Similar feed-intake levels yield no differences in energy utilisation between beef heifers identified as low (efficient) and high (inefficient) for residual feed intake

IF 1.4 4区 农林科学 Q2 Agricultural and Biological Sciences
T. P. Vining, P. A. Lancaster, N. DiLorenzo, G. C. Lamb, J. M. B. Vendramini
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引用次数: 0

Abstract

Context

Improving cattle feed efficiency would reduce feed costs and increase herd profitability. Residual feed intake (RFI) is commonly used to rank cattle for feed efficiency, with low-RFI animals being more efficient than high-RFI animals. However, RFI classification merits further investigation because observed differences in heat energy (HE) production between low- and high-RFI cattle may be related to heat associated with differences in dry-matter intake (DMI) rather than maintenance-energy requirements.

Aims

To determine energy partitioning of beef heifers with low and high residual feed intake.

Methods

Angus crossbred heifers (n = 60) were fed a grower diet (metabolisable energy (ME) = 2.17 Mcal/kg DM) for 70 days. Feed intake was recorded daily using the GrowSafe system, and bodyweight (BW) was recorded every 14 days. Residual feed intake was calculated as the residual from the regression of DMI on mid-test BW0.75 and average daily gain (ADG) (R2 = 0.31). Low-RFI (n = 8) and high-RFI (n = 8) heifers were selected for a metabolism experiment to determine energy partitioning at three feed-intake levels, namely, ad libitum intake, and 1.0× and 0.5× expected maintenance-energy requirement. Apparent nutrient digestibility was determined using indigestible neutral detergent fibre (iNDF) as an internal marker. The sulfur hexafluoride (SF6) tracer and oxygen-pulse techniques determined methane emissions and heat production respectively. Metabolisable energy required for maintenance (MEm) and fasting heat production (HeE) were then calculated from the regression of log HP on ME intake (MEI). Efficiencies of ME used for maintenance and growth were calculated from HeE, MEm, and retained energy at ad libitum intake.

Key results

Residual feed intake was strongly correlated with DMI (0.83). Low-RFI heifers consumed 31% less (P = 0.01) feed than high-RFI heifers during the performance experiment. Heifers with low RFI had greater MEm, but similar efficiencies of ME use for maintenance and gain as did high RFI heifers.

Conclusion

These data indicated that selection based on RFI may not lead to improved energy efficiency in growing heifers.

Implications

The results of this study indicated that low-RFI cattle may not have lower maintenance-energy requirements or differences in efficiencies of ME use than do high-RFI cattle.

剩余饲料摄入量低(高效)和高(低效)的肉用小母牛之间的能量利用率没有差异
背景提高牛的饲料效率可降低饲料成本,提高牛群的盈利能力。残余采食量(RFI)通常用于对牛的饲料效率进行分级,低残余采食量的动物比高残余采食量的动物效率更高。然而,RFI 分级值得进一步研究,因为观察到的低 RFI 和高 RFI 牛的热能(HE)产生差异可能与干物质摄入量(DMI)差异产生的热量有关,而不是与维持能量需求有关。目的 确定低剩余饲料摄入量和高剩余饲料摄入量肉用小母牛的能量分配。方法给盎格鲁杂交小母牛(n = 60)饲喂生长日粮(代谢能 (ME) = 2.17 Mcal/kg DM)70 天。每天使用 GrowSafe 系统记录采食量,每 14 天记录体重 (BW)。剩余采食量是根据 DMI 对试验中期体重 0.75 和平均日增重 (ADG) 的回归计算得出的残差(R2 = 0.31)。选择低 RFI(n = 8)和高 RFI(n = 8)小母牛进行代谢实验,以确定三种采食量水平下的能量分配,即自由采食量、1.0 倍和 0.5 倍预期维持能量需要量。使用难消化中性洗涤纤维(ENDF)作为内部标记测定表观养分消化率。六氟化硫(SF6)示踪技术和氧脉冲技术分别测定了甲烷排放量和产热量。然后根据 HP 对摄入 ME 的对数回归(MEI)计算出维持所需的代谢能(MEm)和空腹产热(HeE)。根据HeE、MEm和自由采食时的留存能量计算出维持和生长所需的代谢能效率。主要结果剩余采食量与DMI密切相关(0.83)。在性能实验期间,低RFI小母牛的饲料消耗量比高RFI小母牛少31%(P = 0.01)。低RFI小母牛的MEm更大,但与高RFI小母牛相比,ME用于维持和增重的效率相似。结论这些数据表明,基于 RFI 的选择可能不会提高生长母牛的能量效率。意义本研究结果表明,与高 RFI 牛相比,低 RFI 牛的维持能量需求或 ME 使用效率可能并不低。
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来源期刊
Animal Production Science
Animal Production Science Agricultural and Biological Sciences-Food Science
CiteScore
3.00
自引率
7.10%
发文量
139
审稿时长
3-8 weeks
期刊介绍: Research papers in Animal Production Science focus on improving livestock and food production, and on the social and economic issues that influence primary producers. The journal (formerly known as Australian Journal of Experimental Agriculture) is predominantly concerned with domesticated animals (beef cattle, dairy cows, sheep, pigs, goats and poultry); however, contributions on horses and wild animals may be published where relevant. Animal Production Science is published with the endorsement of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Australian Academy of Science.
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