The isotope dilution technique of [6-3H]glucose, [U-14C]lactate and [l-14C]propionate was used to evaluate the effect of dietary chromium (Cr) supplementation on whole-body kinetics of glucose, lactate, and propionate in rams. Rams were fed a high grain diet at 2% of body weight with or without 0.5 ppm of supplemental Cr from chelated Cr for the initial 14 days, and then intake was increased to 2.5% at body weight for the last 9 days. Weight gain was enhanced (P < 0.01) with Cr supplementation. Plasma concentrations of glucose, lactate, and propionate were not influenced by Cr supplementation. Turnover rates of glucose and lactate, and their interconversion were also not influenced. Propionate turnover rate tended to increase (P = 0.11) and the conversion of propionate to glucose increased (P < 0.05) with Cr supplementation, leading the increased proportional contribution of propionate to glucose turnover rate (P < 0.05). Chromium supplementation may influence the contribution of each glucogenic substrate for glucose production in rams fed a high grain diet.

Chromium was identified 40 years ago to be an essential mineral for laboratory animals. Chromium has been deemed an essential nutrient based on experimentally induced deficiencies in laboratory animals and clinically observed changes in the health of humans. The most commonly observed symptoms of chromium deficiency in humans include impaired glucose tolerance, insulin resistance and elevations in serum insulin, cholesterol and total triglycerides, the long-term effects of which increase risk of maturityonset diabetes, cardiovascular diseases and hypertension. In laboratory animals, in addition to the above-listed manifestations, there are also decreased longevity, decreased reproductive functions, impaired growth and other adverse effects. All of these clinical symptoms can be reduced or possibly even prevented by organic chromium supplementation to the diet.

Two trials were conducted to investigate the effects of supplemental chromium (Cr) from organic sources (Cr chelate and high Cr yeast) on antibody responses of newly arrived feeder calves following vaccination with infectious bovine rhinotracheitis (IBR), para-influenza-3 (PI3), bovine respiratory syncytial virus (BRSV), bovine viral diarrhea (BVD) and Pasteurella haemolytica and ovalbumin (OVA). Using cross bred steer calves purchased at sales in Ontario, vaccines and OVA were given on d 0 and 21 after arrival in the feedlot. Immune responses of calves were measured as serum specific antibody titres against all antigens on d 0 and 28 or d 35. The anti-OVA antibody responses (trial 2) were further investigated by measuring antibody concentrations of calves weekly until d 55 after arrival in the feedlot. Supplemental Cr (0.14 ppm) from an amino acid-chelated source had no effect on antibody responses to IBR, P13 and BRSV, but enhanced (P < 0.05) antibody titres of calves in response to the BVD vaccine on d 28 or d 35. Supplemental Cr from Cr yeast had no effect on antibody titres of calves to any vaccines. Chromium from both sources (trial 1 and 2) had no effect on antibody responses of calves following vaccination with P. haemolytica. However, supplemental Cr (0.75 ppm) from Cr yeast enhanced (P < 0.05) serum antibody responses of calves to OVA during the primary response (d 14) and secondary response (d 35) following immunization. These data confirmed our previous finding that supplemental Cr can enhance humoral immune response of market-transit stressed calves, but its enhancement on vaccine efficacy was antigen-dependent and variable.

Two studies were conducted to evaluate the effects of Cr supplementation on blood metabolite and hormonal responses of Holstein cows to glucose challenges during late pregnancy and early lactation and to propionate challenges during early lactation. Eight multiparous and 4 primiparous cows (Experiment 1) and 12 primiparous cows (Experiment 2) were assigned to one of two treatments: control and 0.5 ppm of supplemental Cr. The glucose challenges were performed at 2 wk prepartum and at 2 wk postpartum, and the propionate challenges were conducted at wk 2 and 6 postpartum. During glucose tolerance tests, Cr supplementation reduced the ratio of insulin to glucose and reduced plasma concentrations of insulin and triglycerides of primiparous cows during the prepartum period. Chromium supplementation decreased plasma Cr of primiparous cows following glucose challenge. With supplemental Cr, insulin sensitivity was reduced postpartum, particularly for primiparous cows, but insulin sensitivity was increased prepartum. Results of this study suggested that primiparous cows experienced Cr deficiency during late pregnancy and possibly during early lactation. Following propionate infusion, Cr supplementation increased the serum glucose peak, increased the area under the response curve for serum glucose, and tended to increase IGF-I concentrations. Chromium supplementation tended to reduce the ratio of insulin to glucagon. Supplementation might have enhanced gluconeogenesis or glycogenolysis. Supplemental Cr also resulted in reduced variability of most parameters during both experiments.

The objective of this study was to determine the effects of supplemental dietary chromium (Cr) on health status and mastitis-related parameters, as well as neutrophil phagocytic activity of dairy cows during late pregnancy and early lactation. In addition, possible interactions and involvements of Cr with insulin, cortisol, somatotropin (rBST) and insulin-like growth factor-1 (IGF-1) were directly investigated in vitro based on blastogenic responses using peripheral blood lymphocytes (PBL) of eight cows fed the control diet. Forty pregnant Holsteins, 18 primiparous and 22 multiparous, at week (wk) 6 before the expected calving dates were randomly assigned to treatments: control and supplemental chelated Cr (0.5 ppm) in the diet. All cows were managed in a normal production operation and health status was assessed by recording the incidence of health problems during the experimental period of wks 6 before and 16 after calving (-6 to 16 wks). Mastitis-related parameters included somatic cell counts (SCC), bacterial colony counts of milk samples from each mammary gland quarter of all cows during wk 1 to wk 8 postpartum. Peripheral blood neutrophil phagocytic function of eight cows fed either control or supplemental Cr diet was determined by the ability to take up uniform fluorescent beads measured by flow cytometry. Supplemental Cr had no effect (P > 0.10) on health status of cows during late pregnancy and early lactation, or on SCC and bacterial colonies of quarter milk samples from early lactation (wks 1 to 8). Supplemental Cr also did not affect neutrophil phagocytic function of cows from 6 wks prepartum to 6 wks postpartum. However, in the in vitro study of PBL (from control animals, not fed Cr diet) blastogenesis with addition of insulin or cortisol at two levels (0.05 and 0.5 ng ml-1), insulin and cortisol enhanced or had no effect on PBL proliferations with or without concanavalin A (con A) simulation. However, further Cr addition in the culture medium containing supplemental insulin or cortisol, particularly CrCl3, additively increased (P < 0.05) BPL blastogenic activities with or without con a stimulation. Conversely, addition of rBST or IFG-1 (0.5 and 5.0 ng ml-1) in the culture medium enhanced PBL proliferation, but addition of Cr gave no additional effect. These results indicated that supplemental Cr had no beneficial effect on health status, mastitis-related parameters or neutrophil phagocytic activity of dairy cows. However, in vitro study confirmed and extended our previous observations that Cr has an effect on lymphocyte proliferation and this may associate with insulin or cortisol actions.

Two experiments were conducted to evaluate the effects of chromium (Cr) supplementation on early lactation performance of Holstein cows. Experiment 1 involved 12 primiparous (PP) and 22 multiparous (MP) cows, while exp. 2 involved 18 PP and 22 MP cows. In each trial, cows were fed total mixed rations (TMR) and assigned to one of two treatments: control or 0.5 mg kg−1 supplemental chelated Cr from week 6 prepartum to week 16 postpartum The cortisol response to synthetic adrenocorticotropin (ACTH) intramuscular (i.m.) and the luteinizing hormone (LH) response to synthetic gonadotropin-releasing hormone (GnRH) i.m. were evaluated as well, during weeks 2 and 6 postpartum in exp. 2 During the first 16 wk of lactation, supplemental Cr tended to increase milk yields in PP cows by 13% (P = 0.06) and increased milk production by 7% (P < 0.05) in exps. 1 and 2, respectively, but had no effect in MP cows. Despite increased milk yield, Cr supplementation had no adverse effect on milk composition, reproductive performance, or health status. Furthermore, Cr supplementation tended to increase the milk lactose content in PP cows. Supplemental Cr reduced serum β-hydroxybutyrate levels and may reduce subclinical ketosis in MP cows. In addition, in overconditioned, aged cows, Cr supplementation may reduce the incidence of certain other metabolic disorders. Peak values and production rates of cortisol in Cr-supplemented cows tended to be greater (P < 0.10) than in control cows at week 6 Basal LH concentrations did not differ between the two treatments for either week However, the Cr-supplemented cows released less (P < 0.05) LH than did control cows at week 6. Results from hormonestimulation tests suggest that the Cr-supplemented cows may have experienced a greater stress with their increased milk production. However the time in postpartum anestrus and the time to conception were similar, suggesting that Cr supplementation may have mitigated the slower return to fertility usually seen in higher producing PP dairy cows. Further study is needed to determine the effects of Cr supplementation on reproductive performance, health status, and metabolic disorders in dairy cows. Key words: Chromium, milk production, luteinizing hormone, cortisol, reproduction, dairy cows

The effects of supplemental inorganic chromium (Cr) and (or) nicotinic acid (niacin) were compared with those of an organic source of Cr on performance, morbidity and blood metabolites were investigated of 135 crossbred steer calves, purchased at three sales in Ontario. Calves of 236-kg average weight were randomly assigned to control, 0.75 mg kg−1 (dry matter) organic Cr from Cr yeast, 0.75 mg kg−1 inorganic Cr from CrCl3∙6H2O, 100 mg kg−1 niacin, or CrCl3∙6H2O + niacin for the 28-d stress and 28-d growing periods. During the first 2 wk Cr supplementation was doubled. The basal diet was 75% alfalfa silage, 23% high-moisture corn and 2% mineral and vitamin supplement. Treatments had no beneficial effect on overall morbidity. Inorganic Cr and niacin alone had no beneficial effect (P > 0.10) on performance. Inorganic Cr and niacin used together, however, tended to increase weight gain by 39% (P = 0.09) and feed efficiency by 47% (P = 0.08) during the 28-d stress period, with no improvement during the later growing period. Inorganic Cr together with niacin increased serum iron concentration (P = 0.01) and serum total iron-binding capacity (P = 0.01) of healthy calves but had no effect on these metabolites in morbid calves. This study suggested that supplemental inorganic Cr is not as effective as an organic source for ruminants. Supplemental inorganic Cr with niacin tended to improve performance of stressed calves, suggesting that niacin may be a limiting factor for absorption and (or) use of inorganic Cr. Key words: Chromium, niacin, stressed calves, iron, iron-binding capacity, cortisol

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 objectives 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-α) 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-α) 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.

The acute phase response as indicated by serum haptoglobin and total haemolytic complement activity (CH50) was measured in 72 cross-bred steer calves purchased at sales in Ontario. During the 28 day (d) trial, 18 steers were randomly assigned to each of the following groups: 1) control; 2) vaccinated (Infectious Bovine Rhinotracheitis, Parainfluenza-3, Bovine Viral Diarrhea, Bovine Respiratory Synctial Virus vaccine plus Pasteurella haemolytica vaccine); 3) supplemental chelated Cr (0.14 mg/kg); and 4) Cr plus vaccines. Haptoglobin concentrations were low at arrival, increased (P < 0.05) on day 7, and returned to near initial levels (P > 0.05) by day 14. Supplemental Cr reduced (P < 0.05) haptoglobin on day 7 when morbidity was highest. Following antibiotic treatment for respiratory disease haptoglobin was lower (P < 0.05) than during morbidity; however, during morbidity, haptoglobin concentrations were not greater in sick calves (P > 0.05) than in healthy calves. Complement activity was lowest on day 7 (P < 0.05) and peaked on day 14 (P < 0.05). Complement activity tended to be lower on day 7 for vaccine, Cr, and Cr+ vaccine groups; however, the difference from controls was not significant (P > 0.10). Complement activity did not increase on day 14 (P > 0.05) with Cr supplementation as in other treatments. Morbid calves had lower (P < 0.05) CH50 activity than healthy calves on day 14. Following antibiotic treatment, the Cr-supplemented group had higher (P < 0.05) CH50 than during morbidity. In general, chromium supplementation reduced the acute phase response in newly arrived feeder calves.

A 56-d growth trial was conducted to evaluate performance and plasma amino acid (AA) responses of 63 Charolais-crossed steer calves fed alfalfa–grass silage diets. The basal diet was supplemented with either high-moisture corn (control), roasted, flaked, steeped (1 h) soybeans or a 60:40 (dry basis) mixture of corn gluten and blood meal (CG–BM). All diets were balanced for net energy, while the steeped soybeans and CG–BM diets were balanced for rumen-undegradable protein (RUP). Dry matter intake was similar across diets (2.39% of BW). Weight gains were higher (P < 0.01) for the steers fed with CG–BM (12.6%) and soybean (6.9%) supplemented rations than control steers. Digestibilities of neutral and acid detergent fibre were not adversely affected by roasted, steeped soybeans. Plasma glucose was lower (P < 0.05) and plasma urea was higher (P < 0.05) in the soybean- and CG–BM-supplemented steers than in control steers. Supplementation with steeped soybeans or CG–BM increased (P < 0.001) total plasma essential AA, branched-chain AA (BCAA) and BCAA/glycine ratio and lowered the total nonessential AA (NEAA) to essential AA (EAA) ratio. Plasma AA parameters were directly related to the rumen undegradability of the protein supplements. A lower plasma NEAA/EAA ratio indicated improved protein nutrition. These results showed that roasted, steeped soybeans delivered needed protein to the small intestine of rapidly growing steers fed alfalfa–grass silage. Key words: Roasting, steeped, soybeans, protein

Performance, morbidity, serum Cortisol, plasma ascorbate (AsA) and serum tri-iodothyronine (T3) were evaluated in crossbred steer calves purchased at sales in Ontario. Thirty-three steers were randomly assigned to each of control; vaccination with Infectious Bovine Rhinotracheitis, Parainfluenza-3, Bovine Viral Diarrhea, and Bovine Respiratory Synctial Virus vaccine and P. haemolytica vaccine; 0.14 ppm supplemental chelated Cr; and Cr plus vaccines, for the 49 d trial. Supplemental Cr plus vaccine increased (P < 0.05) daily gain and feed intake during the first 28 d. Furthermore, vaccination increased (P < 0.05) 28 d gain for mid-performing steers. Vaccines, Cr and Cr plus vaccines did not reduce morbidity (P > 0.05); however, the Cr-supplemented group had fewer relapses (P < 0.05). Rectal temperature was reduced in both vaccinated and Cr-supplemented calves on days 10–16 post-arrival. Serum cortisol was reduced (P < 0.05) in vaccinated calves and morbid Cr-supplemented calves on day 28 post-arrival. The ratio of free to total T3 on day 7 and day 14 post-arrival, and AsA on day 14 post-arrival was greater (P < 0.05) for calves receiving supplemental Cr plus vaccines. Results confirm previous reports of the beneficial effect of Cr on performance, and indicate some additive effects of Cr and vaccines with respect to daily gain and plasma ascorbate. Key words: Chromium, vaccines, ascorbic acid, tri-iodothyronine, stress, calves

The effects of supplemental chromium (Cr) in the diet, or by direct addition to the culture medium on proliferation of bovine peripheral blood lymphocytes (PBL) was evaluated with and without addition of the mitogen concanavalin A (con A). Twenty-four stressed steer calves were randomized (three animals per pen) to the following treatments: control diet (high quality corn silage) and control diet supplemented with 0.14 ppm chelated Cr. The PBL blastogenic activity was accessed using 0, 2 and 10 ug/ml con A on d 0, 7, 14, 21, 28, 35, and 49 following arrival of calves from sales barns. Blastogenic activity was measured by uptake of methyl-3H-thymidine. The PBL from calves fed dietary Cr showed increased (P<0.05) blastogenic activity following incubation with culture medium containing the higher concentration (10 ug/ml con A) of mitogen. An interaction between Cr and health status of calves occurred with or without mitogen (P<0.05). Morbid animals had lower PBL blastogenic responses but supplemental Cr increased (P<0.05) this response of morbid animals. However, supplemental Cr had no effect on response of healthy animals. When soluble chelated Cr was directly added to the culture medium at 0, .045, .45 and 4.5 ppm, Cr enhanced (P<0.05) blastogenic activity at both concentrations of mitogen, as well as without mitogen stimulation. In addition, using PBL from eight animals fed the control diet from d 0 to 120, chelated Cr and CrCl3 were directly added in the PBL culture medium at 0, 0.0045, 0.045, 0.45 and 4.5 ppm, and the same enhanced blastogenic activity was observed. However, chelated Cr showed greater (P<0.10) enhancement of PBL activity at 0.045 to 0.45 ppm and CrCl3 at 0.0045 ppm concentration (P<0.05). These results confirmed previous indications that Cr can effect certain aspects of cell mediated immunity, which may contribute to the morbidity reduction of calves fed supplemental Cr.

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.

Using crossbred calves obtained at feeder sales in Ontario, we evaluated two different sources of organically complexed chromium (Cr) for supplementing corn silage. A preliminary trial was conducted with 12 unstressed steers with or without 1 mg kg −1 chelated Cr during a 56-d growing period. Chelated Cr markedly decreased (P < 0.05) serum cortisol and glucose levels. In the main trial, 72 calves, weighing 233 kg, were randomly allotted to four treatments: control, high-Cr yeast, chelated Cr, and chelated Cr plus chelated Zn, Cu and Mn for the initial 7 d. Morbidity was determined by visual detection followed by rectal temperature checks. One third of morbidity occurred by day 12; two thirds, by day 16. High-Cr yeast tended to reduce morbidity; however, chelated Cr was more effective, resulting in 16.5% morbidity, or less (P < 0.05) than one third of the control. Daily gain was 41% higher (P < 0.05) with chelated Cr during the first 21 d after arrival, mainly due to the marked reduction in number of sick calves. During days 21–35, compensatory gain occurred with the morbid or antibiotic-treated calves. These data indicate that early (relative to peak morbidity) supplementation of stressed feeder calves with chelated Cr markedly reduces morbidity. Key words: Chromium, stress, calves, morbidity, cortisol, steers

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 level of supplemental Cr from high-Cr yeast on performance, blood chemistry profile, morbidity, and immune status were investigated using 84 Charolais-crossed steer calves in a completely randomized design. Calves of 236-kg average weight, after transportation from Saskatchewan to Ontario, were randomly assigned to four treatments; 0, .2, .5, and 1 ppm of supplemental Cr, incorporated into a corn-silage diet. Blood was collected via jugular venipuncture at d 0, 7, 14, 21, and 28 and analyzed for metabolites, minerals, immunoglobulins, hematocrit (Hct), and leucocyte counts. Hemagglutinating antibody titers to human red blood cells (HRBC) were quantified after immunizations on d 0 and 14. Contact sensitivity after sensitization and challenge with dinitrochlorobenzene was also measured. A 27% increase (P < .05) in ADG was observed at d 30 for calves that were fed .2 and 1 ppm of supplemental Cr. Dry matter intake also increased (P < .05) for the .2- and 1-ppm Cr treatments. A linear decrease (P < .05) in serum cortisol with increasing Cr level was observed at d 28. Chromium supplementation decreased (P < .05) morbidity, as well as rectal temperatures at d 2 and 5. Peak primary antibody titers to HRBC (P < .05) and immunoglobulin G1 concentrations (P = .06) at d 14 were higher for steers that received the Cr supplementation. However, Cr treatment had no effect on expression of contact sensitivity. Chromium supplementation increased (P < .05) Hct on d 14 and 21 and serum Ca and Mg on d 7.(ABSTRACT TRUNCATED AT 250 WORDS)

This study investigated the effects of supplemental chromium (Cr) (0 or 0.2 mg kg−1 from high-Cr yeast) on performance, carcass characteristics and tissue-mineral contents of growing–finishing steers fed corn silage supplemented with either urea–corn or soybean meal during the growing period and a high-grain diet during the finishing period. Ninety-six Charolais-crossed steers, divided into four treatment groups with 24 animals each, were fed for a 70-d growing period followed by a 68-d finishing period. After continuous supplemental Cr, steers were commercially slaughtered and their carcass characteristics were evaluated. Tissue samples, including loin-eye lean and rib fat, liver and kidney, were analyzed for Cr and other minerals (P, Ca, Mg, Fe, Zn and Cu). Supplemental Cr had no effects (P > 0.05) on average daily gain (ADG), dry-matter intake, (DMI), feed efficiency (ADG/DMI), and carcass characteristics, including dressing percentage, loin-eye area, backfat thickness, marbling score, kidney fat and liver weight. Proportion of lean, fat and bone in rib sections was not affected (P > 0.05) by Cr supplementation. Supplemental Cr also did not affect (P > 0.05) total-tissue Cr and other mineral concentrations. However, supplemental Cr increased (P < 0.05) the Cu level of livers in steers fed urea–corn supplements during the growing period. This study showed that continuous supplementation of Cr (0.2 mg kg−1) to unstressed growing-finishing steers had no effect on carcass composition and several minerals in various tissues. Key words: Chromium, steer, carcass, tissue