less) can reduce nitrogen excretion, with ammonia emis- sions reduced by up to 24%. Further decreases in diet pro- tein levels, however, will require that all essential amino ac- ids are included, preferably in a crystalline form, while ensuring a careful balance of amino acids.
• Fibre nutrition: Fibre provides energy to bacteria in the lower gastrointestinal tract where the bacteria use nitrogen for bacterial protein synthesis that would otherwise have been excreted as uric acid.
• Feed additives: There are some additives that can be add- ed to the diet to sequester or trap ammonia. Among these is zeolite, a type of mineral with a porous or lattice-like struc- ture. When included in the diet, it binds ammonia in the faeces and prevents it from being emitted to the air.
• Minimising feed and water waste: Poultry will waste a significant amount of feed if feeders are overfilled, mounted too low, or poorly designed. In which event, faecal nitrogen may increase by 1.5% for every 1% increase in feed waste, and ammonia emission rates will therefore also increase. Feeders should be designed such that it is difficult for the birds to push the feed out of the feeders. The feeder height should be adjusted so that the top of the feed pan is level with the birds’ neck, with the feed fill level set to only 25% of the feeder pan. Too much water in the house also results in excess ammonia emission and poor air quality. This
problem can be alleviated by adopting the nipple drinker system which gives better control over water intake and wastage.
Insecticide pollution A study was conducted in Egypt to determine the effect of pes- ticide pollution on the vaccination efficacy of free-range chick- ens vaccinated against Newcastle disease using Hitchner-B1, Lasota, and inactivated vaccines. Newcastle antibody titers were found to be inversely proportional to the quality and number of pesticide pollutants in the sera, with the disease widely prevalent even on vaccinated farms leading to higher morbidity and mortality (Table 1), probably due to the immuno- toxicity and immunosuppressive effects of pesticides.
There are many reasons for vac- cination failure which can be prevented by carefully consid- ering every aspect.
Table 1 – Performance of free-range chickens reared in pesticide-contaminated areas and pesticide-free areas.
Item Pesticide Geometric mean antibody titer Morbidity (%) Mortality (%)
5.0 60 50
Source: Azzam, A.H. and E.E.K. Ahmed (2006). ▶ POULTRY WORLD | No. 1, 2020 9
No pesticide 7.0 20 10
PHOTO: JAN WILLEM SCHOUTEN
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