Resumen:
The objective of this study was to evaluate the effect of an exogenous phytase on in vitro residual
phosphorus (P) concentration and performance of 30 weaned ¾ Dorper vs ¼ Pelibuey lambs (12.12±1.46
kg BW). In vitro treatments were: 0 and 0.12 mg phytase per g of sorghum, corn gluten meal (CGM),
alfalfa hay and experimental diet (70% ground sorghum grain, 16.9% CGM, 12% alfalfa hay, 1.1%
calcium carbonate). There were significant (P<0.05) differences in the residual P concentration (%)
between 0 and 0.12 mg phytase at 24h of incubation, the values being 0.086 and 0.050 for ground sorghum
grain, 0.259 and 0.119 for CGM, 0.365 and 0.240 for alfalfa hay, and 0.276 and 0.240 for the mixed
diet with the corresponding 48h values of 0.054 and 0.048 for ground sorghum grain, 0.178 and 0.161 for
CGM, 0.198 and 0.131 for alfalfa hay, and 0.237 and 0.211 for the mixed diet. For the performance
trial, 30 lambs were allotted to three different groups using complete randomised design, and were fed
the experimental diet supplemented with 0, 6 or 12 g t-1 phytase. Parameters recorded were ADG, DM
intake, feed conversion (FC), apparent DM digestibility and faecal P excretion (FPE). Phytase
supplementation did not change (P>0.05) ADG (251, 294 and 266 g/d), DMI (905, 1119 and 975 g/d),
FC (4.06, 4.37 and 3.94). However, phytase addition increased DMD (72.34, 82.54 and 82.57%) and
FPE (1.01, 1.09 and 1.26 g/d). It may be concluded that apparent DM digestibility as well as faecal
excretion of phosphorus were affected when an exogenous phytase was added to a 70% sorghum grain
diet, fed to weaned Dorper x Pelibuey lambs.