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

UCHEWA, Emmanuel Nwafoagu et al. 270promote more efficient digestion of poorlydigestible proteins, such as those found in intimateassociation with some other dietary factors(Bateman 1998).In monogastric animals, proteindigestibility is low for some legume seeds, due tothe presence of anti-nutritional factors (ANF) likelectins and protease inhibitors (Tamminga andVerstegen 1994). Low protein digestion can beovercome by technological treatment of the diet inan optimal combination of temperature, moistureand time. Short treatment at high temperature ismore effective in reducing the antinutritional factorcontent of the dietary ingredient. Reduction in theactivity of proteinous ANF and further breakdownof non-starchy polysaccharides can beaccomplished using enzymes, during germinationand grinding to finer particle size.Beal et al. (1998) in a factorial analysisdemonstrated the difference in the in vitronitrogen digestibility between raw soybean anddifferent full fat soybean meals both with andwithout enzyme treatment at different p H (Table1). Surprisingly, they observed that raw soybeanappeared to be more digestible in pigs thanprocessed soybean meal. However, the pretreatmentof soybean with exogenous enzymesincreases protein digestibility. This is because largemolecular weight proteins are partially hydrolyzedbefore the commencement of digestion. Thedifference in nitrogen digestibility between the rawand processed soybean meal could be due to anumber of factors. Heat denaturation preventingdigestive enzymes to act on amino acid residues,differences in solubility due to the pH of thestomach and loss of available protein due to heatinduced interactions with other substances.Nitrogen excretion can also be reducedsubstantially by supplying dietary amino acids inaccordance with the animal’s requirement and byincorporating free amino acids in the feeds andlowering crude protein content.Multi phase feeding, in which diets can beautomatically adjusted by means of a computercontrolled feeding system may reduce excretion ofnitrogen and phosphorus by 10 and 15 to 22%,respectively. Bourdon and others achievednitrogen and phosphorus reduction applying multiphase feeding to castrated male pigs weighingbetween 25 and 100kg with decreased dietaryprotein levels, and supplementary addition oflimiting amino acids (VanKlooseter et al., 1998).From the experiments they concluded that theamount of nitrogen excreted was reduced by 50%, with multi phase feeding accounting for 0.10%. Van-der Peet-schwering et al. (1996) usingmultiphase feeding for growing and castrated malepigs between 25 and 110Kg live weight. Reportedthat multi phase feeding reduced ammoniaemission by 45%, compared to the single controldiet. Further more, multi phase feeding lead to 22% reduction in phosphorus excretion by growingpigs (Beers and Jongbloed 1992). Results ofKemme et al. (1997a, b) indicated that multi phasefeeding does not always lead to optimumperformance and slaughter quality of pigs.Requirements of nitrogen and phosphorusfor breeding sows are much lower duringpregnancy than during lactation. The use ofseparate diets for pregnancy and lactationcompared with one diet for both reduced theexcretion of nitrogen and phosphorus by 20 %(VanKlooseter et al., 1998).Growth promoters, because of improvedfeed conversion ratios have an estimated 7 and3% reduction on nitrogen and phosphorusexcretion per weaned piglet and growing pigrespectively, according to Jongbloed et al (1992).Both nitrogen and phosphorus excretion can befurther reduced with recombinant porcinesomatotropin (rPST) (Bateman 1998);unfortunately, the use of growth promoters in feedis banned.The source and level of fermentablecarbohydrates in the diet influence ammoniavolatilisation of pig slurry (Coppoolse et al. 1990).In an experiment, using three different treatments,Aarnink and Lenis (1998) fed soluble maize starchin treatment 1 and replaced it with coconutexpeller and soybean hulls in treatment II and IIIrespectively, ammonia volatilisation was decreasedunder laboratory conditions by 0.35%, 0.51% and0.36% respectively. In a second experiment, thesame authors examined the effect of electrolytebalance (Na + K – Cl), Ca-level and Ca-salt onammonia emission from slurry. When CaSO4, Ca –benzoate or CaCl2, replaced CaCO3 respectively,the ammonia emission of slurry under laboratoryconditions was reduced by 30%, 54% and 33%respectively.EFFECT ON THE PERFORMANCE OF THEANIMALThere have been numerous reports on the effectsof microbial phytase and phosphorus utilization. Inaddition to the general established improvementsin phosphorus digestibility, significantly higher liveweight gain and better-feed conversion efficiencyhave often been reported (Beers and Jongbloed,1992; Cromwell, 1980; Dungelhoef andRodehutscord, 1995 and Kemme et al., 1997a).This could be explained by interference of phyticacid with the digestion of other essential mineralsand protein. Phytate complexes in acid andalkaline media have been described (Dierick andDecuypere (1994). In vitro studies have shownthat phytate-protein complexes involving aminogroups of lysine, histidine and arginine are formed,which are insoluble and biologically unavailable in