Abstract Faba beans ( Vicia faba L.) treated with formaldehyde (40%) at 0.5, 1.0 and 1.5% to protect its protein, were fed to goat kids in early growth stage for 90 days. Formaldehyde treatment improved significantly ( P < 0.01) DM and EE digestibilities, percent TDN, serum GPT, serum α-amino-nitrogen and daily BW gain in experimental groups compared to controls. Intake of DM and digestibilities of CP, CF and NFE, N retention, rumen metabolites, serum glucose, GOT and protein were apparently higher in experimental groups. Treatment of faba bean protein with formaldehyde (40%) at 1.5% reduced rumen ammonia 40.5%, lowered α-amino-N excretion in urine (26.7%), coupled with a 27.3% rise in serum N and 46.8% higher N retention. As a result, the BW gain was significantly ( P < 0.01) greater at the 1.0 and 1.5% levels of formaldehyde treatment. Feed conversion ratios were 6.9 and 6.3, respectively, as compared to 10.2 in controls. Treatment of faba beans with formaldehyde has potentials for better assimilation of N and BW gains in growing goat kids.