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Salivary and Ruminal Characteristics, Respiration Rate and EKG Patterns of Steers fed a Pelleted or Ground Roughage Diet at two Levels of intake

U. S. Department of Agriculture¹

Abstract

An experiment was conducted to determine if an interaction exists between pelleting and level of intake of a roughage diet as related to the rate of salivary secretion. Subsequent changes in salivary composition, ruminal fill, pH and VFA, respiratory rate and EKG patterns were also investigated. Two groups of four esophageal and ruminal fistulated beef steers, averaging 365 kg., were used in two Latin squares. The treatments within each Latin square were identical and consisted of feeding an 81% roughage diet as a pellet or as a coarsely ground mixture at dry matter intake levels equal to 1% and 2% of body weight.

There was no detectable interaction between pelleting of a high roughage diet and level of intake as related to salivary flow of steers. No difference in salivary flow was found due to pelleting, and a slight but non-significant increase was observed when the level of intake increased. Dry ruminal ingesta weight increased with level of intake, and this increase was greater when the pelleted diet was fed. Pelleting lowered the molar percent of ruminal acetic acid, the C₂/C₃ ratio and C₂/C₄ ratio and increased the molar percent of propionic acid. Total VFA, the molar percent of butyric acid and the C₂/C₄ ratio was greater at the 2% level of intake. Ruminal pH, total VFA and the proportion of individual VFA were significantly affected by time after feeding. Heart rate and respiration rate were greater at the 2% level of intake and heart rate was greatest 2 hr. after feeding. EKG patterns were not affected by treatment.

¹ Animal Husbandry Research Division, A.R.S., Beltsville, Md.