Influence of Cottonseed Meal Supplementation and Cecal Antibiotic Infusion in Lambs Fed Low-Quality Forage. I. Intake, Digestibility, Nitrogen Balance and Ruminal and Cecal Digesta Kinetics

Abstract

Sixteen wether lambs (37 ± 3.7 kg) cannulated at the rumen and cecum were used in a 2 × 2 factorial to study the influence of cottonseed meal supplementation and cecal antibiotic infusion on feed intake and digestive physiology. Lambs were housed in metabolism crates and adapted to a basal diet (50% prairie hay, 50% oat straw mixture; 5.8% CP) for 15 d. Half the lambs were fed 189 g · head−1 · d−1 of cottonseed meal. On d 16, four lambs in each diet group were allotted randomly to receive either daily cecal infusion of 2 g neomycin sulfate or an equal volume (50 ml) of .15 M saline. On d 24, Co-EDTA and Cr-EDTA were infused into the rumen and cecum, respectively. Nylon bags containing basal forage were incubated ruminally on d 25 and 26. Beginning on d 28, feces and urine were collected for 7 d. On d 29, Yb-labeled hay was dosed ruminally. In vitro cecal gas production and fecal nucleic acid concentration were decreased (P < .01) by antibiotic infusion. Protein supplementation increased (P < .01) fecal nucleic acids. Forage intake and in situ DM and NDF disappearance were not influenced by treatment; however, in vivo DM and NDF digestibilities and N retention were increased (P < .05) by protein supplementation, but not by antibiotic infusion. Ruminal fluid dilution rate was decreased (P < .05) by both protein supplementation and antibiotic infusion. Cecal fluid kinetics and passage of Yb-labeled hay were not altered by treatment. Cecal antibiotic infusion had little influence on feed intake and digestibility, but cottonseed meal supplementation increased NDF digestibility and N retention.