Salts Of Volatile Fatty Acids Research Articles

Uilization of salts of volatile fatty acids by growing sheep. 3. Effect of frequency of feeding on the utilization of acetate and propionate by young growing lambs.

1. The effect, on the concentration of volatile fatty acids (VFA) in the rumen, of increasing the frequency of feeding from twice daily to four or six times daily was investigated in sheep given isocaloric rations containing VFA salts. In a second experiment isocaloric rations containing acetate and propionate were given to groups of lambs in two or six equal feeds daily. The efficiency with which the lambs utilized the VFA salts was measured as gain in live weight, empty body weight and carcass weight and was compared to that of lambs receiving only the basal ration. The composition of the carcasses was estimated from that of the loin. 2. Increasing the frequency of feeding from twice daily to four or six times daily significantly reduced the marked changes in rumen VFA composition associated with giving rations containing VFA salts twice daily. In lambs receiving acetate and propionate, final live weight, empty body weight and carcass weight were significantly greater than in lambs receiving only the basal ration (P < 0.001). The combustible energy from added VFA was apparently utilized more efficiently than the calculated metabolizable energy of the basal rations given above maintenance level, and there was no difference between the utilization of acetate and propionate. 3. There were no differences approaching significance between feeding twice daily and six times daily either between groups of lambs receiving only the basal diet or between those given the diets supplemented with VFA salts. Nor were there any interactions between VFA and frequency of feeding. 4. It is postulated that in ruminants the effect of frequency of feeding depends on the environment and level of feeding.

Utilization of salts of volatile fatty acids by growing sheep. I. Acetate, propionate and butyrate as sources of energy for young growing lambs.

1. An experiment was conducted in which sodium and calcium salts of acetic, propionic and butyric acids were given to groups of eight lambs as additions to basal diets of hay and concentrate. Two control groups were included, one group which received only the basal ration and one high-level control group which received sufficient additional concentrate to achieve growth rates greater than those of the groups receiving volatile fatty acid (VFA) salts. 2. With rumen-fistulated sheep, the effect on the rumen VFA composition and the pH of the rumen liquor, of diets supplemented with VFA salts given twice daily, was also investigated and compared with the effect of the basal diet alone. 3. The lambs receiving the VFA salts grew faster and achieved significantly greater empty body and carcass weights than those receiving only the basal rations; the high-level control group had significantly greater empty body and carcass weights than groups receiving salts of VFA. 4. There were no differences approaching significance in the efficiency of the three VFA in promoting gains in live weight, empty body weight and carcass weight. There appeared to be equal efficiency of utilization of the gross energy of the VFA and of the calculatedmetabolizable energy of the concentrates. 5. The effect of twice-daily feeding on the rumen VFA composition was that the concentration of the supple- mentary acid was greatest shortly after feeding, and about 5–6 h after feeding the effect was difficult to detect. There were no differences in the pH of the rumen liquor between animals given diets containing VFA salts and those given the basal ration.

Utilization of salts of volatile fatty acids by growing sheep. 2. Effect of stage of maturity and hormone implantation on the utilization of volatile fatty acid salts as sources of energy for growth and fattening.

1. In two experiments with growing and fattening lambs sodium and calcium salts of volatile fatty acids (VFA) were added to a basal diet of hay and concentrate. In Expt I the lambs were approaching maturity, and the utilization of salts of acetic, propionic and butyric acids was studied. In Expt 2 the animals were younger; the experimental groups received acetate or propionate, and half of them were implanted with hexoestrol. The chemical composition of the carcass was assessed with the loin as a representative joint. The influence of the VFA salts on the digestibility of the basal ration was also investigated. 2. In both experiments the lambs receiving supplements of VFA salts grew faster, and their empty body weights and carcass weights were significantly greater than in lambs receiving the basal diet. 3. The energy derived from acetate and propionate was utilized more efficiently to promote carcass gains than the calculated metabolizable energy above maintenance of the basal ration. There were no differences in the utilization of energy from the different VFA, except in Expt I in which butyrate was utilized somewhat less efficiently than acetate and propionate. 4. Hexoes-trol implantation resulted in faster growth, and highly significantly greater empty body weights and carcass weights. There was no evidence of an interaction between the VFA and hexoestrol treatments. 5. There were no differences between the VFA treatments in the composition of the carcass gains as judged by the composition of the loins, except in Expt I in which lambs receiving acetate tended to be the fattest. The coefficient of variation in loin fat percentages was large in both experiments, but, in Expt I in which both ewe and wether lambs were used, the coefficient of variation among the wether lambs was four times that of the ewe lambs. 6. Additions of VFA salts to the diet resulted in a significant increase in the excretion of ash.