Subacute ruminal acidosis can result in increased flow of fermentable substrates to the hindgut, which can negatively affect animal health and productivity. However, animal responses to increased hindgut fermentation independent of subacute ruminal acidosis have rarely been evaluated. This study determined the impact of abomasal dosage of a fermentable carbohydrate on animal performance and blood and fecal variables. Six ruminally cannulated Holstein steers fed a lactating dairy cow ration were used in a crossover design study with 14-d periods. On d 13 of each period, steers were infused abomasally with a pulse dose of 0 (control) or 1 (Oligo) g of oligofructose/kg of BW. Blood samples collected at 0, 3, 6, 9, 12, and 24 h after abomasal oligofructose dose were evaluated for metabolites (blood urea N, β-hydroxybutyric acid, and NEFA) and systemic inflammatory markers (Cu, serum amyloid A, and haptoglobin). Fecal samples, rectal temperature, heart rate, and respiratory rate were taken at 0, 3, 6, 9, 12, 24, and 48 h after abomasal dosage. Fecal samples were assayed for pH, DM percentage, consistency score (1=liquid to 5=coarse), and organic acid concentrations. Data were evaluated using a model including the fixed effects of treatment, time after dosage, and their interaction. Effects of treatment or treatment × time were not significant for DMI, blood variables, rectal temperature, or respiratory rate. Fecal pH was slightly reduced for Oligo compared with control steers (6.76 vs. 7.02; P=0.04). A treatment × time interaction occurred for fecal DM (P < 0.001). Compared with control steers, DM content of feces was reduced in Oligo steers at 6 h (12.6 vs. 15.2%) but increased at 9 h (16.3 vs. 15.0%) and 12 h (16.5 vs. 15.0). Fecal consistency score was reduced by the Oligo treatment at 6 h (1.44 vs. 2.83; P < 0.001) and 9 h (1.83 vs. 2.67; P=0.005). A treatment × time interaction was detected for fecal concentrations of lactate and acetate (P < 0.05) and tended to occur for propionate and butyrate (P < 0.10). The greatest difference for all organic acids occurred at 12 h, when fecal concentrations of lactate, acetate, propionate, and butyrate were 0.5, 47, 11, and 4.0 mM in control steers and 5.3, 76, 15, and 6.8 mM in Oligo steers, respectively. In summary, abomasal dosage of 1 g of oligofructose/kg of BW increased fecal excretion of microbial fermentation products in steers without causing metabolic acidosis, metabolic disruption, or inflammation.

This study compared conventional and intensified milk replacer feeding regimens on growth, intake, respiratory and fecal scores, vaccination response, and neutrophil mRNA levels. Holstein calves were randomly assigned to a 10-wk study on d 2 of life. Treatments were conventional (CON; n=8) and intensified (INT; n=7) milk replacer feeding programs. Conventional calves were fed a 20.8% crude protein and 21.0% fat milk replacer at 1.25% of birth body weight (BW) from wk 1 to 6 of life and 0.625% of birth BW during wk 7. A 29.3% crude protein and 16.2% fat milk replacer was fed to INT calves at 1.5% of birth BW during wk 1, 2% of current BW from wk 2 to 6, and 1% of current BW during wk 7. All calves were given milk replacer twice daily during wk 1 to 6, once daily during wk 7, and were weaned completely during wk 8. Calf starter intake was measured daily through wk 8. Body weight and withers height were measured weekly. Fecal and respiratory scores were recorded twice daily at feeding. Calves were vaccinated against ovalbumin at the end of wk 1, 3, and 5. Blood samples were collected at the end of wk 1, 3, 5, and 8 for analysis of serum anti-ovalbumin IgG concentration and for isolation of neutrophils. Quantitative PCR was used to measure neutrophil mRNA levels of 7 functionality genes. Treatment did not affect total DMI or anti-ovalbumin IgG response. Intensified milk replacer feeding increased average daily gain, protein intake, fat intake, and feed efficiency compared with the CON feeding program. Compared with CON calves, INT calves had greater fecal scores, indicating looser feces and greater respiratory scores, indicating more respiratory problems. Calves assigned to the INT treatment had increased neutrophil mRNA levels of L-selectin, and at wk 8, neutrophil cytosolic factor 1 was increased and toll-like receptor 4 tended to be increased compared with CON calves. This suggests greater activation of neutrophils in INT calves postweaning, but differences were relatively small and levels of the other 4 genes were unaffected. An INT milk replacer feeding program increased growth, fecal scores, and respiratory scores preweaning, increased mRNA levels of 2 neutrophil genes postweaning, and did not affect vaccination response.