37 Effects of Creep Feeding Duration on Rumen Fermentation Characteristics Using an Ex Vivo Model

• Published in: Journal of animal science 2023-10, Vol.101 (Supplement_2), p.248-249
• Main Authors: Silver, Jack T, Pugh, Lindsey M, Meteer, William T, McCann, Joshua C, Shike, Daniel W
• Format: Article
• Language: English
• Subjects: Acetates; Acetic acid; Body weight; Calves; Cattle; Concrete; Corn; Diet; Duration; Feeding; Feedlots; Feeds; Fermentation; Inoculum; Microorganisms; Propionic acid; Rumen; Solifluction; Substrates; Total mixed rations; Tubing; Weaning
• ISSN: 0021-8812; 1525-3163
• DOI: 10.1093/jas/skad341.282

Abstract The objective was to determine the effects of creep feeding duration on ruminal fermentation using an ex vivo model. Simmental × Angus, spring-born calves (n = 72) were stratified by age (83 ± 14 d) and body weight (BW) into 12 pens with 6 calves per pen. Pens were randomly assigned to 1 of 2 treatments: calves fed creep for 105 d (105dCF) or final 21 d (21dCF) before weaning. Cow-calf pairs were housed on concrete drylots with open-front buildings. Cows were limit-fed at maintenance a total mixed ration (TMR) that consisted of corn, grain coproducts, and corn stalks. Calves (n = 16) were utilized for ex vivo experiments. Experiment 1 was conducted on d 76, before the 21dCF calves having access to creep feed. Rumen fluid was collected from 8 calves per treatment via esophageal tubing and mixed with McDougall’s buffer (1:2 ratio). Each rumen fluid inoculum was combined with 2 substrates (cow TMR or creep feed) in a split-plot design and incubated for 24 h at 39°C. Data were analyzed using the MIXED procedure of SAS 9.4. In Exp. 1, there was no creep feeding duration by substrate interaction (P ≥ 0.16) for 24-h pH, butyrate, acetate, or IVDMD. Molar proportions of acetate and butyrate were greater (P ≤ 0.001) for the 105dCF calves than for the 21dCF calves. There was a treatment by substrate interaction (P = 0.02) for total VFA. The 105dCF calves had greater total VFA than 21dCF calves with a greater magnitude of difference observed with TMR substrate. Calves on 105dCF had greater (P < 0.01) IVDMD than 21dCF calves regardless of substrate (64% and 59%, respectively). Experiment 2 was conducted on day 105 after all calves were abruptly weaned and transported 263 km to the feedlot. Procedures were similar to Exp. 1, except substrates included creep feed and feedlot receiving diet. In Exp. 2, no treatment by substrate interaction (P ≥ 0.13) was observed for 24-h pH, acetate, propionate, total VFA, or IVDMD. Although acetate was greater (P < 0.01) for the 105dCF calves, propionate was greater (P < 0.01) for the 21dCF calves. There was no treatment effect (P = 0.57) for total VFA; however, it was greater (P < 0.01) for the creep feed substrate than for the receiving diet substrate. In Exp. 2, IVDMD tended to be greater (P = 0.06) for 21dCF calves than 105dCF calves. In conclusion, results indicated creep feeding improved ruminal fermentation ex vivo, but even a short-term creep feeding duration of 21 d appears to be adequate in preparing rumen microbial