Butyrate is produced by microbial fermentation in the large intestine of humans and animals. It serves as not only a primary nutrient that provides energy to colonocytes, but also a cellular mediator regulating multiple functions of gut cells and beyond, including gene expression, cell differentiation, gut tissue development, immune modulation, oxidative stress reduction, and diarrhea control. Although there are a large number of studies in human medicine using butyrate to treat intestinal disease, the importance of butyrate in maintaining gut health has also attracted significant research attention to its application for animal production, particularly as an alternative to in-feed antibiotics. Due to the difficulties of using butyrate in practice (i.e., offensive odor and absorption in the upper gut), different forms of butyrate, such as sodium butyrate and butyrate glycerides, have been developed and examined for their effects on gut health and growth performance across different species. Butyrate and its derivatives generally demonstrate positive effects on animal production, including enhancement of gut development, control of enteric pathogens, reduction of inflammation, improvement of growth performance (including carcass composition), and modulation of gut microbiota. These benefits are more evident in young animals, and variations in the results have been reported. The present article has critically reviewed recent findings in animal research on butyrate and its derivatives in regard to their effects and mechanisms behind and discussed the implications of these findings for improving animal gut health and production. In addition, significant findings of medical research in humans that are relevant to animal production have been cited.

Objective-To examine the hypothesis, in a community not studied before, that insulin resistance associated with centralised adiposity is the mechanism underlying the predisposition of Asian immigrant communities to both ischaemic heart disease and diabetes mellitus.Design-Cross sectional study within one socioeconomic stratum.Setting-Two factories in the textile sector in Bradford, West Yorkshire.Subjects-Male manual workers of Asian (110) and non-Asian origin (156) aged 20-65 years.Results-Diabetes was almost three times more prevalent in the Asian group. Two hours after an oral glucose load Asian men had double the serum insulin concentrations of non-Asian men (p < 0 0001). Asian men also had significantly lower concentrations of plasma total cholesterol (p < 0 03), high density lipoprotein cholesterol (HDL) (HDL2, p < 0-0001; HDL3, p < 0-0001), and apolipoprotein AI (p < 0 0001). Fasting plasma triglyceride concentrations were slightly higher (p = 0 072) in the Asian men; thus the ratio of triglyceride cholesterol was higher (p = 0 006). The interrelation between serum insulin and plasma lipid concentrations indicated metabolic differences between the ethnic groups. Insulin concentrations were associated with cholesterol concentrations in the Asian men only and there was a lack of association between triglyceride, low density lipoprotein cholesterol, and HDL cholesterol in this group. The risk marker profile in the Asian men was therefore quite different to that of their non-Asian counterparts and was associated with a greater tendency to centralised adiposity.Conclusion-These data support the insulin resistance hypothesis and thus have important implications for

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The objective of this study was to investigate the effect of short-term elevated ambient temperature on ruminal volatile fatty acid (VfA) dynamics and rumen epithelium gene expression associated with the transport and metabolism of VFA. Eight ruminally cannulated Holstein heifers (200 kg) were used in a factorial, repeated measures experiment with two treatments and two periods. During the first period, animals were provided with feed ad libitum and housed at 20 °C. During the second period, one group (HS) was housed at 30 °C and fed ad libitum. The other group (PF) was housed at 20 °C and pair-fed to match the intake of the HS group. During each period, animals were kept on treatment for 10 day, with sample collection on the final day. In the second period, indicators of heat stress were significantly different between PF and HS animals (P < 0.05). There was a thermal environment effect on butyrate production (P < 0.01) that was not associated with feed intake (P = 0.43). Butyrate absorption decreased in HS animals (P < 0.05) but increased in PF animals (P < 0.05) from period 1 to period 2. There was a feed intake effect on BHD1 expression (P = 0.04) and a tendency for a thermal environment effect (P = 0.08), with expression increasing in both cases. Expression of MCT4 was affected by feed intake (P = 0.003) as were all NHE genes (NHE1, NHE2, and NHE3; P < 0.05). These results indicate that with low feed intake and heat stress, there are shifts in rumen VfA dynamics and in the capacity of the rumen epithelium to absorb and transport VfA. Climate change is a notable barrier to improving livestock sustainability because it may increase the incidence of heat stress (HS) 1. Heat stress costs the U.S. livestock industries $1.7 billion annually 2, and leads to reduced growth rate 3, milk production 4, and reproductive efficiency 5,6 in dairy cattle. Much of the loss in productivity is associated with reduced feed intake 7,8 and increased maintenance energy 9. Another key change that occurs during heat stress is that animals become insulin resistant and fail to mobilize body fat, favoring breakdown of muscle as means to obtain additional energy 10,11. Although these shifts in post-absorptive metabolism have been well characterized in heat stressed cattle, changes in nutrient digestion and absorption have not been evaluated comprehensively. Multiple studies have shown changes in VFA concentrations related to rumen metabolism during heat stress 12-15 , which could be partially driven by a shift in intake. That being said, it is known that concentrations alone are not true representations of metabolism. In particular, absorbed volatile fatty acid (VFA) profiles may be implicated in the post-absorptive shifts in metabolism observed during heat stress because VFA have been shown to influence insulin sensitivity in monogastrics 16,17. It is not unreasonable to think that a similar physiological response may also occur in ruminants. We hypothesize that during exposure to elevated ambient temperature (HS treatment), shifts in ...