control- and GRF-treated steers, respectively. Increased ME (P less than .05) in GRF-treated steers also resulted from decreased fecal (P less than .05) and urinary (P less than .07) energy excretion but was countered by increased (P less than .06) heat energy (HE). Tissue energy (TE), partial efficiency of ME use for TE retention, and estimated maintenance energy were not affected (P greater than .10) by GRF treatment. In summary, GRF treatment altered the partition of TE by increasing protein retention (108 and 80% for low and high intake, respectively) at the expense of fat retention.     

Effect of recombinant porcine somatotropin on energy and protein utilization by growing pigs: interaction with capacity for lean tissue growth.

Three litters of four pigs from each of four different groups were used to evaluate the effect of porcine somatotropin (pST) on growth performance, body gain composition, energy and N metabolism, and in vitro cytochrome oxydase (final enzyme of the respiratory chain) activity of tissues. The four groups included boars from a synthetic line (SG1) or the Large White breed (SG2) and barrows from the Large White breed (SG3) or crossbred between Large White and Meishan breeds (SG4). Inherent capacity for daily lean tissue growth (LTG) decreased from SG1 to SG4. Within a litter, one pig was slaughtered and dissected at the beginning of the experiment (55 kg BW) and the three others were fed the same daily supply of protein and amino acids (26 g of lysine/d) but relative daily energy levels were either 113 (without pST: E1/0), 100 (3 mg of pST/d: E2/pST) or 87 (3 mg of pST/d: E3/pST). The 100 energy level corresponded to the ad libitum intake of E2/pST pigs. Two energy and N balances were carried out in respiration chambers during the experimental period. Pigs were slaughtered and dissected at approximately 95 kg BW and composition of gain was estimated using the comparative slaughter technique. In E1/0 pigs, daily BW, lean, and N gain were affected (P less than .01) by group; 566, 471, 374, and 315 g/d of lean tissue gain in SG1, SG2, SG3, and SG4 pigs, respectively. At high ME intake (E2/pST vs E1/0), pST increased daily BW (+14%), lean (+27%), or N (+26%) gain and reduced adipose tissue (-50%) gain, but the pST effect was inversely related to LTG: for N, the improvement was 2.8, 7.1, 7.0, and 11.1 g/d in SG1, SG2, SG3, and SG4 groups, respectively. Energy restriction (E3/pST vs E2/pST) reduced (P less than .001) adipose tissue gain in all groups but did not affect lean tissue or N gains in SG1, SG2, and SG3 pigs. In the pST-treated pigs of the SG4 group, the lean tissue or N gains were reduced (P less than .01) by energy restriction. Energy restriction combined with pST treatment (E3/pST) led to negligible amounts of fat deposited (40 g/d for SG1 + SG2 + SG3 pigs) and a gain:feed ratio higher than 500 g/kg (580 in SG1 pigs). The increased heat production measured in pST-treated pigs was due to its maintenance component: 275 vs 257 kcal of ME.kg BW-.60.d-1 (P less than .01).(ABSTRACT TRUNCATED AT 400 WORDS)     

Energy source and ionophore supplementation effects on lamb growth, carcass characteristics, visceral organ mass, diet digestibility, and nitrogen metabolism.

In Exp. 1, 72 Targhee lambs (initial BW 22.1+/-.3 kg) were used to determine the effects of energy source (alfalfa pasture vs limit-fed, all-concentrate) and ionophore addition on performance, visceral organ mass, and carcass characteristics. There were no differences (P > . 10) in ADG or gain/ feed due to ionophore supplementation. Lambs that grazed alfalfa had greater (P < .05) liver, omasum, abomasum, small intestine, cecum, and large intestine weights than did lambs fed the concentrate diet. Lambs fed the concentrate diet had greater (P < .01) hot carcass weights, larger (P < .01) loin eye areas, and greater (P < .001) dressing percentages than lambs that grazed alfalfa. In Exp. 2, lambs offered the concentrate diet had greater (P < .001) DM and OM digestibilities than lambs offered alfalfa (89.5 and 91.1 vs 72.4 and 74.2%, respectively). Apparent and true N digestibilities were greater (P < .001) for the concentrate diet than for alfalfa (90.9 and 101.7 vs 77.7 and 91.9%, respectively). Likewise, grams of N retained per day were twice as great (P < .001) with the concentrate diet than with alfalfa (14.9 vs 6.0 g/ d). The greater visceral organ mass and resulting increases in energy and protein requirements in lambs that grazed alfalfa were probably responsible for the lesser hot carcass weight and dressing percentage compared with lambs fed 100% concentrate.     

Effects of diet forage:concentrate ratio and metabolizable energy intake on isolated rumen epithelial cell metabolism in vitro

Crossbred wether lambs were used to assess the effect of altered forage:concentrate ratio and metabolizable energy intake on metabolism of substrates by ruminal epithelium using an isolated cell system. Lambs (n = 28; 20.1 +/- 3 kg BW) were assigned randomly to a factorial arrangement of dietary treatments consisting of either 75% forage or 75% concentrate fed once daily at either .099 or .181 Mcal ME x(kg BW(.75))(-1) x d(-1) for 52 d. After a 52-d feeding period, isolated rumen epithelial cells (IREC) were incubated in the presence of an oxidizable substrate with a single 14C label (acetate, propionate, butyrate, glucose, glutamate, and glutamine) at concentrations ranging from .1 to 50 mM, and substrate oxidation to 14CO2 or metabolism to beta-hydroxybutyrate (beta-HBA), acetoacetate, pyruvate, and lactate was determined. For all substrates, oxidation to CO2 was concentration-dependent and saturable within the physiological range. Differences in substrate oxidation to CO2 by IREC at specific substrate concentrations did not affect Vmax (maximal rate of substrate oxidation, nmol oxidized to CO2 x 1 x 10(6) cells(-1) x 90 min(-1)) and K(ox) (concentration of substrate at which half Vmax oxidation rate is achieved, mmoles/L) estimates for the dietary treatments. Production of beta-HBA from butyrate by IREC from the lambs fed 75% forage was not affected by ME intake; however, production was elevated by high ME intake of the 75% concentrate diet (diet x intake interaction; P < .02). Acetoacetate production from butyrate by IREC from lambs fed at high ME intake was greater (P = .001) than from those fed at low ME intake. Lactate and pyruvate production from glucose, glutamate, and propionate were generally unaffected by dietary treatment; however, rate of glutamine metabolism to lactate and pyruvate by IREC was increased with increased ME intake. The observed changes in metabolite production rates across groups did not affect the predicted Vmax and K(ox) parameter estimates. The estimated K(ox) values corroborate that VFA are the primary oxidizable fuels used by ruminal epithelial cells while illustrating that other substrates such as glucose, glutamate, and glutamine would not be expected to be oxidized extensively in vivo due to the high K(ox) relative to substrate concentrations in vivo. In conclusion, the capacity of isolated ruminal epithelial cells to oxidize substrates was largely unaffected by ME intake or dietary forage:concentrate ratio of the diet.     

Energy requirements of Texel crossbred lambs

Two trials were conducted to determine the energy requirements of feedlot Texel crossbred lambs. In a comparative slaughter trial, thirty 11/16 Texel x 5/16 Ile de France crossbred noncastrated male lambs, weaned at 42 d of age (16.2 +/- 2.1 kg of shrunk BW; SBW), were used. Five lambs were randomly chosen and slaughtered after 10 d of experimental management and diet adaptation (baseline group). Fifteen lambs then were fed for ad libitum intake and slaughtered at 25, 30, or 35 kg of SBW. The remaining 10 lambs were randomly assigned to 2 levels of DMI, either 70 or 55% of the ad libitum intake, and were slaughtered concomitantly with lambs of the 35 kg of SBW group. Total body N, fat, and energy contents were determined. In a digestibility trial, 6 Texel x Ile de France crossbred lambs (30.4 +/- 2.6 kg of SBW) were housed in metabolic cages and used in a replicated 3 x 3 Latin square experiment to evaluate the energetic value of the diet at different feed intake levels. Net and ME requirements for maintenance were 58.6 and 91 kcal/kg(0.75) of SBW, respectively. Consequently, partial efficiency of energy use for maintenance was 0.64. Body fat content varied from 72.7 to 125.9 g/kg of empty BW, respectively, for 13.1 and 28.2 kg of empty BW. Net energy requirements for growth of lambs at 15 and 35 kg of SBW at an ADG of 250 g were 424 and 553 kcal/d, respectively. Partial efficiency of energy use for growth was 0.47. Texel x Ile de France crossbred growing lambs used in this study showed decreased nutritional requirements than those reported by most nutritional systems.     

Postweaning growth, feed efficiency and chemical composition of sheep as affected by prenatal and postnatal testosterone

Data were collected from intact males, castrated males and ewe lambs to investigate the effect of presence or absence of testosterone prenatally and during the postweaning period on postweaning growth, feed intake and carcass chemical composition. Half the lambs from each sex were the progeny of dams that had received five injections of testosterone cyprionate from d 32 through d 87 of gestation. Linear contrasts were used to detect differences. Postweaning daily gain of intact males was greater (P less than .01) than that of male castrates. Ewe lambs from treated dams had approximately 12% greater rate of growth (P less than .04) than ewe lambs from control dams. Ewe lambs from dams that had been treated were 28% more efficient (P less than .01) in the conversion of food to weight than those from untreated dams. Ewe lambs from treated dams had heavier livers (P less than .07). Carcass protein for intact males was greater (P less than .11) than for castrates, and extractable fat was less (P less than .05). Masculinization of growth characteristics of ewe lambs affected the quantity of carcass fat relative to control ewes (7.59 vs 8.92 kg). These ewe lambs also had more water in the carcass than did the control ewes (13.93 vs 12.29 kg). Administration of exogenous testosterone to pregnant ewes over an interval of time approximating time of sexual differentiation in the fetus enhances postweaning growth rate, feed conversion efficiency and chemical composition of genetic females.