IMPACT OF INORGANIC FERTILIZATION ON SORGHUM FORAGE QUALITY AND GROWTH PERFORMANCE OF BARKI LAMBS

The present study was conducted at Maryout Research Station, Desert Research Center. It was applied in two experiments (Agronomy and fodder evaluation experiment and animal growth experiment) to determine the response of sorghum quality and consequently the animal performance to the application of combined N and P fertilizer in newly reclaimed soil. The first experiment was for evaluating sorghum fodder (Sorghum bicolor L.) that sorted with nine treatment combinations (from T1 up to T9) comprising of three nitrogen (N) and phosphorus (P) fertilizers levels (N80.4, N100.5 and N120.6 kg/feddan vs. P20.2, P30.2 and P40.3 kg/feddan) in factorial randomized block design with three replications. The results of the agronomy experiment with considering the ISDMD, NEg and the cost of treatments, showed that two treatments (N120P30 and N100P40) could be nominated to the second experiment which was their evaluation as feeds for the growing Barki lambs as compared to control treatment (N80P20). So, two treatments and control were sorting again in the next summer season to evaluate their nutritive values by using 15 growing Barki lambs (5 lambs/ treatment) in a completely randomized block design. Lambs were on average 22.83 ± 0.29 kg as the initial body weight and aged 5 months. All animals fed concentrate feed mixture to cover 70% of their growth requirements (Kearl, 1982). However, the experimental fodders were offered ad lib. So the experimental animal groups were allowed for three rations for 85d as follows; R1: CFM + sorghum forage of T1 (N80P20) ad lib. , (served as a control), R2: CFM + sorghum forage of T6 (N120P30) ad lib, and R3: CFM + sorghum forage of T8 (N100P40) ad lib. The results indicated that; Average daily gain differed significantly (P= 0.016) being values 158, 185 and 192g for lambs fed R1, R2 and R3, respectively. Animals in R2 and R3 consumed a higher (P=0.042) amount of sorghum compared with the control one. There is a significant effect (P 0.05) by the experimental rations. Both R2 and R3 were the better (P 0.05) amounts of calcium. However, higher P content in sorghum of R2 and R3 revealed significantly higher P intake (P<0.05) and also P retained (P<0.05). The revealed insensible water loss (IWL) of the three groups was significantly different being values 144, 172 and 176 g/kg0.82 for R1, R2 and R3, respectively. The rumen pH value of animal group fed control ration (R1) was significantly (P≤0.001) higher than other groups at all the sampling time. Animals who received R2 ration showed the highest NH3-N values at 3h (P<0.01) and 6h (P<0.05) post-feeding as compared to the other groups; however R3 group showed the highest (P<0.05) value at zero hour post-feeding as compared to the groups. At 6h post-feeding, animals fed R2 showed the highest (P<0.05) TVFA value (22.14meq/dl) as compared to the other groups (19.68 and 21.45 meq/dl for R1 and R3, respectively). It could be concluded that both of the sorghum treatments; N120P30 and N100P40 kg/fed; are in the same nutritive values and similar growth rate for Barki lambs but because of higher P drain away to the land below in case of N100P40 ration so it is recommended for N120P30 to be a better fertilizer rate for the fodder consumed by the Barki lambs and also for its potential to reduce the environmental pollution with the high level of P compared to the other treatment.