ENHANCING MANAGEMENT AND HEALTH FOR BEEF × DAIRY MALE CALVES IN COMMERCIAL CALF-RAISING FACILITIES

Abstract

The commercial beef × dairy (B×D) calf population has expanded rapidly in the United States, yet management tools specifically designed for this population remain limited. Body weight prediction equations developed for purebred dairy or beef calves had not been evaluated in B×D calves, whose intermediate morphological characteristics may reduce the accuracy of those models. Moreover, the long-term consequences of transfer passive immunity (TPI) status and extended immunoglobulin G (IgG) supplementation on growth performance, health outcomes, and survival in this population have also not been characterized. In this dissertation, a series of studies were conducted to evaluate body weight (BW) prediction approaches for day-old B×D calves, assess the effects of extended IgG supplementation or transition milk replacer feeding on growth performance and health outcomes on B×D calves with good-excellent TPI; and determined the long-term consequences of TPI status and extended IgG supplementation on growth performance, health outcomes, and survival probability in B×D male calves over 180 days of life in a commercial calf-raising facility.In the first study, the objectives were to evaluate the performance of published equations for estimating the BW of day-old B×D male calves based on morphological measures, and to develop, test, evaluate, cross-evaluate, and validate BW-predictive equations using body measurements. A total of 320 B×D male calves were enrolled upon arrival at the calf-raising facility. Body weight at arrival and morphological measurements, such as heart girth (HG), hip height (HH), and hoof circumference (HC), were recorded from each calf within the first 24 h of life. Forty-six published peer-reviewed equations were evaluated against the development dataset using root mean squared error (RMSE), concordance correlation coefficient (CCC), and mean squared error decomposition (mean bias, slope bias, and residual error) to assess agreement between observed and predicted BW values. Three linear equations were developed using a forward selection criterion for HG (Eq. 01), HG and HH Eq. 02), and HG, HH, and HC (Eq. 03). In addition to linear models, evaluation of quadratic, cubic, and exponential models was assessed to determine the relationship between BW and morphological traits. Among the tested models, the linear equation proved more effective and simpler than the quadratic, cubic, and exponential models and was ultimately selected for validation. Among the 46 published equations evaluated, 76% demonstrated poor agreement with observed BW, as indicated by an average CCC (0.49) and an average BW RMSE of 107.00 kg. An additional 17% of the published equations achieved moderate agreement, with average CCC values between 0.50 and 0.60 and an RMSE for BW of 6.20 kg; only 7% (the top-performing published equations) had CCC values greater than 0.60 and an RMSE for BW of 4.50 kg. All three developed equations exhibited greater predictive performance than 43 (93%) of the published equations, with an average CCC of 0.75 and an RMSE for BW of 3.50 kg. Cross-evaluation of the three developed equations demonstrated moderate to high BW predicting performance (RMSE = 3.80 kg; CCC = 0.74).The validation assessment using an independent dataset of 176-day-old B×D male calves that only included HG as a morphological measurement indicated that the HG equation (Eq. [01]) had a moderate to high performance (RMSE = 3.80 kg; CCC = 0.64) in predicting the BW of day-old B×D male calves. Thus, indicating that this developed equation (Eq. [01]) can be applied as an on-farm tool to predict the BW of day-old B×D male calves. Because accurate BW estimation at birth represented a critical input for colostrum volume delivery and nutritional management of B×D calves, and because extended colostrum supplementation has been proposed as a strategy to improve health outcomes in calves, the second study evaluated the effects of extended feeding with IgG supplementation and transition milk replacer during the first 14 days of life on growth performance and health outcomes of B×D male calves with successful TPI. One hundred and twenty B×D male calves sourced from 12 commercial dairies in California, U.S., were enrolled upon arrival at a commercial calf-raising facility and confirmed to have good-excellent TPI (serum protein ≥ 5.8 g/dL). Calves were randomly assigned to one of three treatments for the first 14 days: milk replacer, extended IgG supplementation at 20 g/head/day, transition milk, or a control group. Serum total protein, growth performance, and health outcomes were monitored through 180 d of age, and mixed effects models were used with diet treatment as a fixed effect and dairy of origin as a random effect. Serum total protein concentrations were measured at arrival (d 1) and were similar (P = 0.38) among treatment groups. Growth performance was similar (P ≥ 0.28) among treatment groups at all time points. Health outcomes and mortality were similar (P ≥ 0.32) among treatments, and no mortality was recorded during the study period. Extended IgG supplementation or transition milk feeding provided no benefit to growth performance or health in male B×D calves with good-excellent TPI at arrival. Although extended IgG supplementation produced no benefit in calves with good-excellent TPI, whether TPI status itself determined long-term growth performance and survival in B×D calves managed through a commercial calf-raising facility had not been established. Therefore, the third study evaluated the effects of extended immunoglobulin G (IgG) supplementation during the first 14 days of life on growth performance, health outcomes, and survival of beef × dairy (B×D) male calves with different levels of transfer of passive immunity (TPI). A separated cohort of chapter 3 with a total of one hundred and sixty B×D male calves (initial BW = 42.4 ± 5.7 kg) sourced from 12 commercial dairies were enrolled upon arrival at a commercial calf-raising facility at Central Valley, California, U.S. Calves were classified by serum total protein (STP) concentration as poor-fair (fail) status (STP ≤ 5.7 g/dL) or excellent (successful) status (STP ≥ 6.2 g/dL) and randomly assigned within TPI status to treatments: 1) failure of TPI with no IgG supplementation (FNC); 2) failure of TPI with extended IgG supplementation (20 g of IgG/head/d) for 14 days (FEC); 3) successful TPI with no IgG supplementation (SNC); 4) successful TPI with extended IgG supplementation for 14 days (SEC). Data were analyzed as a 2 × 2 factorial with fixed effects for TPI status, treatment, and interaction, with calf as the experimental unit and dairy of origin as a random effect. There was no interaction (P ≥ 0.22) between TPI status and IgG supplementation in any of the growth performance variables. Body weight (BW) and average daily gain (ADG) did not differ (P ≥ 0.22) among treatment groups at any time point; however, calves with successful TPI had greater (P = 0.04) BW at d 80 and greater (P = 0.04) ADG from d 1 to 180 than calves with failed TPI. Extended IgG supplementation did not reduce (P = 0.71) diarrhea incidence in calves with failed TPI; however, calves with successful TPI, regardless of IgG supplementation, had reduced (P ≤ 0.01) diarrhea incidence compared to FNC calves. Extended IgG supplementation reduced (P = 0.03) total antibiotic treatment events by 22% in SEC-treated calves compared to FNC calves, with no reduction (P = 0.52) from extended IgG supplementation among excellent TPI. The treatment groups differed in overall survival probability during the 180-day observation period; the FNC group had the greatest mortality (20.0%), followed by FEC (12.5%), SNC (2.5%), and SEC (0%). Results from these studies indicated that the existing BW prediction equation was poorly accurate when applied to day-old B×D male calves, and that morphological equations developed specifically for this population offered a practical, accurate alternative for on-farm BW estimation. Extended IgG supplementation or transition milk replacement feeding produced no benefit in B×D male calves with good-excellent TPI at arrival, reinforcing that colostrum management at the source dairy was the foundational intervention for this population. Transfer of passive immunity at arrival was the primary determinant of growth performance, health outcomes, and survival in B×D male calves through 180 days of life, and excellent TPI was associated with a decrease in antibiotic use and a reduction of mortality during the calf-raising phase, whereas extended IgG supplementation provided no additional benefit beyond excellent TPI. Collectively, these observations underscore the critical importance of optimizing colostrum delivery at the source dairy and developing population-specific management tools to support the health and productive performance of B×D male calves in commercial calf-raising facilities.