Effect of conventional and intensified milk replacer feeding programs on performance, vaccination response, and neutrophil mRNA levels of Holstein calves.

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.

Immune responses in lactating Holstein cows supplemented with Cu, Mn, and Zn as sulfates or methionine hydroxy analogue chelates.

The aim of this study was to compare effects of inorganic sulfate versus chelated forms of supplemental Cu, Mn, and Zn on milk production, plasma and milk mineral concentrations, neutrophil activity, and antibody titer response to a model vaccination. Holstein cows (n=25) were assigned in 2 cohorts based on calving date to a 12-wk randomized complete block design study. The first cohort consisted of 17 cows that had greater days in milk (DIM; mean of 77 DIM at the start of the trial) than the second cohort of 8 cows (32 DIM at the start of the trial). Diets were formulated to supplement 100% of National Research Council requirements of Cu, Mn, and Zn by either inorganic trace minerals (ITM) in sulfate forms or chelated trace minerals (CTM) supplied as metal methionine hydroxy analog chelates, without accounting for trace mineral contribution from other dietary ingredients. Intake and milk production were recorded daily. Milk composition was measured weekly, and milk Cu, Mn, and Zn were determined at wk 0 and 8. Plasma Cu and Zn concentrations and neutrophil activity were measured at wk 0, 4, 8, and 12. Neutrophil activity was measured by in vitro assays of chemotaxis, phagocytosis, and reactive oxygen species production. A rabies vaccination was administered at wk 8, and vaccine titer response at wk 12 was measured by both rapid fluorescent focus inhibition test and ELISA. Analyzed dietary Cu was 21 and 23mg/kg, Mn was 42 and 46mg/kg, and Zn was 73 and 94mg/kg for the ITM and CTM diets, respectively. No effect of treatment was observed on milk production, milk composition, or plasma minerals. Dry matter intake was reduced for CTM compared with ITM cows, but this was largely explained by differences in body weight between treatments. Milk Cu concentration was greater for CTM than ITM cows, but this effect was limited to the earlier DIM cohort of cows and was most pronounced for multiparous compared with primiparous cows. Measures of neutrophil function were unaffected by treatment except for an enhancement in neutrophil phagocytosis with the CTM treatment found for the later DIM cohort of cows only. Rabies antibody titer in CTM cows was 2.8 fold that of ITM cows as measured by ELISA, with a trend for the rapid fluorescent focus inhibition test. Supplementation of Cu, Mn, and Zn as chelated sources may enhance immune response of early lactation dairy cows compared with cows supplemented with inorganic sources.

Effect of abomasal carbohydrates and live yeast on measures of postruminal fermentation.

Two studies were conducted to evaluate the effects of abomasal carbohydrate infusion on nutrient digestibility and fecal measures. In Exp. 1, 5 Holstein steers were assigned to a Latin square with 1-wk periods and were abomasally infused on a single day at the end of each period with water alone, a single pulse dose of water with 1 g/kg BW oligofructose or cornstarch, or 4 pulse doses of water with 0.25 g/kg BW oligofructose or cornstarch administered every 6 h. Total tract nutrient digestibility was not affected by treatment except for a tendency for a decrease in starch digestibility in response to the 1 g/kg BW dose of cornstarch ( < 0.10). Compared with the control, both oligofructose and starch infusions caused similar decreases in fecal pH ( < 0.05) and increases in fecal short-chain fatty acids ( ≤ 0.01) measured 12 h after the first infusion, with the single 1 g/kg BW infusions causing a greater magnitude of pH change compared with the four 0.25-g/kg BW infusions ( < 0.01). All treatments increased concentration of fecal lipopolysaccharide compared with the control for at least 1 time point following the infusion ( < 0.05), with a greater increase observed for the 0.25 g/kg BW infusions of oligofructose compared with the other treatments ( < 0.05). Results of Exp. 1 indicate that both oligofructose and cornstarch infusions increased carbohydrate fermentation in the intestines and can be used as a method to evaluate the impact of excessive intestinal fermentation on intestinal health. In Exp. 2, 6 Holstein steers received abomasal pulse doses of 0 (control) or 10 g/d live var. (SB) according to a crossover design with 18-d periods. Abomasal infusions of 4 pulse doses of 0.25 g/kg BW oligofructose administered every 6 h were conducted on d 16 of each period. During the baseline period prior to the oligofructose challenge, there were no effects of SB on fecal measures except for an increase in apparent total tract NDF digestibility ( < 0.05), suggesting that SB increased intestinal fiber fermentation. During the oligofructose challenge, SB increased fecal score ( = 0.03) and tended to reduce fecal short-chain fatty acids ( = 0.10). Results of Exp. 2 suggest that abomasal SB modestly stabilized the intestinal environment during increased carbohydrate fermentation.

Effects of abomasal oligofructose on blood and feces of Holstein steers.

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, ß-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.