动物营养学报    2017, Vol. 29 Issue (10): 3530-3540    PDF    
饲养密度和高蛋白质饲粮代谢能水平对公母分饲肉鸡生长性能和腿部健康的影响
范庆红1,2, 王晓晓3, 董晓1, 孙作为3     
1. 青岛农业大学生命科学学院, 青岛 266109;
2. 山东省莱州市畜牧兽医站, 莱州 261400;
3. 山东玖瑞农业集团有限公司, 青岛 266061
摘要: 本试验旨在研究饲养密度与高蛋白质(前期23%,后期21%)饲粮代谢能水平对公母分饲肉鸡生长性能和腿部健康的影响。试验采用2(性别)×2(饲养密度)×3(饲粮代谢能水平)三因子完全随机设计,选用1日龄罗斯308(Ross 308)肉鸡公雏1 872只和母雏2 160只,随机分成12个组,每组8个重复。试验设高、低2个饲养密度,以出栏体重计,分别为42[高饲养密度(HSD),16公/m2或18母/m2]和26 kg/m2[低饲养密度(LSD),10公/m2或12母/m2]。试验饲粮分前期(1~21日龄)和后期(22~35日龄)2个阶段配制,饲粮代谢能设高、中、低3个水平,其中,高代谢能(HME)水平饲粮前期和后期的代谢能水平分别为12.81和13.23 MJ/kg,中代谢能(MME)水平饲粮前期和后期的代谢能水平分别为12.18和12.60 MJ/kg,低代谢能(HME)水平饲粮前期和后期的代谢能水平分别为11.55和11.97 MJ/kg。结果表明:1)饲养密度与饲粮代谢能水平对肉鸡的平均日增重和料重比有显著交互作用(P<0.05)。1~21日龄时,随着饲粮代谢能水平增加,HSD组平均日增重的增加幅度和料重比的降低幅度均小于LSD组;22~35日龄时结果正好相反。性别与饲养密度对肉鸡的平均日采食量有显著交互作用(P<0.05)。随着饲养密度增加,公鸡平均日采食量的降低幅度大于母鸡。2)HSD极显著降低肉鸡的胸肌率(P<0.01),母鸡的胸肌率和腹脂率显著高于公鸡(P<0.05)。饲粮代谢能水平和饲养密度对肉鸡的腿肌率有显著交互作用(P<0.05)。随着饲粮代谢能水平增加,LSD组肉鸡的腿肌率降低,而HSD组基本不变。3)高饲粮代谢能水平极显著降低肉鸡的脚垫损伤评分(P<0.01),公鸡的步态评分和脚垫损伤评分显著高于母鸡(P<0.05),垫料水分含量显著低于母鸡(P<0.05)。饲粮代谢能水平与饲养密度对肉鸡的脚垫损伤评分有显著交互作用(P<0.05)。随着饲粮代谢能水平增加,HSD组脚垫损伤评分的降低幅度大于LSD组。以上结果表明,高饲养密度降低肉鸡的平均日增重,增加料重比;35日龄前,公鸡比母鸡的空间需求更高;提高高蛋白质饲粮的代谢能水平可以缓解HSD对肉鸡生长性能和脚垫健康的不利影响。
关键词: 饲养密度     饲粮代谢能水平     性别     生长性能     腿部健康     肉鸡    
Effects of Stocking Density, Sex and Dietary Metabolizable Energy Level in a High-Protein Diet on Growth Performance and Leg Health of Broiler Chickens
FAN Qinghong1,2, WANG Xiaoxiao3, DONG Xiao1, SUN Zuowei3     
1. College of Life Science, Qingdao Agricultural University, Qingdao 266109, China;
2. Laizhou Animal Husbandry and Veterinary Station, Laizhou 261400, China;
3. Jiurui Agricultural Group Co., Ltd., Qingdao 266061, China
Abstract: This study was conducted to investigate the effects of stocking density, sex and dietary metabolizable energy (ME) level in a high-protein (23% in early phase and 21% in later phase) diet on growth performance and leg health of broiler chickens. According a 2 (sex)×2 (stocking density)×3 (dietary ME level) three-factor completely randomized design, 1 872 male and 2 160 female 1-day-old Ross 308 broiler chickens were allotted into 12 groups with 8 replicates per group. Two stocking densities were designed in this experiment:42[high stocking densities (HSD), 16 males/m2 or 18 females/m2] and 26 kg market weight/m2[low stocking densities (LSD), 10 males/m2 or 12 females/m2], respectively. The experiment contained early phase (1 to 21 days of age) and later phase (22 to 35 days of age), and dietary ME levels divided into high, middle and low levels. The ME levels of high ME (HME) level diet were 12.81 and 13.23 MJ/kg, the ME levels of middle ME (MME) level diet were 12.18 and 12.60 MJ/kg, and the ME levels of low ME (LME) level diet were 11.55 and 11.97 MJ/kg in early phase and later phase, respectively. The results showed as follows:1) stocking density and dietary ME level had significant interactions on average daily gain (ADG) and the ratio of feed to gain (F/G) of broiler chickens (P < 0.05). Increase range of ADG and decrease range of F/G from 1 to 21 days of age in HSD group were lower than those in LSD group with the increase of dietary ME level, however, the results were the opposite from 22 to 35 days of age. Sex and stocking density had significant interaction on average daily feed intake (ADFI) of broiler chickens (P < 0.05). Decrease range of ADFI of male broilers was higher than that of female broilers with the increase of stocking density. 2) HSD significantly decreased breast muscle yield of broiler chickens (P < 0.01), and breast muscle yield and abdominal fat percentage of female broilers were significantly higher than those of male broilers (P < 0.05). Stocking density and dietary ME level had significant interactions on thigh muscle yield of broiler chickens (P < 0.05). Thigh muscle yield of broiler chickens in LSD group was decreased, but there was no change in HSD group with the increase of dietary ME level. 3) Dietary HME level significantly decreased footpad burn score of broiler chickens (P < 0.01), gait score and footpad burn score of male broilers were significantly higher than thaose of female broilers (P < 0.05), and litter moisture content of male broilers was significantly lower than that of female broilers (P < 0.05). Stocking density and dietary ME level had significant interaction on footpad burn score of broiler chickens (P < 0.05). Decrease range of footpad burn score in HSD group was higher than that of LSD group. In conclusion, HSD decreases ADG and increases F/G of broiler chickens, male broilers need more space than the female before 35 days of age, increasing ME level in the high-protein diet can alleviate the negative effects of HSD on growth performance and footpad health.
Key words: stocking density     dietary metabolizable energy level     sex     growth performance     leg health     broiler chickens    

高饲养密度(HSD)(>35 kg/m2)会降低肉鸡的采食量、日增重和饲料转化率,影响其行走能力和脚垫健康[1-8]。饲养密度对肉鸡的影响是一个综合效应,涵盖群体大小、料位、垫料质量等因素。研究发现,肉鸡对生长空间的需求存在性别和年龄差异,HSD对公鸡的不利影响主要见于前期(1~21日龄),而对母鸡的不利影响则主要在后期(35~42日龄)[9]。在HSD条件下,肉鸡的运动量减少,故其营养需求量可能发生改变,尤其是能量。能蛋比是一项重要的营养平衡指标,Sun等[10]研究报道,在正常饲粮蛋白质水平下,提高饲粮能量水平不能缓解HSD对肉鸡的不利影响,而这是否与饲粮蛋白质水平较低有关尚需进一步验证。因此,本试验旨在研究饲养密度、性别和高蛋白质饲粮代谢能(ME)水平对肉鸡生长性能和腿部健康的交互作用,以期更好地指导生产实践。

1 材料与方法 1.1 试验动物与饲养管理

选用1日龄罗斯308(Ross 308) 肉鸡公雏1 872只和母雏2 160只,以稻壳为垫料,分96栏(2.0 m×1.6 m)地面平养,每栏配备料筒和乳头式水线。育雏温度最初2天为34 ℃[相对湿度(RH)为50%],以后每周降低2 ℃,直至26 ℃(RH为45%)为止。试验鸡群按正常程序免疫。每天光照时间如下:第1天,22 h;第2~3天,19 h;第4~6天,16 h;第7~12天,14 h;第13~22天,12 h;第23~30天,15 h;第31~35天,16 h。在整个试验期间,肉鸡自由采食和饮水。鸡舍环境自动控制,舍内温度、湿度、光照和卫生学指标均符合国家标准(GB/T 14925—1994)。

1.2 试验设计

试验采用2(性别)×2(饲养密度)×3(饲粮代谢能水平)三因子完全随机设计,共12个组,每组8个重复。以出栏体重计,2个饲养密度分别为42(HSD)和26 kg/m2[低饲养密度(LSD)]。其中,HSD对应公鸡48只/栏(16只/m2)和母鸡54只/栏(18只/m2),LSD对应公鸡30只/栏(10只/m2)和母鸡36只/栏(12只/m2)。每栏饲养只数在1日龄时按照公鸡和母鸡预估上市体重分别为2.6和2.3 kg确定,终末净面积以3.0 m2计。1~21日龄时,每个饲喂器的容量为2.5 kg,HSD公、母鸡的料位分别为2.6和2.3 cm,LSD公、母鸡的料位分别为4.2和3.5 cm;22~35日龄时,每个饲喂器的容量为8.5 kg,HSD公、母鸡的料位分别为4.0和3.5 cm,LSD公、母鸡的料位分别为6.3和5.2 cm。

试验饲粮分前期(1~21日龄)和后期(22~35日龄)2个阶段配制,代谢能设高、中、低3个水平,其中,高代谢能(HME)水平饲粮前期和后期的代谢能水平分别为12.81和13.23 MJ/kg,中代谢能(MME)水平饲粮前期和后期的代谢能水平分别为12.18和12.60 MJ/kg,低代谢能(LME)水平饲粮前期和后期的代谢能水平分别为11.55和11.97 MJ/kg。饲粮蛋白质水平前期和后期分别为23%和21%,其他营养水平均参照NRC(1994) 标准,试验饲粮组成及营养水平见表 1

表 1 试验饲粮组成及营养水平(风干基础) Table 1 Composition and nutrient levels of experimental diets (air-dry basis)
1.3 测定指标及方法 1.3.1 生长性能测定

在每个饲养阶段末(21和35日龄时),以重复(栏)为单位,对鸡群进行空腹称重并统计剩料量,以计算平均日增重(ADG)、平均日采食量(ADFI)和料重比(F/G)。

1.3.2 步态和脚垫损伤评分

35日龄时,每个重复随机选取2只鸡进行步态和脚垫损伤评分。步态评分参照Garner等[11]改进的方法,标准如下:0分=步态正常,无行走障碍;1分=步态异常,有行走障碍;2分=不愿行走或站立,运动能力严重受损。脚垫损伤评分采用Bilgili等[12]描述的方法,标准如下:0分=脚垫无损伤;1分=脚垫轻微损伤,伤口直径不足0.75 cm;2分=脚垫损伤较重,伤口直径介于0.75~1.50 cm之间;3分=脚垫严重受损,伤口直径大于1.50 cm。

1.3.3 胴体组成测定

在步态和脚垫损伤评分结束后,对所选每只鸡进行称重,屠宰。取胸肌、腿肌和腹脂,逐一称重,计算器官指数(100×器官重/体重,%)。

1.3.4 垫料水分含量测定

35日龄时,每个鸡栏选择5个不同的位点(四角和中心),采集垫料样本(全厚),合在一起并混合均匀后,按照AOAC 930.15标准测定垫料水分含量。

1.4 统计分析

使用SAS 9.0软件的一般线性模型(GLM)程序对试验数据进行三因素方差分析(three-way ANOVA),当主效应或互作效应显著(P<0.05) 时,采用Duncan氏法对相关均值进行多重比较。

2 结果 2.1 生长性能

表 2可知,1~21日龄时,饲养密度与饲粮代谢能水平对肉鸡的平均日增重和料重比有显著交互作用(P<0.05)。随着饲粮代谢能水平增加,HSD组平均日增重的增加幅度(MME vs. LME,-0.44%;HME vs. LME,+0.99%)小于LSD组(MME vs. LME,+1.32%;HME vs. LME,+3.96%),HSD组料重比的降低幅度(MME vs. LME,-2.81%;HME vs. LME,-7.02%)小于LSD组(MME vs. LME,-4.55%;HME vs. LME,-8.04%)。饲粮代谢能水平、饲养密度和性别对肉鸡的料重比有显著交互作用(P<0.05)。随着饲粮代谢能水平增加,HSD组公鸡料重比的降低幅度(MME vs. LME,-4.26%;HME vs. LME,-7.80%)大于母鸡(MME vs. LME,-1.39%;HME vs. LME,-6.25%),LSD组母鸡料重比的降低幅度(MME vs. LME,-4.79%;HME vs. LME,-8.22%)大于公鸡(MME vs. LME,-4.29%;HME vs. LME,-7.86%)。

表 2 饲养密度和高蛋白质饲粮代谢能水平对1~21日龄公母分饲肉鸡生长性能的影响 Table 2 Effects of stocking density, sex and metabolizable energy level in a high-protein diet on growth performance of broiler chickens from 1 to 21 days of age (n=8)

表 3可知,22~35日龄时,饲养密度与饲粮代谢能水平对肉鸡的平均日增重和料重比有显著交互作用(P<0.05)。随着饲粮代谢能水平增加,HSD组的平均日增重增加(MME vs. LME,+3.56%;HME vs. LME,+11.53%),LSD组的平均日增重降低(MME vs. LME,-0.79%;HME vs. LME,-0.49%);HSD组料重比的降低幅度(MME vs. LME,-7.48%;HME vs. LME,-13.46%)大于LSD组(MME vs. LME,-0.51%;HME vs. LME,-3.30%)。性别与饲养密度对肉鸡的平均日采食量有显著交互作用(P<0.05)。随着饲养密度增加,公鸡平均日采食量的降低幅度(HSD vs. LSD,-9.14%)大于母鸡(HSD vs. LSD,-6.54%)。

表 3 饲养密度和高蛋白质饲粮代谢能水平对22~35日龄公母分饲肉鸡生长性能的影响 Table 3 Effects of stocking density, sex and metabolizable energy level in a high-protein diet on growth performance of broiler chickens from 22 to 35 days of age (n=8)

表 4可知,1~35日龄时,饲养密度与饲粮代谢能水平对肉鸡的料重比有显著交互作用(P<0.05)。随着饲粮代谢能水平增加,HSD组料重比的降低幅度(MME vs. LME,-4.85%;HME vs. LME,-9.97%)大于LSD组(MME vs. LME,-2.03%;HME vs. LME,-5.52%)。性别与饲养密度对肉鸡的平均日采食量有显著交互作用(P<0.05)。随着饲养密度增加,公鸡平均日采食量的降低幅度(HSD vs. LSD,-6.66%)大于母鸡(HSD vs. LSD,-4.58%)。

表 4 饲养密度和高蛋白质饲粮代谢能水平对1~35日龄公母分饲肉鸡生长性能的影响 Table 4 Effects of stocking density, sex and metabolizable energy level in a high-protein diet on growth performance of broiler chickens from 1 to 35 days of age (n=8)
2.2 胴体组成

表 5可知,HSD显著降低肉鸡的胸肌率(P<0.01),母鸡的胸肌率和腹脂率显著高于公鸡(P<0.05)。饲粮代谢能水平和饲养密度对肉鸡的腿肌率有显著交互作用(P<0.05)。随着饲粮代谢能水平增加,LSD组肉鸡的腿肌率降低(MME vs. LME,-5.96%;HME vs. LME,-5.64%),而HSD组基本不变(MME vs. LME,-1.64%;HME vs. LME,-0.99%)。

表 5 饲养密度和高蛋白质饲粮代谢能水平对35日龄公母分饲肉鸡胴体组成的影响 Table 5 Effects of stocking density, sex and metabolizable energy level in a high-protein diet on carcass composition of broiler chickens at 35 days of age (n=8)
2.3 腿部健康和垫料水分含量

表 6可知,高饲粮代谢能水平显著降低肉鸡的脚垫损伤评分(P<0.01),公鸡的步态评分和脚垫损伤评分显著高于母鸡(P<0.05),垫料水分含量显著低于母鸡(P<0.05)。饲粮代谢能水平与饲养密度对肉鸡的脚垫损伤评分有显著交互作用(P<0.05)。随着饲粮代谢能水平增加,HSD组脚垫损伤评分的降低幅度(MME vs. LME,-15.7%;HME vs. LME,-49.0%)大于LSD组(MME vs. LME,-15.5%;HME vs. LME,-34.0%)。

表 6 饲养密度和高蛋白质饲粮代谢能水平对35日龄公母分饲肉鸡腿部健康和垫料水分含量的影响 Table 6 Effects of stocking density, sex and metabolizable energy level in a high-protein diet on leg health and litter moisture content of broiler chickens at 35 days of age (n=8)
3 讨论 3.1 饲养密度和高蛋白质饲粮代谢能水平对公母分饲肉鸡生长性能和胴体组成的影响

本试验发现,1~35日龄时,HSD显著降低了肉鸡的平均日采食量和平均日增重,增加了料重比。这与Feddes等[3]和Dozier等[5]的研究结果一致,表明HSD降低了肉鸡的生长性能。Dozier等[4]认为,HSD导致肉鸡增重减缓,部分原因归结于采食量的减少。Sørensen等[7]推测,HSD对肉鸡生长性能的不利影响可能与肉鸡行动能力减弱、接触饲粮不便有关。本试验中,HSD增加了肉鸡的步态评分和脚垫损伤评分,说明肉鸡因腿疾而导致的采食困难可能是HSD降低其生长性能的重要原因。

为排除饲喂设施干扰,与其他研究[3, 5]相比,本试验肉鸡的单位采食空间(料位/只)更大。Collins等[13]报道,家禽天生喜欢聚集在料槽周围,这与饲养密度无关。Febrer等[14]认为,肉鸡是一种群居动物,HSD有助于催生它们的“社会”习性。这些研究说明,提供充足的采食空间可能有助于提高HSD肉鸡的采食量。

HSD降低了肉鸡的平均日采食量,为了弥补养分摄入的减少,本试验设计了3种不同代谢能水平的高蛋白质饲粮,以检验饲养密度与饲粮营养水平的交互作用。1~21日龄时,高饲粮代谢能水平对LSD肉鸡平均日增重和料重比的改善效果优于HSD;22~35日龄时,结果正好相反,说明HSD增加了肉鸡后期的代谢能需求量。

本试验比较了公鸡和母鸡在不同饲养密度条件下的生长性能。因为公鸡的生长速度较快,所以一般认为公鸡比母鸡需要更多空间。本研究中,HSD对公鸡平均日采食量的不利影响大于母鸡,尤其是在后期。这与前人研究结果[9-10]相一致,说明在35日龄之前,公鸡比母鸡的空间需求更高。

此外,Dozier等[5]报道,当饲养密度超过25 kg/m2时,随着饲养密度增加,小型肉鸡(体重1.5~1.8 kg时上市)的终末体重和胸肌产量都显著降低。与此相似,本试验发现,HSD显著降低了肉鸡的胸肌率。

3.2 饲养密度和高蛋白质饲粮代谢能水平对公母分饲肉鸡腿部健康与垫料水分含量的影响

与Sørensen等[7]报道一致,本试验中,HSD增加了肉鸡的步态评分,暗示降低饲养密度能够减缓腿病的发生。HSD加剧了肉鸡的脚垫损伤,Dozier等[5]认为,这其中有一部分原因与垫料潮湿有关。Dawkins等[15]在商业肉鸡养殖场所做的大型试验表明,导致肉鸡健康水平下降和死亡率增加的关键因素是由饲养密度引发的环境问题(如空气和垫料质量等),而非饲养密度本身。与Sørensen等[7]和Bilgili等[12]报道相似,本试验中,公鸡的步态评分和脚垫损伤评分都高于母鸡,表明公鸡的腿部健康状态更差。

Nelson等[16]报道,前期和中期饲喂低能量水平饲粮(为了减缓生长)不能降低肉鸡的腿病发生率(饲养8周)。本试验探讨了高蛋白质饲粮代谢能水平对肉鸡步态评分的影响,研究发现,尽管HME饲粮增加了肉鸡的体重,但是腿病的发生并没有加剧,说明体重大不是诱发肉鸡腿疾的主因。

Shepherd等[17]综述了营养因素与垫料质量之间的关系,表明LME水平饲粮加重了肉鸡的脚垫损伤。本试验中,LME水平饲粮增加了肉鸡的平均日采食量,降低了料重比,暗示粪便养分排泄量增多,而这可能会降低垫料质量。这一推论与Nagaraj等[18]报道一致,即饲粮蛋白质水平和来源显著影响肉鸡脚垫损伤的发生率和严重性。以上研究表明,饲喂营养均衡的饲粮可能会通过改善垫料质量缓解脚垫损伤的发生。

4 结论

① 高饲养密度降低肉鸡的平均日增重,增加料重比。

② 35日龄前,公鸡比母鸡的空间需求更高。

③ 提高高蛋白质饲粮的代谢能水平可以缓解HSD对肉鸡生长性能和脚垫健康的不利影响。

参考文献
[1]
PURON D, SANTAMARIA R, SEGURA J C, et al. Broiler performance at different stocking densities[J]. Journal of Applied Poultry Research, 1995, 4(1): 55-60. DOI:10.1093/japr/4.1.55
[2]
ESTEVEZ I, NEWBERRY R C, DE REYNA L A. Broiler chickens:a tolerant social system?[J]. Etología, 1997, 5: 19-29.
[3]
FEDDES J J R, EMMANUEL E J, ZUIDHOF M J. Broiler performance, body weight variance, feed and water intake, and carcass quality at different stocking densities[J]. Poultry Science, 2002, 81(6): 774-779. DOI:10.1093/ps/81.6.774
[4]
DOZIER W A, THAXTON J P, BRANTON S L, et al. Stocking density effects on growth performance and processing yields of heavy broilers[J]. Poultry Science, 2005, 84(8): 1332-1338. DOI:10.1093/ps/84.8.1332
[5]
DOZIER W A, THAXTON J P, PURSWELL J L, et al. Stocking density effects on male broilers grown to 1.8 kilograms of body weight[J]. Poultry Science, 2006, 85(2): 344-351. DOI:10.1093/ps/85.2.344
[6]
ESTEVEZ I. Density allowances for broilers:where to set the limits?[J]. Poultry Science, 2007, 86(6): 1265-1272. DOI:10.1093/ps/86.6.1265
[7]
SØRENSEN P, SU G, KESTIN S C. Effects of age and stocking density on leg weakness in broiler chickens[J]. Poultry Science, 2000, 79(6): 864-870. DOI:10.1093/ps/79.6.864
[8]
SANOTRA S G, LAWSON L G, VESTERGAARD K S, et al. Influence of stocking density on tonic immobility, lameness, and tibial dischondroplasia in broilers[J]. Journal of Applied Animal Welfare Science, 2001, 4(1): 71-87. DOI:10.1207/S15327604JAWS0401_4
[9]
孙作为, 吕明斌, 燕磊, 等. 饲养密度和饲粮赖氨酸水平对公母分饲肉鸡生长性能、胴体组成和健康状态的影响[J]. 动物营养学报, 2011, 23(4): 578-588.
[10]
SUN Z W, YAN L, YUAN L, et al. Stocking density affects the growth performance of broilers in a sex-dependent fashion[J]. Poultry Science, 2011, 90(7): 1406-1415. DOI:10.3382/ps.2010-01230
[11]
GARNER J P, FALCONE C, WAKENELL P, et al. Reliability and validity of a modified gait scoring system and its use in assessing tibial dyschondroplasia in broilers[J]. British Poultry Science, 2002, 43(3): 355-363. DOI:10.1080/00071660120103620
[12]
BILGILI S F, ALLEY M A, HESS J B, et al. Influence of age and sex on footpad quality and yield in broiler chickens reared on low and high density diets[J]. Journal of Applied Poultry Science, 2006, 15(3): 433-441. DOI:10.1093/japr/15.3.433
[13]
COLLINS L M, SUMPTER D J T. The feeding dynamics of broiler chickens[J]. Journal of the Royal Society Interface, 2007, 4(12): 65-72. DOI:10.1098/rsif.2006.0157
[14]
FEBRER K, JONES T A, DONNELLY C A, et al. Forced to crowd or choosing to cluster?Spatial distribution indicates social attraction in broiler chickens[J]. Animal Behaviour, 2006, 72(6): 1291-1300. DOI:10.1016/j.anbehav.2006.03.019
[15]
DAWKINS M S, DONNELLY C A, JONES T A. Chicken welfare is influenced more by housing conditions than by stocking density[J]. Nature, 2004, 427(6972): 342-344. DOI:10.1038/nature02226
[16]
NELSON T S, KIRBY L K, JOHNSON Z B. Effect of calcium, phosphorus, and energy level on the incidence of weak legs in heavy male broilers[J]. Journal of Applied Poultry Research, 1992, 1(1): 11-18. DOI:10.1093/japr/1.1.11
[17]
SHEPHERD E M, FAIRCHILD B D. Footpad dermatitis in poultry[J]. Poultry Science, 2010, 89(10): 2043-2051. DOI:10.3382/ps.2010-00770
[18]
NAGARAJ M, WILSON C A P, HESS J B, et al. Effect of high-protein and all-vegetable diets on the incidence and severity of pododermatitis in broiler chickens[J]. Journal of Applied Poultry Research, 2007, 16(3): 304-312. DOI:10.1093/japr/16.3.304