IF YOU CAN SMELL IT, IT'S ALREADY TOO LATE !
Air quality remains an important parameter for swine and poultry farming especially when animal density is increasing with close house system. Among different air parameters, ammonia stands the most important to control. Animals produce a large amount of ammonia and the effect on their health and performances are rapidly significant and well described in literature. What the research doesn’t know exactly is effect of ammonia before emission in the litter.
Underestimated effects of ammonia One study from Vilodre-Tuleda et al. (2015) shows that ammonia has a direct negative effects inside the digestive tract. Basically, it is shown in vivo on piglet that high concentration protein diet (26% CP) compare low concentration diet (18% CP) decreases absorption of butyrate by decreasing activity of an important transporter, the monocarboxylates receptor 1 (MCT1). The decrease of the activity of MCT1 can be reproduce ex vivo and in vivo by adding NH3 in the medium. It suggests that NH3 and maybe other protein-derived metabolites present in lumen digestive tract can trigger inflammation and reduce butyrate absorption. Butyrate is well-knowed as an essential molecule for digestive health and performances. Ammonia may be toxic for intestinal enterocytes, can impair barrier function and allow translocation of pathogenic bacteria. Furthermore, NH3 has a role in carcass quality in broiler. A study from Xing et al. (2014) has shown that from 25ppm exposure for 20 days (21 to 42 days), birds have a lower dressing, eviscerated yield, and breast muscle percentage. Relative weight of kidney and liver increase whereas spleen, thymus and bursa of Fabricius decrease. It suggest impact on immune system development. To finish, fatty acid profil (unsaturated fatty acid to saturated fatty acid ratio) decreases with ammonia exposure which testifies a lower meat nutritional value. It can be explained by a higher concentration of free radicals in cell because of the immune response triggered by ammonia.
Well known effects of ammonia
Ammonia is a colourless, water-soluble gas and a strong irritant with a pungent odour. Ammonia is a by-product of microbiological decomposition of organic nitrogen compound from feces, inside and outside of the digestive tract. In case of birds, uric acid is the main nitrogenous compound in feces and must be degraded into urea before becoming ammonia. The process of decomposing uric acid and urea into NH3 involves several enzyme produced by enteric flora, including uricase and urease. This process requires water and oxygen to produce NH3 and carbon dioxide. It is influenced by diet composition, ventilation, animal density, moisture content, pH and temperature of the litter. Ammonia concentration in farm houses should be between 5 and 25ppm. Sometimes it can reach 100ppm in finishing period with. For human nose, detection threshold can vary but ammonia is usually detect from 10 to 30 ppm. Environmental parameters like ventilation and relative humidity are closely related to ammonia concentration and must monitored if you cannot measure directly ammonia concentration in house. Effect on performances are well documented and summarized for swine and poultry in figure 1. FCR and intake are affected because animal show reduce voluntary intake of feed and water.
Figure1: Effect of ammonia on performances and health
Health status and respiratory welfare reduction of animal can explain a part of performances diminution. The first witness of ammonia intoxication is eye membrane infection. It can be followed by conjunctivitis as we can see on figure 2. Those diseases are painful for animal.
Figure 2: Conjunctivitis on broiler
The third effect of ammonia emission is on the farmer welfare and health. Ammonia irritates respiratory tract, make eyes crying and its odour is unpleasant. It’s a concern for neighbourhood of the farm as well. Dietary manipulations to reduce ammonia emission
Crude protein reduction: A lot of feed millers in Asia traditionally produce feed with high level of crude protein for regulatory reason and because the market ask for. (see our Nutricle: High or low protein?). Reduce this level of crude protein is the first step to reduce ammonia production
Utilisation of highly digestible protein (like hydrolysate) is recommended to reduce the part of non-digest protein which will be degraded into ammonia or favour gut malfunction like post weaning diarrhoea or necrotic enteritis.
Synthetic amino acid is recommended with some limitations (see our Nutricle: High or low protein?)
Enzyme like protease can be used to reduce the non-digest protein part
Feeding program following: it’s not, strictly speaking, a dietary manipulation but maybe one of the most efficient. For example in swine production, grower feed is used for a too long time (sometimes until finishing) and hog receive a large amount of protein they cannot valorised.
Saponins: We can found saponins in some plants like fenugreek or yucca and they can reduce ammonia emission by inhibiting urease activity and directly bind ammonia. Saponin can reduced the odour of manure as well and increase farmer and his neighbour welfare. Inhibiting urease activity is a strategy also used by the fertilizer industry.
The following tips remain the most cost effective according to an English studies (purple bubbles on figure 3).
Figure 3: Bubble diagram showing strength of evidence, cost effectiveness and acceptability for a range of interventions to reduce ammonia emissions
Ammonia is an issue in livestock farming for many reasons: reduction performances, health and welfare. Nevertheless, with dietary adaptations and a focused management on air quality, it’s possible to reduce the impact of ammonia on our industry.