Effects of feeding UFA-rich cold-pressed oilseed cakes and sainfoin on dairy ewes’ milk fatty acid profile and curd sensory properties

Abstract

A lactation study was carried out utilizing 72 ewes in a 2 × 3 factorial arrangement involving two forages: Tall fescue (FES) and sainfoin (SAIN) hays; and 3 concentrates, which contained hydrogenated prilled palm fat (CTR), cold-pressed sunflower cake (SUN) or cold-pressed rapeseed cake (RPS) as fat sources. Ewes were divided into 6 equilibrated groups of 12 ewes each, according to milk yield and days in milk. Concentrates were offered individually and forage was group fed ad libitum. Milk yield was daily recorded; individual samples of milk were taken for fat, protein, lactose and for fatty acid (FA) composition analysis. Dry matter intake (DMI) and organic matter apparent digestibility (OMD) were estimated using two markers. Feeding behaviour was recorded for 48 h. Blood samples were collected for non-esterified fatty acids, blood urea nitrogen and IGF-1 determinations. Curd acceptance test was carried out using a non-trained sensory panel using a 10-point line scale for the attributes of appearance, flavour, odour, texture and overall acceptability. Milk yield and composition were analysed using the MIXED procedure for repeated measures with fixed effects of concentrate, forage and week, their interaction and the initial record measured at week 0 as covariate, and day and ewe as random effects. Total, hay and concentrate DMI, OMD, plasma metabolites and milk FA profile were analysed using the GLM procedure. Feeding behaviour and sensorial data were analysed using the previous statistical model but without including a covariate. SUN reduced milk total saturated fatty acids (SFA) compared to CTR with both forages, while RPS only reduced SFA with SAIN. Polyunsaturated FA were increased with both cakes and SAIN. SUN increased n-6:n-3 ratio compared to CTR (+54%) and RPS (+62%), and SAIN reduced this ratio compared to FES (−27%). SUN reduced milk index of atherogenicity compared to CTR (up to −33%) with both forages, while RPS reduced (up to −31%) this index only with SAIN. Concentrate did not affect milk production, digestibility and intake, but SAIN increased these traits together with plasma IGF-1. Neither concentrate nor forage affected curd acceptance traits. Healthier milk can be obtained with cakes. Nevertheless the forage used in the ration seems to be of great importance. Neither cakes nor SAIN had a detrimental effect on digestibility, production performance or curd acceptance in lactating ewes.