The utilization of diets containing acetate, propionate or butyrate salts by growing lambs

Abstract

1. In a comparative slaughter experiment growing lambs were given concentrate diets in which 7, 15 or 22% of the metabolizable energy (me) provided by barley was replaced by sodium and calcium salts of acetic acid, or 22% of me was replaced by Na and Ca salts of propionic or butyric acids.2. The efficiency of utilization for fattening (k_f) of the diets containing 0, 7, 15 or 22% of me as acetate was 57.2, 59.6, 54.1 and 48.8 (se ± 1.8) respectively, the last value being significantly lower (P < 0.001) than the first. The k_f for successive increments of acetate was 90, 37 and 19% (se ± 13), the decrease being significant (P < 0.001).3. The k_f values of the diets containing 22% of me as propionate or butyrate respectively were 48.7 and 50.6 (se ± 1.8), both values being significantly lower than the control (P < 0.01). The partial k_f of propionate was 19±13, and of butyrate 28 ± 13%.4. It is concluded that the experiment provided evidence that the efficiency with which acetate is utilized for energy retention is not constant, but varies with its contribution to me. The experiment also provided some evidence that large amounts of propionate and butyrate may be inefficiently utilized by growing lambs, although poor utilization of high levels of volatile fatty acid (VFA) salts per se cannot be entirely excluded.