Abstract
The objective of this study was to evaluate the effects of dietary supplementation with live yeast (Saccharomyces cerevisiae), mannan-oligosaccharides and the combination of these additives on the inflammatory response, ruminal parameters and rumen morphology of sheep fed a high grain-based diet. Thirty-Two Dorper x Santa Ines crossbred lambs with an average weight of 24±2 kg were distributed in a completely randomized design. The animals were housed in individual stalls and fed ad libitum. Diet treatments were: Control (without additive); LY (2 g/kg DM of live yeast, Saccharomyces cerevisiae), MOS (2 g/kg DM of mannan-oligosaccharides) and LY+MOS (2 g/kg DM of LY + 2 g/kg DM of MOS). The experiment lasted 42 days. The supplementation with MOS alone and the additives combination resulted in increased ruminal pH (P<0.01), while the total concentrations of short chain fatty acids (SCFA) in the rumen were higher (P<0.05) only in the diets with LY and MOS. Ammonia (NH3) concentration in the rumen decreased (P<0.04) with the additives usage. Diets with LY, MOS and with additives combination reduced (P<0.01) the levels of lipopolysaccharides (LPS) in the plasma with values of 0.46; 0.44 and 0.04 EU/mL, respectively when compared to the control (0.93 EU/mL). MOS and LY+MOS treatments had reduced stratum corneum thickness (P<0.01) in comparison to the control treatment. The total thickness of ruminal epithelium was lower with the addition of MOS in the diet (P<0.03) than with LY additive. The incidence and severity of hepatic abscesses in animals whose diet was supplemented with LY and LY+MOS was lower (P<0.05) than in animals fed the control diet. The use of LY, MOS and LY+MOS in the high-concentrate diets for sheep reduced NH3 concentrations and LPS translocation into the bloodstream. Diets containing MOS and LY+MOS enhanced the health of the ruminal epithelium by reducing the thickness of the stratum corneum, and diets containing LY and LY+MOS decreased the incidence and severity of hepatic abscesses.
Highlights
The use of high-concentrate diets, mainly grains, is an increasingly common practice in ruminant feeding to improve milk production and body weight
The pH increased with the addition of Live yeast (LY)+MOS into the diet, this result does not indicate that there was a stabilizing effect on ruminal pH, because the highest ruminal pH (5.50) was below 5.8, the level considered to be indicative of ruminal acidosis [3]
The stratum corneum thickness observed with the MOS and LY+MOS diets can be considered normal for forage-based diets (17.3 μm), according to Steele et al [35]. These results suggest that MOS and LY+MOS have a protective effect on the ruminal epithelium against the damage caused by severe ruminal acidosis that occurs when feeding grain-based diets
Summary
The use of high-concentrate diets, mainly grains, is an increasingly common practice in ruminant feeding to improve milk production and body weight This type of diet contains carbohydrates that are rapidly fermentable in the rumen and increases the risk of metabolic disorders such as ruminal acidosis, foot problems and hepatic abscesses [1, 2]. Ruminal acidity leads to the death of gram-negative bacteria with the corresponding release of endotoxins (lipopolysaccharides, LPS), activating a cascade of inflammatory mediators, and affecting the animal productive performance [5, 6] For this reason, the economic and health consequences of subacute ruminal acidosis can be considered one of the most important problems in animal feedlot systems. The possible effects of these additives on the digestive tract microbiota, ruminal pH regulation, and immunostimulation are beneficial to digestibility, performance, and health of animals [9, 10]
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