Amino acid composition, and determination and prediction of the protein digestibility of different sugarcane yeasts in broilers

ABSTRACT The aim of this study was to determine the amino acid composition and digestible protein values of different sugarcane yeasts, as well as to generate prediction equations for the apparent digestibility coefficient of dry matter (ADCDM) and crude protein (ADCCP), based on the chemical composition of the yeast and the age of the broilers. Four ileal digestion trials were carried out with 690 broilers, divided into the pre-starter, starter, growth and final phases. The birds were housed in metabolic cages and distributed in a completely randomised design, consisting of five treatments and six replications of eight, six, five and four birds respectively in each experimental phase. The treatments consisted of one reference feed and four test feeds, substituting 30% of the reference feed with four different yeasts. Yeasts two and four showed a higher percentage of amino acids. However, yeast two had the highest percentages of ADCDM, ADCCP and digestible protein: 83.64, 81.22 and 14.66% in the pre-starter phase; 78.09, 78.28 and 14.13% in the starter phase; 76.74, 74.75 and 13.49% in the growth phase; and 72.98, 71.21 and 12.85% in the final phase respectively. There was an average reduction of 0.424% in ADCDM and 0.428% in ADCCP for each day the birds aged. The following prediction equations were generated from the composition of the yeasts and age of the chickens: ADCDM = 77.4 - 0.424*(age) - 7.51*(DM) - 45.01*(EE) and - 0.424*(age) + 3.02*(CP) + 126.93*(EE) - 0.03*(GMD) and ADCCP = 606.9-0.428*(age) -5.8*(DM) - 0.01*(GMD) and -0.426*(age) + 2.68(CP) + 139.7*(EE) - 0.03*(GMD).

摘要
本研究旨在测定不同甘蔗酵母的氨基酸组成与可消化蛋白值，并基于酵母的化学组成及肉仔鸡日龄，建立干物质表观消化系数（apparent digestibility coefficient of dry matter, ADCDM）与粗蛋白表观消化系数（apparent digestibility coefficient of crude protein, ADCCP）的预测方程。本研究选用690羽肉仔鸡开展4项回肠消化试验，划分为育雏前期、育雏期、生长期及育肥期四个阶段。试验鸡只饲养于代谢笼中，采用完全随机试验设计，设置5个处理组，各试验阶段分别设置6个重复，每个重复的鸡只数依次为8羽、6羽、5羽与4羽。
处理组包含1种基础日粮与4种试验日粮，4种试验日粮均以30%的比例用不同甘蔗酵母替代基础日粮。结果显示，酵母2与酵母4的氨基酸占比更高；其中酵母2的干物质表观消化系数、粗蛋白表观消化系数与可消化蛋白占比均为最高，各阶段具体数值如下：育雏前期分别为83.64%、81.22%与14.66%；育雏期分别为78.09%、78.28%与14.13%；生长期分别为76.74%、74.75%与13.49%；育肥期分别为72.98%、71.21%与12.85%。
分析表明，肉仔鸡日龄每增加1天，干物质表观消化系数平均降低0.424%，粗蛋白表观消化系数平均降低0.428%。基于酵母化学组成与鸡只日龄，本研究建立了如下预测方程：
ADCDM = 77.4 - 0.424×(日龄) - 7.51×(干物质) - 45.01×(粗脂肪) - 0.424×(日龄) + 3.02×(粗蛋白) + 126.93×(粗脂肪) - 0.03×(GMD)
ADCCP = 606.9 - 0.428×(日龄) - 5.8×(干物质) - 0.01×(GMD) - 0.426×(日龄) + 2.68×(粗蛋白) + 139.7×(粗脂肪) - 0.03×(GMD)