The effect of NaCl or NaHCO3 on digestion in the stomach of weaned calves

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Abstract
SUMMARY: The response to dietary inclusion of NaCl or NaHC03 at 42 and 60 g/kg (18 g Na/kg) respectively was examined in relation to rumen fermentation and the flow of nutrients to the duodenum of calves.Measurements were made with four calves on each diet at 8 and 11 weeks of age: weaning having taken place at 5 weeks of age.Osmotic pressure, pH, total VFA concentration and molar proportions of VFA were not significantly affected by the treatments imposed. Rumen dilution rate was increased by 28% on the NaHCO3 diet compared with the other two diets but this difference failed to achieve statistical significance. Mean duodenal flows of organic matter, modified acid detergent fibre and total amino acids were 0·52, 0·72 and 1·25 of the respective dietary intakes and were not significantly affected by the treatments imposed. NaHCO3, however, significantly increased the supply of α-linked glucose polymer to the small intestine (15% of dietary intake) compared with the control (4%) and NaCl (6%) diets. The results demonstrated that NaCl and NaHCO3 had small effects upon the digestion within the rumen of young calves with specific reference to flow of nutrients to the proximal duodenum. It is suggested that the stimulatory effect of NaHC03 on food intake and performance of calves may be attributable to an increase in rumen buffering capacity, and some indication of an increase in the fractional outflow rate of water and possibly particulate matter from the rumen.