Mirza, Muhammad Waseem
Improvement in litter quality and leg health by nutritional modification in growing turkeys.
PhD thesis, University of Glasgow.
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Pododermatitis (FPD) is a contact dermatitis commonly observed in poultry, primarily affecting the surface of the footpad and the hock joint, and causes poor welfare and economic losses when severe. Most reported field outbreaks of FPD have been associated with poor litter conditions. There are three important aspects of litter condition associated with incidences of FPD and hock burns (HB) i.e. increased litter moisture, greasy or capped litter as well as high ammonia (NH3) content. Therefore maintaining litter quality and more specifically the moisture content is essential if conditions such FPD and HB are to be controlled. Poor litter condition is caused by an interaction between management, nutrition and intestinal health. In terms of nutrition, dietary density i.e. energy and protein concentrations are important factors in terms of determining litter quality and incidences of FPD, because of the effect that they exert on water intake.
Four experiments were used to investigate the effects of nutritional modifications on water intake (WI) and excretion by turkeys. In the first experiment explored the effect of different dietary nutrient concentrations supplemented with and without phytase on WI and excretion. It was noted that excreta moisture content was reduced (P<0.001) as nutrient density decreased whereas nutrient density had no effect (P>0.05) on the cumulative WI. Water output (g/g of weight gain) was higher (P<0.05) for phytase-fed birds but nutrient density had no effect (P>0.05).
In the next two experiments floor-pen studies were used to examine the effects of nutrient density and dietary protein concentration (ranging from 77 to 120% of BUT breed recommendation) on litter quality parameters and, therefore, on leg health conditions. In one study the energy and protein ratio were kept constant whereas in the second the protein concentration changed while the energy remained constant (100% of breed requirement). Growth performance parameters were determined for each study which was conducted from 4 to 20 weeks of age. When birds were fed diets in which the energy and protein ratio remained constant the high protein/energy diets resulted in a lower WI and litter moisture content when compared to group fed diet containing lower concentrations of protein/energy (P<0.05). In contrast litter pH and NH3 concentration and prevalence of HB were higher when birds were fed with the high protein/energy diets. Notably there was no effect (P>0.05) of treatment on FPD.
Birds fed diets containing a higher than the recommended dietary protein concentration (constant energy concentration) had a higher WI and litter moisture content when compared to group fed diets containing the low nutrient density diets (P<0.001). Likewise, litter pH and NH3 concentration and prevalence of HB and FPD were higher where birds were fed the higher than recommended protein concentration diets.
The final experiment was designed to establish the relative importance of protein and potassium in determining WI and excretion. There were six treatments based on three diets containing either 77, 100 and 120% of the dietary protein recommended by the breeder. Each diet was then split into two and one of the two diets was supplemented with K2CO3 to give a K+ concentration of 16.5 g/kg of diet. The remaining diet of the pair was left unsupplemented (ie contained only naturally occurring potassium). It was noted that birds fed with diet containing higher dietary protein concentration had higher WI and moisture output (MO) when compared to group fed diet containing lower dietary protein concentration (P<0.001). The effect within diets containing the same CP and standardised K+ was marginally insignificant (P=0.065) in terms of WI. Whereas birds fed diets containing naturally occurring K+ only had approximately 10% less (P<0.05) MO compared to these fed diets containing the standardised concentration of K+.
While recognising that factors such as non-starch polysaccharides (NSP), indigestible fat and trypsin inhibitor could not be excluded totally, it was concluded, on the basis of the experiments conducted, that dietary protein (as provided by soybean meal) was primarily responsible for the higher WI and hence excretion. This then ultimately produces unacceptable litter quality and results in leg health problems in turkeys. To prevent excessive water intake and reduce litter moisture content there should be a correct balance between dietary energy and protein levels. Feeding turkeys lower ideal protein diets containing higher apparent metabolisable energy ratio crude protein (AME:CP) may help to improve the amino acid digestibility and ionic balance and, therefore, litter quality and this will help to decrease leg health problems such as footpad dermatitis and hock burn.
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