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⁻¹ Se as selenized-yeast (SeY) (the SeY diet) or selenate (the selenate diet). Muscles (Musculus longissimus dorsi (MLD) and Musculus 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, CO₂ and CH₄ in the ruminal fluid. The contents of CO₂, CH₄ and VFAs including straight-chain VFAs with the exception of iso-branched-chain VFAs were most effectively reduced by the selenite diet. The control diet most efficiently increased the concentration sums of odd-saturated fatty acids (odd-SFAs) and iso-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 CH₄ and 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) in MLD and MBF than the SeY diet, which most effectively increased the concentrations of ΣSFAs and ΣFAs in MLD and MBF. The selenate diet most effectively increased the body mass gain of lambs.