Trinta leitões machos castrados mestiços foram distribuídos em baias individuais, de acordo com o peso inicial, em seis blocos com cinco tratamentos cada um, onde o farelo de algodão constituiu 0, 25, 50, 75 e 100% da fonte protéica respectivamente para os tratamentos 1, 2, 3, 4 e 5. O período experimental foi de 91 dias e, os pesos médios inicial e final foram, respectivamente, 23,57 e 91,14kg. A ração e a água foram fornecidas à vontade. As rações possuíam 16% de P. B. para o período de crescimento, e 13% para o de acabamento. Após 91 dias de ensaio, foi observado que o aumento de porcentagem de farelo de algodão na ração resultou em efeitos negativos lineares para ganho de peso (P < 0,05), e quadrático, para conversão alimentar (P < 0,05). As regressões não mostraram efeito significativo dos tratamentos sobre rendimento e comprimento da carcaça; no entanto, houve um efeito linear negativo sobre a espessura do toicinho (P < 0,05), porcentagem do pernil (P < 0,01) e área cio olho de lombo (P < 0,01).

Thirty “three-cross” harrows were alloted lo the treatments according to weight. The soybean meal was substituted by increasing levels of cottonseed meal as protein source (100:0; 75:25; 50:50; 25:75; and 0:100). The experiment lasted91 days and the initial and final average weights were 23.57 and 91.14kg respectively. Rations and water were given individually “ad libitum”. The rations had 16% CP during the growing period (23.57 to 55-60kg) and 13% CP during the finish period (55-60 to 91.14kg). At the end of the trial it was observed that increasing cottonseed meal levels resulted in a negative quadratic effect in gain of weight (P < 0.05) and a negative quadratic effect in feed efficiency (P < 0.05). The worst feed efficiency was obtained in the treatments 4 and 5. The treatment 5 was significantly (P < 0.05) inferior to the others. Regression analyses did not show any significative effect of treatment on carcass dressing percentage and lengh, but had a negative linear effect on the backfat thick-ness (P < 0.05), percentage of ham (P < 0.01) and loin eye area (P < 0.01).The percentage of ham in treatment 5 was significantly inferior (P < 0.05) to the others. The treatment 4 was significantly inferior (P < 0.05) to treatment 2 but not to treatment 1 and 3. The loin eye area in treatment 5 was significantly inferior (P < 0.05) to the others.The present trial shown that a 50-50% combination of cottonseed meal and soybean meal was superior to the others.