Composition of rumen-surrounding fat and fatty acid profile in selected tissues of lambs fed diets supplemented with fish and rapeseed oils, carnosic acid, and different chemical forms of selenium

Abstract

The main aim of our study was to investigate the impact of carnosic acid (CA), selenized yeast (SeY) and selenate (SeVI) added to the diet including rapeseed oil (RO) and fish oil (FO) on contents of volatile fatty acids (VFA), fatty acids (FA), CH4 and CO2 in the rumen and levels of FA, tocopherols, total cholesterol (TCl) and malondialdehyde (MDA; a marker of oxidative stress) in the rumen-surrounding fat (RSF) of lambs. The second objective of our study was to investigate the effects of CA and Se (as SeY or SeVI) added to the diets including RO and FO on concentrations of FA in the liver, heart, musculus longissimus dorsi (MLD) and musculus biceps femoris (MBF) of lambs. After the preliminary period, the 35-day experiment was conducted, during which animals were fed the basal diet (BD) with 20 g RO/kg BD and 10 g FO/kg BD (the control diet) or experimental diets supplemented with 20 g RO/kg BD, 10 g FO/kg BD and 1 g CA/kg BD without/with 0.35 mg Se/kg BD (Se as SeY or SeVI). The experimental diet with CA and SeY increased ruminal contents of acetic acid (AA), propionic acid (PA), butyric acid (BA), valeric acid (VA), iso-butyric acid (isoBA), iso-valeric acid (isoVA), CH4 and CO2 compared to the control and other experimental diets. The experimental diet with CA and SeVI decreased the ruminal contents of BA, VA, isoBA, the content sums of VFA and straight-chain VFA, CH4 and CO2 compared to the control diet and the experimental diet with CA and SeY. All experimental diets affected the concentration of FA in the RSF, ruminal fluids, the liver, heart, MLD and MBF. Content sums of long-chain polyunsaturated FA (LPUFA), n-3LPUFA and ratios of LPUFA/FA, n-3LPUFA/FA and Σn-3LPUFA/n-6PUFA in the RSF of lambs fed all of the experimental diets was lower than that of the control diet. SeY and CA added to the diet reduced the content of MDA in the RSF compared to the control and other experimental diets. The diet with CA and SeVI decreased the level of MDA in the RSF when compared to the control diet and the diet with CA. Compared to SeY added to the diet with CA, the diet containing CA and SeVI more efficiently improved animal performance by reducing lamb emissions of CH4 and CO2 (the greenhouse gases); this is valuable information for nutritionists carrying out research on farm ruminants to improve the nutritive value of food from the aspect of human health.