The aim of this study was to describe the utility of Doppler ultrasonography of the milk vein (MV) to assess mammary plasma flow (MPF) and determine whether a relationship exists between MPF assessed via Doppler ultrasound of the MV (MPFMV) and the Fick principle (MPFFick) on the day of calving and at 7 DIM. A total of 11 parity 2 (P2) and 10 parity 3 (P3) Holstein cows were enrolled in the study immediately after calving. The MPFFick was estimated using the mammary arteriovenous difference of Phe and Tyr as internal markers at 2, 4, 6 and 8 h after colostrum collection and the morning milking at 7 ± 1 DIM. Milk was collected at milking 2 and the evening milking at 7 ± 1 DIM for determination of milk protein output. The MPFMV was also estimated by Doppler ultrasound of the left and right MV at 2 and 8 h after colostrum collection and the morning milking at 7 ± 1 DIM. Both MPFMV and MPFFick increased by 15.8 and 19.5% from calving to 7 DIM, respectively. No differences were detected between parity in MPFFick; however, P3 cows had greater MPFMV than P2 cows, as well as greater MV diameter. No relationship existed between MPFMV and MPFFick during the calving and fresh periods, which may have been due to the violation of multiple assumptions of the Fick principle as a result of the fluctuating rate of milk secretion, tissue metabolism, and blood flow associated with the onset of lactation. Although Doppler ultrasound of the MV may be a time-efficient, non-invasive technique to estimate fresh period MPF, further work is needed to validate its accuracy with techniques estimating MPF directly in the pudendal artery, such as the dye dilution technique. Such knowledge would allow for the widespread utilization of this non-invasive technique to uncover knowledge gaps pertaining to the relationship between fresh period mammary metabolism and milk production.

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.

This study aimed to evaluate the effects of maternal chromium propionate (CRP) supplementation during late gestation on cow-calf performance and skeletal muscle metabolism of neonatal calves. A total of 100 late gestation primiparous and multiparous Angus-Simmental cows (698.4 +/- 95.6 kg) were randomly assigned to one of two treatment groups: control (CTRL; n = 50), receiving a basal diet, or CRP (n = 50), receiving the same basal diet supplemented with 4 mg/head/day of CRP from day 223 of gestation until parturition (54.4 +/- 10.7 days). Cows were weighed, scanned via carcass ultrasound for body condition monitoring, and blood sampled every 28 days for glucose, insulin, beta-hydroxybutyrate (BHB), and non-esterified fatty acids (NEFA). At birth, calves were separated from their dams prior to nursing for blood collection, birth weight, and colostrum yield and samples from the dam. Samples from the longissimus dorsi muscle were biopsied from calves at six days of age for analysis of mRNA expression and protein abundance related to adipogenesis and glucose metabolism. Pre-partum dry matter intake did not differ between treatments (kg/d, P = 0.13; % of body weight, P = 0.29). A tendency for a treatment x calf sex interaction was detected for cow average daily gain (ADG; P = 0.08), where CRP cows carrying male calves tended to have lower ADG compared to CTRL cows of either calf sex. A treatment x days pre-partum (DPP) interaction was observed for levels of BHB (P > 0.01) with CTRL cows showing increased BHB at 11 DPP, while concentrations remained stable in CRP cows. In the biopsied skeletal muscle, calves born to CRP-supplemented dams exhibited greater mRNA expression of PPAR gamma (P < 0.01), ZFP423 (P < 0.01), DLK1 (P = 0.02), IRS1 (P = 0.01), and GLUT4 (P = 0.04), and tended to show greater protein abundance of IRS1 (P = 0.08) compared to calves born to CTRL cows. These findings suggest that supplementing CRP during late gestation modified dam energy status dependent on fetal sex and influenced the programming of the skeletal muscle metabolism in offspring.

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; MPFMV) 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 MPFMV 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 MPFMV and glc and acetate uptake was lowest from wk-6 to wk-4 relative to calving. Total MPFMV 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.

The objective of this study was to evaluate whether different metabolizable energy (ME) intakes would affect insulin responsiveness in late gestation beef cattle. Primiparous and multiparous cattle were fed rations that supplied 78% (LowME, n = 7 heifers and 12 cows) or 120% (HighME, n = 9 heifers and 10 cows) of predicted ME requirements from day -52 until calving, and then fed a common lactation ration. Body weight and rib and rump fat depth were measured every 2 wk prior to calving and on days 7, 13, 28, and 55 after calving. Plasma and serum were collected on day -3 and 7 relative to calving. Cattle underwent an intravenous glucose tolerance test (IVGTT) and a subcutaneous adipose biopsy on day -7 and -6, respectively. Prepartum body weight was similar (P = 0.62) for LowME and HighME cattle, but HighME cattle had greater (treatment by time: P = 0.01) rump fat depth than LowME at day -10 and -3 relative to calving. Overall, prepartum rib and rump fat depth tended to be greater (P = 0.07 and 0.06, respectively) for HighME vs. LowME. Glucose and insulin were similar (P ≥ 0.19) during the IVGTT and serum NEFA were elevated (P < 0.01) for LowME. The HighME NEFA decrement was lesser (treatment-time: P = 0.03) than that of LowME, indicating reduced insulin responsiveness. Adipocyte area tended to be larger (P = 0.05) for HighME. Antepartum glucose and cholesterol were greater (P < 0.04) and serum NEFA was lower (P < 0.01) for HighME vs. LowME. Postpartum albumin, glucose, and cholesterol were all increased (P ≤ 0.03) on day 7 after calving by feeding HighME before calving. Postpartum body weight was similar (P = 0.19) between treatments while rump fat depth was still less (P = 0.03) for LowME compared to HighME. The HighME cattle tended to have more (P = 0.06) rib fat depth postpartum. As such, HighME provision during late gestation improved markers of energy balance and was associated with modest reductions in antepartum insulin responsiveness, but this had few impacts after calving.

There is limited research investigating the impact of closeup nutrition on colostrum and transition milk (TM) production and composition in both primiparous (PP) and multiparous (MP) cattle, despite the potential of alterations in prepartum metabolism to modify the availability of substrates for colostrum and milk synthesis. The objective of this study was to determine the effect of altering closeup dietary NDF content on colostrum, transition and mature milk composition and to characterize potential associations between cow and metabolic factors and colostrum yield and composition. Primiparous heifers were blocked by expected calving date and genetic parent average for milk yield and MP cows were blocked by parity, expected calving date, completed 305-d average milk yield and body condition score (BCS) at dry-off. From d -57 ± 5.8 before expected calving, PP (n = 20) and MP (n = 28) cattle were fed a high NDF diet (HI; 55.7% DM basis; 2.37 Mcal ME/kg DM). From d -19 ± 4.0, cattle were randomly assigned within block to a close-up diet (CUD) to either remain on HI or move to a low NDF diet (LO; 40.6% DM basis; 2.48 Mcal ME/kg DM). Blood samples were collected at wk -4, -3, -2, -1, at calving (within 12 h), and at d +4, +7, +14 and +21 relative to calving. Colostrum (milking [M] 1) was collected within 8 h of calving, followed by TM (M2 to M7) and mature milk (d 16 ± 2.0, wk +2), and total yield (kg) was measured at each milking. Component (fat, protein, lactose, TS, MUN, SCC, BHB), insulin, and immunoglobulin G (IgG) concentrations were analyzed by Fourier-Transform Infrared spectroscopy, ELISA, and radial immunodiffusion, respectively, and multiplied by milk yield at each respective milking to determine component (g), insulin (μg) and IgG (g) yields. Feeding LO had no effect on colostrum yield, component concentrations and yields, and IgG content and yield. However, cows fed LO had greater colostrum insulin concentration and yield, albeit this difference only existed between LO-MP and HI-MP cows and not between LO-PP and HI-PP heifers. The LO cows tended to have greater colostrum SCC than HI cows; yet, no differences were observed between parity with CUD. Interestingly, correlation analyses demonstrated that colostrum production was differentially associated with serum metabolites and hormones in PP heifers and MP cows. In terms of milk production, LO-MP cows produced greater transition and mature milk yields and component yields than HI-MP cows. In contrast, no differences existed between LO-PP and HI-PP heifers. In summary, the results suggest that colostral insulin levels and SCC are responsive to alterations in closeup NDF content. Further, providing low compared with high NDF diets during closeup improved transition and mature milk production in MP, but not PP, cattle, emphasizing the need for future research investigating the underlying differential metabolic and production responses to closeup dietary NDF content between parity groups.

The objective of this study was to evaluate the effects of varying levels of maternal metabolizable energy (ME) intake during late gestation on the changes in postnatal development of skeletal muscle in calves. A total of 42 primiparous (n = 21) and multiparous (n = 21) pregnant Angus-Simmental beef cows (680.8 ± 74.4 kg) were housed indoors at the Ontario Beef Research Center at the University of Guelph. Cows were blocked by predicted calving date, balanced by initial body weight and parity, and randomly assigned to one of 3 treatment diets designed to provide 92% (LME, n = 16), 104% (CME, n = 13), or 118% (HME, n = 13) of predicted ME requirements, based on a 715 kg Angus cow with body condition score (BCS) 7 programmed to lose 2 BCS units over late gestation. All cows were managed under a planned moderate negative energy balance starting 53 d before expected calving. At birth, calves were weighed before suckling the dam, and again on day 209 at weaning. At 28 d of age, plasma and serum samples were collected for insulin, glucose, BHBA, and non-esterified fatty acids analysis. At 30 d of age Longissimus muscle samples were biopsied from the calves and were used for mRNA expression and protein abundance for energy metabolism. All statistical analyses were performed in SAS Studio, in a mixed model including the fixed effects of treatment and parity, and the random effect of sire. No differences were observed among treatments for calf birth weight, weaning weight, and metabolic profile. A lower mRNA expression of MYH1 was observed (P = 0.02) in the skeletal muscle of calves from the HME and LME groups compared to the CME. An increased mRNA expression of both MYH2a (P = 0.04) and MYH2 × (P = 0.01) was observed in calves from LME compared to HME, suggesting potential alterations in muscle fiber composition that may influence metabolic efficiency and growth performance. A greater mRNA expression of PPARα (P = 0.04), PPARGC1α (P = 0.04), and MEF2A (P = 0.01) were observed in calves from the LME group compared to the HME. A greater AMPK activity was observed (P = 0.01) in the skeletal muscle of calves from the LME group compared to CME and HME. In contrast, Akt activity was greater in HME and LME groups compared to CME (P = 0.01). Our findings suggest that maternal ME intake affected the muscle energy metabolism of the offspring, the oxidation of fatty acids, mitochondrial biogenesis, and the use of muscle fiber-type fuel.

The objective of this study was to evaluate the effects of feeding milk replacer (MR) at different lactose amount while keeping osmolality constant on gastrointestinal function, blood parameters, and inflammation-related mRNA expression in the livers of dairy calves. Fifteen Holstein bull calves were assigned to one of three dietary treatments differing in MR lactose content (L: 38 %, M: 41 %, and H: 46 %). Feeding of the test diets was started at 1 day of age and gradually increased to a maximum feeding rate at 20 days of age (L: 1.16 kg/d, M: 1.21 kg/d, and H: 1.26 kg/d DM). Under these conditions, the lactose dosages for the treatments were 441 g/d, 496 g/d, and 580 g/d, respectively. The MR were prepared to ensure isocaloric and iso-osmotic (451 mOsm/kg) conditions. Fecal scores were recorded daily, and at 14 and 28 days of age, blood and breath samples were collected before and after MR feeding. In addition, feces and urine were collected for 2 consecutive days. Then, the calves were slaughtered to evaluate intestinal permeability and liver mRNA expression. The permeability in the duodenum and ileum was lower in H and M than in L; the permeability in the jejunum was also lower in H than in L. The hepatic mRNA expressions of toll-like receptor-2, IL-1 beta, and tumor-necrosis factor-alpha were lower in H and M than L. Nitrogen retention was higher in H than in L, and linear and quadratic increasing trends were observed in tissue ratio of gastrointestinal tract with the increase in lactose amount. Postprandial increase in plasma glucose concentration was smaller and postprandial increase in TG concentration was higher in H than in L. Fecal properties, digestibility, and breath hydrogen concentrations were not affected by treatment. These results indicate that feeding high-lactose MR may increase gastrointestinal weight and decrease permeability in the small intestine of calves.

The primary objective of the study was to characterize concentrations and yields of lactoferrin (LF), insulin, and IGF-I in colostrum, transition milk (TM), and whole milk (WM) of multiparous (MP) and primiparous (PP) cows. A secondary objective was to determine associations between colostrum and TM components (fat, protein, lactose), IgG and bioactive compounds (oligosaccharides, LF, insulin, IGF-I; defined as compounds present in micro quantities that stimulate physiological responses systemically or locally within the neonate). Holstein cows (10 MP and 10 PP) were assigned to the study at calving and colostrum was collected 5.3 ± 0.7 h after calving, followed by twice daily sampling of milkings 2–5 (TM) and milking 12 (WM). Colostrum, TM, and WM samples were analyzed by commercial ELISA to determine concentrations of LF, insulin, and IGF-I. Concentrations of insulin, IGF-I and LF were greatest in colostrum compared with all other milkings. Similarly, IGF-I and LF yields were greatest in colostrum, while insulin yield was greatest in colostrum and milking 2 compared with milking 4, 5 and 12. Specifically, insulin, IGF-I and LF yields were 36.3, 14.7 and 2.3 × greater in colostrum compared with WM, respectively. Primiparous cows had greater insulin and lower LF concentrations in colostrum compared with MP cows. Additionally, lower LF concentrations in PP cows compared with MP cows persisted through milkings 2 and 3. The majority of associations between components and bioactive compounds in colostrum were positive; however, correlations were different between PP and MP cows. Specifically, there were a greater number of strong (ρ > 0.80) correlations between components and IgG in PP cows. In contrast, MP cows demonstrated a greater number of strong correlations among bioactive compounds, as well as between components and total oligosaccharides. To the author's knowledge, this study is the first to characterize the yields of IGF-I, LF, and insulin during the colostral (collection within 6 h) and TM period in both MP and PP cows. The study findings indicate that colostrum contains higher levels of bioactive peptides compared with WM and that parity influences the levels of LF and insulin, but not IGF-I. Our study also uniquely demonstrates associations between early lactation components and bioactive compounds, which are not consistent among parities.

There is a lack of knowledge available on how cats adjust their macronutrient partitioning due to the consumption of single-macronutrient meals. The objective of this study was to evaluate consumption of a single meal of ingredients that contained foods of strictly carbohydrates (CHO), fat (FAT) or protein (PRO), on energy expenditure (EE) and macronutrient metabolism in cats. Ten domestic shorthair adult cats (1·9 years; 4·12 kg) were fed 22–24 g of chicken fat (FAT), 56–62 g of whey protein solution (PRO) or 54–56 g of cornstarch solution (CHO) for a single day in a randomised complete block design. Indirect calorimetry was conducted for 24 h post-feeding. Mean average EE over 24 h was highest in cats fed PRO (44 kcal/kg BW) and FAT (43 kcal/kg BW) compared with that in cats fed CHO (42 kcal/kg BW; P < 0·01). During 0 to 4 h, cats fed FAT had greater EE (49 kcal/kg BW), suggesting that cats respond to oxidising more dietary fat over protein in the early postprandial stage. Mean 24 h respiratory quotient (RQ) was greatest for cats fed CHO (0·76) followed by PRO (0·75) and FAT (0·74; P < 0·05). During 4 to 8 h, the RQ of cats fed PRO was the greatest (0·77), suggesting that cats initially increase gluconeogenesis from amino acids for subsequent glucose oxidation. In comparison to omnivores and herbivores, obligate carnivores have unique responses to single macronutrient intake, where they apparently generate energy from carbohydrate metabolism and rely more on gluconeogenic precursors.

Early colostrum feeding facilitates the passive transfer of immunoglobulin G (IgG), which contributes to the defensive establishment of neonates; however, the molecular mechanisms of IgG absorption in the small intestine of neonatal mammals remain largely unknown. In this study, a total of 16 neonatal goat kids with similar body weight (2.05 ± 0.31 kg) were selected and randomly assigned to 1 of 2 feeding treatments: normal colostrum feeding (NCF, n = 8) or delayed colostrum feeding (DCF, n = 8). Multi-omics coupled with individual bioinformatics analyses were employed to obtain a comprehensive understanding of the molecular mechanisms of IgG absorption. Phenotypic analysis showed that the capacity of IgG absorption was largely affected (P < 0.05) by colostrum feeding time in neonatal goat kids. Weighted gene co-expression network analysis generated 23 gene modules (gene module defined M1 to M23) and the M12 module was highly correlated (|r| > 0.70 and adjusted P < 0.01) with IgG absorption. Genes in M12 were involved in the endocytosis pathway, especially related to clathrin-mediated endocytosis and macropinocytosis. The differentially expressed genes (DEGs) enriched in the above-mentioned pathways regulated the clathrin synthesis (CLTC), the formation of clathrin-coated vesicles (ARPC1A), and the sorting and recycling endosomes (CAPZA2, KIAA0196, RAB10, RAB11A and VPS35) as well as the formation of macropinosomes (FGFR4 and RhoA) in micropinocytosis, which induced differences in serum IgG concentrations. Additionally, 5 differentially expressed miRNAs (miR-2755-3p, miR-10400-5p, miR-71-5p, miR-2944-3p and miR-2411-3p) were predicted to regulate mRNA involved in clathrin-coated vesicles, Fc receptor for IgG (FcRn)-IgG sorting, and macropinosomes formation that may cause the difference in IgG absorption ability. This study provides new insights into the molecular mechanisms controlling IgG absorption of neonatal ruminants and reveals novel mRNA and miRNA markers involved in clathrin-mediated endocytosis and macropinocytosis which may provide the fundamental knowledge related to IgG absorption to support further study in other mammals.

Gut health is a critical determinant of overall performance, disease resistance, and productivity in calves and cows. The gastrointestinal epithelium is tasked with nutrient absorption while maintaining a barrier against harmful luminal contents, making it a highly metabolically active and organ system. In fact, the gastrointestinal tract (GIT), accounts for up to 20% of total oxygen consumption in ruminants, highlighting its substantial energy demand. Key developmental transitions—such as birth, weaning, and the onset of lactation—require major structural and functional adaptations in both the upper and lower GIT. These transitions, however, also expose animals to periods of physiological stress and compromised gut barrier function. In calves, the preweaning period presents a high risk for gastrointestinal disorders and diseases, often exacerbated by microbial and gut barrier dysfunction. Weaning introduces significant stress as the digestive system shifts from milk-based to solid diets, often leading to transient inflammation, altered microbiota, and increased gut permeability, particularly in the lower gut. In adult cows, the transition to highly fermentable, energy-dense diets during early lactation poses another critical challenge. This abrupt dietary shift can disrupt ruminal and intestinal integrity, leading to ruminal acidosis and systemic inflammation via translocation of microbial endotoxins. Nutrients, microbial metabolites, such as butyrate, and gut hormones, including glucagon-like peptide 2 and insulin-like growth factor, play vital roles in stimulating epithelial growth and repair. Understanding how these factors interact to influence gut proliferation and barrier function is crucial, especially when balanced against the energetic cost of gut tissue expansion. Ultimately, optimizing gut development and resilience during key life stages holds promise for improving health, feed efficiency, and lifetime productivity in cattle.

The objective of this case-control study was to assess gut permeability, measured through Cr-EDTA recovery, in healthy and diarrheic neonatal calves. The study was conducted at a commercial calf-rearing facility, where fecal consistency was monitored twice daily. Calves were categorized as diarrheic if they had runny or watery feces, whereas those with normal fecal consistency, neutrophil count, and physical exam findings were considered healthy controls. Gut permeability assessment (Cr-EDTA: 0.1 g/kg BW administered orally 2 h after milk feeding) and blood bacterial culture were performed 24 h after onset of diarrhea. Plasma Cr concentration was determined using inductively coupled plasma mass spectrometry. Wilcoxon signed-rank test and Kruskal-Wallis tests, followed by Dunn's post hoc test, were used to compare Cr concentrations between groups. The study included 12 healthy calves and 11 diarrheic calves, with 5 diarrheic calves having bacteremia. Diarrheic calves had greater median (interquartile range) plasma Cr concentrations than healthy calves at 2 h (1.76 [0.92–2.34] mg/L vs. 0.59 [0.48–1.19] mg/L) and 4 h (2.07 [1.57–2.51] mg/L vs. 0.92 [0.77–1.66] mg/L) postadministration, respectively. Both bacteremic and nonbacteremic calves with diarrhea had greater plasma Cr concentrations at 2 h compared with healthy calves (bacteremic: 1.96 [1.76–2.03] mg/L; nonbacteremic: 1.42 [0.78–2.34] mg/L), but there was no difference between bacteremic and nonbacteremic calves. At 4 h postadministration, both bacteremic (2.00 [1.67–2.07] mg/L) and nonbacteremic (2.45 [1.57–3.66] mg/L) diarrheic calves had greater plasma Cr concentrations than healthy calves, with no difference observed between bacteremic and nonbacteremic groups. This study suggests an association between diarrhea and increased gut permeability in neonatal calves. Further studies are required to compare gut permeability in a larger cohort of bacteremic and nonbacteremic diarrheic neonatal calves.

This study evaluated the effects of an oral probiotic capsule containing a live culture of Megasphaera elsdenii NCIMB 41125 on performance, feeding behavior, rumen pH and VFA concentration, and development of dairy-beef crossbred calves. Thirty-one male dairy-beef crossbred calves (Holstein x Angus; mean +/- SD; 45.3 +/- 7.1 kg; 8.2 +/- 2.0 d old) were enrolled in a blinded, 76-d randomized trial. Calves were randomly assigned to one of 3 treatments: placebo, probiotic capsule administration on d 15, or probiotic capsule on d 15 plus a second capsule on d 39 of the study. Calves were housed individually with ad libitum access to water and calf starter and were fed 7 L/d of milk replacer (1,050 g of powder/d) in 2 meals until d 41, then 3.5 L/d in 2 meals until weaning on d 56. Behavioral observations were recorded in 1-min intervals using a wall-mounted camera. Rumen fluid samples were collected on d 14, 35, 49, 58, and 70, and analyzed for pH and VFA. Upon euthanasia on d 77, forestomach weights were recorded and rumen papillae dimensions were measured. Mixed linear models were used for statistical analysis. Probiotic treatment resulted in greater daily solid feed DMI and ADG, particularly during weaning and postweaning periods. Additionally, probiotic-treated calves spent more time drinking water and tended to have lower rumen pH compared with control calves. Empty rumen weight and papillae area were greater in calves supplemented with the probiotic capsule on d 15 compared with the other treatments. These findings suggest that preweaning M. elsdenii supplementation enhances performance and rumen development in dairy-beef crossbred calves. However, the effects of timing and number of capsule applications on rumen development and calf performance should be further investigated. Further research should also investigate the probiotic's effect on the rumen microbiome and fermentation dynamics throughout the rearing period using detailed microbiome analysis.

The number of crossbred dairy calves has drastically increased over the past decade, but pre-feedlot nutritional recommendations remain scarce. This study investigated the interaction between pre- and post-weaning diets with different energy substrate inclusions. Male Holstein-Angus calves (n = 68) were assigned at 1 wk of age to 1 of 4 treatments in a 2 × 2 factorial arrangement: fat milk replacer (MR) + control grower diet (FC); fat MR + fat grower diet (FF); lactose MR + fat grower diet (LF); and lactose MR + control grower diet (LC). Fat and lactose MR were 29% and 18% fat, and 38% and 51% lactose (DM), respectively. Mixing rate for fat and lactose MR were 135 and 150 g/l, respectively to balance energy and protein supply. Milk replacer was fed at 15% of arrival body weight (BW) until wk 3 and 18% thereafter until wk 6. Gradual weaning occurred from wk 6 to 10, with grower diets introduced at wk 5 and fed until the end of the growing phase (wk 36). Fat and control grower diets were 7% and 3% crude fat (DM), respectively. At wk 13, calves were transported to a feedlot for the remainder of the experiment. Milk and solid feed intake were recorded daily, and BW was collected weekly. Starting on wk 16, measurements of the ribeye area (REA), back and rump fat thickness, and intramuscular fat (IMF) percentage were taken monthly using ultrasound on the Longissimus dorsi muscle. Analysis of variance was conducted using treatment and calf nested in block as fixed and random effects, respectively. Milk composition had no effect on BW or average daily gain (ADG), though calves fed fat MR had greater milk intake for the first 2 wks (P = 0.01). Calves fed the control grower diet had increased solid feed intake (P = 0.02) and tended to have greater ADG (P = 0.10), leading to a greater BW at wk 36 of age and a larger REA (P = 0.05) compared to calves fed the fat grower diet. Rump fat depots tended to be higher in calves fed the high lactose MR (P = 0.06) and the control grower (P = 0.07), whereas IMF was greater in LC-fed calves compared to FC-fed calves (P = 0.05). Overall, calves fed the fat grower diet had higher feed efficiency (kg DMI / kg BW gain) than calves fed the control grower (P < 0.01). Milk replacer composition had limited effects on growth when fed at isocaloric and isonitrogenous levels. However, growth, body composition and feed efficiency were affected by the type of energy substrate in the grower diet. Whether these differences persist in the finishing phase remains to be addressed.

Late gestation marks the prominent period for fetal muscle development in-utero, pre-dispositioning offspring muscle development, and carcass value. Adequate glucose metabolism facilitates muscle fibers formation, although it can be compromised by maternal energy imbalances. Nutritional strategies such as supplementation of organic chromium propionate, in late gestation, aim to enhance insulin sensitivity and glucose metabolism, potentially improving maternal energy balance to promote efficient glucose uptake for fetal muscle development. However, this relationship between chromium and glucose in this stage of gestation is yet to be fully understood. This study aimed to evaluate the effects of maternal chromium propionate supplementation and the impacts on the growth and muscle metabolism in the offspring. One hundred late-gestation Angus-cross beef cows were randomly assigned to two treatments until parturition: control (CON, n = 50), receiving a basal diet, and chromium propionate (CRP, n = 50), receiving the same diet supplemented with 10 g/head/day of KemTRACE® Chromium 0.04% (Kemin Industries, Inc., Des Moines, IA). Cow performance was monitored from 56 days prepartum to parturition, and calf metabolic parameters were assessed at birth. From 2-10 days of age, skeletal muscle samples were collected from calves to assess gene expression and protein abundance related to adipogenesis and glucose metabolism. Maternal CRP-supplementation had no impact (P > 0.05) on calf birth weight, weaning weight, or average daily gain from birth to weaning. A treatment by calf sex interaction was observed for the number of muscle fibers, where CRP-supplemented male calves exhibited a greater number (P = 0.01) of muscle fibers compared to CON male calves. However, no significant differences were observed for muscle fiber size (P = 0.53) or muscle fiber type (P > 0.05) between dietary treatments or calf sex. Calves from CRP-supplemented dams showed increased skeletal muscle mRNA expression of adipogenic markers PPARγ (P < 0.01), ZFP423 (P < 0.01), and DLK1 (P = 0.02). Similarly, they exhibited enhanced mRNA expression of IRS1 (P = 0.01) and GLUT4 (P = 0.04) and tended to increase the IRS1 activity (P = 0.08). In summary, these findings suggest maternal supplementation with chromium propionate at late gestation affects the skeletal muscle development of the offspring likely enhancing the early intramuscular adipogenesis and glucose uptake capacity, increasing their potential for intramuscular fat deposition.

The objectives of this cross-sectional study were to identify barriers to veterinary involvement in calf health and assess knowledge gaps in calf care among American and Canadian bovine veterinarians. A questionnaire was administered to veterinarians, collecting data on demographics, satisfaction with calf health management knowledge, involvement in decision-making, satisfaction with calf health involvement, frequency of calf health record analysis and feedback, topics of interest for further learning, and preferred learning formats. Multivariable logistic regression models were used to assess associations between variables and outcomes. Only 28% of veterinarians frequently reviewed calf health records, and 44% made actionable recommendations after reviewing them. Female veterinarians were more likely than male veterinarians to frequently review calf health records (Odds ratio – OR: 2.9, 95% CI: 1.2–7.3). Additionally, the odds of frequently reviewing records increased with the amount of time spent working with calves (OR: 10.2 per 10% increment, 95% CI: 10.0–10.5). Veterinarians highly satisfied with their knowledge of neonatal calf diarrhea (NCD) prevention were more likely to make recommendations based on records (OR: 11.6, 95% CI: 1.9–72.4). Additionally, those frequently reviewing records were more likely to provide feedback (OR: 15.5, 95% CI: 4.0–60.3). Incomplete records was the most common reason for not reviewing records (60% of respondents) and why actionable recommendations were made less frequently than “most of the time” (67% of respondents). Veterinarians were least confident in their knowledge regarding milk feeding and weaning recommendations but they were interested in learning more about post-weaning nutrition and automated calf feeders. Further, they preferred conference presentations for continuing education. These findings suggest that veterinary involvement in calf health could be improved by facilitating better data capture and enhancing veterinarian knowledge.

The gastrointestinal microbial consortium in dairy cattle is critical to determining the energetic status of the dairy cow from birth through her final lactation. The ruminant's microbial community can degrade a wide variety of feedstuffs, which can affect growth, as well as production rate and efficiency on the farm, but can also affect food safety, animal health, and environmental impacts of dairy production. Gut microbial diversity and density are powerful tools that can be harnessed to benefit both producers and consumers. The incentives in the United States to develop Alternatives to Antibiotics for use in food-animal production have been largely driven by the Veterinary Feed Directive and have led to an increased use of probiotic approaches to alter the gastrointestinal microbial community composition, resulting in improved heifer growth, milk production and efficiency, and animal health. However, the efficacy of direct-fed microbials or probiotics in dairy cattle has been highly variable due to specific microbial ecological factors within the host gut and its native microflora. Interactions (both synergistic and antagonistic) between the microbial ecosystem and the host animal physiology (including epithelial cells, immune system, hormones, enzyme activities, and epigenetics) are critical to understanding why some probiotics work but others do not. Increasing availability of next -generation sequencing approaches provides novel insights into how probiotic approaches change the microbial community composition in the gut that can potentially affect animal health (e.g., diarrhea or scours, gut integrity, foodborne pathogens), as well as animal performance (e.g., growth, reproduction, productivity) and fermentation parameters (e.g., pH, short-chain fatty acids, methane production, and microbial profiles) of cattle. However, it remains clear dairy of lactation. a as but envithat all direct-fed microbials are not created equal and their efficacy remains highly variable and dependent on stage of production and farm environment. Collectively, data have demonstrated that probiotic effects are not limited to the simple mechanisms that have been traditionally hypothesized, but instead are part of a complex cascade of microbial ecological and host animal physiological effects that ultimately impact dairy production and profitability.

Even with the same energy supply, differences in energy sources may affect calf growth and metabolism. In this study, we evaluated the effects of feeding 3 different milk replacers (MR) with different lactose supplies under isoenergetic conditions on calf digestibility, growth, and metabolism-related markers. Fifteen Holstein bull calves were randomly assigned to one of 3 MR feeding treatments: low lactose (L: 38%), medium lactose (M: 41%), or high lactose (H: 46%). After birth, calves were provided colostrum, and treatment MR were fed from 1 d of age and gradually increased to a maximum feeding rate at 20 d of age (L: 1.16 kg/d, M: 1.21 kg/d, H: 1.26 kg/d DM) without feeding solid feeds during the experimental period. Blood samples were temporarily collected weekly to assess blood concentrations of metabolites and hormones. From 30 to 36 d of age, the calves were euthanized and liver samples were collected to determine growth-related mRNA expression. The L calves showed a greater body length than H calves and the highest growth hormone receptor (GHR) mRNA expression. Plasma concentrations of total cholesterol, urea nitrogen, total protein, albumin, insulin, and IGF-1 were not different, but plasma concentrations of triglycerides were greater in order H, M, and L. These results showed that the difference in lactose content in the MR affected calf metabolism, and the L-MR was suggested to be more likely to enhance growth into the peripheral tissues.