From calf ranch to harvest: health outcomes, management practices, and performance of beef-on-dairy cattle

Abstract

Breeding practices within the dairy industry have shifted to using beef semen to breed cows and have led to the increased production of crossbred beef-on-dairy calves that enter the beef supply chain. Similar to dairy replacement heifers, beef-on-dairy calves are separated from their dams shortly after birth and transported to calf ranches. A calf ranch is an off-site operation that raises calves from birth to a targeted weight or age depending on the marketing plans for that animal. The objective of this dissertation was to evaluate management practices, welfare, health, and performance of beef-on-dairy cattle from calf ranch through harvest. First, a survey of 15 commercial calf ranches was conducted. The survey focused on management of beef-on-dairy calves and consisted of 10 sections related to ranch demographics, calf arrival protocols, pre-weaning housing, starter feed, and milk offering, post-weaning housing and feed management, and health challenges and protocols. Results were descriptive, reported as frequencies of participants’ answers calculated as percentage of operations for each question. This survey revealed substantial variability in management practices across operations, highlighting a lack of standardized protocols for raising beef-on-dairy calves. Next, two cross-sectional observational studies were conducted focused on mortalities within commercial calf ranches. The first was conducted during the summer of 2023 at 2 calf ranches to report the frequency of causes of mortality and determine associations of breed (dairy vs. beef-on-dairy), sex (female vs. male), and days of age (< 30, 30 to 59, 60 to 89, > 90 days) with mortality diagnosis as determined via gross necropsy. Gastrointestinal (GI) and respiratory diagnoses were identified in high frequencies in young calves (18.5% and 71.1%, respectively), and the probability of GI and respiratory diagnoses were associated with days of age but not breed nor sex. Calves > 60 days of age were at greater risk for respiratory diagnoses compared to calves < 30 days of age, 88% vs 37%, respectively. In contrast, probability of a GI mortality diagnosis was greater for calves < 30 days of age compared to calves between 60 and 89 days of age, 46% vs 5%. The second cross-sectional observational necropsy study was conducted over 12 months to identify primary and co-morbidities in mortalities at commercial calf ranches and determine whether relative risk of RESP or GI diagnoses in mortalities varied by season (Period 1: Feb, Mar, Apr, May; Period 2: June, July; Aug, Sept; Period 3: Oct, Nov, Dec, Jan), sex (female vs. male), breed (dairy vs. beef-on-dairy), or ranch. Respiratory diagnoses were the most common (67.5%; 164/243) followed by GI (11.5%; 28/243). The location of GI lesions (none, upper GIT, lower GIT, or both upper and lower GIT) was also analyzed for associations with season, sex, breed, or ranch. Risk of diagnosing a calf with respiratory at time of necropsy or finding at least 1 GI lesion did not differ between season, sex, breed, or calf ranch. Location of GI lesion was also not significantly associated with season, sex, breed, or calf ranch. Next, a complete randomized block design was used (n = 26 male beef-on-dairy calves) to determine if a single topical dose of maternal bovine appeasing substance (MBAS) would decrease cortisol concentrations in blood, produce changes in behavior, and improve performance outcomes during and following weaning. Calves were randomly allocated to receiving a dose of MBAS or saline (CONT). Calves were housed individually in pens and stepped down from 2 bottles of milk to none over 3 days. Blood was collected to determine cortisol concentration. Accelerometers and cameras were used to assess behavior. Feed offerings and refusals were measured, and body weights were collected to assess performance. Cortisol concentrations were lower for CONT vs MBAS calves. No treatment effects were identified for performance metrics. Several treatment by time interactions were found for behaviors with CONT having more lying bouts than MBAS calves on day 0, the first day of step-down weaning, and day 2. This study demonstrated that MBAS altered behavior during weaning, but it did not improve performance or reduce stress, as indicated by blood cortisol compared to CONT. The fifth study was a prospective, observational study designed to determine the probability of treating a calf within 12 days of an adjacent calf being treated for diarrhea or respiratory disease. Hutch location and daily health records were collected for 9,756 calves. Calves treated for diarrhea or respiratory disease without an adjacent calf treated in the previous 12 days were classified as “noncontact”, whereas calves with an adjacent calf treated were classified as “contact”. The probability of treatment for both diseases was estimated based on contact status, age category, and their interaction. Daily probability of treatment for both diseases was significantly affected by the interaction between contact status and age. Calves < 30 days old (vs > 30 days) had higher probability of diarrhea treatment. For respiratory disease, contact calves had a higher probability of treatment within each age group; although magnitude of difference varied by age. These findings indicate proximity between hutches may influence disease and should be considered when managing the health of calves within a calf ranch. The final two studies investigated associations between various predictor variables and liver abscess (LA) prevalence at harvest in beef-on-dairy cattle during the finishing phase. The first study evaluated associations between origin, feedyard performance, and health metrics with LA at harvest in beef-on-dairy cattle. Feedyard data and liver scores were collected from two sources (Dataset 1 (D1) = 330 cohorts; Dataset 2 (D2) = 386 cohorts). For D1, a modified version of Elanco’s scoring system was used and 4 outcomes of interest were created (Total LA = all scores (D1TA), Severe LA = scores A+, A+Adhered (A+Ad), A+Open (A+Op) (D1SA), Severe+ LA = scores A+Ad, A+Op (D1S+A), and Severe LA as proportion of Total LA (D1ST). Dataset 2 used an in-house scoring system with non-mutually exclusive categories: Abscessed which consisted of livers with any abscess present (D2TA), Adhered which included livers with any adhesion present (D2AdL), and Condemned which consisted of livers deemed unfit to enter production chain and were condemned (D2CL). Multiple risk factors such as sex, days on feed (DOF), average shipping weight, percentage of cohort railed, and origin were associated with D1TA, D1SA, D1S+A, and D1ST. Average daily gain and quarter harvested were associated with D2TA and D2CL. Average shipping weight and origin were also associated with D2TA. The only risk factor associated with D2AdL was sex. Steer cohorts had higher probability (P ≤ 0.05) of D1TA, D1SA, D1S+A, D1ST, and D2AdL than heifer cohorts. Cohorts on feed > 300 days had higher probability (P ≤ 0.05) of D1TA, D1SA, and D1S+A than cohorts with fewer DOF. Cohorts with shipping weights of 680 to 725 kg had higher risk (P = 0.03) of D1SA than those > 726 kg. Cohorts with < 0.5% railed had lower probability (P ≤ 0.04) of LA outcomes than those with > 0.5% railed. Cattle harvested in quarter 3 had lower risk (P ≤ 0.03) of D2TA compared to quarter 4 and D2CL compared to all other quarters. Cohorts originating from region 3 had lower risk (P ≤ 0.05) of D1TA, D1SA, D1S+A, and D1ST than those from regions 1 and 4. These results identify factors associated with LA in beef-on-dairy cattle; further research is needed to determine management strategies to mitigate LA occurrence. The second LA study used feed intake data to determine the association of LA prevalence at harvest with feeding patterns in beef-on-dairy cattle during the finishing phase. Cohort-level closeout and daily feed delivery records were collected from 5 feedyards (n = 378 cohorts). Livers were scored using a modified version of Elanco’s scoring system, and the same categories were used from the previous study: Total LA (TA), Severe LA (SA), Severe+ LA (S+A), and Severe LA as proportion of Total LA (ST). Feeding patterns were described using several metrics: cluster analysis, area under the curve (AUC), descriptive measures of central tendency and variability during different periods relative to days on feed (DOF) and days to ship (DTS), and number of decreases from the previous day’s intake. All predictor variables were tested in univariate models, and those with a p-value ≤ 0.3 were tested in a multivariate model. Backward stepwise selection was used to eliminate predictors with the highest p-value until all remaining variables were significant (P ≤ 0.05). Measures of central tendency and variability of feed intake during different periods, cluster, and AUCs were significantly associated with multiple LA outcomes. For the DOF periods, as average intake increased, the probability of TA, SA, and S+A increased as well. For measures of variation, cohorts in the largest standard deviation category had lower probabilities of TA, SA, and S+A compared to cohorts with smaller standard deviations. Cluster was associated with TA and ST where cluster 5 had the highest probability of TA compared to clusters 2, 3 and 4. For ST, clusters 5 and 1 had lower probabilities of ST than cluster 4. There seemed to be a pattern where lower AUCs had greater probabilities of LA outcomes, and the probability decreased as AUC increase; however, this was not consistent across DOF/DTS periods or outcomes. Average intake, clustering of feed curves, and measures of variation were significantly associated with LA and could help identify management practices to reduce LA prevalence in beef-on-dairy cattle. In conclusion, this body of work advances understanding of beef-on-dairy calf management, health, and performance across the production system, from calf ranch to harvest. These findings demonstrate that factors such as calf age and proximity to calves previously treated may affect morbidity and mortality outcomes within the calf ranch. Additionally, origin, demographics, and feeding behaviors were associated with liver abscess outcomes identified at harvest, highlighting critical opportunities for intervention in the calf ranch and finishing phases. Together, these results highlight the need for more standardized, data-driven management strategies to improve animal health, welfare, and performance in the growing beef-on-dairy production system.