Use of the relative dose response (RDR) assay to determine vitamin A status of calves at birth and four weeks of age

An accurate assessment of vitamin A status can be determined by analysis of liver biopsy samples; however, liver biopsies are not always feasible. Plasma concentrations of vitamin A do not provide an accurate indication of vitamin A status. The objective of this study, therefore, was to determine the ability of the relative dose response assay to indicate the vitamin A status of Holstein calves. Calves were obtained at birth and assigned to vitamin A treatments (0, 1700, 34,000, or 68,000 IU/d) added to milk replacer. Liver biopsies and relative dose response assays were performed at birth and 4 wk. Calves supplemented with 1700, 34,000, or 68,000 IU of vitamin A/d had adequate (greater than 20 microg/g) liver concentrations of vitamin A at 4 wk of age. The relative dose response assay at 4 wk was correlated with liver concentrations of vitamin A. Both the relative dose response assay and liver concentrations of vitamin A indicated that calves not supplemented with vitamin A had low vitamin A status, whereas other treatment groups had adequate vitamin A status. Plasma concentrations of retinol increased by 4 wk of age in calves receiving supplemental vitamin A at 34,000 IU and 68,000 IU/d and decreased in unsupplemented calves; however, all calves had concentrations of <20 microg of retinol/dl of plasma. The relative dose response assay agreed with liver biopsies as an indication of vitamin A status, whereas plasma concentrations of retinol incorrectly indicated all treatment groups were deficient in vitamin A.     

Influence of dietary vitamin A content on serum and liver vitamin A concentrations and health in preruminant Holstein calves fed milk replacer

Evidence has suggested that the current requirement for vitamin A tabulated by the NRC [(approximately 3800 IU of vitamin A/kg of dry matter (DM)] for dairy calves fed liquid diets is too low. The objective of this study was to assess the effects of vitamin A content in milk replacers on serum and liver vitamin A concentrations, growth, and development of clinical signs of vitamin A deficiency in calves. Male Holstein calves were separated from their dams at birth and given standardized feedings of colostrum and milk replacer for 3 d. On d 4, calves were assigned to five groups and fed milk replacer containing 2300, 6200, 9000, 18,300, or 44,000 IU of vitamin A/kg of DM. Liver biopsies and serum samples were taken on d 4, 9, 15, 21, and 28 to monitor vitamin A concentrations. Weekly physical and neurological examinations were performed to monitor the development of deficiency signs. Fecal scores, body temperature, and the presence of nasal and ocular discharge were recorded daily. Liver vitamin A concentrations in calves allotted to diets with 2300 and 6200 IU of vitamin A/kg decreased from d 4 to 28. Calves fed 9000 IU of vitamin A/kg maintained liver stores, while those fed 18,300 and 44,000 IU of vitamin A/kg had significant increases in hepatic vitamin A. A strong negative association existed between incidence of hyperthermic temperatures and vitamin A concentration in the diet; calves fed 2300 IU of vitamin A/kg had approximately three times more hyperthermic readings than did calves fed other treatments. A strong negative association also existed between fecal score and concentration of vitamin A in the diet; calves fed diets containing low vitamin A concentration had a higher incidence of high fecal scores (more watery) than did calves fed diets with higher vitamin A concentrations. Although slight differences were detected in serum retinol concentration, growth performance and incidence of ocular and nasal discharges were not different among treatment groups. Our data indicate that vitamin A concentrations of less than 9000 IU/kg of DM in milk replacers result in declining liver vitamin A stores in preruminant calves. Using the human Dietary Reference Intakes as a model for calculating the requirement, we recommend that the vitamin A requirement for preruminant calves should be increased to 11,000 IU of vitamin A/kg of DM.     

Effect of Vitamins A and E on Nitric Oxide Production by Blood Mononuclear Leukocytes from Neonatal Calves Fed Milk Replacer, ,

This study evaluated the effects of dietary vitamin A and E on the in vitro capacity of blood mononuclear leukocytes from calves to produce nitric oxide. Calves fed milk replacer received 100 IU/d of vitamin E as RRR-α-tocopherol or RRR-α-tocopheryl acetate and 0, 1700, 34,000, or 68,000 IU of vitamin A as retinyl acetate. Leukocytes from calves produced greater amounts of nitric oxide relative to leukocytes from adult cattle. The greater production of nitric oxide by calf leukocytes may be typical of the immature neonatal immune system. Nitric oxide production by calves fed RRR-α-tocopherol and either 1700 or 34,000 IU of vitamin A was less than that of calves in other groups and was more typical of production by leukocytes from cows. Our data suggest that optimal amounts of dietary vitamins A and E prompt the maturation of this response toward one that is more typical of adult cattle. Leukocytes from 1-wk-old calves produced less nitric oxide and were less responsive to stimuli than were leukocytes from older calves, a possible consequence of suppressive factors that were present in the ingested colostrum or in the circulation at birth.     

Plasma lipid concentrations in preruminant calves fed whole milk with whey protein isolate

The objective was to investigate the acute effects of retinol acetate added to whey protein isolate (WPI) on postprandial changes in plasma retinol (experiment 1) and the acute effects of milk fat added to WPI on triglyceride (TG), chylomicrons and very low density lipoprotein (VLDL), and fatty acid concentrations (experiment 2) in suckling calves at 1 and 6 wk of age. In experiment 1, 16 Holstein male calves were alloted to 2 equal groups. On the days of measurement, the calves were fed at 0900 h whole milk [4% of body weight (BW)] mixed with vitamin A acetate (500,000 IU) with or without WPI (0.04% of BW). At 1 wk of age, significantly higher postfeeding concentrations of plasma retinol were observed in the calves fed milk with WPI. At 6 wk of age, no differences in the plasma retinol concentrations were observed between 2 groups. On the days of measurement in experiment 2, 16 male calves were fed at 0900 h whole milk (4% of BW) with added milk fat prepared by centrifugation from whole milk (2% of BW) with or without WPI (0.04% of BW). The milk supplemented with fat was prepared on the day before the measurement. At 1 wk of age, significant higher postfeeding concentrations of plasma TG concentrations were obtained in the calves fed WPI than in the control calves, immediately after the meal or from 7 h later onward. Plasma chylomicrons and VLDL concentrations at 1 wk of age were significantly higher in the WPI-fed group than in the control group at 8 h postfeeding. In the calves with the WPI diet, plasma concentrations of myristic, palmitic, stearic, oleic, and linoleic acids at 1 wk of age were significantly higher than those in the control calves at 8 h after feeding. However, chylomicrons and VLDL, and fatty acid concentrations did not differ between the 2 groups after feeding at 6 wk of age. Results indicate that WPI increases plasma lipid concentration of preruminant calves only at 1 wk of age. These data are interpreted to indicate that WPI enhances mainly lipid uptake in the intestines of neonatal calves.     

Modulation of fat-soluble vitamin concentrations and blood mononuclear leukocyte populations in milk replacer-fed calves by dietary vitamin A and beta-carotene

Dairy calves (n = 18), separated from dams at birth, were fed 1 L of pooled-colostrum. For the remaining 7 wk of the study, they were fed one of three diets consisting of either a custom-formulated milk replacer without vitamin A (controls), or supplemented with retinyl palmitate (equivalent to 32,000 IU of vitamin A/d) or with beta-carotene (equivalent to 20,000 IU of vitamin A/d). Plasma retinol, beta-carotene, and RRR-alpha-tocopherol concentrations were lowest at birth, and increased substantially from birth to 1 wk postpartum in all groups, a probable consequence of ingestion of colostrum. From 1 to 7 wk of age, retinol concentrations were greatest in retinyl palmitate-supplemented calves, intermediate in beta-carotene-supplemented calves and lowest in control calves. At 2, 3, 5, 6, and 7 wk, RRR-alpha-tocopherol concentrations were lower in retinyl palmitate-supplemented calves than in control calves. A negative correlation between plasma retinol and vitamin E concentrations existed from wk 2 to 7, suggesting vitamin A influences the absorption and distribution of RRR-alpha-tocopherol. Supplemental retinyl palmitate, but not beta-carotene, was associated with a reduction in the percentage of blood mononuclear leukocytes expressing CD2, CD4, and CD8-T cell antigens and interleukin-2 receptors. By wk 7, leukocyte populations from retinyl palmitate-supplemented calves were more similar to those from adult cattle than those from control calves, suggesting that supplemental vitamin A, as retinyl palmitate, affects the maturation of the neonatal immune system. Differences in the composition of blood mononuclear leukocyte populations may represent changes in immune competency.     

Effect of beta-lactoglobulin on plasma retinol and triglyceride concentrations, and fatty acid composition in calves

Beta-lactoglobulin (beta-lg) is the main protein of ruminant milk whey. Although beta-lg can bind in vitro to a variety of hydrophobic substrates, mainly retinol and long-chain fatty acids, its physiological function is still unknown. In Exp. 1, we investigated the effect of beta-lg on the plasma retinol concentration in preruminant calves. Holstein male calves (n = 20) were fed Holstein whole milk at 40 g/kg body weight (BW) plus vitamin A acetate (500,000 i.u.) with or without beta-lg (0.4 g/kg BW). The plasma retinol concentration of 10-d-old calves was greater (P < 0.05) in the beta-lg-fed group) than in the control group during the period from 8 to 12 h and at 24 h after the feeding. The postprandial change of plasma retinol in 40-d-old calves fed milk with beta-lg was higher (P < 0.05) than that in the control calves only at 12 h after the feeding. In Exp. 2, Holstein male calves (n = 18) were used to investigate the effect of beta-lg on plasma triglyceride concentration and fatty acid composition. Calves were fed Holstein whole milk at 40 g/kg BW plus milk fat prepared from whole milk at 2 g/kg BW with or without beta-lg (0.4 g/kg BW). Plasma triglyceride concentration at age 10 d was higher (P < 0.05) in the beta-lg-fed group than in the controls during the periods from 1 to 2 h and from 7 to 11 h after the feeding. At age 40 d, plasma triglyceride in the beta-lg-fed group was higher (P < 0.05) than in the control group only at 9 h. Ratios of palmitic, stearic, and oleic acids to total plasma lipids were higher (P < 0.05) in the calves fed beta-lg milk than in the control calves at age 10 d. These results suggest that beta-lg enhances the intestinal uptake of retinol, triglyceride, and long-chain fatty acids in preruminant calves.     

Short communication: The preruminant calf as a model for characterizing the effects of vitamin D status in the neonate

The objective of this study was to evaluate the feasibility of using the preruminant dairy calf as a model for evaluating effects of vitamin D status in the neonate. Because the newborn calf can be sustained during the first weeks of life solely on a fluid diet having a defined composition, has documented nutritional requirements, and is minimally affected by repeated samplings of peripheral blood, it has the potential to serve as a model for characterizing nutrient-specific effects on the growth and health of the neonate. Colostrum-fed Holstein bull calves (n = 13) entered the trial at approximately 4 d of age. All calves were fed a custom-formulated milk replacer devoid of vitamin D. Plasma 25-hydroxyvitamin D₃ concentrations in all calves were determined on a regular basis beginning at d 0. Using this information, low- and high-status groups of calves were established by subcutaneous administration of 25-hydroxyvitamin D₃. To maintain targeted plasma 25-hydroxyvitamin D₃ concentrations in low (<30 ng/mL) and high (>60 ng/mL) vitamin D-status calves, low-status calves (n = 6) received a total of 8,600 IU (2,225 IU/wk) of vitamin D during the experimental period and high-status calves (n = 7) received 54,000 IU (13,500 IU/wk). Concentrations of 25-hydroxyvitamin D₃ in low-status calves averaged 27 ng/mL, compared with 78 ng/mL in high-status calves, and were less at all sampling times from d 7 to d 28. Concentrations of 1,25-dihydroxyvitamin D₃ and 25-hydroxyvitamin D₃ were not correlated. Calcium, magnesium, and phosphorous concentrations were unaffected by 25-hydroxyvitamin D₃ administration; however, plasma calcium and 1,25-dihydroxyvitamin D₃ concentrations were correlated. Calcium and magnesium concentrations decreased with age but remained within normal ranges for dairy cattle. These results indicate that it is possible to predictably control vitamin D status over a 28-d period and suggest that the preruminant calf might be useful as a model for studying effects of vitamin D on growth, development, and immune function in the neonate.     

Short communication: Fat-soluble vitamin and mineral status of milk replacer-fed dairy calves: Effect of growth rate during the preruminant period

Effects of growth rate on fat-soluble vitamin and macro- and micromineral concentrations in the circulation of preruminant dairy calves were evaluated. Dietary treatments were designed to achieve 3 targeted rates of gain [no growth (NG) = 0.0 kg/d; low growth (LG) = 0.55 kg/d; or high growth (HG) = 1.2 kg/d] over a 7-wk period. Milk replacer (MR) intakes necessary to achieve these growth rates were estimated using the National Research Council's Nutrient Requirements of Dairy Cattle calf model computer program. All of the calves were fed a 30% crude protein, 20% fat MR reconstituted to 14% dry matter. The diets were formulated to ensure that protein was not a limiting nutrient. No-growth and LG calves were supplemented additionally with vitamins A, D, and E to compensate for treatment differences in dry matter intake relative to the HG calves; however, no attempt was made to adjust mineral intake based on MR consumption. Growth rates for NG (0.11 kg/d), LG (0.58 kg/d), and HG (1.16 kg/d) calves differed during the study. Health was minimally affected by growth rate and this was reflected by comparable and relatively low serum haptoglobin concentrations in all calves during the 7-wk period. Concentrations of serum retinol, 25-(OH)-vitamin D₃, and zinc were unaffected by growth rate. The HG calves had lower RRR-α-tocopherol concentrations than NG and LG calves at wk 7, suggesting that the increased growth rate of HG calves was associated with increased utilization of vitamin E. Serum concentrations of all vitamins increased with age. Copper, calcium, and phosphorous concentrations in HG calves exceeded those in LG and NG calves during the latter weeks of the study, likely because of increased MR intake by HG calves. Fat-soluble vitamin and mineral concentrations for all treatment groups remained within ranges considered normal for preruminant calves.     

Tolerance of the preruminant calf for excess manganese or zinc in milk replacer

In two experiments, calves were fed milk replacer containing 40, 200, 500, 1000, or 5000 ppm Mn or 40, 200, 500, 700, or 1000 ppm Zn in DM, from 3 to 38 d of age, to estimate the minimum toxic concentrations of Mn and Zn. Starting at 1000 ppm Mn, weight gains and feed efficiencies were decreased slightly; none of the calves fed 5000 ppm Mn survived the 5-wk experiment. Liver and bile showed the largest increases in Mn concentration. In the Zn experiment, only at 700 and 1000 ppm Zn were weight gains, DM intake, and feed efficiency reduced. Largest Zn increases were in liver, kidney, and plasma. Thus, performance of the preruminant calves was not affected adversely by 500 ppm Mn or 500 ppm Zn in milk replacer, concentrations that are markedly higher than the NRC recommendations of 40 ppm Mn and 40 ppm Zn. However, Mn and Zn concentrations increased in some tissues, and toxicities might have arisen if the trial had been continued. Evidence was not obtained indicating that the calf benefits from Mn or Zn intakes above the NRC recommendations.     

Effects of an enhanced vitamin A intake during the dry period on retinoids, lactoferrin, IGF system, mammary gland epithelial cell apoptosis, and subsequent lactation in dairy cows

Studies in vitro show important interactions among vitamin A, lactoferrin, and insulin-like growth factor (IGF) binding proteins (IGFBP) and, thus, the IGF system. As a consequence, mammary gland epithelial cell proliferation and apoptosis during the bovine dry period and potential milk yield may be affected. We have studied effects of feeding vitamin A (550,000 IU/ d) that exceed daily requirements about 8-fold for up to 2 mo to dairy cows during the dry period on concentrations of retinol and its metabolites in plasma and milk, milk lactoferrin, plasma and milk IGF-I and IGFBP-3, lactoferrin and IGF-I mRNA levels in mammary gland tissue, mammary gland apoptosis, and 100-d milk yield in the ensuing lactation. In the group supplemented with vitamin A, the peripartal decrease of plasma retinol was delayed and attenuated, and colostral retinol plus retinylester concentration was enhanced, but colostral beta-carotene concentration decreased. The retinoic acid isomer 9,13-dicis retinoic acid that coeluted with 13-cis retinoic acid, was the predominant circulating retinoic acid and was higher in GrA than the control group. Plasma IGFBP-3 concentrations were positively correlated with plasma retinol concentrations (r = 0.51), but there were no group differences. Numbers of apoptotic epithelial cells in mammary epithelium were higher at drying off and parturition than in the middle of the dry period, coinciding with high concentrations of IGF-I and lactoferrin in mammary secretions. At parturition, numbers of apoptotic cells in mammary gland biopsies in cows supplemented with vitamin A were higher than in control cows. In conclusion, supplementation of dairy cows during the dry period with high amounts of vitamin A did not significantly modify concentrations of lactoferrin, IGFBP-3, and IGF-I in plasma and in mammary secretions, but slightly decreased energy-corrected 100-d milk yield and milk fat yield, possibly because of enhanced apoptic rates of mammary cells.     

Acute phase response elicited by experimental bovine diarrhea virus (BVDV) infection is associated with decreased vitamin D and E status of vitamin-replete preruminant calves

Studies in young animals have shown an association between vitamin deficiencies and increased risk of infectious disease; however, there is a paucity of information regarding the effect of acute infection on the vitamin status of the vitamin-replete neonate. To characterize the effects of acute infection on vitamin D and E status of the neonate, 6 vitamin-replete preruminant Holstein bull calves were experimentally infected with bovine viral diarrhea virus (BVDV; strain BVDV2-1373). Six mock-inoculated calves served as controls. Sustained pyrexia, leukopenia, and asynchronous increases in serum haptoglobin and serum amyloid A characterized the response of calves to infection with BVDV. Infection was also associated with increased serum IFN-γ, IL-2, and IL-6 concentrations. During the last 8 d of the 14-d postinoculation period, serum 25-hydroxyvitamin D and α-tocopherol concentrations in infected calves decreased by 51 and 82%, respectively. The observed inverse association between vitamin D and E status and serum amyloid A in infected calves suggests that the infection-induced acute phase response contributed to the reduced vitamin status of these animals. Additional studies are necessary to determine if the negative effect of infection on status are unique to this specific infection model or is representative of preruminant calf’s response to acute infection. Studies are also needed to characterize mechanisms underlying infection-related changes in vitamin D and E status and to determine whether additional vitamin D or E supplementation during an acute infection diminishes disease severity and duration in the young animal.     

Bovine vitamin A and beta-carotene intake and lactational status. 2. Responsiveness of mitogen-stimulated peripheral blood lymphocytes to vitamin A and beta-carotene challenge in vitro

The interaction of dietary vitamin A and beta-carotene with lactational status on the in vitro proliferation of mitogen-induced peripheral blood lymphocytes was studied. Cows were fed (IU/cow per d) 1) 53,000 IU vitamin A, 2) 213,000 IU vitamin A, or 3) 53,000 IU vitamin A plus 400 mg beta-carotene from 6 wk before to 2 wk after dry off. Lymphocytes were incubated with retinol, retinoic acid, or beta-carotene. Concanavalin A-induced blastogenesis was inhibited by 10(-6) M retinol and 10(-8) M retinoic acid in cows fed 53,000 IU vitamin A before dry off. In contrast, 10(-7) M retinol and 10(-7) M retinoic acid stimulated Concanavalin A-induced blastogenesis for cows fed vitamin A plus beta-carotene before dry off. After dry off, retinol and retinoic acid did not affect Concanavalin A-induced blastogenesis in all treatment groups. In vitro, 10(-5) M beta-carotene inhibited Concanavalin A-induced blastogenesis before and after dry off in all treatment groups. Blastogenesis in the absence of mitogen stimulation or induced by lipopolysaccharide was inhibited by all vitamins before and after dry off in all treatment groups. These data indicate that vitamin A and beta-carotene supplementation interact with lactational status to influence the responsiveness of bovine blood lymphocytes to vitamin challenge in vitro.     

Plasma retinol transport and clearance in hypervitaminosis A.

Effects of mild and severe hypervitaminosis A on retinol transport and clearance were studied in mature ewes. Excessive vitamin A intake was assoicated with high concentrations of vitamin A in plasma and liver, with elevated serum enzymes, with decreased feed consumption and packed cell volume, and with epithelial hyperplasia. Retinol transport in plasma increased 6- to 8-fold with excessive dietary vitamin A, was greater with mild hypervitaminosis A, and increased exponentially with vitamin A concentration in plasma. Clearance of retinol from plasma increased 2-fold with hypervitaminosis A, exhibited a greater response in the mild group, and increased linearly with vitamin A concentration in plasma. The relationship of clearance to vitamin A concentration in liver was described best by a power function. Retinol clearance represents a mechanism to maintain vitamin A concentration in plasma and may be most effective below vitamin A concentrations of 135 microgram/dl plasma. With severe hypervitaminosis A, massive vitamin A accumulates in liver leading to hepatic dysfunction and a resultant decrease in retinol clearance from plasma.     

Effects of d-α-tocopherol and dietary energy on growth and health of preruminant dairy calves

To observe the effects of supplemental dietary d-α-tocopherol in relation to dietary energy on growth and immune status in dairy calves, 32 newborn Holstein bull calves were assigned to 1 of 4 treatments for 5 wk in a 2 × 2 factorial, randomized complete block, split-plot design. Calves received moderate growth (MG) or low growth (LG) all-milk dietary treatments, formulated to support daily gains of 0.5 or 0.25 kg/d, respectively, per the dietary energy recommendation for milk-fed calves according to the National Research Council’s Nutrient Requirements of Dairy Cattle. Calves in both groups were either injected i.m. with Vital E-A+D (injectable solution of vitamins E, A, and D) on d 1 and supplemented with Emcelle Tocopherol (micellized vitamin E) via milk daily (MG-S and LG-S), or were not supplemented (MG-C and LG-C) during the study period. Total weight gain of MG calves was greater than that of LG calves and tended to be greater in MG-S calves than in MG-C calves. Calves receiving vitamin supplementation demonstrated greater concentrations of plasma α-tocopherol, retinol, and 25-(OH)-vitamin D than did control calves, whereas MG calves demonstrated a lower concentration of plasma α-tocopherol than did LG calves. The apparent increased utilization of α-tocopherol by MG calves was accompanied by a rise in serum haptoglobin, a positive acute-phase protein and indicator of inflammation, especially in MG-C calves. Serum amyloid A, also a positive acute-phase protein, was not different among groups, but was elevated from baseline in all groups during wk 1 through 3. Plasma IgG₁ concentrations were higher in MG-S and LG-S calves than in their nonsupplemented dietary counterparts, whereas plasma IgG₂, IgA, and IgM concentrations were not different among groups. In summary, dietary supplementation of d-α-tocopherol improved plasma α-tocopherol status and tended to increase growth in calves fed for 0.5 kg of average daily gain. Vitamin supplementation ameliorated the rise of serum haptoglobin associated with acute inflammation in MG calves, and may have improved passive transfer of maternal antibody. These results indicate a role for α-tocopherol in prevention of proinflammatory state associated with greater dietary energy and onset of infectious disease.     

Metabolism of vitamin K and influence on prothrombin time in milk-fed preruminant calves

The metabolism of vitamin K was studied in 66 preruminant veal calves that were fed supplemental menadione sodium bisulfite complex or phylloquinone. Menadione sodium bisulfite complex was converted by intestinal microorganisms to menaquinone-4 and absorbed and stored in the liver as menaquinone-4. Phylloquinone was absorbed unchanged. Production of menaquinones 6, 7, 8, and 10 by intestinal microorganisms also was observed, but was not dependent upon dietary vitamin K. No difference was noted in prothrombin time among the groups. Intestinal microorganisms provide sufficient vitamin K to meet the physiological needs of calves fed milk replacers. Menaquinone-4 was the form of vitamin K used to meet the calf's requirement.     

Effects of chronic environmental cold on growth, health, and select metabolic and immunologic responses of preruminant calves

The physiological response of the preruminant calf to sustained exposure to moderate cold has not been studied extensively. Effects of cold on growth performance and health of preruminant calves as well as functional measures of energy metabolism, fat-soluble vitamin, and immune responsiveness were evaluated in the present study. Calves, 3 to 10 d of age, were assigned randomly to cold (n = 14) or warm (n = 15) indoor environments. Temperatures in the cold environment averaged 4.7°C during the study. Frequent wetting of the environment and the calves was used to augment effects of the cold environment. Temperatures in the warm environment averaged 15.5°C during the study. There was no attempt to increase the humidity in the warm environment. Preventative medications or vaccinations that might influence disease resistance were not administered. Nonmedicated milk replacer (20% crude protein and 20% fat fed at 0.45 kg/d) and a nonmedicated starter grain fed ad libitum were fed to all calves. Relative humidity was, on average, almost 10% higher in the cold environment. Warm-environment calves were moderately healthier (i.e., lower respiratory scores) and required less antibiotics. Scour scores, days scouring, and electrolyte costs, however, were unaffected by environmental temperature. Growth rates were comparable in warm and cold environments, although cold-environment calves consumed more starter grain and had lower blood glucose and higher blood nonesterified fatty acid concentrations. The nonesterified fatty acid and glucose values for cold-stressed calves, however, did not differ sufficiently from normal values to categorize these calves as being in a state of negative-energy balance. Levels of fat-soluble vitamin, antibody, tumor necrosis factor-α, and haptoglobin were unaffected by sustained exposure to moderate cold. These results support the contention that successful adaptation of the dairy calf to cold is dependent upon the availability of adequate nutrition.     

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.     

Effects of prepartum supplementation of β-carotene on colostrum and calves

Little is known about transfer of dietary β-carotene into colostrum, its absorption by the calf, and its effects on retinol and α-tocopherol in the calf when the dam's dietary vitamin A is adequate. Our objective was to assess the effect of β-carotene supplementation during the close-up dry period on the colostrum and calf. The study was conducted on a large commercial dairy farm in Indiana during early summer of 2015. Ninety-four multiparous Holstein cows were blocked by calving data, parity, and previous production, and then randomly assigned to either control or β-carotene (BC) treatments. While locked in headgates each morning, each cow received a topdress of β-carotene (Rovimix, DSM Nutritional Products, 8 g/d; provided 800 mg β-carotene) or carrier from 21 d before expected calving until calving. Colostrum was collected within 2 h of parturition. Calf blood samples were obtained within 2 h of birth before receiving the dam's colostrum, at 24 h after birth, and at 7 d and 60 d of age. Blood serum was analyzed for β-carotene, retinol, α-tocopherol, and other metabolites and enzymes. Colostrum was analyzed for β-carotene, retinol, α-tocopherol, colorimetry profile, and milk components. Data were analyzed using mixed-effects models in SAS (SAS Institute Inc.). Calf serum β-carotene data were analyzed using the FREQ procedure. Colostrum β-carotene was higher for BC cows. Colostrum from BC cows had increased a* [measures red (positive) to green (negative)] and b* [measures yellow (positive) to blue (negative)] colorimeter values, indicating that β-carotene altered colostrum color toward red and yellow. Supplementation did not affect colostral or calf IgG concentrations. Colostrum color indices were correlated with IgG concentrations as well as concentrations of β-carotene, retinol, and α-tocopherol. Before receiving colostrum, the concentration of β-carotene in calf serum was below the detectable threshold of 0.05 μg/mL. At 24 h of age, the number of calves with detectable β-carotene concentrations increased, with more calves from BC cows (52.1%) having detectable concentrations than calves from cows in the control group (6.1%). No differences in concentrations of retinol or α-tocopherol were observed in calf serum. Supplementation of β-carotene to cows decreased activities of gamma-glutamyl transpeptidase and glutamate dehydrogenase in calf serum. In pregnant cows already receiving adequate vitamin A, supplementation of β-carotene increased concentration of β-carotene in colostrum, altered colostrum color, and increased serum β-carotene in calves at birth.     

Long-term effects of feeding gossypol and vitamin E to dairy calves.

Male Holstein calves were used to test the effect of feeding 400 mg of free gossypol/kg of diet and to determine whether vitamin E could counteract gossypol toxicity. Fifty-two calves were allotted to treatments as follows: 1) soybean meal-based starter; 2) cottonseed meal-based starter; 3) cottonseed meal-based starter + 2000 IU of vitamin E/d per calf, and 4) cottonseed meal-based starter + 4000 IU of vitamin E/d per calf. Vitamin E supplementation (treatments 3 and 4) improved weight gain and feed intake over calves on treatment 1. Gossypol concentrations in plasma were higher in calves on treatments 2, 3, and 4 than in calves on treatment 1; however, no differences were observed among animals receiving the three cottonseed meal diets. Hemoglobin and hematocrit were decreased in calves receiving treatment 2, and vitamin E supplementation counteracted this effect (treatments 3 and 4). Plasma alpha-tocopherol concentrations were not affected by gossypol intake and followed the vitamin E supplementation pattern During the experimental period, 10 calves died, six from treatment 2 and two each from treatments 3 and 4. Necropsy findings from 4 of 10 calves were suggestive of gossypol toxicity. Histopathological examination revealed centrilobular necrosis in the liver and atrophy and vacuolation of cardiocytes. Feeding cottonseed meal caused death of some calves with gossypol related toxicity signs, but did not decrease plasma alpha-tocopherol; however, vitamin E supplementation increased performance and may have conferred some protection against gossypol toxicity.     

Vitamin E requirements of dairy calves

Thirty-two Holstein heifer calves receiving conventional rations were supplemented with 0 (control), 125, 250, or 500 IU of vitamin E/calf per d. The objective was to determine the optimum requirement based on their overall performance from birth to 24 wk of age. Overall weight gains at 24 wk were higher with 125 and 250 IU and intermediate with 500 IU supplementation compared with no supplementation. Total dry feed consumption and fecal scores were similar among treatments. Serum alpha-tocopherol increased with increased supplementation in a quadratic fashion, being almost doubled with 125 IU compared with that of control calves. Serum creatine kinase, glutamic oxalacetic transaminase, and lactic dehydrogenase values in the unsupplemented calves indicated cell membrane damage. Serum glucose was higher at 8 wk in supplemented calves, but no differences among other serum metabolites were observed. Hematological responses at 4 and 8 wk of age indicated lower mean corpuscular hemoglobin in calves given 500 IU than others and lower mean corpuscular hemoglobin concentration in calves given 500 IU than in calves given 125 or 250 IU. We conclude that supplementation of conventional rations with 125 to 250 IU vitamin E/animal per d can increase the performance of calves.