The rumen consists of a complex ecosystem where nutrients consumed by ruminants are digested by fermentation process, which is executed by diverse microorganisms such as bacteria, protozoa, fungi, bacteriophage and oscillospira. A symbiotic relationship is found among different groups of microorganisms due to the diverse nature of these microbial species and their adaptability and interactions. The ruminant provides necessary environment for the establishment of such microorganisms, while the microorganisms obtain energy from the host animal through microbial fermentation end products. The rumen microbial ecosystem fulfills several functions like fibrolytic, lipolytic and proteolytic functions and produce metabolites including volatile fatty acids (VFA), biohydrogenated lipids, microbial protein, methane etc. The purpose of this review is to contribute a better understanding of the fermentation processes that are taking place in the rumen and to provide information that can be applied for the development of new nutritional strategies to improve the digestion process for achieving maximum production.

The study evaluated the effect of supplementation of rumen protected choline (RPC) and fat (RPF) alone and in combination, and injection Vit-E + selenium on feed intake, blood metabolic profile and postpartum fertility in transition Gir cows. Forty advanced (8 months) pregnant cows were divided into five equal groups (T1 to T5, n=8) and were managed individually from 30 days prepartum till 60 days postpartum. Cows in T1 group were fed basal diet, those in T2 to T5 groups received additional oral supplements of RPC @ 45 g/d (T2), RPF @ 80 g/d (T3), RPC + RPF as above (T4) and injection Vit-E 500 mg + Se 15 mg fortnightly (T5). The mean fortnightly dry matter intake increased significantly by days 0, 15 and 45 of lactation with higher overall value in T2 than other groups. The blood glucose levels were significantly higher on day of calving and dropped suddenly around day 15 postpartum in all groups. Plasma total cholesterol was significantly lower in T5 and T2, and higher in T4, and it declined significantly from 30 days prepartum till day of calving with lowest values on day 15 postpartum, which increased gradually till day 60 postpartum. The TAG and VLDL concentrations dropped 15-20 fold on day 0 and 15 postpartum over prepartum values, and again increased 5-10 fold on days 30 and 45 postpartum in most groups with higher values in T3, T4 and T5 than in T1 and T2 groups. BHBA levels were significantly increased on day 15 postpartum over day of calving or prepartum values, declined by day 45 postpartum, and were significantly higher in T2 and lower in T5 as compared to other groups. The uterine involution, first estrus postpartum and conception rates were significantly enhanced with all nutrient supplements, and T5 in particular.