In poultry production, performance parameters are usually related to regular factors such as health and nutrition. Exposure to environmental noise should not be underestimated either, however. Birds don't like noisy conditions and tend to perform less.
By Dr Salah H. Esmail, Cairo, Egypt
The noise intensity associated with any power source in a farm is best measured in decibels (dB) using a sonometer. Given in Table 1 are the permissible noise levels and the allowable duration of exposure. Should the birds be exposed to higher levels of noise, or for a period of time beyond these recommendations, then a number of production problems can be expected.
A study was conducted in a poultry farm in Sanaa, North Yemen to examine the effects of noise stress on feed intake, digestion and performance of broiler chicks. A power generator operating at 160 KW capacity was used as a major noise source. Intensity of noise, expressed in weighted dB, was measured by a sonometer in two chicken houses located at distances of 30 and 200 meters from the generator. The generator was operating continually and values of 83 dB and 64 dB were obtained for the houses at 30 and 200 meters from the generator, respectively.
Production responses of chicks exposed to different levels of noise are shown in Table 2. The chicks exposed to 83 dB at 30 meters from the generator had a lower feed intake compared to those exposed to 64 dB at 200 meters. As a result, weight gain of the former group was lower and the efficiency of feed conversion was also reduced.
The decreased intake of feed by the high-noise group could be explained by a variety of functional changes in the internal body system. Hormonal changes, such as decreased adrenal activities, were found to be a result of exposure to noise stress. The decreased adrenal activity may affect feed intake through a reduced intestinal relaxation.
Thus, a small amount of feed may pass out of the crop, due to prolonged periods of contraction of the small intestines. It was also reported that during noise stress there is a decreased gastric secretion caused by a transient ischemic change in the gastric mucosa and by an increased gastric motility. Consequently, physical retardation of feed intake may arise due to the gastric distension and the delayed entry of gastric chyme into the duodenum.
Breakdown of glycogen
Digestibility results are also shown in Table 2. Digestibility values of dry matter (DM) and protein were similar among the two treatments, but fat digestibility was reduced in the high-noise group. This may have been an additional factor in reducing weight gain of the chickens. It has also been reported that production of glucocorticoids is elevated by excessive noise.
This should give rise to a rapid breakdown of glycogen in the muscle cells, leading to a decline in pH and a delay in the temperature drop after slaughter. Both of these factors are responsible for pale, soft, oxidative (PSE) meat. Furthermore, reproductive hormones, such as estrogen and progesterone, have been found to respond adversely to noise stress. This effect has not yet been observed for poultry, but is commonly reported in horse and cattle.
Keep it silent
To alleviate noise effects in poultry farms, the distances between the chicken houses and the source of the noise should be given a prime consideration. As indicated earlier, the farther the distance, the less noise stress and the better performance. However, in small farms where the land area is a limiting factor, alleviating the noise stress by means of increasing the said distance may not be a practical approach. Installation of resonators or exterior application of noise baffles may be considered in such a case. Also, consultation with a qualified acoustical engineer can lead to specific solutions for most noise problems.