Relation of the maximum temperature and relative humidity close to the insemination with the tropical milking criollo heifer's gestation in three seasons

Growth performance, carcass, and meat quality traits of Tropical Milking criollo bulls fed with two energy-level diets

The aim of this study was to determine the effect of two energy-level diets on the beef performance of Tropical Milking criollo bulls grouped by weight and age in three periods: initial, middle, and final. Evidence on intensive beef production from Tropical Milking criollo cattle breeds are unknown, and productive alternatives for dairy producers in the hot tropics are needed. Bulls were fed in each period with low (LE, 2.2 Mcal ME/kg DM) and high (HE, 2.9 Mcal ME/kg DM) energy diets and content phase feeding protein of 14.5, 12.0, and 10.3%, respectively. For each period, ten bulls were randomly assigned to diets. In all periods, growth performance for final body weight, average daily gain, feed intake, and feed conversion were all superior in HE (p ≤ 0.05). For the final period, slaughter body, hot and cold carcass weights, and dressing were also superior in HE (p ≤ 0.05); for meat quality traits, differences were observed in muscles Longissimus dorsi, Semimembranosus, Infraspinatus, and Serratus ventralis for pH and tenderness (p ≤ 0.05), although not for diets. For color L*, a*, and b* system, neither diet nor muscle had effect on L* (p > 0.05); however, the diet-muscle interaction was significant for a* (p ≤ 0.05), and only muscle effect was detected for b* (p ≤ 0.05). Tropical Milking bulls responded positively to a high-energy diet, despite not being a beef breed.

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.