Open access publications in the SLU publication database

Abstract

The objective of this thesis was to study the effects of forage crude protein content and forage conservation method on metabolism and hindgut ecosystem, abrupt feed changes and exercise response. In total 22 horses, both sedentary and athletic, were used. The sedentary horses were fistulated in right ventral colon and the athletic horses were in Standardbred race training. In the sedentary horses bacterial counts, volatile fatty acid (VFA), pH and dry matter (DM) in colon content and faeces and in the athletic horses nitrogen intake and excretion, fluid and acid-base balance, digestibility and exercise response were measured. Forages used in the studies were 1) grass silage with 13% (RP) and 17% (HP) crude protein, 2) grass hay, haylage and silage (same cut): 81%, 55% and 36% DM, 3) grass hay and silage (same cut): 82% and 45% DM and 4) grass haylage and silage (same cut): 68% and 41% DM. Colon VFA concentrations were higher and pH was lower on the HP diet than the RP diet. No other major alterations in composition and activities of the colon ecosystem were found. In the athletic horses urine and faecal nitrogen excretion and water intake increased and faecal DM decreased on the HP diet compared to the RP diet already within 48 h. Colon lactobacilli increased on the silage diet and streptococci decreased on the haylage diet compared to the hay diet, but there were no changes in VFA concentrations or pH. Apparent digestibility was higher on the silage diet compared to the hay diet. Estimated evaporative fluid loss was higher and tended to be higher on the silage diet than the hay diet and on the HP diet than the RP diet, respectively. Changes were observed already within 48 h. Heart rate, blood pH, plasma lactate and total proteins did not differ between the RP diet and the HP diet or between the haylage diet and silage diet during exercise and recovery. However, the increased urine and evaporative fluid losses might be a disadvantage during more prolonged exercise when fluid loss is a limiting factor.