A brief and comprehensive history of the development and use of feed analysis: A review

1 Introduction

In recent years, feed analysis has become an important tool in many academic disciplines other than livestock nutrition. In the field of range science, feed analysis has been used to assess the quality of forages consumed by wildlife [1]. Feed analysis is also used as a tool in crop science to assist in cultivar selection in plant-breeding programs [2]. In the environmental quality field, feed analysis is used to mitigate livestock pollution issues [3]. In toxicology, feed analysis is used to identify and quantify feed-born poisons, such as aflatoxin [4].

In contemporary agribusiness, nutritional information obtained from feed analysis is used to market feed products domestically and internationally [5]. Feed analysis is crucial in establishing quality assurance in manufactured feeds [6]. The monetary value of feedstuffs can be established through valid feed analysis [7]. Feed analysis aids in preventing detrimental or unwanted feed components from reaching consumers [8]. Accurate feed analysis performed by commercial or governmental laboratories can provide unbiased, independent, third-party verification of feed quality from which sellers and purchasers of animal feeds can negotiate transaction terms.

Recently, feed analysis has been used by various government organizations for differing reasons. Feed analysis has been used to enforce and monitor compliance to contractual terms. The United States Fish and Wildlife Service has utilized feed analysis to set contract parameters for minimum feed quality standards, as in pelleted alfalfa supplied to the National Elk Refuge for the elk feeding program in Jackson, Wyoming, USA. Several USA state wildlife agencies have also used feed analysis in ways similar to those of the National Elk Refuge. The United States Department of Agriculture Farm Service Agency has also utilized feed analysis in qualifying farmers and livestock producers for disaster relief.

As stated, feed analysis has widespread use among diverse groups. As time passes, feed analysis will continue to increase in importance for modern societies. As land and food resources become more limited, more sustainable use of resources will be required [9]. Sustainable use of feed resources can come from proper and efficient feed management. This is made possible chiefly by accurate and reliable feed analysis.

Early histories reporting origins of feed analysis are very limited. Historic accounts of the development of feed analysis are scattered; therefore, a brief chronologic compilation of significant individuals, theories, and technological advancements which have led to the development of contemporary feed analyses will be given in this review. Apart from providing background on feed analysis, in general, this review will primarily focus on the history of feed analyses that quantify fiber, lipid, and nitrogen components.

2 Early development of animal nutrition

Historically, feed analysis has developed concurrently with theoretical and technological advancements in the sciences of agriculture, nutrition, and chemistry. Over time progress in these sciences has continuously led to change in theories, methods, instrumentation, and terminology associated with feed analysis. Contemporary readers who have been educated in modern science may find it hard to understand logic and terminology from the eighteenth century or earlier. Efforts have been made in this review to provide background and explanation to fill in gaps in comprehension due to centuries of change in science and terminology.

Francois Magendie (1783–1855) described nutrition in his day as a subject resulting from conjecture, and ingenious hypothesis used to satisfy imaginations. Often knowledge of nutrition was not arrived at through sound scientific experimentation [10,11]. Incorrect ideas about nutrition often hampered progress in the science. However, through investigations in animal and plant nutrition by such scientific pioneers as Antoine François Fourcroy (1755–1809), Justus von Liebig (1803–1873), Heinich Einhof (1777–1808), Albrecht Daniel von Thaer (1752–1828), Michal Oczapowski (1788–1854), and others progress was accelerated [10,11]. Beginning with the Chemical Revolution and discovery of true elements during the late seventeenth and early eighteenth centuries, true progress and significant advancements were made in nutritional science.

During much of the eighteenth century and into the beginning of the nineteenth century, it was thought that three classes of materials existed in nature: mineral, vegetable, and animal. Animal nutrition was considered to be a process by which animals transformed vegetable matter into animal matter [12]. Dry distillation was commonly used for nearly 200 years (1615–1794) to analyze organic matter. Early on, organic matter analyzed through dry distillation was separated into weighed fractions characterized as gaseous, phlegm (watery matter), oil, or carbon residue. Later, organic matter as characterized as carbonic oxide, carbonic acid, watery fraction, empyreumatic oil, acidic fraction, carbureted hydrogen fraction, and charcoal. Even later, volatile alkalies, ammonia, and nitrogen were used by researchers to describe organic matter [13].

In 1785, Claude Berthollet found that ammonia was given off when animal tissues decomposed, establishing that animal tissues contained nitrogen. Other scientists of the period also verified that nitrogen was in animal tissues [14]. It was generally believed that nitrogen was not in plants. Constituents such as sugar, starch, or fat were thought to be unique to plants [10]. Consequently, in error, nitrogen was considered unique to animal matter. This information was erroneously used as a system to classify organic materials under two broad categories: animal and vegetable substances. Materials classified as animal substances contained nitrogen, while materials thought to have no nitrogen were regarded as vegetable substances. However, in 1789, Antoine François Fourcroy found nitrogen-containing substances in the plant family Brassicaceae [14]. Therefore, in cases where plants contained nitrogen, the plants were considered animal substance with vegetable parts [12].

Although it had been determined that nitrogen was a characteristic of animal substances, the absolute source of nitrogen was unknown, whether from an animal’s diet or from the atmosphere. In 1816, François Magendie performed simple nutritional experiments using dogs to determine if animals assimilated atmospheric nitrogen. Magendie fed dogs diets which contained carbohydrates and lipids; exclusively. After several weeks, with inadequate nitrogen in their diets, all dogs in Magendie’s experiments died. Magendie’s experiments demonstrated that animals derive nitrogen exclusively from diet and not from the atmosphere. He also discovered that animal diets can be incomplete and diets devoid of nitrogen cannot sustain life indefinitely [10].

Jean Baptiste Boussingault in 1836 through his own experimentation confirmed Magendie’s findings. Boussingault also proposed that nitrogen needed by animals could be obtained from plants. In consideration of Magendie’s work and his own, Boussingault suggested indexing and assessing plant foods based on nitrogen content. He also stated that other organic and inorganic substances may be needed for animal nutrition. However, Magendie is credited as the first to separate food nutrients into three components, namely protein, fat, and carbohydrate [14,15].

Liebig hypothesized, in 1842, that fat and carbohydrates underwent oxidation in animals [16]. He also generalized that albumen (protein) from plants is the starting point or foundation for diverse animal parts and tissues [14]. In the same year, George Budd recognized medical disorders resulting from nutrient deficiency. Although it may be asserted that through his work with scurvy in 1746 nearly a hundred years earlier, James Lind discovered the link between health and proper nutrition. However, Lind did not recognize citrus juice (vitamin C) as a deficient nutrient. Rather, at the time citrus juice was recognized as a cure or preventative for environmental conditions that led to scurvy [10]. Therefore, the link between disease and nutrition was not adequately established by Lind. Recognition of the importance of proper nutrition for optimum animal and human health stimulated a need to qualify and quantify food by more precise and accurate methods of evaluation, characteristic of chemical analysis.

3 Definition of feed analysis

Analysis was defined in 1775, “to dissolve, or break in pieces; a separation, or solution of a compound body into parts of which it consists” [17]. Analysis was later defined by Webster in 1828 as “The separation of a compound body into its constituent parts” [18]. The definition of analysis has changed little since 1775, in its primary sense, “a separation of a whole into its component parts” [19]. Taking into consideration the historic and present-day definition of analysis, feed analysis can be defined as the separation of a forage or feedstuff into its components.

4 Categories of feed analysis

There are several categories of components by which feeds are commonly analyzed: anatomical, sensorial, structural, and chemical. Anatomical components can include plant parts such as seeds, blossoms, stems, or leaves. Sensorial components comprise feed characteristics such as smell, texture, taste, and color. Structural components include feed characteristics such as particle size, chop length, leaf shatter, or fines. Chemical analyses of feeds are typically performed to establish ratios or percentages of broad chemical groups found in feeds, such as water, carbohydrates, lipids, and protein. However, currently some animal nutrition professionals emphasize that to optimize animal performance, chemical analysis of feeds should not only be carried out to quantify broad nutrient groups, but also for specific chemical compounds such as amino acids like lysine [20] and even specific sugars [21].

Feed analysis using nominal or ordinal scales is probably most common when evaluating sensory components of feeds such as smell, texture, taste, and color. Qualitative analysis, though not as precise as quantitative measures, will probably always be necessary as long as such characteristics as appearance, smell, and texture of feeds are important to livestock producers for rapid and inexpensive establishment of feed quality.

Currently, anatomical, sensory, and structural feed components can be quantified using various technologies [22]. For example in a palatability study, electronic nose analysis (ENA) was used to determine the aromatic characteristics of concentrate feeds which affect feed intake in sheep. Through ENA technology, total volatile organic compounds and sulfur compounds were quantified in feeds. Specific chemical groups such as aldehydes and terpenes were also quantified. In addition, specific compounds methanamine and α-pinene were identified and thought to contribute to negative odor or flavor in feeds studied [23]. Physical components commonly evaluated using qualitative measures can also be assessed quantitatively such as particle size [24], grain content [25], leaf or stem content [26], or stem shear force [27].

Present-day analyses of chemical feed components are almost exclusively quantified using methods which express measurements in continuous numerical values, which is the case where feed component determinations are established using gravimetric, volumetric, or spectroscopic methods.

5 Early feed analysis

6 Early feed analysis systems

7 Balancing rations

In the science of animal nutrition, several principles encourage practice of feed management: animals have nutrient requirements for maintenance, growth, reproduction [55,56], animal nutrient requirements can be satisfied through their consumption and assimilation of balanced rations [55,56], and data disclosing nutrient composition in animal feeds are needed to facilitate formulation of economically balanced animal rations [57,58].

Balancing animal diets or rations is a method used to manage animal feeding. As early as 1852, nutritional data needed for balancing livestock rations were collected by experiment stations and university laboratories in Europe and especially in Germany, using actual feeding experiments and by calculations and comparisons [59]. Later, Weende methods were used to analyze feeds used for creation of feed composition tables beginning in about 1864 [60].

From inception, reasons for balancing livestock rations were largely economic. Balanced rations provided livestock producers with greater quality and production assurances. However, successfully balanced rations are dependent on accurate feed composition data. For example, crude protein analyses which indicate nitrogen content less than that of a feeds true value would cause over supplementation of protein within a balanced ration. Curtiss [61] in 1900 noted that an effect of feeding rations too rich in nitrogenous material is that excess nutrients pass out of animals as waste, and therefore were not economical. Excess animal waste, though a primary economic concern of the late nineteenth century and much of the twentieth century in recent decades, has become a major environmental concern [62]. As important as accurate feed analysis is for formulating balanced feed rations for economic reasons, feed analysis may be more important to society for mitigation of environmental animal waste issues and for efficient and sustainable use of earth resources in the future.

8 Accuracy and precision

Although feed analysis is a field that undergoes frequent change, there are two unchanging universal objectives that guide all responsible individuals who perform feed analysis or who value feed analysis as a resource. Those objectives are accuracy and precision. Accuracy is a primary objective of feed analysis. Accuracy is used to describe how well an analytical value or measurement from a sample represents the true value from a population [63]. Precision as it pertains to feed analysis is how closely a group of measurements taken from a specific analyte agree.

In the early nineteenth century, German agricultural chemist saw a need for consistency and improvement of analytical methods. Also recognizing a need for uniformity and more satisfactory laboratory results concerned chemists and citizens in the United States organized the Association of Official Agricultural Chemists (AOAC) in 1884 [29]. Initially, the major focus of the AOAC was on the quality of analysis and methods of commercial fertilizers; but by about 1886, interest grew for uniformity of methods for analysis of animal fodders and feedstuffs. Since 1886, AOAC has successfully provided industry, government, and academia with high quality, reliable analytic methods to evaluate animal feeds, to increase precision and accuracy within and between laboratories.

Despite development of uniform analytical methods for evaluation of animal feeds, such as those authorized by AOAC, there is evidence of accuracy and precision problems among US feed laboratories. These problems have been documented in trade and professional publications [64]. Inaccurate feed analysis confounds the true objectives of end-users, harming rather than benefiting them. Unlike the past, the challenge of those who use feed analysis in the future may not be access to valid analytical methods or technology, but in achieving available, accurate, and precise measures of feed composition to support sustainable agricultural practices.

Development and utilization of certified reference material (CRM) is a step toward achieving greater accuracy and precision within and between feed laboratories. CRM serves a vital function in assessing feed laboratory performance over time [65]. CRM will become increasingly important as automated sensor-based feed evaluation technologies, for example, near infrared reflectance spectroscopy, are incorporated into such areas as precision feeding and feed quality control systems.

9 Conclusions

Feed analysis has become an integral part of the science of animal nutrition. It has become so, because feed is the major cost of modern animal production systems, and because feed analysis is vital to efficient and sustainable animal production agriculture. Reliable data on nutrient composition in feedstuffs are needed to economically balance animal rations. Consequently, feed analysis has emerged as a valuable tool for animal nutritionists, owners, caregivers, or producers. Currently, feed analysis is nearly standard practice for many animal production systems. It plays an important role in facilitating and promoting animal health, and has brought about historically unprecedented advances in livestock production and efficiency through ration balancing. However, use of feed analysis has evolved beyond being a tool for those involved with animal production or care. Feed analysis has become a valuable tool in many other scientific fields. Currently, feed analysis is widely utilized in academia, government, and industry. Feed analysis is likely to continue to evolve and have even greater positive impacts on society as environmental concerns, such as climate change or sustainable agricultural practices, become more compelling. The origins and history of feed analysis, knowledge of the people, practices, and events leading to its development are beneficial to any who seek understanding, instruction, or guidance regarding the important subject of feed composition.