Corrigendum: What Is It Like to Be a Bass? Red Herrings, Fish Pain and the Study of Animal Sentience.

[This corrects the article DOI: 10.3389/fvets.2022.788289.].

What Is It Like to Be a Bass? Red Herrings, Fish Pain and the Study of Animal Sentience.

Debates around fishes' ability to feel pain concern sentience: do reactions to tissue damage indicate evaluative consciousness (conscious affect), or mere nociception? Thanks to Braithwaite's discovery of trout nociceptors, and concerns that current practices could compromise welfare in countless fish, this issue's importance is beyond dispute. However, nociceptors are merely necessary, not sufficient, for true pain, and many measures held to indicate sentience have the same problem. The question of whether fish feel pain - or indeed anything at all - therefore stimulates sometimes polarized debate. Here, we try to bridge the divide. After reviewing key consciousness concepts, we identify "red herring" measures that should not be used to infer sentience because also present in non-sentient organisms, notably those lacking nervous systems, like plants and protozoa (P); spines disconnected from brains (S); decerebrate mammals and birds (D); and humans in unaware states (U). These "S.P.U.D. subjects" can show approach/withdrawal; react with apparent emotion; change their reactivity with food deprivation or analgesia; discriminate between stimuli; display Pavlovian learning, including some forms of trace conditioning; and even learn simple instrumental responses. Consequently, none of these responses are good indicators of sentience. Potentially more valid are aspects of working memory, operant conditioning, the self-report of state, and forms of higher order cognition. We suggest new experiments on humans to test these hypotheses, as well as modifications to tests for "mental time travel" and self-awareness (e.g., mirror self-recognition) that could allow these to now probe sentience (since currently they reflect perceptual rather than evaluative, affective aspects of consciousness). Because "bullet-proof" neurological and behavioral indicators of sentience are thus still lacking, agnosticism about fish sentience remains widespread. To end, we address how to balance such doubts with welfare protection, discussing concerns raised by key skeptics in this debate. Overall, we celebrate the rigorous evidential standards required by those unconvinced that fish are sentient; laud the compassion and ethical rigor shown by those advocating for welfare protections; and seek to show how precautionary principles still support protecting fish from physical harm.

Competition during the milk-feeding stage influences the development of feeding behavior of pair-housed dairy calves.

This study investigated how the feeding behavior of pair-housed calves develops in response to reduced teat and feed place availability. Twenty Holstein bull calves were pair housed and provided with milk replacer (MR) and grain concentrate ad libitum via either (1) 1 teat and feed bucket/pen, such that calves could not feed simultaneously [competitive feeding (CF)] or (2) 2 teats and feed buckets/pen [noncompetitive feeding (NCF)]. The calves were weaned during wk 7 of life by incrementally diluting the MR. Postweaning, all pens were managed identically and offered a complete pelleted diet ad libitum via 2 feed buckets/pen (NCF) in period 1 (wk 8 and 9) and period 3 (wk 12 and 13) and exposed to a competitive challenge with CF in period 2 (wk 10 and 11). Feeding times and competitive interactions were recorded from video for 3 d/wk in wk 2, 4, and 6 and 2 d/wk in wk 8 to 13. Meal criteria were used to calculate daily meal frequency, meal time, and synchronized meal time (the percentage of meal time when calves within the pen were engaged in simultaneous meals). Milk replacer intake was subject to a treatment × week interaction, with calves in CF pens having lower MR intake (wk 2: 8.3 vs. 10.0 L/calf per day for CF vs. NCF), but compensating by increasing intake to a greater extent over time (wk 4-5: 13.3 vs. 11.7 L/d for CF vs. NCF). Corresponding to MR intake, meal frequencies and feeding times evolved differently over this period, increasing in CF pens and decreasing in NCF pens (wk 2: 5.8 vs. 11.1 and wk 4-6: 6.2 vs. 5.1 meals/d for CF vs. NCF). Calves in CF pens also spent less time engaged in synchronized meals (28 vs. 51% of meal time; standard error=7.1) and displaced each other 5 times more frequently during synchronized eating. Postweaning, calves in previously CF pens maintained 5 times greater displacement frequencies and had fewer overlapping meals than calves in previously NCF pens (34.5 vs. 40.7% of meals, respectively). Postweaning, when calves were all fed noncompetitively (2 buckets/pen in periods 1 and 3), calves previously fed CF had greater intakes in period 3 (4.87 vs. 4.44 kg/d) and a tendency for greater intake in period 1 (2.80 vs. 2.63 kg/d), greater rates of intake in period 3 (87.8 vs. 72.0 g/min) and a tendency for greater rates of intake in period 1 (44.3 vs. 38.9 g/min), and greater meal frequencies in both periods (11.1 vs. 9.9 meals/d). In the competitive challenge period (1 bucket/pen in period 2), intake, rates of intake, and meal frequencies were subject to treatment × week interactions: calves in NCF pens had lower intake and meal frequencies, but increased meal frequency, intake, and rate of intake over time to a greater extent than calves previously in CF pens. These results indicate that calves are able to adapt to moderate competition by increasing meal frequency and that behavioral responses to competition persist postweaning.

Effect of feed presentation on feeding patterns of dairy calves.

The objectives of this study were to determine the effect of feed presentation on meal frequency and duration, as well as diurnal feeding patterns of dairy calves, and to assess any longer-term differences in feeding patterns resulting from previous experience. Twenty Holstein bull calves were exposed from wk 1 to 8 of life to 1 of 2 feed presentation treatments: concentrate and chopped grass hay (<2.5 cm) offered at a ratio of 7:3 as a mixture (MIX), or as separate components (COM). Feed was provided ad libitum. Calves received 8L/d of milk replacer (1.2 kg of dry matter), with the amount progressively reduced after 5 wk to facilitate weaning by the end of wk 7. At the beginning of wk 9, all calves received the MIX diet and remained on trial for an additional 3 wk. Feeding behavior was recorded from video for 4d during wk 6, 8, 9, and 11. In wk 6, calves fed MIX spent more time feeding than calves fed COM (56.7 vs. 46.8 min/d). In wk 8, calves fed MIX spent more time feeding (174.0 vs. 139.1 min/d) and had a lower rate of intake (11.5 vs. 14.7 g/min) compared with calves fed COM. Meal frequency was similar between treatments (12.2 meals/d). Diurnal feeding patterns in wk 8 were also affected by feed presentation, with calves fed MIX spending less time feeding at time of feed delivery and more time feeding throughout the rest of the daylight hours than calves fed COM. Diurnal feeding patterns of hay and concentrate in wk 8 differed for calves fed COM, with more time spent consuming hay at time of feed delivery and less time spent consuming hay throughout the rest of the day. Once calves previously fed COM were transitioned to the MIX diet in wk 9, meal frequency, meal duration, and diurnal feeding patterns were similar between treatments: both treatments spent similar amounts of time feeding (173.9 min/d) and had similar peaks in feeding activity at time of feed delivery, sunrise, and sunset. Provision of hay and concentrate to young calves as a mixed ration, compared with separate components, increases time spent feeding and results in more evenly distributed diurnal feeding patterns. However, differences in feeding patterns resulting from feed presentation did not persist after 8 wk of age, when all calves were fed a mixed ration.

Effect of early exposure to different feed presentations on feed sorting of dairy calves.

This study examined how early exposure to different feed presentations affects development of feed sorting in dairy calves. Twenty Holstein bull calves were exposed for the first 8 wk of life to 1 of 2 feed presentation treatments: concentrate and chopped grass hay (<2.5cm) offered ad libitum at a ratio of 7:3 as a mixture (MIX), or as separate components (COM). Calves received 8L/d of milk replacer (1.2kg of dry matter), with the amount progressively reduced after 5 wk to facilitate weaning by the end of wk 7. All calves received the MIX diet in wk 9 to 11 and, subsequently, a novel total mixed ration (TMR; containing 40.5% corn silage, 22.0% haylage, 21.5% high-moisture corn, and 16.0% protein supplement) in wk 12 to 13. Intake was recorded daily and calves were weighed twice a week. Fresh feed and orts were sampled on d 1 to 4 of wk 6, 8, 9, 11, 12, and 13 for analysis of feed sorting, which was assessed through nutrient analysis for the MIX diet and particle size analysis for the TMR. The particle separator had 3 screens (19, 8, and 1.18mm) producing long, medium, short, and fine particle fractions. Sorting of nutrients or particle fractions was calculated as the actual intake as a percentage of predicted intake; values >100% indicate sorting for, whereas values <100% indicate sorting against. Feed presentation did not affect dry matter intake or growth. Prior to weaning, all calves selected in favor of hay; MIX calves consumed more neutral detergent fiber (NDF) than predicted (103.6%) and less nonfiber carbohydrates (NFC) than predicted (92.6%), and COM calves consumed, as a percentage of dry matter intake, 40.3% hay (vs. 30% offered rate). In wk 8, calves fed COM consumed more NFC than calves fed MIX (1.0 vs. 0.95kg/d) and less NDF (0.43 vs. 0.54kg/d), indicating greater selection in favor of concentrate. However, when provided the MIX diet, calves previously fed COM did not sort, whereas calves previously fed MIX consumed more NFC intake than predicted (103.2%) and less NDF intake than predicted (97.6%). Calves previously fed MIX maintained increased sorting after transition to the novel TMR, sorting against long particles (86.5%) and for short (101.8%) and fine (101.2%) particles. These results indicate that initially providing dairy calves with solid feeds as separate components, compared with as a mixed ration, reduces the extent of feed sorting in the weeks after transition to a common ration.

Feed delivery method affects the learning of feeding and competitive behavior in dairy heifers.

The objective of this study was to determine how different feeding methods may affect the learning of feeding, sorting, and competitive behavior of growing dairy heifers. We hypothesized that heifers previously fed a total mixed ration (TMR) would distribute their feeding time more evenly throughout the day, sort the new ration less, compete less for feed, maintain a more solid fecal consistency, and continue to grow rapidly compared with heifers previously fed a top-dressed ration (TDR). Thirty-two Holstein heifers (237.2+/-21.9 d of age) were divided into 8 groups of 4 and exposed to 1 of 2 treatments for 13 wk: 1) TMR or 2) TDR, with each containing 65% grass/alfalfa haylage and 35% textured concentrate on a dry matter (DM) basis. Following this feeding period, all heifers were switched to an unfamiliar TMR containing 56.1% grass/alfalfa haylage, 21.0% corn silage, 21.0% high-moisture corn, and 1.9% mineral supplement (DM basis) for 7 wk. Group DM intakes were recorded daily throughout the experiment. Feeding behavior, recorded using time-lapse video, and sorting behavior were measured for 7 d during wk 1, 4, and 7 after the dietary change. Feeding competition was measured on d 2, 4, and 6 of each recording week. Sorting activity was determined through particle size analysis of the fresh feed and orts. The particle size separator separated feed into 4 fractions (long, medium, short, and fine). Sorting of each fraction was calculated as actual intake expressed as a percentage of predicted intake. Animals were scored for fecal consistency twice weekly, using a scale from 1 (liquid) to 4 (solid). Heifers were weighed every 2 wk. Neither DM intake (9.0 kg/d) nor average daily gain (1.2 kg/d) differed between treatments. Sorting also did not differ between treatments. Heifers tended to spend more time feeding if they had previously been fed a TDR (198.8 vs. 186.8 min/d). As they had done before the dietary change, heifers previously fed the TDR spent more time at the bunk in the 2h following feed delivery (40.6 vs. 25.9 min/d). Heifers previously fed the TDR were displaced from the feed bunk more frequently than heifers previously fed the TMR (23.0 vs. 13.1 times/d), particularly during the 2-h period following feed delivery. Fecal scores were lower (more fluid in consistency) for heifers originally fed the TDR (3.2 vs. 3.7). The continued difference in feed bunk competition suggests that heifers previously fed the TDR had learned these patterns in the past, retaining them even when switched to an unfamiliar ration. Furthermore, lower fecal scores for heifers previously fed the TDR suggest altered rumen fermentation, possibly because of altered diurnal consumption patterns. These results show that feeding a TMR to replacement dairy heifers from a young age promotes a more even diurnal feeding pattern, minimizes feed bunk competition, and promotes a more solid fecal consistency.

Effect of feed delivery method on the behavior and growth of dairy heifers.

The objective of this study was to determine the effects of feed delivery method on growth, feeding competition, feeding, and sorting behavior of dairy heifers. Thirty-two Holstein heifers (146.2+/-21.9 d of age) were divided into 8 groups of 4 and exposed to 1 of 2 feed delivery treatments for 13 wk. The treatment rations contained 65% grass/alfalfa haylage and 35% textured concentrate (on a dry matter basis) fed as a 1) total mixed ration (TMR) or 2) top-dressed ration (TDR). Group dry matter intakes were recorded daily throughout the experiment. Feeding behavior, recorded using time-lapse video, and sorting behavior were measured for 7 d during each of wk 1, 5, 9, and 13. Sorting activity was determined through particle size analysis of the fresh feed and orts. The particle size separator separated feed into 4 fractions (long, medium, short, and fine). Sorting of each fraction was calculated as actual intake expressed as a percentage of predicted intake. Heifers were fecal scored for consistency of stool twice weekly using a scale from 1 (liquid) to 4 (solid); heifers were weighed every 2 wk. Neither dry matter intake (7.3 kg/d) nor average daily gain (1.3 kg/d) differed between treatments. Heifers fed the TDR tended to consume less neutral detergent fiber than heifers fed the TMR (4.77 vs. 4.91 kg/d). Heifers fed the TDR sorted against long particles (98.9 vs. 96.0%) and consumed short particles (100.3 vs. 101.1%) to a greater extent than did heifers fed the TMR. Daily feeding time did not differ between treatments (201.0 min/d), but heifers on the TDR did spend more time at the bunk in the 2h following feed delivery (50.1 vs. 32.0 min/d). Heifers fed the TDR were displaced from the feed bunk more frequently than heifers fed the TMR (17.6 vs. 8.6 times/d), particularly during the 2-h period following feed delivery. Fecal scores were lower for heifers on the TDR (2.7 vs. 3.4). These results suggest that feeding a TMR to replacement dairy heifers may promote a more even diurnal feeding pattern, minimize feed sorting and feed bunk competition, and promote more solid fecal consistency.

Absorbencies of six different rodent beddings: commercially advertised absorbencies are potentially misleading.

Moisture absorbency is one of the most important characteristics of rodent beddings for controlling bacterial growth and ammonia production. However, bedding manufacturers rarely provide information on the absorbencies of available materials, and even when they do, absorption values are usually expressed per unit mass of bedding. Since beddings are usually placed into cages to reach a required depth rather than a particular mass, their volumetric absorbencies are far more relevant. This study therefore compared the saline absorbencies of sawdust, aspen woodchips, two virgin loose pulp beddings (Alpha-Dri and Omega-Dri), reclaimed wood pulp (Tek-Fresh), and corncob, calculated both by volume and by mass. Absorbency per unit volume correlated positively with bedding density, while absorbency per unit mass correlated negatively. Therefore, the relative absorbencies of the beddings were almost completely reversed depending on how absorbency was calculated. By volume, corncob was the most absorbent bedding, absorbing about twice as much saline as Tek-Fresh, the least absorbent bedding. Conversely, when calculated by mass, Tek-Fresh appeared to absorb almost three times as much saline as the corncob. Thus, in practical terms the most absorbent bedding here was corncob, followed by the loose pulp beddings; and this is generally supported by their relatively low ammonia production as seen in previous studies. Many factors other than absorbency determine whether a material is suitable as a rodent bedding, and they are briefly mentioned here. However, manufacturers should provide details of bedding absorbencies in terms of volume, in order to help predict the relative absorbencies of the beddings in practical situations.

The use of operant technology to measure behavioral priorities in captive animals.

Addressing the behavioral priorities of captive animals and the development of practical, objective measures of the value of environmental resources is a principal objective of animal welfare science. In theory, consumer demand approaches derived from human microeconomics should provide valid measures of the value of environmental resources. In practice, however, a number of empirical and theoretical problems have rendered these measures difficult to interpret in studies with animals. A common approach has been to impose a cost on access to resources and to use time with each resource as a measure of consumption to construct demand curves. This can be recorded easily by automatic means, but in a number of studies, it has been found that animals compensate for increased cost of access with longer visit time. Furthermore, direct observation of the test animals' behavior has shown that resource interaction is more intense once the animals have overcome higher costs. As a consequence, measures based on time with the resource may underestimate resource consumption at higher access costs, and demand curves derived from these measures may not be a true reflection of the value of different resources. An alternative approach to demand curves is reservation price, which is the maximum price individual animals are prepared to pay to gain access to resources. In studies using this approach, farmed mink (Mustela vison) paid higher prices for food and swimming water than for resources such as tunnels, water bowls, pet toys, and empty compartments. This indicates that the mink placed a higher value on food and swimming water than on other resources.

The identification of abnormal behaviour and behavioural problems in stabled horses and their relationship to horse welfare: a comparative review.

Many behaviours in domestic animals, such as the 'stable vices' of horses, are treated because they are considered undesirable for economic or cultural reasons, and not because the activity affects the horse's quality of life. The impact of a behaviour on the human reporter is not a function of its impact on the animal performer, and an understanding of the causes and effects of the particular activity is necessary to assess the costs and benefits of treatment. Where the behaviour is a sign of poor welfare, such as an inadequate environment, treatment can best be achieved by removing these underlying causal factors. Pharmacological or physical prevention of a behaviour can be justified only if the behaviour causes harm to the performer or to others. In these cases, prevention of the behaviour without addressing its causes is no cure and may result in its perseverance in a modified form or the disruption of the animal's ability to adapt to its environment. Where the behavioural 'problem' causes no harm and is not related to poor housing, then the education of the reporter, rather than treatment of the performer, may be the best solution.

Stereotypies and suffering.

Stereotypies often develop in environments that independent evidence shows cause poor welfare. Thus the development od stereotypies indicates that well-being has probably been poor, with the animal motivated to show a behaviour pattern that it could not perform normally or to completion. The continued performance of stereotypies may also indicate current suffering. However, an individual or population's degree of stereotypy does not necessarily correspond to the degree to which its well-being or welfare is impaired. This would require individual differences in stereotypy level to be the product of motivational differences and nothing else. In fact, they are also likely to be influenced by an animal's tendency to respond to the eliciting aspects of its environment with active behaviour rather than in a more inactive way. Stereotypy levels are also likely to be influenced by the general propensity of the individual to develop inflexible behavioural routines. Furthermore, as a stereotypy develops and becomes more habit-like it may be performed in circumstances where well-being is not at stake. Thus when comparing animals, lower levels of stereotypy do not necessarily reflect better well-being. General rules about the levels of stereotypy that are deemed "acceptable" from a welfare point of view are of limited use in reducing animal suffering unless they take take these factors into account. There is a great need for more research into the developmental processes responsible for stereotypies.