Zinc supplementation to ameliorate the adverse effects of cadmium on rumen fermentation in cattle

The effect of graded levels of cadmium (Cd) on in vitro rumen fermentation and amelioration of its adverse effects through Zn supplementation was studied in cattle. In the first experiment, different levels of Cd (0 to 20 ppm) were supplemented to substrate (concentrate and roughage in 40:60) and incubated in vitro to find out the minimum level of Cd that may affect the rumen fermentation. It was observed that 10 ppm Cd supplementation, decreased DM as well as NDF digestibility and total volatile fatty acid concentration significantly(P<0.05), while NH₃ -N concentration increased with increase in Cd concentration in the inoculum. Second experiment was conducted to observe the effect of different levels of Zn (0, 50, 100, 150, 200, 250 and 300 ppm) on in vitro rumen fermentation to substrate containing 10 ppm Cd. Results revealed that zinc supplementation up to 100 ppm had no effect on IVDMD, IVNDFD or tVFA concentration, whereas, fiber digestibility was depressed (P<0.05) at higher levels of Zn supplementation. Ammonia nitrogen concentration was reduced significantly at 200 ppm and thereafter. Based on the results, 100 ppm Zn level was selected for in vivo studies.

Karan Fries male crossbred calves (14; 4–5 m old) divided into three groups with 4, 5 and 5 calves in each group were offered conventional control diet (C) or C supplemented either with 10 ppm Cd (T,) or 10 ppm Cd and 100 ppm Zn (T₂) for 30 days. There was no change in tVFA and TCA-N concentration. However, NH₃-N concentration was high (P<0.05) in T₂. There was increase (P<0.05) in the alanine transaminase (ALT), aspartate transaminase (AST) and urease in T₂ which tended to decrease in group T₃. It was evident that zinc supplementation at 100 ppm level reduced NH₃-N concentration observed due to feeding of 10 ppm Cd in crossbred male calves.