Penny Young, ASAS/ASAP Intern
New research from the University of Melbourne recently listed for review in Translational Animal Science finds that chromium supplementation may help to increase insulin sensitivity, normalize NEFA metabolism and reduce heat stress in pigs. Managing heat stress in animals is important from both economic and welfare perspectives, and the findings from this study make a case for the inclusion of dietary chromium in diets during periods where heat stress is anticipated.
The team, headed by Fan Liu and sponsored in part by Australian Department of Agriculture and Water Resources via the Carbon Farming Futures Program, investigated several markers of heat stress in pigs and also looked into the effects of chromium supplementation on these indicators. Insulin sensitivity was a particular focus because research has suggested that increased insulin sensitivity may help to alleviate heat stress.
It appears insulin helps to mitigate heat-stress by enhancing skin microcirculation. When increased insulin sensitivity is induced by administration of chromium this effect is reinforced because chromium can facilitate vasodilation and may also help to improve radiant heat dissipation. Targeting insulin in the management of heat stress is also important because attenuated lipid mobilization in heat-stressed pigs leads to increased fat deposition, and based on studies in ruminants this may be due to increased insulin resistance or hyperinsulinemia (although this was not found to occur in this study). Other studies have found that it is likely chromium helps to normalize the attenuated lipid metabolism in heat-stressed pigs, yet the effects on heat stress as a syndrome are variable, hence this study investigates physiology, feed intake, and insulin related metabolism in growing pigs during heat-stress.
Based on rectal temperature, respiration rate and blood results as markers, it was found that chromium can alleviate some physiological symptoms of heat stress in growing pigs. It helps to mitigate the increases in respiration rate and rectal temperature seen, most likely by improving heat dissipation through the skin and thus resulting in a reduced reliance on cooling through the respiratory route. The chromium supplementation was also found to improve average daily gain in the pigs kept at normal temperature (20oC), however this effect was not seen in the animals subjected to heat stress.
While the chromium diet seemed not to have a major effect on feed intake in the heat-stressed pigs in this study, this was perhaps due to the fairly dramatic intake reduction seen in those pigs under these conditions (40oC). It also appears that the impact of chromium supplementation might vary depending on the degree of heat stress, with another study finding that at a reduced heat stress condition, with ambient temperature at around 30oC, chromium supplementation did result in around an eight percent improvement in feed intake. The study found that chromium supplementation most likely has some direct role in facilitating lipolysis and identifies this as worthy of further research.
Read more about the findings here.
Liu, J. J. Cottrell, U. Wijesiriwardana, F. W. Kelly, S. S. Chauhan, R. V. Pustovit, P. A. Gonzales-Rivas, K. DiGiacomo, B. J. Leury, P. Celi, F. R. Dunshea