Cooling Holstein cows for 60 days prepartum in summer: effects on prepartum physiology, postpartum productivity, and calf growth.

Heat stress (HS) during the dry period of dairy cows in hot and dry conditions compromises the physiological status and mammary gland development of dairy cows, thereby negatively affecting milk component yield in the subsequent lactation. Our objective was to evaluate the effects of cooling Holstein cows under moderate or higher HS conditions (i.e., ambient temperature higher than 30 °C, with a temperature-humidity index of 78.2 units) during the dry period on prepartum physiological status, postpartum productivity, and calf growth. Twenty-four multiparous Holstein cows were divided into two groups: one with a cooling system based on spray and fans under a pen shade (CL, n = 12) and the other not-cooled (NC, n = 12). The cooling system operated 10 h/d (09:00-19:00 h) for 60 d prepartum. During the morning, rectal temperature and respiration frequency were lower in CL cows, but not in the afternoon, which was attributed to higher (P < 0.01) dry matter intake by CL cows. Total serum protein was higher (P < 0.01) in CL cows, but hemoglobin was higher in NC cows (P < 0.01), with no differences in other electrolytes, hormones, hematological components, and metabolites. Milk fat and fat and fat-protein corrected milk were higher (P < 0.05) in CL cows. Female and birth weight trended (P = 0.08) to be higher in CL cows. Cooling cows during the dry period had a limited effect on physiology prepartum but increased postpartum productivity of Holstein cows under hot and dry conditions.

Predicting carcass tissue composition in Blackbelly sheep using ultrasound measurements and machine learning methods.

This study aimed to predict Blackbelly sheep carcass tissue composition using ultrasound measurements and machine learning models. The models evaluated were decision trees, random forests, support vector machines, and multi-layer perceptrons and were used to predict the total carcass bone (TCB), total carcass fat (TCF), and total carcass muscle (TCM). The best model for predicting the three parameters, TCB, TCF, and TCM was random forests, with mean squared error (MSE) of 0.31, 0.33, and 0.53; mean absolute error (MAE) of 0.26, 0.29, and 0.53; and the coefficient of determination (R2) of 0.67, 0.69, and 0.76, respectively. The results showed that machine learning methods from in vivo ultrasound measurements can be used as determinants of carcass tissue composition, resulting in reliable results.

Reproductive performance of hair ewes and rams implanted with melatonin previous to the anestrus season in northwest Mexico.

Ovine reproductive behavior depends on annual photoperiodic cycle and its impact on endogenous melatonin secretion. In this regard, exogenous melatonin administration previous to the physiological anestrus period could modify the reproductive performance of sheep in the northwest of Mexico. Two independent studies were performed to evaluate such hypothesis in hair sheep implanted with melatonin prior to the anestrus season in latitudes 24° and 25° of Mexico. Study 1 involved 15 rams assigned to one of three treatments receiving 0mg (n=5), 18mg (n=5), or 36mg (n=5) of melatonin subcutaneously. Study variables were measured monthly since implantation (d0) and included testosterone concentration, scrotal circumference, mass motility, individual motility, and sperm concentration. Study 2 included 50 ewes assigned to one of two treatments receiving 0mg (n=25) or 18mg (n=25) of melatonin subcutaneously. In ewes, progesterone concentration and the frequency of females in anestrus were measured during the implantation (-30d), as well as at the beginning (0d) and at the end (45d) of the mating period, while pregnancy rate was determined by ultrasonography 45d after. Continuous variables were analyzed using a mixed effects model considering treatment, time, and the treatment by time interaction as fixed effects. Animal nested within treatment was the random effect. Binary variables were analyzed using the chi-square test. In males, melatonin improved testosterone and sperm concentrations (P<0.05), while in females, a 28% higher pregnancy rate was observed in implanted ewes (P<0.05). Therefore, melatonin enhanced reproductive parameters in both sexes and its exogenous administration previous to the anestrus season in northwest Mexico could be more effective in rams.

Estimation of Carcass Tissue Composition from the Neck and Shoulder Composition in Growing Blackbelly Male Lambs.

This study was designed to develop predictive equations estimating carcass tissue composition in growing Blackbelly male lambs using as predictor variables for tissue composition of wholesale cuts of low economic value (i.e., neck and shoulder). For that, 40 lambs with 29.9 ± 3.18 kg of body weight were slaughtered and then the left half carcasses were weighed and divided in wholesale cuts, which were dissected to record weights of fat, muscle, and bone from leg, loin, neck, rib, and shoulder. Total weights of muscle (CM), bone (CB) and fat (CF) in carcass were recorded by adding the weights of each tissue from cuts. The CM, CF and CB positively correlated (p < 0.05; 0.36 ≤ r ≤ 0.86), from moderate to high, with most of the shoulder tissue components, but it was less evident (p ≤ 0.05; 0.32≤ r ≤0.63) with the neck tissue composition. In fact, CM did not correlate with neck fat and bone weights. Final models explained (p < 0.01) 94, 92 and 88% of the variation observed for CM, CF and CB, respectively. Overall, results showed that prediction of carcass composition from shoulder (shoulder) tissue composition is a viable option over the more accurate method of analyzing the whole carcass.