Interrelationship between diseases and calving season and their impact on reproductive parameters and milk production of tropical dairy cows.

The interactions between calving season, the occurrence of retained placenta, intrauterine infections (IUI), and early mastitis, and their effects on the reproductive performance and milk yield of Holstein-Friesian cows in a tropical environment were studied using data from 3320 calvings (1948 cows) from two farms in El Salvador. Based on environmental conditions, season of calving was categorized into: quadrimester 1 (November-February), quadrimester 2 (March-June), and quadrimester 3 (July-October) where quadrimester 2 and 3 had the highest ambient temperature and relative humidity, respectively. Cows were classified into 1, 2, and 3 + parities. The effects of quadrimester and of diseases on days to first service, services per conception, days open, interval between services and 305-day milk yield were studied in separated multivariate regressions. The likelihood of experiencing a disease contingent on the calving season and the likelihood of a cow being culled due to poor fertility associated with experiencing a disease were evaluated using logistic regression. Cows calving in quadrimester 2 and 3 were more likely to suffer from IUI and showed poorer reproduction than cows calving in quadrimester 1. Reproduction was more strongly affected by IUI. Mastitis increased the days to first service, days open, and interval between services. Mastitis and IUI also caused a lower 305-day milk yield. Overall, hotter and more humid conditions lead to higher incidence of disease and poorer reproductive performance. The physiological responses that lead to these phenomena should be further studied to understand the interactions between diseases, environmental conditions and reproduction.

Permeability and changes in carbohydrate moiety in rat endometrial epithelium during oestrus as revealed by ruthenium red.

We have used four different methods of ruthenium red (RuR) staining (RuR-Lumen, RuR-Glu, Glu/CB-RuR and RuR-OsO4) in order to study the permeability of the uterine epithelial cells of the rat during oestrus. The best results were obtained with the application of RuR-OsO4, and this test was used for the statistical analysis. In addition, the dialyzed iron and diamine test (HID) techniques corroborated the nature of the acid glycoconjugate part of luminal surface of the uterine epithelium stained by the RuR. By means of the Thiéry technique we detected the presence of neutral glycoconjugates. These results, together with statistical analysis, lead us to suggest a) that the uterine epithelial cells present a greater permeability to RuR during early oestrus (Stage II) than during the later part (Stage III) and b) that sulphate group-bearing glycoconjugates decrease in the course of the oestrus, whereas the neutral glycoconjugates remain constant.