We investigated the effect of Cr supplementation on growth performance, feeding behavior, health status, and blood metabolites of summer-exposed dairy calves during the pre- and postweaning periods. A total of 24 newborn Holstein female calves (1 d of age; 42.1 ± 0.89 kg of body weight) were assigned randomly to a control group (no Cr supplement; Cr-) or a Cr group (Cr+) receiving 0.05 mg of Cr/kg of body weight. During the study period, the average maximum temperature-humidity index was 81.3 units, indicating a high environmental heat load. Chromium was provided in colostrum and milk during the preweaning period, and in the starter feed during the postweaning period. Calves had free access to fresh water and starter feed throughout the experiment and were weaned on d 63. Starter feed intake and total dry matter intake were greater in Cr+ calves. Despite decreased meal frequency in Cr+ calves, during the preweaning period the starter feed intake increased due to increases in meal duration and meal size and a tendency for greater meal interval. Increased postweaning starter intake in Cr+ calves was attributed to a tendency for an increase in meal duration. Chromium-supplemented calves had greater overall weight gain, but their feed efficiency and rectal temperature were not affected by Cr treatment. Chromium supplementation tended to increase the heart girth during the preweaning and overall periods and increased the hip width during the postweaning and overall periods. Respiration rates were lower in Cr+ calves than Cr- calves during the preweaning and overall periods. During the preweaning period, the time spent in eating and ruminating per 12-h period was not affected by Cr treatment. During the postweaning period, the rumination time (min per 12-h period) was unaffected but total eating time (min per 12-h period) increased in Cr+ calves. Times spent resting, drinking, standing, lying, and in nonnutritive oral behaviors were not affected by treatments during the pre- and postweaning periods. Chromium supplementation had no effects on serum concentrations of cortisol, triiodothyronine, and thyroxine measured at weaning or the end of the trial. The Cr+ calves tended to have higher serum concentrations of glucose and a higher ratio of insulin to glucose measured at the end of the trial. In conclusion, Cr supplementation of both liquid and solid feeds improved growth performance in summer-exposed calves as a result of reduced respiration rate and increased feed intake; however, no beneficial effects were found on feed efficiency and insulin metabolism.

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.

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The objectives of this study were to investigate the effects of chromium (Cr) supplementation on feed intake and meal pattern, weight gain and skeletal growth, and health and metabolic criteria of environmentally heat-loaded dairy calves during the pre-weaning period. Forty-eight newborn female calves were allotted randomly to a control group (no Cr supplement; Cr-) or a Cr group (Cr+) receiving 0.05 mg Cr (as Cr-methionine)/kg BW. Cr was provided in the liquid feed (colostrum and milk) during the pre-weaning period. The average maximum temperature-humidity index was 83.7 U, indicating severe environmental heat load. Despite reduced meal frequency and increased in inter-meal interval, Cr supplementation tended to increase starter feed intake and total dry matter intake as a result of increased meal size and duration. Respiration rate was lower in Cr+ calves. Calf growth, rectal temperature, faecal score and incidence of diarrhoea or pneumonia were not affected by Cr supplementation, but number of days with diarrhoea and treatment duration decreased during the pre-weaning period. Cr supplementation tended to increase resting time and decreased time devoted to non-nutritive oral behaviours. At weaning, serum concentration of glucose was lower but total protein and globulin concentrations were higher in Cr+ calves. In Cr+ calves, the activity of glutathione peroxidase was higher and lower on d 49 and 63 of the study, respectively, compared to the control calves. Activity of catalase was increased on d 21 and tended to decrease on d 35 in Cr+ calves. In general, Cr supplementation to environmentally heat-loaded dairy calves decreased non-nutritive oral behaviours, improved feed intake and decreased days with diarrhoea and treatment duration, but had minimal effects on weight gain, metabolism and indicators of oxidative stress or insulin function.

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