Protein utilisation in response to caecal corn starch in ponies

The influence of administering caecal corn starch (0.0, 0.2, 0.4 or 0.6 g/kg body weight/day) on protein utilisation in 4 ponies was analysed with a latin square experimental design. The basal diet was dehydrated alfalfa pellets. Determinations were made of nitrogen retention, protein and dry matter digestions, total plasma protein, plasma urea nitrogen, plasma ammonia and plasma-free amino acids. Twice daily administration of corn starch into the caecum resulted in an increased nitrogen retention (P less than 0.01). Maximum nitrogen retention was observed with the caecal administration of 0.4 g/kg bwt of corn starch/day. Nitrogen retention expressed as percentage of the nitrogen absorbed was significantly higher (P less than 0.01) when corn starch was caecally administered. Digestion coefficients for dry matter and protein tended to be higher in ponies receiving the corn starch. Values of blood urea nitrogen in ponies administered the 0.0, 0.2, 0.4 or 0.6 g levels were 7.74, 6.47, 5.36 and 7.39 mmol/litre, respectively. Total plasma protein concentration was not changed by treatment. A lower plasma ammonia level was observed at the 0.4 g/kg bwt treatment level when corn starch was administered via the caecum. A trend toward an increase in plasma essential amino acid concentrations of isoleucine, phenylalanine, leucine, arginine and threonine were observed with ponies receiving caecal corn starch. Likewise, non-essential amino acid concentrations of tyrosine, serine, proline and glycine were also elevated. A slight increase in glycine concentration was observed at the 0.2 g/kg bwt treatment level. These results suggest that the administration of corn starch into the caecum resulted in more efficient utilisation of nitrogen by the large intestine.