Tetsuji Etoh

Effect of nutrient intake on intramuscular glucose metabolism during the early growth stage in cross-bred steers (Japanese Black male × Holstein female).

The objective was to investigate the impact of nutrient intake during the early growth period on the expression of glucose metabolism-related genes in skeletal muscle of cross-bred cattle. From 1.5 to 5 months of age, group H (n=7) animals were intensively fed a high-protein and low-fat milk replacer [crude protein (CP) 28%; ether extracts (EE) 18%; max: 2.0 kg, 12 l/day], and group R (n=7) animals were fed a restricted amount of normal milk replacer (CP 25%; EE 23%; max 0.5 kg, 4 l/day). From 6 to 10 months of age, group H cattle were fed a high-nutrition total mixed ration mainly prepared from grain feed, and group R cattle were fed only roughage. Blood samples were taken from each animal at three biopsy times (1.5, 5 and 10 months of age), and the blood plasma concentration of glucose and insulin was analysed. In glucose concentration, there were no significant differences; however, the concentrations of insulin were higher in group H than in group R at 5 and 10 months of age. Muscle samples were taken by biopsy from longissimus thoracis muscle (LT) at 1.5, 5 and 10 months of age. We analysed mRNA expression levels using the quantitative real-time polymerase chain reaction (PCR) assay for glucose transporters (GLUT1 and GLUT4), insulin receptor, phosphatidylinositol 3-kinase (PI-3K), protein kinase B (PKB, also known as Akt), hexokinase 1 (HK1) and tumour necrosis factor alpha (TNFα). Although no differences were detected at 1.5 and 5 months of age, at 10 months of age, GLUT1, HK1 and TNFα mRNA expression levels were significantly higher in group H than in group R. These results suggested Glut1 that affects insulin-independently mediated glucose uptake was more responsive to improved nutrition during early growth stage than GLUT4 that insulin-dependently mediated glucose uptake in LT of cattle.

Effects of nutritional status on hormone concentrations of the somatotropin axis and metabolites in plasma and colostrum of Japanese Black cows

We aimed to determine the effects of nutritional status on concentrations of somatotropic axis hormones (growth hormone (GH) and insulin-like growth factor 1 (IGF-1)), insulin and metabolites (glucose, total protein and nonesterified fatty acids (NEFA)) in the plasma and colostrum in late antepartum cows. Eight pregnant Japanese Black cows were randomly assigned to two experimental groups (n = 4 per group). Control cows (CON) received 100% of their nutritional requirements until parturition, whereas restricted group cows (RES) received 60% of their nutritional requirements. Blood samples were taken during the antepartum period, and blood and colostrum samples were collected on days 0, 1, and 3 after calving. Compared to the CON group, the RES group had higher concentrations of GH and NEFA in plasma, but significantly lower concentrations of glucose and insulin in plasma. The concentrations of GH in plasma after calving were significantly higher, but total plasma protein was significantly lower in RES than in CON cows. Compared to the CON group, the RES group had significantly higher concentrations of GH in colostrum, but significantly lower total concentrations of protein in colostrum. Concentrations of IGF-1 were not different between the two groups. These findings suggest that maternal nutritional status during late gestation influences concentrations of GH and total protein in the blood and colostrum of Japanese Black cows.

Effects of a high milk intake during the pre-weaning period on nutrient metabolism and growth rate in Japanese Black cattle

This study aimed to determine the effects of feeding an increased volume of high-fat milk during the early post-natal life on metabolite concentrations in the blood, the expression of key genes regulating intermediary metabolism in the skeletal muscles, and the rate of growth of Japanese Black cattle. All calves were fed a high-fat milk replacer (crude protein, 26%; crude fat, 25.5%; total dissolved nitrogen, 116%). Control calves (n = 4) were nursed with 500 g milk replacer until 3 months of age, whereas calves in the experimental group (n = 4) were nursed with 1800 g milk replacer until 3 months, and then the volume was gradually reduced until 5 months. Body weight was significantly higher in the experimental group than in the control group at 7 months. Plasma glucose concentrations were significantly lower in the experimental group. Expression of glucose-transporter-4 messenger RNA (mRNA) was lower, whereas that of glucose transporter 1, cluster of differentiation 36, and carnitine palmitoyltransferase-1b mRNA was significantly higher in the Longissimus thoracis of the experimental group. Nutritional status during early post-natal life appears to strongly influence the growth rate and glucose and lipid metabolism in Japanese Black cattle.

Higher Intake of Milk-Replacer Pre-Weaning Enhances Post-WeaningInsulin-Like Growth Factor 1 Levels in Japanese Black Cattle

Alterations in early pre-natal nutrition of Japanese Black calves influence the glucose and lipid metabolism after weaning. However, the effects of early nutritional status on the endocrine system in later life stages in Japanese Black cattle are unknown. This study examined how post-weaning plasma levels of growth hormone (GH), insulin-like growth factor 1 (IGF-1), and blood insulin, which are hormones affecting growth and meat quality, and metabolites were affected by feeding 1800 g versus 500 g of milk replacer to Japanese Black cattle (5 per group) during nursing. Up to weaning (90 days post-birth), all calves received calf starter and hay ad libitum, and post-weaning, they received a concentrate feed and hay ad libitum. Plasma concentrations of GH and IGF-1 were greater at weaning in the high-milk-replacer group (P<0.1 and P<0.01, respectively), and elevated IGF-1 concentrations persisted until the study end (210 d) (P<0.05), suggesting that the levels were sustained independent of the influences of both GH and nutrient intake. Blood insulin and metabolites (plasma glucose, beta-hydroxybutyric acid, and non-esterified fatty acids) were not significantly different between the two groups. The results of this study suggest that feeding calves a high volume of milk replacer during nursing will increase IGF-1 secretion well beyond weaning.