Infradian rhythmicity in lactogenic hormone (prolactin, growth hormone, cortisol and thyroid hormone) secretion throughout the lactation cycle in mithun cows (Bos frontalis): variation among strains. Issue 6 (1st November 2016) - Vupru, Kezhavituo
Abstract: The role of lactogenic hormones (prolactin, growth hormone, cortisol and thyroid hormone) on lactation yield in Mithun cows as well as their rhythmicity throughout the lactation cycle were studied in Mizoram ( n = 4) and Nagaland ( n = 7) strain of mithun ( Bos frontalis ). Blood samples were collected from all the animals from the day of calving to the complete dry off at an interval of 15 days. All the hormones were estimated in the serum by commercially available ELISA kits. Plasma level of cortisol (μg/dl), growth hormone (GH, in ng/ml), prolactin (PRL, in μIU/ml), triiodothyronine (T3, in nmol/μl) and thyroxin (T4, in ng/ml) were 20.84 ± 0.29, 28.08 ± 0.56, 9.87 ± 0.20, 27.82 ± 0.56 and 51.33 ± 0.48, respectively, in mithun irrespective of strains during the lactation period. Levels of all the hormones varied significantly ( p ≤ 0.01) during different days of lactation cycle but, there was no significant difference among strain. Levels of PRL, GH, cortisol and T3 were significantly ( p < 0.01) higher around calving and declined sharply. The hormones remained in almost steady state during mid-lactation and declined during late lactation. All the hormones stated above were positively correlated with lactational yield thus their role on lactogenesis and galactopoiesis was established.