P. Gómez-Cortés

Effects of extruded linseed supplementation on n-3 fatty acids and conjugated linoleic acid in milk and cheese from ewes

The objective of this study was to assess the effects of dietary supplementation of extruded linseed on animal performance and fatty acid (FA) profile of ewe milk for the production of n-3 FA- and conjugated linoleic acid-enriched cheeses. A Manchega ewe flock (300 animals) receiving a 60:40 forage:concentrate diet was divided into 3 groups supplemented with 0, 6, and 12 g of extruded linseed/100 g of dry matter for the control, low, and high extruded linseed diets, respectively. Bulk and individual milk samples from 5 dairy ewes per group were monitored at 7, 14, 28, 45, and 60 d following supplementation. Manchego cheeses were made with bulk milk from the 3 treatment groups. Milk yield increased in dairy ewes receiving extruded linseed. Milk protein, fat, and total solids contents were not affected by linseed supplementation. Milk contents of alpha-linolenic acid increased from 0.36 with the control diet to 1.91% total FA with the high extruded linseed diet. Similarly, cis-9 trans-11 C18:2 rose from 0.73 to 2.33% and its precursor in the mammary gland, trans-11 C18:1, increased from 1.55 to 5.76% of total FA. This pattern occurred with no significant modification of the levels of trans-10 C18:1 and trans-10 cis-12 C18:2 FA. Furthermore, the high extruded linseed diet reduced C12:0 (-30%), C14:0 (-15%) and C16:0 (-28%), thus significantly diminishing the atherogenicity index of milk. The response to linseed supplementation was persistently maintained during the entire study. Acceptability attributes of n-3-enriched versus control cheeses ripened for 3 mo were not affected. Therefore, extruded linseed supplementation seems a plausible strategy to improve animal performance and nutritional quality of dairy lipids in milk and cheese from ewes.

Milk Production, Conjugated Linoleic Acid Content, and In Vitro Ruminal Fermentation in Response to High Levels of Soybean Oil in Dairy Ewe Diet

Feeding vegetable oils rich in linoleic acid has been demonstrated to be an effective strategy to enrich milk with conjugated linoleic acid (CLA). However, high amounts of vegetable oil in the diet in free form could adversely affect animal performance, mainly in sheep. The aim of this work was to improve the ewe milk fatty acid profile by increasing potentially healthy acids such as CLA without any detrimental effects on milk production and ruminal fermentation with soybean oil (SBO) diet supplementation. Twenty-four ewes were assigned to 2 treatments and fed 2 diets (control or supplemented with 6% of SBO; 2 lots of 6 animals per treatment) and fed ad libitum for 4 wk. The forage:concentrate ratio was 20:80. Batch cultures of rumen microorganisms were used to study in vitro rumen fermentation. Changes in fatty acid profile were characterized as a reduction in C6:0 to C16:0 at the expense of an increase in C18:0, C18:1 isomers, and CLA concentrations. Proportions of milk CLA and trans-11 C18:1 (vaccenic acid) went from 1.04 to 3.44 and 2.08 to 6.20 g/100 g of total fatty acids, respectively. However, the SBO diet also increased trans-10 C18:1 and other trans C18:1 content. No significant decreases were found in the treatments for dry matter intake and milk production. The notable increases in trans-10, cis-12 and trans-9, cis-11 were not accompanied by fat level decreases in ewe milk. Concerning in vitro ruminal fermentation, no significant differences were found in the extent and rate of gas production, effective degradability, in vitro true digestibility, and volatile fatty acid production. The results demonstrate that dairy sheep milk CLA content can be substantially increased (more than 3-fold) by adding high levels of SBO in the diet as free oil, without any negative effects on animal performance.

Changes in milk fatty acid profile and animal performance in response to fish oil supplementation, alone or in combination with sunflower oil, in dairy ewes

Ruminant diet supplementation with sunflower oil (SO) and fish oil (FO) has been reported as a good strategy for enhancing some milk fat compounds such as conjugated linoleic acid (CLA) and n-3 polyunsaturated fatty acids in dairy cows, but no information is available regarding dairy sheep. In this work, ewe diet was supplemented with FO, alone or in combination with SO, with the aim of improving milk nutritional value and evaluating its effect on animal performance. Sixty-four Assaf ewes in mid lactation, fed a high-concentrate diet, were distributed in 8 lots of 8 animals each and assigned to 4 treatments (2 lots/treatment): no lipid supplementation (control) or supplementation with 20 g of SO/kg (SO), 10 g of FO/kg (FO), or 20 g of SO plus 10 g of FO/kg (SOFO). Milk production and composition, including a complete fatty acid profile, were analyzed on d 0, 3, 7, 14, 21, and 28 of treatments. Supplementation with FO tended to reduce dry matter intake compared with the control treatment (-15%), and its use in combination with SO (SOFO) resulted in a significant decrease in milk yield as well (-13%). All lipid supplements reduced milk protein content, and FO also reduced milk fat content by up to 21% alone (FO) and 27% in combination with SO (SOFO). Although the mechanisms involved in FO-induced milk fat depression are not yet well established, the observed increase in some milk trans-FA that are putative inhibitors of milk fat synthesis, such as trans-9,cis-11 CLA, and the 63% decrease in C18:0 (consistent with the theory of reduced milk fat fluidity) may be involved. When compared with the control, lipid supplementation remarkably improved the milk content of rumenic acid (cis-9,trans-11 CLA; up to 4-fold increases with SO and SOFO diets), whereas FO-containing diets also increased milk n-3 polyunsaturated fatty acids, mainly docosahexaenoic acid (with mean contents of 0.29 and 0.38% of total fatty acids for SOFO and FO, respectively), and reduced the n-6:n-3 FA ratio to approximately half the control value. All lipid supplements resulted in high levels of some trans-FA, mainly trans-11 C18:1 (vaccenic acid) but also trans-10 C18:1.

Milk fatty acid profile and dairy sheep performance in response to diet supplementation with sunflower oil plus incremental levels of marine algae

In an attempt to develop strategies for enhancing the nutritional value of sheep milk fat, dairy ewe diet was supplemented with 3 incremental levels of marine algae (MA), in combination with sunflower oil, to evaluate the effects of these marine lipids on milk fatty acid (FA) profile and animal performance. Fifty Assaf ewes in mid lactation were distributed in 10 lots of 5 animals each and allocated to 5 treatments (2 lots per treatment): no lipid supplementation (control) or supplementation with 25 g of sunflower oil/kg of DM plus 0 (SO), 8 (SOMA(1)), 16 (SOMA(2)), or 24 (SOMA(3)) g of MA (56.7% ether extract)/kg of DM. Milk production and composition, including FA profile, were analyzed on d 0, 3, 7, 14, 21, and 28 of treatment. Neither intake nor milk yield were significantly affected by lipid addition, but all MA supplements decreased milk fat content from d 14 onward, reaching a 30% reduction after 28 d on SOMA(3). This milk fat depression might be related not only to the joint action of some putative fat synthesis inhibitors, such as trans-9,cis-11 C18:2 and probably trans-10 C18:1, but also to the limited ability of the mammary gland to maintain a desirable milk fat fluidity, that would have been caused by the noticeable increase in trans-C18:1 together with the lowered availability of stearic acid for oleic acid synthesis through Delta(9)-desaturase. Furthermore, all lipid supplements, and mainly MA, reduced the secretion of de novo FA (C6:0-C14:0) without increasing the yield of preformed FA (>C16). Supplementation with sunflower oil plus MA resulted in larger increases in cis-9,trans-11 C18:2 than those observed with sunflower oil alone, achieving a mean content as high as 3.22% of total FA and representing a more than 7-fold increase compared with the control. Vaccenic acid (trans-11 C18:1) was also significantly enhanced (on average +794% in SOMA treatments), as was C22:6 n-3 (DHA) content, although the transfer efficiency of the latter, from the diets to the milk, was very low (5%). However, the highest levels of MA inclusion (SOMA(2) and SOMA(3)) reduced the milk n-6:n-3 ratio, but MA supplements caused an important increase in trans-10 C18:1, which would rule out the possibility that this milk has a healthier fat profile before determining the specific role of each individual FA and ensuring that this trans-FA is at least innocuous in relation to cardiovascular disease risk.

Addition of olive oil to dairy ewe diets: effect on milk fatty acid profile and animal performance

The effects of ruminant diet supplementation with linoleic or different polyunsaturated fatty acids (FA) have been well documented. Less abundant information, however, exists on the effects of incorporating monounsaturated FA, such as oleic acid, on lipid metabolism or animal performance. The purpose of this work was to assess the effects of feeding dairy ewes a diet supplemented with high levels of olive oil (OO) on milk yield and composition, paying particular attention to the FA profile. Twenty-four Assaf ewes were fed ad libitum with 2 diets, control or supplemented with 6% OO (2 lots of 6 animals per diet) for 4 wk. Milk yield and composition and dry matter intake were recorded weekly. Milk FA composition was determined by gas chromatography and conjugated linoleic acid profile by silver ion HPLC. Milk yield increased in ewes receiving OO, with no differences in dry matter intake. The OO diet decreased the milk protein percentage but increased the milk fat, protein, and total solids yield. Medium-chain saturated FA (C10:0 to C16:0) content was reduced with OO supplementation, whereas C18:0 and cis-9 C18:1 content increased. Leaving aside trans-11, most trans C18:1 isomers, mainly trans-10, increased in supplemented ewes. The main conjugated linoleic acid isomer (cis-9, trans-11 C18:2) decreased with OO supplementation, whereas trans-7, cis-9 and trans-9, cis-11 C18:2 exhibited a remarkable increase. These results support the argument that the supplementation of ewe diets with high levels of OO does not have any detrimental effects on animal performance but substantially modifies the FA profile.

Animal performance and milk fatty acid profile of dairy goats fed diets with different unsaturated plant oils

The effect of supplementing a basal diet with 1 of 3 plant oils on productive efficiency and milk fatty acid composition was studied in dairy goats. Sixteen Malagueña goats were used in a 4×4 Latin square experiment with 21-d periods and 4 goats per treatment. The basal diet comprised 30% alfalfa hay and 70% pelleted concentrate. Experimental treatments were control (basal diet without added oil) and the basal diet supplemented with 48g/d of high oleic sunflower oil (HOSFO), regular sunflower oil (RSFO), or linseed oil (LO). Dry matter intake and body weight were not affected by treatments. Milk production was higher in HOSFO treatment and milk fat content was higher in RSFO and LO treatments, although no differences in milk energy production or milk renneting properties were found. The RSFO and LO treatments increased the proportion of vaccenic acid in milk fat more so than the HOSFO diet, and rumenic acid followed the same pattern. The content of trans10-18:1 remained low in all experimental diets (<0.7% of total fatty acid methyl esters) although HOSFO and RSFO diets increased it. The variations in the fatty acid profiles observed with the 4 diets, mainly the unsaturated fatty acid isomer contents, are extensively discussed. Compared with that in the control diet, the n-6:n-3 fatty acid ratio in milk fat substantially decreased with the LO, increased with RSFO, and did not change with HOSFO. The addition of moderate amounts of LO to the diets of dairy goats has favorable effects on milk fatty acid composition from the point of view of the human consumer, without negative effects on animal performance.

Effects of feeding increasing dietary levels of high oleic or regular sunflower or linseed oil on fatty acid profile of goat milk

In this work, the effects of increasing amounts of 3 plant oils in diets on the fatty acid (FA) profile of goat milk were studied. The study consisted of 3 experiments, one per oil tested (linseed oil, LO; high oleic sunflower oil, HOSFO; and regular sunflower oil, RSFO). The 3 experiments were conducted successively on 12 Malagueña goats, which were assigned at random to 1 of 4 treatments: 0, 30, 48, and 66 (H) g of added oil/d. A basal diet made of alfalfa hay and pelleted concentrate (33:67) was used in all of the experiments. For each animal, milk samples collected after 15 d on treatments were analyzed for fat, protein, lactose, and FA composition, whereas individual milk yield was measured the last 3 d of each experiment. Oil supplementation affected neither dry matter intake nor milk production traits. Increasing the oil supplementation decreased the content of saturated FA (especially 16:0) in milk fat and increased mono- and polyunsaturated FA in a linear manner. Vaccenic acid content linearly increased with the oil supplementation by 370, 217, and 634% to 5.32, 2.66, and 5.09 g/100 g of total FA methyl esters with the H diet in LO, HOSFO, and RSFO experiments, respectively. Rumenic acid content linearly increased with LO and RSFO supplementation by 298 and 354% from 0.53 and 0.41 g/100 g of total FA methyl esters with the 0 g of added oil/d diet. The content of trans-10-18:1 was not affected by LO supplementation but showed an increasing linear trend with HOSFO supplementation and linearly increased with RSFO supplementation. The ratio of n-6 to n-3 polyunsaturated FA in milk fat was decreased by about 70% with the H diet in the LO experiment and it was increased by 54 and 82% with the H diet in the HOSFO and RSFO experiments. In conclusion, LO supplementation in this work seemed to be the most favorable alternative compared with HOSFO or RSFO supplementation.

Effect of supplementation of grazing dairy ewes with a cereal concentrate on animal performance and milk fatty acid profile.

This work was conducted to investigate the effect of supplementing grazing ewes on pasture with a cereal concentrate on the milk fatty acid (FA) profile. Ninety Assaf ewes in mid lactation were distributed in 9 lots of 10 animals each and allocated to 3 feeding regimens: 1) pasture--ewes were only allowed to graze pasture (an irrigated sward of Lolium perenne, Trifolium pratense, and Dactylis glomerata); 2) PS--grazing ewes were supplemented with oat grain (700 g/animal and day); and 3) TMR--ewes were fed ad libitum a total mixed ration (TMR; 80:20 concentrate/forage ratio). Milk yield and composition were recorded for 5 wk. The highest milk yield was observed in ewes receiving the TMR and the lowest in grazing ewes supplemented with oat grain. Productions of milk fat, protein, and total solids showed the lowest values in treatment PS. The atherogenicity index, which comprises C12:0, C14:0, and C16:0, in PS milk fat was no different from that observed in milk from animals on pasture (1.53 for pasture, 1.54 for PS, and 3.22 for TMR). Oat grain supplementation generated higher amounts of C18:0 and cis-9 C18:1 in milk fat than the pasture-only diet, but significantly decreased the levels of alpha-linolenic acid and most of intermediates of the process of biohydrogenation of this FA. Cis-9 trans-11 C18:2 and trans-11 C18:1, its precursor for endogenous synthesis in the mammary gland, were lower in PS (0.58 and 1.59 g/100 g of total FA) than in TMR (0.72 and 1.92 g/100 g of total FA) and very different from the results observed in grazing ewes receiving no supplement (1.21 and 3.88 g/100 g of total FA). Furthermore, the lowest levels of trans-10 C18:1 and trans-10 cis-12 C18:2 were detected in the milk fat of ewes fed pasture. It is concluded that, when pasture quality and availability do not limit dairy production, supplementation of grazing ewes with oat grain compromised the milk FA profile without any significant positive effect on milk production.

Inhibition of ∆9-desaturase activity with sterculic acid: Effect on the endogenous synthesis of cis-9 18:1 and cis-9 trans-11 18:2 in dairy sheep

This study was conducted in lactating ewes to examine the involvement of ∆(9)-desaturase in mammary lipogenesis, especially in the endogenous synthesis of cis-9, trans-11 18:2 and cis-9 18:1, because no information on this matter was available for dairy sheep. With this aim, 6 Assaf ewes were monitored in a 15-d experiment, which included a 5-d pretreatment period, a 5-d treatment period, and a 5-d posttreatment period. During the treatment period, ewes received 0.5 g/d of sterculic acid (a cyclopropene fatty acid that inhibits ∆(9)-desaturase), delivered intravenously in 4 equal doses at 6-h intervals. Animals were fed pasture to supply mainly α-linolenic acid and minimize the amount of milk cis-9, trans-11 18:2 of ruminal origin. Sterculic acid administration was calculated to inhibit ∆(9)-desaturase by 70% based on the milk content of cis-9 14:1. This inhibition resulted in decreases in the milk content of the enzyme products (e.g., cis-9 10:1, cis-9 14:1, cis-9 16:1, cis-9 18:1, and cis-9, trans-11 18:2) and increases in its substrates (e.g., 14:0, 18:0, and trans-11 18:1), as well as in reductions in the desaturase indexes. Some other milk fatty acids, further to previously reported products or substrates of ∆(9)-desaturase (e.g., cis-15 18:1 and cis-9, cis-15 18:2, or trans-11, trans-15 18:2, and cis-9, trans-11, trans-15 18:3), were also affected by sterculic acid administration. Endogenous synthesis was the major source of cis-9 18:1 and cis-9, trans-11 18:2, accounting for 63 and 74% of its content in milk fat, respectively. To our knowledge, the present study provides the first estimates of endogenous synthesis of these 2 bioactive fatty acids in ovine milk fat.

Effects of different forage: concentrate ratios in dairy ewe diets supplemented with sunflower oil on animal performance and milk fatty acid profile

The aim of this study was to evaluate the effect of different forage:concentrate (FC) ratios in dairy ewe diets supplemented with sunflower oil (SO) on animal performance and milk fatty acid (FA) profile, particularly focusing on trans C18:1 FA and conjugated linoleic acid (CLA). Sixty lactating Assaf ewes were randomly assigned to 6 treatments in a 3 × 2 factorial arrangement: 3 FC ratios (30:70, 50:50, and 70:30) and 2 levels of SO addition (0 and 20 g/kg of dry matter). Both the diet FC ratio and SO supplementation affected milk yield, but differences between treatments were small. Although the proportion of concentrate induced limited changes in milk FA profile, dietary SO significantly decreased saturated FA and enhanced total CLA. Furthermore, the incorporation of SO in ewe diets decreased the atherogenicity index value by about 25% and doubled the contents of potentially healthy FA such as trans-11 C18:1 and cis-9,trans-11 CLA. However, the inclusion of SO in a high-concentrate diet (30:70) could switch linoleic acid biohydrogenation pathways, resulting in a significant increase in trans-10 C18:1, trans-9,cis-11 C18:2, and trans-10,cis-12 C18:2 milk fat percentages.