Blood leptin concentrations in Japanese Black cattle

Changes in the liver transcriptome and physiological parameters of Japanese Black steers during the fattening period

We investigated the physiological changes during the fattening period and production characteristics in Japanese Black steers bred and raised using the typical feeding system in Japan. Here, 21 Japanese Black steers aged 12 months were used, with experimental period divided into early (12–14 months of age), middle (15–22 months), and late fattening phases (23–30 months). The liver transcriptome, blood metabolites, hormones, and rumen fermentation characteristics were analyzed. Blood triglyceride and non-esterified fatty acid concentrations increased, whereas blood ketone levels decreased, with fattening phases. Blood insulin increased with fattening phases and was positively correlated with carcass weight and marbling in late fattening phases. Rumen fermentation characteristics showed high propionate levels and low butyrate levels in late fattening phases, likely due to increased energy intake. Genes related to glucose metabolism, such as SESN3, INSR, LEPR, and FOXO3, were down-regulated in late fattening phases. Genes related to lipid metabolism, such as FABP4, were up-regulated, whereas FADS1 and FADS2 were down-regulated. These findings suggest that the physiological changes resulted from changes in the energy content and composition of diets. Liver metabolism changed with changes in fat metabolism. Insulin was strongly associated with physiological changes and productivity in Japanese Black cattle.

Association of leptin gene polymorphism with economic traits in crossbred cattle

The present investigation was carried out to identify two polymorphisms in leptin gene by PCR-RFLP and to examine the possible association of the identified genotypes with growth, production and reproduction traits in 205 female crossbred cattle (½ Holstein Friesian × ½ Hariana). One fragment of 330 bp comprising partial intron 2 and exon 3, and another fragment of 94 bp comprising partial exon 2 of leptin gene were amplified, and digested with HphI and Kpn2I restriction enzymes, respectively, for identification of genotypes. The animals with HphI-RFLPCT and Kpn2I-RFLP-AV genotypes had significantly higher birth weight than the HphI-RFLP-CC and Kpn2IRFLP- AA genotypes respectively. The HphI-RFLP locus had significant effect on body weight at 12 months of age, age at first calving and average daily milk yield, while, Kpn2I-RFLP had significant effect on first lactation milk yield and average daily milk yield. Therefore, leptin gene could be used as a marker for genetic selection of economic traits in cattle.

The relationships between leptin and vitamin A levels in plasma of fattening cattle supplemented with vitamin A

The objective of this study was to examine the effect of dietary vitamin A (retinol) on leptin in cattle. The relationship between plasma leptin and insulin was also examined. The experiment studies 16 9-month-old steers over the following 20-month fattening period. Four treatment diets were given to four steers in each of four groups. Cattle in treatment A were given a diet high in vitamin A (9000 to 10500 µg/day) throughout the experiment. Cattle in treatment B were given a diet low in vitamin A (300 to 4500 µg/day) for 0 to 10 months, after that they were given the high vitamin A diet during the period 10 to 20 months. Cattle in treatment C were given the low vitamin A diet for 0 to 14 months, after that they were given the high vitamin A diet for the period 14 to 20 months. Cattle in treatment D were given the low vitamin A diet throughout the experiment. Plasma samples were collected at 2-month intervals during the experiment to determine the plasma leptin, insulin and vitamin A concentrations. Plasma leptin concentration significantly increased over the fattening period (P< 0·001) but did not differ between the treatments (P> 0·05). Plasma leptin concentration was positively correlated with insulin concentration (r = 0·44,P< 0·001), although it was not correlated with plasma vitamin A concentration (r = –0·01,P> 0·05). It was concluded that dietary vitamin A in cattle does not affect plasma leptin concentration.

Plasma leptin concentration in pre- and post-weaning lambs

Leptin has an important rôle in the control of appetite and energy expenditure. Several studies have reported the effects of leptin in ruminants. However, little is known about changes in circulating leptin concentrations in neonates of ruminant species, or the effects of weaning on plasma leptin concentrations. The main objectives of this experiment were: to examine plasma leptin concentrations in lambs, in the period from just after birth through to weaning; to examine the effect of weaning on plasma leptin concentrations, and to compare leptin concentrations measured using a ‘multi-species’ leptin radio-immunoassay (RIA) kit and a specific ovine RIA in lambs during the 6-month period after weaning. In a previous paper, we reported leptin concentrations using a commercial RIA during the post-weaning period. However, we were not able to measure plasma leptin concentrations from just after birth to weaning as they were apparently below the level of sensitivity of the assay. In the present study, five crossbred lambs were removed from their dams within 2 days after birth, and bottle-fed on milk replacer at a level sufficient to meet a 1•2 times maintenance metabolizable energy intake. Lambs were weaned 45 days after birth, and housed individually in pens. The lambs were offered timothy hay, rolled barley and soya-bean meal to meet a 200 g daily gain during the post-weaning period. During the pre-weaning period, blood samples were collected within 5 h of birth and thereafter at 09:00 h; every day from 2 to 6 days of age; at 2-day intervals from 6 to 14 days of age; and at 3-day intervals from 14 to 45 days of age. During the post-weaning period, blood samples were collected before and 3 and 6 h after the morning meal at the ages of 0•5, 1, 2, 3, 4, 5 and 6 months. Plasma leptin concentrations slightly increased (P < 0•05) just after birth and then remained constant until 45 days old (P > 0•05). Additionally, plasma leptin concentration was not significantly changed following weaning. During the post-weaning period, plasma leptin concentrations were compared using two RIA systems. The correlation between plasma leptin concentrations measured by the ‘multi-species’ leptin RIA kit and specific ovine RIA was poor (r = 0•41). These findings are consistent with other reports and suggest that the ‘multi-species’ leptin RIA kit is not suitable for estimating leptin plasma concentrations in ruminants.

The relationships between leptin and insulin in blood plasma of growing lambs

The present study was designed to examine the pattern of changes in plasma leptin concentration during the early stage of young ruminants. Five crossbred lambs weaned at 45 days were housed individually in pens. The lambs were offered timothy hay, rolled barley and soya-bean meal to meet a 200 g daily gain, and were given free access to water and mineral block. Blood samples were collected just before the morning feeding and at 30-min intervals for 6 h after the morning feeding beginning at 0·5 months after weaning and thereafter monthly for the next 6 months. Plasma leptin level increased dramatically from 0·5 to 3 months after weaning. Thereafter, it dropped to a similar level to that at 2 months after weaning and remained at that level. Moreover, plasma leptin level was not affected by feeding, and no variation throughout the day of sampling was observed. Plasma insulin levels showed similarity to changes in plasma leptin levels. Plasma insulin levels were positively correlated (r = 0·63) with plasma leptin levels. This study shows that plasma leptin level dramatically increases after weaning. Additionally, it suggests that insulin contributes to the increase of leptin with growth in lambs.