Ruminal in situ disappearance and whole-tract digestion of starter feeds in calves before, during, and after weaning

Authors: GELSINGER, SONIA - University Of Wisconsin; Coblentz, Wayne; Zanton, Geoffrey; Ogden, Robin; AKINS, MATT - University Of Wisconsin

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2018
Publication Date: 2/13/2019
Citation: Gelsinger, S.L., Coblentz, W.K., Zanton, G.I., Ogden, R.K., Akins, M.S. 2019. Ruminal in situ disappearance and whole-tract digestion of starter feeds in calves before, during, and after weaning. Journal of Dairy Science. 102(3):2196-2206. https://doi.org/10.3168/jds.2018-15551.
DOI: https://doi.org/10.3168/jds.2018-15551

Interpretive Summary: The ability of calves to digest feeds changes over time with rumen development. This change is not well described. This study measured the degradability of feeds in the rumen and whole gastrointestinal tract of calves at different ages and fed different starter diets. Feed intake, fecal output, and ruminal degradability of feeds increased with time; whereas whole-tract digestibility of feeds decreased over time.

Technical Abstract: The objective of this study was to measure and compare rumen and whole-tract degradability of 2 calf starter diets and describe an in situ technique for estimating ruminal degradability of diets in calves at different ages. Ten bull calves (n=5/diet) were cannulated at 3 wk of age. They received milk replacer and one of 2 starter diets through wk 7, then starter only (up to 4500 g/d) through wk 15. Starter diets were a complete pellet (PEL; 42% starch, 13% NDF) and a texturized feed (TEX; 31% starch, 22% NDF). Portions of each diet were dried, ground through a 2-mm screen, and 1.25 g was inserted into concentrate in situ bags (5 cm × 10 cm, 50µm porosity). Each calf received duplicate bags of each diet for a total of 8 bags/calf (2 diets × 2 timepoints). All bags were inserted at the time of starter feeding. Half of the bags were removed at 9 h, the other half at 24 h. After removal from the rumen, bags were rinsed, dried (55o C, and composited by diet and by calf within week for NDF, N, and starch analyses. This process was repeated over 3 d during wk 5, 7, 9, 11, 13, and 15. Daily starter intake and total fecal excretion were recorded during the same 3-d periods. Diets, refusals, and feces were subsampled, dried, ground, composited by calf by week and analyzed for NDF, N, and starch content. Apparent digestibility coefficients, total intake, and fecal excretion were calculated and analyzed with a mixed procedure. Intake and fecal excretion of all measured nutrients increased from wk 5 through wk 15 of age and were greater for calves fed TEX. Whole-tract digestibility of DM, N, and starch decreased from wk 5 to 15, and was greater in calves fed PEL. Ruminal disappearance of DM, N, and starch after 9-h incubations and DM, NDF, and N disappearance after 24-h incubations increased linearly with age. Ruminal disappearance of DM and NDF was greater from PEL than TEX. Ruminal disappearance was estimable for DM, NDF, N and starch. In addition, changes over time and changes due to rumen environment were clearly demonstrated. Based on these data, there is potential to design specific rations and feed processing methods for calves based on their ability to utilize nutrients.