Effects of rosemary essential oil on the milk production and fatty acid profiles of ewes fed oat hay or silage

Abstract. Milk and dairy products are among daily-consumed foods in most countries. However, milk production and characteristics depend mainly on animal feeding and additives. The basic feeding corresponds to green or conserved forage and concentrate. The aim of this study was to investigate the effects of a conserved oat forage form (hay, H, or silage, S) and rosemary essential oils (REO) as additives on milk production and the fatty acid (FA) profile of Sicilo-Sarde dairy sheep. Forty-eight lactating Sicilo-Sarde ewes were ranked into four homogenous groups. Two groups were fed oat hay (H) and the other group oat silage (S) ad libitum. All the ewes were supplemented with 600 g d−1 of concentrate. Within each form of forage, one group of ewes received a control concentrate, and the other group received the REO concentrate. The milk yield was not affected by REO intake but tended to be higher (P=0.07) for oat hay than for silage (570 vs. 510 mL d−1). The milk protein content was greater for oat silage than hay diets (5.8 vs. 5.3 %), given that the silage form contains more crude protein. In addition, the silage form of forage improved the milk FA profile, with higher C18:3n−3 (0.70 vs. 0.45 %) long-chain FA and polyunsaturated FA (PUFA) n3 proportions and a lower PUFA n-6/n-3 dietetic ratio (P<0.05). The milk of ewes receiving REO contained a lower percentage of vaccenic acid and n−6 PUFA but a higher percentage of n−3 PUFA and consequently lower n6/n3 (2.56) and PUFA / SFA (P<0.05) ratios. In conclusion, REO could be recommended for dairy ewes fed silage to improve the nutritional quality of their milk for human consumption.