Abstract

ZAPATA, Carlos et al. Effect of the partial substitution of the diet protein by urea on dry matter intake and productive performance in lambs. Zootecnia Trop. [online]. 2004, vol.22, n.1, pp.29-48. ISSN 0798-7269.

To evaluate the effect of the partial substitution of the feed protein by urea (U) on dry matter intake (DMI) and on daily weight gain (DWG) in lambs, two experiments were undertaken in the Ovine Unit in the Ceniap-INIA, Venezuela. In the first, twenty West African lambs (av. wt. 21±1.5 kg) were assigned to five diets, where urea replaced part of the protein from fishmeal (FM). In the second, twenty West African lambs (av. wt. 14±0.48 kg) were assigned to five diets where urea replaced the protein from soybean meal (SBM). In both experiments, urea was included at the levels of 0, 1, 1.5, 2 and 3% of the supplement. The daily ration of lambs was 300 g of supplement plus chopped hay of Bermuda grass (Cynodon dactylon) offered ad libitum. In the first experiment with FM, the daily intake of MS was the same among treatments, averaging 904.2±43 g/d. DWG was found to be different among treatments (P<0,05), with the higher value for 1,5, 2 and 3% U (60.0, 67,5 and 3% U (61.0). The 1% U (32.5) was similar to the control (40.0). Similarly, feed conversion was improved (P<0.05) for the treatments with 1.5, 2 and 3% U, with values of 16, 15.5 and 14.8, respectively, which were lower than control (21.0) and 1% U (27.5) treatments. In the second experiment with SBM, there were observed differences (P<0.05) in DMI between control (0% U) and 1% U treatments (763.07 vs. 631.82 g/d). Higher levels of U showed intermediate values (654.77, 688.41 and 717.72 g/d, for 1.5, 2 and 3% U levels, respectively). DWG was significantly different among treatments, with the highest gain for the treatment with 1% U (98.75 g/d). This value for 1.5% U (75.42 g/d) was similar to control (75.00 g/d). Higher levels of substitution showed intermediate gains (87.92 and 88.75 g/d for the 2 and 3% U treatments, respectively). In this experiment, feed conversions were similar among treatments, with an overall value of 8.27. Independently of the protein source, in this experience, urea replaced the protein of the daily ration, without affecting lamb’s growth, approximately 25%.

Keywords : protein; urea; lambs; dry matter intake; daily weight gain.