Feeding heat-treated colostrum or unheated colostrum with two different bacterial concentrations to neonatal dairy calves

The objective of this study was to determine the effects of feeding heat-treated colostrum or unheated colostrum of different bacterial counts on passive transfer of immunity in neonatal dairy calves. First milking colostrum was collected from Holstein cows, frozen at -20°C, and then thawed and pooled into a single batch. One-third of the pooled colostrum was transferred into plastic containers and frozen at -20°C until needed for feeding (unheated-low bacteria). Another third was heat-treated at 60°C for 30 min and then frozen at -20°C until needed for feeding (heat-treated). The final third of colostrum was transferred into plastic containers, stored at 20°C for bacteria to grow for 24 h (unheated-high bacteria), and then frozen at -20°C until needed for feeding. A total of 30 Holstein bull calves weighing ≥30 kg at birth were systematically enrolled into 1 of the 3 treatment groups. Calves were separated from their dams at birth before suckling occurred. Before colostrum was fed, a jugular blood sample was collected from each calf. The first feeding consisted of 3.8 L of colostrum containing, on average, 68 g of IgG/L using an esophageal feeder between 1.5 and 2 h after birth. For the second and third feeding pasteurized whole milk at 5% of birth weight was fed. Blood samples were collected before colostrum feeding and at 24 and 48 h of age to determine serum total protein (STP) and IgG concentrations. Heat treatment of colostrum at 60°C for 30 min reduced colostrum bacteria concentration yet maintained colostral IgG concentration and viscosity at similar levels to the control treatment. Calves fed heat-treated colostrum had significantly greater STP and IgG concentrations at 24 h and greater apparent efficiency of absorption (AEA) of IgG (STP = 62.5 g/L; IgG = 26.7 g/L; AEA = 43.9%) compared with calves fed unheated-low bacteria colostrum (STP = 57.0 g/L; IgG = 20.2 g/L; AEA = 35.4%) or unheated-high bacteria colostrum (STP = 56.2 g/L; IgG = 20.1 g/L; AEA = 32.4%). High bacteria load in colostrum did not interfere with total protein or IgG absorption or AEA.     

Short communication: The effect of delayed colostrum feeding on plasma concentrations of glucagon-like peptide 1 and 2 in newborn calves

Glucagon-like peptide (GLP)-1 is involved in glucose homeostasis via its role in stimulating insulin secretion, whereas GLP-2 increases mucosal growth of the small intestine. To our knowledge, the effect of delayed colostrum feeding on plasma GLP-1 and GLP-2 in neonatal calves has not been evaluated. To investigate the effect of delayed colostrum feeding on plasma concentrations of GLP-1 and GLP-2 in newborn calves, we randomly assigned 27 Holstein bull calves to 1 of 3 treatment groups: those fed colostrum within 1 h after birth (control), 6 h after birth (6H), and 12 h after birth (12H; n = 9 for each treatment). Blood samples were obtained before the colostrum feeding and every 3 h after each colostrum feeding for a 36-h period, and plasma concentrations of GLP-1, GLP-2, insulin, and glucose were measured. Plasma GLP-1 concentration at 12 h after colostrum feeding was lower in 12H than in control calves. In addition, plasma insulin concentration was lower in the 6H and 12H calves than in the controls. Plasma glucose and GLP-2 concentrations were, however, not affected by treatment. These results indicate that delayed colostrum feeding can decrease plasma GLP-1 and insulin concentrations without affecting glucose or GLP-2 concentration.     

Effect of extended colostrum feeding on plasma glucagon-like peptide-1 concentration in newborn calves

Glucagon-like peptide-1 (GLP-1) plays a role in the regulation of glucose homeostasis via the stimulation of insulin secretion. The objective of this study was to evaluate the effect of extended colostrum feeding on plasma concentration of GLP-1. Holstein bull calves (n = 27) were fed pooled colostrum at 7.5% of birth body weight at 2 h after birth and then fed mature milk (M), a 50:50 mixture of pooled colostrum and milk (CM), or pooled colostrum (C; n = 9 for each treatment) at 5% of birth body weight at 12 h after birth and every 12 h thereafter until 72 h after birth. Blood samples were obtained before (1 and 2 h after birth) and after (until 72 h after birth; 42 time points) the first colostrum feeding, and plasma concentrations of glucose, insulin, and GLP-1 were measured. Data were analyzed by ANOVA of JMP 13 (SAS Institute Inc., Cary, NC) with treatment, time, and treatment × time interaction as fixed effects. Treatment × time interaction was observed for plasma insulin and glucose concentrations, which were mainly the result of lower concentrations from 1 to 2 d after birth for C compared with M. Conversely, on d 3 after birth, the difference between treatments was not observed for insulin and glucose. For the entire experimental period, plasma GLP-1 concentration was higher for C (2.25 ng/mL) compared with M (1.41 ng/mL) and tended to be higher compared with CM (1.58 ng/mL). A treatment × time interaction was observed for GLP-1, but unlike glucose and insulin, this was mainly the result of higher concentrations from 54 to 72 h after birth (on d 3 after birth) for C compared with M or CM. Postprandial plasma concentration of glucose was not correlated with that of GLP-1 but was positively correlated with that of insulin for the 4-h period after feeding on d 1 (r = 0.30) and d 3 after birth (r = 0.33). Postprandial plasma concentration of GLP-1 was positively correlated with that of insulin for the 4-h period after feeding on d 3 after birth (r = 0.20). These results indicate that extended colostrum feeding may increase plasma GLP-1 concentrations, especially 3 d after birth, but further study is necessary to determine the effect on plasma insulin and glucose concentrations.     

Effects of feeding heat-treated colostrum on passive transfer of immune and nutritional parameters in neonatal dairy calves

The first objective of this study was to describe the effect of on-farm heat treatment of colostrum on colostral bacteria counts and IgG concentrations. The second objective was to describe the effect of feeding heat-treated (vs. raw) colostrum on passive transfer of colostral immune and nutritional parameters in neonatal calves. Pooled batches of colostrum were mixed and divided equally: one half was fed raw whereas the other half was fed after heat treatment at 60°C for 60 min using a commercial on-farm batch pasteurizer. Colostrum samples were cultured for total bacteria count and total coliform count and analyzed for total IgG concentration. Forty-nine Holstein calves were fed either raw colostrum (n = 24) or heat-treated colostrums (n = 25) within 1 to 2 h after birth. Serum samples collected from calves at 0 h (precolostrum) and 24 h (postcolostrum) were assayed for serum total protein; IgG, IgA, and IgM concentrations; peripheral total leukocyte counts; neutrophil counts; lymphocyte counts; lymphocyte phenotypes; vitamin A, vitamin E, cholesterol, and β-carotene concentrations. Serum samples collected from 2- to 5-d-old calves were tested for immunoglobulin function via a bovine viral diarrhea virus type I serum neutralization titer and for neutrophil bacterial opsonization activity. On-farm batch heat treatment of colostrum at 60°C for 60 min resulted in lower colostrum bacteria concentrations while maintaining colostral IgG concentration. Calves fed heat-treated colostrum had significantly greater serum total protein and IgG concentrations at 24 h, plus greater apparent efficiency of IgG absorption (total protein = 6.3 mg/dL; IgG = 22.3 mg/mL; apparent efficiency of absorption = 35.6%) compared with calves fed raw colostrum (TP = 5.9 mg/dL; IgG = 18.1 mg/mL; apparent efficiency of absorption = 26.1%). There was no effect of treatment on serum concentrations of IgA, IgM, vitamin A, vitamin E, cholesterol, β-carotene or vitamin E:cholesterol ratio, or on serum bovine viral diarrhea virus type I serum neutralization titers. There was no difference between treatment groups when examining calf plasma total leukocyte counts, neutrophil counts, lymphocyte counts, or neutrophil opsonization activity. However, the latter results were considered inconclusive.     

The effect of tube versus bottle feeding colostrum on immunoglobulin G absorption,abomasal emptying,and plasma hormone concentrations in newborn calves

The objective of this study was to determine if feeding colostrum to newborn calves through an esophageal tube, compared with a nipple bottle, would delay abomasal emptying, which would in turn decrease passive transfer of IgG and plasma glucose, insulin, and glucagon-like peptide (GLP) 1 and GLP-2 concentrations. Twenty newborn Holstein bull calves were fed 3 L of colostrum replacer (200 g of IgG) through either an esophageal tube or nipple bottle at 2 h after birth followed by feeding pooled whole milk every 12 h after birth. Acetaminophen was mixed into the colostrum meal as a marker for abomasal emptying. A jugular catheter was inserted 1 h after birth and blood was sampled frequently to analyze serum for IgG and acetaminophen and plasma for glucose, insulin, GLP-1, and GLP-2. Feeding method did not affect abomasal emptying, and as a result no treatment effect was present on serum IgG concentrations. Maximum concentration of serum IgG was 24.4 ± 0.40 mg/mL (± standard error), which was reached at 14.6 ± 1.88 h after the colostrum meal for both groups. Apparent efficiency of absorption at maximum concentration of IgG was 52.9%, indicating high efficiency of passive transfer of IgG for both treatments. Tube feeding increased glucose and insulin area under the curve before the first milk meal, most likely due to the decreased time to consume the colostrum meal. In addition, tube-fed calves consumed 0.5 ± 0.13 L more milk in their first milk meal than bottle-fed calves. No treatment effect on plasma concentrations of GLP-1 or GLP-2 was present, but both hormones increased after colostrum feeding. These findings confirm that there is no effect on absorption of IgG from colostrum when feeding good-quality colostrum at a volume of 3 L through either an esophageal tube or nipple bottle.     

Altered mucosa-associated microbiota in the ileum and colon of neonatal calves in response to delayed first colostrum feeding

The present study investigated whether delaying the first feeding of colostrum affected ileum and colon mucosa-associated microbiota in calves. Twenty-seven male Holstein calves were randomly assigned to 1 of 3 groups, fed colostrum at 45 min, 6 h, and 12 h after birth, respectively. Ileum and colon mucosa were collected at 51 h after birth, and their associated microbial profiles were assessed using amplicon sequencing. Both ileum and colon mucosa-associated microbiota were predominated by genus Escherichia-Shigella. The negative correlation between the molar proportion of short-chain fatty acids (SCFA) and ileum mucosa-associated opportunistic pathogens, and the positive correlation between the molar proportion of SCFA and colon mucosa-associated beneficial bacteria, suggest that SCFA might play an important role in maintaining the gut health of 2-d-old calves. A higher relative abundance of ileum mucosa-associated Enterococcus and Streptococcus was detected when the first colostrum feeding was delayed for 12 h. The relative abundance of colon mucosa-associated Lactobacillus tended to be lower in calves fed colostrum 12 h than those under the other 2 treatments, whereas that of Faecalibacterium tended to be lower in calves fed colostrum immediately after birth than those fed colostrum 6 and 12 h after birth, respectively. Our findings suggest that delayed first colostrum feeding affects the establishment of ileum and colon mucosa-associated bacteria, which may have long-term effects on gut health of calves.     

Formulation of colostrum supplements, colostrum replacers and acquisition of passive immunity in neonatal calves

Provision of an adequate mass of IgG from maternal colostrum is essential to health and survival of neonatal calves. Colostrum supplements (CS) have been developed to provide supplemental immunoglobulin when maternal colostrum is of poor quality. However, colostrum replacers (CR) that provide > or = 100 g of IgG have not been formulated. Our objective was to determine the absorption of IgG in newborn calves fed CS derived from bovine serum or CR derived from bovine immunoglobulin concentrate. The CS were prepared by collecting, processing, and spray drying bovine serum and blending with other ingredients to provide 45 to 50 g of IgG per dose. The CR were prepared by further processing bovine serum to increase IgG concentration to > 50% IgG and blending with other ingredients to provide 100 to 122 g of IgG per dose. Holstein calves (n = 160) were fed 90 to 244 g of IgG from CS or CR in 1 or 2 feedings in two experiments. Blood was collected from each calf by jugular venipuncture at 0 and 24 h of age and plasma IgG was determined by turbidimetric immunoassay. Apparent efficiency of IgG absorption was calculated. Plasma IgG concentrations at 24 h of age were indicative of IgG intake and averaged 5.5 to 14.1 g/L in calves fed CS and CR. Mean apparent efficiency of IgG absorption in calves fed CS was 25 and 28% in experiments 1 and 2, respectively. Mean apparent efficiency of IgG absorption in calves fed CR ranged from 19 to 32% and were affected by method of processing and number of times fed. Treatment of plasma with polyethylene glycol reduced the efficiency of IgG absorption in experiment 1. The addition of animal fat to CR had no effect on IgG absorption. A second feeding of CR increased plasma IgG, but efficiency of absorption was reduced. Mean body weights at 60 d of age were not affected by treatment and ranged from 64.3 to 78.2 kg. Plasma IgG concentration in calves fed > or = 122 g of IgG from Ig concentrate approached (9.9 g/L) or exceeded 10 g/L, indicating successful transfer of passive immunity. Provision of IgG to prevent failure of passive transfer is possible with CR containing >20% IgG when fed at 454 g per dose.     

Alterations of the circular RNA profile in the jejunum of neonatal calves in response to colostrum and milk feeding

Circular RNA (circRNA) have been suggested to contribute to regulating gene expression in various tissues and cells of eukaryotes. However, little is known regarding the expression pattern of circRNA and their potential function in the small intestine of neonatal calves that receive colostrum. In the current study, jejunum tissue samples were collected from control calves (2 h after birth; CT; n = 3) and neonatal calves that ingested colostrum (24 h after birth; CO; n = 3) or milk (24 h after birth; MK; n = 3) to compare the circRNA expression patterns using a high-throughput RNA sequencing approach. A total of 21,213, 17,861, and 21,737 circRNA were identified in the CT, CO, and MK groups, respectively. Only 13,254 of these circRNA were common to the 3 groups, suggesting high specificity of circRNA expression depending on nutrient type. In total, 243, 249, and 283 circRNA were differentially expressed in the CO versus CT, CO versus MK, and MK versus CT comparisons, respectively. Gene ontology analysis showed that the differentially expressed circRNA and their predicted or known target genes from the CO and MK groups were mainly involved in macromolecule metabolic process, response to stress, and vesicle-mediated transport. Moreover, pathway analysis showed that the Rap1 signaling pathway, focal adhesion, ubiquitin-mediated proteolysis, and extracellular matrix–receptor interaction were the most significantly enriched pathways. These data collectively indicate that circRNA are abundant and dynamically expressed when calves receive colostrum and act as microRNA sponges to regulate their target genes for jejunum function during the early development of newborn calves.     

Quantitative comparative phosphoproteomic analysis of the effects of colostrum and milk feeding on liver tissue of neonatal calves

Posttranslational modifications, mostly phosphorylation, are critical for protein structure and function. However, the association between liver phosphoproteins in neonatal calves and colostrum intake is not well understood. In this study, we examined the liver phosphoproteome profile in neonatal calves after receiving colostrum or milk. Liver tissue samples were collected from control calves (CON, n = 3) 2 h after birth and from calves that received colostrum (CG, n = 3) or milk (MG, n = 3) 24 h after birth. Hepatic phosphoprotein expression profiles were analyzed using quantitative proteomics based on the liquid chromatography–tandem mass spectrometry method. In total, 1,587 phosphorylated sites were identified in 1,011 liver proteins. The most abundant phosphorylation site AA was serine (87.5%), followed by threonine (11.9%) and tyrosine (0.5%). Among the 1,011 phosphoproteins, 219, 453, and 26 displayed differential expression in the CG versus MG, CG versus CON, and MG versus CON comparisons, respectively. Differentially expressed phosphoproteins in the CG–MG comparison included 3-phosphoinositide-dependent protein kinase 1, glucose transporter member 4, protein kinase N2, and vinculin, which were mainly involved in the glycogen metabolic process, transport, growth and development, and cell adhesion process, according to Gene Ontology analysis. Pathway analysis indicated their enrichment in the insulin signaling pathway, spliceosome, and adherens junction. The CG–CON comparison identified differentially expressed phosphoproteins and their target genes that were largely involved in the cellular process, macromolecule metabolic process, developmental process, and transport. Pathway analysis indicated their association with endocytosis, mechanistic target of rapamycin, AMP-activated protein kinase, and insulin signaling pathways. These data demonstrate that changes in the phosphoproteins of liver tissues may play an important role in energy metabolism and immune response in the calves that received colostrum. These results provide novel insights into the crucial roles of protein phosphorylation during the early life of newborn calves.     

Effect of colostrum on the acute-phase response in neonatal dairy calves

The core part of the mammal innate immune system is the acute-phase response (APR), during which acute-phase proteins (APP) are synthesized. Colostrum contains immunomodulating factors such as proinflammatory cytokines and APP in large quantities. We looked at proinflammatory cytokines [IL-1β, IL-6, and tumor necrosis factor-α (TNF-α)] and APP [serum amyloid A (SAA) and haptoglobin (Hp)] in colostrum and in calves' serum. The aim of this study was to evaluate the effects of colostrum on the calves' systemic APR and the associations of the calves' serum APR with short- and long-term weight gain (at the age of 1, 3, and 9 mo). A total of 143 female dairy calves were studied during their first 3 wk of life. The calves were separated from their mothers immediately after birth and bottle-fed 3 L of quality-controlled colostrum once within 2 h after birth. Serum samples were collected once a week during the first 3 wk of life (a total of 1–3 samples per calf). Mean sampling age (±standard deviation) was 4.3 (±2.0) d in the first week, 11.0 (±2.0) d in the second week, and 18.0 (±2.0) d in the third week. Linear regression models were used to study associations of colostrum APP and cytokine concentration with serum APR markers and for studying associations of colostrum and serum APR markers with calves' average daily weight gain (ADWG). Mixed linear regression models were used to compare serum concentrations of APR markers by study weeks. The colostrum IL-6 concentrations were positively associated with serum IL-6 in the first 3 wk of life. Colostrum IL-1β was positively associated with calves' serum IL-1β during the first week of life, and colostrum TNF-α was positively associated with calves' serum TNF-α during the first 2 wk of life. Serum IL-1β concentrations differed over the 3 wk, being the highest during the first week and the lowest during the second week. For IL-6, the concentration during the first week was the highest, and for TNF-α, a steady decline in the concentration was observed. Serum SAA concentrations were elevated during the first 2 wk of life and subsequently declined during the third week. Albumin concentrations were lowest in the first week, whereas Hp concentrations were highest during the second week. Serum concentrations of SAA, Hp, IL-6, and TNF-α during the second week were negatively associated with ADWG at 9 mo of age. The SAA concentrations during the third week of age had a negative association with 9-mo ADWG. Serum Hp concentrations in the third week were negatively associated with 3-mo ADWG. The results of our study suggest that colostrum cytokines influence calf serum cytokine concentrations. Thus, they influence the newborn calves' adaptation to the environment and the development of their immune system. Factors that activate an APR during the second and third week of life have a long-term influence on calves' development.     

Effect of on-farm commercial batch pasteurization of colostrum on colostrum and serum immunoglobulin concentrations in dairy calves

The objectives were to describe the effect of on-farm commercial batch pasteurization on immunoglobulin (IgG) concentrations and the fluid and feeding characteristics of colostrum and to compare serum IgG concentrations in calves fed fresh versus pasteurized colostrum. Newborn calves (123) were systematically allocated to dietary treatments of either fresh or pasteurized colostrum at both the first and second colostrum feedings. The IgG concentrations were measured for batches of colostrum fed fresh and in pre and postpasteurized samples for batches of colostrum fed after being pasteurized and in calf serum. Pasteurization reduced colostrum IgG concentration, with the percentage reduction averaging 58.5 and 23.6% for 95-L and 57-L batches, respectively. Pasteurizing high quality colostrum in 57-L (vs. 95-L) batches resulted in higher IgG concentrations in the end product. Pasteurization of 57-L batches produced colostrum of normal or only mildly thickened consistency that could be fed to calves. Serum IgG concentrations were higher for calves fed fresh colostrum and for calves with a shorter time interval (< or = 6 h) between first and second colostrum feedings. After controlling for the time interval between feedings, serum IgG concentrations were significantly higher for 40 calves fed unpasteurized (19.1 mg/ml) vs. 55 calves fed pasteurized colostrum (9.7 mg/ml) for calves fed 2 L at first feeding. By contrast, there was no difference in serum IgG concentrations between 8 calves fed unpasteurized (16.1 mg/ml) and 20 calves fed pasteurized colostrum (13.5 mg/ml) after calves were fed 4 L at the first feeding. While the latter results suggest that pasteurizing colostrum may work for producers with excellent colostrum management, these results are preliminary and should be interpreted with caution, given the fewer number of calves and batches of colostrum involved with this second comparison.     

Metagenomic analysis revealed the individualized shift in ileal microbiome of neonatal calves in response to delaying the first colostrum feeding

The aim of this study was to explore the effect of colostrum feeding time on the ileal microbiome of neonatal calves. In this study, 22 male Holstein calves were randomly assigned to different colostrum feeding time treatments: after birth (at 45 min, n = 7); at 6 h after birth (n = 8); and at 12 h after birth (TRT12h; n = 7). At 51 h after birth, calves were killed and ileum digesta was collected for microbiome analysis using shotgun metagenomic sequencing. Bacteria, archaea, eukaryotes, and viruses were identified from the ileum microbiome. For the bacteriome, Firmicutes and Proteobacteria were the predominant phyla, and Escherichia, Streptococcus, Lactobacillus were the 3 most abundant genera. For the archaeal community, Euryarchaeota and Crenarchaeota were the 2 major phyla, and Methanosarcina, Methanobrevibacter, and Methanocorpusculum were the 3 most abundant genera. In total, 116 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were identified from the ileal microbiome, with “biosynthesis of vancomycin group antibiotics,” “biosynthesis of ansamycins,” “valine, leucine, and isoleucine biosynthesis,” “ribosome,” and “d-alanine metabolism” as the top 5 functions. When the ileal microbiomes were compared among the 3 treatments, the relative abundance of Enterococcus was higher in TRT12h calves, suggesting that calves may have a higher abundance of opportunistic pathogens when the feeding of colostrum is delayed for 12 h. Moreover, among all KEGG pathways, the enriched “taurine and hypotaurine metabolism” (KO00430) pathway was identified in the ileal microbiome of TRT12h calves; however, future studies are needed to understand the effect on the host. Additionally, 2 distinct ileal microbial profiles were identified across all samples, indicating that that host factors may play a significant role in driving varied microbiome changes in response to colostrum feeding time. Whether such microbiome shifts affect long-term gut function and calf performance warrants future studies.     

Pasteurization of colostrum reduces the incidence of paratuberculosis in neonatal dairy calves

In the present study, the potential benefits of feeding pasteurized colostrum were demonstrated in calves born to dams naturally infected with Mycobacterium avium ssp. paratuberculosis. Calves were separated at birth from their dams and randomly allocated into a group fed either the colostrum of their dam (DC; n = 6), followed by feeding the milk of the dam for 3 wk and then milk replacer, or into a group fed pooled pasteurized colostrum (PC; n = 5) from healthy noninfected dams, followed by milk replacer. At 6 wk of age, calves were weaned onto calf starter, housed together, and fed in a similar manner throughout the rest of the 12-mo study. Calves were necropsied at the end of the study, and 25 tissue sites were sampled from each animal and cultured for M. avium ssp. paratuberculosis. Sixteen of the 25 tissue sites were positive for calves across both treatment groups, with 14 of the 16 tissue sites positive for DC calves and 9 of the 16 tissue sites positive for PC calves. The degree of colonization within a tissue was low and variable for calves within treatment groups, and fecal shedding of M. avium ssp. paratuberculosis was minimal during the 12-mo study. As a measure of the early immune response to infection, blood obtained from calves was stimulated in vitro with M. avium ssp. paratuberculosis antigen preparations, and IFN-_Y secretion was measured. Antigen-specific IFN-_Y was consistently greater throughout the study in DC calves (0.95 ± 0.19) compared with PC calves (0.43 ± 0.10). Although long-term benefits are unknown, these results indicate that feeding a source of colostrum from paratuberculosis-free dams may decrease the initial exposure of neonates to M. avium ssp. paratuberculosis, perhaps decreasing dissemination of infection over time.     

Effects of profound acidemia on the dynamic glucose and insulin response and plasma potassium and phosphorus concentrations during an intravenous glucose tolerance test in neonatal calves

Acidemia and electrolyte imbalances such as hyperkalemia are common in neonatal calves with diarrhea. Acidemia negatively affects the cellular response to insulin and may therefore result in deranged glucose, potassium, and phosphorus homeostasis. The primary aim of this study was to compare indices that characterize the dynamic glucose and insulin response between acidemic and nonacidemic neonatal diarrheic calves and a healthy control group during an intravenous glucose tolerance test (IVGTT) that consisted of i.v. administration of 0.3 g of glucose per kg of body weight. Secondary aims were to characterize the associated changes in plasma potassium and phosphorus concentrations. The effect of correction of profound acidemia with a sodium bicarbonate containing infusion on these parameters was also assessed. Thirty calves (age ≤21 d) were purposively assigned to one of the following groups: 10 calves with diarrhea and profound acidemia (venous blood pH <7.20) where an IVGTT was performed before and after treatment with sodium bicarbonate, 10 calves with diarrhea and minimal acid-base disturbance (venous blood pH >7.35), and 10 healthy control calves. Profoundly acidemic diarrheic calves (jugular venous blood pH 6.99 ± 0.10) had a similar initial increase in plasma insulin concentration to that in healthy control calves or nonacidemic calves with diarrhea. However, insulin concentrations remained relatively stable in acidemic calves between 15 and 60 min after the start of the IVGTT, whereas a marked decrease in plasma insulin concentrations occurred in all other groups during the same period of time. We conclude that acidemia does not alter cell glucose availability or the dynamic response of glucose, phosphorus, and potassium to insulin; however, acidemia markedly prolongs plasma insulin concentrations following an IVGTT through an unidentified mechanism. Results of this study emphasize the importance of correcting acidemia and metabolic acidosis in neonatal calves with diarrhea.     

Influence of feeding fermented colostrum and Lactobacillus acidophilus on fecal flora of dairy calves

Twenty Holstein calves were assigned alternately at birth to diets of 1) fermented colostrum, 2) colostrum treated with 1% propionic acid, 3) whole milk, or 4) whole milk treated with Lactobacillus acidophilus (frozen concentrate culture) at 5 x 10(8) organisms per litter. Diets were fed once daily for 3 wk at 10% of birth weight as the sole source of nutritients. Fecal samples were collected at 0, 7, 14, and 21 days of age and analyzed for coliform and lactobacilli numbers. Fermented colostrum diets did not alter coliform counts in feces of healthy calves. Fecal coliform counts of calves fed L. acidophilus decreased with time. Average fecal lactobacilli counts were lower for the colostrum diets than milk diets. The apparent lowered incidence of scours frequently reported in calves fed fermented colostrum diets was not reflected in major changes in fecal microflora under the conditions of this study.     

Effect of feeding single-dam or pooled colostrum on maternally derived immunity in dairy calves

The role of colostrum management in providing adequate immunological protection to neonatal calves has been widely investigated, and thresholds for colostrum quality, as well as optimum volume and timing for colostrum feeding have been established. However, limited information is available on the effect of colostrum source (single dam or pooled) on passive immunity, as well as subsequent antibody survival in the calf. This study aimed to assess the effect of feeding single-dam colostrum (own and other dam) or pooled colostrum on transfer of passive immunity, and also investigate the rate of depletion of disease-specific antibodies among dairy calves. In total, 320 cows and 119 dairy heifer calves were enrolled in the study. Calves were blood-sampled immediately after birth and received either own-dam, other-dam, or pooled colostrum. Calves were blood-sampled at 24 h to assess serum IgG concentrations and at monthly intervals thereafter to document disease-specific antibody survival. Mean colostrum IgG concentration was higher for other-dam treatment group, whereas own-dam and pooled treatments were similar. For all treatment groups, the mean IgG concentration was >80 mg/mL, exceeding the quality threshold of 50 mg/mL. Mean calf serum IgG concentration was lower for calves fed pooled colostrum compared with those that received colostrum from a single cow. There was a negative association with 24-h serum IgG and calf birth bodyweight; calves <30 kg at birth had the highest 24-h serum IgG concentration. Survival of antibodies to bovine viral diarrhea, Salmonella infection, leptospirosis, bovine parainfluenza 3 virus, bovine respiratory syncytical virus, rotavirus, and coronavirus was not associated with colostrum source; however, antibodies to infectious bovine rhinotracheitis had a greater period of survival among calves fed own-dam colostrum. We found that feeding single-dam colostrum can thus improve calf immunity through increased serum IgG levels and antibody survival rates. Furthermore, we hypothesize that immune exclusion may occur with pooled colostrum; therefore, providing pooled colostrum may still be a good practice as long as it can be ensured that enough antibodies are absorbed into the blood stream to deal with pathogens calves may encounter because different dams may have antibodies against different strains of viruses and bacteria, yielding cross protection.     

The effects of feeding more milk on periprandial plasma glucagon-like peptide-2 concentrations in preweaning dairy calves

The objective of this study was to evaluate periprandial plasma concentrations of glucagon-like peptide-2 (GLP-2), glucose, and β-hydroxybutyrate (BHB) in response to a milk meal in preweaning dairy calves. Nineteen Holstein heifer calves were fed either a high (10 L/d; n = 9) or low (5 L/d; n = 10) amount of pasteurized whole milk from d 2 to 50 of life. Calves were housed in individual pens for the first 19 ± 3 d and fed only milk before being moved to a group pen, where they remained on their respective milk treatment and offered calf starter ad libitum. Blood samples were collected sequentially for 240 min following their milk meal at wk 3, 5, and 7 of life to characterize the periprandial response in plasma concentrations of GLP-2, glucose, and BHB. Baseline plasma glucose concentrations were increased, when a high amount was fed; however, we found no difference in area under the curve. Feeding a high amount of whole milk had no effect on baseline or periprandial plasma BHB concentrations. Baseline plasma GLP-2 concentrations decreased as calves aged. Feeding a high amount of whole milk tended to significantly increase baseline GLP-2 concentrations throughout compared with calves fed a low amount. The periprandial response of GLP-2 was not biphasic until calves were 7 wk old. In conclusion, feeding a high amount of milk may increase GLP-2 concentrations in preweaning calves, although its exact mechanism is unknown.     

Addition of casein or whey protein to colostrum or a colostrum supplement product on absorption of IgG in neonatal calves

The effects of the addition of nonimmunoglobulin protein on absorption of immunoglobulin G (IgG) from colostrum or colostrum supplement products were determined in two experiments. In experiment 1, 48 Holstein calves were fed 4 L of pooled maternal colostrum or 4 L of reconstituted colostrum supplement with 0, 200, or 400 g of added whey protein concentrate or casein. In experiment 2, 38 Jersey calves were fed 2 L of pooled maternal colostrum with 100 or 200 g of whey protein concentrate or casein added immediately before feeding. Blood was collected at 24 h of age and plasma IgG concentration, total protein, hematocrit (experiment 1 only), and plasma urea N were determined. In experiment 1, blood samples were also collected at 4, 8, 12, 16, and 20 h to evaluate absorption of IgG and protein and urea N concentrations. The addition of 400 g of casein to colostrum supplement in experiment 1 reduced plasma IgG from 5.66 g/L (0 g of casein addition) to 3.88 g/L, increased plasma urea N at 24 h, and reduced the change in plasma total protein from 0 to 24 h. Hourly plasma IgG concentrations increased with the consumption of colostrum or supplements but increased more rapidly in calves fed whey protein concentrate and more slowly in calves fed casein. The addition of 200 g of casein or whey protein concentrate to colostrum supplements had no effect on plasma IgG concentration at 24 h of age. The addition of 100 or 200 g of casein or whey protein concentrate to maternal colostrum had no effect on plasma urea N, total protein, or plasma IgG in experiment 2. The addition of nonimmunoglobulin protein to colostrum supplements or maternal colostrum did not affect IgG absorption from the intestine of newborn calves unless the amount of total protein exceeded 500 g of protein.     

Effects of colostrum and milk replacer feeding rates on intake,growth, and digestibility in calves

Newborn Holstein male calves (n = 50) born on a single dairy farm were assigned randomly at birth to receive 3 feedings of 1.8 L of pooled maternal colostrum (MC) at 1, 6, and 12 h of age or 1 feeding of 500 g of a colostrum replacer reconstituted to 1.8 L at 1 h of age, followed by 2 feedings of 227 g of a commercial milk replacer (MR) reconstituted to 1.8 L at 6 and 12 h of age (CR). All feedings were administered by esophageal feeder. At 2 to 3 d of age, calves were transported to the experimental facility and assigned within colostrum group to receive 0.66 kg/d dry matter (DM) of MR to 39 d, and then 0.33 kg/d to 42 d (MRM) or 0.77 kg/d of MR DM to d 13, 1.03 kg/d for 22 d, and 0.51 kg/d for 7 d (MRH). The MR contained 25.8% crude protein and 17.6% crude fat (DM basis) and was based on whey proteins and lard as the primary fat source. Calf starter (21.7% crude protein, 15.7% neutral detergent fiber, 37.4% starch, DM basis) and water were available for ad libitum consumption throughout the 56-d study. Serum IgG and total protein were measured at 2 to 3 d of age. Intakes of MR and calf starter were monitored daily. Calf health and fecal scores were also monitored daily. Body weight was measured weekly, and hip width and body condition score were monitored every 2 wk. Digestion of DM, organic matter, crude protein, and ether extract were determined at 1 and 3 wk from 5 calves randomly selected within treatment and using chromic oxide as a digestibility marker added to the MR. Calves fed CR had lower serum IgG and total protein than calves fed MC. Also, calves fed CR grew more slowly, consumed less calf starter, and were less efficient to 56 d than calves fed MC. The number of days calves were treated with veterinary medications was higher when calves were fed CR. Calves fed MC-MRH gained more BW than other calves from 3 to 8 wk of age. Calves fed CR-MRH consumed less calf starter than other calves during wk 7 and 8. Digestion of nutrients at 1 and 3 wk of the study was unaffected by type of colostrum or level of MR fed and did not change from 1 to 3 wk. Over the first 2 mo of life, the calves fed MRH consumed less calf starter than calves fed MRM, but average daily gain or hip width change did not differ. One feeding of CR followed by 2 feedings of MR in the first 24 h likely reduced absorption of IgG from CR and contributed to differences in health and growth. Differences in animal performance observed in this study were unrelated to MR digestibility.     

Effects of a low- or high-frequency colostrum feeding protocol on immunoglobulin G absorption in newborn calves

Calves might experience an upper limit of IgG absorption from colostrum ingestion at birth, but it is not clear whether the total IgG mass fed in the first meal or feeding frequencies can saturate the IgG transport mechanism and therefore limit IgG absorption. The objective of this study was to determine whether different colostrum replacer (CR) feeding frequencies affect serum IgG levels or apparent efficiency of absorption (AEA) in neonatal calves. Male Holstein calves (n = 40) were separated from their dams immediately after parturition and randomly assigned to receive CR [12% of birth body weight (BW)], following either (1) a low-frequency (LF; n = 20) or (2) a high-frequency (HF; n = 20) feeding protocol. Low-frequency calves received 2 CR meals (8% and 4% birth BW within 1 h after birth and 12 h after first CR feeding, respectively), whereas HF calves received 3 CR meals (4% of BW for each meal; within 1 h after birth, 6, and 12 h after first CR feeding). The CR powder fed had a dry matter IgG concentration of 30% and an IgG concentration of 70.5 g/L when reconstituted. All CR was fed via esophageal tube within 1 h after birth. Calves were bottle-fed pasteurized milk (5% birth BW) at 24, 36, and 48 h after the first CR feeding. Blood was collected before first CR feeding and at the following intervals post-CR feeding: every 2 h until 18 h; every 3 h from 18 to 30 h; and every 6 h from 30 to 48 h after the first CR feeding. Serum IgG values at 24 h did not differ between LF and HF (25.79 ± 0.93 and 25.66 ± 0.88 g/L, respectively). In the first meal, calves fed LF ingested a higher total IgG mass than HF (257.98 ± 4.16 g and 126.72 ± 4.05 g, respectively); however, AEA at 24 h did not differ for calves fed HF or LF (27.68 ± 1.16% and 27.63 ± 1.26%, respectively). The IgG area under the curve (AUC) at 24 h was greater for calves fed LF than HF (443.13 ± 15.17 and 379.59 ± 13.99 g of IgG/L × h, respectively). Additionally, AUC at 6 h, 12 h, and 48 h were greater for calves fed LF than HF. These results indicate that, although LF calves had a greater AUC, HF calves were still able to absorb IgG in the second and third meal, allowing HF calves to achieve serum IgG levels similar to those of LF calves at 24 h. In addition, the provision of 3 meals at 70.5 g/L of IgG within the first 12 h of life did not result in added benefits to serum IgG or AEA levels.