Comparative profiles of different lipoprotein cholesterol parameters and Growth Hormone during hot humid and winter season in Murrah Buffaloes

Now, it is well known that in bovines HDL-C act as substrate for ovarian steroidogenesis. The restriction of entry of other lipoprotein parameters is due to ovarian blood barrier, which restricts the entry of other lipoproteins, which are bigger in size. In vitro studies have indicated their role in mediating proliferation of cells. Besides gonadotropin, Growth Hormone (GH) is also gaining importance in the field of reproduction. GH receptors have been localized on the ovaries and follicle of bovines. Further it has been suggested that it can be the direct role of the hormone or it can be mediated through IGF-I. It has been assigned various roles in mediating follicle development, ovulation and corpus luteum maintenance. The river buffaloes are capable of breeding throughout the year, but during certain period of time were found to be more favourable than the others. It has been found that, winter season and hot humid season exhibit two extreme conditions of temperature variation; Hot humid season being unfavourable than the winter season because of high humidity and reasonably high temperature. It has been observed that during June to August months, conception rate and exhibition of estrus behaviour is low. This study was undertaken to analyze different lipoprotein cholesterol parameters namely Total cholesterol (TC), High-density lipoprotein cholesterol (HDL-C), Triglycerides (TG) and Low density lipoprotein cholesterol (LDL-C) in the plasma of cyclic Murrah buffaloes throughout the estrous cycle. The mean plasma concentration (mu g/ml) of different lipoproteins during hot humid season were TC 592 40, HDL-C 229 42, TG 345 95, LDL-C 285+/-94. Where as in winter season their concentrations were 1381.0+/-31.0, 1793.0+/-110.0, 511.0+/-21.0, 608.0+/-94.0 respectively. The mean+/-SEM circulatory level of GH was low during HH season than during winter (6+/-2 ng/ml vs, 17+/-2 ng/ml). During estrous cycle only one peak of GH was exhibited during hot humid season where as three peaks were exhibited during winter season. It can be concluded that winter season is favourable for maintaining physiological levels of hormones and metabolic parameters, which in turn may increase the reproductive efficiency of bovines. During winter season average temperature was 15 5 degrees C. During hot humid season average temperature was 34+/-3 degrees C. THI was more than 75%. (C) 2007 Elsevier B.V. All rights reserved.