Effects of heat stress on

Abstract

Context Interest in studying heat stress (HS) has increased significantly due to the problems associated with increasing global warming. Heat stress has very destructive effects on the health and performance of livestock. Aims Our objective was to investigate the effects of heat stress on in vivo and in vitro ruminal metabolism in fat-tailed Iranian sheep. Methods Fourteen intact non-lactating and non-pregnant mature fat-tailed Makoei ewes (67.5 ± 2.5 kg BW) were kept indoors for 24 h/day and randomly assigned to HS (33.0–41.0°C and a temperature–humidity index (THI) of ≥83 for 24 h/day) or thermoneutral (TN; 24.5 ± 2.3°C and a THI of 66.1 ± 2.5) condition in two consecutive experimental periods. At the end of first experimental period, the animals in each group were exchanged with another group. The ewes were fed a total mixed ration two times a day, composed of lucerne hay (33%) and corn silage (1:2) to meet their maintenance metabolisable energy and protein requirements. Key results HS ewes had lower dry-matter (DM) intake than did TN ewes (P < 0.05). HS increased the in vivo DM, organic matter (OM) and neutral detergent fiber digestibility (P < 0.05), but crude protein digestibility was not affected. Total volatile fatty acid concentration and pH were not affected by HS. However, propionate molar percentage was increased and N-NH3 concentration was decreased by HS. In vitro gas production of three different tested feeds was lower in rumen fluid collected from HS than that from TN group, but DM and OM digestibility and methane emission were decreased only in the case of Orchard grass (P < 0.05). Conclusions and implications In general, HS had detrimental effects on DM intake and in vitro nutrient digestibility but increased in vivo nutrient digestibility, and changed microbial population.

Effects of Feeding a Commercial Starch Binding Agent during Heat Stress on Enteric Methane Emission, Rumen Volatile Fatty Acid Contents, and Diet Digestibility of Merino Lambs

“…Regardless of the period and diet, acetate and iso-valerate did not show any significant variation. Contrary to our results, a difference in the concentrations of acetate and isovalerate due to heat stress was observed in goats [13,51] and sheep [52]. Further, propionate production was lower during P2 and P3 compared with P1, which would have played a beneficial role in reducing the heat increment [49].…”

Influence on the fermentation quality, microbial diversity, and metabolomics in the ensiling of sunflower stalks and alfalfa

“…Research indicates that ensiling sunflower stalks can decrease the content of NDF and increase Acid Detergent Lignin (ADL) (Gholami-Yangije et al, 2019). These findings are inconsistent with our experiment.…”

“…As can be seen from Table 2, with the increase of alfalfa ratio in all treatments, the CP gradually increases, an outcome that can be anticipated. Research conducted by Gholami-Yangije et al (2019) suggests that ensiling can increase the crude protein content in sunflower residues. This aligns with the results of our experiment, where there is a gradual increase in crude protein content during the fermentation of A2S8 and A4S6 (p>0.05).…”

“…However, sunflower silage has a higher content in acid detergent fiber and lignin than alfalfa and maize silage, in this condition it can not completely replace normal dietary feeds (Pereira et al, 2007). Gholami-Yangije et al (2019) thought that there was no effect on milk production and composition of dairy goats when sunflower silage replaced a certain percentage of diet. Therefore, in order to reduce the negative effects of sunflower silage, there may be a feasible solution in using sunflower straw mixed with high quality pasture in specific proportions for silage.…”

Folic Acid and Taurine Alleviate the Impairment of Redox Status, Immunity, Rumen Microbial Composition and Fermentation of Lambs under Heat Stress

“…Similar to this finding, the content of NH 3 -N was decreased markedly by HS, which may be due to the imbalance of the proteolytic bacteria and NPN-utilizing bacteria caused by the high ambient temperature. The decrease of pH can also confirm this, because a variety of bacteria that were susceptible to the low pH can be repressed [47,48]. However, the supplementation of folic acid and taurine significantly decreased the ratio of acetate/propionate and elevated the concentration of NH 3 -N, compared with the MHS and SHS groups, which mirrored the observation that the folic acid and taurine can effectively protect the microbial fermentation in rumen from the deleterious influence of HS.…”