High growth rate fails to enhance adaptive immune responses of neonatal calves and is associated with reduced lymphocyte viability

The objective of the study was to evaluate the effects of 3 targeted growth rates on adaptive (i.e., antigen-specific) immune responses of preruminant, milk replacer-fed calves. Calves (9.1 ± 2.4 d of age) were assigned randomly to one of 3 dietary treatments to achieve 3 targeted daily rates of gain [no growth (maintenance) = 0.0 kg/d, low growth = 0.55 kg/d, or high growth = 1.2 kg/d] over an 8-wk period. The NRC Nutrient Requirements of Dairy Cattle calf model computer program was used to estimate the milk replacer intakes needed to achieve target growth rates. All calves were fed a 30% crude protein, 20% fat, all-milk protein milk replacer reconstituted to 14% dry matter. Diets were formulated to ensure that protein would not be limiting. All calves were vaccinated 3 wk after initiation of dietary treatments with Mycobacterium bovis, strain bacillus Calmette-Guerin and ovalbumin. Growth rates for no-growth (0.11 kg/d), low-growth (0.58 kg/d), and high-growth (1.16 kg/d) calves differed throughout the experimental period. Blood glucose concentrations in high-growth calves increased with time and were higher than in low- and no-growth calves. Mononuclear and polymorphonuclear leukocyte percentages in peripheral blood were unaffected by growth rate but did change with advancing age. Percentages of CD4⁺ T cells increased with age in no-growth and low-growth calves, a characteristic of maturation, but failed to increase in high-growth calves. Growth rate did not affect the percentages of CD45RO⁺ (memory) CD4⁺ and CD8⁺ T cells, antigen (i.e., ovalbumin)-specific serum IgG concentrations, or antigen (i.e., purified protein derivative)-induced IFN-γ and nitric oxide secretion by mononuclear cell cultures. Antigen-elicited cutaneous delayed-type hypersensitivity responses of no-growth calves exceeded responses of low-growth, but not high-growth, calves. In resting- and antigen-stimulated cell cultures, viabilities of CD4⁺, CD8⁺, and γδTCR⁺ T cells from high-growth calves were lower than those of the same T cell subsets from no-growth and low-growth calves. Alternatively, resting cultures of mononuclear leukocytes from high-growth calves produced more nitric oxide than those from no-growth and low-growth calves. In conclusion, adaptive immune responses were affected minimally by growth rate. The results suggest that protein-energy malnutrition in the absence of weight loss is not detrimental to antigen-specific responses of neonatal vaccinated calves and that a high growth rate does not enhance these responses. The negative effect of a high growth rate on the viability of circulating T cell populations may influence infectious disease resistance of the calf.     

Increase in Escherichia coli inoculum dose accelerates CD8+ T-cell trafficking in the primiparous bovine mammary gland

Although migration of leukocytes into the mammary gland is pivotal for a cow's response against intramammary invading pathogens, the contribution of lymphocyte subsets to this response remains unclear. To investigate the dynamics of lymphocyte populations during Escherichia coli mastitis, T-lymphocyte subsets, CD4⁺/CD8⁺ ratio, CD21⁺ cells, and lymphoproliferation were studied in blood and milk of primiparous cows exposed to different quantities of bacteria. The cows were intramammarily inoculated with 10⁴ cfu of E. coli (group A) and 10⁶ cfu (group B). Compared with group A, a much greater number of lymphocytes migrated into the infected quarters at postinfection hour (PIH) 6 to 24 in group B, and the CD8⁺ cells were the first-recruited T cells in the milk. There was a significant decline in the CD4⁺/CD8⁺ ratios at PIH 6 to 24 in group B. The decrease of CD4⁺/CD8⁺ ratios at PIH 6 to 24 resulted mainly from greater CD8⁺ cell concentrations in milk. In contrast, at PIH 72, CD4⁺/CD8⁺ ratios increased about 2-fold in both groups. This increase was mainly due to the increase in CD4⁺ cell concentration. The increased concentration of CD4⁺ cells coincided with an increase in the CD21⁺ cell population in the milk. In blood, the increase of CD8⁺ cells appeared much faster in group B (PIH 6 and 12) than in group A. The results from lymphoproliferation also indicated a greater increase in the proliferative response in both blood and milk lymphocytes of group B. Our study demonstrates for the first time that an increase of E. coli inoculum dose accelerates the trafficking of CD8+ cells during initiation of E. coli mastitis, and these cells are the predominant T cells in milk during the early hours of bovine E. coli mastitis.     

Effects of additional milk replacer feeding on calf health, growth, and selected blood metabolites in calves

The objective of the experiment was to evaluate effects of increased milk replacer feeding on growth, intake, feed efficiency, and health parameters in stressed calves. Holstein bull calves (n = 120; approximately 3 to 8 d of age) were purchased from sale barns and dairy farms and housed in fiberglass hutches. In addition, wood shavings contaminated with coronavirus were mixed with clean shavings and added to each hutch before the start of the experiment. Calves were fed either a fixed amount (454 g/d) of a 20% crude protein (CP), 20% fat milk replacer to weaning at 28 d or a variable amount (454, 681, 908, and 454 g/d on d 0 to 7, 8 to 14, 15 to 31, and 32 to 41, respectively) of a milk replacer containing 28% CP and 17% fat without or with added dietary supplement containing bovine serum. Calves were also fed commercial calf starter and water ad libitum. Plasma IgG concentration in most calves on arrival at the facility was < 10 g/L. Intake, change in body weight, feed efficiency, morbidity and mortality, and selected plasma metabolites were determined. Body weight at 28 d, 56 d, daily body weight gain, intake of milk replacer, fecal scores, days with diarrhea, and days treated with antibiotics were increased with feeding variable amount of milk replacer over the 56-d study. Starter intake from d 1 to 56 was reduced from 919 to 717 g/d in calves fed fixed and variable amounts of milk replacer, respectively. Morbidity, measured as the number of days that calves had diarrhea, was increased by 53% when a variable amount of milk replacer was fed. Calves fed variable milk replacer were treated with antibiotics for 3.1 d compared with 1.9 d for calves fed 454 g of milk replacer/d. Concentrations of plasma glucose, urea N, and insulin-like growth factor-I were increased when calves were fed variable amount of milk replacer. Dietary supplement containing bovine serum had no effect on any parameter measured. There was no effect of milk replacer feeding on concentrations of nonesterified fatty acids, total protein, or growth hormone concentrations. Plasma tumor necrosis factor-α was highest in calves with the highest plasma IgG concentrations on the day of arrival and might be related to the calf's ability to identify pathogens in the environment. Under conditions of this study, calves fed variable amount of milk replacer and exposed to immunological challenge before weaning had greater BW gain, but also increased incidence of diarrhea that required added veterinary treatments.     

Effects of vegetable fats versus lard in milk replacers on feed intake, digestibility, and growth in Finnish Ayrshire bull calves

The aim was to study whether vegetable fat mixtures could be used instead of lard [15.2% in dry matter (DM)] in milk replacers without impairing the performance of Finnish Ayrshire bull calves (n = 58). The growth performance of the calves was measured before and after weaning from 14 d to 6 mo of age. The following 3 fat sources in a milk replacer were studied: 1) a mixture of palm, coconut, and rapeseed oil, 2) palm and coconut oil, and 3) lard. The calves were bucket-fed 2 L of milk replacer 3 times per day. The milk replacer contained 116 g of DM/L, resulting in an average DM intake of 4.8 g of DM/kg of body weight^0.75 (BW^0.75) during the 8-wk trial, after which the calves were weaned. All the calves had free access to water, commercial starter, and grass silage before weaning. The weaned calves had free access to water and grass silage and were given 3 kg/d (air-dry basis) of a commercial concentrate mixture. The concentrate was replaced by barley when the bulls were 4.5 mo old. There were no significant differences between the diets in feed intake and apparent diet digestibility. The health and BW of the calves were similar during the study. The feed conversion rate (kg of DM intake/kg of gain) before weaning was significantly greater for the lard diet compared with the 2 vegetable fat mixtures. After weaning, the feed conversion rate was slightly lower for the diet that included the palm, coconut, and rapeseed oil mixture than for the diet that included palm and coconut oil mixture. The study showed that the 2 mixtures consisting solely of vegetable oils were effective dietary components, thus providing 2 alternative fat mixtures of milk replacers, for use instead of lard in formulating commercial calf milk replacers.     

Relationship between cortisol response to stress and behavior, immune profile, and production performance of dairy ewes

The existence of a relationship between cortisol levels, after an acute stress, and behavioral activities, immunological profile, and production performance in sheep was studied. An initial flock of 30 Comisana ewes was involved in the experiment, and each of the 30 ewes was individually subjected to an isolation test in a novel environment. Subsequently, from the initial flock, 2 groups of 8 Comisana ewes were each retrospectively selected, and the animals were divided, according to their cortisol concentration 10 min after the isolation test, into high cortisol (HC) ewes, having a peak of cortisol concentration >90 ng/mL (average: 119.3 ng/mL ± 11.8), and low cortisol (LC) ewes having a peak of cortisol concentration <80 ng/mL (average: 52.4 ± 11.8). During the isolation test, the behavior of each animal was video-recorded and behavioral activities were registered. Blood samples were collected before the isolation test, immediately after the test (10 min), and at 60, 120, 300 min, 24 h, and 48 h after the test to evaluate percentages of T-helper (CD4⁺) and T-cytotoxic (CD8⁺) cells, CD4⁺/CD8⁺ ratio, and IL-1β and IL-6 levels. The ewes were milked for 3 d after the isolation test to determine cortisol levels and IL-1β and IL-6 concentrations in whey. Milk yield was recorded at each milking, and milk samples were analyzed for pH, nutritional parameters, renneting properties, and somatic cell count. During the isolation test, HC ewes exhibited a shorter duration of movement and fewer bleats than LC ewes. The average plasma IL-1β concentration was higher in HC than in LC ewes. The average whey IL-1β and IL-6 concentrations were higher in whey from HC ewes than in LC ewes. A positive correlation emerged between plasma and whey IL-1β concentrations. The average CD4⁺/CD8⁺ ratio in blood was lower in HC than in LC ewes. Time from isolation affected the CD4⁺/CD8⁺ ratio: at 120 min, the CD4⁺/CD8⁺ ratio increased compared with that at 10 min after isolation and then decreased until 300 min after isolation. On average, ewes with low cortisol concentrations showed higher milk production and lower SCC than ewes with high cortisol concentrations. Results suggest that plasma cortisol concentration is connected to the behavioral response and immune competence of dairy ewes and cytokine concentrations. Both whey IL-1β and IL-6 can be considered reliable indicators of the magnitude of hypothalamic-pituitary-adrenal axis activation. The stress-induced changes in CD4⁺/CD8⁺ ratio are critical for controlling disease incidence and planning appropriate vaccination programs. High reactivity of the hypothalamic-pituitary-adrenal axis is also associated with a reduction in milk production and an increased predisposition to develop intramammary inflammatory processes.     

Feeding activated charcoal from bark containing wood vinegar liquid (nekka-rich) is effective as treatment for cryptosporidiosis in calves

The effect of activated charcoal containing wood vinegar liquid (Nekka-Rich) on Cryptosporidium parvum was evaluated in vitro and in vivo. First, the adsorption of C. parvum by the activated charcoal component of Nekka-Rich was examined. When mixed, C. parvum oocysts were effectively adsorbed by activated charcoal. Next, the effect of the wood vinegar liquid component of Nekka-Rich was assessed. Wood vinegar liquid had an antiprotozoan activity against C. parvum oocysts. Finally, the anticryptosporidial effect of Nekka-Rich was evaluated in calves experimentally infected with C. parvum. Six neonatal calves at 7 d of age were orally infected with 1 × 10⁵ oocysts of C. parvum. When diarrhea was observed (on d 3 after the experimental infection), 3 calves received a milk replacer containing 10 g of Nekka-Rich at 8-h intervals for 4 consecutive days, and 3 control calves were given a milk replacer without Nekka-Rich at 8-h intervals for 4 consecutive days. Calves fed milk with Nekka-Rich showed recovery from diarrhea 1 d after the start of treatment. Significantly less fecal excretion of C. parvum oocysts was observed 1 d after treatment in calves fed Nekka-Rich. On d 2 from the beginning of treatment with Nekka-Rich (on d 5 after the experimental infection), oocysts were not isolated from fecal samples. On the other hand, nontreated control calves developed severe diarrhea, and fecal excretion of oocysts was consistently observed. Calves in both groups were killed for collection of samples, which were subjected to scanning electron microscopy. Scanning electron microscopy revealed adherence of C. parvum oocysts to the intestinal epithelial surface of nontreated control calves, whereas a lack of C. parvum adhesion was observed in calves fed Nekka-Rich. These results suggest that Nekka-Rich would be useful for the treatment of cryptosporidiosis in neonatal calves.     

The effects of early weaning on innate immune responses of Holstein calves

The objectives of this study were to compare innate immune responses of calves weaned early (EW; n = 23; weaned at 23.7 ± 2.3 d of age) with those of conventionally weaned calves (CW; n = 22; weaned at 44.7 ± 2.3 d of age). All calves were fed 3.8 L of colostrum within 12 h of birth and were subsequently fed milk replacer twice daily. The weaning process began by withdrawal of the afternoon milk-replacer feeding. Milk was fully withdrawn, and the calf was considered completely weaned when it consumed 900 g of calf starter as-fed for 2 consecutive days. Blood samples were collected from all calves at 24, 27, 31, 45, 48, 52, and 66 ± 2.3 d of age. Early weaned calves took a variable amount of time to completely wean from milk replacer; therefore, data were also analyzed by comparing calves grouped by latency to completely weaned (fast = 1 to 5 d; intermediate = 6 to 8 d; slow = 15 to 17 d). Slow-EW calves weighed less than either the fast- or intermediate-EW calves before initiating weaning. At 27 d of age, circulating neutrophils were greater among EW calves than CW calves. Moreover, fast-EW calves had lower neutrophil:mononuclear cell ratios at 45 d of age than other EW calves. Slow-EW calves had lower TNF-α concentrations from whole blood stimulated with endotoxin at 27 and 31 d of age compared with fast- and intermediate-EW calves. All EW calves had decreased neutrophil L-selectin at d 27 and increased neutrophil L-selectin at 31 d of age. At 31 d of age, neutrophil β₂-integrin was the greatest among the fast-EW calves. All EW calves had decreased neutrophil oxidative burst at 27 and 31 d of age. Three days after CW calves were weaned they had higher neutrophils, hematocrit percentages, and circulating cortisol than EW calves. In addition, 3 d after CW calves were weaned they had decreased neutrophil oxidative burst responses to Escherichia coli. Weaning, irrespective of age, suppressed many innate immune responses. In addition, early weaning transiently suppressed L-selectin expression on neutrophils; however, the immunological significance in the context of the resistance to disease is unknown because EW calves likely had greater protection from passively derived immunoglobulins when they were weaned. Finally, calves with lower BW around 24 d of age may not be suitable for early weaning programs as evident in the suppressed secretion of TNF-α from whole blood cultures during the week following the initiation of weaning.     

Comparison of supplementation of n-3 fatty acids from fish and flax oil on cytokine gene expression and growth of milk-fed Holstein calves

The ability to reduce incidence of disease in calves and improve early vaccination strategies is of particular interest for dairy producers. The n-3 fatty acids have been reported to reduce inflammatory diseases in humans but limited research has been done in calves. The objective of this study was to compare supplementation of n-3 fatty acids from fish and flax oil on gene expression of whole blood cells and growth of milk-fed Holstein calves. Forty-eight Holstein bull calves from a commercial dairy were randomly assigned to 1 of 3 diets beginning at 4 d old: (1) control milk replacer (MR) with all pork fat, (2) MR with 2% flax oil, and (3) MR with 2% fish oil. All MR were 17% fat, 27% crude protein on a dry matter (DM) basis, with all protein from whey sources. Calves were each fed 654 g DM of MR daily for the first 25 d and then 327 g/d for d 26, 27, and 28. On d 28, calves were challenged with a Pasteurella vaccine and the temperature response to the vaccine was recorded. Milk and feed intake and fecal scores were recorded daily, and body weight and hip width were recorded weekly. Blood was collected from all calves on d 25. One tube of collected blood was incubated with endotoxin (lipopolysaccharide; LPS) for 2 h and frozen with a second tube of control blood. Quantitative real-time PCR was used to assess the effects of LPS stimulation on cytokine gene expression. During the 28 d, calves supplemented with flax oil had a greater growth rate and feed efficiency than calves fed fish oil (0.52 ± 0.02 vs. 0.48 ± 0.02 g of gain:g of feed). Fish oil tended to decrease LPS stimulation of tumor necrosis factor-α expression. Flax oil, but not fish oil, decreased the expression of IL-4 and tended to decrease expression of osteopontin and IL-8. Flax oil tended to reduce the increase in rectal temperature in response to a Pasteurella vaccine. In conclusion, our data support the idea that supplementation with n-3 fatty acids affects cytokine gene expression.     

Short communication: Addition of varying amounts of sodium bicarbonate to colostrum replacer: effects on immunoglobulin G absorption and serum bicarbonate in neonatal calves

Fifty-two dairy calves were blocked by birth date and, within each block, randomly assigned to 1 of 4 treatments to investigate the effects of incremental levels of sodium bicarbonate (NaHCO₃) on IgG metabolism. Treatments were (1) colostrum replacer (CR) + 0 g of NaHCO₃ (control); (2) CR + 15 g of NaHCO₃; (3) CR + 30 g of NaHCO₃; or (4) CR + 45 g of NaHCO₃. Calves were fed colostrum replacer (>200 g of IgG) in one feeding within 45 min of birth (0 h) and 2 L of milk replacer at 12, 24, 36, and 48 h. Only calves born in calving pens from multiparous cows with no dystocia were used in this study. Blood samples were taken at 0, 6, 12, 24, and 48 h postpartum, and serum was analyzed for IgG using radial immunoassay and bicarbonate using spectrophotometry. Feeding increasing levels of sodium bicarbonate had negative linear effects on IgG concentration, IgG apparent efficiency of absorption, and IgG area under the curve, primarily due to the effect of the highest dose of NaHCO₃ (45 g). Sodium bicarbonate treatments had no effect on serum bicarbonate concentration. However, area under the curve of serum bicarbonate increased linearly with the amount of NaHCO₃ fed.     

Improved performance and heightened neutrophil responses during the neonatal and weaning periods among outdoor group-housed Holstein calves

The objective was to determine if outdoor group housing of Holstein calves influences metabolic status, leukocyte responses, and behavior compared with individually housed calves. Forty-nine Holstein heifer calves (2 ± 1 d of age) were randomly assigned to 1 of 2 treatments: individually housed (G1; n = 22) or group housed [3 calves per pen (G3); n = 27]. The space allowances per calf were 4.8 and 7.0 m² for G1 and G3, respectively. All calves were offered an identical plane of milk replacer nutrition (747 and 1,010 g of DM/d of a 28% CP:20% fat milk replacer from wk 1 to 2 and wk 3 to 6, respectively). Weaning was initiated during wk 7 by removing the p.m. feeding and calves were completely weaned when they consumed 900 g of calf starter/d (as fed) for 2 consecutive days after d 54. At d 90, calves were commingled into random outdoor groups of 5 calves per pen. Peripheral blood was collected during the neonatal (d 3, 10, and 21), weaning (d 46, 48, and 54), and commingling periods (d 90, 93, and 98) and was analyzed for neutrophil oxidative burst (OB) capacity when cocultured with Escherichia coli, neutrophil surface L-selectin protein expression, and whole-blood secretion of tumor necrosis factor-α when cocultured with lipopolysaccharide. Starter intake was greater for G3 during the postweaning period (wk 8 to 12). Average daily gain was greater for G3 than G1 from d 54 to 68 and tended to be greater after commingling from d 113 to 133. During the neonatal period, G3 calves had more activated neutrophils, as evidenced by increased neutrophil L-selectin protein expression and a tendency for increased percentage of neutrophils producing an OB than G1 calves. During weaning, G3 calves continued to have more activated neutrophils with increased L-selectin expression on d 46 and 48 and a greater OB intensity throughout the period. No differences were observed among leukocyte responses between treatments at d 93 and 98. Outdoor group-housed Holstein calves had improved performance and heightened neutrophil responses compared with individually housed calves.     

CD2/CD21 index: A new marker to evaluate udder health in dairy cows

Lymphocytes play a significant role in the immunological processes of the bovine mammary gland and were found to be the dominant cell population in the milk of healthy udder quarters. The objective of this study was to investigate the quantitative relationship between CD2⁺ T and CD21⁺ B lymphocytes using flow cytometry. In a first study, quarter foremilk samples from apparently healthy udder quarters [somatic cell counts (SCC) ≤100,000 cells/mL; n = 65] were analyzed and compared with diseased quarters (SCC >100,000 cells/mL; n = 15). Percentages of CD2⁺ T cells were significantly higher in milk samples with SCC ≤100,000 cells/mL than in those with SCC >100,000 cells/mL, whereas percentages of CD21⁺ B cells developed in the opposite direction. As a result of this opposing trend, a new variable, the CD2/CD21 index—representing the percentages of CD2⁺ cells per CD21⁺ cells—was defined. Although diseased quarters with SCC >100,000 cells/mL and the detection of major pathogens revealed generally CD2/CD21 indices <10, values >10 were observed in apparently healthy quarters. Hence, a CD2/CD21 index cutoff value of 10 may be suitable to aid differentiation between unsuspicious and microbiologically suspicious or diseased udder quarters. To test whether CD2/CD21 indices <10 were primarily related to pathogens, quarters with SCC ≤100,000 cells/mL and >100,000 cells/mL with different bacteriological status (culture negative, or minor or major pathogens) were selectively examined in a second biphasic study. In the first trial, 63 udder quarters were analyzed and 55 of these quarters were able to be sampled again in the second trial carried out 14 d later. In both trials, results of the first study were confirmed. Indeed, CD2/CD21 indices <10 were also found in quarters showing SCC ≤100,000 cells/mL and containing minor or major pathogens at the time of the current or previous bacteriological analysis. The results of our examinations indicated a clear relationship between the CD2/CD21 index and the bacteriological status of the mammary gland. In combination with SCC, it offers a new marker for quick differentiation of unsuspicious and microbiologically suspicious or diseased udder quarters.     

Automated measurement of changes in feeding behavior of milk-fed calves associated with illness

There is a need for improved methods of detecting illness among group-housed milk-fed calves. In 4 separate experiments, we examined whether illness in group-housed dairy calves fed with an automated milk feeder changed their feeding behavior, and whether these changes were affected by low (n = 26) or high (n = 38) milk rations. All calves were subjected to regular health checks that included general condition, rectal temperature, lung auscultation, and fecal scoring. We match paired calves that succumbed to illness with healthy calves on the same feeding allowance. In the days following clinically identified illness (gastroenteric or respiratory affections), sick calves fed high allowances of milk or milk replacer decreased milk intake (−2.59 ± 0.7 L/d) and frequency of visits to the milk feeder (−2.43 ± 0.3 visits/d), and increased the duration of each visit to the milk feeder (1.66 ± 0.5 min/visit) compared with healthy calves fed at the same allowance. However, sick calves fed a low allowance of milk or milk replacer only decreased the duration of each visit to the milk feeder (−1.35 ± 0.2 min/visit) compared with healthy calves. Feed allowance affected feeding behavior associated with illness of milk fed calves.     

Influence of different oral rehydration solutions on abomasal conditions and the acid-base status of suckling calves

The aim of the study was to investigate the influence of oral rehydration solutions (ORS) on milk clotting, abomasal pH, electrolyte concentrations, and osmolality, as well as on the acid-base status in blood of suckling calves, as treatment with ORS is the most common therapy of diarrhea in calves to correct dehydration and metabolic acidosis. Oral rehydration solutions are suspected to inhibit abomasal clotting of milk; however, it is recommended to continue feeding cow's milk or milk replacer (MR) to diarrheic calves to prevent body weight losses. Three calves with abomasal cannulas were fed MR, MR-ORS mixtures, or water-ORS mixtures, respectively. Samples of abomasal fluid were taken before and after feeding at various time points, and pH, electrolyte concentrations, and osmolality were measured. The interference of ORS with milk clotting was examined in vivo and in vitro. To evaluate the effects of ORS on systemic acid-base status, the Stewart variables strong ion difference ([SID]), acid total ([A_tot]), and partial pressure of CO₂ (pCO₂) were quantified in venous blood samples drawn before and after feeding. Calves reached higher abomasal pH values when fed with MR-ORS mixtures than when fed MR. Preprandial pH values were re-established after 4 to 6 h. Oral rehydration solutions prepared in water increased the abomasal fluid pH only for 1 to 2 h. Oral rehydration solutions with high [SID₃] ([Na⁺] + [K⁺] − [Cl⁻]) values produced significantly higher abomasal pH values and area under the curve data of the pH time course. Caseinomacropeptide, an indicator of successful enzymatic milk clotting, could be identified in every sample of abomasal fluid after feeding MR-ORS mixtures. The MR-ORS mixtures with [SID₃] values ≥92 mmol/L increased serum [SID₃] but did not change venous blood pH. Oral rehydration solutions do not interfere with milk clotting in the abomasum and can, therefore, be administered with milk. In this study, MR-ORS mixtures with high [SID₃] values caused an increase of serum [SID₃] in healthy suckling calves and may be an effective treatment for metabolic acidosis in calves suffering from diarrhea.     

Growth characteristics of calves fed an intensified milk replacer regimen with additional lactoferrin

The objective of this study was to evaluate the effect of lactoferrin addition to milk replacer varying in crude protein (CP) on dry matter intake, growth, and days medicated. Thirty-four Holstein heifer calves were assigned to 4 treatments in a 2 × 2 factorial arrangement of treatments in a randomized complete block design. Treatments were as follows: 562 g daily of a nonmedicated conventional milk replacer (20% CP:20% fat) feeding regimen with or without 1 g of supplemental bovine lactoferrin (n = 9 for both treatments) or a nonmedicated intensified milk replacer feeding regimen (28% CP:20% fat) fed on a metabolizable energy basis (0.2 Mcal/kg BW^0.75) from d 2 to 9, and at 0.27 Mcal/kg BW^0.75 from d 10 to 42 with or without 1g supplemental bovine lactoferrin (n = 8 for both treatments). Calves were fed pelleted starter (25% CP) in 227.5-g increments beginning on d 2 and had free access to water. Calves remained on the study for 14 d postweaning. Dry matter intake was determined daily. Growth measurements were taken weekly. Blood samples were taken twice weekly for determination of blood urea N. On d 10 of life, calves were subjected to a xylose challenge. Calves on conventional treatments ate more starter preweaning, during weaning, and postweaning. Preweaning, intensively fed calves had higher dry matter intakes. Weights of intensified-fed calves were greater at weaning. Intensified milk replacer-fed calves had greater average daily gain preweaning and overall and higher gain:feed ratios preweaning, but conventionally fed calves had higher gain:feed ratios during weaning. Intensified milk replacer-fed calves had greater hip heights during weaning and postweaning and greater heart girths preweaning, weaning, and postweaning. Days medicated were greater preweaning and overall for intensified-fed calves. There were no differences among treatments for xylose absorption. Calves on conventional treatments had increased blood urea nitrogen concentrations preweaning. There were no effects of lactoferrin on any experimental variable. Intensified milk replacer-fed calves consumed less starter but had higher average daily gains overall and larger frames and greater BW than conventionally fed calves. An intensified milk replacer feeding regimen promotes faster growth during the preweaning period when compared with calves fed conventional treatments, but supplemental bovine lactoferrin was not beneficial under these experimental conditions.     

Effects of compound probiotics on growth performance,rumen fermentation,blood parameters,and health status of neonatal Holstein calves

This study aimed to investigate the effects of compound probiotics (consisting of 10⁸ cfu/g of Lactobacillus plantarum, 10⁸ cfu/g of Pediococcus acidilactici, 10⁸ cfu/g of Pediococcus pentosaceus, 10⁷ cfu/g of and Bacillus subtilis) on growth performance, rumen fermentation, bacteria community, blood parameters, and health status of Holstein calves at the first 3 mo of age. Forty-eight newborn calves were randomly divided into the following 3 groups: control group (milk replacer with no compound probiotics), low compound probiotics group (milk replacer + 0.12 g of compound probiotics per head per day), and high compound probiotics group (HP; milk replacer + 1.2 g of compound probiotics per head per day). Starter pellets of the low compound probiotics and HP groups were coated with 0.05% compound probiotics. Milk replacer was provided from 2 to 63 d of age (6 L at 2–10 d, 8 L at 11–42 d, 6 L at 43–49 d, 4 L at 50–56 d, and 2 L at 57–63 d), and starter pellets were provided ad libitum from 7 to 90 d of age. Body weight and body size (d 1, 30, 60, and 90), blood (d 40 and 80), and rumen fluid (d 90) were analyzed using the one-way ANOVA procedure; fecal score was recorded daily and analyzed as repeated measures using the mixed model procedure. Results showed that diet supplemented with compound probiotics had no effects on the body weight, average daily gain, dry matter intake, and feed efficiency. At 90 d of age, diet supplemented with compound probiotics decreased the withers height. Immunity activities increased in the HP group, supported by the increased concentrations of serum total protein and immunoglobulins at 40 d of age, and by the increased activity of superoxide dismutase at 80 d of age. Diet supplemented with compound probiotics altered rumen fermentation, indicated by the decreased rumen acetic acid and propionic acid, and the increased butyric acid concentrations. Diet supplemented with compound probiotics improved the health status of calves, indicated by the decreased fecal score at 3 wk of age and the decreased medicine treatments. In summary, although diet supplemented with HP decreased the withers height, this level of probiotics is recommended to improve rumen development and health status of newborn Holstein calves.     

Changes of immunophysiological characteristics in neonatal calves experimentally challenged with mixture of live bacteria and virus

The aim of the present study was to define efficient immunophysiological parameters in neonatal Holstein calves with an experimentally induced microbial infection. Calves (n = 15) were challenged with classical swine fever virus (LOM strain) and Erysipelothrix insidiosa live vaccine by intravenous injection at 3 wk of age except for control calves (n = 4). The level of total serum IgA was significantly increased at 14 and 19 d post-experimental challenge (DPEC) compared with that in calves at −2 DPEC. At 5 DPEC, relative amounts of bacterial- and viral-specific IgA increased significantly and were sustained until 26 DPEC. In the hematology assay, the neutrophil:lymphocyte ratio (%) in whole blood was significantly decreased at 14 DPEC because of a significant increase in lymphocytes and a coincident decrease in neutrophils. The percentages of CD4⁺ and CD25⁺ T cells were significantly decreased at 14 DPEC and returned to initial levels at 19 DPEC. It is intriguing to note that the level of serum lactoferrin was significantly decreased by the microbial challenge within 1 d. The concentration of haptoglobin was increased within 3 d and gradually decreased in calves after microbial challenge. Our results suggest that 1) bovine serum lactoferrin plays an important role in the innate immune response against microbial infection at an early stage and 2) experimentally induced microbial challenge using porcine live bacterial and viral vaccine in calves could be a good experimental model to evaluate the effect of diet or stress induced by environmental change on the immune responses against microbial infection.     

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.     

Supplementation of 1% L-glutamine to milk replacer does not overcome the growth depression in calves caused by soy protein concentrate

Glutamine, an important fuel and biosynthetic precursor in intestinal epithelial cells, helps maintain intestinal integrity and function when supplemented to the diet of many species. The hypothesis tested here was that glutamine supplementation would overcome the decreased average daily gain (ADG) and altered intestinal morphology caused by milk replacer containing soy protein concentrate (SPC). Holstein calves (9 male and 1 freemartin female per treatment) were assigned to diets of 1) all-milk-protein (from whey proteins) milk replacer, 2) milk replacer with 60% milk protein replacement from SPC, and 3) SPC milk replacer as in diet 2 plus 1% (dry basis) l-glutamine. Milk replacers were reconstituted to 12.5% solids and were fed at 10% of body weight from d 3 to 10 of age, and at 12% of body weight (adjusted weekly) from d 10 through 4 wk of age. No dry feed (starter) was fed, but water was freely available. Glutamine was added at each feeding to reconstituted milk replacer. Five calves from each treatment were slaughtered at the end of wk 4 for measurements of intestinal morphology. The ADG was greater for calves fed the all-milk control than for those fed SPC; glutamine did not improve ADG (0.344, 0.281, and 0.282 kg/d for diets 1 to 3, respectively). Intake of protein was adequate for all groups and did not explain the lower growth for calves fed SPC. Villus height and crypt depth did not differ among treatments in the duodenum. In the jejunum, villus height (713, 506, and 464 μm, for diets 1 to 3, respectively) and crypt depth (300, 209, and 229 μm, respectively) were greater for calves fed all milk protein than for either SPC group. In the ileum, villus height was greater for calves fed all milk than for either soy group (532, 458, and 456 μm), whereas crypt depth tended to be greater (352, 301, and 383 μm for diets 1 to 3, respectively), and the villus to crypt ratio was lower for calves supplemented with glutamine than for those fed SPC alone. Urea N concentration in plasma was greater for calves supplemented with glutamine than for those fed SPC alone, indicating that glutamine was at least partially catabolized. Supplemental l-glutamine did not improve growth or intestinal morphology of calves fed milk replacer containing SPC.