Concentration and heritability of immunoglobulin G and natural antibody immunoglobulin M in dairy and beef colostrum along with serum total protein in their calves

Immunoglobulin (Ig) G and natural antibody (NAb) IgM are passively transferred to the neonatal calf through bovine colostrum. Maternal IgG provides pathogen- or vaccine-specific protection and comprises about 85 percent of colostral Ig. Natural antibody IgM is less abundant but provides broad and non-specific reactivity, potentially contributing to protection against the dissemination of pathogens in the blood (septicemia) in a calf’s first days of life. In the dairy and beef industries, failure of passive transfer (FPT) of colostral Ig (serum total protein (STP) <5.2 g/dL) is still a common concern. The objectives of this study were to, i) compare colostral IgG concentrations and NAb-IgM titers between dairy and beef cows; ii) assess the effect of beef breed on colostral IgG; iii) compare passive transfer of colostral Ig in dairy and beef calves; and iv) estimate the heritability of colostral IgG and NAb-IgM. Colostrum was collected from Holstein dairy (n=282) and crossbred beef (n=168) cows at the University of Guelph dairy and beef research centres. Colostral IgG was quantified by radial immunodiffusion and NAb-IgM was quantified by an enzyme-linked immunosorbent assay. In dairy (n=308) and beef (n=169) calves, STP was estimated by digital refractometry. Beef cows had significantly greater colostral IgG (146.5 ± 9.5 SEM g/L) than dairy cows (92.4 ± 5.2 g/L, p <0.01). Beef cows with a higher proportion of Angus ancestry had significantly lower colostral IgG (125.5 ± 5.8 g/L) than cows grouped as “Other” (142.5 ± 4.9 g/L, p= 0.02). Using the FPT cut-off, 13% of dairy and 16% of beef calves had FPT; still, beef calves had a significantly larger proportion with excellent passive transfer (STP ≥6.2 g/dL, p <0.01). The heritability of colostral IgG was 0.04 (± 0.14) in dairy and 0.14 (± 0.32) in beef. Colostral NAb-IgM titers in dairy (12.12 ± 0.22, log2 (reciprocal of titer)) and beef cows (12.03 ± 0.19) did not differ significantly (p=0.71). The range of NAb-IgM titers was 9.18 to 14.60, equivalent to a 42-fold range in antibody concentration. The heritability of colostral NAb was 0.24 (± 0.16) in dairy and 0.11 (± 0.19) in beef cows. This study is the first to compare colostral NAb-IgM between dairy and beef cows. Based on the range in NAb-IgM titers and the heritability, selective breeding may improve colostrum quality and protection for neonatal calves in the early days of life.

Dairy vs. beef production – expert views on welfare

Consumers’ views and concerns about the welfare of farm animals may play an important role in their decision to consume dairy, meat and/or plants as their primary protein source. As animals are killed prematurely in both dairy and beef industries, it is important to quantify and compare welfare compromise in these two sectors before the point of death. Seventy world-leading bovine welfare experts based in 23 countries, were asked to evaluate the likelihood of a bovine to experience 12 states of potential welfare concern, inspired by the Welfare Quality® protocol. The evaluation focused on the most common beef and dairy production systems in the experts’ country, and was carried out separately for dairy/beef calves raised for red-meat, dairy/beef calves raised for veal, dairy/beef calves raised as replacement, and for dairy/beef cows. The results show experts rated the overall likelihood of a negative welfare state (i.e. welfare risk) to be higher in animals from dairy herds than from beef herds, for all animal categories, regardless of whether they were used to produce milk, red-meat or veal. These findings suggest that consuming food products derived from common dairy production systems (dairy or meat), may be more harmful to the welfare of animals than consuming products derived from common beef production systems (i.e. from animals solely raised for their meat). Raising awareness about the linkage between dairy and meat production, and the toll of milk production on the welfare state of animals in the dairy industry, may encourage a more sustainable and responsible food consumption.

Prevalence, Risk Factors, and Antimicrobial Resistance Profile of Respiratory Pathogens Isolated From Suckling Beef Calves to Reprocessing at the Feedlot: A Longitudinal Study

Here, we investigated the prevalence and risk factors for the presence of Histophilus somni, Mannheimia haemolytica, Mycoplasma bovis, and Pasteurella multocida in the respiratory tract of calves from the spring processing to the reprocessing at feedlots. Additionally, we characterized, phenotypically and genotypically, the antimicrobial resistance (AMR) profile of the four species. Calves from 22 cow–calf operations were enrolled in the study (n = 30 calves per operation) and sampled by deep nasopharyngeal swabs at three time points: spring processing, weaning, or induction into feedlots, and at reprocessing at the feedlot. Isolates were tested for susceptibility using the minimum inhibitory concentration (MIC) test against commonly administered antimicrobials. Additionally, a subset of isolates underwent whole-genome sequencing to infer presence of AMR genes and resistance determinants. Among studied pathogens, P. multocida was the most prevalent species, regardless of time point, followed by M. haemolytica, M. bovis, and H. somni. For M. bovis, a sharp increase in prevalence was detected at the reprocessing sampling, whereas for P. multocida, an increase in prevalence was observed at the weaning/induction sampling. Comingling and co-location of feedlots were not associated with prevalence of any respiratory pathogen. In terms of AMR, resistance against macrolides was prevalent in M. bovis, with most isolates resistant against tildipirosin, tilmicosin, and tylosin. In general, there was limited evidence to support an increase in resistance rates of respiratory bacteria from the spring processing to reprocessing at feedlots, with the exception of florfenicol resistance in M. bovis, which increased at reprocessing. Metaphylactic administration of tetracyclines at feedlot induction was not associated with the MIC of tetracyclines in any respiratory bacteria. Conversely, there were clear associations between the parenteral use of macrolides as metaphylaxis at the feedlot induction, and increased MIC against macrolides in P. multocida, M. haemolytica, and H. somni. Overall, the AMR phenotypes were corroborated by presence of AMR genes. We hypothesize that the administration of macrolides such as tulathromycin at feedlot induction contributes to historical changes in macrolides MIC data of respiratory bacteria of beef cattle.

Long-Acting Moxidectin for the Control of Gastrointestinal Nematodes in Preweaned Beef Calves in Tropical Areas

Gastrointestinal nematodes (GINs) in beef calves in the preweaning period can be an underestimated problem, and an adequate control program can result in increased productivity. In the current scenario of anthelmintic resistance, clinical studies with highly effective molecules with a prolonged period of action can contribute to the development of technologies applied in the field. The objective of this study was to evaluate the effects of a 10% moxidectin formulation (10%MOX), administered to calves aged 4–5 months, in the control of gastrointestinal nematodes and weight gain until the time of weaning. The study was divided into 2 stages. The first stage was carried out on a farm, with a randomized block design based on fecal egg counts (FEC), live weight, number of calvings of the mother, breed of the calves, and pickets. In the second stage, the study was repeated on 10 other farms, following a completely randomized design, to confirm the results obtained in the first stage. In all experiments there was a treated group and a placebo group. In the first stage, the effectiveness of 10%MOX in the FECRT performed on the 38th day post-treatment was 98.49%, and the treated animals still had lower FEC averages and a 9.4 kg increase in weight at weaning compared to those from the placebo group. In the second stage, the average increase in weight gain was 6.1 kg, confirming the results of the first stage. The study demonstrated effective control of GINs and improvement in the productive performance of calves treated in the preweaning phase, using 10% moxidectin.

PSXV-27 Late-Breaking: Evaluation of antioxidant capacity in receiving beef calves challenged with lipopolysaccharide (LPS)

The objective of this study was to evaluate antioxidant capacity in plasma of beef calves challenged with LPS. Following an initial feeding period of 40 d, steers (n = 32; 379 kg ± 30.7) were transported to the Livestock Issues Research Unit’s Bovine Immunology Research and Development Complex and challenged intravenously with LPS (0.25 µg/kg BW) on d 41. Blood samples were collected via jugular catheter at -2, 0, 2, 4, 6, 8, 10, 12, 18, 24, 36 and 48 h relative to the LPS challenge at 0 h. Blood samples were processed to isolate plasma for indicators of oxidative stress with a colorimetric assay to determine ferric reducing antioxidant power (FRAP) values via concentration of ferrous iron (µM). Data were analyzed as repeated measures using the GLIMMIX procedure of SAS. Antioxidant values did vary with time (P < 0.001) being greater (P < 0.05) at -2, 0, 2, 36, and 48 h. Antioxidant capacity was reduced at 6 and 8 h (P < 0.05), with the least FRAP value observed at 8 h post-challenge. Antioxidant capacity increased (P < 0.05) again at 10 h, showing similar (P > 0.05) concentrations to those observed at 4 h. By 24 h post-challenge, plasma FRAP values increased (P < 0.05) similar to initial values at -2, 0, and 2 h. It can be inferred that oxidative stress contributes to reduced antioxidant capacity, ultimately interfering with animal growth and productivity. While these values reflect the oxidative stress response to an acute endotoxin challenge, and a subsequent recovery returning to homeostasis within 24 to 48 h, they may also correlate with other physiological and immunological indicators associated with an acute endotoxin challenge.

94 The Effects of Weather, Body Weight, and Dry Matter Intake on Total Daily Water Intake in Beef Steers

Weaned angus steers (n = 26; 272.92 + 21.29 kg) were selected to study the effects of weather, predicted daily BW, and DMI on total daily water intake (TDWI) from December 2019 to May 2020 (181 days). Calves were provided with ad libitum access to feed and water, under a monoslope barn, for the duration of the study. In periods of cold stress, cattle were provided with corn stalk bedding within the dry lot, away from the monoslope barn. Measurements of feed and water disappearance were obtained by utilizing an automated feed and water system (Insentec RIC, Hokofarm, Marknesse, Netherlands), where disappearance was assumed to be caused by intake. Calves were weighed every 28 days in order to calculate ADG and therefore predict daily BW for each calf. Daily weather records, including windchill (°C), solar radiation (W/m2), and maximum relative humidity (%), were obtained through the South Dakota Mesonet automated weather station located 3.86 km from where the calves were housed. A linear mixed effects model with both random intercept and slope were used to account for the within subject correlations. Increased TDWI was associated with increased wind chill (0.38-kg per 1°C; P < 0.0001), increased solar radiation (1.04-kg per 1 W/m2; P < 0.0001), and decreased maximum relative humidity (-0.14 kg per 1%; P < 0.0001). For every kg increase in DMI, TDWI increased by 1.07 kg (P < 0.0001). Lastly, for every kg increase in BW, TDWI increased by 0.05 kg (P < 0.0001). Effects of DMI, BW, SRAD, windchill, RHMax were predictive of TDWI in beef calves fed during the winter. This model will be useful for predicting TDWI during the winter months where calves are raised in regions where temperatures are regularly below freezing.