Grazing cows could produce milk with a higher proportion of polyunsaturated fatty acids, which is beneficial to human health, compared with non-grazing cows, though grazing alone could compromise milk production. Under oceanic climate conditions, a study involving 15 dairy cows, fed total mixed ration (TMR)ad libitumin combination with different grazing times of 12 h (TMR12), 6 h (TMR06) and zero grazing time (TMR00) with the aim to evaluate different strategies on the fatty acids profile of milk and milk production. No differences were seen between the treatments with respect to milk yield (34·4±6·3 kg/d) or milk protein content (30·4±1·8 g/kg). The milk produced by the TMR12 cows had less total fat (36·2 vs. 38·2 g/kg) and saturated fatty acid (FA, 69·39 vs. 71·44 g/100 g FA) than that produced by the TMR00 cows. The concentration of vaccenic acid in the TMR06 and TMR12 milk was twice that of the TMR00 milk (4·22, 4·09 and 2·26 g/100 g FA respectively). Linear increases in conjugated linoleic (CLA) and linolenic acids were observed with increasing grazing time. Pasture was an important source of FA especially C18:3 for TMR06 and TMR12 cows. Under oceanic climatic conditions, the grazing of dairy cows as a complement to feeding with TMR can improve the FA profile of milk and increase its CLA content.

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.

In recent years, consumer attitudes toward fat of animal origin have changed owing to findings that some milk fatty acids (FAs) are positive for human health, especially conjugated linolenic acid andn-3 FAs. Accordingly, the manipulation of the fat content and FA composition of cows’ milk via nutritional strategies has been an important target for the dairy industry in many countries. Twenty commercial Holstein–Friesian dairy herds of Asturias (northern Spain) with 1106 dairy cows were examined in order to evaluate milk FA profiles under different management systems. These herds were divided into three groups according to management: (1) indoor herds: cows feeding indoors, (2) mixed herds: indoor management system but with at least 6 h of grazing outdoors and (3) outdoor herds: cows allowed 6–18 h of grazing per day. Milk from the indoor herds exhibited the highest concentration of fat (3.57%;P⩽0.01), protein (3.14%;P⩽0.001), lactose (4.76%;P⩽0.01) and urea (29.4 mg dl⁻¹;P⩽0.01). The milk of outdoor herds had a lower (P⩽0.05) content of short-chain FAs than that of the indoor and mixed herds (10.89 versus 11.52 and 11.35 g 100 g⁻¹FA). The milk of the indoor herds had higher concentrations of saturated fatty acids (SFA) (67.56 g 100 g⁻¹FA;P⩽0.001) and palmitic and palmitoleic acids (30.16 and 1.82 g 100 g⁻¹FA, respectively), while that of the mixed and outdoors herds had higher concentrations of unsaturated fatty acids (UFA) (34.58 g 100 g⁻¹FA;P⩽0.001) and long-chain FAs, especially stearic (13.89 g 100 g⁻¹FA;P⩽0.01), vaccenic (2.77 g 100 g⁻¹FA;P⩽0.001), conjugated linoleic (0.92 g 100 g⁻¹FA;P⩽0.001) and linolenic (0.42 g 100 g⁻¹FA;P⩽0.001) acids. Results from this study suggest that the incorporation of forage and pasture in the diet of dairy cows can improve the FA profile of milk.

This study examined the characteristics of the fatty acids profile in the meat of lambs fed grazing and supplemented with different PUFA sources. Thirty Suffolk lambs were used (37.2±5.4kg BW), grazing on perennial ryegrass (Lolium perenne) (12h d^-1) and supplemented (30g kg^-1 BW^0.75) with ryegrass hay (RGH), or supplements formulated with fishmeal (FHM) or soybean meal (SBM). Lambs were used in a completely randomized design. Results showed an effect on total SFA, with SBM higher than RGH (P=0.033), and SBM and FHM showing higher MUFA content compared with RGH (P=0.001). Total PUFA content was higher for RGH, followed by FHM and with the lowest content for SBM (P=0.001). Concluding that there is a variation in fatty acid content depending on the lipid-protein source used in supplementation in grazing sheep, the content of PUFA was higher for grazing lambs supplemented with RGH compared with those supplemented with FHM or SBM.

In vitro activity of Pithecellobium dulce and Lysiloma acapulcensis on exogenous development stages of sheep gastrointestinal strongyles