C.M. Wathes

The preferences of laying hens for different concentrations of atmospheric ammonia

Ammonia gas is one of the most abundant aerial pollutants of modern poultry buildings. The current chronic exposure limit for ammonia of 25 ppm is set for human safety rather than animal welfare. This study assessed the behavioural preferences of laying hens (Gallus gallus domesticus) for different concentrations of ammonia found in commercial poultry houses. Six groups, each of six laying hens, were given the choice of three concentrations of ammonia ( approximately 0, 25 and 45 ppm) in a preference chamber over a period of 6 days and their location and behaviour recorded every 15 min. Hens foraged (p=0.018), preened (p=0.009) and rested (p=0.029) significantly more in fresh air than in the ammonia-polluted environments. There was a significant difference between the responses in 0 and 25 ppm (p<0.05) but not between 25 and 45 ppm (p>0.05). This suggests that ammonia may be aversive to hens with a threshold for this aversion between 0 and 25 ppm. Future studies should explore graded concentrations of ammonia between 0 and 25 ppm in order to suggest a new chronic exposure limit on the basis of animal welfare.

Aerial emissions from poultry production

Aerial emissions from poultry production may affect bird performance, cause respiratory ill health in stockmen and are a source of environmental pollutants. Recent measurements of the concentrations in, and emissions from, poultry houses are presented. Control of aerial emissions must be integrated with other environmental parameters that determine the profitability and sustainability of poultry production.

The preference of pigs for fresh air over ammoniated air

Abstract Six weanling pigs were given the choice, in a two-sided preference chamber, of freely moving between fresh air and ammoniated air (approximately 100 p.p.m. ammonia). The air supplies could be switched between the two sides; the two sides were otherwise made as similar as possible. The pigs were kept in the chamber, one at a time, for 14 days. The first 4 days were a familiarisation period when both sides where supplied with fresh air. During a subsequent 10-day experimental period, the treatment (fresh air or ammoniated air supply) was changed from side to side every 24 h. A computer program that monitored the activation of pressure pads on either side of a flap door between the two sides recorded the pigs movements. During the familiarisation period each pig established one side on which to spend most of its time; the analysis therefore tested whether the treatment with ammoniated air changed the proportion of the day that each animal spent on that side. The results show a significant (P ≤ 0.001) decrease in the amount of time spent on the preferred side when that side was supplied with ammoniated air, with four of the six pigs demonstrating a marked response. This indicates that pigs may find a contaminant of the air of piggeries, ammonia, aversive. The potential for detailed study of responses to different substances and concentrations may help to provide new specifications for air quality in intensive livestock housing.

The balance of airborne bacteria in calf houses

The bacterial content of the air and physical environment of two crated veal calf units were monitored over the growing period of 16 weeks. The rate of release of bacteria colony forming particles (BCFP) from the calves was rapid, typically 2×10 6 BCFP/h per unit calf area, and showed a positive correlation with absolute humidity. The concentration of airborne BCFP, arising mainly from these calves, was about 30 BCFP/l, but was not a simple function of climate. In addition to clearance by ventilation at rates ranging from 2 to 10 air changes/h, the airborne bacteria were removed by sedimentation and other physical processes, and killed by normal biological mechanisms. The combined rate for the latter two pathways of clearance was equivalent to 4–49 air changes/h, which is of a magnitude comparable with ventilation rates in naturally-ventilated livestock buildings. At present the critical concentrations of non-pathogenic bacteria in animal houses are unknown and so a minimum ventilation rate based on this criterion cannot be calculated. However, recognition of the different routes of clearance of airborne bacteria, including ventilation, is fundamental to the design of animal houses.

The RCVS codes of conduct: what's in a word?

In 2012, the RCVS introduced a new Code of Professional Conduct for Veterinary Surgeons, replacing the Guide to Professional Conduct which had existed until then. Is a common Code relevant for the veterinarians many roles? Theres more to think about here than just the change of name, write Steven McCulloch, Michael Reiss, Peter Jinman and Christopher Wathes