Meal Criteria Research Articles

The Biologically Relevant Unit for the Analysis of Short-Term Feeding Behavior of Dairy Cows

To determine whether visits or meals are the most biologically relevant unit of short-term feeding behavior, we analyzed 209,025 records of visits to feeders by 37 cows. Two feeds were used that differed in protein content. Cows were divided into control groups for the low and high protein feeds and a choice group that had access to both. Daily number of visits and intake per visit were very variable. Cows fed low protein feed had lowest daily intakes, but single-visit characteristics were poorly correlated with daily intake. The probability of cows ending a visit did not change greatly with visit length. Log-normal models were used to estimate individual meal criteria (44.7±2.1min), and visits were grouped into meals. Meal duration (36.9±1.3min) and daily number of meals (6.1±0.1) were not affected by treatment. Feeding rate and intake per meal were lowest for cows fed low protein feed. Meal size decreased systematically during the day. The probability of cows ending and starting a meal increased with meal length and interval between meals, as predicted by the satiety concept. Meals are, therefore, a biologically relevant unit of short-term feeding behavior and visits are not.

The biologically relevant unit for the analysis of short-term feeding behaviour of dairy cows

Study of short-term feeding behaviour (STFB) could improve the understanding of variation in daily intake in dairy cows. STFB is generally measured in short bouts (e.g. visits to feeders) that are clustered in larger bouts (or meals). The value of bout analysis depends strongly on the choice of an appropriate bout. Before bouts can be grouped into meals, a meal criterion (MC, that is: the longest non-feeding interval accepted as part of a meal) must be estimated. Tolkamp and Kyriazakis (1999) criticised existing methods and recently developed a new technique to estimate meal criteria. These log-normal models were developed on basis of the idea that eating bouts end when animals are satiated (i.e., in a state of low feeding motivation) (Tolkamp and Kyriazakis, 1999). This implies that feed consumption during the relevant eating bout will result in a gradual increase in satiety. This will be associated with an increase in the probability of cows ending a bout. In this study we will analyse whether meals are a more biologically relevant unit of STFB than the short feeding bouts (i.e. visits) that are routinely recorded.

A comparison of five methods that estimate meal criteria for cattle

AbstractIn data collected for feeding behaviour analysis, feeding events are generally separated by many very short to very long intervals during which no feeding occurs. When feeding is clustered in bouts, a meal criterion (that is the longest non-feeding interval accepted as part of a meal) must be estimated before events can be grouped into meals. Until recently, three methods that estimate quantitative meal criteria were available. These methods consist of fitting a ‘broken-stick’ (two straight intersecting lines, both with a negative slope) to the frequency distribution (method 1), the loge-transformed cumulative frequency distribution (the log-survivorship curve; method 2) or the loge-transformed frequency distribution (method 3) of intervals between events. Recently, new methods have been proposed that fit either two (method 4) or three (method 5) Gaussians to the frequency distribution of loge-transformed interval length (log-normal models). We compare the estimates obtained with these five methods when applied to a data set of 79575 intervals between visits to food dispensers. These were recorded with 16 lactating cows during an average period of 156·6 (s.d. 51·5) days per cow. Meal criteria were estimated as 1·9, 6·0, 7·5, 32·4 and 49·1 min by methods 1 to 5, respectively. Estimated daily number of meals ranged from 5·7 to 12·1 per cow and estimated average meal size from 4·0 to 8·4 kg. The observed probabilities of cows initiating feeding in relation to time since feeding last showed best agreement with the predictions of the log-normal models. We conclude that the first three methods do not, while log-normal models do, have an adequate biological basis for a clear interpretation of the estimated meal criteria. Log-normal models are, therefore, the most promising for estimating meal criteria in cattle and probably in other species as well.

To split behaviour into bouts, log-transform the intervals

Analysis of behaviour that is displayed in bouts depends crucially on quantitative estimates of bout criteria, that is, the lengths of the shortest intervals between bouts. Current methods estimate bout criteria by modelling the log-transformed (cumulative) frequency distributions of intervals between events. For analysis of feeding behaviour, these models will not result in biologically meaningful quantitative estimates (Tolkamp et al.1998,Journal of Theoretical Biology194, 235–250). We proposed a method that models the frequency distribution of log-transformed interval lengths instead. Applying this method to a single data set showed that the log-transformed lengths of intervals between feeding events were distributed as two Gaussians. Here we test this model using a data set of 35171 intervals between feeding that was obtained during an experiment with 38 cows in three dietary treatment groups. No meaningful bout criterion could be obtained for some individuals, which casts doubt on the general validity of the proposed model. Addition of a third log-normal improved the fit of the model and we hypothesized that this third population represents intervals including drinking. In a second experiment, we found the measurements to be consistent with this hypothesis. We obtained meaningful meal criteria for all individuals by fitting either a double, or a triple, log-normal model to the frequency distributions of the lengths of intervals between feeding. These log-normal models appear to be not only more biologically meaningful than log (cumulative) frequency models but also far more flexible.

Estimating meal criteria for meal pattern analysis of dairy cows

Meal pattern analyses depend crucially on appropriate estimates of bout or meal criteria (i.e., the longest non-feeding intervals accepted as part of a meal). Bout criteria are frequently estimated after fitting a ‘broken-stick’ to the un-transformed, the log-transformed, or the log-transformed cumulative (log-survivorship), frequency distribution of between-feeding interval length. We know of no biological justification for fitting a broken stick to the frequency distribution of short intervals between feeding events and can, therefore, not interpret ‘criteria’ obtained that way. The methods that fit a broken-stick to log-survivorship or log-frequency curves are based on the implicit assumption that the probability of an animal initiating a bout is independent of the time since the last bout. Only then will the length of intervals between bouts be distributed as a negative exponential that appears as a straight line after log-transformation. However, the satiety concept predicts that this probability is not constant but increases with time since the last meal.

Satiety Splits Feeding Behaviour into Bouts

Animal behaviour is frequently displayed in bouts. Bout analysis aims at finding a bout criterion, i.e. that time between events that separates intervals within, from intervals between, bouts. Methods used for quantitative bout analysis are log-supervivorship and log-frequency analysis. Both models assume that the probability of the start of an event (or a bout) is independent of the time since the last event (or bout) and that, therefore, events as well as bouts occur according to Poisson processes, i.e. purely at random. The frequencies of intervals within, as well as between, bouts are then distributed as negative exponentials. These models are also widely applied in feeding behaviour analysis, where bouts can be meals. However, the satiety concept predicts that after terminating a meal, the animal's feeding motivation will be low. The probability of the animal initiating the next meal is expected to increase with time since the last meal and, therefore, meals will not likely be randomly distributed. A negative exponential is then not the most appropriate model to describe the frequency distribution of intervals between meals. Results of an experiment in which feeding behaviour of 16 cows was recorded continuously for 30 days were used to test the suitability of existing bout analysis techniques. It is concluded that these techniques are inadequate for the description of the observed interval distributions. A new model is proposed that takes account of the observed “shortage” of short intervals between meals. In contrast to existing models, that describe log-transformed frequency distributions of interval lengths, the proposed model describes frequency distributions of log-transformed interval lengths. Compared with existing models, this log-normal model is in better agreement with the biological phenomenon of satiety, it gave a better fit to the observed interval distribution and led to a more meaningful meal criterion.

Effects of Concentrate Intake on Subsequent Roughage Intake and Eating Behavior of Cows in an Automatic Milking System

Twenty-three cows were kept in a free-stall barn with an automatic system for milking and feeding. The cows were offered mixed silage for ad libitum consumption. Concentrates were fed with the automatic milking system. This experiment examined the eating behavior of cows and the relationship between the intake of concentrate and the subsequent intake of roughage in a free-stall barn with an automatic milking system. An individual meal criterion was used to characterize the meal pattern of each cow. Daily roughage intake and the time spent on meals ranged from 25.6 to 40.2 kg/d and from 70.1 to 240.0 min/d, respectively. Meal duration and size did not differ, regardless of whether concentrate was eaten or not eaten during the premeal interval. Multiple regression analysis showed that the partial regression coefficient for the duration of the premeal interval was significant for each cow, and the regression coefficient for the intake of concentrate during the premeal interval was significant for 78% of the cows. Separation of the eating phases into concentrate and roughage showed that the cows made many repeated traffic cycles through the automatic milking system and feeding section of the barn, thus revealing a high demand for concentrate under the experimental conditions.

Patterns of daily food intake in growing pigs

AbstractFood intake patterns of growing pigs given food ad libitum in individual and group housing were derived from food intake recordings with IVOG®-stations. The IVOG-station is a feeding station that records animal identification number, time, duration and amount of food intake during each visit of a pig to the food hopper. Data were collected in three testing batches of 90 Dutch Landrace pigs each, housed in 10 individual pens and in 10 group pens of eight pigs per batch.Based on survival analysis theory, intervals between visits shorter than 5 min (which was used as meal criterion) were regarded as within-meal intervals and these visits were grouped into meals. In group housing, food intake per day and rate of food intake had no significantly non-normal distribution. In individual housing, rate of food intake, food intake per day and number of meals per day had no significantly non-normal distribution. In individual housing rate of food intake, food intake per day and number of meals per day had no significantly non-normal distribution. All traits were normally distributed after discarding extreme values, except food intake and eating time per visit and per meal. In group housing these traits were not significantly non-normally distributed after logarithmic transformation.Pigs housed in groups ate faster, had a higher food intake per meal but less meals per day, less eating time per day and a lower daily food intake than pigs penned individually. During the day two peaks of feeding activity occurred, especially in group housing: one in the morning and one in the beginning of the afternoon.A distinction was made between meals with a major contribution to daily food intake and meals of minor importance. In group housing, 69% of the daily number of meals accounted for proportionately 0·87 of daily food intake and 0·83 of daily food intake time. In individual housing 39% of the meals accounted for proportionately 0·90 of the daily food intake and 0·79 of the daily eating time.Higher repeatabilities of day to day recordings of food intake traits, were found when estimated within 2-week periods compared with months or with the total fattening period.

Sucking behaviour of dairy calves fed milk ad libitum by bucket or teat

The milk intake and sucking behaviour of Dutch and Holstein-Friesian crossbred calves fed milk replacer ad libitum by either the bucket method ( n=8) or an artificial teat ( n=6) were compared. The animals were observed for 3 weeks from the age of 2 weeks, penned individually and all provided with a “dummy” (artificial) teat near the milk source within the pen. The teat-fed calves ingested significantly more milk than the bucket-fed calves (11.9 vs. 8.0 kg/day; P<0.05), and this intake took much longer (44.2 vs. 17.7 min/day; P<0.05). In both treatment groups, milk intake was organized in “meals”. The meal criterion, separating the withinmeal and between-meal non-feeding intervals, was set at 5 min. Frequency of meals and daily total meal duration did not differ significantly. Meals occurred rather randomly throughout a 24-h period. On average, the dummy teat was used for 13 min per day by bucket-fed calves, but for only 1 min by teat-fed calves ( P<0.05). Sucking of the dummy teat was largely clustered within the meal periods. It is concluded that in the young calf a need for sucking exists independently of milk satiation. However, the level of satiation depends on whether the calf drinks or sucks the milk. Nutritive sucking is clearly more reinforcing than non-nutritive sucking.