The French and Dutch Experiences in Controlling Odour on Farms

The influence of intensive agriculture on both the environment at large and within livestock buildings is receiving the highest priority in research programmes. In many cases emissions are a limiting factor for the location and operation of animal production facilities throughout the world. Odours from livestock production are perplexing mixtures of chemical compounds and have become a severe social problem in many countries. Some of the compounds will have health damaging effects as well.

Ammonia was choosen as an indicator of air quality problems due to its influence on the well-being of livestock and stockmen together with its influences on atmospheric pollution. Numerous workers have noted the important adverse effects of ammonia on human health. Recent reports have been made by Nowak (1995) for Germany and Tielen et al. (1995) for the Netherlands and in the United Kingdom by Whyte et al. (1995).

In addition there are many reports of reduced animal performance and reduced health status in poor environmental conditions (e.g. Attar and Brake, 1988; Emsinger et al., 1990; Roberston et al., 1990; Drummond et al., 1980). Recent reports from the Royal Veterinary and Agricultural University of Denmark have shown that even extremely short exposure duration can be harmful. Exposure of pigs to 50 ppm ammonia for 20 minutes a day, on four occasions only, seriously reduced animal performance between 37 and 90 kg liveweight (Figure 1). In addition, the same authors found in further experiments that ammonia seriously reduced respiratory health.

Another important effect of aerial ammonia is the delay of puberty, even at the level of 20 ppm, as shown by Malayer et al. (1988).

The seriousness of the problems caused by aerial ammonia is underlined by a law (Health and Safety Executive, 1989) in the United Kingdom. The levels of substances to which workers can be exposed are regulated in order to protect respiratory health of the worker. Ammonia is closely controlled by this legislation with levels of 25 to 35 ppm allowing the presence of the worker for only 10 minutes per day. When the level of ammonia exceeds 35 ppm the worker is not allowed in that building without a respirator. Even if these regulations are kept by the pig worker, the animals are subjected to the gases for 24 hours daily.

In spite of all reports and legislation concerning the negative impact on health and performance, ammonia in pig buildings in the Netherlands is not regarded as a problem (e.g. van der Voorst, 1991; Verdoes, 1990; Kemme et al., 1993) because levels will be below 10 ppm when practising good hygiene and optimum ventilation, which is contrary to experiences in other countries.






Consequently two studies under Central European circumstances were conducted to establish the levels of ammonia in pig buildings and to test the effect of Yucca schidigera extract (De-Odorase, Alltech Inc.) on ammonia concentrations and animal performance. De-Odorase was choosen as a means to reduce atmospheric ammonia since a number of people (e.g. Mader and Brumm, 1987; Cole and Tuck, 1995; Ender et al., 1993; Lyons, 1997) have reported its ability to reduce ammonia and odour and to improve animal performance.


The ammonia survey

METHODS

The first study was conducted in the Netherlands during 1994–1995 (Schuerink, 1995) followed by a study in France during 1996–1997 (Morel, 1997). To establish ammonia levels in the Netherlands, the survey was conducted on a sample of 27 farms representing a wide range of farm types in terms of feed characteristics, feeding system, floor type, stocking density and ventilation systems. To investigate the effects of Yucca extract on aerial ammonia and pig performance, a total of 900 and 5,780 pigs, respectively, were involved on five farms in the Netherlands and six farms in France. Pigs on each farm were equally divided over control and trial groups. Trial groups were fed the same feed as the control groups except for the addition of 120 g De-Odorase per tonne of feed for the trial groups.

In the Netherlands measurements for both control and trial groups were done at the same time, whereas in France 80% of all observations for the control groups were done in summer whereas 44% of the measurements for the trial groups were done in winter. Atmospheric ammonia levels were measured at least three times per fattening period using Dräger diffusion tubes for an 8 hour period situated 1 metre above the floor in the pig building. The Dräger tubes were validated in a study comparing them with a wet chemical method at IMAG Wageningen (Vijn, 1995). No significant difference was shown between the two techniques in quantifying ammonia concentrations.


RESULTS

Overall situation

The levels of ammonia measured in Dutch pig buildings are given in Figure 2. The results are interesting in that there was a wide range and the values were considerably higher than would be expected from previous reports. Very few values fell in the range that is suggested might be achieved with good management and ventilation. In the period August–September, 75% of all atmospheric ammonia concentrations were above 10 ppm; whereas in winter time more than 90% of the measurements exceeded 10 ppm. The averages were 20 and 30 ppm for summer and winter, respectively, and differed significantly (P<0.01).






The ammonia concentrations observed on French farms are given in Figure 3. These results confirm the Dutch findings regarding the differences in distribution between summer and winter. In the summer 63% of the readings exceeded 20 ppm, whereas in winter almost 90% of all measurements were found to be above 20 ppm. The averages differed significantly (P<0.0001) and were 27 and 47 ppm, respectively, for summer and winter.










Effect of De-Odorase on atmospheric ammonia

The use of De-Odorase in the diet (120 g/tonne) was effective in reducing ammonia under practical farm conditions in both the Netherlands and France. In the Netherlands ammonia had been measured before the trial started and on four occasions during the trial phase, at days 10, 40, 70 and 100 after the start of the fattening period. In France the four measurements were taken at 10, 40 and 60 days after entry into the fattening unit and 2 weeks before the removal of the pigs. The average reductions in atmospheric ammonia in response to De-Odorase were 42.5 and 28.5% for the Netherlands and France studies, respectively. The findings are shown in Figures 4 (Dutch, P<0.01) and 5 (French, P<0.001). Furthermore, it was estimated that the reductions in ammonia obtained by De-Odorase equal an increase in practised ventilation rate of 200%, which will induce respiratory problems.


Effect of De-Odorase on animal performance

The incorporation of De-Odorase in the pig diet improved certain aspects of animal performance in both countries (Table 1). From both studies it can be concluded that De-Odorase improved efficiency and reduced mortality (P<0.05). Decreased mortality in this regard reflected improved health status of the animals due to reduced ammonia, which was underlined by the reduced costs of medication (P<0.02) in the French study.






Conclusions

As an example for Central European circumstances, these surveys in the Netherlands and France show that ammonia levels can be extremely high.

These levels and the frequency of their occurrence are much higher than was believed and there is a need for reduction to levels below those which can have consequences on both pigs and stockmen.Ventilation needs to be adequate for the well being of the animal, but is constrained by the need to maintain house temperature. It has been shown that De-Odorase reduces ammonia levels significantly and improves animal performance in terms of feed conversion ratio, mortality and reduced costs of medication while maintaining the normal ventilation rate.






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