Abstract:
Studying animal nutrition and physiology is important not only for monitoring animal health and productivity, but also for product quality control and human health. This review will discuss the advantages and disadvantages of various methods for studying animal nutrition. In general, these methods are divided into «field» (observation, stomach/feces analysis) and «laboratory» (biochemical, molecular, balance). They allow one to determine the diet, energy requirements, and evaluate feed quality. The main methods for studying nutrition: Analysis of stomach and feces contents: a classic field method that allows one to accurately determine the composition of food. Biochemical methods: analysis of the profile of proteins and amino acids, lipids and fatty acids, carbohydrates, and other markers. Molecular methods: analysis of DNA samples to identify food items. Balance method: determination of nutrient requirements based on the balance of nitrogen and carbon. Observational method: direct observation of animal behavior (including feed preference tests).
Feed nutritional assessment: determination of energy, protein, and amino acids in the diet. Recently, there has been growing interest in studying the digestion process to understand the potential impact of food on human health. Ideally, digestion should be studied in humans under natural conditions, but this is not always feasible from an ethical and financial standpoint. Therefore, as an alternative to in vivo experiments, simple in vitro digestion models simulating the gastrointestinal tract have been proposed. However, such models do not fully capture the complexity of the digestive tract. Therefore, chronic digestion experiments are a powerful tool for studying digestion in animals, allowing the dynamics of physiological processes to be monitored in real time, as demonstrated in studies on farm animals (broiler chickens, pigs, cows, etc.).
During animal digestion studies, chyme samples are collected from the gastrointestinal tract, which can only be done without slaughter using cannulation. Fistula («cannula») placement involves surgically inserting a cannula into the wall of the gastrointestinal tract. The outer end of the cannula extends beyond the skin and contains a removable stopper that allows for sample extraction. The advantage of cannulation is that it allows for sampling from the same animal over a long period of time. Furthermore, the same animals can be given different experimental treatments, reducing variability. However, cannulation requires surgical intervention, and surgical modifications can alter gastrointestinal secretions and motility, altering blood flow patterns and modifying the digestive process itself. Using cannulated animals provides unique data on the kinetics of enzymatic digestion, intestinal motility, and microbial fermentation, which is unavailable with static methods such as postmortem analysis.
The study was supported by the Russian Science Foundation grant No. 25-16-00095, https://rscf.ru/project/25-16-00095/.
