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Impacts of an additional cooling event during the night on physiological and productive parameters of two breeds (B) of dairy cows under severe heat stress conditions were determined. Fifteen Holstein (H) and 15 Jersey x Holstein (JxH) cows were assigned to one of the two cooling strategies (CS), where the difference was an added 1 h cooling event during the night (i.e., 3X and 4X cooling events) with the 4X group having the added night cooling event. Maximum and minimum average temperature/humidity indices during the study were 86 and 77 units, respectively. There were no CS x B interactions for any response variable. Body condition score (BCS) was similar between CS, but H cows had higher (P

The present study is an analysis of scientific elements on the metabolism of ruminants: polysaccharides, proteins, and lipids. Where i) the fermentative digestion carried out by microorganisms, ii) the posruminal digestion and absorption and iii) the metabolism of each monomer is associated with the blood analytes that give us an approximation to the nutritional metabolism of the animal, also confer information on alterations and adjustments homeostatic. This review emphasizes the metabolism of monosaccharides, amino acids, and fatty acids. Therefore, the revised information aims to make the understanding of catabolic and anabolic processes in ruminant nutrition.

The objective of the present work was to quantify the concentration of non-esterified fatty acids, β-hydroxybutyrate, triacylglycerol and cholesterol during the negative energy balance, in Holstein cows. The study was carried out by sampling and analyzing 250 blood sera obtained from 50 Holstein cows. After delivery, the first sampling was performed at 7 d, the second at 15 d and the three remaining at 30, 45 and 60 d. Mean values for non-esterified fatty acids, β-hydroxybutyrate, triacylglycerol and cholesterol were determined. The resulting data set was analyzed by Gaussian distribution and descriptive statistics. Confidence intervals of 95% were established. The comparison between groups was carried out by Analysis of Variance and frequency histogram. The non-esterified fatty acids, β-hydroxybutyrate and triacylglycerol, are consistent with the values reported internationally. The cholesterol concentration showed a slightly higher value than the references. The AGNE did not present differences between groups, the β-hydroxybutyrate registered its highest value at 15 d postpartum, and lowest at 60 d postpartum. Triacylglycerol and cholesterol showed their highest concentration at 60 d postpartum, and the lowest at 15 d postpartum. The calculated confidence intervals could be used at the herd level to detect alert situations when at least 5% of the cows in the sample fall outside the reference range.