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North Carolina State University, Raleigh 27695 and Vanderbilt University, Nashville, TN 37232
Abstract
Four esophageal- and ruminal-cannulated Angus steers (avg weight, 308 kg) were used to investigate how salivation is affected by the administration of purified slaframine (SF; l-acetoxy-6-aminooctahydroin-dolizine), a cholinergic secretagogue isolated from Rhizoctonia leguminicola. Steers were fed a concentrate diet at twice the net energy requirement for maintenance in hourly increments. In trial I, a single injection of SF was administered to four steers intramuscularly at 0, 6, 12 and 24-µg/kg body weight (BW) in a 4 x 4 Latin-square design. Saliva was collected via esophageal cannula at 15-min intervals 30 min after each feeding, weighed, sampled and reinfused via ruminal cannula over a 10-h period. At 12- and 24-µg SF/kg BW, salivary flow was 31 to 43% greater (P<.01) than at 0- or 6-µg SF/kg. Response peaked within the first 3 h and returned to baseline levels at 8 h. Buffering capacity and pH of saliva were not different (P>.10); however, osmolality and Na concentration increased and K concentration decreased (P<.10) as salivation rates increased. Feed intake of steers did not appear affected at any level of SF administration. In trial 2, 0-. 12- and 24-µg SF/kg BW were repeatedly administered intramuscularly to three steers in a 3 x 3 Latin-square design at 8-h intervals for 24 h. Salivary flow was measured and sampled over the entire 24-h period, as in trial 1. Flow rates were increased 50 to 70% (P< .01) by SF treatment. The pattern of response was similar to that found in trial 1. Response to SF did not decrease with subsequent injections. Effects of SF on osmotic pressure. pH. buffering capacity and Na and K concentrations were similar to those found in trial 1. Saliva protein and n-acetylneuraminic acid concentrations decreased (P<.10) with increased saliva flow rates. Slaframine may be a useful tool in furthering our understanding of the effects of salivary flow on ruminal function.
1 Paper no. 9879 the Journal Series of the North Carolina Agr. Res. Serv., Raleigh 27695-7601. The use of trade names in this publication does not imply endorsement by the North Carolina Agr. Res. Serv. of the products named, nor criticism of similar ones not mentioned.
2 Animal-Forage Metabolism Complex. Dept. of Anim. Sci., North Carolina State Univ.
3 Part of a thesis submitted to the Graduate College of North Carolina State Univ. in partial fulfillment of the requirements for the Ph.D. degree in Anim. Sci.
4 Present address: Dept. Anim. and Dairy Sci., Univ. of Georgia, Athens 30602.
5 Address correspondence to this author.
6 Dept. of Poul. Sci., North Carolina State Univ.
7 Dept. of Food Anim. and Equine Med., North Carolina State Univ.
8 Dept. of Biochem., Vanderbilt Univ. Supported by Public Health Service Grant ES00569 from the National Institutes of Health.
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