Direct heat stress-induced effects on rumen fermentation characteristics and nutrients degradability in sheep pair-fed alfalfa hay

Hassan S Mohamed-Ali,Mohamed A Al-Badwi,Emad M Samara,Aly B Okab,Ahmed A Al-Haidary,Khalid A Abdoun

doi:10.5424/sjar/2020183-16247

Hassan S Mohamed-Ali, Mohamed A Al-Badwi + Show 4 more

Open Access

https://doi.org/10.5424/sjar/2020183-16247

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Abstract

Aim of the study: To investigate the direct effect of heat stress on rumen fermentation characteristics and nutrients degradability of pair-fed rams to subsequently eliminate the confounding effects of dissimilar feed intake induced by heat stress exposure.Area of study: Saudi Arabia.Material and methods: Five rumen-cannulated desert rams (45 ± 1.63 kg body weight; 2–3 years of age) were placed individually in controlled climatic-chambers to be exposed to two successive periods. The 1st period was a control thermoneutral period (TN; 23.64 ± 0.14 °C; extended for 21 days) followed by a 2nd period of heat stress (HS; 44.26 ± 1.70 °C, for another 21 days). Each period was consisted of a temperature acclimation phase (7 days) and a data collection phase (14 days). Alfalfa hay was offered twice daily during both periods in a pair-fed manner (800 g DM per head and day).Main results: Exposing pair-fed desert rams to elevated ambient temperature had (p<0.05) elevated their respiration rate and skin temperature, without noticeable (p>0.05) changes in their rectal temperature. Most of the rumen fermentation characteristics and nutrients degradability were not affected by HS (p>0.05). However, exposure to HS increased (p<0.05) pre-feeding rumen total volatile fatty acids concentrations, pre-feeding molar proportion of acetate, and post-feeding rumen osmolality.Research highlights: HS had no direct effect on post-feeding rumen fermentation characteristics and nutrients degradability in desert sheep. This implies that strategic approaches to mitigate the adverse effects of HS have to be directed towards promoting feed intake and nutrients utilization under such conditions.

Highlights

Sheep are forced to induce several physiological changes when exposed to environmental challenges, which include decrease in feed intake and disturbance of nutrients metabolism (Rhoads et al, 2009; Wheelock et al, 2010; Adedeji, 2012; Wojtas et al, 2014), as well as reduction in blood flow to the rumen epithelium, thereby lowering ruminal motility, reducing saliva production and decreasing rumen pH (Kadzere et al, 2002; Yadav et al, 2012; Das et al, 2016)
The obtained results indicate the overall means of Ta and temperature humidity index (THI) were (p
The average calculated THI for HS period was 86.97 ± 0.98, suggesting that desert rams were exposed to severe heat stress during this period

Summary

Introduction

Sheep are forced to induce several physiological changes when exposed to environmental challenges, which include decrease in feed intake and disturbance of nutrients metabolism (Rhoads et al, 2009; Wheelock et al, 2010; Adedeji, 2012; Wojtas et al, 2014), as well as reduction in blood flow to the rumen epithelium, thereby lowering ruminal motility, reducing saliva production and decreasing rumen pH (Kadzere et al, 2002; Yadav et al, 2012; Das et al, 2016).

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