Whole intact rapeseeds or sunflower oil in high-forage or high-concentrate diets affects milk yield, milk composition, and mammary gene expression profile in goats

Abstract

This study aimed to ascertain the response of goat mammary metabolic pathways to concentrate and lipid feeding in relation to milk fatty acid (FA) composition and secretion. Sixteen midlactation multiparous goats received diets differing in forage-to-concentrate ratio [high forage (HF) 64:36, and low forage (LF) 43:57] supplemented or not with lipids [HF with 130 g/d of oil from whole intact rapeseeds (RS) and LF with 130 g/d of sunflower oil (SO)] in a 4 x 4 Latin square design. Milk yield, milk composition, FA profile, and FA secretion were measured, as well as the expression profiles of key genes in mammary metabolism and of 8,382 genes, using a bovine oligonucleotide microarray. After 3 wk of treatment, milk, lactose, and protein yields were lower with HF-RS than with the other diets, whereas treatment had no effect on milk protein content. Milk fat content was higher with the HF-RS and LF-SO diets than with the HF and LF diets, and SO supplementation increased milk fat yield compared with the LF diet. Decreasing the forage-to-concentrate ratio from 64:36 to 43:57 had a limited effect on goat milk FA concentrations and secretions. Supplementing the LF diet with SO changed almost all the FA concentrations, including decreases in medium-chain saturated FA and large increases in trans C18:1 and C18:2 isomers (particularly trans-11 C18:1 and cis-9, trans-11 conjugated linoleic acid), without significant changes in C18:0 and cis-9 C18:1, whereas supplementing the HF diet with RS led to a strong decrease in short- and medium-chain saturated FA and a very strong increase in C18:0 and cis-9 C18:1, without significant changes in trans C18:1 and conjugated linoleic acid. Despite the decreases in milk lactose and protein yields observed with HF-RS, and despite the decrease in milk medium-chain FA and the increase in C18 FA secretion with RS or SO supplementation, none of the dietary treatments had any effect on mammary mRNA expression of the key genes involved in lactose (e.g., alpha-lactalbumin), protein (e.g., beta-casein), and lipid metabolism (e.g., lipoprotein lipase) after 3 wk of treatment. In addition, transcriptome analysis did not provide evidence of treatments inducing significant changes in the expression of specific genes in the mammary gland. However, 2-way hierarchical clustering analysis highlighted different global mammary expression profiles between diets, showing that the gene expression profiles corresponding to the same diet were gathered by common groups of genes. This experiment suggests that after 3 wk of dietary treatment, other factors, such as substrate availability for mammary metabolism, could play an important role in contributing to milk FA responses to changes in diet composition in the goat.

Dietary sunflower oil modulates milk fatty acid composition without major changes in adipose and mammary tissue fatty acid profile or related gene mRNA abundance in sheep

“…LPL, CD36 and FABP3). These findings are consistent with previous research in dairy goats fed plant oils (Bernard et al, 2009a and2009b;Ollier et al, 2009), suggesting that, in the absence of MFD, diet-induced changes in the content of milk long-chain FA might not be mediated by changes in the mRNA abundance of these particular candidate genes. They would also suggest that other regulatory mechanisms such as post-transcriptional events linked to higher availability of 18-carbon FA may be involved (Bernard et al, 2008).…”

Alteration of gene expression in mammary gland tissue of dairy cows in response to dietary unsaturated fatty acids

“…A possible explanation for these results might be that the variability in the FA profile among the dietary treatments was not sufficient because the unprotected UFA sources had undergone extensive biohydrogenation by rumen microorganisms (Chilliard et al, 2007); and therefore, the contrast in absorbed FA composition between supplements was probably too small to cause large differences in mammary gland tissue gene expression. In agreement, Ollier et al (2009) supplementing mid-lactation multiparous goats with oil from whole intact rapeseed or sunflower did not find significant changes in the expression of 8382 genes in the mammary gland, despite changes in milk composition. However, the lack of differently expressed genes between UFA sources could also be the result of a high variability in the expression levels of genes in the mammary gland within groups of treatments, as biological variation is intrinsic to all organisms (Churchill, 2002).…”

“…Lastly, the mixedeffects ANOVA allows to treat the cow as a random effect, which captures variability between individual cows within the same condition (Churchill, 2004). Ollier et al (2009) also analyzed genome-wide expression in the mammary gland of goats fed with diets differing in forage-to-concentrate ratio supplemented or not with lipids by ANOVA, including diet, period and animal group effects. However, in our study, the expression of genes in mammary gland was not significantly affected by the different dietary unprotected UFA sources.…”

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

“…Supplementing high-forage diets with rapeseeds or highconcentrate diets with sunflower oil were shown to increase milk fat synthesis in the goat (Ollier et al, 2009). Inclusion of sunflower oil altered the concentrations of most fatty acids in milk characterized by relatively large increases in trans 18:1 and 18:2 isomers, whereas rapeseeds resulted in marked reductions in the concentrations of fatty acids synthesized de novo and enhanced 18:0 and OA content, in the absence of substantial changes in trans 18:1 and CLA isomers.…”