Increasing air movement at floor level during a broiler flock growout may provide drier litter and improved paw quality, according to recently completed research at the University of Georgia that was funded by the U.S. Poultry & Egg Assn. (USPOULTRY) and the USPOULTRY Foundation.
In the project, Dr. Mike Czarick and colleagues at the University of Georgia studied the use of circulation fans to help reduce litter moisture in broiler houses and found that, in addition to improved litter and paw quality, thermal stratification in a broiler house was reduced, which allowed birds to distribute themselves comfortably throughout the house.
Using circulation fans to help dry litter appears to cost less than using only conventional ventilation methods.
In a summary report, Czarick said today's broiler producers are relying less on antibiotics and putting more attention on animal welfare than ever before, which means growers are being challenged to improve litter management. High litter moisture (greater than 35%) has been correlated with increased risk factors related to bird health and welfare, Czarick noted.
He said litter moisture can be reduced through proper drinker management and ventilation to maintain a low relative humidity (Rh) in the house (less than 50%).
While proper drinker management should not place a financial burden on the grower, decreasing Rh by just 20% could increase heating costs by 45% due to the higher ventilation rates required, depending on specific conditions in a broiler house, Czarick said.
A possible alternative to primarily using ventilation to control litter moisture could be maintaining a moderate Rh level (50-60%) and increasing air movement over the litter through the use of circulation fans, Czarick said. Traditionally, circulation fans have been used mainly to minimize temperature stratification, improve temperature uniformity and conserve energy, he noted.
According to Czarick, circulation fan systems designed to meet these objectives do not typically produce a significant level of air movement at floor level, which limits litter drying.
The objective of Czarick's study was to evaluate the combined effects of maintaining a moderate house Rh level (50-60%) and moderate level of air movement (150 ft. per minute) across the floor on litter moisture, paw health and coccidia sporulation.
A total of five flocks were studied on two commercial broiler farms (two houses per farm) One house on each farm did not use circulation fans (control), and an adjacent house (treatment) was equipped with eight 24-in., one-third-horsepower circulation fans that operated continuously throughout the flock. Both houses on each farm were managed similarly and were ventilated to maintain a moderate Rh of 50-60%.
Czarick reported that the combination of maintaining a house Rh between 50% and 60% and an average velocity at floor level of 150 ft. per minute resulted in a more consistent environment throughout the house. During cold weather, when temperature uniformity tends to be more problematic, the treatment house temperatures differed by less than 5°F more than 99% of the time, while control house temperatures varied less than 5°F only 50% of the time, he added.
Thermal images showed that areas beneath tube heaters in control houses often exceeded 120°F during colder weather, while floor temperatures in the treatment houses ranged from 85°F to 100°F, Czarick reported. These differences in floor temperatures led to uneven bird distribution in the control house, he noted, adding that birds often gathered near sidewalls to avoid areas under the heaters in control houses, while birds in the treatment houses were more evenly distributed.
These differences in bird distribution influenced litter moisture profiles, Czarick said, noting that by three weeks, litter moisture was often 20-25% in treatment houses versus 25-35% in control houses. Furthermore, sidewalls in treatment houses tended to be at moisture levels of less than 25% versus greater than 30% in control houses during the cooler times of the year, he added.
With drier litter, footpad lesions were typically lower in treatment houses. By the end of each flock, usually fewer than 30% of the birds scored showed signs of severe lesions in the treatment houses, whereas more than 50% of birds displayed signs of severe lesions in the control houses, Czarick said.
If a paw value of $1.00/lb. is assumed, the treatment effect could have the potential to save up to $3,000 per year for a 25,000-bird house growing a 4.5 lb. bird, Czarick said.
According to the researchers, participating producers observed that ammonia levels were consistently lower in the treatment house. Ammonia measurements taken over the first four weeks of one flock found an approximately 50% reduction in ammonia concentrations in the treatment house versus the control (15-25 versus 30-40 parts per million).