The relationship between meal composition and long-term diet choice1

Abstract

When animals are offered a choice of feeds that are nutritionally complementary, they are able to select a consistent combination of these feeds over long periods of time. Analysis of how such consistent diet choice is achieved, in terms of short-term feeding behavior, may further our knowledge of how animals regulate nutrient intake. Previous work, on meal pattern analysis and on nutrient synchronization, led us to hypothesize that animals may select a consistent diet within a meal. In three experiments cows were offered a choice between high- (H) and low- (L) protein feeds and short-term feeding behavior data were collected using computerized feeders. Feeding behavior was first analyzed in terms of visit characteristics. A greater average daily intake of H, relative to L, was more closely related to the ratio of H visits to L visits than to differences in the intake per visit to feeders supplying H or L. Individual meal criteria were estimated using a mixed-distribution model, and visits were clustered into meals. Cows typically had approximately six meals per day. The observed frequency distribution of meal composition, in terms of the proportion of visits to H feeders, was determined. Subsequently, the observed visits were randomly reclustered into bouts consisting of the same number of visits as were observed in meals, and the frequency distribution of random bout composition was calculated. If frequency distributions of meals and random bouts coincide, then this is evidence that cows do not regulate diet choice within a meal. Comparison of the frequency distributions of meals and random bouts provided no evidence that cows attempted to achieve their long-term average diet composition within a meal. We also investigated whether cows tried to achieve a consistent diet choice within a meal by adjusting their intake per visit, depending on the feed type visited and the proportion of visits to H feeders in a meal. There was no evidence that this occurred. In conclusion, our analyses have shown that cows did not attempt to select within a meal a consistent diet in terms of protein to energy ratio. Indeed, our data and the literature suggest that the timeframe over which the intake of energy and protein is regulated must be greater than a meal in a number of animal species.

A personal view of how ruminant animals control their intake and choice of food: minimal total discomfort

“…A similar situation is also seen in diet selection by ruminants, where large short-term fluctuations are underlain by long-term stability 56 and this leads to the conclusion that over a period of days animals regulate their intake and selection of food by a process involving correction of shortterm errors. However, neither the mechanisms nor the statistical characteristics of such phenomena have yet been resolved, providing a challenge for the future.…”

Diet selection by growing lambs offered whole barley and a protein supplement, free choice: Effects on performance and digestion

“…Also allantoin excretion data must be interpreted with caution since it is known that purine bases are not completely degraded in the rumen (Pérez et al, 1996;Vicente et al, 2004) and differences in allantoin excretion might result from variations in the extent of rumen purine degradation associated with barley processing (Askar et al, 2005). Furthermore, rumen ammonia levels may be highly variable throughout the day when ingredients that differ in their protein content are given at choice, since ruminants do not seem to select a balanced diet in the short term of a meal (Yeates et al, 2002). Therefore data recorded by spot sampling of rumen fluid did not necessarily reflect average daily levels and it is known that short term imbalances in energy and protein supply seem to have little effect on digestion or N utilisation in longer term (Ludden et al, 2002).…”

Technical note: Evaluation of bimodal distribution models to determine meal criterion in heifers fed a high-grain diet

“…Behavioral patterns associated with feeding activities provide biological insight into long-term regulation of feed intake (Forbes, 1985) diet preferences (Yeates et al, 2002), and health status of animals (González et al, 2008). Multiple technologies have been used to collect frequency and duration of feedbunk (BV) event data to examine feeding behavior in cattle (Tolkamp et al, 2000).…”