Digestibility of wheat straw or ammoniated wheat straw in equine diets

Abstract

Summary Six mature mares of Quarter Horse and Paint breeding (average body weight 560 kg) were used in a replicated, completely randomized experiment to evaluate the acceptance and digestibility of diets containing untreated or ammoniated wheat straw. Horses were fed one of three dietary treatments: (1) 50% chopped, ammoniated wheat straw/50% chopped alfalfa hay (AMWS), (2) 100% chopped alfalfa hay (ALF), or (3) 50% chopped wheat straw/50% chopped alfalfa hay (WS). Horses were maintained in dry lots during the two experimental periods with ad libitum access to water, and were fed diets in two equal feedings daily totaling 1.6% of body weight. Dietary adjustment periods were 14 days, followed by fecal collection periods of 4 days. Total fecal output was determined using chromic oxide as an external indicator. Feed and fecal samples were analyzed for dry matter, nitrogen, acid detergent fiber, neutral detergent fiber and energy content. Dietary intake (dry-matter basis) was similar between treatments with means of 8.7, 9.1 and 8.8 kg/d for AMWS, ALF, and WS, respectively. Energy and protein digestibilities were greater for ALF than WS. Dry matter digestibility was greater for both ALF and AMWS than WS. Digestibility of acid detergent fiber was not different among treatments, however a trend (P