Acidification of calf bedding reduces fly development and bacterial abundance

Environmental stressors, such as high fly density, can affect calf well-being. Sodium bisulfate (SBS) is an acidifier that reduces the pH of flooring and bedding, creating a medium that neither bacteria nor immature flies (also known as larvae or maggots) can thrive in. Two experiments were conducted to investigate the application of SBS to a mixture of rice hull calf bedding and calf slurry (BED) to reduce house fly (Musca domestica L.) larval density and the abundance of bacteria. In experiment 1, dish pans containing 1 L of BED and 3,000 house fly eggs were treated with SBS at concentrations of 0, 8.9, 17.7, and 26.5 g of SBS/0.05 m2 of BED (CON, LOW, MED, and HIGH, respectively), with each SBS concentration applied to 4 individual pans (16 pans total). Reapplication of the same SBS concentrations in each pan occurred 3 times/wk throughout the 23-d trial. Larval house fly survival was significantly reduced in all pans with SBS relative to CON pans, with lowest survival rates in the MED and HIGH pans (99% and 100% reduction, respectively). The mean pH for each treatment was inversely related to the SBS concentration. In experiment 2, pans containing 1 L of BED and 3,000 house fly eggs were treated with either 0 g of SBS (CON), 8.9 g of SBS/0.05 m2 of BED with reapplication of the acidifier 3 times/wk (SB3×), or 8.9 g of SBS/0.05 m2 of BED applied only once at 48 h before the end of the 8 d-trial (SB48). Larval house fly survival and bacterial concentrations were reduced (90% larval reduction and 68% bacterial reduction) in the SB3× treatment relative to the CON. Mean pH was also reduced in SB3× pans relative to CON or SB48 pans. Overall, acidification of calf BED using the acidifier SBS resulted in a reduction of bacteria and house fly larval survival. This form of fly control might be expected to reduce adult fly production and, therefore, fly-related stress in calves.