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Volatile Fatty Acids in Concentrate Rations for Lactating Dairy Cows

Department of Animal Science, Macdonald College of McGill University, Ste. Anne de Bellevue, Quebec, Canada

ABSTRACT

Varying proportions of acetic and propionic acid (70:30, 5050, 30:70) were included in concentrate rations at 0, 3, 6 and 9 %. Rations were made isonitrogenous by varying amounts of dry shelled corn and corn gluten feed. Each ration was fed to five cows at 1 kg per 3.5 kg milk for 84 days. Forages, including hay and green chop or haylage, were offered ad libitum. Each concentrate ration also was fed to three wethers for 21 days. Voluntary intake and digestibility were determined.

There were no significant differences between rations for milk production, but persistency of milk yield was greater (P < .05) for the 6%-70:30 ration than that of the 3%-70:30, 3%-50:50 or 9%-30:70 rations. The 9%-70:30, 3%- and 9%-30:70 rations resulted in higher (P < .05) milk fat percentages than the 9%-50:50 ration. Average daily gains were affected by ration (P < .05) with the 50:50 rations approximating the basal ration.

Sheep digested more cellulose of high volatile fatty acid rations than of basal ration (P < .05). Differences in digestibility of dry matter, energy and protein were not significant (P < .05). Dry matter and digestible energy intakes were depressed with the 9%-50:50 ration.