Examination of the Persistency of Milk Fatty Acid Composition Responses to Fish Oil and Sunflower Oil in the Diet of Dairy Cows

Abstract

Based on the potential benefits of cis-9, trans-11 conjugated linoleic acid (CLA) for human health, there is a need to develop effective strategies for enhancing milk fat CLA concentrations. Levels of cis-9, trans-11 CLA in milk can be increased by supplements of fish oil (FO) and sunflower oil (SO), but there is considerable variation in the response. Part of this variance may reflect time-dependent ruminal adaptations to high levels of lipid in the diet, which lead to alterations in the formation of specific biohydrogenation intermediates. To test this hypothesis, 16 late lactation Holstein-British Friesian cows were used in a repeated measures randomized block design to examine milk fatty acid composition responses to FO and SO in the diet over a 28-d period. Cows were allocated at random to corn silage-based rations (8 per treatment) containing 0 (control) or 45 g of oil supplement/kg of dry matter consisting (1:2; wt/wt) of FO and SO (FSO), and milk composition was determined on alternate days from d 1. Compared with the control, the FSO diet decreased mean dry matter intake (21.1 vs. 17.9 kg/d), milk fat (47.7 vs. 32.6 g/kg), and protein content (36.1 vs. 33.3 g/kg), but had no effect on milk yield (27.1 vs. 26.4 kg/d). Reductions in milk fat content relative to the FSO diet were associated with increases in milk trans-10 18:1, trans-10, cis-12 CLA, and trans-9, cis-11 CLA concentrations (r(2) = 0.74, 0.57, and 0.80, respectively). Compared with the control, the FSO diet reduced milk 4:0 to 18:0 and cis 18:1 content and increased trans 18:1, trans 18:2, cis-9, trans-11 CLA, 20:5 n-3, and 22:6 n-3 concentrations. The FSO diet caused a rapid elevation in milk cis-9, trans-11 CLA content, reaching a maximum of 5.37 g/100 g of fatty acids on d 5, but these increases were transient, declining to 2.35 g/100 g of fatty acids by d 15. They remained relatively constant thereafter. Even though concentrations of trans-11 18:1 followed the same pattern of temporal changes as cis-9, trans-11 CLA, the total trans 18:1 content of FSO milk was unchanged because of the concomitant increases in the concentration of other isomers (Delta(4-10) and Delta(12-15)), predominantely trans-10 18:1. In conclusion, supplementing diets with FSO enhances milk fat cis-9, trans-11 CLA content, but the high level of enrichment declines because of changes in ruminal biohydrogenation that result in trans-10 replacing trans-11 as the major 18:1 biohydrogenation intermediate formed in the rumen.

Recent advances in the regulation of milk fat synthesis

“…This has been most clearly demonstrated with abomasal infusion of trans-10, cis-12 CLA in dairy cows where milk fat percent progressively decreased with a significant reduction by 10 h (Harvatine and Bauman, 2007b) and a nadir was achieved by 3 to 4 days (Baumgard et al, 2000). Diet-induced MFD develops over a longer interval ( , 7 to 18 days) consistent with the adaptations in ruminal fermentation that are required to produce altered biohydrogenation products (Shingfield et al, 2006b); however, MFD was induced more rapidly when cows switched to a low-forage diet and also had ruminal contents exchanged with a cow already adapted to the diet (Satter and Bringe, 1969). Third, the maximal reduction in milk fat yield observed with trans-10, cis-12 CLA and diet-induced MFD is , 50% ).…”

Role of trans fatty acids in the nutritional regulation of mammary lipogenesis in ruminants

“…A number of studies have attempted to identify additional biohydrogenation intermediates involved in the regulation of milk fat synthesis based on the evaluation of changes in specific fatty acids in milk and changes in milk fat secretion. Over a range of diets causing MFD a close inverse relationship has been identified between milk trans-9, cis-11 CLA concentrations and milk fat secretion Shingfield et al, 2006a). In all cases, enrichment of trans-9, cis-11 CLA in milk fat has been shown to be highly correlated with increases in trans-10 18:1 concentrations.…”

“…Ruminal biohydrogenation pathways appear to be more stable and robust to alterations due to diet in small ruminants compared with the cow that may reflect differences between species related to eating behavior, rumination, buffering of rumen pH, rumen digestion kinetics and transit rates (Chilliard et al, 2003;Pulina et al, 2006;Bernard et al, 2009c) resulting in less exposure of the mammary gland to TFA that may inhibit milk fat synthesis. This is supported by a recent experiment demonstrating that supplements of fish oil and soya bean oil (30 and 109 g/day) to goats grazing fresh grass enhanced milk fat content (mean response 8 g/kg) and milk trans-11 18:1 concentrations (mean response 11.9 g/100 g fatty acids) in the absence of large changes (mean response 0.9 g/100 g fatty acids) in milk trans-10 18:1 content (Gagliostro et al, 2009), whereas fish oil and sunflower oil causes MFD in lactating cows fed maize silage based diets and increases in milk fat trans-10 18:1 and trans-9, cis-11 CLA concentrations (Shingfield et al, 2006a).…”

“…Decreases in milk fat output during diet-induced MFD typically occur within a few days, and in more severe cases milk fat yield can be lowered by more than 50%, with little or no change in the yields of milk, milk protein or lactose Shingfield et al, 2006a). Secretion of all fatty acids is decreased during dietinduced MFD, but the reductions in the output of fatty acids synthesized de novo are disproportionately greater (Bauman and Griinari, 2003).…”

The effect of fish oil supplementation of pregnant and lactating ewes on milk production and lamb performance

“…It is therefore postulated that the adsorbent nature of the vermiculite carrier included in the current study may have rendered the long-chain PUFAs less available to ruminal bacteria, thereby negating potential negative effects. Alternatively, PUFA supplementation may have metabolic effects upon DM intake via shifts in ruminal biohydrogenation leading to an increased supply of unsaturated fatty acids at the duodenum as suggested by Shingfield et al (2006). Measures of ruminal biohydrogenation were not made within the current study; however, the increases in C 18:1 trans and cis-9, trans-11 CLA within plasma of ewes fed fish oil indicate that biohydrogenation of C 18:2 (n-6) and C 18:3 (n-3) to C 18:0 may have been inhibited in favour of intermediaries such as trans isomers of C 18:1 .…”