Oilseed Supplementation Improves Milk Composition and Fatty Acid Profile of Cow Milk: A Meta-Analysis and Meta-Regression

Abstract

Oilseed supplementation is a strategy to improve milk production and milk composition in dairy cows; however, the response to this approach is inconsistent. Thus, the aim of this study was to evaluate the effect of oilseed supplementation on milk production and milk composition in dairy cows via a meta-analysis and meta-regression. A comprehensive and structured search was performed using the following electronic databases: Google Scholar, Primo-UAEH and PubMed. The response variables were: milk yield (MY), atherogenic index (AI), Σ omega-3 PUFA, Σ omega-6 PUFA, fat, protein, lactose, linoleic acid (LA), linolenic acid (LNA), oleic acid (OA), vaccenic acid (VA), conjugated linoleic acid (CLA), unsaturated fatty acid (UFA) and saturated fatty acid (SFA) contents. The explanatory variables were breed, lactation stage (first, second, and third), oilseed type (linseed, soybean, rapeseed, cottonseed, and sunflower), way (whole, extruded, ground, and roasted), dietary inclusion level, difference of the LA, LNA, OA, forage and NDF of supplemented and control rations, washout period and experimental design. A meta-analysis was performed with the “meta” package of the statistical program R. A meta-regression analysis was applied to explore the sources of heretogeneity. The inclusion of oilseeds in dairy cow rations had a positive effect on CLA (+0.27 g 100 g−1 fatty acids (FA); p < 0.0001), VA (+1.03 g 100 g−1 FA; p < 0.0001), OA (+3.44 g 100 g−1 FA; p < 0.0001), LNA (+0.28 g 100 g−1 FA; p < 0.0001) and UFA (+8.32 g 100 g−1 FA; p < 0.0001), and negative effects on AI (−1.01; p < 0.0001), SFA (−6.51; p < 0.0001), fat milk (−0.11%; p < 0.001) and protein milk (−0.04%; p < 0.007). Fat content was affected by animal breed, lactation stage, type and processing of oilseed and dietary NDF and LA contents. CLA, LA, OA and UFA, desirable FA milk components, were affected by type, processing, and the intake of oilseed; additionally, the concentrations of CLA and VA are affected by washout and design. Oilseed supplementation in dairy cow rations has a positive effect on desirable milk components for human consumption. However, animal response to oilseed supplementation depends on explanatory variables related to experimental design, animal characteristics and the type of oilseed.

The Effects of Feeding Milled Rapeseed Seeds with Different Forage:Concentrate Ratios in Jersey Dairy Cows on Milk Production, Milk Fatty Acid Composition, and Milk Antioxidant Capacity

“…In a meta-analysis by Plata-Pérez et al [ 1 ], it was found that supplementing the diet of cows with oilseeds can increase milk production due to the increase in NE L intake. In our study, the increased milk production in cows fed the HR diet compared to the H diet, was consistent with the higher energy density of the HR diet and, respectively, the higher intake of NE L ( Table 3 ).…”

“…In addition, it was found that oilseeds that have a high content of LA (e.g., sunflower seeds, cotton seeds, soybeans) induce a significant decrease in milk fat concentration, because LA has an effect of inhibiting the fermentation processes in the rumen, and it is believed that LA is a substrate in the production of trans isomers, which are related to the milk fat depression syndrome [ 7 , 47 ]. Flax seeds and rapeseed seeds, having a lower content of LA, form a smaller number of isomers that inhibit the de novo synthesis of FAs with short and medium chains in the mammary gland and thus have a smaller influence on the milk fat concentration [ 1 ].…”

“…The inclusion of rapeseed in the diet of cows reduced the content of SFAs in milk, possibly by decreasing the production of acetic acid in the rumen, which is the main substrate for the de novo synthesis of medium-chain FAs [ 1 , 15 ].…”

“…Nowadays, many consumers are aware of the relation between diet and health. A major interest in modifying milk fatty acids (FAs) composition, aiming to enhance the health status of consumers, was noticed in the last two decades [ 1 , 2 , 3 ]. Such changes are intended to decrease the proportion of saturated FAs (SFAs) in milk fat composition, and to increase the proportion of healthy FAs, such omega-3 FAs (n-3 FAs), conjugated linoleic acid (CLA, cis -9, trans -11 C18:2), oleic acid (OA, C18:1 cis -9), and vaccenic acid (VA, C18:1 trans -11) [ 4 ].…”

“…Increasing the concentration of nutritionally beneficial FAs in milk also increases the risk of milk fat oxidation, leading to changes in the nutritional and dietary properties of milk [ 1 ]. To maintain high milk quality, the concentration of antioxidants should therefore be increased [ 23 ], for them to ensure an increased antioxidant capacity of milk [ 2 , 24 ].…”