Inferring the recent ancestry of myostatin alleles affecting muscle mass in cattle.

Double muscling is an inherited condition in cattle characterised by large increases in muscle mass. Mutations in the myostatin (MSTN) gene, responsible for double muscling, were targeted in this study to estimate the time since the most recent common ancestor (TMRCA) for Q204X (p.Gln204*), E226X (p.Glu226*), 821del11 (c.821del11), E291X (p.Glu291*), C313Y (p.Cys313Tyr) and the more phenotypically moderate F94L (p.Phe94Leu) mutation. Genetic variability was examined in eight regions upstream and downstream of the MSTN locus. The molecular distance of the homozygous region associated with each MSTN allele was used to estimate the TMRCA. Long homozygous segments were associated with the MSTN alleles (mostly > 2 Mb), compared to short segments (130 kb) for cattle wild type at the double muscling and F94L sites. Estimates of time indicated that each MSTN allele had a recent common ancestor (<400 years ago). The results from this study, and the increasing frequency of these MSTN alleles in some cattle breeds, demonstrate recent positive selection.

Associations of feed efficiency with circulating IGF-1 and leptin, carcass traits and meat quality of lambs.

The aim of this study was to investigate the effects of feed efficiency classifications on live animal measurements, circulating IGF-1 and leptin concentrations, and carcass, non-carcass and meat quality traits of lambs. One-hundred and two lambs approximately 70 days-old with initial live weight of 24.6 ± 3.71 kg (mean ± SD) were individually fed for 56 days to determine residual feed intake (RFI) and residual feed intake and gain (RIG). Lambs were then classified as phenotypically Low-, Medium- or High-RFI and Low-, Medium- or High-RIG phenotypes. Circulating leptin and IGF-1 concentrations were higher in more efficient lambs (Low-RFI or High-RIG). Variation in RFI and RIG did not affect meat redness or tenderness, but High-RIG lambs had darker meat. These findings show that the phenotypically more efficient Low-RFI and High-RIG lambs produced carcasses with similar characteristics and meat quality as the less efficient High-RFI and Low-RIG lambs but have a strategic advantage of lower feed intake to achieve similar production outcomes.

An assessment of Walk-over-Weighing to estimate short-term individual forage intake in sheep.

The main limitation for determining feed efficiency of freely grazing ruminants is measurement of daily individual feed intake. This paper describes an investigation that assessed a method for estimating intake of forage based on changes in BW of ewes. A total of 24 dry and non-pregnant Romane ewes (12 hoggets, HOG; mean±SD 51.8±2.8 kg BW; body condition score (BCS) 2.6±0.2; and 12 adults, ADU; 60.4±8.5 kg BW; BCS 2.7±0.8) were selected for the study and moved from their rangeland system to a confined pen with controlled conditions and equipped with individual automatic feeders. The experiment lasted for 28 days (21 days adaptation and 7 days feed intake measurement). Ewes were fed hay and trained to use the electronic feeders (one feeding station per ewe) in which actual daily intake (H intake24) was measured. The pens were designed to maximize movement of trained ewes through an automated Walk-over-Weighing device, by using water and mineral salts as attractants. Total individual intake of hay measured in the automatic feeder at each meal (H intake) was compared with indirect estimates of feed intake determined using differences in the BW of the ewes (∆BW) before and 1 h following morning and afternoon feeding at fixed times. The BW, BCS, H intake, H intake24, as well as plasma non-esterified fatty acids (NEFA), glucose and insulin profiles were determined. The BW was higher in ADU v. HOG but BCS was not affected by parity. The H intake24 was affected by day of experiment as a consequence of reduced availability and intake of water on one day. Plasma glucose, NEFA and insulin were not affected by parity or day of experiment. The H Intake was and ∆BW tended to be higher in the morning in HOG, whereas H intake was and ∆BW tended to be higher in ADU at the afternoon meal. Irrespective of parity or feeding time, there was very strong correlation (r 2=0.93) between H intake and ∆BW. This relationship confirms that our indirect method of estimating individual forage intake was reliable within the strictly controlled conditions of the present experiment. The method appears suitable for use in short-term intensive group feeding situations, and has potential to be further developed for longer-term forage intake studies, with a view to developing a method for freely grazing ruminants.

The impact of gender and age on the nutritional parameters of alpaca (Vicugna pacos) meat, colour stability and fat traits.

Meat quality parameters for 50 huacaya alpacas, representing three age groups (18, 24 and 36months) and two genders (females and castrated males) were studied. Prior to chilling, samples of m. longissimus thoracis et lumborum (LL) were taken to determine isocitrate dehydrogenase activity and glycogen concentration, and further meat quality samples were taken after 24h. Alpaca meat has low levels (<1%) of intramuscular fat in the LL, m. semimembranosus and m. biceps femoris, but the level in the LL increases with animal age, with levels of desirable polyunsaturated fatty acids (PUFA) ranging from 96.3 to 136.4mg/100g. Lipid oxidisation post retail display ranged from 1.27 to 1.96MDA/kg meat. Colour stability testing indicated alpaca meat was relatively stable during retail display with day of display having no significant effect on lightness (L*), or the 630nm/580nm ratio. These results may relate to the high proportion (76%) of glycolytic and type IIX muscle fibres in LL.

Selection for increased muscling in Angus cattle did not increase the glycolytic potential or negatively impact pH decline, retail colour stability or mineral content.

This study determined the impact of selection for greater muscling in Angus cattle on myofibre characteristics, muscle enzymatics, retail colour stability, pH decline and mineral content of the semimembranosus (SM), semitendinosus (ST) and longissimus thoracis (LT). Muscle from 10 low muscled (low) and 11 high muscled (high) steers were analysed. The high steers had myofibres 22% and 24% larger in cross-sectional area in the SM and ST (P<0.05), and 8.6% less type IIX myofibres in the LT than the low steers (P<0.05). The highs had 4.9% lower lactate dehydrogenase activity, 10.2% and 12.3% higher citrate synthase and isocitrate dehydrogenase activity than lows (P<0.05). The highs had 27% more iron in the LT (P<0.05). The results indicate that the oxidative capacity of muscle can be maintained in more muscular cattle with no detrimental effects to mineral content, pH decline or retail colour stability. Myofibre hypertrophy is one mechanism leading to greater muscle mass of these high muscled cattle.

Longitudinal muscle gene expression patterns associated with differential intramuscular fat in cattle.

Intramuscular fat (IMF) can improve meat product quality through its impact on flavour and juiciness. High marbling cuts can command premium prices in some countries and grading systems, but there is substantial cost involved in choosing to grain feed animals in an effort to deposit more IMF. There would be value in developing methods to predict predisposition to 'marble' well. Unfortunately, the biological mechanisms underpinning marbling remain a mystery: the key adipocyte cell populations have not been defined, there are no reliable DNA markers, no known (if any) causal mutations and gene expression analyses in the main have tended to characterise increases in expression of end-point fat metabolism proteins such as the fatty acid-binding proteins. To shed light on expression-based markers of marbling potential, we contrasted LD gene expression in high IMF Wagyu cross animals with a low IMF Piedmontese cross at various time points. The expected divergence in the fat metabolism genes FABP4, THRSP, CIDEC and ACACA between the breeds occurs surprisingly late in postnatal development at about 20 months. On the other hand, divergent expression of WISP2, RAI14 and CYP4F2 was discovered in animals at or before 12 months of age, suggesting these genes may have potential as earlier predictors of marbling potential. In line with other researchers, we found intriguing links between IMF development and connective tissue remodelling. WISP2 - a novel adipokine highly expressed and secreted by adipose precursor cells and an inhibitor of the pro-fibrotic connective tissue growth factor - emerges as a particularly attractive candidate. It is relatively upregulated in high marbling Wagyu before admission to feedlotting, somewhere between 7 and 12 months. This difference is subsequently maintained until 25 months, but not thereafter. RAI14, thought to play a role in porcine adipocyte differentiation and with links to retinoic acid metabolism, has an unusual expression profile. Its expression level increases monotonically with postnatal development, and is always higher in Wagyu than Piedmontese. Strong, sustained upregulation of the anti-inflammatory CYP4F2 in Piedmontese is consistent with Wagyu adiposity being a pro-inflammatory state. Application of regulatory impact factor analysis, a network method for identifying causal effector molecules, suggests marbling roles for transcription factors previously implicated in (1) the formation of liposarcoma (unconstrained fatty masses) (YEATS4, MDM2), (2) adipogenesis (CREBL2, SP1, STAT1) and (3) inflammation (ISGF3G, HOXB13, PML).

Postweaning substitution of grazed forage with a high-energy concentrate has variable long-term effects on subcutaneous fat and marbling in Bos taurus genotypes.

The objective of this study was to quantify the effects and interactions of stage of growth and genotype on commercial carcass traits and intramuscular fat (IMF) content in 5 muscles of steers ( = 165) and to test the hypothesis that substituting pasture with a high-energy concentrate during the immediate postweaning period increases IMF. Cattle of 3 genotypes (Angus, Hereford, and Wagyu × Angus; = 55/genotype) were selected at weaning from commercial herds, targeting genotypic differences in marbling and subcutaneous fatness. Following weaning, steers were fed for 168 d within 2 different improved, temperate pasture-based nutritional systems: a forage-only system (FS) and forage with high-energy supplemented system (SS), with 2 replicates per system. The supplement was fed at a level of 1% of average BW adjusted every 2 wk to provide an estimated 50% of energy requirements for 168 d from weaning. Pasture on offer in both systems was managed to match the BW of the FS and SS steers during the postweaning treatment period to avoid confounding due to differences in growth rate during this period. Steers were then regrouped into 2 replicates and backgrounded on improved, temperate pasture for 158 d and then grain fed within 1 group for 105 d (short fed) or 259 d (long fed). Groups were slaughtered at commencement (d 0) and end of postweaning nutritional treatments (d 168), end of backgrounding (d 326), and after short (d 431) or long feedlotting (d 585). Serial slaughter stage had an effect on all traits assessed ( < 0.01). The FS steers had more rib fat ( < 0.01) and higher Meat Standards Australia marbling score ( < 0.05) and a tendency ( < 0.10) to have greater eye muscle area than the SS steers throughout the study. Genotypic differences were evident ( < 0.05) for all traits assessed except HCW, dressing percentage, rib fat depth, ossification score, ultimate pH, and IMF in the semitendinosus muscle. The results for marbling and IMF do not support the use of a high-energy feed as a substitute for an equivalent amount of energy from pasture during the immediate postweaning period to enhance development of marbling.

Organization and regulation of the gene encoding the sheep acid-labile subunit of the 150-kilodalton insulin-like growth factor-binding protein complex.

In adult animals, most circulating insulin-like growth factor I (IGF-I) and IGF-II is sequestered in a 150-kDa complex composed of 1 molecule each of IGF, IGF-binding protein-3 or -5, and the acid-labile subunit (ALS). Capture of IGF in ALS-containing complexes increases their circulating half-lives and concentrations and suppresses their hypoglycemic potential. ALS has been studied almost exclusively in rodents and primates, and no information exists in the sheep despite its extensive use to study the circulating IGF system. To initiate studies in the sheep, we isolated the ovine ALS gene and characterized its spatial and developmental regulation. The ALS gene spans about 3.0 kb of chromosomal DNA and consists of 2 exons interrupted by a 977-bp intron. Exon 1 encodes the first 5 amino acids of the signal peptide; exon 2 encodes the remaining 27 amino acids of the signal peptide and the entire mature protein of 579 amino acids. Transcription initiation occurs at nucleotides -58 and -29 (ATG, + 1), 2 sites that are not preceded by TATA or initiator sequences. A DNA fragment extending from -727 to - 11 of the sheep ALS gene directed basal expression of a luciferase reporter plasmid in the rat liver cell line H4-II-E. GH increased promoter activity by 1.8-fold, consistent with conservation in the sheep promoter of the GH response element previously identified in the mouse gene. A survey of adult tissues by Northern analysis revealed the presence of a 2.2-kb transcript only in liver. Weak expression was first detected in liver on day 130 of fetal life, increased suddenly on day 7 of postnatal age, and changed little thereafter. The sheep is a useful model to understand the regulation and role of ALS, particularly around the time of birth, when final maturation of the circulating IGF system occurs.

Influences on fetal and placental weights during mid to late gestation in prolific ewes well nourished throughout pregnancy.

This study investigated associations between fetal and placental weights from 85 to 130 days gestation in 49 fetuses from 21 ewes of a prolific genotype used as an experimental model of intrauterine growth retardation. The proportion of variation in fetal weight explained by placental weight increased from zero at 85 days to 91% (residual standard deviation (RSD) = 260 g) at 130 days. Overall, stage of pregnancy plus placental weight accounted for 96% of fetal weight variation (RSD = 212 g). Litter size and number of fetuses per uterine horn also influenced individual fetal weights. Gestational age, litter size, placental weight per ewe, and liveweight and condition score of ewes during early to mid gestation (initial LW and CS) explained 99.5% of the variation in fetal weight per ewe (RSD = 236 g). Most variation (86%) in placental weight was explained by stage of pregnancy, litter size, number of placentomes, and initial LW and CS (RSD = 53 g). Placental weight per ewe was influenced by stage of pregnancy, litter size and initial ewe LW and CS (R2 = 0.97; RSD = 89 g). The association of fetal and placental weights with initial ewe LW was positive, and with initial CS was negative. The results show that in the absence of overt nutritional restriction of pregnant ewes, fetal and placental weights are tightly coupled during late gestation and ewe fatness during early pregnancy is inversely related to placental and fetal weights. They demonstrate that placental weight explains most of the variation in fetal weight in the present intrauterine growth retardation model.

Intrauterine growth retardation is associated with reduced cell cycle activity, but not myofibre number, in ovine fetal muscle.

Cellular development of muscle was studied in sheep fetuses at 85 days of gestation. Large and small fetuses were compared at 100, 115 and 130 days, and an additional group of large 130-day fetuses were studied following 7 days of maternal undernutrition. Myogenesis in the peroneus longus muscle was completed between 100 and 115 days of gestation, and myofibre number did not differ between small and large fetuses. The proportion of myofibre-related nuclei identified as entering S-phase of the cell cycle was 1.7% per hour in 85-day fetuses. In large fetuses, subsequent rates were relatively constant (approximately 1.5% h(-1)), whereas in small fetuses cell cycle activity declined with age from 1.3 to 0.9% h(-1), and was 0.5% h(-1) in 130-day fetuses of restricted ewes. The constant rate of cell cycle activity in large fetuses was associated with an increasing estimated rate of muscle growth (peroneus longus (mg) = 0.831 x 10(0.024 x age [d]), r2 = 0.98), which contrasted with slow and relatively constant muscle accretion in small fetuses (8.4 mg day(-1)), and slower muscle accretion at 130 days in large fetuses from restricted ewes. Differences in DNA and RNA content in the semimembranosus muscle increased with age, large fetuses having 70% more muscle DNA, 108% more muscle RNA and 104% larger muscles than small fetuses at 130 days (all P<0.001). The results demonstrate that myonuclei accumulation, but not myofibre number, is associated with fetal growth in sheep and, therefore, with fetal nutrition during mid to late gestation.

An ultrasound-guided procedure to administer a label of DNA synthesis into fetal sheep.

A novel technique was developed to deliver a bolus dose of a DNA label into the peritoneal cavity of fetal sheep at 85-130 days gestation. Use of markers to identify the site of injection in fetuses from litters up to quadruplets, and immunohistochemistry to detect the DNA label, 5-bromo-2'-deoxyuridine (BrdU), confirmed the procedure was successful in 85% of cases. Duration of the procedure was (mean +/- SD) 44 +/- 16 min, and recovery from anaesthesia was rapid and uneventful in all cases. Fetal weight was estimated with a high degree of accuracy (residual standard deviation (RSD) = 297 g and r2 = 0.93, P<0.001) and the dose of label administered (110 +/- 33 mg BrdU/kg fetal weight) was adequate in all cases. BrdU detected in fetal nuclei following injection into amniotic fluid highlights the need for positive identification of the injection site in timed, short-term studies, and suggests potential to further develop the technique to investigate cellular events in fetal sheep younger than 85 days of gestation. The results demonstrate that the procedure can be used to determine in vivo whether or not nuclei have entered the S-phase of the cell cycle.

Effects of birth weight and postnatal nutrition on neonatal sheep: IV. Organ growth.

This study investigated effects of birth weight and postnatal nutrition on organ growth in neonatal lambs. Suffolk x (Finnsheep x Dorset) low- (mean +/- SD 2.29 +/- 0.34 kg, n = 28) and high- (4.84 +/- 0.45 kg, n = 20) birth-weight male lambs were studied. Lambs within each birth weight category were allocated to be individually grown rapidly (ad libitum fed, ADG 337 g, n = 20) or slowly (ADG 150 g, n = 20) on a liquid diet to live weights up to approximately 20 kg. All organs weighed less at birth in small than in large newborns (P < 0.001), except the adrenals (P = 0.10). At birth, as a percentage of empty body weight (EBW), small newborns had larger testes (0.14 vs. 0.10%, P = 0.023) and smaller thymus (0.17 vs. 0.37%, P = 0.009), and tended to have a larger heart (0.85 vs. 0.75%, P = 0.060) and a smaller spleen (0.10 vs. 0.14%, P = 0.054) than large newborns. During the first 2 to 3 wk postpartum, small newborns had greater fractional growth rates of organs than large newborns, most notably spleen, thymus, and liver. Postnatal growth of organs was more closely associated with EBW than age, except for lungs, testes, and stomach. At completion of rearing to 20 kg of live weight, small newborns had a spleen approximately 30% heavier than large newborns (P < 0.001). Testes weights were 37% and 24% greater in small newborns reared slowly and rapidly, respectively, compared with their high-birth-weight counterparts (P = 0.034). It was also evident that postnatal nutrition altered the mass of individual organs at the conclusion of the rearing period without affecting the combined weight of dissected organs. Slowly reared lambs had a larger pancreas (+27%, P = 0.002), stomach complex (+83%, P < 0.001), large intestine (+39%, P < 0.001), entire gastrointestinal tract (+18%, P = 0.002), and testes (+54%, P = 0.016) and tended to have a larger heart (+6%, P = 0.068) than their rapidly reared counterparts at 20 kg of live weight. Rapidly reared lambs had a larger thymus (+61%, P = 0.003), liver (+34%, P < 0.001), kidneys (+33%, P < 0.001), and small intestine (+17%, P < 0.001) and tended to have a larger thyroid (+13%, P = 0.054) at 20 kg of live weight than slowly reared lambs. The functional significance of the smaller thymus at birth and increase in spleen and testes weights at 20 kg of live weight in low- compared with high-birth-weight lambs warrants further investigation. It also remains to be established whether these differences at 20 kg of live weight persist.

Effects of birth weight and postnatal nutrition on neonatal sheep: II. Skeletal muscle growth and development.

This study investigated effects of birth weight and postnatal nutrition on growth and development of skeletal muscles in neonatal lambs. Low (L; mean +/- SD 2.289 +/- .341 kg, n = 28) and high (H; 4.840 +/- .446 kg, n = 20) birth weight male Suffolk x (Finnsheep x Dorset) lambs were individually reared on a liquid diet to grow rapidly (ad libitum fed, ADG 337 g, n = 20) or slowly (ADG 150 g, n = 20) from birth to live weights (LW) up to approximately 20 kg. At birth, weight of semitendinosus (ST) muscle in L lambs was 43% that in H lambs; aggregate weights of ST and seven other dissected muscles were similarly reduced. In ST muscle of L lambs, mass of DNA, RNA, and protein were also significantly reduced to levels 67, 60, and 34%, respectively, of those in H lambs. However, myofiber numbers of ST, tibialis caudalis, or soleus muscles did not differ between the L and H birth weight lambs and did not change during postnatal growth. During postnatal rearing, daily accretion rate of dissected muscle was lower in L than in H lambs. Accretion of muscle per kilogram of gain in empty body weight (EBW) was reduced in the slowly grown L lambs compared with their H counterparts, although the difference was less pronounced between the rapidly grown L and H lambs. Throughout the postnatal growth period, ST muscle of L lambs contained less DNA with a higher protein:DNA ratio at any given muscle weight than that of H lambs. Slowly grown lambs had heavier muscles at any given EBW than rapidly grown lambs. Content of DNA and protein:DNA ratio in ST muscle were unaffected by postnatal nutrition, but RNA content and RNA:DNA were greater and protein:RNA was lower at any given muscle weight in rapidly grown lambs. Results suggest that myofiber number in fetal sheep muscles is established before the presumed, negative effects of inadequate fetal nutrient supply on skeletal muscle growth and development become apparent. However, proliferation of myonuclei may be influenced by fetal nutrition in late pregnancy. Reduced myonuclei number in severely growth-retarded newborn lambs may limit the capacity for postnatal growth of skeletal muscles.

Effects of birth weight and postnatal nutrition on neonatal sheep: I. Body growth and composition, and some aspects of energetic efficiency.

We investigated the effects of birth weight and postnatal nutrition on growth characteristics of neonatal lambs. Low- and high-birth-weight male lambs were individually reared on a high-quality liquid diet to grow rapidly (ad libitum access to feed) or slowly (ADG 150 g) to various weights up to 20 kg live weight (LW). Average daily gain tended to be greater in the high- (mean+/-SE 345+/-14 g) than in the low- (329+/-15 g) birth-weight lambs given ad libitum access to feed owing to slower growth by the small newborns during the immediate postpartum period. At birth, on a weight-specific basis, small newborns contained 6.4% less nitrogen and tended to have more ash (8.9%) than the high-birth-weight newborns. Daily rates of fat, ash, and GE accretion were greater, and nitrogen accretion tended to be greater in the rapidly grown large newborns than in their small counterparts. At any given empty body weight (EBW) during rearing, low-birth-weight lambs contained more fat and less ash, resulting in slowly and rapidly grown small newborns containing 39.3 and 42.7 Mcal GE, respectively, at completion of the study (17.5 kg EBW), compared with 34.8 and 40.5 Mcal in their large counterparts. The differences in fatness and energy content between the birth weight categories are attributed to energy requirements for maintenance that were approximately 30% lower, coupled with higher relative intakes in the low-birthweight lambs, during the early postnatal period. At this time, the ability to consume nutrients in excess of lean tissue growth requirements was apparently more pronounced in small than in large newborns, which resulted in lower efficiency of energy utilization for tissue deposition. Furthermore, body composition differences between the slowly and rapidly reared lambs support the notion of a priority of lean tissue over fat when nutrient supply is limited.

Nutritional regulation of the genes encoding the acid-labile subunit and other components of the circulating insulin-like growth factor system in the sheep.

In sheep, perinatal maturation of the endocrine arm of the insulin-like growth factor (IGF) system is characterized by two developmental events. First, concentrations of circulating IGF-I increase rapidly after birth and become responsive to changes in nutrition and growth hormone (GH). Second, the liver initiates synthesis of a serum protein called the acidlabile subunit (ALS). The acid-labile subunit promotes the endocrine actions of IGF-I and -II by recruiting them to long-lived complexes of 150 kDa. In this study, we examined the effect of nutrition on hepatic expression of the ALS gene around the time of birth and later in life. Expression of genes encoding other components of the circulating IGF system was also measured. At d 130 of fetal life, fetuses suffering from chronic undernutrition caused by placental insufficiency had lower expression of the ALS and IGF-I genes than well-nourished fetuses, but they did not have any changes in the expression of the IGF-binding protein (IGFBP)-2 or IGFBP-3 genes. In early postnatal life, hepatic gene expression was analyzed between d 12 and 38 in lambs fed a milk replacer at levels sustaining weight gains of 150 or 337 g/d. The lower plane of nutrition decreased the expression of the ALS, IGF-I, and GH receptor genes and increased the expression of the IGFBP-2 gene; expression of the IGFBP-3 gene was not affected by nutrition at this stage of life. Finally, hepatic gene expression was measured in 3-mo-old lambs offered ad libitum levels of a balanced diet or of a diet limiting for both energy and protein. Although the rate of growth of the lambs fed the limiting diet was reduced by 38%, the only effect detected in hepatic gene expression was a ninefold increase in the abundance of IGFBP-2 mRNA. Overall, these results indicate that undernutrition during late fetal and early postnatal life delays hepatic expression of the ALS gene and final maturation of the endocrine IGF system.

Effects of birth weight and postnatal nutrition on neonatal sheep: III. Regulation of energy metabolism.

This study investigated effects of birth weight and postnatal nutrition on regulation of energy metabolism in the neonatal lamb. Low (mean +/- SD 2.289 +/- 0.341 kg, n = 28) and high (4.840 +/- 0.446 kg, n = 20) birth weight male Suffolk x (Finnsheep x Dorset) lambs were individually reared on a liquid diet to grow rapidly (ad libitum fed, ADG = 337 g, n = 20) or slowly (ADG = 150 g, n = 20) from birth to live weights (LW) up to approximately 20 kg. At birth, small newborns had higher plasma concentrations of urea nitrogen (mean +/- SEM 8.31 +/- 0.25 vs 6.39 +/- 0.32 mM, P = 0.002) and somatotropin (ST, 49.1 +/- 17.0 vs 10.8 +/- 4.3 ng/mL, P = .045) and lower IGF-I (36.1 +/- 6.8 vs 157.7 +/- 21.8 ng/mL, P < 0.001) than large newborns. Plasma glucose (1.42 +/- 0.23 vs 2.63 +/- 0.95 mM, P = 0.147) and insulin (0.09 +/- 0.02 vs 0.13 +/- 0.06 ng/mL, P = 0.264) concentrations did not differ. Urea nitrogen concentration in plasma peaked and then declined rapidly in all lambs during the first week postpartum, and plasma ST declined on a body-weight-related basis from birth. During rearing to 20 kg LW, plasma insulin was higher in low- vs high-birth-weight lambs. Lambs fed ad libitum had greater plasma concentrations of glucose, urea nitrogen, insulin, and IGF-I compared to those fed a restricted diet (ADG = 150 g). The results suggest that during the early postpartum period, newborn lambs exhibit the fetal characteristic of high rates of amino acid oxidation. The results also support the notion that, at birth, low-birth-weight lambs are less mature than high-birth-weight lambs in aspects of metabolic and endocrine development, which may enhance their capacity to utilize amino acids for energy production and to support gluconeogenesis during the immediate postpartum period. Being small at birth also resulted in elevated plasma insulin concentrations when adequate nutriment to support moderate or rapid growth was provided postpartum, although it remains to be elucidated whether this more chronic effect persists in the longer term.

Salivary and plasma cortisol as an index of stress in goats.

Total assayable cortisol in plasma was highly correlated (r = 0.97) with physiologically active free cortisol in plasma after routine management procedures in 1- to 3-weeks-old goats. Transport of adult goats caused significant increases (P less than 0.001) in free cortisol in saliva and in free and total cortisol in plasma. No difference (P greater than 0.05) between concentrations of free cortisol in saliva and in plasma was apparent before or after transport. The results demonstrated that the salivary cortisol method is a useful measure of stress in adult goats, and that the relationship between free and total cortisol in plasma, and the adrenocortical response to transport, appear to be similar in sheep and goats.

Prevalence of udder bacteria in milk samples from four dairy goat herds.

The prevalence of udder bacterial infections in 4 commercial goat herds in New South Wales was examined. Coagulase negative staphylococci were the predominant bacteria isolated being cultured from 13.3% of the 896 halves tested. Other bacteria isolated were Staphylococcus aureus (less than 1% of halves), streptococci (0.6%) and coliforms (2.0%). The low prevalence of udder bacteria contributing to the contamination of the milk was attributed to the milking management practices carried out in these herds, in particular pre-milking and post-milking antisepsis.

Prevalence, spread and control of caprine arthritis-encephalitis virus in dairy goat herds in New South Wales.

A study of the prevalence, spread and control of caprine arthritis-encephalitis virus (CAEV) in dairy goat herds in New South Wales (NSW) during 1986-1988 found that 56.8% of 1484 goats in 14 dairy herds were infected with CAEV. The prevalence of CAEV infection within most herds not implementing control measures increased during the study. At the end of the study, 59.7% of 1322 goats were infected. The prevalence of CAEV increased with age. Differences between breeds were less apparent. Within seven herds with a high standard of identification of goats, 149 of 812 goats seroconverted in an ELISA. Of these newly infected goats, 142 (95.3%) were > 1 yr of age and 96 (64.4%) were > 2 yr suggesting lateral spread of the virus. Most of the goats > 2 yr of age had been in the milking herd for a minimum of 3 to 6 months. The high seroconversion rate within the milking herd suggested that factors other than the ingestion of infected colostrum and milk before weaning were important for the spread of CAEV. Observations indicated that behaviour of goats, particularly reproductive behaviour among lactating does, and milking herd management practices are important in the spread of CAEV. A high density of livestock, poor livestock control and contamination of feed, water, equipment and personnel were implicated in transmission. Poorly functioning milking machines may also be involved. CAEV was eradicated from 3 herds by the implementation of strict control measures.

A disintegrin and metalloprotease-12 is type I myofiber specific in Bos taurus and Bos indicus cattle.

A disintegrin and metalloproteinase-12 (ADAM12) is involved in the regulation of myogenesis and adipogenesis and is of interest as a potential target to manipulate skeletal muscle development and intramuscular fat (IMF) deposition in cattle to increase beef yield and improve meat quality. The longissimus thoracis muscle (LM) and semitendinosus muscle (STM) from 5 Bos taurus (Angus) and 5 Bos indicus (Brahman) cattle were collected for histological and ADAM12 gene and protein expression analysis. Myofiber typing was used to determine if ADAM12 expression patterns related to differences in muscling and IMF deposition, which are influenced by proportions of the different myofiber types. The STM was found to contain a higher proportion of glycolytic myofibers than the LM, which contained a greater proportion of oxidative myofibers (myofiber ratio of glycolytic to more oxidative types in LM and STM of 1.1 and 3.5, respectively; P < 0.05). ADAM12 gene expression, fluorescent immunohistochemical staining for ADAM12, and image analysis found ADAM12 to be greater in the LM (P < 0.05). Regression analysis found a strong, positive relationship for the distribution of ADAM12 against the proportion of type I myofibers (P < 0.05, r(2) = 0.86). These findings suggest ADAM12 is upregulated in muscles with more slow-oxidative myofibres, such as the LM, and is linked to type I myofibers in cattle. ADAM12 may be important in the regulation and maintenance slow myofibers in the LM muscle.