Feeding Visits Research Articles

Weaning age of calves fed a high milk allowance by automated feeders: Effects on feed, water, and energy intake, behavioral signs of hunger, and weight gains

Dairy calves are increasingly fed large volumes of milk, which reduces feeding motivation and improves weight gain. However, calves often show signs of hunger and lose weight when weaned off milk due to low starter intake. We examined whether delaying the age at weaning would reduce responses to weaning. Calves were raised in groups of 9 and fed milk, starter, hay, and water with automated feeders. In each group, 3 calves were randomly assigned to 1 of 3 treatments: (1) low-milk, early-weaned: fed 6 L/d of milk and weaned at 47 d of age; (2) high-milk early-weaned: fed 12 L/d of milk and weaned at 47 d; (3) high-milk later-weaned: fed 12 L/d of milk and weaned at 89 d of age. Milk, starter, and hay intakes were recorded daily and digestible energy (DE) intake estimated. Feeder visits were recorded. Before weaning, the high-milk calves drank more milk, ate less starter and hay, but had higher DE intakes, gained more weight, and made fewer visits to the milk feeder than the low-milk, early-weaned calves. During and immediately after weaning, the high-fed, early-weaned calves ate less starter and hay, had lower DE intakes, and gained less weight than the low-milk, early-weaned calves and lost their body weight advantage 7 d after weaning. During and immediately after weaning, the high-milk, later-weaned calves ate more starter and hay and had higher DE intakes, higher weight gains, and made fewer visits to the milk feeder than the high-milk, early-weaned calves. They were still heavier than the low-milk, early-weaned calves 18 d after weaning. Delaying the age at which calves are weaned off milk reduces the drop in energy intake and behavioral signs of hunger that result from weaning.

Hummingbirds choose not to rely on good taste: information use during foraging

To increase their chances of survival and reproduction, animals must detect changes in food quality and then decide if, and how quickly, to adjust their behavior. How quickly an animal responds to change will depend on the information available (cognitive, sensory, or physiological) and how it weights those types of information. Surrogate measures of meal size suggest that sensory information is used to make initial choices about how much to eat following changes in resource quality, choices are subsequently altered and refined as further information becomes available. Using direct measures, we investigated the amount of food consumed, the time taken to feed, and the interbout intervals between visits to a feeder of rufous hummingbirds, before and after changes in sucrose concentration. The hummingbirds did not change how much they drank at first experience of a new concentration but then rapidly adjusted meal sizes toward optimal for that concentration over a few feeding visits. Thus, it seems the hummingbirds used both cognitive and physiological information to decide how much to drink but appeared to ignore sensory information, such as taste. The early responses animals make to changed resources enable us to determine the types of information on which they rely most in their decision making. Copyright 2011, Oxford University Press.

Experimental cooling during incubation leads to reduced innate immunity and body condition in nestling tree swallows

Nest microclimate can have strong effects that can carry over to later life-history stages. We experimentally cooled the nests of tree swallows (Tachycineta bicolor). Females incubating in cooled nests reduced incubation time and allowed egg temperatures to drop, leading to extended incubation periods. We partially cross-fostered nestlings to test carry-over effects of cooling during incubation on nestling innate constitutive immunity, assessed through bacteria killing ability (BKA) of blood. Nestlings that had been cooled as eggs showed a lower ability to kill bacteria than control nestlings, regardless of the treatment of their foster mother. However, there was no effect of treatment of rearing females on nestling BKA in control nestlings, even though cooled females made significantly fewer feeding visits than did control females. This suggests that the effect of cooling occurred during incubation and was not due to carry-over effects on nestling condition. Nestlings that were exposed to experimental cooling as embryos had lower residual body mass and absolute body mass at all four ages measured. Our results indicate that environmental conditions and trade-offs experienced during one stage of development can have important carry-over effects on later life-history stages.

Group provisioning limits sharing conflict among nestlings in joint-nesting Taiwan yuhinas

Offspring often compete over limited available resources. Such sibling competition may be detrimental to parents both because it entails wasted expenditure and because it allows stronger offspring to obtain a disproportionate share of resources. We studied nestling conflict over food and its resolution in a joint-nesting species of bird, the Taiwan yuhina (Yuhina brunneiceps). We show that adult yuhinas coordinate their feeding visits, and that this coordination limits competition among nestlings, leading to a 'fairer' division of resources. Transponder identification and video-recording systems were used to observe adult feeding and nestling begging behaviours. We found that: (i) yuhinas feed nestlings more often in large parties than in small parties; (ii) feeding events occurred non-randomly in bouts of very short intervals; and (iii) food distribution among nestlings was more evenly distributed, and fewer nestlings begged, during large-party feeding bouts compared with small-party feeding bouts. To our knowledge, this is the first study in a cooperative breeding species showing that adults can influence food allocation and competition among nestlings by coordinating their feeding visits. Our results confirm the hypothesis that the monopolizability of food affects the intensity of sibling competition, and highlight the importance of understanding the temporal strategies of food delivery.

Synchronous provisioning increases brood survival in cooperatively breeding pied babblers

1. Behavioural synchrony typically involves trade-offs. In the context of foraging, for example, synchrony may be suboptimal when individuals have different energy requirements but yield net benefits in terms of increased foraging success or decreased predation risk. 2. Behavioural synchrony may also be advantageous when individuals collaborate to achieve a common goal, such as raising young. For example, in several bird species, provisioners synchronize nest-feeding visits. However, despite the apparent prevalence of provisioning synchrony, it is not known whether it is adaptive or what its function might be. 3. Here, we propose a novel explanation for provisioning synchrony: it increases brood survival by decreasing the number of temporally separate nest visits and accordingly the chance that the nest will be detected by predators. Using cooperatively breeding pied babblers, we showed experimentally that provisioners synchronized nest visits by waiting for another provisioner before returning to the nest. Brood survival increased with provisioning synchrony. Provisioners were more likely to synchronize feeding visits for older nestlings as they were louder and possibly more conspicuous to predators. Finally, provisioners in large groups were more likely to wait for other provisioners and synchronized a higher proportion of all visits than those in smaller groups. Thus, provisioning synchrony may be one mechanism by which large groups increase brood survival in this species. 4. This study highlights a novel strategy that birds use to increase the survival of young and demonstrates the advantages of coordinated behaviour in social species.

Intermittent suckling affects feeder visiting behaviour in litters with low feed intake

Intermittent suckling (IS) has proven to stimulate creep feed intake in suckling piglets. This paper describes the development of feeding behaviour in three litters with high (H) and three litters with low (L) feed intake during lactation in both control (C) and IS treatment. In order to synchronize the start of intermittent suckling within a farrowing room, treatment day 0 (T0) was designated as the start of data collection. IS litters were separated from the sow for a period of 12 h/day (0930 to 2130) from T14 to weaning (T25). Feeder visits of individual piglets and nursing behaviour were analysed from continuous video recordings at 5 treatment days: T13, T16, T24, T25 and T26. A high number of CL piglets never visited the feeder during lactation; at T24, 56% of the CL piglets did not visit the feeder. On the other hand, 91% of the ISL and CH piglets and all ISH piglets visited the feeder at least once at T24. In contrast to the other groups, no increase was seen in visiting frequency during lactation in CL piglets. At T24, visiting frequency was higher in ISL than in CL piglets. So, IS stimulated piglets from low feed intake litters to visit the feeder. Between T16 and T24, total feeder time increased in piglets from all groups ( P < 0.05), except in CL piglets in which no change was found ( P > 0.10). Latency to first visit to the feeder after weaning did not differ between groups. It is concluded that IS stimulates piglets from litters with a low level of creep feed intake to visit the feeder during lactation, which familiarizes them with the feeder and the feed during lactation. The IS treatment does not affect feeder visiting behaviour of piglets with an anyhow high level of feed intake during lactation.

Invited review: Feeding behavior of goats1,2

Factors influencing the feeding behavior of goats include grazing management practices, type of vegetation and season, breed and stage of production, group size, and properties of diets fed in confinement. Considerable information has been gathered from visual observation during daylight. However, tools are now available to characterize the feeding behavior of goats while grazing and while in confinement throughout the day. Global positioning system collars can be used to assess horizontal and vertical distances traveled, up or down position of the head, and movement within pasture or rangeland areas. A commercially available leg activity monitor allows estimation of the number of steps and time spent standing, lying, and moving rapidly without grazing. However, these measurements do not directly determine grazing. Therefore, prediction equations based on visual observation must be developed. Classification tree analysis is a robust method in developing these equations because the decision tree can be pruned or expanded to provide the best fit. Another equipment system determines time spent eating, ruminating, and remaining idle from the pattern of jaw movement. In addition to use of n-alkanes as internal markers to estimate digestibility, their profile can provide an indication of the botanical composition of the selected diet. Automated feeding systems for confined goats permit determinations such as number of feeder visits and meals, eating time, and rate and pattern of feed intake. Heart rate measured while goats are in normal production settings can be used to predict total energy expenditure through multiplication by energy expenditure per heartbeat of individual animals. To partition the activity energy cost, an estimate of ME intake or measures of changes in body energy status and milk energy yield are needed to determine other sources of heat to be subtracted from total energy expenditure. These methods create the opportunity to gain a fuller understanding of factors influencing the feeding behavior of goats and the relationships with levels and efficiencies of production.

Parent-absent begging in the Brown-headed Cowbird (Molothrus ater): the role of short-term need and nestmate size

Although it is well-established that nestlings of many altricial species beg when parents are away from the nest, we have a poor understanding of parent-absent begging in brood parasites, including the proximate factors that may influence begging frequency and intensity. In this study, I examined how parent-absent begging was influenced by competitive asymmetries between host and Brown-headed Cowbird (Molothrus ater) nestlings under disparate levels of short-term need. Food-deprived cowbird nestlings begged more frequently and for a greater proportion of parent-absent period than when food-supplemented, with similar patterns observed in hosts of different sizes. In contrast, three metrics of cowbird begging intensity varied relative to host size but not due to differences in short-term need. Cowbirds consistently begged more frequently and intensively than host nestlings for a given level of short-term need, providing evidence that cowbird begging displays are more frequent and intense than non-parasitic nestlings during both feeding visits and parent-absent periods. In sum, the frequency of begging by cowbirds was only influenced by short-term need, whereas begging intensity during parent-absent events was only influenced by the host against which cowbirds competed. This study demonstrates that host size and short-term need had differing influences on the frequency and intensity of parent-absent begging in cowbirds, although both factors are likely important in limiting the evolution of parent-absent begging in cowbirds. Because it appears to provide no immediate benefits yet may decrease fitness, parent-absent begging should be included in future theoretical models investigating the evolution of begging displays in nestling birds.

Vocal sib–sib interactions: how siblings adjust signalling level to each other

Game theory states that iterative interactions between individuals are necessary to adjust behaviour optimally to one another. Although our understanding of the role of begging signals in the resolution of parent–offspring conflict over parental investment rests on game theory implying repeated interactions between family members, empiricists usually consider interactions at the exact moment when parents allocate food among the brood. Therefore, the mechanisms by which siblings adjust signalling level to one another remain unclear. We tackled this issue in the barn owl, Tyto alba. In the absence of parents, hungry nestlings signal vocally to siblings their intention to contest vigorously the next, indivisible, food item. Such behaviour deters siblings from competing and begging when parents return to the nest. In experimental two-chick broods, nestlings producing the longest calls in the absence of parents, a signal of hunger level, were more successful at monopolizing the food item at the first parental feeding visit of the night. Moreover, nestlings increased (versus decreased) call duration when their sibling produced longer (versus shorter) calls, and an individual was more likely to call again if its sibling began to vocalize before or just after it had ended its previous call. These results are in agreement with the hypothesis that siblings challenge each other vocally to reinforce the honesty of sib–sib communication and to resolve conflicts over which individual will have priority of access to the next delivered food item. Siblings challenge each other vocally to confirm that the level of signalling accurately reflects motivation.

Feeding visit time of fruit-eating birds in Cerrado plants: revisiting the predation risk model

Fruiting plants that attract frequent visits by fruit-eating birds tend to be predictable patches for a predator. Consequently, the risk of a predator attack increases the longer a bird stays on a fruiting plant. We tested whether large and cryptic species of fruit-eating birds spend more time per feeding visit than smaller and conspicuous ones in fruiting plants of the Brazilian Cerrado. Data were obtained from the literature for eight fruiting plant species and from field observations of birds feeding on fruits of Zanthoxylum rhoifolium (Rutaceae). We searched for a positive linear relationship between the mean visit time and the total length of the species, considering bird color as a covariate. Feeding visits of the large and cryptic bird species lasted longer than feeding visits of small and conspicuous species. Large birds may be safer from predators because large predators are less common. Cryptic birds may be difficult to be detected by predators and, consequently, may be less likely to be attacked by predators than conspicuous birds. Thus, our results provide support to the hypothesis that vulnerable bird species spend less time foraging in fruiting plants.

Who Cares? Males Provide Most Parental Care in a Monogamous Nesting Cuckoo

AbstractCuckoos hold a prominent position in the study of parental care, because they show the greatest variation of any bird family in the way they care for their offspring. Despite this, few data are available on cuckoos with biparental care even though it is the most common form of parental care in cuckoos and birds in general. Here I describe the breeding behaviour of the pheasant coucal,Centropus phasianinus, an old‐world nesting cuckoo. I show that males almost exclusively build the nest and incubate and brood the young alone both at night and during the day. The incubation pattern of short,c. 40 min bouts on the nest interspersed with 20 min frequent recesses is well suited to incubation by a single parent and is widespread amongst birds. Males also defend the nestlings and deliver 80% of the feeds to the young consisting of insects (65%), frogs and reptiles. Females did not compensate for their fewer feeding visits by delivering more vertebrates than males. Although coucal males get little help feeding, the hourly feeding rate of 3.8 feeds per brood (1.4 feeds/nestling) exceed that of the few nesting cuckoos studied to date and matches that of other tropical non‐passerines. Predominantly male care is found in less than 5% of birds, mainly species with reversed sexual size dimorphism or reversed sex‐roles. Its evolution, especially in monogamous species, remains puzzling. The breeding behaviour of pheasant coucals illustrates a possible transitional stage in the evolution of polyandry and interspecific brood parasitism in cuckoos.

Changes in Feeding Behavior as Possible Indicators for the Automatic Monitoring of Health Disorders in Dairy Cows

Changes in short-term feeding behavior of dairy cows that occur with the onset of the health disorders ketosis, acute locomotory problems, and chronic lameness were investigated using data collected during previous experiments. The objective of the study was to describe and quantify those changes and to test their suitability as early indicators of disease. Feed intake, feeding time, and number of daily feeder visits were recorded with computerized feeders. Ketosis in 8 cows was characterized by rapid daily decreases in feed intake [−10.4kg of fresh matter (FM)], feeding time (−45.5min), and feeding rate (−25.3g of FM/min) during an average of 3.6 d before diagnosis by farm staff. Acute locomotion disorders in 14 cows showed smaller daily decreases in feed intake (−1.57kg of FM) and feeding time (−19.1min), and a daily increase in feeding rate (+21.6g of FM/min) during an average of 7.7 d from onset to diagnosis. The effects of chronic lameness on short-term feeding behavior were assessed by analyzing changes during the 30 d before and 30 d after all cows were checked for foot lesions and trimmed, and cows were classified as either lame (n = 81) or not lame (n = 62). During the 30 d before trimming, cows classified as lame showed significant changes in daily feeding time, number of daily visits, and feeding rate, but nonlame cows did not. In lame cows, the observed daily changes (slope) for the 30 d before and the 30 d after trimming were −0.75 and +0.32 min/d for daily feeding time, −0.35 and +0.31 for daily number of visits, and +0.77 and −0.35 g/min for feeding rate, respectively. These changes in feeding behavior were not different among cows consuming low or high forage rations. Daily feeding time was the feeding characteristic that changed most consistently in relation to the studied disorders. A simple algorithm was used to identify cows whose daily feeding time was lower than the previous 7-d rolling average minus 2.5 standard deviations. The algorithm resulted in detection of more than 80% of cows with acute disorders at least 1 d before diagnosis by farm staff. Short-term feeding behavior showed very characteristic changes with the onset of disorders, which suggests that a system that monitors short-term feeding behavior can assist in the early identification of sick cows.

Restoring avian island endemics: use of supplementary food by the endangered Pink Pigeon (Columba mayeri)

The wild population of Pink Pigeons (Columba mayeri) of Mauritius has recovered from ten individuals in 1990 to ~390 birds in 2008. Limited availability of native feeding habitat is a primary factor restricting further increases in population. Current management of the species includes provision of supplementary food (wheat) and restoration of native forest habitat. This study investigated dependence on supplementary food by examining patterns of supplementary food use and social interactions in two Pink Pigeon subpopulations. During 72 h of observations over a 10-week study period 99% of the birds visited supplementary feeding stations, and the combined duration of these visits per individual was 0–1.7% of the total observation period. Frequency of visits peaked in late afternoon and timing of feeding visits also varied between sexes in one subpopulation, where males fed for longer after daytime nest incubation (1600–1800 hours) than females, and females fed for longer than males throughout the middle of the day (1000–1300 hours). Younger birds (<1 year old) fed more frequently than older birds. Implications of these findings for the long-term management of this and other recovering avian populations are discussed.

Predator-induced reductions in nest visitation rates are modified by forest cover and food availability

Bird parents can alert predators to the location of their nest. One mitigating option is that parents reduce their nest visitation rate in exchange for a lower predation risk. Here, using field data and experiments, we show that Siberian jay Perisoreus infaustus parents adjust feeding visit rates depending on an interaction of 3 factors: predator activity, nest concealment, and food availability. The rate of nest visits increased with the degree of nest concealment; yet, this relationship was modified by the presence of corvid predators. As the vegetation became more dense, parents at sites with high corvid activity disproportionately increased their feeding visit rates when compared with birds at sites with low corvid activity. We experimentally assessed how nesting cover affects this response of parents to the presence of corvids by using an Eurasian jay Garrulus glandarius model. Parents nesting at open sites ceased nest visits, whereas those nesting in dense forest continued feeding, albeit at a lower rate. Cover may thus not fully compensate for the effect of predator activity on feeding visit rates. However, offspring exposed to high predator activity might still receive the same amount of food because parents may adjust load sizes to compensate. This idea was confirmed by an experiment showing that in areas of high predator activity, food-supplemented birds significantly decreased nest visits when compared with nonsupplemented birds. These results indicate that some bird species can employ multiple nest-defense strategies to reduce predator-attracting nest visits; yet, these strategies may carry fitness consequences through reduced offspring quality.

Breeding biology and provisioning of nestling snow buntings in the Canadian High Arctic

We examined basic breeding biology, as well as the effects of parental sex, brood size, nestling age, and nest habitat on foraging distances and parental food delivery rates of snow buntings (Plectrophenax nivalis) on Devon Island, NT, Canada, in the summers of 2003–2006. Clutch sizes and initiation dates were similar to those found in previous studies, although nest density was much higher. Feeding rates and foraging distances of buntings differed depending on the size and age of the brood, but were similar between nest habitats. Unlike in earlier studies, we found that male buntings made fewer feeding visits, but traveled longer distances to forage for food than females. Whether these differences between the sexes relate to reducing competition for prey, or to differing sex roles in parental care due to the poorly insulated nest cavities of this species, remains to be determined.

Foraging scent marks of bumblebees: footprint cues rather than pheromone signals

In their natural habitat foraging bumblebees refuse to land on and probe flowers that have been recently visited (and depleted) by themselves, conspecifics or other bees, which increases their overall rate of nectar intake. This avoidance is often based on recognition of scent marks deposited by previous visitors. While the term 'scent mark' implies active labelling, it is an open question whether the repellent chemicals are pheromones actively and specifically released during flower visits, or mere footprints deposited unspecifically wherever bees walk. To distinguish between the two possibilities, we presented worker bumblebees (Bombus terrestris) with three types of feeders in a laboratory experiment: unvisited control feeders, passive feeders with a corolla that the bee had walked over on its way from the nest (with unspecific footprints), and active feeders, which the bee had just visited and depleted, but which were immediately refilled with sugar-water (potentially with specific scent marks). Bumblebees rejected both active and passive feeders more frequently than unvisited controls. The rate of rejection of passive feeders was only slightly lower than that of active feeders, and this difference vanished completely when passive corollas were walked over repeatedly on the way from the nest. Thus, mere footprints were sufficient to emulate the repellent effect of an actual feeder visit. In confirmation, glass slides on which bumblebees had walked on near the nest entrance accumulated hydrocarbons (alkanes and alkenes, C23 to C31), which had previously been shown to elicit repellency in flower choice experiments. We conclude that repellent scent marks are mere footprints, which foraging bees avoid when they encounter them in a foraging context.

A critical analysis of ‘false-feeding’ behavior in a cooperatively breeding bird: disturbance effects, satiated nestlings or deception?

False feeding,' where helpers arrive at nests with food but fail to provision the young, has been reported in several cooperative species. This and other potentially 'deceptive' behavior has been interpreted as indicating that helping may operate as a signal within such social groups. We critically examine these phenomena in the provisioning behavior of the bell miner Manorina melanophrys. Exces- sively close observation distances can artificially elevate the rate of false feeding in this (and other) species, but once this had been accounted for, there was little evidence for any 'deceptive' behavior by helpers or breeders. Natural and experimentally induced variation in the presence of a potential conspecific audience at the nest did not have any consistent influence upon the rate of false feeds, which was low at 7.94% of 6,880 nest visits. Instead, encountering unexpectedly low levels of brood demand provided a more parsimonious explanation for those visits where helpers failed to feed nestlings or ate the food themselves. Failure to completely transfer a load to nestlings was more likely when the load contained a high proportion of sticky lerp, indicating a simple prey-transfer problem. Finally, individu- als that arrived at nests without prey were often members of neighboring breeding pairs, suggesting that these few non- feeding visits may instead involve an information-gathering function. We, therefore, suggest that future studies explicitly exclude the possibility of observer disturbance and all aspects of normal provisioning behavior before applying the terms 'false feeding' or 'deceptive' and inferring anything more than straightforward helping at the nest.

Learning Performance of Foraging Bumblebees (Bombus terrestris) under Manipulation of Inter-visit Time Intervals (Hymenoptera: Apidae)

Short-term information affects feeding choices in bees. When making rapid successive choices, bees tend to forage in a flower-constant manner, and perform well in delayed matching-to-sample learn< ing tests. Flower constancy and learning performance decline when consecutive choices are more than five seconds apart. It was suggested that visual stimuli associated with the last-encountered food source are retained in the bees' working memory, and prime their next choice. The contents of the working memory may either fade, or be replaced by other visual input, within a few seconds. To distinguish between these possibilities, the visual input available to bees between consecutive feeding choices was controlled. Bombus terrestris (Linnaeus 1758) bumblebees, foraging on differentially-rewarding artificial feeders of different colors, were exposed to either 1.5 seconds or 15 seconds of darkness following each feeder visit. The bees did not fly in the dark, therefore these treatments differed in the time elapsed between successive feeding choices, but not in the visual input available to the foragers during this time. The bees' feeder choices were compared to the choices of untreated controls. Control bees chose rewarding feeders significantly more often than bees from both darkness treatments. Shifts between feeders of different colors, and choices of non-rewarding feeders, were associated with long time-intervals between visits in the control treatment, but not in the darkness treatments. The results support previous evidence that short-term information, when available, improves the learning performance of bees. The similarity in the bees' foraging performance in the two darkness treatments suggests that the decay of working memory may involve acquisition of new visual data. Alternative interpretations for the similar results in the two darkness treatments arc discussed.

Nest mate size, but not short-term need, influences begging behavior of a generalist brood parasite

Hosts of generalist brood parasites often vary with regards to their life-history traits, and these differences have the potential to influence the competitive environment experienced by brood-parasitic nestlings. Although begging by brood parasites is more exaggerated than their hosts, it is unclear if generalist brood parasites modulate their begging behavior relative to host size. I examined the begging behavior of brown-headed cowbird (Molothrus ater) nestlings when competing against nest mates that differ in size and under different levels of short-term need. Cowbird nestlings begged on nearly all feeding visits, responded to adults as fast as (or faster than) their nest mates, and typically begged more intensively than their nest mates. Latency to beg, time spent begging, and maximum begging posture of cowbirds were similar during supplementation and deprivation treatments, indicating begging intensity was not influenced by short-term need. Time spent begging by cowbirds varied among hosts of 3 different sizes when short-term need was standardized, suggesting that nest mate size strongly influenced begging behavior. Cowbirds obtained more food when competing against an intermediate-sized host due to lower provisioning rates of small hosts or because of increased competitive ability of large host nestlings. Overall, cowbirds obtained the greatest volume of food per unit time spent begging when competing against intermediate hosts, but this value approached that of the small host when adjusted for modal brood size. These results demonstrate that cowbirds adjust their begging relative to the size of the hosts against which they compete but not to levels of short-term need. Key words: begging behavior, begging intensity, brown-headed cowbird, Molothrus ater, nestling competition, short-term need. [Behav Ecol]

Age at introduction to the group affects dairy calves’ use of a computer-controlled milk feeder

Use of computer-controlled milk feeders in dairy calves often involves large group sizes and continuous introduction of new calves, which may cause problems due to competition especially for young calves. Ninety-eight dairy calves were paired (one 6-day-old and one 14-day-old) and introduced into an existing group (group size median 18 (interquartile range 16–24)). During the first week calves were guided to the feeder by the stockperson if they had consumed less than half of their daily milk allowance. Number of days guided to the feeder and milk feeder visits were recorded. Due to the dynamic group structure, blocks of calves were created and the dataset was divided into two halves. Each half dataset contained four blocks, and calves in separate blocks were independent within each half dataset. Calves introduced at day 6 had a higher probability of requiring guidance to the feeder than calves introduced at day 14 ( P < 0.001). Calves introduced at day 6 spent less time in the milk feeder during days 1–12 after introduction ( P < 0.01). This was mainly due to these calves spending less time during unrewarded visits to the milk feeder ( P < 0.01). However, calves introduced at day 6 also spent less time in the milk feeder after ingesting milk ( P < 0.01), and ingested less milk ( P < 0.01). The results show that the younger calves had more difficulties in getting access to the milk feeder during the first period after introduction and required more guidance by the stockperson. It is suggested that 6-day-old calves are less able to compete for milk feeder access in large groups.