Wether Lambs Research Articles

The effect of post-ruminal infusion of protein or energy on the pathophysiology of Trichostrongylus colubriformis infection and body composition in lambs

The effect of post-ruminal infusion of protein or energy on the pathophysiology of Trichostrongylus colubriformis infection and body composition in lambs was investigated using the comparative slaughter technique. Of 52 Dorset DownxCoopworth wether lambs (mean body weight 30.5, s.e. 0.44 kg), 8 comprised an initial slaughter group (IC), 36 were infected daily, per os, with 3000 Trichostrongylus colubriformis larvae per animal, and the remainder (C) were parasite-free controls. Groups of 12 infected animals were given either a continuous infusion (via abomasal catheter) of 50.4 g/day crude protein as sodium caseinate (PI), glucose (EI) in isocaloric amounts to PI, or a solution containing P and Na at the same rate as the caseinate infusions (SI). Uninfected controls (C) were also infused with this solution. Animals were slaughtered after 6 and 12 weeks for estimation of worm count and body composition. All animals were offered, ad libitum, meadow hay (118 g crude protein/kg dry matter (DM); 930 g organic matter/kg DM; 0.65 organic matter digestibility). DM intake of infected animals decreased by approximately 22% in PI and EI and by 32% in SI animals. Mean total metabolizable energy (ME) intake during the experiment (inclusive of infusions) was C, 0.607; PI, 0.687; EI, 0.704; SI, 0.617, s.e.d. 0.0308 MJME (kg W)-0.75 day-1. Nitrogen retention in infected sheep was increased fourfold by protein infusion and twofold by energy infusion. The rate of energy retention was reduced by infection, increased by protein infusion but only partly by energy infusion. Protein infusion reduced mean faecal egg output and mean total parasite count. Increased endogenous plasma loss into the gastrointestinal tract was similar in all infected groups. It was concluded that a major limiting factor in efficient food utilization in animals with gastrointestinal nematode infections is a parasite-induced protein rather than energy deficiency, possibly the result of increased endogenous protein losses into the gastrointestinal tract. The debilitating effect of internal parasites could be markedly reduced by increasing duodenal protein supply.

Nutrient utilization by sheep fed forage grown on soil treated with fluidized-bed combustion residue.

A mineral balance trial was conducted with 18 wether lambs fed sun-cured hay harvested from pastures located on a reclaimed strip-mined site. The following soil applications were made during each of 3 yr: 1) none, 2) dolomitic limestone and 3) fluidized-bed combustion residue (FBCR). Because FBCR had half the buffering capacity of limestone, it was applied at twice the rate of limestone. Apparent digestibility of hemicellulose was higher (P less than .05) for limestone-amended forage than for FBCR-amended forage (70.2 vs 67.0%), and apparent digestibility of cellulose was higher (P less than .05) for amended forages (66.7%) than for the control (63.9%). Apparent absorption and retention of N were similar among treatments, when expressed as a percentage of intake. Lambs fed control forage were in negative Ca balance, lower (P less than .01) than with amended forages. Apparent absorption and retention of Mg and Fe (g/d basis) were higher (P less than .05) for lambs on the limestone treatment than for lambs on the FBCR treatment. Apparent absorption of S was higher (P less than .01) for lambs on the FBCR treatment than for those on the limestone treatment. These differences were related to differences in mineral concentrations of the forages. Serum P was lower (P less than .05) for lambs fed FBCR-treated forage than for lambs fed limestone-treated forage (10.1 vs 12.9 mg/dl). Soil amendment with FBCR did not have deleterious effects on digestibility or mineral metabolism; in fact, it may have enhanced utilization of Ca and S and improved digestibility of some fiber components by lambs.

Effects of animal-to-animal exchange of ruminal contents on the feed intake and ruminal characteristics of fed and fasted lambs.

Four Suffolk x Hampshire wether lambs averaging 55 kg with permanent ruminal cannulas were used in a 4 x 4 Latin square design to determine the effects of exchange of ruminal contents between fed and fasted lambs on subsequent DMI and ruminal characteristics. Lambs were fed a pelleted 70% roughage diet at 2% of BW for 17 d. During each period of the Latin square two lambs were deprived of feed and water for 3 d. At the end of the fasting period ruminal contents from one fed and one fasted lamb were exchanged. Lambs were then given ad libitum access to feed for 8 d, during which DMI, feeding pattern, and ruminal characteristics were monitored. Measurements of ruminal volume determined by total collection and indigestible marker (lithium sulfate) suggested that only about 50% of total ruminal contents were actually exchanged. Fasted lambs had lower (P less than .05) DMI, ruminal fermentative capacity, ruminal DM weight, and ruminal DM percentage than fed lambs during the first 4 d of realimentation. Exchange of ruminal contents did not (P greater than .10) affect DMI, feeding pattern, ruminal fluid pH, ruminal fermentative capacity, ruminal contents DM percentage, ruminal nucleic acid concentration, or VFA. Dosing fasted lambs with ruminal contents from nonfasted lambs reduced (P less than .05) ruminal liquid volume, dry weight of ruminal contents, and propionate concentration. Results of this trial are interpreted to indicate that although decreased ruminal function is a factor in the low feed intakes of fasted ruminants, the possibility of increasing postfast feed intake via improved ruminal function is limited because other metabolic factors may play a more important role.

Apparent digestibility and nutrient balance in lambs fed different levels of flatpea hay.

Apparent digestibility and nutrient utilization were studied in a digestion and balance trial with 30 wether lambs (BW 32 kg). Lambs were blocked by weight and allotted randomly to five diets with ratios of alfalfa (Medicago sativa L.) to 'Lathco' flatpea (Lathyrus sylvestris L.) hay of 100:0, 75:25, 50:50, 25:75, and 0:100. Alfalfa was harvested in the early bloom stage and flatpea was harvested in the vegetative stage. Digestibilities of DM, NDF, ADF, cellulose, hemicellulose, and energy decreased linearly (P less than .05) as the level of flatpea hay increased to values of 53.3, 32.4, 39.9, 46.0, 40.5, and 52.5%, respectively, for 100% flatpea hay. Nitrogen retention (9 to 15% of intake) was not affected by level of flatpea hay. Ruminal pH, NH3 N, and blood urea N increased linearly (P less than .001) as level of flatpea increased in the diet, apparently a reflection of dietary N level. Calcium excretion decreased linearly (P less than .01) with increased proportions of flatpea hay and was related to dietary intake of Ca. Apparent absorption and retention showed a cubic effect (P less than .05). No clinical signs of toxicity were observed in any of the lambs during the 20-d metabolism trial. Vegetative flatpea is potentially valuable as a forage for feeding ruminants.

IMMUNIZATION OF LAMBS AGAINST SOMATOSTATIN TO IMPROVE GROWTH RATE

Weight gain, shoulder height and feed intake responses to immunization against somatostatin (SRIF) were examined in three experiments with a total of 78 lambs. Initial immunizations against SRIF occurred when lambs were 4, 8 and 3 wk old for exps. 1, 2 and 3, respectively, with booster immunizations 2, 4, 6, 8 and 10 wk later. Control lambs were left untreated except in exp. 3 where one group of control lambs was immunized with human serum alpha globulin. Treated lambs were immunized with SRIF conjugated to human serum alpha globulin. Experiments were terminated when lambs reached 45 kg body weight. SRIF immunization did not alter lamb shoulder height or feed conversion efficiency. Rate of gain of ram and wether lambs, but not ewe lambs, was improved by SRIF immunization. Wether lambs in exp. 1 and ram lambs in exp. 2 gained 21 and 15% more, respectively, than their controls by 20 wk of age. In exp. 3, SRIF-treated 3/4 Romanov ram lambs gained 13% more than their controls by 19 wk of age. However, SRIF-treated 7/8 Romanov lambs gained only 3% more than controls during this time. In conclusion, immunizing wether and ram crossbred lambs against somatostatin increased their growth rates sufficiently to reduce the time needed to reach market weight by 2–3 wk. However, feed conversion efficiency was not improved by somatostatin immunization. Key words: Somatostatin, SRIF, immunization, growth rate, lambs

Exogenous human growth hormone-releasing factor and ovine somatotropin improve growth performance and composition of gain in lambs

The objectives of this study were 1) to compare intermittent subcutaneous administration of human growth hormone-releasing factor (hGRF) at two doses with a similar regimen of ovine somatotropin (oST) for effects on growth and composition of gain in growing lambs and 2) to determine whether increasing the dietary amino acid availability enhances response to oST or hGRF. Eighty crossbred ewe and wether lambs (25.5 kg live weight) were assigned randomly in pairs to receive four daily injections of excipient, 40 micrograms oST/kg BW, 5 micrograms hGRF/kg BW or 10 micrograms hGRF/kg BW for 42 (n = 80) or 56 (n = 40) d. Doses were adjusted weekly for BW. Mean plasma oST concentrations increased from 2.03 ng/ml prior to treatment to 20.64, 4.80 and 5.45 ng/ml with oST, 5 and 10 micrograms/kg hGRF doses, respectively. Lambs did not become refractory to hGRF. Cumulative gain increased approximately 18% with 7 wk of treatment with oST and the low dose of hGRF (both P less than .01), and feed efficiency improved 21% with oST and 18% with both doses of hGRF (both P less than .05). Carcass lipid accretion rate decreased 22% to 30% (P less than .001), and carcass protein accretion rate increased 30% to 36% (P less than .001) with hGRF and oST treatment, respectively. Addition of fishmeal to the diet at 4% to replace an equal amount of soy protein improved gain 8.5%; it improved efficiency 14.2% (P less than .05) across all treatments, and it significantly enhanced the effects of oST on feed efficiency (interaction P less than .12) and hind leg muscle weights.

Muscle protein synthesis in response to testosterone administration in wether lambs

A method has been developed based on stable isotopes and biopsy procedures which allows the large-dose procedure for measurement of protein synthesis to be applied in serial studies to farm species. Measurements of total nitrogen retention and protein synthesis in m. longissimus dorsi and m. vastus lateralis were made in five wether lambs (40-44 kg) infused intravenously, successively, with vehicle (10 d); testosterone (15 d; 9 mg/d); vehicle (15 d). N retention was improved by testosterone infusion (+2.9 g N/d; a 96% improvement total over control periods). Muscle protein synthesis was not significantly altered by exogenous hormone administration, nor were RNA:protein, RNA:DNA or protein:DNA. The implication of the developed procedure for dynamic studies in accessible tissues of large animals is discussed.

Responses of young and mature wethers exposed to micromist cooling in feedlot environments

The responses of young and mature wethers to different cooling/housing environments were studied. In the first trial, 180 wether lambs were housed in closed or open pens. In the second, both young and mature wethers (60 of each) were housed in conventional feedlot sheep pens. Micromist cooling was installed in both types of shed. Although mist cooling considerably reduced ambient temperatures in open and closed animal pens, there was no significant improvement in live weight gains in lambs in the first experiment. Mist cooling in conventional sheep sheds resulted in a significant improvement in live weight gains. The young wethers were found to be more sensitive to heat stress than the mature.

Factors affecting food efficiency and body composition of growing ruminants offered straw-based diets: supplementation with lipids with and without protein meal

ABSTRACTGrowing heifers (experiment 1) and wether lambs (experiments 2 and 3) were offered ammoniated cereal straw with or without a protein meal. The effects of supplementation with long-chain fatty acids (LCFA; as calcium salts of LCFA (CaLCFA) or fat prills) on nutrient utilization were studied.Intake of the basal diet (g/kg live weight) was unaffected by the protein meal, but was often reduced by supplementation with LCFA, especially fat prills. Live-weight gain was increased both by supplementation with protein meal and CaLCFA. Fat prills only increased live-weight gain in the presence of protein meal and depressed live-weight gain in the absence of protein meal. There were small differences between the two sources of LCFA in their apparent effects on rumen fermentation.Supplementation with protein meal increased relative protein content (P < 0·05) and tended to increase water content (P > 0·05) in the wethers in experiment 3 (corrected to equal empty-body weight at slaughter). Of the LCFA, only CaLCFA tended to increase relative body fat content (by proportionately 0·23; (P > 0·05) but decreased relative protein and water content by 0·05 and 0·06 (P < 0·05).Supplementation of straw-based diets with as little as 20 g CaLCFA per kg food dry matter improved live-weight gain and efficiency of nutrient utilization of ruminants, particularly when offered in combination with a protein meal. There appeared to be marked differences in the effects of CaLCFA and fat prills on food intake, productivity and to some extent body composition.

The effect of cimaterol and oestradiol-17β alone or combined on growth and body composition of wether lambs

ABSTRACTTwenty-four Finn ♂ × Dorset Down ♀ wether lambs about 10 weeks and weighing on average 18 kg were allocated to treatment groups as follows: untreated controls (U); 15 mg oestradiol-17β (OE) implanted subcutaneously (O); cimaterol (2 mg/kg dry matter (DM)) in the diet (C); and 15 mg OE implant + cimaterol (2 mg/kg DM in the diet) (OC). The lambs were offered a diet, restricted to 38 g/kg live weight (LW), and which contained an estimated 12·5 MJ metabolizable energy and 137 g crude protein per kg DM for the experimental period of 62 or 63 days. Comparisons were made for the main effects of OE and cimaterol and also interactions between OE and cimaterol. Treatment with OE, on average, resulted in greater LW gain, DM intake, empty body weight (EBW), body length and chest depth, weight of shoulder and loin joints and carcass crude protein, but had no effect on fat deposition in carcass or depots. As a proportion of EBW, the weights of the pituitary gland and accessory vesicular glands were increased, as was teat length in lambs treated with OE. Cimaterol treatment, on average, increased LW gain, EBW, killing-out ratio, carcass weight and its weight of crude protein and, unlike OE, decreased the weight of the pituitary gland as a proportion of EBW and reduced the weight and proportion of fat in the carcass and perirenal and retroperitoneal depots. Increases in the cross-sectional area of m. longissimus dorsi and in the weight of selected major and minor commercial joints were also obtained in cimaterol-treated lambs. The presence of significant interactions indicated that there was incomplete or no additivity between the effects of cimaterol and OE for LW gain, cross-sectional area of m. longissimus dorsi and weights of carcass and carcass crude protein, omental fat and of certain of the dissected joints. These results suggest either that the mechanisms of action of oestradiol-17β and cimaterol are not independent or that they are affected by similar metabolic or physiological processes which limit the ability of castrated male sheep to exhibit a positive response.

THE EFFECTS OF SHEARING AND RALGRO IMPLANTS ON FEEDLOT PERFORMANCE OF LAMBS DURING THE SUMMER

To evaluate the effects of shearing and Ralgro® implants on the performance of fast-gaining feedlot lambs during the summer, 84 group-fed crossbred wether lambs (34.8 ± 1.8 kg) were shorn on day 0 of the feeding period (ES), shorn 3 wk later (LS), or left unshorn (NS), and either implanted with 12 mg Ralgro on day 0 (R) or not implanted (C). Lambs were blocked by initial weight. Heavy and light pens of lambs were shipped to market when the average weight within a pen was 52 kg after 40 and 55 d, respectively. Between days 0 and 40, mean average daily gain (ADG) of all lambs was 384 g and feed conversion was 4.38 kg dry matter kg−1 gain. During the first 40 d of the feeding period, shearing did not affect ADG (P > 0.05), but ES lambs had higher feed intake and poorer feed conversion than NS lambs (P < 0.05). Performance of the LS lambs was similar to the NS lambs prior to shearing, and similar to the ES lambs after shearing. A delay period between implantation and growth response was observed. Ralgro did not affect ADG between days 0 and 21 (P > 0.05) but improved ADG by 14.2% between days 21 and 40 (P < 0.01), giving an overall growth improvement of 6.5% between days 0 and 40 (P < 0.06). Ralgro had no effect on ADG after day 40. There were no interactions between the effects of shearing and Ralgro implantation on ADG (P > 0.05). Key words: Lambs, shearing, Ralgro, feedlot, summer

Level of nutrition and visceral organ size and metabolic activity in sheep

Thirty-two crossbred wether lambs (initial live-weight 31 kg) were fed on a diet (metabolizable energy (ME) 12.8 MJ/kg) ad lib. (ADLIB) or restricted to maintain body-weight (MAINT) for a 21 d period. On days 0, 7, 14 and 21, four lambs per treatment were slaughtered, visceral organs weighed and tissues sampled. During the 21 d period, ME intake in ADLIB lambs increased quadratically with an average rate of live-weight gain of 425 g/d. In MAINT lambs, live weight (30 kg) was maintained, and daily ME intake (kJ/kg empty body-weight (EBW)0.75) declined (P less than 0.01) quadratically with time. Weights of liver, stomach and small intestines as a percentage of EBW were increased in ADLIB lambs and decreased by 10-33% in MAINT lambs (treatment x day, P less than 0.01). In vitro liver oxygen consumption was not affected by level of feed intake. Estimates of whole-liver O2 consumption (mmol O2/d per kg EBW) increased in ADLIB lambs and were relatively constant in MAINT lambs. These findings suggest that level of feed intake changes the relative proportion of visceral organs to body mass. In addition, the effect of level of feed intake on changes in the relative contribution of visceral organs to whole-body metabolic rate appears to be primarily a result of differences in organ size rather than tissue-specific metabolic activity.

In vitro and in vivo digestibility of soya-bean straw treated with various alkalis

ABSTRACTThree trials were conducted to evaluate the effects of treating soya-bean straw with various alkalis plus ensiling on digestibility of various nutrients and on nitrogen retention in ruminants. Soya-bean straw was treated with sodium hydroxide, calcium hydroxide or ammonium hydroxide and ensiled at 650 g/kg moisture. In trial 1, the effects of level and type of alkali on in vitro digestibility of ensiled soya-bean straw were evaluated. Concentrations of alkalis used were 0 (control), 20, 30, 40 and 50 g/kg dry matter. Both in vitro digestibilities of dry matter and organic matter of soya-bean straw were significantly (P < 0·05) increased with alkali treatment at all levels plus ensiling compared with untreated or treated unensiled straw. The 40 g/kg alkali concentration level in combination with ensiling appeared to be the most effective overall. In trial 2, the effects of type of alkali on nutrient digestibility and nitrogen retention in wether lambs were evaluated. Sixteen wether Suffolk lambs were given untreated or alkali-treated (40 g/kg) ensiled soya-bean straw. Treatments were: (1) water-treated straw; (2) NaOH-treated straw: (3) Ca(OH)1-treated straw; and (4) NH4OH-treated straw. Lambs given NH4OH-treated ensiled straw digested the dry matter, organic matter, and crude protein better than those given water-treated ensiled straw (P < 0·05). NH4OH improved nitrogen intake by proportionately 0·181 but not nitrogen retention. For trial 3, eight Angus steers were used. Chopped soya-bean straw was treated with NH4OH and ensiled in Silopress bags. Treatments were: (1) untreated dry straw; (2) water-treated straw; (3) 30 g/kg NH4OH-treated straw; and (4) 40 g/kg NH4OH-treated straw. The trial consisted of a 7-day collection period which was replicated once. Apparent digestibilities of dry matter, crude protein and various fibre constituents were increased by ensiling or ensiling and NH4 OH treatment combinations (P < 0·05). Alkali treatments in combination with ensiling appeared to improve digestibility of soya-bean straw, but ammoniation did not improve nitrogen utilization. Ensiling appeared to have a more significant effect than alkali treatments per se on the degradability of soya-bean straw.

Interaction of insulin-like growth factors (IGF) with isolated sheep hepatocytes. I. Binding and degradation of IGF-I

The binding and degradation of 125I-hIGF-I by isolated sheep hepatocytes have been examined. Hepatocytes were isolated by collagenase perfusion of 32–55 kg wether lambs and were incubated at 20 or 37C at pH 7.4 in a 95% O 2/5% CO 2 atmosphere. Maximal binding was obtained at 60 min and declined slightly over the following 60-min period at both 20 and 37C. Degradation of 125I-hIGF-I by the hepatocytes was minimal with 10–12% degradation over a 120-min period at 37C. The lysosomal inhibitors chloroquine (0.2 mM), leupeptin and ammonium chloride had no significant effects on 125I-hIGF-I degradation or binding. At 20C (60-min incubation), half maximal inhibition of 125I-hIGF-I binding was obtained with 8.4 ± 1.1 nM hIGF-II, 16 ± 2.4 nM hIGF-I, 36 ± 6.2 nM oIGF-II, and 60 ± 5.9 nM oIGF-I. Ovine insulin (0.01–10 uM) had no effect on 125I-hIGF-I binding. These observations suggest that IGF-I binds to the type II IGF receptor. The low molecular weight sheep serum IGF binding protein inhibited binding of 125I-hIGF-I to hepatocytes in a dose-dependent manner with half maximal inhibition occurring at 16.5 μg/ml, but did not affect IGF-I degradation. The current studies show that IGF-I interacts with ruminant hepatocytes via type II IGF receptors. The liver is not a major site of IGF-I degradation and the observed degradation is nonlysosomal and independent of receptor interaction.

The dietary requirements of calcium and phosphorus for growing lambs

ABSTRACTGroups of wether lambs were fed on four concentrate diets, from a live weight (LW) of about 25 kg until they had grown to about 50 kg, when they were killed, minced and analysed. A fifth group was killed at the start of the trial to provide data on their initial composition. The dietary treatments were identical except in their concentrations of calcium (Ca) and phosphorus (P) and supplied, with some approximations: (A) 0·75 times the requirements for Ca and P estimated according to the recommendations of the AFRC Technical Committee on Responses to Nutrients (TCORN, 1990); (B) a close match to the estimated requirements for both elements; (C) 1·5 times the estimated requirements for both elements; (D) 1·5 times the Ca requirement and 0·75 times the P requirement.The retentions of Ca and P in the lambs were closely similar with diets B and C (6·8 and 7·3 g Ca per kg LW and 4·1 and 4·5 g P per kg LW) and significantly lower with diet A (4·8 g Ca and 3·0 g P per kg LW) and diet D (5·0 g Ca and 2·7 g P per kg LW). Parallel differences in response to diet were evident in the composition of the metacarpi. Plasma Ca and P concentrations showed no significant differences between the dietary treatments A, B and C, but plasma P concentrations were markedly depressed with lambs on diet D and plasma Ca concentrations were elevated in this group. Rumen P concentrations were also markedly lower in lambs on diet D and their food intakes and growth rates were lower than in lambs in other groups. The results indicate that Ca and P retentions were not increased by feeding these elements in excess of their estimated requirements and were reduced when Ca and P or P alone was reduced proportionately to about 0·75 times requirement. The data are in accord with the TCORN recommendations and suggests that they provide a satisfactory basis for defining Ca and P requirements for growing lambs.

Effects of cimaterol on energy utilization for maintenance and for protein and fat deposition by wether and ewe lambs given chopped lucerne hay or lucerne-barley pellets

ABSTRACTThe effects of sex (wethersv.ewes), diet (chopped lucerne hayv.lucerne-barley pellets) and cimaterol on energy utilization by Suffolk cross lambs were determined by comparative slaughter. Quadratic regression of energy retention (RE) on metabolizable energy intake (MEI) enabled estimation of maintenance energy requirements (Em), efficiencies of gain (ktotal) and maximum rates of gain (REMAX). Regressions using RE in fat and proteinv.MEI yielded analogous parameters for fat and protein deposition (Em fat, kfat, REMAX fatand Emprotcin, kprolein, REMAXprotcinrespectively). Emwas lower in wethers than ewes (455v.510 kJ/kg M0·75per day respectively), but was unaffected by diet or cimaterol. Sex and cimaterol did not affect ktotai. which was higher in lambs given pellets compared with lambs given hay (0·417v.0·224 respectively). Similarly, REMAXwas higher in lambs given pellets than in lambs given hay (326v.114 kJ/kg 0·75 per day respectively). None of the groups differed significantly in the parameters of fat deposition, which averaged 480 kJ/kg 0·75 per day for Emfal, 0·224 for ktat, and 250 kJ/kg M0·75per day for REMAX, fat-Em.proteinwas lower in wethers than in ewes (466v.569 kJ/kg 0·075 per day, respectively), and was further reduced by cimaterol (418 and 507 kJ/kg 0·75 per day for wethers and ewes respectively). Estimates of kprotcin were higher in wethers than in ewes (0·091v.0·064 respectively), and were increased by cimaterol (0·115 and 0·089 for wethers and ewes respectively). Similarly REMAX protein was higher in wethers than in ewes (47v.37 kJ/kg 0·75 per day respectively), and was increased by cimaterol (58 and 48 kJ/kg 0·75 per day for wethers and ewes respectively). The repartitioning action of cimaterol was additive with effects of diet, intake and sex.

The performance of short scrotum and wether lambs born in winter or spring and run at pasture in northern Tasmania

Summary. The growth of short scrotum and wether lambs was studied in 3 experiments over 2 years, at the Elliott Research Station in northern Tasmania. Short scrotum lambs born in winter grew significantly (P<0.05) faster than wethers from birth to slaughter at 137 days of age. For spring born, short scrotum lambs, the growth advantage was less because of the quality and quantity of pasture available during summer and autumn. Wether lambs were fatter than short scrotum lambs in all experiments, with the slope of the relationship between GR and carcass weight being 0.57 � 0.02 I! 0.42 � 0.01 mmkg (experiment 1); 1.13 � 0.1 1 v. 0.68 � 0.09 mm/kg (experiment 2); and 0.91 � 0.16 v. 0.63 � 0.08 mm/kg (experiment 3) respectively. As carcass weight increased, the difference in carcass fatness increased. There was a shift in the distribution of carcasses according to fat score, with more wether carcasses being allocated high fat scores. Testes weight in the short scrotum lambs showed considerable variation within and between experiments and in all cases the testes were located in a subcutaneous position. There was a poor relationship between testes weight and growth rate. The level of testes development in a proportion of animals indicated that the animals could be fertile.

Effect of plane of nutrition and age on carcass maturity of sheep.

One hundred twenty ewe and wether lambs were fed high (76% TDN, 12.3% crude protein) or low (70.6% TDN, 16.1% crude protein) energy diets and slaughtered at average ages of 261, 356 or 469 d. High planes of nutrition for lambs at 356 or 469 d of age resulted in heavier carcasses, thicker fat depth and higher flank streaking scores compared to lambs fed low planes of nutrition. Rib bone, break joint and overall maturity scores were not influenced (P greater than .05) by diet. Metacarpal and metatarsal bones from lambs fed high planes of nutrition were slightly longer and heavier and required more force to break (P less than .05) compared with bones from lambs fed low planes of nutrition. The majority of the ewes fed high or low planes of nutrition had fused growth plates and possessed spool joints by 469 d; none of the wethers had spool joints. An additional 27 wethers were slaughtered at an average of 480, 578 or 662 d. Rib bone, break joint and overall maturity scores were not different (P greater than .05) for animals fed the high or low energy diets, but bone weight and shaft break force values were higher for those fed high energy diets. At 662 d of age, only 20% of the wethers on each dietary regimen possessed fused growth plates. Overall, plane of nutrition in market-weight lambs and yearlings had very little influence on the presence or absence of a break joint or on other bone maturity scores.(ABSTRACT TRUNCATED AT 250 WORDS)

High dietary calcium to phosphorus ratio and alkali-forming potential as factors promoting silica urolithiasis in sheep.

Sheep were used to study factors previously found to promote silica urolithiasis in a rat model. In addition to high silica, these dietary factors included elevated calcium, a high calcium to phosphorus ratio and alkali-forming effects. Wether lambs had ad libitum access to a diet of 50% of grass hay and 50% ground oats plus supplement. Diet analysis was 3.4% total SiO2, .29% calcium, .25% phosphorus, 11.3% CP and 28% ADF. Treatments (40 lambs/treatment) consisted of a control (C), limestone to increase dietary calcium to .6% (L), L + 1% sodium bicarbonate (LS) and L + 1% ammonium chloride (LA). After a 91-d experimental period followed by a 56-d postexperimental finishing period, silica kidney deposits were found in all treatments, and SiO2 made up 74% to 97% of the urolithic ash. Kidney urolith incidences in the four treatments were C, 7/40; L, 12/40; LS, 20/40; and LA, 9/40. A higher urolith incidence in LS (LS vs C, P less than .05) and a trend toward a higher incidence in L (L vs C, P less than .2), accompanied by elevated urine pH (L = LS greater than C greater than LA, P less than .01), lend support to the concept that high-silica diets having high calcium to phosphorus ratios and alkali-forming potentials contribute to silica urolithiasis.

Growth and carcass fatness of ewe, wether, ram and cryptorchid crossbred lambs reared at pasture: effects of weaning age

The effects of weaning age and sex on growth, the carcass fatness and dressing percentage were studied in grazing Dorset x (Border Leicester x Merino) lambs. Entire male (ram and cryptorchid) lambs grew significantly (P<0.001) faster from marking to slaughter than did either wethers or ewes. They were also leaner than wethers, which were in turn leaner than ewes (mean � s.e. GR tissue depth: 11.4 � 0.16, 13.9 � 0.22 and 16.3 � 0.23 mm, respectively, at a carcass weight of 19.7 kg). Across all sex groups, the GR measurement increased 1.2 � 0.03 mm per kg increase in carcass weight. An earlier weaning (at 13-15 weeks of age) reduced (P<0.001) liveweight gains. There was also a small reduction (P<0.05) in the GR measurement associated with the earlier weaning, particularly in ewe and wether lambs. The dressing percentage of wethers increased with increasing liveweight over the entire range of weights. However, in ewes and entire males, there was little change in dressing percentage with increasing liveweight above 40 kg. An earlier weaning was associated with a small reduction in dressing percentage.