Vitamin premix reduction in broiler chickens' diet negatively impacts growth, feed intake, feed conversion ratio, small intestine growth, and health

Vitamin and mineral premix are the most expensive poultry diet ingredients and can account for nearly 3-6% of the total diet cost. To reduce the production cost, this study aimed to investigate the impact of reduced levels of vitamin premix below the strain guide in the broiler chickens' diet on their performance, internal organ weight, intestinal growth and health, blood lipid profile, and liver enzyme activity. 200 Ross 308 one-day-old broilers, arranged into five treatments with four replicates, each with ten chicks in a completely randomized manner. The diet was based on corn-soybean meal and given in pellets. The experimental groups were supplemented with a 1, 2, 3, 4, and 5 g/kg vitamin premix. The reduced vitamin premix level in the broilers' diet led to a linear decline in feed intake (FI), weight gain (WG), and body weight at all rearing phases significantly (P&lt;0.05) and increased feed conversion ratio at starter and grower phases. Also, the mortality rate increased linearly with a reduced vitamin premix level in the diet insignificantly (P&gt;0.05). However, internal organ weight and length were not influenced by the reduction in the level of vitamins except for jejunum, and ceca length and ileum weight were increased linearly (P&lt;0.05). In addition, intestinal histomorphology, serum lipid profile, liver enzymes, glucose, and uric acid levels were not significantly affected by the reduced vitamin levels in the broilers' diet (P&gt;0.05). In conclusion, reducing vitamin premix levels in the broilers' diet does not adversely affect relative organ weight, intestinal health, and sera biochemical parameters. However, reducing vitamin levels in the broilers' diet to lower than the strain guide led to a decline in FI, WG, and performance of the broiler chickens and an increased mortality rate.维生素矿物质预混料是家禽日粮中成本最高的原料，约占日粮总成本的3%至6%。为降低生产成本，本研究旨在探究肉鸡日粮中维生素预混料添加量低于品系指南水平对其生产性能、内脏器官重量、肠道发育与健康、血清血脂谱及肝脏酶活性的影响。本试验选用200只1日龄罗斯308（Ross 308）肉鸡，采用完全随机设计分为5个处理组，每组设置4个重复，每个重复包含10只肉鸡。试验日粮以玉米-豆粕为基础，制成颗粒料，各试验组分别添加1、2、3、4、5 g/kg的维生素预混料。结果显示，肉鸡日粮中维生素预混料添加量降低可显著线性降低各饲养阶段的采食量（Feed Intake, FI）、增重（Weight Gain, WG）以及体重（P<0.05），并升高育雏期与育成期的饲料转化率。同时，日粮维生素预混料添加量降低会使死亡率呈线性升高趋势，但差异不显著（P>0.05）。除空肠外，内脏器官重量与肠道长度未受维生素添加量降低的影响；而盲肠长度与回肠重量呈线性升高（P<0.05）。此外，日粮维生素水平降低对肉鸡的肠道组织形态学、血清血脂谱、肝脏酶活性、葡萄糖及尿酸水平均无显著影响（P>0.05）。综上，降低肉鸡日粮中的维生素预混料添加量，并不会对相对器官重量、肠道健康及血清生化指标产生不利影响。但当日粮维生素预混料添加量低于品系指南水平时，会导致肉鸡的采食量、增重及生产性能下降，同时死亡率升高。