Impact of Heat and Nutritional Stress on Rumen Fermentation Characteristics and Metabolic Activity in Bucks_Chaidanya.K_2010-20-108

                          ACADEMY OF CLIMATE CHANGE EDUCATION AND RESEARCH

                                                   Kerala Agricultural University

Title of Thesis               :Impact of Heat and Nutritional Stress on Rumen Fermentation Characteristics and Metabolic Activity in Bucks

Name of Student          :Chaidanya.K (2010-20-108)

Major Advisor               :Dr. G.  Girish Varma  

                                       (Chairman, Advisory Committee) Dean,

                                       College of Dairy Science and Technology,

                                       KVASU, Mannuthy

                                                                    ABSTRACT

A study was conducted to assess the combined effect of heat stress and nutritional restriction on rumen fermentation characteristics and metabolic activities in Osmanabadi Bucks. Twenty four adult Osmanabadi bucks (average body weight (BW) 16.0 kg) were used in the present study. The bucks were divided into four groups viz., C (n=6; control), HS (n=6; heat stress), NS (n=6; nutritional stress) and CS (n=6; combined stress). The study was conducted for a period of 45 days. C and HS bucks had ad libitum access to their feed while NS and CS bucks were under restricted feed (30% intake of C bucks) to induce nutritional stress. The HS and CS bucks were exposed to solar radiation for six hours a day between 10:00 h and 16:00 h to induce heat stress. The data were analyzed using repeated measures analysis of variance. The carboxy methyl cellulase (CMCase) Extracellular activity (EC), CMCase Intracellular activity (IC) and CMCase total activity (TA) of rumen liquor differed significantly (P<0.01) between the groups. The highest concentration of ammonia nitrogen (P<0.05) was recorded in C while the lowest in CS group. There were significantly (P<0.01) higher levels of trichloroacetic acid (TCA) in ad libitum (C and HS) fed groups as compared to restricted fed (NS and CS) groups. There were significantly (P<0.01) higher levels of total nitrogen in ad libitum (C and HS) fed groups as compared to restricted fed (NS and CS) groups. There were significantly (P<0.01) higher levels of propionic acid, butyric acid, and valeric acid in ad libitum (C and HS) fed groups as compared to restricted fed (NS and CS) groups. Further, the acetate and propionate ratio was significantly (P<0.01) higher in CS and NS groups as compared to C and HS groups. There were significantly (P<0.01) higher levels of plasma alkaline phosphatise (ALP) in ad libitum (C and HS) fed groups as compared to restricted fed (NS and CS) groups. However, plasma Aspartate amino transferase (AST) and alanine amino transferase (ALT) showed reverse trend (P<0.05) to plasma ALP. The highest (P<0.01) plasma Triiodothyronine(T3) and Thyroxine(T4) was recorded in C group as compared to stress groups (HS, NS and CS). Further, the highest leptin concentration was recorded in C group while the lowest level in CS group. The higher expression of rumen heat shock protein 70(HSP70) messenger Ribonucleic acid(mRNA) was reported in CS goats. Further, the higher expression of intestinal HSP70 mRNA was reported in HS goats. The thyroid alveoli showed significantly lower thyroglobulin activity in HS group. The length of rumen villi and thickness was reduced more in CS, whereas rumen keratinization was observed highest in CS group. It can be concluded from this study that when two stressors occur simultaneously, they may have severe impact on rumen fermentation characteristics and metabolic activities of bucks as compared to that would occur individually. Further, the study established the adaptive capability of Osmanabadi bucks to the detrimental effects of environmental stresses to alter their fermentation and metabolic activities. This is evident from the significant influences of interaction between treatment and experimental days on majority of the parameters studied.