Effect of Short-Chain Fatty Acids on Voluntary Feed of Broiler Chicks

Studies were conducted on the effect of feeding various low-molecular-weight fatty acids on the voluntary feed intake (FI) of broiler chicks. In a series of experiments, the effect of single intubations of various organic acids on FI during the following 24 h was investigated in male broiler chicks 2 to 3 wk of age. The various compounds diluted in glycerol were given at 100, 200, 300, or 600 mg/kg BW in various intubated volumes. The zero-level birds received glycerol only. Intubation of propionic acid (but not of formic, acetic, butyric, valeric, or caproic acid) significantly decreased FI linearly (P<.05). Glycolic acid (hydroxyacetic acid) also significantly depressed FI as did di- and trichloroacetic acid. Neutralized with KOH, propionic acid still significantly depressed FI in a linear manner. In a second study, the effect of dietary incorporation of acetate and propionate, as the Ca salt or free acid, on FI from 7 to 21 days of age was investigated in chicks. Propionate depressed voluntary FI more than acetate, and the Ca salt depressed FI more than the free acid. Propionate (but not acetate) significantly depressed the deposition of abdominal fat. Another experiment with various levels of lactic acid fed from 21 to 28 days of age revealed no significant effect on FI. Propionic acid has a specific effect on the appetite of chicks, but acetic acid also reduces their appetite when included in the diet in a nonvolatile form.