Metabolismo hepático e sua influência no desempenho reprodutivo em bovinos

Abstract

Reproductive efficiency is the parameter that most affects the productivity and profitability of beef and dairy cattle production systems, and most gestational losses occur early during the first trimester of gestation. In the first experiment it was related to the nutritional condition, the metabolic and productive variables and their relation with the reproductive indices and it was observed that the metabolic variables influence on the reproductive performance since the transition period and that higher blood urea concentrations are related to animals with higher number of artificial inseminations and longer interval between calving and a new conception (mid-c group – 100 to 150 days and late-c group >150 days). In addition, early return to cyclicity does not assure a shorter interval between calving and a new conception, and the progesterone synthesis is directly related to cholesterol availability. The second experiment aimed to evaluate liver parameters and the influence on maternal recognition of pregnancy in beef cattle presenting natural ingestion of Senecio spp. The cows were divided in two groups: group 1 presenting GGT lower than 30 and group 2 GGT above 31 U/L. To evaluated liver health was used GGT status, cytological and histopathological exams that presented megalocytosis and binucleated cells and other findings suggestive of Seneciosis. The pregnancy rate was higher, CL diameter greater and concentration of progesterone on the cows from the group 1. However, no difference on body condition scores. Some cows presented a large CL on US scanning, high concentration of progesterone, and high ISG15 mRNA expression on Day 19, and it is an open cow on Day 45, that suggests us this cow had embryo loss beyond D19, indicating that cows are in the process of embryonic mortality and may allow a better identification of causes that may be related to corpus luteum insufficiency, and to be associated to a possible embryonic loss. In conclusion, although the different levels of liver damage do not alter the perception of body condition, they compromised the availability of progesterone necessary for embryonic survival and have the potential to impair maternal recognition of pregnancy. Thus, liver function determine the reproductive efficiency, and reflects the nutritional and metabolic condition of the animal.