Comparing the effects of silage and hay from similar parent grass forages on organic dairy cows’ feeding behavior, feed intake and performance

While ensiling is globally the predominant forage preservation method, feeding hay as the sole source of forage has re-emerged in alpine, grassland-based dairying. Studies have shown that many factors could modulate the effects of the forage conservation method on cows’ responses, such as plant species, stage of maturity, cutting and wilting time, and forage cut length. In the present study, forages were obtained from the same fields (grass-dominated swards), mowed at the same time, and treated equally during wilting (roughly for 28 h; 56% DM at harvest). Windrows were harvested alternately using a loading wagon set to a specific cut length (8 cm), either for ensiling in a horizontal silo or barn-drying using an air dehumidifier. Nine months later, 2 feeding groups, with 9 cows each, were offered either one or the other of the conserved forages ad-libitum along with a fixed allocation of concentrate per cow (3.6 kg/d; DM basis) over a period of 34 d. Assignment of cows to groups was based on previous milk yield, body weight, DIM, and parity. Data collection started after a 14-d adaptation period. Data for covariate adjustment of chewing behavior, feed intake, milk performance parameters, and body weight were collected during a period of 9 d, prior to experimental feeding.Results revealed that the cows fed hay tended to increase forage DM intake (18.3 versus 17.8 kg/d; P = 0.07) and ingested a higher amount of water-soluble carbohydrates (+1.2 kg/d; P < 0.01). Hay-fed cows showed a trend towards a greater milk energy output (30.1 versus 28.5 kg energy corrected milk/d; P = 0.09) mainly due to an elevated milk fat yield (1.26 versus 1.16 kg/d; P = 0.02). The total chewing times in both groups were equal, suggesting that the physical effectiveness of fiber was the same, but the fact that cows on hay shortened rumination times per kg of ingested DM (P = 0.02) and NDF (P = 0.01) indicates a greater particle breakdown while eating. Cows on silage tended to sort against CP (P = 0.06) and had a significantly (P = 0.01) looser consistency of feces, but the DM contents did not differ (P = 0.15) when compared with those of hay-fed cows.It can be concluded that grass forages conserved as hay, rather than silage, were more attractive for cows and led to a higher milk energy output. Besides the preferential intake aspects, it can be assumed that the higher content of water-soluble carbohydrates in hay enhanced ruminal fermentation processes, which in turn provided cows with additional amounts of nutrients and energy.