Intake and digestibility of meat ewes belonging to two contrasting feed efficiency genetic lines, during their two first production cycles

Abstract Feed is the largest cost in animal production, therefore improving feed efficiency (FE) is one of the main priorities when redesigning farming systems. The objective of this work was to evaluate the effects of a divergent genetic selection for FE in Romane rams [i.e. efficient (RFI-) or inefficient (RFI+)] on the feed intake and nutrient digestibility of their daughters (ewes), reared in different conditions. Different to their sires, which were fed high concentrate-diets, the ewes were fed ad libitum total mixed ration (TMR) composed of silage (65%), hay (25%) and barley (10%). A series of in vivo digestibility trials were conducted using Romane ewes (n =20; 10 RFI- and 10 RFI+) during their 2 first production cycles. The BW, metabolic BW (MBW), body condition score (BCS), DM intake (DMI) and nutrient intake and digestibility were individually monitored. All parameters were significantly affected (P