Effects of fish oil and starch added to a diet containing sunflower-seed oil on dairy goat performance, milk fatty acid composition andin vivoΔ9-desaturation of [¹³C]vaccenic acid

Abstract

The potential benefits on human health have prompted an interest in developing nutritional strategies for specifically increasing rumenic acid (RA) in ruminant milk. The aims of the present study were to (i) compare two dietary treatments with lipid supplements on milk yield and composition, (ii) measure the in vivo D9-desaturation of vaccenic acid (VA) to RA using 13 C-labelled VA and (iii) determine the effect of the dietary treatments on this variable. Treatments were 90 g sunflower-seed oil (SO) per d or 60 g sunflower-seed oil and 30 g fish oil per d plus additional starch (SFO), in a grassland hay-based diet given to eight Alpine goats in a 2 £ 2 cross-over design with 21 d experimental periods. Milk yield and composition were similar between treatments. Goats fed SFO had higher milk 6 : 0 -16 : 0 concentration, lower milk SC18 concentrations and showed no effect on milk VA and RA, compared with SO. At the end of the experiment, intravenous injection of 1·5 g [ 13 C]VA followed by measurements of milk lipid 13 C enrichment showed that in vivo 31·7 and 31·6 % of VA was D9-desaturated into milk RA in the caprine with the SO and SFO treatments, respectively. The expression of genes encoding for D9-desaturase (or stearoyl-CoA desaturase; SCD1, SCD5) in mammary tissues and four milk D9-desaturation ratios were similar between treatments. In conclusion, the present study provides the first estimates of in vivo endogenous synthesis of RA (63-73 % of milk RA) from VA in goats, and shows no difference between the two lipid supplements compared.

Effects of fish oil and additional starch on tissue fatty acid profile and lipogenic gene mRNA abundance in lactating goats fed a diet containing sunflower-seed oil

“…The goats were milked at 0730 and 1530 h, and fresh diets were offered in two equal meals after the milking. The effects of the treatments on animal performance and milk FA composition have been reported earlier (Bernard et al, 2010).…”

“…Several studies have highlighted the stability of goat milk fat secretion and composition under a variety of feeding strategies (Chilliard et al, 2007), including diet supplementation with sunflower-seed oil and fish oil (Bernard et al, 2010), which is a combination of lipid supplements that causes milk fat depression in dairy cows and sheep (Thering et al, 2009;Invernizzi et al, 2010;Toral et al, 2010). Although comparisons between studies can seldom be made because of the few data available in goats and the variation in basal diet composition and/or lipid supplementation, inter-species differences in lipid metabolism have been highlighted previously (Chilliard et al, 2007).…”

“…The experiment lasted for 21 days (which corresponded to the second period of a crossover study; see Bernard et al, 2010 for details). The goats were milked at 0730 and 1530 h, and fresh diets were offered in two equal meals after the milking.…”

“…In dairy goats, the partial substitution of sunflower-seed oil in the diet by fish oil (a source of very long-chain n-3 polyunsaturated FAs (PUFA)) reduced the n-6:n-3 FA ratio of milk fat without reversing the low saturated FA and the high c 9,t11-18:2 and t11-18:1 concentrations achieved (Bernard et al, 2010). Remarkably, feeding sunflower-seed oil and fish oil plus additional starch compared with sunflower-seed oil alone affected neither the percentage of t10-18:1 in milk fat nor dairy goat performance, which contrasts with the important reductions in milk fat content and yield and the marked -E-mail: laurence.bernard@clermont.inra.fr increases in t10-18:1 concentrations in cows or sheep fed n-6 PUFA-rich oils and fish oil (Invernizzi et al, 2010;Toral et al, 2010).…”

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

“…Endogenous synthesis via the action of SCD on trans-11 18:1 is responsible for 64% to 97% of cis-9, trans-11 CLA (Palmquist et al, 2005;Glasser et al, 2008b) and virtually all the trans-7, cis-9 CLA secreted in bovine milk (Palmquist et al, 2005). Experiments with 13 C-labelled trans-11 18:1 have estimated that 25% or 32% is desaturated to cis-9, trans-11 CLA in the bovine (Mosley et al, 2006) and caprine (Bernard et al, 2010) mammary gland, respectively.…”