15AGRITECHCAT3 Evaluating a potential proxy test for Feed Conversion Efficiency in beef cattle.

该项目的目标是在英国牛肉行业通过选择饲料转化效率（FCE）来节省大量饲料成本。它将提供一种新的工具来识别饲料效率高的牛-而不需要昂贵的记录饲料摄入量和生长速度。记录成本一直是限制将FCE纳入反刍动物育种计划的主要因素。该项目还将提供有关遗传变异和相关性的初步信息，以帮助将新工具纳入育种计划。该项目的科学依据是FCE与N同位素分馏现象之间的关系。在以前的工作中，使用血液样品测量了N同位素分馏，当FCE高时，N同位素分馏较低。本项目将探索一种利用头发样品测量氮同位素分馏的新方法。毛发样本是有吸引力的，因为它们积累了很长一段时间的信息，并且很容易从农场记录其他性状的牛身上获得。从商业上讲，这既是饲养者生产更有价值的牲畜（销售公牛、精液和胚胎）的机会，也是所有牛肉生产商降低饲养成本的机会。该项目的早期阶段将收集关键信息，以便就替代工具的选择及其在育种计划中的使用方式做出决定：（i）验证基于血浆或毛发样本的替代物（Delta-15 N）与氮利用效率之间的关系。(ii)评价毛发作为测量Delta-15 N的代表性样品的适用性。(iii)代理测量值与其他农场记录性状之间关系的调查。(iv)基于替代物（Delta-15 N）的FCE遗传变异的初步分析。我们将使用在全饲料转化效率方案（60天记录采食量、活重和身体组成（通过超声扫描））的牛组（共n=100）记录期结束时采集的血浆和毛发样本作为另一项研究的一部分。将对毛发样本进行切片，以确保待分析的部分是在记录期间产生的（基底4.5 cm代表最近两个月的生长; Zazzo等人，2007）。将对血浆、毛发和饲料样本进行Delta-15 N分析，并探索Delta-15 N和FCE之间的关系，包括和不包括有关身体成分的信息。我们将（i）调查毛发15 N替代测量值与其他农场记录性状（400天体重和超声扫描）之间的关系，（ii）基于替代值对FCE的遗传变异进行初步分析，使用2，000只纯种阿伯丁安格斯动物（约100只）。100- 150群），目前正在记录通过阿伯丁安格斯牛协会（AACS）的农场记录计划。

The project targets the large feed costs savings that could be achieved by selection for feed conversion efficiency (FCE) inthe UK beef industry. It will deliver a new tool to identify feed efficient cattle - without the need for expensive recording offeed intake and growth rates. The cost of recording has been the main factor limiting the incorporation of FCE into ruminantbreeding programmes. The project will also provide preliminary information about genetic variation and correlations - tohelp with incorporation of the new tool into breeding programmes. The scientific basis for the project is the relationshipbetween FCE and the phenomenon of N isotopic fractionation. N isotopic fractionation has been measured using bloodsamples in previous work, and is low when FCE is high. This project will explore a new approach to measure N isotopicfractionation using hair samples. Hair samples are attractive because they accumulate information from an extended periodof time and are easy to obtain from cattle undergoing on-farm recording for other traits. Commercially, this is both anopportunity for breeders to produce more valuable stock (sales of bulls, semen and embryos) and for all beef producers toreduce feeding costs. The early-stage project will gather key information needed to make decisions about the choice ofproxy tool and the way that it will be used in breeding programmes:(i) Verification of the relationship between the proxy (Delta-15N) based on plasma or hair samples and N-use efficiency.(ii) Evaluation of the suitability of hair as a representative sample for measuring Delta-15N.(iii) Investigation of the relationship between proxy measurements and other farm-recorded traits.(iv) Preliminary analysis of genetic variation in FCE based on the proxy (Delta-15N).We will use samples of plasma and hair taken at the end of the recording period of groups of cattle (n=100 in total) on a fullfeed conversion efficiency protocol (60-day recording of feed intake, live-weight, and body composition (by ultrasoundscanning)) as part of another study. Hair samples will be sectioned to ensure that the portion to be analysed was producedduring the recording period (the basal 4.5 cm representing growth in the last two months; Zazzo et al. 2007). Samples ofplasma, hair and feed will be analysed for Delta-15N and relationships between Delta-15N and FCE explored, with and without inclusion of information about body composition. We will (i) investigate the relationship between the hair 15N proxymeasurement and other farm-recorded traits (400-day weights and ultrasound scans) and (ii) conduct a preliminaryanalysis of genetic variation in FCE based on the proxy, using 2,000 pedigree Aberdeen Angus animals (approx. 100-150herds) currently being recorded through the Aberdeen Angus Cattle Society (AACS) on-farm recording scheme.