Lactational, digestive and metabolic effects of supplementing dairy ewes with barley Beta-glucans

Lactational, digestive and metabolic effects of supplementing dairy ewes with barley Beta-glucans: A set of 5 conventional and new varieties of barley with different features (waxy-hulless, waxy-hulled, non-waxy-hulled) were evaluated by analyzing its nutritive composition, Beta-glucans content and in situ rumen degradability for dairy ruminants. The working hypothesis was that new varieties may have higher nutritive value and functional properties (i.e., lactogenic) for livestock. Barley waxy varieties showed higher crude protein (plus 2.3 per cent units) and P-glucans (plus 2.6 per cent units) contents than non-waxy varieties, whereas hulless varieties had less crude fiber content (-2.1 per cent units) and higher energy value (4 to 7 per cent UFL), according to INRA (2007) and PrevAlim (v.3.23) than the hulled varieties. With regard to the rumen degradability, all the barley varieties had a similar and high DM, CP and Beta-glucans degradability (on average, 93.8 plus minus 1.6, 97.6 plus minus 0.3 and 100.0 plus minus 0.3 per cent, respectively), being 85 per cent of components immediately soluble. In a second experiment, a commercial barley Beta-glucans extract (Glucagel) was used, to evaluate the in vivo effects of Beta-glucans supplementation in the performance and metabolic profile of lactating dairy ewes at the short-term. With this aim, a new design of metabolic cages specially conceived for lactating dairy ewes was developed. Five Lacaune lactating dairy ewes (66.7 plus minus 2.6 kg BW; 202 plus minus 22 DIM and 1.58 plus minus 0.12 kg per d milk yield) were allocated in the metabolic boxes and submitted consecutively to 2 dietary treatments (C, control 10w in Beta-glucans; BG, Beta-glucans supplementation at a rate of 1.62 g per kg metabolic BW) during 10 d (C, dl to 5; BG, d6 to 10). No changes in milk yield, milk composition and digestibility were detected for BG, but a higher feed efficiency (BG vs. C., 1.69 vs.1.77 kg DM intake per kg ECM) with a 6 per cent reduction in feed intake were observed. Plasma cholesterol and albumin tended to be lower in BG vs. C ewes, whereas plasmatic glucose and NEFA did not change. Metabolomic analyses (600 MHz 1H NMR spectroscopy) showed higher P-glucose in plasma of BG ewes, when compared to C, which was supported by specific dynamic ELISA analysis of Beta-glucans (Fungitell), indicating that they left the rumen not fully degraded and that were absorbed. On the other hand, less carnitine, lecithin, creatine and 3-metylhistidine in milk were observed in the BG ewes, agreeing with a better nutritive stage. Moreover, less acetic and higher hippuric acids were found in the urine of BG vs. C ewes. In conclusion, new waxy barley varieties, high in Beta-glucans, showed higher nutritive value and positive metabolic effects at the short-term, recommending their use in dairy ruminants. Further research is needed a mid and long-terms