Food particle size as an indicator of its structural composition and a key aspect of the development of the nutrition theory paradigm

The using of modern feed-preparation machines and new technologies for the preparation and feeding of rations in animal husbandry has exacerbated the problem of the ratio in food of relatively large particles that capable to support the necessary motility of the digestive tract and relatively small ones, which provide high consumption of dry matter and its digestibility. In the presented work, we were the first to obtain data about the relationship between the particle size of the diet, the contents of the gastrointestinal tract and the feces of cattle. Based on the determination of the average particle size and dry matter content, a method for assessing the structure of feed has been proposed. The concepts of the informational component of food and the definition of rationed feeding have been introduced into the paradigm of nutrition theory. The aim of the work was to study the impact of the particle size of the diet on the particle size of the contents of the gastrointestinal tract and feces of cattle; to assess the relationship of these indicators with the digestibility of the main groups of nutrients; to develop a methodological approach to rationing the diet structure; to supplement the theory of rationed feeding with the necessary concepts. The studies were carried out at the Institute of Animal Science of National academy of agrarian sciences of Ukraine in 2017-2019 on two heifers ( Bos taurus taurus ) of the Ukrainian red-and-white breed with a live weight of 350 kg fitted with a duodenal lockable cannula of the beginning of the duodenum and a large-diameter rumen cannula. The animals were fed twice a day (at 8 a.m. and 5 p.m.) in equal shares. Chyme flux was measured during 9 h after morning feeding. The intake of chyme into the duodenum was measured within 14 days ( n = 6). The measurements were interrupted for 1-2 days to give the animals rest. Samples of the contents of the rumen were collected through a cannula with a 100 mm diameter from the middle part of the rumen mat in triplicate with a 3 h interval between morning and evening feeding. The experiments were designed according to the balance test methodology with simultaneous assessment of the duodenal chyme flux and sampling of the rumen contents, duodenal chyme and feces. The main diet consisted of hay, silage, concentrates and provided the maintenance of the basal metabolism. The other rations were obtained by replacing one or two components of the main ration with additional amounts of the remaining components in an amount that was equal to the dry matter value of the interchangeable feed. The average particle size of the feed particles was determined by the arithmetic weighted average method by manual parsing and dry sieving, and the selected biological samples by the wet sieving method. The metabolic energy of the rations was calculated. It was found that the average particle size of rumen, chyme and feces decreased with an increase in the average particle size of the diet. The average particle size of the rumen (8.68±0.49 mm, n = 31) was an order of magnitude higher than the average particle size of the duodenal chyme and feces, that indicates the most intense crushing of feed in the proventriculus. The average particle size of feces (1.09±0.06 mm, n = 19, 0.1 > p > 0.05) exceeded the average particle size of the duodenal chyme (0.99±0.05 mm, n = 31), that is indicative of the predominant digestion of the small fraction in the intestine and the formation of feces from the large fraction of the chyme. The value of feed structure in our studies was 0.12-0.92 kgʺm/day vs. 0.033-0.062 kgʺm/day for the contents of the rumen, 0.0031-0.0057 kgʺm/day for duodenal chyme, and 0.0019-0.0028 kgʺm/day for feces. A relationship between the structure of the diet, the availability of crude protein for digestion in the intestine and the size of feces particles was revealed, that theoretically suggests the possibility of assessing the state of digestive processes which ba