Michael A. Steele

The aim of this study was to characterize dry and fresh period mammary metabolism as estimated via mammary plasma flow of the milk vein (MV; MPF_MV) and mammary acetate and glucose (glc) metabolism and to determine potential cow- and mammary-level factors that influence colostrum production. A total of 21 Holstein cows (n = 11 parity 2 [P2] and 10 parity 3 [P3] cows) were dried off at d-58 ± 3.4 relative to calving and followed until 7 ± 1 d in milk (DIM). All cows were provided the same dry and lactating diets supplying 46.4 and 54.4 Mcal ME/d, respectively. Starting at d-49 relative to expected calving, estimation of MPF_MV via Doppler ultrasonography, and mammary acetate and glc arteriovenous difference, uptake and clearance, were determined every other wk until wk-1 before expected calving, then every 4 d until actual calving, at calving, and at 7 ± 1 DIM by collection of frequent pairs of coccygeal vessel and MV blood samples. Colostrum was collected within 1.4 ± 0.76 h of calving, components were determined via mid-infrared spectroscopy, and IgG was determined by radial immunodiffusion. Mammary metabolism as estimated via MPF_MV and glc and acetate uptake was lowest from wk-6 to wk-4 relative to calving. Total MPF_MV began to steadily increase starting at wk-2, while mammary acetate and glc uptake only began to increase at wk-1 and d-4, respectively. The earlier increase in mammary acetate uptake may suggest its role in providing energy for mammogenesis and lactogenesis I, while mammary glc uptake may coincide with lactogenesis II and copious milk production. Assuming the complete oxidation of mammary acetate and glc uptakes, the average daily rate of energy expenditure of the dry mammary gland was 0.93 Mcal/d and equated to a total energy expenditure of 56.1 Mcal throughout the entire dry period. Correlation and regression analyses highlighted the importance of achieving adequate dry-off during the far-off period of high-producing cows in promoting colostrum production, as greater previous lactation milk yield and far-off mammary acetate uptake were negatively associated with colostrum yield. In summary, the mammary gland appears to achieve a non-secretory, low metabolic state between wk-6 to wk-4 relative to calving, and this period appears to be of greater importance in driving colostrum production than the close-up period. Future work should aim to uncover the relationships between dry period mammary metabolism, especially the non-secretory state during the far-off period, and prepartum mammogenesis and colostrogenesis.

Genetic selection for calf feed efficiency could lower rearing costs and environmental impact by breeding animals that meet growth requirements with fewer feed resources. Here we estimated genetic parameters for residual metabolizable energy intake (RMEI) as a calf feed efficiency trait using multiple-trait model estimates for energy sink traits and recursive modeling. Data comprised 4,662 weekly average records for metabolizable energy intake (MEI), average daily gain (ADG), and metabolic body weight (MBW) from 938 Holstein dairy calves collected in one research herd from 2016 to 2024. Multi-trait repeatability models including MEI, ADG, and MBW were fit separately for the pre-weaning (PreW; d 5 to 28 of life) and peri-weaning period (PeriW; d 46 to 60 of life), with age, year-season of birth, scour incidence, trial participation, and dam parity as fixed effects. Heritability estimates for PreW-RMEI and PeriW-RMEI were 0.11 and 0.33. In the PreW period heritability estimates for MEI, ADG, and MBW were 0.32 ± 0.05, 0.20 ± 0.04, and 0.54 ± 0.06 respectively. In the PeriW period heritability estimates for MEI, ADG, and MBW were 0.37 ± 0.06, 0.20 ± 0.04, and 0.51 ± 0.07 respectively. Genetic correlations among MEI, ADG, and MBW were moderate to high in the PreW (0.72 ± 0.06 to 0.86 ± 0.06) and PeriW (0.44 ± 0.12 to 0.72 ± 0.06) periods. PreW-RMEI relative breeding value correlations were favorable with heifer fertility traits, while PeriW-RMEI relative breeding value correlations were moderately favorable with selection indices (Pro$ and LPI) and estimated breeding values for protein and fat yield. These findings highlight that genetic selection could be implemented for PreW-RMEI and PeriW-RMEI as distinct early-life feed efficiency traits in dairy cattle. Future studies should be used to collect more phenotypic data across multiple herds and at different stages of life and estimate proper genetic correlations using multi-trait models.

The objective of this study was to determine whether increasing the dilution of colostrum replacer (CR) meals to reduce total solids (TS) influences serum IgG concentration, apparent efficiency of absorption (AEA), abomasal emptying rate, and gastrointestinal permeability in newborn calves. Forty-eight newborn male Holstein calves (46.9 ± 3.70 kg) were randomly assigned to receive a single CR meal (949 g, providing 150 g of IgG) via esophageal tube within 1 h after birth at different final volumes (FV). Different TS concentrations were created by mixing the CR powder with varying amounts of water giving 4 dose-response treatment groups: Control (n = 12) received 949 g of CR powder in 1.791 kg of water (FV = 2.64 L and TS = 360 g/L); Dilution 1 (DL-1; n = 12) received 949 g of CR powder in 2.083 kg water (FV = 2.97 L and TS = 320 g/L); Dilution 2 (DL-2; n = 12) received 949 g of CR powder in 2.574 kg water (FV = 3.39 L and TS = 280 g/L); and Dilution 3 (DL-3; n = 12) received 949 g of CR powder in 3.110 kg water (FV = 3.96 L and TS = 240 g/L). After CR feeding, 6 calves/treatment were catheterized for blood sampling at 1, 2, 3, 4, 5, 6, 8, 10, 12, 24, 36, and 48 h post CR feeding to assess abomasal emptying via acetaminophen. At 24 h, the same subset received lactulose, D-mannitol, and Cr-EDTA via esophageal feeder to evaluate gastrointestinal permeability, with blood being collected at 24, 26, 28, 30, and 32 h relative to CR feeding. Non-catheterized calves were blood sampled via jugular venipuncture at 0, 12, 24, 36, and 48 h relative to CR feeding, and daily thereafter from d 3 to d 7. Body weight was recorded at birth (BW_0h), at 48h (BW_48h), and at 7 d (BW_7d). Body weight, average daily gain at 48 h (ADG_48h), and d7 (ADG_7d), serum total protein (STP), AEA, and abomasal emptying rate did not differ among treatments. No differences in IgG absorption were observed, except for IgG AUC at 24 h and d 7. The IgG_AUC24 was greater in DL-2 (225.4 ± 18.9 mg·h/mL) and DL-3 (221.2 ± 18.9 mg·h/mL) compared with DL-1 (156.7 ± 18.9 mg·h/mL), with Control (191.7 ± 18.9 mg·h/mL) showing intermediate values. Further, IgG_AUCd7 was greater in DL-3 (11.7 ± 0.39 mg·h/mL) compared with the Control (8.9 ± 0.39 mg·h/mL), with DL-1 and DL-2 showing intermediate values. No time by treatment differences were observed in postprandial concentrations of lactulose, D-mannitol, and Cr-EDTA. However, a difference was observed in the time to reach maximum chromium concentration (CrTmax), which was shorter in DL-3 calves (5.7 ± 0.47 h) compared with Control (7.6 ± 0.47 h), DL-1 (7.3 ± 0.47 h), and DL-2 (7.3 ± 0.47 h). Results from the present study show that decreasing the osmolality of CR by adding water had minimal impact on overall IgG absorption, abomasal emptying rate, and gastrointestinal permeability in newborn calves.

Summary:This study aimed to determine whether breed and colostrum replacer (CR) quantity fed in the first 12 hours of life affects lymphocyte populations in blood. Male Holstein (H; n = 10) and Holstein × Angus (C; n = 10) calves were fed CR at either low (2.5 g of immunoglobulin G [IgG]/kg of body weight; n = 4 for H and 6 for C) or high (5.0 g of IgG/kg of body weight; n = 6 for H and 4 for C) quantities at 0 and 12 hours of life and followed for an 84-day period at a commercial rearing facility. The study revealed that feeding higher quantities of CR was associated with a higher proportion of IgM⁺ and IgM⁺CD21⁺ B cells among the total lymphocytes, which were identified using flow cytometry. However, breed was not found to be associated with differences in the lymphocyte population in the peripheral blood of calves. Created with BioRender.com.

The objective of this retrospective cohort study was to explore factors associated with neonatal calf diarrhea (NCD), bovine respiratory disease (BRD), lung consolidation (LC), and mortality on Ontario dairy farms. Health records from 2,349 Holstein calves from birth until 56 d of age across 9 dairy farms were analyzed using multivariable mixed-effects logistic regression models, which accounted for farm-level clustering through a random effect. The models evaluated associations between the outcomes of interest and season of birth, birth BW, calving ease, first colostrum feeding volume, colostrum quality (measured as Brix percentage), number of colostrum feedings, time of birth, and transfer of passive immunity (TPI), using the categories of poor (<5.1 g/dL), fair (5.1-5.7 g/dL), good (5.8-6.1 g/dL), and excellent (≥6.2 g/dL). Season of birth was the only variable associated with NCD (23% incidence), with calves born in the summer having higher odds of NCD (odds ratio [OR] = 1.54; 95% CI: 1.08-2.20) than those born in the winter. For BRD (48% incidence), calves born in the fall had higher odds of BRD (OR = 1.51; 95% CI: 1.12-2.04) compared with winter-born calves, whereas calves born in the summer had lower odds (OR = 0.67; 95% CI: 0.51-0.88). Additionally, calves with excellent TPI had lower odds of BRD compared with those with poor TPI (OR = 0.71; 95% CI: 0.52-0.98). The odds of LC (51% incidence) were lower in calves with good (OR = 0.56; 95% CI: 0.38-0.82) or excellent (OR = 0.41; 95% CI: 0.28-0.61) TPI compared with poor TPI. Summer-born calves also had lower odds of LC than winter-born calves (OR = 0.72; 95% CI: 0.51-1.00). Finally, each 1-kg increase in birth weight was associated with reduced odds of LC (OR = 0.96; 95% CI: 0.94-0.98). For mortality (3% incidence), calves born in the fall had lower odds (OR = 0.23; 95% CI: 0.05-0.97) of death compared with those born in the winter. Similarly, calves with good (OR = 0.13; 95% CI: 0.07-0.78) or excellent (OR = 0.34; 95% CI: 0.12-1.00) TPI status had reduced odds of mortality compared with those with poor TPI. In contrast, the odds of mortality were higher for calves with a health event compared with those with no health events (OR = 20.18; 95% CI: 4.24-96.13) and for calves with LC compared with those without LC (OR = 2.65; 95% CI: 1.02-6.88). These results identify some modifiable factors associated with preweaning calf health and survival and highlight the importance of improving colostrum management and early disease detection, as well as the influence of season.

An increasing proportion of calves entering the beef industry originate from dairy herds, representing a rapidly growing component of the global protein supply chain; however, best practices for their nutrition and health management remain poorly defined, particularly during early life. The objective of this narrative review is to provide a summary of current practices, challenges, and opportunities in the dairy-beef calf industry, with particular focus on the prefeedlot period. A lack of research and inconsistent policies across governing bodies has led to knowledge gaps regarding optimal management at the dairy farm of origin, including strategies for genetic decisions and colostrum management. Upon arrival at calf-rearing facilities and feedlots, clear guidance is lacking on optimal pre- and postweaning diets, implant and vaccination programs, and antimicrobial use. Dairy-beef calves undergo unique stressors that are not present in the traditional beef system, such as low levels of colostrum and milk, early weaning (∼2 mo of age compared with 5-9 mo), commingling, and transportation. As such, specific management strategies, including phase-feeding or nutritional interventions before or during transport, may help calves face these stressors. Therefore, for dairy-beef production to be sustainable, many of the health and welfare challenges will need to be overcome. For example, the current level of antimicrobial usage, where 61% to 87% of calves receive at least one antimicrobial during the preweaning period, and the duration and conditions of transportation are unsustainable. Addressing these challenges will enhance standard rearing practices and contribute to improved calf health, growth, and welfare of the industry. Thus, through targeted longitudinal research focusing on early life management of dairy-beef calves and the creation of recommended best practices, dairy-beef production may present a profitable and sustainable source of beef production.

Within the past decade, the use of beef semen in the dairy industry has risen, leading to a growing number of dairy × beef crossbred calves being born. However, limited studies compare the health and growth performance of purebred dairy and crossbred calves during the preweaning phase. This study aimed to evaluate the association of breed with morbidity, mortality, and growth performance during an 84-d rearing period. A total of 640 male calves were enrolled upon arrival to a calf-rearing facility and were classified as either Holstein (n = 446) or crossbred (n = 194), which were identified by hide color. Breed, source (local farm versus auction), and BW were recorded upon arrival. Calves were fed milk replacer (MR) twice daily until weaning, which occurred between d 42 and 63, and solid feed and water were offered ad libitum throughout the study. Health exams were performed twice daily, evaluating fecal consistency from arrival to d 21 and respiratory health from arrival to d 84. Mortalities and treatments administered, including electrolytes, nonsteroidal anti-inflammatory drugs, and antibiotics, were recorded throughout the study. Solid feed intake and BW were measured weekly following enrollment, and MR refusals were recorded daily. Statistical models, including Cox proportional hazards, Weibull, negative binomial, and linear regression, were built in Stata 18 (StataCorp LP) to assess the association of breed with calf health and growth. Holstein calves had a greater incidence of diarrhea compared with crossbred calves (incidence rate ratio = 1.23; 95% CI: 1.01-1.51) and a higher hazard of receiving a second (hazard ratio [HR] = 1.62; 95% CI: 1.04 to 2.51) or third (HR = 2.47; 95% CI: 1.24 to 4.91) treatment for respiratory disease. With respect to growth performance, crossbred calves had increased BW by d 28 and weighed 7.13 ± 1.31 kg (95% CI: 4.56 to 9.70) more than Holsteins by d 84. Similarly, ADG was greater for crossbreds starting between d 28 and 35. Feed-to-gain conversion ratios (FCR) were lower for crossbred calves during both the preweaning and weaning phases; however, Holstein calves had improved FCR between d 70 and 77 compared with crossbred calves. These results suggest that crossbred calves may be able to overcome illness quicker and with fewer therapeutic interventions than Holsteins in the rearing period while achieving superior growth performance.