Castro-Pérez Beatriz I, Estrada-Angulo Alfredo, Ríos-Rincón Francisco G, Núñez-Benítez Víctor H, Rivera-Méndez Carlos R, Urías-Estrada Jesús D, Zinn Richard A, Barreras Alberto, Plascencia Alejandro
Faculty of Veterinary Medicine and Zootechnics, Autonomous University of Sinaloa, Culiacán, Sinaloa 1084, México.
Sukarne Enterprise, Culiacán, Sinaloa 80300, México.
Asian-Australas J Anim Sci. 2020 Jun;33(6):1034-1041. doi: 10.5713/ajas.19.0112. Epub 2019 Aug 23.
The objective of this experiment was to evaluate the effect of shade allocation and shade plus fan on growth performance, dietary energy utilization and carcass characteristics of feedlot cattle under tropical ambient conditions.
Two trials were conducted, involving a total of 1,560 young bulls (289±22 kg BW) assigned to 24 pens (65 bulls/pen and 6 pens/treatment). Pens were 585 m2 with 15 m fence line feed bunks. Shade treatments (m2 shade/animal) were: i) limited shade (LS) to 1.2 m2shade/animal (LS1.2); ii) limited shade to 2.4 m2 shade/animal (LS2.4); iii) total shade (TS) which correspond to 9 m2/animal, and iv) total shade equipped with fans (TS+F). Trials lasted 158 and 183 days. In both studies, the average weekly maximum temperature exceeded 34°C.
Increasing shade allocation tended (p = 0.08) to linearly increases average daily gain (ADG), and dry matter intake (DMI, quadratic effect, p = 0.03). This effect was most apparent between LS1.2 and LS2.4. Shade allocation, per se, did not affect gain efficiency or estimated dietary net energy (NE). Compared with TS, TS+F increased (p<0.05) ADG, gain efficiency, and tended (p = 0.06) to increase dietary NE. There was a quadratic effect of shade on longissimus area and marbling score, with values being lower (p<0.01) for LS2.4 than for LS1.2 or TS. Likewise, marbling score was lower for TS+F than for TS. Percentage kidney, pelvic, and heart (KPH) linearly decreased with increasing shade. In contrast, KPH was greater for TS than for TS+F.
Providing more than 2.4 m2 shade/animal will not further enhance feedlot performance. The use of fans in combination with shade increases ADG and gain efficiency beyond that of shade, alone. These enhancements were not associated with increased DMI, but rather, to an amelioration of ambient temperature humidity index on maintenance energy requirement.
本实验的目的是评估在热带环境条件下，遮荫配置以及遮荫加风扇对育肥牛生长性能、日粮能量利用和胴体特性的影响。
进行了两项试验，共1560头青年公牛（体重289±22千克）被分配到24个栏舍（每个栏舍65头牛，每种处理6个栏舍）。栏舍面积为585平方米，有15米长的围栏式饲槽。遮荫处理（每头牛的遮荫面积，平方米）如下：i）有限遮荫（LS），每头牛1.2平方米遮荫面积（LS1.2）；ii）有限遮荫，每头牛2.4平方米遮荫面积（LS2.4）；iii）完全遮荫（TS），相当于每头牛9平方米；iv）完全遮荫并配备风扇（TS+F）。试验持续158天和183天。在两项研究中，每周平均最高温度均超过34°C。
增加遮荫配置有使平均日增重（ADG）呈线性增加的趋势（p = 0.08），干物质摄入量（DMI，二次效应，p = 0.03）。这种效应在LS1.2和LS2.4之间最为明显。遮荫配置本身并不影响增重效率或估计的日粮净能（NE）。与TS相比，TS+F使ADG、增重效率增加（p<0.05），并且有使日粮NE增加的趋势（p = 0.06）。遮荫对背最长肌面积和大理石花纹评分有二次效应，LS2.4的值低于LS1.2或TS（p<0.01）。同样，TS+F的大理石花纹评分低于TS。肾脏、骨盆和心脏（KPH）的比例随着遮荫增加呈线性下降。相反，TS的KPH高于TS+F。
每头牛提供超过2.4平方米的遮荫面积不会进一步提高育肥性能。风扇与遮荫结合使用可使ADG和增重效率比单独使用遮荫时更高。这些改善与DMI增加无关，而是与环境温度湿度指数对维持能量需求的改善有关。
