The objective of this study was to evaluate the effects of incorporating 2 commonly used additives or spray-dried porcine plasma in calf milk replacer (CMR) on calf performance and health. Male Holstein calves (n = 158) transported from auction barns and local dairy farms were randomly assigned to receive 1 of 3 decoquinate-containing CMR for the first 49 d of the experiment: all milk protein and no additives (CONT); 15% of crude protein (CP) replaced with spray-dried porcine plasma, no additives (PLM); or all milk protein and an added combination of sodium butyrate (rate 1.4 kg of butyric acid/Mt) and Bacillus subtilis (1.28 million cfu/g of feed; BB). All milk replacers were formulated to contain 26% CP and 17% fat, 2.4% Lys, and 0.8% Met, and were bucket-fed at daily feeding rates of 520 g during wk 1 and 2, 650 g during wk 3, and 900 g during wk 4 and 5, in a total of 4, 5, and 6 L of solution, respectively. Calves were offered texturized calf starter (18% CP) upon arrival until wk 3 and transitioned to a corn and pellet ration with 2% straw (18.1% CP). No prophylactic administration of antibiotics occurred. All calves were gradually weaned over a 2-wk period. Calves were individually housed until weaned and then housed in groups of 5 in a mechanically ventilated facility in southwestern Ontario, Canada. Fecal scores, treatments administered (antibiotic or supportive therapy), and mortalities were recorded daily. Body weight was measured using a digital scale at arrival and at 14, 49, 56, and 78 d after arrival. No differences were found among the groups with respect to growth, feed efficiency, or incidence of diarrhea or respiratory infection treatment. Calves supplemented with BB had a greater hazard of mortality over the growing period compared with CONT. An interaction was found between the BB group and the level of total serum protein, with the BB group having a lower proportion of days with a fecal score of 3 when the calves had a higher total serum protein level. Calves fed PLM had a lower proportion of d with a fecal score of 3 relative to CONT but no difference in the proportion of d with a fecal score of 2 or higher. This study found that the addition of spraydried plasma in CMR reduced diarrhea severity; however, supplementing BB was associated with a higher hazard of calf mortality and had a varying response on fecal score.

The prophylactic use of oral antimicrobials, such as neomycin, in milk replacer (MR) or whole milk is a common practice in calf-rearing that is thought to aid in preventing disease. Heavy reliance on antimicrobials is of concern not only because of the development of antimicrobial resistance, but also because of the potentially negative effects on health. The objective of this study was to investigate the effects of neomycin on calf health and growth performance. One hundred and sixty calves (approximately 3-10 d of age), distributed across 2 experimental periods, were stratified by body weight (BW) and serum total protein, and assigned to 1 of 3 treatments: control (CON; nonmedicated MR, n = 60), short-term antibiotic (ST; neomycin mixed in MR from d 1-14, n = 50), or long-term antibiotic (LT; neomycin in MR from d 1-28, n = 50). Arrival BW (47.69 ± 0.87 kg) and serum total protein (5.67 ± 0.09 g/dL) were not different between treatment groups. Neomycin in ST and LT was dosed in MR at a rate of 20 mg/kg of BW and was adjusted weekly according to BW. Calf BW was measured weekly for 49 d, and health indicators (fecal score, attitude score, respiratory score, and rectal temperature), MR intake, starter intake, and the use of additional electrolytes and antimicrobials were recorded daily. Calves in the CON group experienced a higher proportion of days with diarrhea (20.32 ± 0.02%) compared with ST (14.70 ± 0.02%) or LT (13.80 ± 0.02%) calves, as well as longer bouts of diarrhea (7.45 ± 0.38 d, 5.69 ± 0.46 d, and 5.62 ± 0.45 d for CON, ST, and LT calves, respectively). Calves in the CON group also experienced higher fecal scores (score of 0.64 ± 0.04) than ST (score of 0.53 ± 0.04) or LT (score of 0.49 ± 0.04) calves, especially at d 7. However, no differences were observed in other health-related measures. The time to reach first diarrhea and first respiratory illness was not different between treatments, nor was the time to recover from respiratory illness. The time to intervention with additional electrolytes or antimicrobials was not different between treatment groups. Furthermore, growth performance, feed intake, and feed conversion ratio were not different. No differences were found when comparing ST and LT, except in the defined daily dose of total antimicrobials received. Calves in the LT group received a higher overall dose than ST calves, and both ST and LT calves received a higher dose than CON calves, which received no prophylactic antimicrobials. Given that there were no differences in performance variables and no additional health benefits aside from reduced fecal scores in calves fed neomycin, current practices involving the use of antimicrobials on dairy and veal operations need to be considered more prudently.

The objective of this prospective cohort study was to determine the effect of an abnormal fecal consistency score on weight gain and mortality in male Holstein calves and to identify risk factors associated with the occurrence of an abnormal fecal consistency score. This study enrolled 2,616 calves entering a calf-raising facility in Ontario, Canada, between January 2018 and December 2020. Fecal consistency scores were assigned twice daily for the first 28 d following arrival, where a score of 2, indicating runny consistency, and 3, indicating watery consistency, were classified as diarrhea. Severe diarrhea was classified by a score of 3. Serum total protein was measured upon arrival and the source of the calf (i.e., whether the calf came from a drover, local farm, or auction) was recorded. Body weight measurements were also collected at arrival and at 14, 56, and 77 d after arrival. Calf mortality and disease treatment during the first 77 d were recorded. On average, calves had diarrhea for 16% (4.51 d) of the first 28 d under observation, and severe diarrhea for 7% (1.87 d) of the 28 d under observation. Using a repeated measures linear regression model, we found the proportion of days with diarrhea significantly decreased weight gain at 14, 56, and 77 d following arrival. An increased proportion of days with diarrhea increased the risk of mortality, which was determined using a Cox proportional hazards model. We also found, using 2 Cox proportional hazards models, that a higher proportion of days with an abnormal fecal score increased the hazard of antibiotic treatment. With respect to factors associated with the occurrence of abnormal fecal consistency, we found that arrival weight and the source of calves were statistically significant predictors. Specifically, for every additional kilogram of body weight at arrival, the proportion of days with diarrhea decreased by 7%. With respect to source, calves from drovers had a higher proportion of days with diarrhea compared with those sourced directly from local dairy farms. Our results highlight the substantial influence the presence of abnormal fecal consistency has on short-term weight gain, mortality risk, and morbidity risk. We also demonstrate that diarrhea occurrence can be predicted using body weight at arrival and calf source. Further research should evaluate longer-term effects of diarrhea and better understand the effect of arrival weight on neonatal calf disease risk.

No abstract

Neomycin is commonly used in calf milk replacers (MR) to prevent diarrhea, however, antimicrobial exposure in early life may have consequences to gut development. The objective of this study was to investigate the effects of neomycin inclusion in MR on calf gut health and development. Thirty-six calves were randomly assigned to one of three treatments: control (CON), non-medicated (MR, n = 12), short-term antimicrobial exposure (ST: 20 mg/kg BW neomycin mixed in MR from d 1–14, n = 12), or long-term antimicrobial exposure (LT: 20 mg/kg BW neomycin in MR from d 1–28, n = 12). Fecal samples were collected weekly to measure total bacteria, and gut permeability was measured in week 2 and 4 by comparing serum recovery of orally dosed lactulose and D-mannitol markers. Calves were dissected at week 5 to collect intestinal tissues, which were used to analyze histology, gene expression and total bacteria abundance. Digesta samples were collected to analyze for total bacteria abundance and volatile fatty acid (VFA) concentrations. No treatment effects were found in the amounts of total bacteria in fecal, digesta, or tissue samples. Marker recovery in serum was higher at week 2 compared to week 4 (P < 0.01), suggesting that calves in early life have higher gut permeability. Histomorphological measures were similar, except for villi length in the distal jejunum, which was longest in ST calves (P = 0.05). Tight-junction, mucus, and inflammatory-associated gene expression was similar overall, although the expression of Tight junction protein-1 in the distal jejunum was lowest in CON calves (P = 0.04). Distal jejunum acetic acid, propionic acid, and total VFA tended to be highest in LT calves (P = 0.09; P = 0.06; P = 0.07, respectively). Although this study found few consequences of neomycin to gut health, the lack of benefits supports the argument that antimicrobials should be used prudently.