Clinical and clinicopathologic features of transport tetany of feedlot lambs

Clinical and clinicopathologic features of transport tetany in 9 feedlot lambs were investigated. The lambs became recumbent within 10 days after arrival in the feedlot. The mean serum calcium concentration, mean magnesium concentration, and calcium:phosphorus ratio were significantly (P less than 0.01) less in affected lambs than in 6 unaffected lambs from the same feedlot. The mean serum phosphorus concentration was significantly (P less than 0.05) greater in the group of affected lambs. High activities of serum glutamic oxalacetic transaminase, creatine kinase, and lactate dehydrogenase in the serum of affected lambs indicated muscle necrosis, which was confirmed by histologic examination. Blood pH, HCO-3, and total carbon dioxide were significantly greater in affected lambs (P less than 0.01) than in unaffected lambs.     

Effect of immunization against somatostatin in the pregnant ewe on growth and endocrine status of the neonatal lamb

Absorption of somatostatin (SRIF) specific antibodies from colostrum of ewes actively immunized against SRIF may improve growth rate of the neonatal lamb by neutralizing the inhibitory effects of SRIF on pituitary and thyroid function. Growth and endocrine parameters in the offspring of SRIF immunized (SI) and control (C) crossbred ewes were examined. Lamb weight was recorded at birth and twice each week to 24 days of age. Blood samples were collected prior to first suckle and twice each week. At 21 to 24 days of age, in separate experiments, lambs were infused with glucose (0.29 g/kg), arginine (0.25 g/kg) or thyrotropin-releasing hormone (TRH; 0.33 microgram/kg). A strong correlation (R = 0.88; P less than .01) was observed between anti-SRIF titre in the ewe at parturition and in the lamb at 3 days of age. No effect on lamb birth weight (SI 4.28 +/- 0.27 kg; C 4.35 +/- 0.23 kg) was observed. At 24 days of age cumulative gain in SI lambs (5.4 +/- 0.32 kg) was greater (P less than .05) than in C lambs (4.5 +/- 0.32 kg). The growth hormone secretory responses to glucose or arginine were not affected by treatment. Plasma IGF-I, plasma thyroxine (T4) and the plasma thyrotropin and T4 responses to TRH were not different between treatments. Plasma triiodothyronine (T3) was higher (P less than .05) in SI (2.46 +/- .10 ng/ml) than in C (2.01 +/- .05 ng/ml) lambs, however, the plasma T3 response to TRH was lower in SI lambs. Plasma glucose (mg/dl) was higher (P less than .05) in SI (118.4 +/- 1.7) than in C (106.0 +/- 4.0) lambs. Plasma insulin was not affected by treatment. Increased plasma T3 and glucose concentrations during SRIF immunoneutralization in the neonate lamb may be important factors contributing to the growth response observed.     

Growth hormone stimulates protein synthesis in bovine skeletal muscle cells without altering insulin-like growth factor-I mRNA expression

Growth hormone is a major stimulator of skeletal muscle growth in animals, including cattle. In this study, we determined whether GH stimulates skeletal muscle growth in cattle by direct stimulation of proliferation or fusion of myoblasts, by direct stimulation of protein synthesis, or by direct inhibition of protein degradation in myotubes. We also determined whether these direct effects of GH are mediated by IGF-I produced by myoblasts or myotubes. Satellite cells were isolated from cattle skeletal muscle and were allowed to proliferate as myoblasts or induced to fuse into myotubes in culture. Growth hormone at 10 and 100 ng/mL increased protein synthesis in myotubes (P < 0.05), but had no effect on protein degradation in myotubes or proliferation of myoblasts (P > 0.05). Insulin-like growth factor-I at 50 and 500 ng/mL stimulated protein synthesis (P < 0.01), and this effect of IGF-I was much greater than that of GH (P < 0.05). Besides stimulating protein synthesis, IGF-I at 50 and 500 ng/mL also inhibited protein degradation in myotubes (P < 0.01), and IGF-I at 500 ng/mL stimulated proliferation of myoblasts (P < 0.05). Neither GH nor IGF-I had effects on fusion of myoblasts into myotubes (P > 0.1). These data indicate that GH and IGF-I have largely different direct effects on bovine muscle cells. Growth hormone at 10 and 100 ng/mL had no effect on IGF-I mRNA expression in either myoblasts or myotubes (P > 0.1). This lack of effect was not because the cultured myoblasts or myotubes were not responsive to GH; GH receptor mRNA was detectable in them and the expression of the cytokine-inducible SH2-containing protein (CISH) gene, a well-established GH target gene, was increased by GH in bovine myoblasts (P < 0.05). Overall, the data suggest that GH stimulates skeletal muscle growth in cattle in part through stimulation of protein synthesis in the muscle and that this stimulation is not mediated through increased IGF-I mRNA expression in the muscle.     

Effects of flax supplementation and a combined trenbolone acetate and estradiol implant on circulating insulin-like growth factor-I and muscle insulin-like growth factor-I messenger RNA levels in beef cattle

We evaluated effects of a 5% (dry matter basis) ground flaxseed supplement (flax) and a trenbolone acetate and estradiol-17beta implant, Revalor-S, on circulating IGF-I and muscle IGF-I messenger RNA (mRNA). Sixteen crossbred yearling steers (initial BW = 397 kg) were assigned randomly to one of four treatments: 1) flax/implant; 2) nonflax/implant; 3) flax/nonimplant; and 4) nonflax/nonimplant. Serum was harvested from blood collected on d 0 (before implant or flax addition), 14, and 28, and used in subsequent analyses of circulating IGF-I. Biopsy samples (0.5 g) were obtained from the longissimus muscle on d 0, 14, and 28. Total RNA was isolated from the muscle samples, and real-time quantitative-PCR was used to assess relative differences in IGF-I mRNA. Flax supplementation had no effect (P > 0.10) on circulating IGF-I concentrations. Following implantation, sera from implanted steers had 52 and 84% greater (P < 0.05) IGF-I concentrations than sera from nonimplanted steers on d 14 and 28, respectively. On d 28, local muscle IGF-I mRNA levels increased 2.4-fold (P < 0.01) in biopsy samples obtained from implanted compared with nonimplanted steers. Muscle biopsy samples from nonflax cattle had 4.4-fold higher (P < 0.01) levels of IGF-I mRNA than those from flax cattle on d 28. To determine whether a component of flax, alpha-linolenic acid (alphaLA), was directly responsible for IGF-I mRNA down-regulation, we incubated primary cultures of bovine satellite cells, from implanted and nonimplanted steers, in two concentrations of alphaLA (10 nM and 1 microM). An implant x dose interaction (P < 0.05) was observed for IGF-I mRNA concentrations in bovine satellite cells cultured for 72 h with alphaLA. Satellite cells from nonimplanted steers had similar (P > 0.10) IGF-I mRNA concentration regardless of the level of alphaLA exposure; however, satellite cells from implanted steers exposed to 10 nM and 1 microM alphaLA had 2.5- and 2.0-fold greater IGF-I mRNA levels, respectively, than cells from implanted steers that were not exposed to alphaLA (P < 0.05). Administration of a Revalor-S implant increased circulating IGF-I and local muscle IGF-I mRNA concentrations in finishing cattle. However, muscle IGF-I mRNA levels were decreased by flax supplementation. Muscle cell culture experiments suggested that alphaLA was not responsible for the IGF-I mRNA down-regulation.     

Growth performance and carcass composition of lambs infused for 28 days with a growth hormone-releasing factor analogue.

A human growth hormone-releasing factor analogue, [DesNH2Tyr1,D-Ala2,Ala15]hGRF(1-29)NH2 (GRF-A), was infused s.c. into lambs for 28 d to determine its effects on growth performance and carcass composition. Twenty crossbred wethers weighing 47.0 +/- .5 kg were implanted with 7-d osmotic minipumps at weekly intervals. Minipumps contained either vehicle (dimethyl sulfoxide:H2O, 1:1) or GRF-A, released at a rate of 208 pmol (or .7 micrograms).h-1.kg-1. During the infusion period, plasma GH levels were increased (P less than .01) in GRF-A-treated wethers compared with control wethers (15.0 vs 9.3 ng/ml) and were higher on days that closely followed minipump implantation. Plasma IGF-I and hepatic IGF-I RNA concentrations were similar in lambs of both groups. Analogue treatment improved feed conversion (4.9 vs 5.8 kg dry matter/kg gain, P less than .05), increased average daily gain (.35 vs .30 kg, P = .05) and had no effect on feed intake, wool growth and body, carcass, selected organ and pituitary weights. Carcasses from GRF-A-infused lambs had less adjusted fat depth, a lower percentage of fat and a higher percentage of protein (P less than .05) than carcasses from control lambs. Magnitude of most effects of GRF-A on carcass measurements were correlated with the mean GH level that a lamb had during the infusion period. In conclusion, s.c. infusion of GRF-A improved feed utilization and altered carcass composition of feeder lambs in a relatively short period of time (28 d).     

The relationships between glycogen stores and muscle ultimate pH in commercially slaughtered pigs

Small samples of liver and m. adductor (AD) were collected within 45 minutes of death from the carcasses of a total of 604 pigs killed at three bacon factories. Glycogen concentrations were measured and part of the muscle sample allowed to complete post-mortem glycolysis in order to estimate ultimate pH (pHu) values. Liver glycogen levels were also used to predict overall food withdrawal times. Muscle glycogen concentrations ranged from 2.2 to 15.3 mg/g, liver glycogen from 0.01 to 50.7 mg/g and pHu in the AD from 5.51 t 6.76. The overall average predicted fasting time was 16.5 +/- 0.54 (SEM) hours and 22% of pigs had pHu values in the AD greater than 6.2 indicative of potentially dark, firm, dry meat. Muscle glycogen concentration was positively correlated with liver glycogen (r = 0.27, P less than 0.01) and negatively correlated with predicted fasting time (r = -0.30, P less than 0.001). The pHu in the AD was negatively correlated with liver glycogen (r = -0.34, P less than 0.001) and positively correlated with predicted fasting time (r = 0.37, P less than 0.001). Therefore, pigs which had reduced concentrations of glycogen in their livers, indicative of longer food withdrawal times before slaughter, tended to have less glycogen in their muscles and a higher pHu in the meat.     

Insulin-like growth factor-I concentration in Holstein female cattle: variations with age, stage of lactation and growth hormone-releasing factor administration

Plasma insulin-like growth factor-I (IGF-I) concentrations were monitored in Holstein females through different periods of their growth, lactation and after acute or chronic growth hormone-releasing factor (GRF) administration. Plasma samples were radioimmunoassayed using a human IGF-I antibody after a 24 hr incubation in a HCl(.1N)-glycine(.2M) buffer (pH 2). In a first study, IGF-I concentrations were measured in Holstein females of different ages and(or) stages of lactation (n = 6 per group). The IGF-I concentrations in newborn calves (102.0 +/- 11.3 ng/ml) markedly decreased (P less than .01) in 1 mo old animals (50.2 +/- 7.1 ng/ml), then increased (P less than .01) to 137.0 +/- 5.1 and 137.4 +/- 11.0 ng/ml in 6 and 10 mo old heifers, respectively. In dairy cows, IGF-I concentrations were low 24 hr post-partum (44.7 +/- 7.6 ng/ml) and then increased (P less than .05) to remain stable throughout lactation (91.3 +/- 4.9, 92.8 +/- 12.9, 96.1 +/- 7.6, 90.7 +/- 8.8 ng/ml at 2, 3, 6 and 9 mo of lactation, respectively). There was a further increase (P less than .05) to 113.7 +/- 3.1 ng/ml during the dry period. In a second trial, blood samples were collected from lactating dairy cows every 2 hr for 24 hr following a sc injection of saline (n = 4) or human (h) GRF (1-29)NH2 (10 micrograms/kg BW, n = 4). The IGF-I peak concentration was reached on average 10 hr after the GRF injection and was higher (P less than .01) in treated cows than in control cows (135.4 vs 86.9 +/- 16.2 ng/ml). In the last trial, daily sc injections of 10 micrograms of hGRF(1-29)NH2 per kg BW to dairy cows (252 days of lactation) for 57 days, which increased milk production by 14% (2 kg/day), also increased (P less than .01) IGF-I concentration: 127.1 +/- 5.3 and 118.0 +/- 1.6 vs 90.7 +/- 4.7 and 96.0 +/- 5.0 ng/ml on days 29 and 57 of treatment for treated (n = 9) and control (n = 8) cows, respectively. Thus, the IGF-I concentration in dairy cattle varies with age and stage of lactation, and is increased by GRF administration in lactating dairy cows.     

Evaluation of morphological lesions in selected internal organs in lambs of Kamieniecka,Pomorska and Polish Blackheaded Mutton sheep and their crossbreeds

Investigations were carried out on 40 rams aged 50 days (n = 8), Kamieniecka (K), Pomorska (P) and Polish Blackheaded Mutton (PBM) breeds and their crossbreeds (K x PBM, P x PBM). Microscopic evaluation of the liver, kidneys, spleen and heart muscle in the rams as well as ultrastructural analyses of their liver and semitendinous muscle showed that retrogressive lesions, circulation disturbances, inflammation and progressive changes occurred respectively: frequently, occasionally, rarely. Internal organs, particularly liver and kidneys, of crossbred rams (K x PBM and P x PBM) were almost two times more affected with morphological lesions than purebred lambs (K and P). However, in the semitendinous muscle these differences were more vivid in the ultrastructural analysis than in the histopathological or macroscopic observations. Results suggest that breed growth-rate differences have effects on the pathomorphological pattern of the liver and kidneys in lambs. On the bases of this evaluation, it can also be emphasised that young PBM rams are less susceptible to morphological lesions than the K and P breeds.     

Evaluation of biochemical evidence of congenital nutritional myopathy in two-week prepartum fetuses from selenium-deficient ewes

Muscle damage attributable to selenium (Se)/vitamin E deficiencies is known to develop at birth or later in lambs. The purpose of this study was to determine whether and when muscle damage develops in utero. Thirty pregnant ewes maintained on Se-deficient forages from birth were allotted to 3 equal groups. Half of each group was given a single IM injection of 0.056 mg of Se/kg of body weight, 1 month before parturition. At 3 weeks before parturition, cesarean section-derived fetuses from Se-deficient ewes did not have evidence of muscle damage. At 2 weeks before parturition, fetuses from Se-deficient ewes had biochemical evidence of congenital nutritional myopathy, as evidenced by low blood Se concentration (P less than 0.05) and by increased plasma creatinine kinase (P less than 0.001) and lactate dehydrogenase (P less than 0.01) activities, compared with fetuses from Se-treated ewes. Thus, for optimal protection of fetuses and newborn lambs in Se-deficient areas, Se should be administered to ewes at least 1 month before parturition.     

Growth factor messenger RNA levels in muscle and liver of steroid-implanted and nonimplanted steers

Ribonuclease protection assays were used to measure steady-state semimembranosus muscle and/or hepatic levels of IGF-I, IGFBP-3, IGFBP-5, hepatocyte growth factor (HGF), and myostatin messenger RNA (mRNA) in steers implanted from 32 to 38 d with Revalor-S, a combined trenbolone acetate and estradiol implant. Insulin-like growth factor-ImRNA levels were 69% higher (P < 0.01, n = 7) in the livers of implanted steers than in the livers of nonimplanted steers. Similarly, IGF-I mRNA levels were 50% higher (P < 0.05, n = 7) in the semimembranosus muscles of implanted steers than in the same muscles from nonimplanted steers. Hepatic IGFBP-3 mRNA levels were 24% higher (P < 0.07, n = 7) in implanted steers than in nonimplanted steers. Hepatic HGF and IGFBP-5 mRNA levels did not differ between implanted and nonimplanted steers. Similarly, muscle IGFBP-3, IGFBP-5, HGF, and myostatin mRNA levels were not affected by treatment. Previous data from these same steers have shown that circulating IGF-I and IGFBP-3 concentrations were 30 to 40% higher (P < 0.01, n = 7) in implanted steers than in nonimplanted, control steers. Additionally, the number of actively proliferating satellite cells that could be isolated from the semimembranosus muscle was 45% higher (P < 0.01, n = 7) for implanted steers than for nonimplanted steers. Viewed together, these data suggest that increased muscle IGF-I levels stimulate increased satellite cell proliferation, resulting in the increased muscle growth observed in Revalor-S implanted steers.     

Influence of diet on basal and growth hormone-stimulated plasma concentrations of IGF-I in beef cattle

The effects of nutrition on plasma concentrations of insulin-like growth factor-I (IGF-I) were characterized in steers under basal conditions and following single i.m. injection of bovine growth hormone (bGH, .1 mg/kg BW). Nutritional effects on IGF-I were studied in three trials. In all trials steers were individually fed and penned Angus or Hereford x Angus (280 kg). In the first trial, two diets (LPLE1: 8% CP and 1.96 Mcal ME/kg, 4.5 kg.hd-1.d-1; MPHE1: 11% CP, 2.67 Mcal ME/kg, 6.5 kg.hd-1.d-1) were fed (n = 5/diet). Plasma IGF-I concentrations averaged 74 (LPLE1) and 152 (MPHE1) ng/ml (P less than .02). Following bGH injection, IGF-I increased to peak concentrations between 12 and 24 h (averaging 105 and 208 ng/ml at peak for LPLE and MPLE, respectively, P less than .01). In the second trial, steers were fed diets composed of 8, 11 or 14% CP and 1.96 or 2.67 Mcal ME/kg dry matter (6.35 kg.hd-1.d-1 in a factorial arrangement for 84 d, n = 4/diet). Within the low ME diet groups, plasma IGF-I was similar in steers fed 11 and 14% CP but greater at these two CP levels than in steers fed 8% CP (P less than .05). Within the high ME diet groups, plasma IGF-I increased linearly with CP (P less than .01). In the third trial, steers were fed diets to result in a negative N status. Insulin-like growth factor-I was lower (P less than .02) during feed restriction than when steers were full-fed. The IGF-I response to bGH was diminished or absent in underfed steers (P less than .01). These data are interpreted to suggest that diet composition and intake affect plasma concentrations of IGF-I in steers. In cattle, CP may be the primary nutritional determinant of basal IGF-I, but the IGF-I response to CP may be affected by the available ME. Undernutrition can attenuate the IGF-I response to GH and uncouple the regulation of IGF-I normally ascribed to GH.     

Animal performance, plasma hormones and metabolites in Holstein and Belgian Blue growing-fattening bulls

Six Holstein (light-muscled type) and six Belgian Blue bulls (double-muscled type) were fed a finishing diet. Average daily gain was 1.36 kg for the Holstein bulls vs 1.24 kg for the Belgian Blue bulls (P less than .05). Holstein bulls consumed more feed (2.3 vs 1.8 kg/100 kg body weight, P less than .001) than the Belgian Blue bulls. The dressing percentage (55.4 vs 65.8%, P less than .001) and the proportion of muscle (56.1 vs 71.3%, P less than .001) in the carcass were less, whereas the proportions of adipose tissue (28.3 vs 15.4%, P less than .001) and bone (15.7 vs 13.4%, P less than .05) were higher in the Holstein bulls. Plasma creatinine determined in samples obtained once a week was lower (11.0 vs 20.3 mg/liter, P less than .001) in the Holstein bulls. In contrast, Holstein bulls tended to produce more triiodothyronine (2.3 vs 1.8 nM, P less than .10), tetraiodothyronine (71.9 vs 54.7 nM, P less than .10) and insulin-like growth factor I (IGF-I; 340 vs 205 ng/ml, P less than .20) than the Belgian Blue bulls. Growth hormone, insulin, IGF-I and testosterone were measured at 20-min intervals during two 24-h periods. In wk 6, Holstein bulls tended to produce more growth hormone than the Belgian Blues, as indicated by higher total peak area (3,185 vs 2,431 ng), peak amplitude (34.1 vs 22.6 ng/ml, P less than .10) and baseline (4.6 vs 3.3 ng/ml, P less than .20). In wk 27, the trends were opposite.(ABSTRACT TRUNCATED AT 250 WORDS)     

Endocrine and metabolic changes during altered growth rates in beef cattle

Eight steers from a group of 14 were fed ad libitum from 240 to 510 kg live weight, gaining at 1.4 +/- .2 kg/d. The six other steers were diet-restricted and grew at .37 +/- .09 kg/d from 240 to 307 kg, prior to ad libitum realimentation on the same diet to a final weight of 510 kg. Blood samples taken during the growth phases from both treatments were analyzed for insulin-like growth factor-I (IGF-I), triiodothyronine (T3), thyroxine (T4), glucose (GLU), nonesterified fatty acids (NEFA), and blood urea nitrogen (BUN) and (or) growth hormone (GH). During restricted growth, mean serum concentrations of GH were elevated (45.6 vs 23.4 ng/ml; P less than .05), serum concentrations of IGF-I decreased (108 vs 167 ng/ml; P less than .05) compared with control steers with ad libitum access to feed. Levels of T4 and GLU also were lower (P less than .05) during restricted than during normal growth. During early realimentation, levels of GLU (P less than .05), IGF-I (P less than .01), T4 and BUN (P less than .01) increased. Levels of T3 remained unchanged, whereas concentration of NEFA declined (P less than .001). Blood urea nitrogen decreased during early realimentation despite a large increase in diet protein intake and in protein storage, suggesting an increased efficiency of nitrogen use for protein synthesis. During realimentation, IGF-I levels rose above those of control steers and remained higher at the final weight of 510 kg (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of disulfiram in experimentally induced vitamin E deficiency myopathy in lambs

Vitamin E deficiency myopathy (white muscle disease) was induced in 14 suckling lambs (2 experiments; 7 lambs/experiment) by addition of cod liver oil to the diet. Disulfiram, an antioxidant, was administered orally once each day to 8 of the 14 lambs at 2 different doses. Serum creatine kinase (CK) activity was measured weekly for 5 weeks. Increased CK activity was evident in some lambs beginning at week 3. By week 4, serum CK was abnormally increased in 5 of the 6 nontreated lambs (ie, disulfiram not given) and in 4 of the 8 treated lambs. The combined disulfiram groups had significantly lower serum CK values during the study (P less than 0.05). Serum alpha-tocopherol, measured on samples from week 5 for lambs of experiment 1, was significantly higher in treated lambs (P less than 0.01). Microscopic examination of the vastus lateralis muscle indicated that the most severe lesions, consistent with nutritional myopathy, were seen in nontreated lambs. Therefore, disulfiram may have an antioxidant effect in lambs with vitamin E deficiency.     

Carcass composition and meat quality of equally mature kids and lambs

Carcass composition and meat quality attributes of 55 suckling kids (27 males and 28 females) and 57 suckling lambs (28 males and 29 females) of Portuguese native breeds were investigated. These suckling kid and lamb meats are European meat quality labels produced according to "Cabrito de Barroso- PGI" and "Borrego Terrincho-PDO" specifications, respectively. Female kids were slaughtered at 9.1 +/- 0.36 kg of BW, and male kids were slaughtered at 10.4 +/- 0.37 kg of BW, corresponding to 20.1 and 17.7% of maturity, respectively. Female lambs were slaughtered at 8.6 +/- 0.53 kg of BW, and male lambs were slaughtered at 9.9 +/- 0.23 kg of BW, corresponding to 19.9 and 17.1% of maturity, respectively. At 24 h postmortem, various yield and quality measurements were collected. The left sides of the carcasses were dissected into muscle, subcutaneous fat, intermuscular fat, and bone. Final pH, instrumental color (L*, a*, b*), carcass measurements, and kidney knob and pelvic fat were also determined. Samples of LM were taken from the lumbar and thoracic cuts for intramuscular and meat quality determinations. At 72 h postmortem, a sample of LM was used for cooking losses and Warner-Bratzler shear force determination. Suckling lambs had greater dressing proportion than suckling kids (P < 0.01). Carcass fatness was not affected by species (P > 0.05), but females had greater kidney knob and pelvic fat proportion than males (P < 0.01). Lambs had greater proportions of the highly valued leg cut and lower proportions of shoulder, anterior rib, and neck cuts than kids. Dissection results indicated that kid carcasses had greater muscle content and lower dissected fat and bone than lambs. Kids had greater (P < 0.001) muscle ultimate pH value than lambs (5.8 +/- 0.02 vs. 5.6 +/- 0.02). Males had greater (P < 0.05) muscle ultimate pH value than females (5.7 +/- 0.02 vs. 5.6 +/- 0.02). The kid meat was significantly lighter (P < 0.05) and less yellow (P < 0.001) than the lamb meat. Kids presented less cooking losses (P < 0.001) than lambs, and shear force value was significantly greater (P < 0.01) in lamb meat. The kid meat had significantly more moisture (P < 0.001) and less intramuscular fat content (P < 0.001) than lambs. At this maturity stage, there were significant differences on both carcass and meat quality attributes of suckling kids and lambs, possibly due to inherent differences between species.     

Influences of gender, time of castration, genotype, birthtype and feeding regimen on lamb longissimus fiber type proportions

Two trials examined genetic and environmental influences on muscle fiber type proportions. Trial 1 compared Polypay and Coopworth x Polypay male lambs either left intact or castrated early, mid or late in growth. Trial 2 compared Hampshire-sired lambs (females, early castrate wethers and late castrate wethers) from Suffolk x Coopworth dams and whiteface x Coopworth dams. Half the lambs in each trial were raised from weaning to 52 kg slaughter weight in drylot; the other half were reared to 41 kg on pasture before being finished in drylot. Analysis of longissimus tissue samples revealed no significant differences among rams, wethers and ewes in proportions of muscle fiber types. Early castration increased the proportion of alpha red fibers in Trial 1 (P less than .01) but not in Trial 2. Polypay lambs had a higher proportion of beta red fibers (P less than .05) than the Coopworth x Polypay lambs, but no differences were seen between the genotypes of Trial 2. Single-born lambs in Trial 1 had a 6% higher proportion of alpha white fibers (P less than .05) than twin-born lambs; however, this difference was not detected in Trial 2. Drylot lambs had a higher proportion of beta red fibers than pasture-reared lambs, the difference being 5% (P less than .01) in Trial 2. Muscle fiber type proportions were not found to be related to growth rate and carcass fatness, and no evidence of differential fiber transformation was found in this trial.     

湖羊与澳湖F1代羔羊短期育肥效果的比较

本研究以湖羊和澳湖F1代羔羊(澳洲白绵羊♂ × 湖羊♀)为研究对象,对其生长性能、屠宰性能、体组成和肌肉品质进行比较分析,综合评估湖羊与澳湖F1代羔羊育肥效果.随机选择湖羊和澳湖杂交F1代羔羊各61只,在相同的饲养环境和日粮下进行育肥和性能测定.饲养试验结束后立即屠宰,对试验羊只的生长性能、屠宰性能、体组成和肌肉品质等指标进行系统测定和比较.结果显示,湖羊和澳湖F1羔羊育肥期初始体重(0 d)、末期体重(60 d)无显著差异(P>0.05),全期平均日增重(ADG)、平均日采食量(ADFI)无显著差异(P>0.05),但在育肥前期(0～20 d)湖羊的ADG极显著高于澳湖F1代羔羊(P<0.01),而在育肥中期(20～40 d)和后期(40～60 d)澳湖F1代羔羊的ADG均显著高于湖羊(P<0.05).澳湖F1代羔羊的胴体胸围、臀围和眼肌面积显著大于湖羊(P<0.05).澳湖F1代羔羊的心脏重、肝脏重、肺脏重及其相对重(宰前活重)均极显著高于湖羊(P<0.01),但皮毛重、肾周脂重、肠系膜重、尾脂重及其相对重(宰前活重)均极显著低于湖羊羔羊(P<0.01).湖羊的熟肉率和屠宰结束后45 min肌肉pH极显著大于澳湖F1代羔羊(P<0.01),但澳湖F1代羔羊肌肉失水率、屠宰结束后24 h肉色b*2值和l*2值极显著优于湖羊(P<0.05).总体上来看,湖羊早期生长发育较快,但澳湖F1代羔羊后期生长潜力较大,且胴体性能优于湖羊,胴体脂肪沉积比湖羊少,肉用性能明显提高.     

Serum concentrations of IGF-I in postpartum beef cows

Four experiments assessed changes in serum IGF-I under various physiologic conditions in postpartum cows. In Exp. 1, anestrous suckled cows (n = 25) were infused for 6 d with either saline or glucose at two different infusion rates. In Exp. 2, anestrous cows (n = 29) received either a saline (weaned and suckled controls) or 3 g/d phlorizin (weaned phlorizin) infusion for 3 d. Calves from the weaned groups were removed from 15 h before and throughout infusions. In Exp. 3, cycling suckled cows (n = 20) received prostaglandin F2 alpha (PGF2 alpha) when the 5-d saline or phlorizin infusion began. In Exp. 4, suckled cows (n = 20) had ad libitum access to feed or received 50% of control feed consumption from 30 to 40 d postpartum. Increasing glucose availability (Exp. 1) increased (P less than .05) serum IGF-I by 30 to 35%. IGF-I remained stable after weaning (Exp. 2) in phlorizin-infused cows (128.8 +/- 12.7 ng/ml), but increased (P less than .05) by 3 d after calf removal in weaned control cows (152.2 +/- 7.5 ng/ml). IGF-I also remained stable in phlorizin-infused cows following PGF2 alpha injection (Exp. 3), but increased in control cows by 2 d after PGF2 alpha (156.8 +/- 18.3 on d 2 vs. 133.7 +/- 9.8 ng/ml pre-injection; P less than .05) and remained elevated (P less than .05) during the periovulatory period. In cows receiving restricted feed intake (Exp. 4), IGF-I decreased by approximately 50% within 4 d of feed restriction (71.3 +/- 9.4 vs 137.4 +/- 16.6 ng/ml; P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Enhanced skeletal growth of sheep heterozygous for an inactivated fibroblast growth factor receptor 3

Normal fibroblast growth factor receptor 3 (FGFR3) acts as a negative bone growth regulator by restricting chondrocyte proliferation and endochondral bone elongation. In sheep, a heritable mutation that inactivates FGFR3 produces skeletal overgrowth when homozygous, this condition is commonly referred to as spider lamb syndrome (SLS). We hypothesized that sheep heterozygous for the inactivated FGFR3 mutation (FGFR3(SLS/+)) would exhibit enhanced long bone growth and greater frame size; additionally, the isolated effects of increased bone growth would translate into greater BW and larger LM area relative to normal lambs at harvest. The current study investigated bone length and LM area of FGFR3(SLS/+) sheep at maturity and during growth. At maturity, FGFR3(SLS/+) ewes exhibited a larger frame size and longer bones than normal FGFR3(+/+) ewes (P < 0.05). Similarly, FGFR3(SLS/+) lambs had greater frame sizes than normal FGFR3(+/+) lambs, as indicated by increased metacarpal III length and height at withers (P < 0.05). The FGFR3(SLS/+) lambs took longer than the normal FGFR3(+/+) lambs to reach the 60-kg common BW harvest end point (P < 0.05). The FGFR3(SLS/+) lambs showed no difference in BW, ADG, or LM area at any age compared with normal FGFR3(+/+) lambs (P > 0.2). A similar LM area produced in the context of a greater frame size and skeletal length produces a greater muscle volume, thereby potentially increasing meat yield. The results of this study suggest that FGFR3(SLS/+) animals exhibit a relaxation of the normal inhibition of chondrocyte proliferation, resulting in an increase in the overall frame size. The sheep industry could utilize the naturally occurring genetic mutation in FGFR3 to potentially increase meat yields with enhanced skeletal growth as an alternative to exogenous growth promotants.