The Influence of Different Chemical Forms of Selenium Added to the Diet Including Carnosic Acid, Fish Oil and Rapeseed Oil on the Formation of Volatile Fatty Acids and Methane in the Rumen, and Fatty Acid Profiles in the Rumen Content and Muscles of Lambs

Lambs were divided into 3 groups of 6 animals each. For 35 days lambs were fed a diet including 2% rapeseed oil, 1% fish oil and 0.1% carnosic acid (the control group) or two experimental diets supplemented with 0.35 mg ∙ kg−1Se as selenized-yeast (SeY) (the SeY diet) or selenate (the selenate diet). Muscles (Musculus longissimus dorsi(MLD) andMusculus biceps femoris(MBF)), ruminal fluids and microbiota were collected from each lamb. SeY supplementation most effectively stimulated the accumulation of straight-chain volatile fatty acids (VFAs),iso-branched-chain VFAs, CO2and CH4in the ruminal fluid. The contents of CO2, CH4and VFAs including straight-chain VFAs with the exception ofiso-branched-chain VFAs were most effectively reduced by the selenite diet. The control diet most efficiently increased the concentration sums ofodd-saturated fatty acids (odd-SFAs) andiso-SFAs in microbiota. The SeY diet most efficiently reduced acetic acid to propionic acid ratio in the ruminal fluid. The selenate diet improved animal performance by reducing ruminal concentrations of CH4and CO2. The SeY diet and especially the selenate diet reduced the biohydrogenation to C18:0 when compared with the control diet. The selenate diet more efficiently reduced the concentration sums of all SFAs (ΣSFAs) and all fatty acids (ΣFAs) inMLDandMBFthan the SeY diet, which most effectively increased the concentrations of ΣSFAs and ΣFAs inMLDandMBF. The selenate diet most effectively increased the body mass gain of lambs.