Steaming represents a strategy for reducing dust and mold concentrations and increasing dry matter intake in some hays, but can result in leaching of essential nutrients.
Management strategies for horses with respiratory disease include soaking hay prior to feeding. Hay steaming is an alternative to this practice; however, little is known about its impact on forage nutritive values or intake. The objective of this research, conducted at the University of Minnesota, was to determine the effect of steaming on forage nutritive value and intake by horses.
Two alfalfa-orchardgrass mixed hays were evaluated: a low and moderately moldy hay. Six mature horses were used in a 10 day cross over design. Three horses were assigned to each hay type and treatments were switched on day 6. Each day, one bale of each hay was sampled (pre and post-steaming) and steamed for 90 minutes using a commercial hay steamer. Two flakes of steamed or unsteamed low or moderately moldy hay were weighed and offered simultaneously to each horse in individual hay nets. Horses were allowed access to hay for 2 hours, any remaining hay was collected and 2 hour dry matter intake was calculated. Six additional bales of low and moderately moldy hay were used to evaluate the effect of steaming on total suspended particulate (TSP) or "dust". Flakes of unsteamed or steamed hay were agitated in an electric cement mixer, and TSP was recorded every minute for 30 minutes.
Steaming increased hay moisture and therefore reduced dry matter to 77 and 81% for low and moderately moldy hay, respectively. In low and moderately moldy hay, steaming reduced phosphorous (P) content by 16 and 17%, respectively. Steaming reduced water soluble (WSC) and ethanol soluble carbohydrates (ESC) by 13% and 27% respectively, for moderately moldy hay, but had no effect on low mold hay. Steaming reduced mold concentrations in both hays by ≥ 91%. Total suspended particulate of moderately moldy hay was reduced by 55%, but TSP in low mold hay was not affected by steaming (P = 0.445). Dry matter intake of low mold hay was increased by steaming; horses ingested 0.64 kg of unsteamed and 2.02 kg of steamed hay. Dry matter intake of moderately moldy hay was not affected by steaming. For low mold hay, steaming decreased P and mold concentrations, increased dry matter intake of the hay, but had no effect on TSP. In moderately moldy hay, steaming reduced P, WSC, ESC, mold concentrations and TSP, but did not affect dry matter intake.
Steaming represents a strategy for reducing TSP and mold concentrations and increasing dry matter intake in some hays, but can result in leaching of essential nutrients.