Apparent recovery of C18 polyunsaturated fatty acids from feed in cow milk: A meta-analysis of the importance of dietary fatty acids and feeding regimens in diets without fat supplementation

摘要: A meta-analysis was conducted using the results of 82 experiments (78 publications, 266 treatments) to investigate importance dietary C18 fatty acids (FA) and feeding regimen for milk FA profile apparent recovery selected relative intake these or their precursors. Feeding treatments based on lipid-supplemented diets were excluded. regimens defined as grazing [including partial full-time grazing, at concentrate proportions from 0 44% dry matter (DM)], forage-based indoor [>65% forage total DM (DMI)], concentrate-based (forage DMI ≤65% DMI). Linoleic acid (LLA), α-linolenic (ALA), in fat increased linearly with respective content all tested. This effect highest feeding. Slopes lowest regimens, especially regarding ALA sum FA, whereas intercepts prediction equations regimens. indicates that, cows, factors other than contents determine composition fat. At equal LLA contents, type showed no significant proportion Milk rumenic vaccenic positively related contents. Grazing led strongest enrichment The ALA, LLA, (secreted, % intake), an estimate transfer efficiency, decreased increasing content. relationship followed a nonlinear decay function. When exceeded certain threshold (about 0.2, 0.8, 2.8% respectively) remained constant about 5, 10, 82% ingested respectively. below 0.01% 1.5% DM, 100%. In conclusion, general inverse between corresponding seems exist. Within this frame, different types eventual varies. Among them, pasture appears provide most variable properties.