Rumen biohydrogenation and milk fatty acid profile in dairy ewes divergent for feed efficiency

Abstract

Rumen biohydrogenation and milk fatty acid profile in dairy ewes divergent for feed efficiency (by Toral et al.) Achieving more sustainable livestock productions requires an enhancement of feed efficiency, but the mechanisms underlying this trait and explaining its large individual variation in dairy animals are still unraveled. Feed efficiency metrics rely on the record of individual feed intake, an expensive or time-intensive task limiting their use in practical farming and forcing the search for other proxies. In this study, two groups of dairy ewes phenotypically divergent for feed efficiency were used to examine the relationship between this trait and the lipid profile of rumen fluid and milk. Results suggest that milk fatty acids might serve as biomarkers of feed efficiency.

Effect of Dietary Supplementation with Lipids of Different Unsaturation Degree on Feed Efficiency and Milk Fatty Acid Profile in Dairy Sheep

“…Nevertheless, from a productive point of view and with the perspective of a direct application in the dairy sector, decreased FCR and ECR would also entail economic advantages for farmers, thus the potentially positive implications of our findings. Furthermore, animal performance data suggest that the lower FCR and ECR in SBO would partly be explained by increased FA yield, which supports a key role of lipid metabolism in underlying feed efficiency mechanisms [ 22 , 54 ]. Further, note that our results did not seem to be explained by mobilization of body reserves, since all treatments showed improved body weight during the trial.…”

“…Although their main effects on milk FA profile have been previously described [ 8 , 9 , 15 ], we report a comprehensive FA composition because available profiles in the literature are often poorly detailed, especially in terms of minor C18, odd-, branched-, and very long-chain FA. Although their biological effects are largely unknown [ 31 , 32 , 33 ], a lack of detail in presentation of results may limit the future advancement of knowledge or the potential application of FA as noninvasive biomarkers [ 22 , 34 , 35 ].…”

“…Residual traits are currently more recommended and used as indicators of feed efficiency in genetic selection [ 19 , 22 , 27 ]; their interest deriving from their potential relationship with basic metabolic processes [ 52 , 53 ]. In Australia, steers from low-RFI selection lines have been shown to consume less feed for the same level of growth performance and, thus, improve the profitability of farms [ 24 ].…”

“…Finally, regarding a validation of previously suggested biomarkers of feed efficiency in dairy ewes (e.g., saturated C4-C14 FA, saturated C4-C14 fatty acids/ cis -9 18:1 ratio or C20–22 n-6 polyunsaturated FA in milk) [ 22 ], no solid conclusions can be drawn. The reason is none other than the divergent effects of experimental diets on the milk concentration of these biomarkers.…”

“…In the last years, an increasing number of researchers in ruminant nutrition have turned their efforts towards prioritizing an improvement in feed efficiency over production level [ 17 , 18 , 19 ]. Although there is still very little information on this topic, particularly in dairy ewes [ 20 , 21 ], a recent study has suggested a relationship between feed efficiency and lipid metabolism in the ovine, with certain milk FA being potential biomarkers of this trait (e.g., saturated C4–C14 FA, saturated C4–C14 fatty acids/ cis -9 18:1 ratio, or C20–22 n-6 polyunsaturated FA) [ 22 ]. Thus, because diet composition has a great influence on the efficiency of feed utilization [ 19 , 23 , 24 ], re-evaluation of the use of lipid supplements aimed at improving milk FA composition is required to examine their effects on metrics and biomarkers of feed efficiency.…”