Effects of dietary inclusion of chromium propionate and calcium propionateon glucose disposal and gastrointestinal development in dairy calves

In experiment 1, 21 male Holstein calves (43.9 kg) were fed only milk repla cer at 1.4% of their body weight as dry matter for 6 wk. Dietary treatments included a commercial milk replacer (22% protein, 15% fat) containing (dry basis) either 6.4% Ca propionate or 6.4% dextrose (control) and either 0 o r 0.5 mg/kg of supplemental Cr as Cr propionate. Neither Cr nor Ca propiona te affected body weight gain; however, Ca propionate tended to increase the growth of the entire foregut measured after slaughter at 6 wk of age. A Mi nimal Model glucose tolerance test indicated that insulin sensitivity was n ot affected by treatment. However, calves fed Cr had higher glucose disappe arance indexes than controls when propionate was not fed (0.013 vs. 0.019 u nits) but similar clearance when propionate was included (0.018 vs. 0.018 u nits, Cr x P interaction). The area under the glucose response curves after propionate-loading tests was much greater for calves fed the Cr versus con trol replacer when propionate was not present; however, when propionate was included, the response was less dramatic. In experiment 2, 25 Holstein calves were used to study performance and meta bolic responses when milk replacer, and then postweaning starter, were supp lemented with 0.5 mg/kg of Cr as Cr propionate. The metabolic responses of these calves were not affected by treatment. Overall, combined data suggest ed that supplemental Cr may improve glucose effectiveness; however, these r esponses seemed to be attenuated by supplemental propionate.