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Carbohydrate-rich diets may increase urinary excretion of chromium (Cr) and increase its requirements. This study was conducted to investigate the effect of grain type (barley v. corn) and Cr supplementation on feed intake, feeding behavior and weight gain in dairy calves. Forty-eight neonatal Holstein female calves were assigned randomly to four experimental diets in a 2×2 factorial arrangement. Experimental diets were either barley-based diet (BBD) or corn-based diet (CBD) supplemented with (+Cr) or without (-Cr) Cr as Cr-methionine (0.05 mg/kg of BW0.75). Chromium was provided in milk (from days 3 to 73 of life) during the pre-weaning period and then in pre-warmed water (from day 74 until day 94 of life) after weaning. Meal length tended to increase in calves fed the BBD v. CBD during the pre-weaning period. During the post-weaning period, meal size, inter-meal interval, and eating rate increased concurrently but meal frequency and eating time decreased in the BBD v. CBD. During the pre-weaning period, feed efficiency, BW at weaning, and heart girth increased and non-nutritive oral behaviors tended to decrease with Cr supplementation. Due to increased meal frequency, the starter feed intake but not eating time increased by Cr supplementation during the post-weaning period. Supplementing Cr increased starter feed intake, final BW, average daily gain and heart girth during the overall period. Rumination time increased in BBD+Cr calves due to increases in the frequency and duration of rumination, or decreased rumination bout interval. Overall, the type of grain had no effect on feed intake and growth performance; however, Cr supplementation decreased non-nutritive oral behaviors and increased starter feed intake via increasing the meal frequency and thereby improved growth performance.

Stressful situations may result in serum chromium (Cr) depletion with increased urinary excretion of the mineral and increased Cr requirements. The objective of this study was to investigate the effects of Cr supplementation on growth performance, feeding behavior, blood metabolites and hormones, indicators of oxidative stress and glucose-insulin kinetics of summer-exposed weaned dairy calves. In total, 48 Holstein female calves (63 days of age; 77.0±1.45 kg of BW) were assigned randomly to one of two treatments: (1) a control group with no supplemental Cr (Cr-), and (2) a supplemental Cr group (Cr+) to supply 0.05 mg Cr as Cr-methionine/kg of BW0.75. Chromium was provided in the starter feed and adjusted weekly based on BW over the experimental period. All calves were on experiment for 4 weeks after weaning. The average maximum temperature-humidity index was 76.1 units during the study period, indicating a mild degree of environmental heat load. Results indicated that in summer-exposed dairy calves, increased dietary Cr provision tended to decrease fecal score, tended to change rumination pattern, increased antioxidant capacity by increasing serum concentration of catalase, but had no effects on growth performance, metabolic status or peripheral glucose and insulin metabolism.

The objective of this study was to determine the effect of supplemental chromium as chromium-L-methionine (Cr-Met) on productive and reproductive performances and some metabolic parameters in late gestation and early lactation of dairy cows. Sixty multiparous Holstein dairy cows according to prior lactation, parity, body mass (682±33 kg), and expected calving date were divided equally (30 cows/treatment) and were randomly allocated to one of the two groups. One group received basal diet without Cr (control group) and another group received Cr-Met supplement added at manufacturer's recommended level (8 mg of "Cr"/head per day) from 21 days before expected calving date until 21 days of lactation. Supplemental Cr tended to increase milk yield (P=0.08) while percentage of lactose and lactose yield increased (P<0.01). Chromium supplementation decreased serum nonesterified fatty acids concentration at 7 days prepartum and 21 days postpartum. Serum insulin concentration for cows receiving Cr was higher than the control group (P=0.05). Serum cortisol concentration decreased (P<0.05) in prepartum period in supplemented group. Chromium did not affect concentrations of metabolic parameters at calving. However, serum glucose concentration increased at 21 days postpartum in the supplemented group (P<0.05). Chromium supplementation increased neutrophil and neutrophil to lymphocyte ratio in prepartum period (P<0.05). Based on serum concentrations of progesterone, days to first ovulation tended (P=0.07) to occur earlier in the supplemented group. Furthermore, days to first service and days to first estrus of the supplemented group occurred earlier than the control group (P<0.05) but days open, services per conception and conception rates at first insemination did not differ between two groups (P>0.05). Percentage of cyclic cows at 36 days postpartum and estrous behavior before AI was higher in the supplemented group.

Metabolic demands of early lactation introduce enormous challenges to dairy cows when coincided with environmental stresses. The objective of this study was to determine effects of a chromium (Cr) supplement on feed intake and blood indicators of nutrient metabolism in early lactation cows in summer. Fifteen Holstein cows at 38±6 days in milk were grouped based on parity and randomly assigned to three supplemental doses of 0, 0.05 and 0.10 mg Cr/kg of BW(0.75) . Cows received a basal mixed ration with a forage to concentrate ratio of 57.7:42.3, twice daily at 09:00 and 16:00 h for 9 weeks. The first 2 weeks were for adaptation, and the following 7 weeks were for weekly sampling and data collection. The Cr supplement (a Cr-methionine product with 10% Cr and 90% Met from a compound containing one atom of Cr and three molecules of Met) was mixed with 100 g of ground corn and top dressed with the morning feed. The average ambient temperature-humidity index was 77.7 units during the study. Dry matter intake increased from 21.8 to 24.2 and 23.7 kg/day when 0.05 and 0.10 mg Cr/kg BW(0.75) was provided respectively. Milk output of energy, fat, protein and total solids increased by providing Cr at 0.05 mg but not 0.10 mg/kg BW(0.75) . Both doses of Cr increased milk protein content, but the higher Cr dose reduced feed efficiency compared with control. While rectal temperature and body condition score were unaffected, cows receiving 0.05 mg and not 0.10 mg Cr/kg BW(0.75) tended to have greater respiration rate than control cows. Blood insulin and non-esterified fatty acids concentrations and the insulin to glucagon ratio decreased, and serum albumin increased when cows received 0.05 mg of Cr/kg BW(0.75) . Blood glucose, glucagon, insulin-like growth factor-1, total protein, globulins, urea, BHBA, triglycerides, cholesterol, cortisol, progesterone, and high- and very low-density lipoproteins were not affected. Therefore, supplemental Cr supply at 0.05 and 0.10 mg/kg BW(0.75) improved feed intake, only at 0.05 mg/kg BW(0.75) increased milk secretion, and mainly at 0.05 mg/kg BW(0.75) altered peripheral nutrient metabolism in early lactation Holstein cows under high ambient temperatures., (© 2010 Blackwell Verlag GmbH.)

Holstein cows (n = 72) entering second or later lactation were used to determine whether metabolic indices and hepatic capacities for oxidation and gluconeogenesis from propionate are affected by source of carbohydrate in the prepartum diet and chromium-l-methionine (Cr-Met) supplementation throughout the periparturient period. Cows were fed prepartum diets as total mixed rations with the concentrate portion based either on starch-based cereals [high nonfiber carbohydrate (NFC); 1.59 Mcal/kg of net energy for lactation (NE(L)), 14.4% crude protein (CP), 40.3% NFC] or nonforage fiber sources (low NFC; 1.54 Mcal/kg of NE(L), 14.5% CP, 33.6% NFC) from 21 d before expected parturition until parturition. After parturition all cows were fed a common lactation total mixed ration (1.74 Mcal/kg of NE(L), 16.5% CP, 40.0% NFC). The Cr-Met was supplemented once daily via gelatin capsule at dosages of 0, 0.03, or 0.06 mg of Cr/kg of BW(0.75). Thus, treatments were in a 2 (carbohydrate source) x 3 (Cr-Met) factorial arrangement. There was no effect of prepartum carbohydrate source on pre- and postpartum plasma concentrations of glucose, nonesterified fatty acids (NEFA), beta-hydroxybutyrate (BHBA), insulin, glucagon, or insulin to glucagon ratio. However, cows fed the low NFC diet during the prepartum period tended to have greater plasma NEFA and lower BHBA concentrations postpartum. Liver glycogen concentrations tended to be greater on d 1 postpartum for cows fed low NFC prepartum. Supplementing 0.03 mg/kg of BW(0.75) of Cr as Cr-Met increased prepartum plasma glucose and glucagon concentrations and tended to decrease prepartum plasma NEFA concentrations compared with either 0 or 0.06 mg of Cr/kg of BW(0.75). Postpartum plasma glucose concentrations decreased linearly and glucagon concentrations were increased quadratically by administering increasing amounts of Cr-Met. Supplementing Cr-Met did not affect prepartum plasma concentrations of insulin or BHBA, postpartum NEFA or BHBA, or liver composition. There was an interaction of prepartum carbohydrate source and Cr-Met supplementation such that in vitro hepatic conversion of [1-(14)C]propionate to both CO(2) and glucose was similar or increased when Cr-Met was supplemented to cows fed the low NFC diet but decreased when Cr-Met was supplemented to cows fed the high NFC diet. Insulin addition in vitro did not affect hepatic metabolism of propionate on d 1 postpartum. Overall, both the NFC content of the prepartum diet and Cr-Met had only modest effects on metabolic indices in this experiment.

Ruminal administration of a triple indigestible marker system comprised of cobalt EDTA (CoEDTA), ytterbium acetate (YbAc), and chromium-mordanted straw (CrS) decreases product:substrate ratios for Delta9-desaturase in bovine milk fat. This experiment was designed to identify the marker(s) responsible and develop an alternative system for simultaneous determination of nutrient flow in the gastro-intestinal tract and milk fatty acid composition. Five lactating dairy cows were used in a 5 x 5 Latin square with 21-d periods to evaluate the effects of YbAc, CoEDTA, and CrS independently or as part of a triple marker system (TMS), and CrEDTA as an alternative to CoEDTA on milk fat composition. Markers were administered in the rumen over a 7-d interval and samples of milk were collected on d -1, 3, 7, and 11. Both TMS and CoEDTA alone reduced the concentrations of milk fatty acids containing a cis-9 double bond, whereas YbAc, CrS, and CrEDTA had no effect. Reductions in product:substrate ratios for Delta9-desaturase were time dependent and evident within 3 d of administration. Ruminal infusion of CoEDTA for 7 d induced mean decreases in milk cis-9 14:1/14:0, cis-9 16:1/16:0, cis-9 18:1/18:0, and cis-9, trans-11 conjugated linoleic acid/trans-11 18:1 concentration ratios of 47.7, 26.7, 40.3, and 42.6%, respectively. In conclusion, ruminal infusion of CoEDTA alters milk fatty acid composition and appears to inhibit Delta9-desaturase activity in the bovine mammary gland. Results indicate that a TMS based on CrEDTA, YbAc, and indigestible neutral detergent fiber can be used for estimating nutrient flow without altering milk fat composition in lactating cows.

Accurate determination of the flow of nutrients at the omasum requires the use of a triple marker system. Typically, a system based on ruminal administration of the lithium salt of CoEDTA, ytterbium acetate (Yb-Ac), and chromium-mordanted straw (Cr-S) has been used. However, there is evidence to suggest that product:substrate ratios for stearoyl-coenzyme A desaturase (Delta(9)-desaturase) are lower in milk fat from cows administered a combination of CoEDTA, Yb-Ac, and Cr-S, indicating reduced Delta(9)-desaturase activity. To evaluate this hypothesis, samples of milk were collected 1 d before, and on d 2, 6, and 9 of administering the CoEDTA, Yb-Ac, and Cr-S triple marker system into the rumen of 4 cows. A 4 x 4 Latin square with 28-d experimental periods was used to assess the effects of 0, 75, 150, and 300 g/d of fish oil in the diet on ruminal and mammary lipid metabolism. Irrespective of the amount of fish oil in the diet, concentrations of all milk fatty acids containing a cis-9 double bond were reduced after markers were given. Milk fatty acid pairs dependent on Delta(9)-desaturase were decreased over time, with responses reaching a nadir within 6 d of marker administration. Overall, administering markers into the rumen was associated with a mean decrease in milk cis-9 10:1/ 10:0, cis-9 12:1/12:0, cis-9 14:1/14:0, cis-9 16:1/16:0, cis-9 17:1/17:0, cis-9 18:1/18:0, and cis-9,trans-11 conjugated linoleic acid/trans-11 18:1 concentration ratios of 44.6, 52.7, 58.7, 36.8, 37.2, 44.3, and 43.0%, respectively. In conclusion, one or more of the markers administered altered milk fatty acid composition and may act as an inhibitor of Delta(9)-desaturase in the bovine mammary gland.

Holstein cows (n = 72) entering second or later lactation were used to determine whether productive performance and dry matter intake (DMI) are affected by carbohydrate source in the prepartum diet and chromium-L-methionine (Cr-Met) supplementation throughout the periparturient period. Cows were fed either a TMR with the concentrate portion based on starch-based cereals [high nonfiber carbohydrate (NFC); 1.59 Mcal/kg of net energy for lactation (NEL), 14.4% crude protein (CP), 40.3% NFC] or a TMR with the concentrate portion based on nonforage fiber sources (low NFC; 1.54 Mcal/kg NEL, 14.5% CP, 33.6% NFC) from 21 d before expected parturition until parturition. After parturition all cows were fed a lactation TMR (1.74 Mcal/kg NEL, 16.5% CP, 40.0% NFC). The Cr-Met was supplemented once daily via gelatin capsule at dosages of 0, 0.03, or 0.06 mg of Cr/kg of metabolic body weight. Thus, treatments were in a 2 (carbohydrate source) x 3 (Cr-Met) factorial arrangement. Neither prepartum nor postpartum DMI was affected by prepartum dietary carbohydrate source. Administering increasing amounts of Cr-Met linearly increased milk yield and, subsequently, postpartum DMI. Prepartum carbohydrate source did not affect postpartum milk yield; however, cows fed the low NFC diet tended to yield milk with a lower content of total solids. These data indicate that prepartum carbohydrate source has little influence on performance during the immediate peripartal period, and that increases in milk yield for cows supplemented with Cr-Met are independent of prepartum dietary carbohydrate source.

Two hundred thirty-two primiparous and multiparous cows were assigned to a study to determine the effect of supplementing 0 or 6.25 mg/d of Cr from Cr Met on lactation and reproductive performance. Cows received treatments from 6 wk precalving through 21 wk postpartum. Precalving, treatments were incorporated into a pelleted grain mixture and group-fed. Post-calving, cows received treatments via an individual oral drench once a day after the a.m. milking. Grazed herbage was the primary diet constituent for lactating cattle. Blood was collected from a predetermined group of cows before and immediately after calving. On 4 occasions during the treatment period, milk yield was recorded and samples collected for determination of composition. Chromium supplementation had no effect on yield of milk and milk components and milk composition. Chromium supplementation decreased serum nonesterified fatty acids (NEFA) concentration (0.60 vs. 0.68 mmol/L), with chromium supplementation having the greatest impact on serum NEFA concentrations at 1 wk prepartum. Greater percentages of cows supplemented with Cr were observed to be anestrus by dairy personnel (45.5 vs. 32.0%). However, Cr supplementation tended to increase the percentage of cows pregnant in the first 28 d of the mating season (50.0 vs. 39.2%). Results indicate that Cr Met supplementation of intensely grazed, late-gestation and early-lactation dairy cattle decreased serum NEFA concentrations and tended to increase pregnancy rates in the first 28 d of the mating season.

The effect of supplemental chromium as chromium-methionine (Cr-Met) on production and metabolic parameters was investigated in 48 cows from 28 d before expected calving date through 28 d of lactation. Average body weight (BW) was 730 +/- 61 kg before treatment. Treatments were supplementation of 0, 0.03, 0.06, and 0.12 mg of Cr as Cr-Met/kg of BW(0.75). Dry matter intake increased linearly and quadratically during the prepartum and postpartum periods, respectively, and body condition score loss decreased linearly during the postpartum period with increasing Cr-Met. Increasing Cr-Met supplementation caused quadratic increases in milk, fat, and lactose yields. Treatments did not affect concentrations of blood metabolites and liver triglyceride. Serum insulin concentration and molar ratio of insulin to glucose for cows receiving Cr-Met were lower than for cows not receiving Cr-Met, but they increased quadratically with increasing Cr-Met. Glucose tolerance tests (GTT) were conducted on d 10 prepartum and d 28 postpartum. Chromium-methionine supplementation attenuated insulin sensitivity prepartum and enhanced glucose tolerance postpartum, but not prepartum. Basal insulin concentrations for cows receiving Cr-Met were higher than for cows not receiving Cr-Met during the prepartum GTT. During the postpartum GTT, peak glucose concentration and clearance rate decreased and half-life (t(1/2)) and time to reach basal concentration (T) were prolonged quadratically by increasing Cr-Met. Additionally, peak insulin concentration, area under the curve, and molar ratio of insulin to glucose were higher for cows not receiving Cr-Met than for cows receiving Cr-Met and t(1/2) and T were shortened quadratically by increasing Cr-Met.

Two groups of 12 young bulls, as similar as possible with respect to age and weight, were fed a basic diet of hay and concentrates ad libitum for 170 days. The concentrate fed to one of the groups was supplemented with 0.20 mg of organic chromium per kg DM from a fodder yeast product so that the concentration of chromium in the total dry matter of their diet was 0.90 mg/kg, compared with 0.72 mg/kg in the diet of the control group. No significant differences were observed between the two groups of animals in terms of either their daily weight gain or any of the parameters of carcass quality examined. It is therefore concluded that in Sweden there is no reason to add chromium routinely to the diet of intensively fed, growing bulls.

Twenty-four Holstein bull calves were fed a milk replacer diet to assess the effects of Cr on calf performance and metabolism of glucose. Treatments consisted of no supplemental Cr (control) or 0.4 mg/kg of dry matter of supplemental Cr from CrCl3 or from a Cr-nicotinic acid complex. Supplementation with the Crt-nicotinic acid complex increased the average daily gain and feed efficiency from d 28 to 42, but not over the entire 63-d performance phase. Calves that were fed diets supplemented with CrCl3 or the Cr-nicotinic acid complex had lower plasma glucose concentrations at 45 to 180 min after an i.v. infusion of insulin than did controls. Calves fed diets supplemented with the Cr-nicotinic acid complex also had lower plasma glucose concentrations from 90 to 180 min after insulin challenge than did calves that were fed diets supplemented with CrCl3. After an i.v. infusion of glucose, calves that were fed diets supplemented with CrCl3 had lower serum insulin concentrations at 10 to 25 min after challenge than did controls or calves that were fed diets supplemented with the Cr-nicotinic acid complex. However, the glucose clearance rate after glucose infusion was not affected by Cr supplementation. Chromium supplementation did not markedly affect the performance of calves, but the Cr-nicotinic acid complex and CrCl3 did intensify the response to insulin administered i.v.

Forty-eight Angus crossbred steers (263 +/- 2 kg initial BW) were blocked by weight and randomly assigned within weight group to treatment. Treatments consisted of control or .4 mg of supplemental Cr as Cr-nicotinic acid complex/kg of DM. Steers were fed diets containing 90% corn silage (DM basis) and 10% of a soybean meal-mineral-vitamin supplement. After 56 d on the dietary treatment, half of the steers in each treatment were transported 343 km and unloaded in an unfamiliar location. The next day, d 58, shipped steers were returned to the feedlot (50 km). On d 58 after shipped steers were returned to the feedlot, all steers were inoculated with infectious bovine rhinotracheitis virus (IBRV) intranasally. Average daily gain from d 0 to 80 was increased (P < .10) by supplemental Cr. There was a shipping x time interaction for serum cortisol concentrations. Shipping increased (P < .02) serum cortisol on d 58, but 7 d after transport there were no effects of shipping on serum cortisol. Transportation increased (P < .05) the ratio of neutrophils to lymphocytes. Supplemental Cr did not affect rectal temperature after the IBRV challenge or the antibody response to IBRV or porcine red blood cells. Immunoglobulin G antibody response to porcine red blood cells was decreased (P < .09) by shipping. Supplemental Cr as Cr-nicotinic acid improved ADG of growing steers, regardless of whether they had been stressed by shipping. Supplemental Cr did not affect any of the immune responses that were measured.

This study determined whether supplementing the diets of dairy cows during the peripartum period with organic trivalent Cr influenced the capacity of their peripheral blood mononuclear cells to produce activation cytokines in response to stimulation with mitogens in vitro. Nine cows were fed 0.5 ppm of Cr/d per cow from 6 wk prepartum to 16 wk postpartum; 10 other periparturient cows served as unsupplemented controls. Mononuclear leukocytes, enriched from peripheral blood during wk 0, 2, 4, and 6 of lactation, were cultured with or without the T-lymphocyte mitogen, concanavalin A. Culture supernatants, harvested at 24, 48, or 72 h, were assayed for interleukin-2, interferon-gamma, and tumor necrosis factor-alpha. The cytokines were barely detectable in the supernatants from the unstimulated cultures, but supernatants from mitogen-stimulated cultures contained higher concentrations of each cytokine. For cows fed Cr, concentrations of all three cytokines in the culture supernatants of the mitogen-stimulated mononuclear cells decreased significantly relative to values for unsupplemented cows, particularly around peak lactation for the 24- and 48-h cultures. Theses results extended our previous observations and supported the hypothesis that organic Cr is immunomodulatory in high producing cows.

Our previous research showed enhanced immune responses, including mitogen-induced blastogenesis of peripheral blood mononuclear cells from feedlot calves and periparturient dairy cows supplemented with dietary chromium (Cr). The objective of the present study were to test whether blood sera from Cr-supplemented periparturient cows contained immunomodulatory activity for mitogen-stimulated peripheral blood mononuclear cells and, if so, to determine if this activity was explicable by differences in blood profiles of some glucose-regulating hormones (insulin, cortisol, growth hormone, insulin-like growth factor I, and tumor necrosis factor-alpha) between Cr-supplemented and unsupplemented (control) animals. Blood sera from ten unsupplemented cows and nine Cr-supplemented cows (0.5 ppm day-1) were collected weekly from 2 weeks before to 6 weeks after parturition, and were used to supplement (1, 10, and 20% vol/vol) culture medium supporting concanavalin A (Con A) stimulated mononuclear cells enriched from blood of four nulliparous donor cows. Hormone concentrations were determined using radioimmunoassays. Con A-induced blastogenesis was enhanced when 1, 10, and 20% sera from Cr-supplemented cows was added to the mononuclear cell cultures, and this was particularly evident around parturition. Conversely, peripartum sera from unsupplemented cows depressed Con A-induced blastogenesis. Except for a marginal rise in blood cortisol 2-4 weeks after parturition, no significant effects of Cr supplementation on other hormones (insulin, growth hormone, insulin-like growth factor I, tumor necrosis factor-alpha) were observed. These observations suggest that factors in peripheral blood serum from Cr-supplemented cows, other than absolute concentrations of the glucose-regulating hormones studied, modulate Con A-induced blastogenesis of mononuclear leukocytes.

Holstein calves, 10 steers (98 +/- 16 kg; Exp. 1) and 14 heifers (122 +/- 7 kg; Exp. 2), were fed either corn-cottonseed hull basal diets (CON; 15.1 and 13.2% CP, respectively) or CON plus 370 micrograms/kg of Cr as Cr-tripicolinate (CrP). After either 58 (Exp. 1) or 56 (Exp. 2) days of ADG and DMI measurement, calves were individually fed 1.4% of their BW every 12 h through the end of each experiment. Nitrogen balance, i.v. glucose tolerance tests (IVGTT), i.v. insulin challenge tests (IVICT), baseline growth hormone (GH) measurements, and GH-releasing hormone challenges were then performed on calves in split groups on d 70 through 87 in Exp. 1. In Exp. 2, all challenges began on d 78 and N balance was not determined. Inclusion of CrP did not affect (P > .10) ADG, DMI, or ADG/DMI of pooled data from Exp. 1 and 2 or N balance criteria in Exp. 1. Plasma glucose, insulin, and NEFA concentrations were not affected (P > .10) by CrP. Total plasma cholesterol was lower (P < .05) for CrP- than for CON-fed calves at wk 4 in Exp. 1 and wk 6 in Exp. 2. During IVGTT, calves fed CrP vs CON had higher (P < .05) clearance rates for glucose in Exp. 1 (2.68 vs 1.88%/min) and in Exp. 2 (2.64 vs 2.08%/min). During IVICT, calves fed CrP vs CON had higher clearance rates for glucose in Exp. 1 (2.98 vs 2.34%/min; P = .12) and in Exp. 2 (2.89 vs 2.00%/min; P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

The objective of this study was to determine the effect of supplemental dietary chromium (Cr) on antibody responses of feedlot calves. Fifty-five newly weaned calves were divided into two groups, 28 that received supplemental Cr and 27 that did not, and were immunized with a commercial vaccine against bovine infectious rhinotracheitis virus (IBR) and bovine parainfluenza virus type 3(PI-3). Sera harvested from blood sampled preimmunization, and at days 14 and 28 postimmunization (PI), were assayed for anti-IBR and anti-PI-3 antibody titers. Individual calves were also scored as seroconverters if day 14 or 28 PI titers were > or = 3 times the value of the preimmunization titer. Thirty-five calves did not seroconvert to either antigen. Of 20 IBR seroconverters, 15 calves were from the Cr-supplemented group while only five calves were controls (p = 0.007). There was no treatment difference in the number of PI-3 seroconverters. Least squares analysis of actual antibody titers revealed that Cr supplementation increased the magnitude of the peak antibody response to the IBR (p = 0.003), but had no effect on anti-PI-3 antibody titers. These data confirmed and extended our previous observations that supplemental Cr can be immunomodulatory in cattle.

The objective of the present study was to determine the effects of supplemental dietary chromium on immune responses of dairy cows subjected to physical and metabolic stresses associated with late pregnancy, calving, early lactation, and peak milk yield. Nine periparturient dairy cows were supplemented with chelated Cr (.5 ppm/d) from 6 wk prepartum (wk -6) through 16 wk postpartum (wk 16), and 10 cows were unsupplemented controls. To assess humoral immune responses, all cows were immunized with ovalbumin (OVA; s.c.) and human erythrocytes (HRBC; i.v.) on wk -2 and 2, and sera from weekly blood samples were assayed for content of antigen-specific antibody. Cell-mediated immunity was assessed in vitro using antigen (OVA)- and mitogen-stimulated peripheral blood mononuclear cell (PBMC) blastogenesis of cells collected biweekly from wk -2 and 6. Supplemental Cr caused anti-OVA antibody responses (P < .01) and mitogen-stimulated blastogenic responses of PBMC (P = .05) to be elevated, was associated with lowered OVA-stimulated blastogenic responses of PBMC (P < .01), and had no overall effect on antibody responses to HRBC (P > .10) relative to responses of control cows. These results confirmed and extended our previous observations that supplemental Cr can alter specific immune responses of stressed cattle.

The effects of supplemental chromium (Cr) from high-Cr yeast were investigated with steer calves fed corn silage diets. One hundred eight Charolais-crossed calves, weighing 245 kg after marketing and transport, were allotted to one of four treatments during the initial 28-d stress period: control, .4 ppm of Cr in the diet, long-acting injectable oxytetracycline (LAOTC), and Cr + LAOTC. Those fed Cr received 4 mg of Cr/d for the first 3 d sprinkled onto a small amount of hay over the silage. Chromium without LAOTC increased (P less than .05) ADG by 30% (.61 vs .79 kg/d) and ADG/DMI by 27% (.123 vs .156). Oxytetracycline alone increased (P less than .05) ADG by 30% and DMI by 15%. Chromium had no effect on morbidity. However, LAOTC tended (P less than .14) to reduce morbidity (26.0 vs 14.0%) after its administration. After d 28, steers were processed. Two weeks later, they were rerandomized within Cr groups to urea-corn vs soybean meal supplementation of corn silage during a 70-d growing period. Level of Cr was reduced to .2 ppm. Jugular blood was collected from eight steers on each treatment on two occasions. Chromium had no effect on ADG or ADG/DMI. However, Cr decreased (P less than .05) serum cortisol (75.0 vs 55.6 nmol/L). Furthermore, Cr increased (P less than .05) serum immunoglobulin M and total immunoglobulins in calves fed diets with soybean meal but had no effect in calves with urea-corn supplementation.(ABSTRACT TRUNCATED AT 250 WORDS)

Six ruminally fistulated crossbred steers (BW = 369 kg) were used in a randomized complete block experiment to test the efficacy of continuous-infusion pumps and controlled-release boluses for administering external markers to predict fecal output. Steers, limit-fed chopped alfalfa hay at 2% of BW daily, were fitted with continuous-infusion pumps that administered Co-EDTA and YbCl3 solutions intraruminally. In addition, a controlled-release bolus containing Cr2O3 was inserted into the rumen of each steer. Fecal grab samples were taken every 6 h for 7 d during initial marker equilibration; after this period, fecal grab samples were taken every 3 h for 48 h to evaluate diurnal variation patterns. Steers were subsequently fitted with fecal bags for 7 d to allow total fecal collection. Grab samples also were taken during the total fecal collection period at 0600 (AM) and 1400 (PM). The marker X time effect was nonsignificant. Similarly, time of grab sampling (AM or PM) did not affect estimates of fecal output (P greater than .10), but the Cr2O3 bolus overestimated fecal output (P less than .05). Fecal marker concentrations during the 48-h profile showed little diurnal variation regardless of marker used. All markers equilibrated in the feces at approximately 100 to 120 h after initiating infusions. The continuous-infusion pumps evaluated were efficacious for administering markers for estimating total fecal output in limit-fed steers; however, the Cr2O3 boluses evaluated overestimated fecal output when the manufacturer's suggested release rate was used for fecal output calculations.