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Effects of Slaframine on Ruminant Digestive Function: Liquid Turnover Rate and Fermentation Patterns in Sheep and Cattle¹

North Carolina State University, Raleigh 27695 and Vanderbilt University, Nashville, TN 37232

Abstract

Two trials were initiated to determine if slaframine (SF) can be used to alter fluid digesta flow and fermentation patterns in the rumen. In trial 1, a preliminary experiment, four Dorset x Barbados Black-belly ruminal-cannulated wethers (avg weight 41.6 ± 8.7 kg) given ad libitum access to a pelleted concentrate/hay diet were injected intramuscularly with 0, 12, 24 or 48 µg SF/kg body weight (BW) in a 4 x 4 Latin-square design. Ruminal fluid dilution rate was determined using a single intraruminal infusion of polyethylene glycol (7 g), followed by seven hourly ruminal fluid samples. The administration of 48 µg SF/kg BW increased (P<.10) ruminal volume and outflow by 27 and 25%, respectively, compared with controls. In trial 2, two Hereford and two Angus ruminal cannulated steers (avg weight 568 ± 93 kg) were injected with 0, 6, 12 or 24 µg SF/kg BW at 8-h intervals over a 24-h period in a 4 x 4 Latin-square design. Steers were fed a concentrate diet at twice maintenance in 24 equal portions daily. Ruminal fluid dilution was measured using a single intraruminal infusion of cobalt-ethylenediamine tetraacetic acid (20 g) administered 9 h after the initial SF injection. Ruminal fluid was collected each hour during 8 to 24 h after the initial SF injection and analyzed for pH, osmolality and volatile fatty acids (VFA). For the 24 µg SF/kg BW treatment, ruminal fluid dilution rate (P<.16) and outflow (P<.04) were 26% greater, ruminal pH was .33 units higher (P<.05) and ruminal propionate concentration and molar proportion (mol/100 mol total VFA) were 36 and 26% lower (P<.05) than the control treatment. Saliva was estimated to contribute 50% more (P<.05) liquid to the ruminal fluid phase for the 24 µg/kg BW treatment than the control treatment. These studies demonstrate the potential for altering the physiological processes controlling ruminal environment and its dependent microbial fermentation using an exogenously administered sialagogue.

¹ Paper no. 10422 of the Journal Series of the North Carolina Agr. Res. Ser., Raleigh, NC 27695-7601. The use of trade names in this publication does not imply endorsement by the North Carolina Agr. Res. Ser. of the products named, nor criticism of similar ones not mentioned.

² Animal-Forage Metab. Complex, Dept. of Anim. Sci.

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. of Anim. and Dairy Sci., Univ. of Georgia, Athens.

⁵ Address correspondence to this author.

⁶ Dept. of Anat., Physiol. Sci. and Radiol., North Carolina State Univ.

⁷ Dept. of Poul. Sci.

⁸ Dept. of Biochem., Vanderbilt Univ. Supported by Public Health Service Grant ES00569 from the Natl. Inst. of Health.