Intake, rumen fermentation characteristics, and feedstuff in situ digestion kinetics as influenced by fungal biomass in alfalfa hay fed to cattle

Abstract

The objective of this study was to investigate whether fungal biomass typically observed in molded hay would affect intake, rumen fermentation characteristics or digestion kinetics of feedstuffs in the rumen. Feeds assessed included corn grain, barley grain, canola meal, alfalfa hay, and barley straw. Three alfalfa hay treatments with similar nutrient profiles but varying in fungal biomass content were fed to late lactation, ruminally cannulated cows in a repeated 3 × 3 Latin square design. Dietary treatments had a 70:30 ratio, dry matter (DM) basis, of test hay and barley-based concentrate; the hays containing 1.6, 2.5 and 3.3 g glucosamine kg −1 DM. Mycotoxins were not detected in the hay treatments. Test feeds were incubated in the rumen for 0.1, 2, 4, 6, 8, 12, 24, 48, 72, and 96 h. Dry matter intake was similar ( P > 0.05) across treatments and averaged 2.1% BW. Volatile fatty acids and rumen pH were not influenced ( P > 0.05) by fungal biomass in alfalfa hay. Fungal biomass in hay did not influence ( P > 0.05) rate and extent of DM degradation in corn grain, barley grain, canola meal, and alfalfa hay; rate and extent of CP degradation in canola meal and alfalfa hay, or rate and extent of neutral detergent fiber (NDF) degradation in alfalfa hay and barley straw. Rate of DM degradation and effective DM degradability of barley straw was higher ( P < 0.05) when incubated in the rumen of cows fed hay with higher amounts of fungal biomass. Presence of fungal biomass in alfalfa hay does not affect the rate and extent of DM, CP, and NDF degradation of feedstuffs commonly used in ruminant rations but may affect rate and extent of DM degradation of highly lignified feedstuffs such as barley straw.