ARI Volume 2 Number 1.pdf - Zoo-unn.org

Animal waste management strategies 269Increase digestible P (g/Kg)1.41.210.80.60.40.20Corn/soy dietBy-product diet0 450 900 1350 1800 2250Phytase (FTU/Kg)Figure 1: Improvement in digestible P bymicrobial phytase (Natuphos) in two dietsfor growing pigs (Beers and Jongbloed,1992)(based either on corn-soybean meal or phytaterichby-products). The efficiency of microbialphytase appeared to be related to its dose and thetype of diet (Figure 1).From 0 – 400 FTU/Kg there was a rapidincrease in microbial phytase efficacy, whichflattened afterwards. In the experiment, it wasshown that microbial phytase was considerablyeffective in enhancing phosphorus digestion andso increases the amount of digestible /availablephosphorus in the feed for pigs.Approximately 67 % of the phosphorus in planttissue is in the form of phytate phosphorus(Myoinositol hexakisphosphate) (Cromwell et al.,1993), which is only minimally available tomonogastric animals since they lack the phytaseenzyme that hydrolyses phytic acid to inositoland/or thophosphate (Peeler, 1972).Supplementation of phytase enzyme in cornsoybeanmeal diet of broiler chickens improves theavailability of phytate bound phosphorus (Simonset al., 1992; Edens et al., 1999). Phytatephosphorus content of corn is 68% of the totalphosphorus, and in soybean meal phytatephosphorus represents 60 % of the totalphosphorus (Edens et al. 1999). Simons et al(1990) demonstrated that in three-week-oldbroilers the availability of dietary phosphorus couldbe increased up to 65 % by means ofsupplemental dietary phytase while reducing fecalphosphorus by 50 %. Furthermore, inclusion ofphytase activity in diets having wheat, triticale,rye, or their by-products resulted in betterphosphorus utilization in poultry (Choct, 2001).The efficacy of microbial phytase depends onanimal related factor such as physiological statusand housing condition (Kemme et al. 1997a).Kemme et al. (1997b) showed that the efficacy ofphytase in generating digestible phosphorusdecreased in the order of lactating sows, growingfinishingPigs, sows at the end of pregnancy,piglets and sows at mid pregnancy.A prerequisite for a good evaluation ofmicrobial phytase efficacy is that the animal be fedbelow their phosphorus requirement. This is due tointestinal regulation of phosphorus absorptionwhen animals are fed above their phosphorusrequirement. It is commonly known that higherdietary calcium levels decrease apparentabsorption of phosphorus. Thus a balance ofcalcium: phosphorus must be established forexcellent performance (Jongbloed, 1993).Reducing Nitrogen Excretion throughNutrition: To reduce the level of nitrogen in fecalmatter through nutrition, two approaches arepossible thus: (I) Enhancement of the depositionof nitrogen in animal products (meat, eggs, milk)and (ii) constant maintenance reduction of dietarynitrogen input while productivity is sustained(Tamminga and Verstegen, 1992). The firstapproach requires the intermediary metabolism tooperate more efficiently, while the secondapproach largely depends on reducing nitrogenlosses along the gastro-intestinal tract.Both approaches will result in a reductionof Nitrogen in animal excreta by 20 %. A moreefficient intermediary metabolism will reducenitrogen excretion in urine by 10 %, whereas areduction in losses from gastro-intestinal willreduce quantities present in both faeces and urineby 30 % (Lenis and Jongbloed, 1994). Feedingration containing a poor balance of amino acidsresults in removal of excess nitrogen in the faeces.Taylor, et al. (1979) indicated that the dietarycontent of total crude protein could be reducedfrom 17.6 % to 14.5 % by the addition ofcrystalline lysine. This leads to improved balanceof essential amino acids present in the diet andbetter protein utilisation.Inclusion of protease in the diet may alsopromote more efficient utilization of dietary protein(Headon and Walsh, 1994). The endogenousproteolytic activities associated with the digestivetract are normally more than adequate to promoteefficient degradation of dietary protein. Forinstance supplementation of feeds with exogenousmicrobial proteolytic activities can serve to improveprotein utilization in animals subject to highprotein intake.Cellulase help in the breakdown of cellwall structure and make nutrients in vegetablematerials much more available to the animal, theyalso break down xylan in cereal grains and reduceviscosity of the digester. The increase in the transittime in the gut leads to increase efficiency ofutilization. The enzyme activation may also help