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The objectives of this study were 1) to determine how cellular growth of skeletal muscle is altered by the repartitioning agent cimaterol and 2) to determine if cimaterol alters endocrine status in association with its repartitioning effects. Thirty Dorset wether lambs were randomly assigned to a pre-treatment baseline group or received 0 or 10 ppm cimaterol in a complete, mixed, high-concentrate diet for 7 or 12 wk. Weights of biceps femoris (BF), semimembranosus (SM) and semitendinosus (ST) muscles were 32.8, 27.1 and 31.5% greater, respectively, in treated lambs at 7 wk, and were 22 to 24% greater at 12 wk. Longissimus (LD) cross-sectional area was 26 and 32% greater at these treatment intervals. Percent type I fibers declined significantly over the course of the experiment in ST, SM and LD, and cimaterol caused a small but significant reduction in percent type I fibers in the ST at 7 and 12 wk. Muscles from lambs fed cimaterol contained 50 and 75% more fibers that exhibited negative staining for phosphorylase activity. Mean cross-sectional area of type I and type II fibers in the combined portions of the ST were 30.4 and 29.3% greater, respectively, in cimaterol-fed lambs after 12 wk, while type I and type II fiber areas in the longissimus were only 13 and 15% greater, respectively. Cimaterol-induced hypertrophy of the ST resulted in both protein and RNA content being 30 to 35% greater (P<.01) at 7 and 12 wk, while DNA concentration was 22% less (P<.01) at 7 wk. DNA concentration returned to normal by 12 wk. These results indicate that cimaterol elicits a rapid increase in muscle RNA and protein accretion without concurrent incorporation of satellite cell nuclei. Plasma insulin and insulin-like growth factor-1 (IGF-1) concentrations were 55 and 34% lower, respectively, in cimaterol-fed lambs. Plasma somatotropin concentration and area under the curve were 2.3 times greater (P<.01) in lambs fed cimaterol for 6 wk, while plasma Cortisol, prolactin and glucose concentration were unaffected at 6 or 12 wk. The significant changes in endocrine status may be important in the mechanism(s) of cimaterol in altering muscle accretion.

Two experiments were conducted in which cimaterol [CL263,780; (anthranilo-nitrile, 5-[1-hydroxy-2-(isopropylamino) ethyl]-)] was fed at 0 or 10 ppm in a complete, mixed, high-concentrate diet to assess effects on growth performance and repartitioning of tissue growth in young, rapidly growing lambs. Average daily gain and feed efficiency (F/G) were not altered in Dorset wether lambs fed cimaterol for 6 or 11 wk in Exp. 1. Average daily gain and F/G were improved 16% (P<.05) in Suffolk × Dorset ram lambs fed cimaterol for 5 wk, but not 10 wk in Exp. 2. Cimaterol increased dressing percent by at least 3 percentage units (P<.05), increased longissimus area 26 and 32% (P<.001), reduced 12th-rib fat thickness 66 and 32% (P<.001) and reduced kidney and pelvic fat 34 and 44% (P<.001) at 6 wk and 12 wk, respectively (Exp. 1). Proximal hindleg muscles were 26% heavier (P<.001) in cimaterol-fed lambs in Exp. 1. Fishmeal (FM) replaced an equal amount of soy protein (3% of diet) to create a 2 × 2 × 2 factorial arrangement in Exp. 2. Cimaterol effects on carcass traits and muscle growth were similar to those observed in Exp. 1. However, hindleg and foreleg muscle weights and longissmus area were 16% greater (P<.001) in FM-fed lambs at 10 wk, and the cimaterol-induced muscle hypertrophy was slightly reduced in these lambs. Fat measures were unaffected by FM. These data demonstrate that cimaterol effectively repartitions skeletal muscle and adipose tissue accretion, and fishmeal fed for 10 wk significantly enhances skeletal muscle growth in lambs.

An experiment was conducted to determine the possible effects of photoperiod and prolactin on the physical and chemical composition of body weight gain. Prolactin was manipulated by im injections of 2-Br-α-ergocryptine (CB154) or sc injections of ovine prolactin (oPRL) and by two light:dark regimens (16L: 8D and 8L:16D). The four treatments employed were: 1) 16L:8D, placebo injections; 2) 16L:8D, CB154 injections; 3) 8L:16D, placebo injections and 4) 8L:16D, oPRL injections. After a 9-wk growth study, animals were slaughtered at similar body weights over the next 2-wk period. Weight of intestines was directly related and weight of pelt inversely related to circulating concentrations of prolactin. Content of N and lipid in the carcass was not influenced by treatment. However, N content of the noncarcass components was elevated (P<.01) in animals receiving CB154. In vitro rates of acetate incorporation (nmol lOO mg tissue−1• •3 h−1) were higher in subcutaneous than in perirenal adipose tissue (1,920 vs 777; P<.001). Rates for treatments 1, 2, 3 and 4 were 1,770, 953,1,320 and 1,350, respectively. The rate for treatment 1 was greater than that for treatments 2 (P<.001) and 3 (P<.05). There was no stimulation of lipogenesis in response to insulin added to the incubation medium. In vitro rates of glycerol release (nmol 100 mg tissue−1• 2 h−l) were higher in perirenal than in subcutaneous adipose (135 vs 81; P<.001). The respective treatment rates were 120, 84, 104 and 124, with treatment 1 being greater (P<.05) than treatment 2. Epinephrine addition elevated glycerol release (156 vs 60; P<.001). Differences for in vitro lipid metabolism between the perirenal and subcutaneous depots were independent of differences in cell size. Overall, these data indicate that the increased body weight gain due to extended lighting was not accompanied by detrimental effects on carcass composition. Nor was there any clear relationship between circulating concentrations of prolactin and in vitro lipid metabolism.

An experiment was conducted to determine whether prolactin is involved in growth or in mediating the photoperiod induced growth response in sheep. Prolactin was manipulated by im injections of 2-Br-α ergocryptine (CB154) or sc injections of ovine prolactin (oPRL) and by two light:dark regimens (16L: 8D and 8L:16D). Fifty-six wether lambs (two/ pen) were allotted to one of four treatments for a 9-wk growth study. Treatments were: 1) 16L: 8D, placebo injections; 2) 16L:8D, CB154 injections; 3) 8L:16D, placebo injections and 4) 8L:16D, oPRL injections. Daily injections of CB154 (.1 mg/kg body weighf.75), oPRL (.8 mg/kg body weight.75) or placebo were in 1 ml volume. Animals were fed ad libitum a complete mixed diet. At wk 8, plasma prolactin concentrations at 3 to 6 h postinjection were 214, 3, 90 and 228 ng/ml for treatments 1, 2, 3 and 4, respectively. Pattern of feed intake, measured at 8-h intervals for a 48-h period, was affected by photoperiod. Animals exposed to the 16L:8D photoperiod consumed 40.0, 42.4 and 17.6% of their total daily feed intake during the first 8 h of light, second 8 h of light and 8 h dark interval, respectively. Those exposed to the 8L:16D regimen consumed 55.2, 22.2 and 22.6% during their 8-h light interval, first 8 h of dark and second 8 h of dark, respectively. Both cumulative gain and feed intake were greater in 16L:8D control animals than in those animals receiving CB154. However, there was no difference in cumulative gain or feed intake between control animals on the 8L:16D regimen and those receiving oPRL. Overall, these results give no definitive support to a role for prolactin in growth or in mediating the photoperiod induced growth response in sheep.

In two experiments, a total of 46 Finn Cross and Dorset lambs were artificially group-reared. Thirty eight were weaned abruptly at 14 d of age from a commercial milk replacer (MR) to a dry starter diet (SD). Lambs were self-fed cool (10 to 15 C) MR reconstituted to 25% dry matter (DM). The ground (2-mm screen) SD averaged 26.2% crude protein and 7.4% fat (DM basis). For both experiments, birth and weaning weights averaged 3.8 and 8.0 kg, respectively. Experiment 1 tested a strategy for encouraging postweaning DM intake. Fifteen lambs received MR reconstituted to 33% DM from d 11 to 14, and 15 lambs received standard 25% DM MR. Between d 14 and 15, intakes of DM, gross energy, crude protein and water dropped 86, 89, 85 and 64%, respectively. Lambs doubled their birth weights during the milk-feeding period and consumed 1.41 kg SD between d 14 and 25. The MR reconstitution rate did not affect weaning weight, postweaning SD or water intake, or growth check (GC, P>.10). Postweaning GC averaged 12.2 d and was not influenced (P>.10) by birth weight, sex or weaning weight. Mortality and disease rates under these conditions were negligible. Experiment 2 was designed to differentiate between the dual effects at weaning of altering the type of diet and of reducing the level of nutrient intake. Eight lambs were weaned to SD at 14 d, and eight lambs were bottle-fed isocaloric levels of MR from d 12 to 30. At weaning, plasma glucose concentration declined 1.4 mM from 6.7 mM due to fasting and an additional 1.0 mM due to the change of the type of diet (P<.01). Plasma acetate and urea N concentrations rose steadily after d 16 in the SD-weaned lambs, but not in the MR-fed lambs (P<.01), suggesting that the SD-weaned lambs absorbed ruminal fermentation products. These results indicate that artificially reared lambs may be routinely weaned to a dry diet at 14 d of age. The major alterations in plasma metabolites that occur within 6 to 8 d after abrupt weaning may define the period when these lambs become functional ruminants.

To test whether lipogenesis is limited by lack of glucose precursors, 45 lambs (30 kg) were randomly grouped by sex and initial weight and fed ad libitumin pens of three in a growth and slaughter experiment. The diets consisted of a basal mixed chopped hay (C), hay + 4% butylene glycol (BD) and hay + 4% propylene glycol (PG). On a dry matter basis, the crude protein content and in vitrotrue digestibility of the hay were 9.6 and 64%, respectively. Growth and feed intake were recorded. After 13 weeks, the lambs were killed. Blood glucose concentrations, feed intake and weight gains did not differ between diets, but intake and weight gains were minimal. BD increased (P<.01) blood ketones. Perirenal adipose tissue fatty acid synthetase (FAS) activity averaged 2.6, 2.4 and 1.2 nmole NADPH oxidized/mg cytosol protein/min for the BD, PG and C lambs, respectively. Values for both glycol-fed groups were higher (P<.01) than the control value. Carcass chemical composition followed a similar pattern, with BD, PG and C carcasses containing 38.1, 39.2 and 35.8% dry matter, respectively, and the dry matter containing 36.6, 39.4 and 30.0% fat, respectively. Carcasses of the BD and PG lambs did not differ significantly from each other, but both groups had more (P<.05) fat and less (P<.05) protein and ash than did the C carcasses, suggesting that the chemical composition of lamb carcasses may be nutritionally manipulated. The essentially equal response of adipose FAS activity and carcass fat in lambs fed PG and lambs fed BD indicates that the inclusion of glucogenic substances did not promote lipogenesis in these lambs fed at or slightly above maintenance.

Two experiments were completed with a total of 54 5- to 7-week-old weanling Yorkshire pigs to determine (Experiment 1) the tissue retention of dietary selenium (Se) present in white sweet clover (Melilotus alba) relative to that provided as sodium selenite (Na2SeO3) and (Experiment 2) the tissue retention and liver distribution of Se present in fly ash incorporated into the diet.In Experiment 1, groups of four pigs each were randomly allotted to corn-soybean meal-type diets containing 5 or 10% white sweet clover grown either in low Se soil (.03 ppm Se in clover) or on fly ash (70 ppm Se in clover). Na2SeO3was added to the low Se clover diets to provide 0, 3.5 or 7.0 ppm of Se. Se concentrations of kidney, liver and skeletal muscle after 61 days were increased more by fly-ash grown sweet clover than by Na2SeO3, but blood Se was increased more by Na2SeO3. No histopathological lesions were found in liver, kidney, heart, pancreas or skeletal muscle. Diets had no effect on weight gain or feed to gain ratio.In Experiment 2, 30 pigs were fed from weaning to 92 kg slaughter weight on a corn soybean meal-type diet containing 0, 1, 2, 4 or 8% fly ash (5.7 ppm Se). Fly ash had no effect on weight gain and no histopathological lesions were found in heart, liver, kidney, pancreas or skeletal muscle. Tissue Se concentrations increased progressively with graded levels of fly ash in the diet. Distribution of Se in eight different sites in the liver was uniform. It is concluded that Se supplied in the diet as a component of fly ash or of white sweet clover grown on fly ash (probably as a constituent of seleno-amino acids) is absorbed and utilized for tissue deposition by the pig. The toxicological potency of clover-borne Se and its ability to alleviate vitamin E - Se deficiency signs relative to that of Na2SeO3remain unknown.

The objective of this study was to compare rebreeding activities of spring- vs fall-lambing Polypay, Dorset, St. Croix and Targhee ewes that either suckled their lambs for 40 d or had lambs weaned at birth. Seasonal effects of male fertility were reduced by utilizing an excess number of fertile rams in the spring. Plasma concentrations of progesterone were monitored to assess days to the first normal ovulation, days to conception and estrous vs anestrous activity. Breed, season and lactation affected the rebreeding performance. Dorset ewes had similar conception rates between spring and fall but a shorter interval from lambing to first ovulation in the fall. Polypay and Targhee ewes were the opposite; they had higher conception rates in fall than in spring matings with no seasonal influence on postpartum interval. Postpartum ewes in the fall had higher conception rates, and fewer of these ewes became anestrous or had estrous cycles of abnormal duration than of those ewes lambing in the spring. Ewes that suckled for 40 d in the spring had delayed estrous activity, but when these ewes became estrual they had higher conception rates than ewes whose lambs were weaned at birth. Lactation had no inhibitory affect on the postpartum interval of fall lambing ewes. These data suggest that the response of different breeds to various components of postpartum fertility varies with season and management of the flock.

Four groups of four lambs each were fed chromic oxide containing diets of varying hay-grain ratios (100:0, 75:25, 50:50, 25:75), digestion trials were conducted, the animals killed and samples of the digesta collected from the rumen-reticulum, omasum, abomasum, duodenum-jejunum, ileum, cecum and large intestine. These were analyzed for dry matter, ether extract, chromic oxide and neutral detergent fiber. Samples of the feed, feces and abomasal and ileal samples were analyzed for starch and additional rumen fluid samples collected and analyzed for acetic, propionic and butyric acids.Expected differences were observed in the chemical composition and digestibility of the diets. The chromic oxide concentration in the duodenum showed a marked decrease and this is attributed to the massive influx of endogenous dry matter. This is calculated to be from 1 (100% hay) to 2 (25% hay) times the contribution of dietary origin to the duodenal contents. The estimations of digestible dry matter of the diets by total collection and by chromic oxide ratio calculations were not different.Estimations of the starch reaching the abomasum and disappearing from the lower tract were made based on chromic oxide ratios. These estimates were 10, 33, 52 and 120 gm./kg. of diet on the 100, 75, 50 and 25% hay diets, respectively. This starch in the abomasum is offered as a possible explanation for the differences in efficiency of utilization of digestible energy from hay and concentrate diets.

Significant increases in the iodine number of lamb depot (kidney) fat were observed when 15% corn oil was included in the diet. Concomitant changes in the fatty acid composition of the fat were also observed with increases in oleic and linoleic acids and decreases in palmitic and stearic acids. The changes occurred whether the lambs were fed high-, medium-, or low-fiber diets, although there was some indication the high-fiber diets favored a greater effect on depot fat by the corn oil.Gain was not markedly affected by the dietary treatments used except in the low fiber-high oil treatment where both diet consumption and growth were significantly reduced. Additional data are presented on the iodine number of fat from various areas of the carcass.

Eleven Holstein bull calves were used to study the effect of the antibiotics, chlortetracycline and bacitracin, and of advancing age on the digestibility of feed and the nitrogen retention of dairy calves. Four calves were used as controls, four received chlortetracycline and three received bacitracin. Both antibiotics were fed orally at the rate of 40 mg. per 100 lb. body weight per day from 3 days of age throughout the experiment. Fecal and urinary collections were made when the calves were 7 and 16 weeks old. There was no effect on the digestibility of dry matter, ether extract, crude fiber or nitrogen-free extract. Chlortetracycline increased both the apparent protein digestibility and nitrogen retention (P<0.05). At 16 weeks as compared with 7 weeks apparent protein digestibility (P<0.10) and nitrogen retention (P<0.05) were also increased.

A 23factorially arranged feeding trial was conducted with 16 groups of 12 fattening lambs each to evaluate the response of lambs fed different amounts of protein and energy with and without stilbestrol.Interactions between digestible protein and ENE fed at 90 and 120% of recommended amounts were detected for liveweight gains, grades and feed efficiencies. The lambs fed the high energy rations apparently required more protein than those fed the low energy rations to maintain feed intake and growth rate.Lambs receiving the high level of protein gained faster, graded higher and were more efficient than those fed the low level. Differences between energy levels were not observed. Actually differences existed between energy levels within each protein level but were in a different direction within each protein level and were detected as a protein by energy interaction.Stilbestrol significantly increased average daily gains (approximately 0.05 lb. per day) and feed efficiency (5.42 vs. 4.49 therms ENE required per lb. gain) but decreased liveweight grade approximately one-third of a grade. No interactions were detected between stilbestrol, protein and energy in liveweight gains or grades.

Eleven ponies were fed diets containing 1:0, 3:2 or 1:4 forage-grain ratios for 30 days. Animals were killed 4 hr. after feeding and the entire digestive tracts were removed and segments isolated. Digestion coefficients were calculated for dry matter, protein, available carbohydrate (ACHO) and neutral detergent fiber (NDF) by Cr2O3-nutrient ratio for seven segments of the gut.The major site of ACHO and protein digestion was prececal; whereas, the major sites of NDF digestion were the colon and cecum regardless of the hay:grain ratio. Therefore the relative importance of digestion in the lower gut increased with increased levels of forage.

Nine purebred Hampshire and 10 purebred Corriedale ewes, 8 with twin lambs and 11 with single lambs, were used in a 2 × 2 factorial experiment to study the effects of breed and number of lambs suckled on milk production, milk composition and DE requirements for milk production when being fed to maintain a constant body weight, and to study the energetic efficiency of milk production during the first 12 weeks of lactation. Maintenance requirements were simultaneously determined using five nonpregnant, non-lactating ewes of each breed. The ewes were individually fed a ration of chopped hay and shelled corn, and their lambs were offered a creep ration ad libitumin adjoining individual creep pens.Hampshire ewes produced significantly (P<.01) more milk and milk calories than did the Corriedale ewes. Ewes with twin lambs produced significantly (P<.01) more milk than those suckling single lambs.Dry matter and fat concentrations were higher in the milk of Hampshire than of Corriedale ewes. Number of lambs suckled had no significant effect on milk composition, although the percent of milk fat tended to be lower in the ewes suckling twin lambs.When body weight was maintained, the Hampshire ewes required significantly (P<.05) more DE for milk production than the Corriedale ewes. The energy requirement differences between ewes suckling single and twin lambs were highly significant.Utilization of dietary energy for milk calorie yield was greater (P<.01) for Hampshire ewes. The difference between ewes with single and those with twin lambs was not significant.The effect of level of feed intake on ration digestibility is discussed in relation to feeding standards. Comparisons were also made between the relative merits of feeding the ewe extra DE for maximum milk production versusfeeding the lamb this extra energy directly.

Animal response was measured in the evaluation of hays over a 3-year period using 516 fattening lambs of native and western origin. Mixed grass hays were cut the first of June and about a month later and were field-cured or barn-dried. Paired and comparison type feeding trials and conventional type digestion trials were utilized. Further, an attempt was made to equalize the protein and/or energy between the early- and late-cut hays by adding appropriate concentrate feeds to the late-cut hay ration. The measurement criteria were total weight gain, live weight grade, feed consumption, and feed efficiency.Variations appeared between years in the differences of TDN content of forages with approximately the same time intervals in harvest dates. The TDN values for early-cut barn-cured hay varied from 66 in 1958 to 57 in 1959 to 61 in 1960 while late-cut barn-cured hay was fairly constant at 53 or 54. Early-cut hay showed significant increases in dry matter, crude fiber and protein digestibility over late-cut hay.Hay harvested early was significantly more favorable than late-cut hay in influencing total gain, live weight grade, feed efficiency and hay consumption in 1958. Live weight grade only was influenced by date of cutting in 1959 while both live weight gain and grade were increased by early-cut hay in 1960. In 1958, heat drying of hay significantly increased live weight grades. During the same trial, increasing the percent protein of the concentrate (by substituting soybean meal for 25% of the corn) failed to influence the performance criteria measured.Lambs receiving late-cut hay in 1959 and 1960 supplemented with either energy or protein and energy grew as well and graded as high as lambs receiving the early-cut hay treatments. Therefore, it would appear that comparable animal performance could be obtained with lower quality hays, in the ranges herein tested, when adequately supplemented.

Two experiments were conducted to determine the TDN requirements of ewes during the last 6 weeks of gestation and the first 90 days of lactation and to determine any interaction between levels of energy fed before and after lambing. In the first experiment 110 ewes were allotted to treatments in a 2 × 2 × 3 factorial arrangement. Treatments included two levels of TDN (100% and 125% of 1957 N.R.C.) during gestation and lactation and three creep rations: hay only; hay+corn, SBOM; hay+calf starter. In the second experiment, 130 ewes were allotted to a 3 × 3 × 2 factorial arrangement of treatments, which included three levels of TDN (75%, 100% and 125% of N.R.C.) during late gestation and lactation and a separation of single and twin lambs. One hundred and forty-three lambs were born the first year and 188 the second.The results are summarized as follows: Varying TDN levels for ewes during the last 6 weeks of gestation did not affect single lamb birth weights but feeding higher levels significantly increased twin birth weights.Feeding higher TDN levels during gestation significantly increased the average 90-day weight of twin lambs in both experiments.Feeding higher lactation levels to ewes increased the 90-day weights of both single and twin lambs.Several interactions among treatments were observed and are discussed.Ewes with single lambs approximately maintained their body weight from 6 weeks pre-partum to 1 day post-partum and to 90 days post-partum when fed the present N.R.C. standard whereas ewes with twins required approximately the 125% level.Significant differences in 90-day weights among creep treatments were observed with the “complex” concentrate being superior to the “simple”, which in turn was superior to the hay alone.A cost analysis table for the lactation treatments is included.These data indicate that the present N.R.C.-TDN standard is apparently satisfactory for ewes pregnant with single lambs but increased levels for ewes pregnant with twin lambs seems advisable, together with an increase in the TDN standard during lactation for ewes with single and twin lambs.

Oral MAP and injected PMS were used in various combinations to test their effect on estrus synchronization and fertility of ewes during both the anestrous and estrous seasons. A total of 391 ewes was used in 5 trials which included 15 treatment groups.During the anestrous period a combination of MAP and PMS was effective in synchronizing an average of 80% of the treated ewes in two trials. Fifty-one percent of ewes synchronized and bred lambed. MAP alone was ineffective in producing a synchronized estrus in anestrous ewes.For fall-bred cycling ewes 60 mg. of MAP given orally for 20 days was more effective than 30 mg. daily for 16 days in both synchronizing ewes and maintaining their fertility. Normally cycling Dorset ewes were successfully synchronized in March with 60 mg. of MAP daily for 20 days.Four combinations of MAP and PMS were tested on ewes at the beginning of the estrous season in late July and early August. All combinations tested were reasonably successful; however, maximum synchronization (100%) and apparent fertility (82%) were observed on a treatment including PMS before and after an 8-day MAP feeding period, although this was not statistically different from the other treatments.Data on synchronization range, lambing range, lambing percent and fertility at the second post-treatment estrus are also presented.

Five years′ research on the dietary causes of muscular dystrophy in the lamb are included. Selenium and vitamin E were equally effective in preventing the natural occurring syndrome, although neither has given complete protection when fed to the ewe during later gestation and early lactation but both have been completely effective when given directly to the lamb. A combination of vitamin E and selenium given to the ewes did result in complete protection for the lambs. Apparently the maternal transfer of either selenium or vitamin E was inadequate at the levels fed (1.0 ppm and 100 I.U./day, respectively). Cooking of the basal ration fed the ewes also completely prevented the condition in the lambs indicating a heat labile antagonist may be present in the basal feeds. This is further substantiated by evidence presented on the prevention of exudative diathesis in the chick and by the relatively high levels of oral selenium apparently required by the ewes to protect the lambs from muscular dystrophy. The addition of an anti-oxidant to the ewes′ diet did not reduce the incidence of dystrophy in the lambs. Linseed oil meal was partially effective as a preventive which is explained by its relatively high selenium content. Data on the selenium content of the feeds used and plasma tocopherol data on the ewes and lambs are also presented.

The comparative utilization of dietary calcium and of Sr90was determined in pigs and sheep under typical management conditions by balance feeding trials, radioassay for Sr90present in feedstuffs in 1958, and chemical analysis for calcium.A ration consisting of hay from crop year 1958, soybean meal and corn ranged from 74 to 93 µµc Sr90/gm. Ca. The hay contributed about 90% of the Sr90intake of the animals.The pigs started with a body burden of 3.7 µµc Sr90/gm. Ca and finished with 9.4; comparative values for the sheep were 30 and 27. For the pigs the comparative utilization of calcium and Sr90was 48 and 8.6% respectively; values for the sheep were 30 and 6.3%.In agreement with values for other species, the pigs and sheep utilized Sr90about 0.2 as effectively as calcium.

Eighty-six lambs were slaughtered at 33, 40,50 or 60 kg. preshrunk, shorn live weight after being fasted for 24 or 72 hr. Marketing losses were determined to include preslaughter, slaughter, cooler and cutting losses. Cooking losses were then determined on representative loin chops from each lamb. Although body weight significantly affected all marketing losses measured, these were often offsetting effects, and the percent of the original lamb, ranging from 32.7 to 34.6, included in the four trimmed retail cuts (leg, loin, rack and shoulder) was not greatly affected by body weight in the lambs fasted for 24 hr. The range was greater (30.7 to 34.1%) in the lambs fasted 72 hr., as a reduction due to fasting was noted in the lightest lambs. The chemical composition of the wholesale rack and retail loin chops was affected by body weight. Cuts from the larger lambs were higher in ether extract and lower in water, protein and ash content. Cooking tended to diminish these differences. No differences due to preslaughter shrink period were noted on cooking losses.

An experiment was conducted to study: (1) the efficiency with which single and twin lamb pairs convert milk and supplemental feed energy and protein into weight gains, as well as the energy and protein of these gains at different levels of milk intake, and (2) to compare the chemical composition of the lamb bodies at 90 days of age as affected by level of nutrient intake. Thirty lambs, 10 singles and 10 pairs of twins, all sired by Hampshire rams, and suckling Rambouillet × Columbia dams were used in a 2 × 2 factorial experiment. Treatment factors consisted of different levels of milk intake and twin vs. single lamb comparisons. Different levels of milk intake were obtained by feeding 94% and 111% of the digestible energy (DE) requirements recommended by the N.R.C. (1957) to ewes with single lambs and 97% and 114% to ewes with twins. The following results were obtained: The lambs consuming more milk, due to the higher DE levels fed to their dams, were significantly heavier at 90 days of age than those suckling ewes fed the lower levels and single lambs were heavier than twin lambs. No interaction was observed between level of milk intake and number of lambs suckled.There was a 12% increase in body energy gain favoring the lambs consuming the higher milk level. Combined twin lamb gains were significantly greater than single lamb gains. Protein gain was significantly greater in lambs consuming the higher milk levels and in twin lambs.The body composition of the lambs was not significantly changed due to milk intake levels, but the single lambs were composed of less water and protein and more fat than the twin lambs.It was estimated that the lambs utilized 77% of the energy of the milk consumed and 19.4% of supplemental feed energy for body energy gain and maintenance energy. On an energy gain basis only, single and twin lambs utilized milk gross energy with an estimated efficiency of 43.8% and 37.4%, respectively. Estimated creep feed utilization was 13.2% for single lambs and 8.8% for twin lambs. Efficiency values did not differ due to level of intake. Gross energy in the pelleted ration fed to the ewes was converted to milk and thence to lamb gain with an average estimated efficiency of 8.3%.The estimated utilization of milk protein for body protein gain and wool growth was 43.3%. Estimated creep ration protein utilization was 19.9%. Treatment differences were small.

Twenty western ewes of mixed Rambouillet and Columbia breeding, 10 with single lambs and 10 with twin lambs, were used in a 2 × 2 factorial experiment to study the effect of two levels of digestible energy and the number of lambs suckled on milk production and composition, and on lamb growth, during the first 90 days of lactation. The DE values were approximately 96% and 113% of the requirements of the lactating ewe for the first 8 to 10 weeks of lactation, as recommended by the National Research Council (N.R.C., 1957). The ewes were individually fed a 55%-roughage: 45%-concentrate ration in pellet form. The lambs had access to limited quantities of the same ration in individual creep pens.Milk production was determined by hand milking following injections of a purified oxy-tocic principle at the beginning and end of a 2½-hr. interval during the first 8 weeks of lactation and 3-hr. intervals the 10th and 12th weeks. Test milk values were obtained in lactation weeks 1, 2, 4, 6, 8, 10 and 12. Each milk sample was analyzed for dry matter, protein, fat, ash and caloric content.Efficiencies of the ewes in converting feed energy into milk energy were determined. Estimations of the caloric contribution of body weight losses of the ewes were used in these determinations. The results are summarized as follows: Ninety-day milk yield, milk calorie production and lamb weights were significantly (P<.05) increased by feeding the ewes approximately 17%; more DE and were significantly (P<.01) higher for ewes suckling twin lambs than for those suckling singles.Feeding levels of DE had no significant effect on milk composition. Percent dry matter, fat and caloric value of the milk were significantly (P<.05) higher for ewes suckling twin lambs.Variation in feed intake by ewes did not result in significant differences in converting feed energy into milk energy. Ewes suckling twin lambs were more efficient (P<.01) in converting feed energy into milk energy.