S Shrifi, H Rahmani, M Motamedi,
Volume 13, Issue 47 (4-2009)
Abstract
In dairy cattle, the increase in milk yield has been accompanied by a more negative energy balance during early lactation and a decrease in fertility. The 167 amino acid protein product of the ob gene was named leptin (derived from the Greek term ‘leptos’ meaning thin). The leptin hormone, as a 16-kDa protein is synthesized mainly by adipose tissue and is involved in regulation of food intake, energy balance, fertility and immune function. The expression and secretion of leptin are correlated with body fat mass and are acutely affected by changes in food intake. The objective of this study was to investigate the fluctuations of leptin concentrations during late pregnancy and early lactation, the effect of parity and BCS on plasma leptin concentration, and to investigate its fluctuation effects on reproductive status. Blood samples of 54 Holstein cows were taken at a fixed time of the day after milking but before feeding, from 2 weeks before calving until 6 weeks after calving. BCS and plasma leptin concentration were measured at 2-wk intervals. Leptin concentrations were affected by parity. Primiparous cows and cows in first parity had higher leptin concentrations compared with multiparous cows (P<0.05). Leptin concentration was not different in late pregnancy and early lactation. BCS was negatively correlated with plasma leptin concentration (P<0.05). Plasma leptin concentration did not influence reproductive traits (days in milk at first breeding, service per conception and open days).
E Mahjoubi, H Amanlo, D Zahmatkesh,
Volume 13, Issue 47 (4-2009)
Abstract
In order to examine the effects of increasing concentrations of beet pulp (lipogenic nutrient) substituted for barley grain (glycogenic nutrient) on productive performance, body condition score loss, and blood metabolites, 18 Holstein cows were used in a randomized complete block design. The cows were blocked based on parity. The cows were 171 ± 16 d in pregnancy, 2.76 ± 1.14 parity, and 289 ± 35 d in milk at the beginning of the experiment. The cows' body condition scores were 4.12 ± 0.35 at the beginning of the trial. The cows were assigned randomly to three dietary treatments containing 1) 23.47% barley (0% beet pulp), 2) 14.87% barley (8.6% beet pulp), or 3) 6.27% barley (17.2% beet pulp). Substituting beet pulp for barley grain didn't affect FCM 3.5%, milk protein, lactose, total solid, and SNF percentage, but milk fat percentage (4.37, 4.91, and 5.18, P < 0.003) and milk energy (0.76, 0.82, and 0.84 Mcal/kg, P < 0.02) increased as beet pulp was replaced with barley, respectively. A tendency was detected for a more negative body condition score change (0.13, -0.09, and -0.12, P < 0.13) and back fat thickness (2.5, -0.4, and -1.6 mm, P < 0.13) with added beet pulp. Plasma glucose (65.83, 58, and 57.16 mg/dl, P < 0.01) and cholesterol (157.33, 122.4, and 120.8 mg/dl, P < 0.03) decreased as beet pulp was substituted for barley grain, respectively. No difference was found in the plasma content of insulin and NEFA between treatments. Considering these results, it appears that with inclusion of beet pulp in fat cows diet during late lactation may slightly reduce body condition score safely and inhibit concomitant low production with diet diluting.
