The effects of bale density, type of binding and storage surface on the chemical composition, nutrient recovery and digestibility of large round hay bales

Abstract

Alfalfa-bromegrass forage was cut at midbloom, sun cured to 847 g dry matter (DM) kg −1 and baled as either high-density (189 kg m −3) or low-density (146 kg m −3) large round bales bound with either plastic mesh (2 cm between strands) or sisal twine spaced at 15 to 20 cm. Bales were stored outside either on a 15 cm layer of crushed rock (7.5 cm diameter) or on the ground. High-density bales had higher ( P < 0.01) mean temperatures during the first 32 days of storage than low-density bales. After 4 and 9 months of storage, high-density bales had a higher ( P < 0.05) DM concentration and a lower ( P < 0.01) proportion of N as acid detergent insoluble N (ADIN) than low-density bales; these effects were greatest in the outer 30 cm of the bales (density × part, P < 0.05). High-density bales had a greater ( P < 0.01) unweathered DM recovery than low-density bales. Plastic mesh-bound bales had: higher (binding × part, P < 0.01) in vitro digestible dry matter (IVDDM) concentrations, lower neutral detergent fiber (NDF; binding × part, P < 0.01), acid detergent fiber (ADF; binding × part, P < 0.01), acid detergent lignin (ADL; binding × part, P < 0.05) and ADIN (binding × part, P < 0.01) concentrations in their outer 30 cm and greater ( P < 0.01) recoveries of total DM, unweathered DM and IVDDM than twine-bound bales after 4 and 9 months of storage. Plastic mesh binding resulted in: smaller (density × binding, P < 0.01) increases in ADF, ADL and ADIN concentrations and smaller (density × binding, P < 0.05) decreases in total DM, unweathered DM and IVDDM recoveries in low-density than in high-density bales. Bales stored on crushed rock had lower ( P < 0.01) temperatures during the first 32 days than ground-stored bales. After 4 and 9 months of storage, rock-stored bales had higher ( P < 0.01) DM concentrations than ground-stored bales; this effect was greater in hay from the outer 30 cm of the bales (surface × part, P < 0.01). Bales stored on crushed rock had higher (surface × part, P < 0.01) IVDDM concentrations in their outer 30 cm and greater unweathered DM ( P < 0.01) and IVDDM ( P < 0.05) recoveries than ground-stored bales. In digestion trials, plastic mesh binding or rock storage of high- or low-density bales resulted in greater ( P < 0.05) DM intakes by sheep than twine binding or ground storage, but had no effects on hay DM digestibility.