Heat Stress Increases In Vitro Hindgut Fermentation of Distinct Substrates in Iberian Pigs

Abstract

Heat stress reduces the feed intake and growth of pigs. We hypothesized that heat stress affects the intestinal fermentation capacity of pigs. Sixteen Iberian pigs (44 ± 1.0 kg) were randomly assigned to one of two treatments (eight pigs/treatment) for 4 weeks—heat stress (HS; 30 °C) ad libitum or thermoneutral (TN; 20 °C) pair feeding. Frozen rectum contents were used as inocula for 24 h in vitro incubations in which a mixture of starches, citrus pectin, inulin from chicory, and cellulose were the substrates. Cellulose was poorly degraded, whereas pectin and the mixture of starches were the most fermentable substrates according to total short-chain fatty acid (SCFA) production. The mixture of starches and inulin produced the greatest amount of gas. For all substrates, heat stress enhanced gas production (8%, p = 0.001), total SCFA production (16%, p = 0.001), and the production of acetate and propionate (12% and 42%, respectively; p = 0.001). The increased isoacid production (33%, p = 0.001) and ammonia concentration (12%, p = 0.001) may indicate protein fermentation under heat stress. In conclusion, the in vitro intestinal fermentation capacity of pigs under heat stress was increased compared to thermoneutral conditions, which may indicate an adaptive response to heat stress.

The Effect of Supplementation with Betaine and Zinc on In Vitro Large Intestinal Fermentation in Iberian Pigs under Heat Stress

“…Therefore, the extent of fermentation seems to depend on both the prevalence of environmental conditions and the fermentability of the individual carbohydrates. Hence, the use of pure substrates with different characteristics allowed us to have a variety of fermentation profiles [ 11 , 33 , 34 ]. Indeed, it has been reported that the fermentation of dietary fiber by pig intestinal microbes mainly depends on its amount and solubility [ 35 ].…”

“…Indeed, it has been reported that the fermentation of dietary fiber by pig intestinal microbes mainly depends on its amount and solubility [ 35 ]. Previous works have demonstrated that pig feces can be used as inoculum for in vitro fermentation techniques, replacing the intestinal content [ 11 , 36 , 37 ] and permitting a valid study of the microbial activity present in the large intestine [ 38 , 39 ]. We used a 24 h incubation time to simulate the transit time of pigs fed diets based on cereals [ 40 ].…”

“…Microbiota present in the intestine carry out the fermentation of dietary fiber, generating gases and short chain fatty acids (SCFA) [ 10 ]. Indeed, we have shown increased in vitro intestinal fermentation in Iberian pigs after HS [ 11 ]. Unsurprisingly, zinc [ 12 , 13 ] and betaine [ 14 , 15 ] have been used as nutritional mitigation strategies to alleviate HS in pigs.…”