The effect of silage fermentation characteristics on dry-matter intake of steers

Effect of feeding supplements on the intake and live-weight gain of male red deer given silage during winter

The live-weight gain (LWG) of young male red deer in New Zealand naturally slows during winter and feeding diets of mainly silage appears to exacerbate this effect. We aimed to quantify the effect of feeding silage on intake and LWG during winter and the ability to improve LWG by feeding supplements, mainly in the form of barley. Seven groups of eight deer were maintained outside in gravelled enclosures and offered silage ad libitum for 94 days during winter. Six groups were given supplements (950 g barley with 50 g rapeseed meal per kg to make all diets isonitrogenous) at rates of proportionately 0·2, 0·4, 0·5, 0·6, 0·7 and 0·9 of the metabolizable energy (ME) intake of the group given only silage (0). The study also examined the effect of the winter treatments on subsequent LWG to slaughter weight whilst grazing on pasture during spring and into summer (102 days).

Increasing supplement intake resulted in a decrease in silage dry matter (DM) and ME intake (P < 0·001) and an increase in total ME intake (P < 0·01). The substitution rate for silage DM was 0·84 (s.e. 0·079). LWG during silage feeding was positively related (P < 0·01) to supplement intake with an increase of 6·21 g/day per MJ per day. LWG on pasture was not related to either supplement feeding rate or LWG during winter. LWG over the entire experiment was related (P < 0·01) to supplement feeding rate, with a final difference in live weight of 6 kg between 0 and 0·9 groups.

This study has confirmed that the LWG of young male deer is low during winter when given only silage and that feeding supplements increases total ME intake and LWG. The reduced LWG due to silage feeding was not compensated for on pasture during spring and summer, thus delaying the time to reach slaughter weight by approximately 1 month. High proportions of silage in the diet appear unsuitable for young male deer if the aim is to achieve rapid LWG during winter.

Meal patterns of dairy cows consuming mixed foods with a high or a low ratio of concentrate to grass silage

With the aim of testing the effects of food quality on meal patterns 127 213 visits by 22 lactating cows to 12 computerized feeders supplying two foods, high forage (HF) and high concentrate (HC) consisting of grass silage and concentrate were analysed. The foods were composed of the same ingredients but the proportion of concentrate dry matter (DM) in the food DM differed between HC (0·59) and HF (0·27). Each of the foods was offered ad libitum to 11 cows from the start of lactation until 156 (s.e. 9) days after calving. Mean daily fresh food intake (49·2 kg) was not affected by treatment. Mean daily intake of DM differed between HC (23·6 kg) and HF (17·8 kg). After estimating individual meal criteria, visits were grouped into meals. The mean daily number of meals was 6·6, the mean fresh food intake per meal was 7·6 kg and neither was affected by treatment. Cows consuming HF had longer meals (41·4 v. 31·3 min) but a lower feeding rate than cows consuming HC (233 v. 337 g of fresh food per min and 78 v. 156 g DM per min). Pre- and post-prandial correlation coefficients were sometimes statistically significant but always low (R2from 0 to 0·05) and not affected by treatment. Food intake per hour of the feeding cycle (defined as the intake during a meal divided by length of the meal plus the duration of the preceding between-meal interval) showed a diurnal pattern in the shape of a sine-wave with low values of about 1·5 kg/h for cycles starting just after midnight and high values of more than 3·0 kg/h for cycles starting just after noon. Neither the mean, nor the amplitude, nor the shift of the sine-wave were affected by treatment. The data suggest that similar mechanisms are responsible for the short-term intake regulation of HC and HF. No evidence was found to suggest that the diurnal meal pattern of cows consuming HF deviated from that of cows consuming HC as a result of differences between foods in constraints related to their physical properties.

A comparison of five methods that estimate meal criteria for cattle

In 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.

The temporal structure of feeding behavior

Meals have long been considered relevant units of feeding behavior. Large data sets of feeding behavior of cattle, pigs, chickens, ducks, turkeys, dolphins, and rats were analyzed with the aims of 1) describing the temporal structure of feeding behavior and 2) developing appropriate methods for estimating meal criteria. Longer (between-meal) intervals were never distributed as the negative exponential assumed by traditional methods, such as log-survivorship analysis, but as a skewed Gaussian, which can be (almost) normalized by log-transformation of interval lengths. Log-transformation can also normalize frequency distributions of within-meal intervals. Meal criteria, i.e., the longest interval considered to occur within meals, can be estimated after fitting models consisting of Gaussian functions alone or of one Weibull and one or more Gaussian functions to the distribution of log-transformed interval lengths. Nonuniform data sets may require disaggregation before this can be achieved. Observations from all species were in conflict with assumptions of random behavior that underlie traditional methods for criteria estimation. Instead, the observed structure of feeding behavior is consistent with 1) a decrease in satiety associated with an increase in the probability of animals starting a meal with time since the last meal and 2) an increase in satiation associated with an increase in the probability of animals ending a meal with the amount of food already consumed. The novel methodology proposed here will avoid biased conclusions from analyses of feeding behavior associated with previous methods and, as demonstrated, can be applied across a range of species to address questions relevant to the control of food intake.

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+/-2.1 min), and visits were grouped into meals. Meal duration (36.9+/-1.3 min) 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.