Interrelationship of plasma leptin with energy metabolites,metabolic hormones and immunological changes.

The study was conducted to see interrelationship of plasma leptin with energy metabolites, metabolic hormones and immunological changes in pre and postpartum Sahiwal cows as influenced by some immunomodulators. For this thirty two pregnant dry Sahiwal cows were selected at sixty days prepartum and divided into four groups of eight cows each. Eight cows were kept as control, eight were supplemented with zinc @ 60 ppm/day/cow, eight were supplemented with vitamin E @ 1000IU/day/cow and other eight with combination of vitamin E @ 1000 IU/day/cow and zinc @ 60 ppm/day/cow during day sixty prepartum to day ninety postpartum. Blood samples was collected on day -60, -45, -30, -15, -7, -3, 0, 3, 7, 15, 30, 45, 60, 90 and 120 with respect to day of parturition. Body weight, body condition score, rectal temperature and respiration rate of experimental animals were recorded on the day of blood collection. Fortnightly dry matter intake was also recorded. Antioxidant enzymes (SOD, catalase and glutathione peroxidase) were estimated in blood lysate and plasma was analyzed for energy metabolites (glucose and NEFA), metabolic hormones (leptin, insulin, GH and cortisol), immunological parameters (TIg, IgG and IL-2), TBARS, total antioxidant activity, vitamin E and zinc. Milk yield was recorded daily up to 120 days of lactation. Milk samples were collected fortnightly from all cows for the estimation of milk composition (fat, protein, lactose and SNF), somatic cell count and Modified California mastitis test. Incidence of reproductive disorders such as retained placenta, metritis, day of first estrus after calving, number of artificial insemination per conception were recorded and incidence of mastitis was also recorded. The results confirm that DMI decreased during peripartum period and was lowest on the day of calving in all the four groups. The body weight decreased towards calving and was found to be lowest on the day of calving in all the four groups. In T3 group BCS was maintained significantly (P<0.05) followed by T2, T1 and control groups during the experimental period. Leptin levels decreased towards calving and remained low up to day 15 postpartum, after that the levels increased towards day 120 postpartum in all the groups. Overall mean value of GH of T3 group was higher (P<0.05) than T1, T2 and control groups. Insulin level decreased by 55.86%, 39.46%, 45.89% and 29.93% towards calving in control, T1, T2 and T3 groups, respectively. Cortisol levels began to increase towards calving and reached to maximum level on day of calving, after calving the levels decreased towards day 120 postpartum in all the groups. T3 group had significantly (P<0.05) higher glucose level than control, T1 and T2 groups, whereas overall mean of NEFA was significantly (P<0.05) lower in T3 than control, T1 and T2 groups. Overall mean of TIg and IgG was observed to be higher (P<0.05) in T3 than control, T1 and T2 groups. Levels of Interleukin-2 was higher (P<0.05) in T3 than control, T1 and T2 groups. Leptin levels were positively correlated with levels of insulin, glucose, TIg, IgG and IL-2, whereas, negatively correlated with GH, and cortisol. SOD, catalase and glutathione peroxidase were lower (P<0.05) in T3 than control, T1 and T2 groups. TBARS began to increased slightly from 60 days before calving and reached maximum on day 30 postpartum in control, whereas, maximum at 15 days postpartum in T1, T2 and T3 groups, after that value decreased towards day 120 postpartum in all the groups. Total antioxidant activity, vitamin E and zinc were higher (P<0.05) in T3 than control, T1 and T2 groups. Milk yield increased by 12.97%, 13.41%, and 24.93% in T1, T2 and T3 groups, respectively, in comparison to control. Milk fat%, milk protein%, milk lactose% and SNF% did not differ significantly between the groups. SCC, %SCM, mastitis, retained placenta, metritis cases were lower in T3 than control, T1 and T2 groups. Day of first estrus after calving was significantly lower in T3 in comparison to T1, T2 and control groups, whereas, number of artificial insemination per conception did not differ significantly in between groups. Therefore vitamin E and zinc supplementation increased the levels of insulin, leptin, glucose and immunity of cows, whereas minimise effect of oxidative stress during pre and postpartum period in Sahiwal cows. LIST OF ABBREVIATIONS