Progress towards pig nutrition in the last 27 years.

Over the last 27 years (1990-2017), based on the revolutionary progresses of basic nutrition research, novel methods and techniques have been developed which bring a profound technological revolution to pig production from free-range system to intensive farming all over the world. Basic theoretical innovations and feed production studies have provided vital advancements in pig nutrition by developing formula feed, utilizing balanced diets, determining feed energy value, dividing pig physiological stages, enhancing gut health, and improving feed processing technique. Formula feed is the primary contributor of the rise of the mechanized farming industry, and meets comprehensive nutritional needs of the pig. The focuses of the development of a balanced diet by optimizing nutrient levels are the amino acids balance, the balance between amino acids and energy, the balance between calcium and phosphorus. Multiple-site-production and targeted feeding program have been applied extensively. Early weaning of piglets improves production efficiency, but piglets that have not yet fully developed their intestine are prone to diarrhea. Therefore, intestinal health has received special attention in recent years. Feed processing technologies, such as granulation, puffing, fermentation and enzymatic hydrolysis, can improve the utilization of feed nutrients and reduce production cost. However, increasing a sow's potential for production, seeking alternatives to antibiotics, reducing drug treatment in piglets, developing functional additives and improving meat quality remain future challenges. Herein, we outline the important progresses of pig nutrition in the past 27 years, which will shed light on the basic nutrition rules of pig production, and help to push forward its future development. © 2018 Society of Chemical Industry.

A 100-Year Review: From ascorbic acid to zinc-Mineral and vitamin nutrition of dairy cows.

Mineral and vitamin nutrition of dairy cows was studied before the first volume of the Journal of Dairy Science was published and is still actively researched today. The initial studies on mineral nutrition of dairy cows were simple balance experiments (although the methods available at the time for measuring minerals were anything but simple). Output of Ca and P in feces, urine, and milk was subtracted from intake of Ca and P, and if values were negative it was often assumed that cows were lacking in the particular mineral. As analytical methods improved, more minerals were found to be required by dairy cows, and blood and tissue concentrations became primary response variables. Those measures often were poorly related to cow health, leading to the use of disease prevalence and immune function as a measure of mineral adequacy. As data were generated, mineral requirements became more accurate and included more sources of variation. In addition to milk yield and body weight inputs, bioavailability coefficients of minerals from different sources are used to formulate diets that can meet the needs of the cow without excessive excretion of minerals in manure, which negatively affects the environment. Milk, or more accurately the lack of milk in human diets, was central to the discovery of vitamins, but research into vitamin nutrition of cows developed slowly. For many decades bioassays were the only available method for measuring vitamin concentrations, which greatly limited research. The history of vitamin nutrition mirrors that of mineral nutrition. Among the first experiments conducted on vitamin nutrition of cows were those examining the factors affecting vitamin concentrations of milk. This was followed by determining the amount of vitamins needed to prevent deficiency diseases, which evolved into research to determine the amount of vitamins required to promote overall good health. The majority of research was conducted on vitamins A, D, and E because these vitamins have a dietary requirement, and clinical and marginal deficiencies became common as diets for cows changed from pasture and full exposure to the sun to stored forage and limited sun exposure. As researchers learned new functions of fat-soluble vitamins, requirements generally increased over time. Diets generally contain substantial amounts of B vitamins, and rumen bacteria can synthesize large quantities of many B vitamins; hence, research on water-soluble vitamins lagged behind. We now know that supplementation of specific water-soluble vitamins can enhance cow health and increase milk production in certain situations. Additional research is needed to define specific requirements for many water-soluble vitamins. Both mineral and vitamin research is hampered by the lack of sensitive biomarkers of status, but advanced molecular techniques may provide measures that respond to altered supply of minerals and vitamins and that are related to health or productive responses of the cow. The overall importance of proper mineral and vitamin nutrition is known, but as we discover new and more diverse functions, better supplementation strategies should lead to even better cow health and higher production.

A 100-Year Review: Fat feeding of dairy cows.

Over 100 years, the Journal of Dairy Science has recorded incredible changes in the utilization of fat for dairy cattle. Fat has progressed from nothing more than a contaminant in some protein supplements to a valuable high-energy substitute for cereal grains, a valuable energy source in its own right, and a modifier of cellular metabolism that is under active investigation in the 21st century. Milestones in the use of fats for dairy cattle from 1917 to 2017 result from the combined efforts of noted scientists and industry personnel worldwide, with much of the research published in Journal of Dairy Science. We are humbled to have been asked to contribute to this historical collection of significant developments in fat research over the past 100 years. Our goal is not to detail all the work published as each development moved forward; rather, it is to point out when publication marked a significant change in thinking regarding use of fat supplements. This approach forced omission of critically important names and publications in many journals as ideas moved forward. However, we hope that a description of the major changes in fat feeding during the past 100 years will stimulate reflection on progress in fat research and encourage further perusal of details of significant events.

A 100-Year Review: Carbohydrates-Characterization, digestion, and utilization.

Our knowledge of the role of carbohydrates in dairy cattle nutrition has advanced substantially in the 100 years of the publication of the Journal of Dairy Science. In this review, we trace the history of scientific investigation and discovery from crude fiber, nitrogen-free extract, and "unidentified factors" to our present analytical schemes and understanding of ruminal and whole-animal utilization and effects of dietary carbohydrates. Historically, advances in research and new feeding standards occurred in parallel with and fostered by new methods of analysis. The 100 years of research reviewed here has bequeathed to us an impressive legacy of information, which we will continue to grow.

A 100-Year Review: Protein and amino acid nutrition in dairy cows.

Considerable progress has been made in understanding the protein and amino acid (AA) nutrition of dairy cows. The chemistry of feed crude protein (CP) appears to be well understood, as is the mechanism of ruminal protein degradation by rumen bacteria and protozoa. It has been shown that ammonia released from AA degradation in the rumen is used for bacterial protein formation and that urea can be a useful N supplement when lower protein diets are fed. It is now well documented that adequate rumen ammonia levels must be maintained for maximal synthesis of microbial protein and that a deficiency of rumen-degradable protein can decrease microbial protein synthesis, fiber digestibility, and feed intake. Rumen-synthesized microbial protein accounts for most of the CP flowing to the small intestine and is considered a high-quality protein for dairy cows because of apparent high digestibility and good AA composition. Much attention has been given to evaluating different methods to quantify ruminal protein degradation and escape and for measuring ruminal outflows of microbial protein and rumen-undegraded feed protein. The methods and accompanying results are used to determine the nutritional value of protein supplements and to develop nutritional models and evaluate their predictive ability. Lysine, methionine, and histidine have been identified most often as the most-limiting amino acids, with rumen-protected forms of lysine and methionine available for ration supplementation. Guidelines for protein feeding have evolved from simple feeding standards for dietary CP to more complex nutrition models that are designed to predict supplies and requirements for rumen ammonia and peptides and intestinally absorbable AA. The industry awaits more robust and mechanistic models for predicting supplies and requirements of rumen-available N and absorbed AA. Such models will be useful in allowing for feeding lower protein diets and increased efficiency of microbial protein synthesis.

Driving Along the Zinc Road.

After having written hundreds of research articles, reviews, and book chapters, I find it awkward to pen an autobiography. I still do use a pen. As stated by others in the nutrition field who have written of their own experiences in a perspective article for the Annual Review of Nutrition, my course through this field of science has been serendipitous. My interest in nutrition developed during my experiences with horses and then Angus cattle and entry into an animal science degree program. As the age of molecular biology was unfolding, I pursued a PhD in nutritional biochemistry with Hamilton Eaton at the University of Connecticut followed by postdoctoral work with Hector DeLuca at the University of Wisconsin, working on vitamins A and D, respectively. At Rutgers University, one of the two institutions where I have served on the faculty, I started my research program on trace elements with a focus on cadmium toxicity but soon thereafter began my research on zinc metabolism and function. I moved to the University of Florida in 1982 for an endowed position and have been a Florida Gator ever since. At the University of Florida, research expanded to include identification of zinc-responsive genes and physiological outcomes of zinc transport influencing health and disease, particularly as related to inflammation. I had the opportunity to contribute national science policy as president of both the Federation of American Societies for Experimental Biology and the American Society for Nutrition. As the time of this writing, I maintain an active laboratory.

After 65 years, research is still fun.

In 1946, at the end of World War II, I entered graduate school at Cornell University, where I remained for 44 years. During that time, my laboratory produced more than 300 publications in the field of reproductive biology, including studies on nutrition and reproduction, the role of the hypothalamus in pituitary gonadotropin release, corpus luteum formation and function, hormone assays, and estrous cycle synchronization. At age seventy, I retired from Cornell and accepted the Gordon Cain Endowed Professorship at Louisiana State University, where I continued my work on the bovine corpus luteum and added research on the collection, maturation, in vitro fertilization, and culture of bovine oocytes. In 1994, I moved to the Pennington Biomedical Research Center and soon thereafter started the research that led to development of the lytic peptide-gonadotropin conjugates, which target and destroy cancer cell membranes. I am continuing my work on the development of targeted cancer cell drugs and, yes, research is still fun!

Contributions of an animal scientist to understanding the biology of the uterus and pregnancy.

I developed a passion for reproductive biology when taking a course in Physiology of Reproduction at Louisiana State University while preparing to apply for Veterinary School at Texas A&M University. My career path changed. I entered graduate school, obtained a Ph.D. and have enjoyed an academic career conducting research in uterine biology and pregnancy in animal science departments at the University of Florida and at Texas A&M University. My contributions to science include: (1) identification of molecules secreted by or transported by uterine epithelia into the uterine lumen that are critical to successful establishment and maintenance of pregnancy, (2) discovery of steroids and proteins required for pregnancy-recognition signalling and their mechanisms of action in pigs and ruminants, (3) patterns of fetal-placental development and placental transport of nutrients, (4) identification of links between nutrients and components of histotroph that affect fetal-placental development, (5) characterising aspects of the endocrinology of pregnancy and (6) contributing to efforts to exploit the therapeutic value of interferon tau, particularly for treatment of autoimmune and inflammatory diseases. Current research focuses on select nutrients in the uterine lumen, specifically amino acids, glucose and fructose, that affect conceptus development, the therapeutic potential for interferon tau, stromal-epithelial cell signalling whereby progesterone and oestrogen act via steroid receptors in uterine stromal cells to stimulate secretion of growth factors (e.g. fibroblast growth factors and hepatocyte growth factor) that regulate uterine epithelial cells and conceptus trophectoderm, and roles of toll-like receptors expressed by uterine epithelia and conceptus trophectoderm in pregnancy.

An unexpected life in nutrition.

In this biographical article, I describe the evolution of my career in nutrition from an early period as an animal nutritionist interested in amino acid metabolism and genetic variation in nutrient requirements to an involvement in human nutrition and international public health. The career changes were in some respects a mirror of the evolution of nutritional science in my lifetime. I spent my entire career at Cornell University in what I think of as three distinct phases. As a researcher and teacher in the Poultry Science Department, I was able to do research in animal nutrition and witness the rapid industrialization of the production of poultry meat and eggs, helped by the findings of the era of nutrient discovery in nutritional science. Later I had the opportunity to lead the reorganization of human nutrition at Cornell during a period when research in nutritional science turned away from identifying new nutrients and became increasingly concerned with the roles of diet and chronic disease. During this period my research focus evolved as I became interested in aspects of international nutrition problems, particularly the influence of parasitic infections on child health and nutrition. I also became involved nationally in nutrition issues through participation in organizations such as the National Nutrition Consortium, the Food and Nutrition Board, and National Institutes of Health study sections at a time of great ferment in nutrition about the relationship of dietary patterns to health. Finally, I became provost of Cornell University and involved in the administration of a major research university. I describe my career in the context of my origins and early education springing from life on a sustainable family farm in rural Illinois.

ASAS centennial paper: Landmark discoveries in swine nutrition in the past century.

During this centennial year of the American Society of Animal Science (ASAS), it is of interest to look back over the history of our Society and, in particular, to the many contributions made by researchers in the area of swine nutrition. A great number of basic and applied research studies involving the nutrition of weanling, growing, and finishing pigs, and gestating and lactating sows have been conducted by swine nutritionists during the past 100 yr. Most of these studies were conducted at universities by animal scientists or by the graduate students under their leadership. Others were conducted by nutritionists in the feed and pharmaceutical industries and government scientists at ARS/USDA research centers. Contributions were also made by animal scientists beyond our borders. Much of the research was published in the Journal of Animal Science during its 66 yr of existence. Before the first issue of the journal was published in 1942, some of the earlier studies were reported in the Proceedings of the Annual Meeting of the Society of Animal Production, the forerunner of ASAS. These research studies have progressively led to a better understanding of the role and utilization of dietary energy, protein, AA, carbohydrates, fats, minerals, and vitamins by pigs and have helped to quantify the nutrient requirements of pigs for various stages of growth, for sows during gestation and lactation, and to a limited extent, for boars. Determining the nutritional value of a wide array of feedstuffs, evaluating feeding strategies, and assessing the value of growth-promoting and carcass-enhancing agents have been important research contributions as well. To identify the particular studies that were among the most instrumental in contributing to our present knowledge of swine nutrition is, to say the least, a daunting assignment. To aid in this task, a survey of swine nutritionists was conducted in which they were asked to identify and rank the 10 most significant findings in swine nutrition during the past 100 yr. The results of that survey are presented in this paper.

Contribution of research with farm animals to protein metabolism concepts: a historical perspective.

The roles of proteins, carbohydrates, fats, and micronutrients in animal and human nutrition were broadly described during the late 18th and 19th centuries, and knowledge in protein nutrition evolved from work with all species. Although much of the fundamental and theoretical research in protein metabolism during the 20th century was conducted with laboratory animals, basic protein nutrition research in farm animals complemented those efforts and led to the development and use of new investigative methods (particularly in amino acid nutrition) as well as use of animal models in furthering the understanding of human protein metabolism. All these efforts have led to a contemporary hybrid model of protein nutrition and metabolism applicable to both humans and animal species. Now in the 21st century, farm animals are used in fetal and pediatric nutrition research, and data accruing for excess amino acid feeding in research with farm animals provide direction for assessment of pharmacological effects of amino acids when consumed in excessive quantities. Thus, as nutritional science is moving forward into nutrigenomics, nutriproteomics, and metabolomics, farm animal and human nutrition research interactions will likely continue with genetically modified farm animals produced for agricultural reasons (improved function and product quality) or those produced with human genes introduced to generate even better models of human protein metabolism.