Fluid balance and metabolic response in athletic horses fed forage diets

• Concentrate diets are related to health problems in athletic horses and high-energy forage diets could be an alternative. Forage feeding may alter substrate and hindgut fluid availability which could be beneficial during feed deprivation and dehydration. However, it may also increase bodyweight (BW) and crude protein (CP) intake which may reduce performance. The objective of this thesis was to study trained Standardbred horses on a high oats diet (OD) and a high energy forage-only diet (FD) before and during 12 hour feed deprivation (Study I), and on two CP intakes during exercise and rest (Study II). In study I ten horses participated. In study II recommended and high CP intakes (diet RP and HP) from forage-only diets were studied in six geldings. BW and TPP were measured in both studies and plasma NEFA, acetate, glucose and insulin concentrations in study I, nitrogen and fluid balance and response to standardised race like exercise in study II. BW was higher on diet FD than on diet OD (3 kg) but was not affected by CP intake. The weight loss was larger during feed deprivation on diet FD than on diet OD. TPP was lower in diet FD before feed deprivation and the pre-feed deprivation level was maintained for 7 and 11 h on diet OD and FD, respectively. The plasma acetate and NEFA was higher, insulin was lower and urea and glucose unaltered on diet FD compared to diet OD before feed deprivation. During feed deprivation plasma NEFA and urea increased in both diets whereas the acetate decreased on diet FD and plasma insulin on diet OD. Plasma glucose was not affected by feed deprivation. Diet HP caused an increased N excretion, water intake and urine output and a lowered urine pH. CP intake did not affect heart rate, plasma lactate and blood pH during exercise. In conclusion, feeding horses diet FD resulted in a small increase in BW that diminished after feed deprivation. The plasma volume was larger and maintained longer on diet FD compared to diet OD which suggests that the horses were more resistant to dehydration. The effect of the altered metabolic response during feed deprivation to exercise remains to be investigated but a high CP intake did not adversely affect the response to exercise.

Ämnesord

LANTBRUKSVETENSKAPER  -- Husdjursvetenskap -- Husdjursvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Animal and Dairy Sience -- Animal and Dairy Science. (hsv//eng)

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