Effects of forage to concentrate ratio in dairy ewes in early-lactation: 2. Milk fatty acid profile and cheese-yielding traits

Póster presentado al: 2017 ADSA Annual Meeting #T292. Pittsburgh, Pennsylvania (Estados Unidos), 25-28 de junio de 2017.

As the second part of the study reported by Elhadi et al. (Abstract M331),the effects of forage:concentrate ratio (F:C, %) were studied in 72 dairyewes (Manchega, MN, n = 36; Lacaune, LC, n = 36) in early lactation.Treatments were: high- (HF, 70:30), medium- (MF, 55:45) and low-forage(LF, 40:60). Ewes were fed indoors, in pens of 6, the HF diet during 4 wkand then the experimental diets (wk 5 to 8). Milk was sampled individuallyon wk 7 for composition (NIR system; Foss, Nordersted, DE) andcoagulation traits (Optigraph; Ysebaert, Frepillon, FR). Tank milk sampleswere collected by group and fat extracted (2000 × g, 15 min, 4°C) andconverted to FAME by base catalyzed transesterification for FA analysis bygas- chromatography. Milk composition varied by breed, being richer formain components in MN than in LC (P < 0.001), with no dietary effects onfat, protein and solids contents (P = 0.95 to 0.24) and only slight quadraticchanges in some FA (P = 0.23 to 0.001). On average, milk FA (g/100 g FAprofile was SFA:MUFA:PUFA = 70.3:24.0:5.7 and atherogenicity index 2.50.Nevertheless diet × breed interactions were detected in most milkcomponents and FA profile data (P = 0.01 to 0.001). Regarding the extremediets (HF vs. LF), no effects were observed in the FA saturation profile in MNewes, whereas SFA decreased (−2%, P < 0.001) and MUFA (4%, P =0.004) and PUFA (12%, P < 0.001) increased in LC ewes. Furthermore,comparing HF vs. LF, the C > 16 increased in the LC (2%; P = 0.031),whereas C > 16 and C16 decreased (−2% and −5%, respectively; P <0.05) and C < 16 increased, in the MN (6%; P = 0.010). Changes inatherogenicity index were negligible. No effect of concentrate was detectedon rennet coagulation time, rate of curd aggregation and laboratory cheeseyieldin both breeds (P = 0.95 to 0.052), except for firmness at min 45 andrate of curd aggregation, that increased (23% and 47%, respectively; P <0.05) in the HF vs. MF comparison in MN ewes. In conclusion, slightchanges in FA profile, and no benefits in cheese traits, were detected whenthe ratio forage:concentrate fell below the level required to satisfy thenutrition requirements of medium and high yielding dairy ewes.

Peer reviewed