Redalyc.Cobalt and Vitamin B12 in Diets for Commercial Laying Hens on the Second Cycle of Production

ABSTRACT The supplementation of cobalt and vitamin B 12 in diets for commercial laying hens on the second production cycle was studied. Four hundred and eighty light commercial laying hens, Lohmann LSL, were used at initial phase of forced molting laying period. The trial was conducted in a randomized design. The plots were the treatments which were constituted by combination of five cobalt levels (0.00; 0.30; 0.60; 0.90 and 1.20ppm) and two vitamin B 12 levels (without and with 10µ/kg) , and the split-plots were four periods (21, 42, 63 and 84 days) during the second period of production, with 4 repetitions and 12 hens per experimental unit. Food and water were provided ad libitum and eggs were collected twice daily. Performance and egg quality parameters were evaluated. At the end of experimental period, two layers from each treatment were slaughtered, and liver and blood samples were taken for analysis. Performance and egg quality were not different (p>0.05) among cobalt supplementation levels, although egg damage data were different (p<0.05). Supplementation with vitamin B 12 decreased egg weight. No influence of cobalt or vitamin B 12 supplementation was seen on the concentration of cobalt in the liver and yolk as well as on blood analysis (hematrocrit, hemoglobin, erythrocytes, and leukocytes). The results revealed that vitamin B 12 supplementation was important for commercial laying hens on the second cycle of production, but not cobalt supplementation

Protease Supplementation under Amino Acid Reduction in Diets Formulated with Different Nutritional Requirements for Broilers

ABSTRACT This study aimed to evaluate the effect of different reductions in digestible amino acids content (lysine, methionine, and threonine), according to two nutritional requirements in corn, soybean meal, and meat and bone meal based diets, with protease supplementation, on performance parameters and carcass characteristics. A total of 1080 day-old chicks, male, Cobb 500, were allotted to a completely randomized design, in a factorial arrangement 3 x 2, three reductions in digestible amino acids content (lysine, methionine, and threonine) and two nutritional requirements (Rostagno et al. 2005 and Cobb-Vantress Guidelines 2008), and all diets were supplemented with protease (200 ppm) with 6 replicates of 30 birds per pen. There was no significant interaction (p<0.05) between digestible amino acid reductions and both nutritional requirements for the performance variables and carcass yield and cuts. There was an effect of amino acid reduction and protease supplementation only on slaughter weight (p<0.05). Broilers fed according to the nutritional requirements of Rostagno et al. (2005) showed better (p<0.05) performance when compared to broilers fed as specified by the nutritional requirements of Cobb-Vantress (2008) with no significant differences in carcass characteristics. Protease supplementation of corn, soybean meal, and meat and bone meal based diets allows a reduction in the inclusion of crystalline amino acids (lysine, methionine, and threonine)