Physiological effects of starter-induced ruminal acidosis in calves before, during, and after weaning

Authors: GELSINGER, SONIA - UNIVERSITY OF WISCONSIN; COBLENTZ, WAYNE; Zanton, Geoffrey; Ogden, Robin; AKINS, MATTHEW - UNIVERSITY OF WISCONSIN

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2019
Publication Date: 2/15/2020
Citation: Gelsinger, S.L., Coblentz, W.K., Zanton, G.I., Ogden, R.K., Akins, M.S. 2020. Physiological effects of starter-induced ruminal acidosis in calves before, during, and after weaning. Journal of Dairy Science. 103(3):2762-2772. https://doi.org/10.3168/jds.2019-17494.
DOI: https://doi.org/10.3168/jds.2019-17494

Interpretive Summary: It is unclear whether low rumen pH causes similar physiological dysfunction in calves as it does in adult cattle. Starter diets were developed to induce or blunt ruminal acidosis, and intake, body weight gain, feeding behavior, blood parameters, rumen environment, and structural parameters were monitored as indicators of calf health. Calves offered the diet designed to induce acidosis consumed less starter, exhibited altered feeding behaviors, grew at a slower rate, and exhibited a greater degree of rumen tissue degradation compared to calves offered the starter diet designed to blunt ruminal acidosis. Symptoms of ruminal acidosis in calves appear similar to those observed in adult cattle, and the etiology of the disease seems to follow similar mechanisms. It is clear from this study that symptoms can be moderated by diet, but further research is needed to determine whether symptoms can be nutritionally prevented, or whether calves that experience ruminal acidosis are more susceptible to the disease as adults.

Technical Abstract: The objective was to use dietary treatments to induce or blunt rumen acidosis in young calves and compare indicators of rumen and systemic health between the 2 diets. Ten bull calves (n=5/treatment) were ruminally-cannulated at 3 weeks of age and received milk replacer and 1 of 2 calf starter diets that were designed to cause (AC; pelleted, 42.7% starch, 15.1% NDF) or blunt (BL; texturized, 35.3% starch, 25.3% NDF) rumen acidosis. Mean birth weight was 38.7 ± 1.3 kg. Bodyweight and calf starter intake were measured weekly. Rumen contents were sampled at -8, -4, 0, 2, 4, 8, 12 and 24 hours relative to starter feeding during weeks 6, 8, 10, 12, 14, and 16 of the trial. Blood was collected from the jugular vein during the same weeks for complete blood cell count, blood pH and partial pressures of oxygen and carbon dioxide. Feeding behavior was assessed during week 16. Marker systems were used to estimate liquid passage and VFA absorption rates. Calves were harvested at 17 weeks of age, and rumen tissue was collected and assessed for papillae length, width, and degree of tissue degradation. Mean ruminal pH ± S.E. (min, max) was 5.4 ± 0.24 (3.3, 7.2) and 5.6 ± 0.24 (3.5, 6.8) for AC and BL calves, respectively. Lowest pH values were observed the week after weaning. Total ruminal VFA concentrations were 131.5 and 124.8 ± 2.4 mM in AC and BL calves, respectively, and increased with age and time after feeding. Dry matter intake was lower in AC calves at week 4 and remained lower through week 16. Feeding behavior also was altered at week 16. Bodyweight also was lower for AC calves from week 5 through 16. Blood hemoglobin and hematocrit were lower in AC calves, but other blood characteristics were not different. Rumen volume increased with age and tended to be greater in BL calves. Passage rate and papillae length and width were not different between treatments, but AC calves experienced a greater degree of tissue degradation. Ruminal acidosis symptoms in calves appear similar to those observed in adult cattle, and the etiology of the disease seems to follow similar mechanisms. It is clear from this study that symptoms can be moderated by diet, but further research is needed to determine whether symptoms can be nutritionally prevented, or whether calves that experience ruminal acidosis are more susceptible to the disease as adults.