Conjugated linoleic acids (CLA) and trans-fatty acid profiles of blood plasma and milk fat in dairy cows fed a high-concentrate diet supplemented with linseed, sunflower, or fish oil

A metabolic study was conducted with four ruminally-cannulated lactating goats (Saanen, 29 weeks lactation, 65 ± 5 kg) in a 4 × 4 Latin square design with 4 dietary treatments. The goats we re fed a basal mixed diet cons isting of 80% concentrate and 20% chopped rye grass hay (DM basis, CON). Th e goats were also fed the CON diet supplem ented with soybean oil at a 5% level of the concentrate (SO), the SO diet supplemented with 0.5% of sodi um bicarbonate (SO-B) or the SO -B diet supplemented with 30 p pm monensin (SO-BM). The goats were housed in individual pen and the study was conducted for 8 weeks. An increased molar proportio n of propionate (C 3 ) was observed at 1 h (p<0.003) and 6 h (p<0.029) post-feed ing from all the supplemented diets. Calculated methane emission was markedly decreased prior to morning feeding (p<0.01) , and at 1 h (p<0.05) and 6 h post-feeding (p<0.05) in goats f ed the supplemented diets. All the s upplements increased (p<0.0001) cis 9, trans 11-CLA content in rumen fluid. Concentrations of both c is 9, trans 11-CLA (p<0.0001) and trans 10, cis 12-CLA (p<0.026) were also increased in the m ilk fat of lactating go ats fed the supplemented diets. The SO-B and SO-BM diets further increased CLA content in goat milk compared to the SO diet. All supplements increased unsaturated (UFA, p<0.002), monounsat urated (MUFA, p<0.002) and polyunsaturated fa tty acids (p<0.014) and reduced SFA to UFA ratio (p<0.023). The concentration of MUFA was even greater (p<0 .002) for SO-BM than for the SO-B diet. In conclusion, feeding soybean oil (5% of concentrate) to lactating goats was a useful way to improve milk fat and to improve fatty acid profile in the milk b y increasing potentially healthy fatty acids such as CLA. Supplementation of sodium bicarbonate or sodium bicarbonate with monensin to the soybean oil-based diet increased CLA content further in goat milk. Supplementation of soybean oil may be an effective metho d to reduce methane emission in lactating goats.