Abstract
ObjectiveThis study was performed to evaluate whether ambient temperature and dietary glycerol addition affect growth performance, and blood metabolic and immunological parameters, in beef cattle.MethodsTwenty Korean cattle steers (405.1±7.11 kg of body weight [BW], 14.2±0.15 months of age) were divided into a conventional control diet group (n = 10) and a 2% glycerol- added group (n = 10). Steers were fed 1.6% BW of a concentrate diet and 0.75% BW of a timothy hay diet for 8 weeks (4 weeks from July 28th to August 26th and 4 weeks from August 27th to September 26th). Blood was collected four times on July 28th, August 11th, August 27th, and September 26th.ResultsThe maximum indoor ambient temperature-humidity index in August (75.8) was higher (p<0.001) than that in September (70.0), and in August was within the mild heat stress (HS) category range previously reported for dairy cattle. The average daily gain (ADG; p = 0.03) and feed efficiency (p<0.001) were higher in hotter August than in September. Glycerol addition did not affect ADG and feed efficiency. Neither month nor glycerol addition affected blood concentrations of cortisol, triglyceride, or non-esterified fatty acid. Blood concentrations of cholesterol, low-density lipoprotein, high-density lipoprotein, glucose, and albumin were lower (p<0.05) on August 27th than on September 26 th, and blood phosphorus, calcium and magnesium concentrations were also lower on August 27th than on September 27th. Glycerol addition did not affect these blood parameters. Percentages of CD4+ T cells and CD8+ T cells were higher (p<0.05) on July 28th than on August 27th and September 26th. The blood CD8+ T cell population was lower in the glycerol supplemented-group compared to the control group on July 28th and August 27th.ConclusionKorean cattle may not be significantly affected by mild HS, considering that growth performance of cattle was better in hotter conditions, although some changes in blood metabolic and mineral parameters were observed.
Highlights
The global-mean surface air temperature has increased by 0.6°C±0.2°C during the last 100 years [1]
It has been suggested that the addition of dietary glycerol and a direct-fed microbial could improve milk yield in dairy cows subjected to Heat stress (HS) [13]
We performed this study to examine whether ambient temperature and replacement of portions of corn sources with dietary glycerol in iso-energy levels affect growth, feed efficiency, blood metabolites, and immune cell populations in Korean cattle steers
Summary
This study was performed to evaluate whether ambient temperature and dietary glycerol addition affect growth performance, and blood metabolic and immunological parameters, in beef cattle. Steers were fed 1.6% BW of a concentrate diet and 0.75% BW of a timothy hay diet for 8 weeks (4 weeks from July 28th to August 26th and 4 weeks from August 27th to September 26th). Results: The maximum indoor ambient temperature-humidity index in August (75.8) was higher (p
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