Measurement of feeding motivation in sheep and the effects of food restriction

Positive Aspects of Welfare in Sheep: Current Debates and Future Opportunities

The concept of positive welfare is an expansion of the traditional understanding that animal welfare is defined by minimizing stress, pain, suffering, and disease. Positive welfare shifts the animal welfare narrative from a focus on reducing negative experiences to proactively providing animals with opportunities to have positive experiences and feelings. The concept, although around for several decades, is in its infancy in terms of developing ways of assessing positive welfare on farms, especially in extensive systems, and there are challenges in the adoption of positive welfare practices and the monitoring of continuous improvement at the farm level. Using an iterative approach, this critical review aims to explore the extent to which positive welfare interventions and indicators are positioned and have been developed within the animal welfare literature for sheep. This paper critiques existing positive welfare indicators, such as choices in food and the physical environment, conspecific social synchronization, maternal bonds, intergenerational knowledge transfer, positive human-animal relationships, etc., as currently assessed by the 'good life framework'. It also reviews the characteristics of scientific measures for (positive) affective states in the current sheep literature and their potential contribution to understanding positive welfare states in sheep. In conclusion, this paper provides recommendations for future research regarding sheep welfare.

Welfare of sheep and goats at slaughter

The killing of sheep and goats for human consumption (slaughtering) can take place in a slaughterhouse or on-farm. The processes of slaughtering that were assessed for welfare, from the arrival of sheep and goats until their death (including slaughtering without stunning), were grouped into three main phases: pre-stunning (including arrival, unloading from the truck, lairage, handling and moving of sheep and goats); stunning (including restraint); and bleeding. Stunning methods were grouped into two categories: mechanical and electrical. Twelve welfare consequences that sheep and goats may experience during slaughter were identified: heat stress, cold stress, fatigue, prolonged thirst, prolonged hunger, impeded movement, restriction of movements, resting problems, social stress, pain, fear and distress. These welfare consequences and their relevant animal-based measures are described in detail in this Scientific Opinion. In total, 40 welfare hazards that could occur during slaughter were identified and characterised, most of them related to stunning and bleeding. Staff were identified as the origin of 39 hazards, which were attributed to the lack of appropriate skill sets needed to perform tasks or to fatigue. Measures to prevent and correct hazards were identified, and structural and managerial measures were identified as those with a crucial role in prevention. Outcome tables linking hazards, welfare consequences, animal-based measures, origin of hazards and preventive and corrective measures were developed for each process. Mitigation measures to minimise welfare consequences are proposed.

Automated feeding of sheep. 1. Changes in feeding behaviour in response to restricted and ad libitum feeding

Context Automated feeding units allow the recording of individual feeding behaviour of group-housed sheep and provide data for research into feed efficiency. Aim It was hypothesised that measures of feeding behaviour such as the number of non-feeding events, meal size, eating rate and meal duration would change under different levels of feeding. Method Maternal Composite ewes (n = 126, 18 per pen) were fed a hay-based pellet using automated feeding units (2 per pen) for four periods differing in total daily feed allowance (kg/day) and meal allowance (g/meal). Sheep were initially fed ad libitum (meal allowance ~1000 g) for 19 days during an adaptation period, before restricted feeding for 41 days at daily allowances of 40%, 60%, 80%, 100%, 140% and 180% of estimated maintenance requirements, with a meal allowance of ~100 g. These restricted daily allowances were the experimental treatments that were randomly applied to sheep and replicated three times per pen. The daily allowance was then adjusted to 1.4 kg/day (with a ~200 g meal allowance) for all sheep over 5 days, before ad libitum feeding of all sheep for a period of 16 days. All feeding and non-feeding events were recorded. Key results Under restricted feeding, sheep altered the timing of their meals to consume more meals during the early morning after daily allowances were reset at 0000 hours. This change was more pronounced for sheep fed a smaller proportion of maintenance. The number of non-feeding events (~8/day) was not affected by the level of restricted feeding, but meal size was smaller, meal duration was longer and eating rate was lower for sheep fed 40% of their maintenance requirement. Under ad libitum feeding, sheep reverted to a preferred meal size and number of meals, with fewer than two non-feeding events per day, but differences in eating rate remained. Conclusions Sheep feeding behaviours adapt and respond quickly to changes in daily allowance and offered meal size, but the similar number of non-feeding events at different proportions of maintenance feeding suggest that non-feeding events may not reflect levels of hunger. Implications Our observations suggest that sheep are capable of learning and adapting to different levels of feeding and that this may allow for automated feeding systems to supplementary feed larger numbers of sheep under extensive situations.

Short communication: Motivation to walk affects gait attributes

Lameness is a major welfare problem in the dairy industry. Environmental factors, such as flooring surface, as well as cow-level factors, such as udder fill, can influence gait. The aim of the current study was to test whether motivation to walk affects gait attributes and whether this effect differs between lame and sound cows. We trained cows to walk down an alley for a food reward and assessed walking speed, stride length, head bob, and back arch of cows previously identified as either lame (n = 7) or sound (n = 10). Cows were assessed when they walked toward a food reward and toward no reward. Cows walked faster and had longer stride length and less variation in head bob when approaching the reward; these effects were similar in both sound and lame cows. We concluded that motivation to walk affects several gait attributes of dairy cows.

Determining a Welfare Prioritization for Horses Using a Delphi Method

Simple Summary

Horses are used for a wide range of different purposes and may be vulnerable to a large number of different welfare issues, some of which are unique to equines, such as responses to being ridden or trained. Compared to farmed livestock, their welfare has received less attention, but concern for their welfare is increasing. Welfare issues can arise from the environments in which animals are kept, how they are treated by their human caregivers and their health. To determine which of the issues are most important and may need the greatest attention in terms of research effort or owner education, we used a process of eliciting expert opinion. Through a series of surveys and ranking of issues, we determined that, in the opinion of equine experts, the most important issues for horses were poor disease prevention, issues arising when old or sick horses are not promptly euthanized, lack of owner knowledge of welfare needs of horses, fear and stress involved in horse use, inability of owners to recognize pain behaviour, obesity and inadequate feeding practices. Prioritizing different welfare issues can help to focus attention on the most pressing or severe issues causing the greatest amount of suffering.

Abstract

Equine welfare issues are receiving increasing attention in the UK, but welfare problems can arise from a wide range of causes. In order to identify the most important welfare concerns for horses, we used a Delphi method with 19 equine welfare experts. An initial list of 84 equine welfare issues was generated using an online discussion board and NVivo thematic analysis. Subsequently, experts ranked these welfare issues for perceived prevalence, severity and duration of suffering associated with each issue on a 6-point Likert scale. All issues with a mean score of 3 or above (n = 37) were included in subsequent rounds. Finally, a subset of experts attended a two-day workshop to determine the final priority list of welfare issues. The welfare issues perceived to be most prevalent were lack of biosecurity, delayed euthanasia, lack of owner knowledge of equine welfare needs, fear and stress from use, and obesity. The issues considered to cause greatest suffering for individual horses were delayed euthanasia, lack of recognition by owners of pain behaviour, large worm burdens, obesity and being fed unsuitable diets for equine feeding behaviour. These outcomes can help to focus research and education interventions on the most pressing welfare issues for horses.

A Ten-Stage Protocol for Assessing the Welfare of Individual Non-Captive Wild Animals: Free-Roaming Horses (Equus Ferus Caballus) as an Example

Knowledge of the welfare status of wild animals is vital for informing debates about the ways in which we interact with wild animals and their habitats. Currently, there is no published information about how to scientifically assess the welfare of free-roaming wild animals during their normal day-to-day lives. Using free-roaming horses as an example, we describe a ten-stage protocol for systematically and scientifically assessing the welfare of individual non-captive wild animals. The protocol starts by emphasising the importance of readers having an understanding of animal welfare in a conservation context and also of the Five Domains Model for assessing welfare. It goes on to detail what species-specific information is required to assess welfare, how to identify measurable and observable indicators of animals' physical states and how to identify which individuals are being assessed. Further, it addresses how to select appropriate methods for measuring/observing physical indicators of welfare, the scientific validation of these indicators and then the grading of animals' welfare states, along with assigning a confidence score. Finally, grading future welfare risks and how these can guide management decisions is discussed. Applying this ten-stage protocol will enable biologists to scientifically assess the welfare of wild animals and should lead to significant advances in the field of wild animal welfare.

Physicochemical and sensory characterization of meat from lambs subjected to feeding restrictions

Abstract This study aimed to evaluate the physicochemical and sensory properties of the meat of Santa Ines lambs subjected to quantitative nutrient restrictions. Twenty-four confined animals received diets with 30% and 60% feeding restriction levels, and were compared to a controlled group without feeding restrictions (ad libitum). After slaughter, the Longissimus thoracis et lumborum (LTL) muscle was collected for the evaluation, being the lamb meat was affected by the feeding restrictions (p < 0.05). The lipid content decreased with the increased restriction, whereas the shear strength, the lightness (L*) and the red index (a*) were lower in lambs treated with the 60% restriction and there were significant variation (p < 0.05) in the sensory properties according to diet. Due to the greater score in relation to aroma and similarity to control with respect to flavor, tenderness and overall evaluation, the 30% feeding restriction level can be considered an economic and efficient alternative for the maintenance of quality in lamb meat.

Cows are highly motivated to access a grooming substrate

In natural environments, cattle use trees and other abrasive surfaces to scratch and groom themselves. Modern indoor dairy cattle housing systems often lack appropriate grooming substrates, restricting the animals' ability to groom. We assessed the motivation of dairy cows to access an automated mechanical brush, a grooming resource that can be implemented in indoor cattle housing systems. Cows were trained to push a weighted gate to access either fresh feed (positive control), a mechanical brush or the same space without a brush (negative control). Weight on the gate was gradually increased until all cows failed to open it. The weight each cow was willing to push to access each resource was assessed using the Kaplan-Meier survival analysis. Despite differences in methodology used to obtain data on motivation to access feed and the brush, the outcomes were very similar; cows worked as hard for access to fresh feed and the brush (p = 0.94) and less hard for access to the empty space (compared with fresh feed: p < 0.01; brush: p < 0.02). These results indicate that cows are highly motivated to access a mechanical brush and that it is an important resource for cows.

Forage choice in pasturelands: Influence on cattle foraging behavior and performance

We determined if combinations of adjacent pastures of 3 forage species led to complementary relationships that influenced animal behavior and performance over monocultures. Grazing bouts, behavioral levels of activity, blood urea N (BUN), chemical composition of feces, BW, and herbage biomass before and after grazing were monitored when beef calves strip-grazed 3 replications of 4 treatments from June 14 through August 23, 2013 (9 animals/treatment). Animals grazed monocultures of: 1) tall fescue (TF), 2) alfalfa (ALF), 3) sainfoin (SAN), or 4) a choice of strips of forages TF, ALF, and SAN (CHOICE). The lowest and greatest incidence of foraging bouts occurred for cattle in CHOICE and SAN, respectively (P < 0.01). Animals in CHOICE grazed SAN > ALF > TF (P < 0.01). Animals on TF and CHOICE took greater number of steps than animals grazing a monocultures of either legume (P = 0.01). Calves in TF had lower BUN (P < 0.01) and fecal CP concentration (P < 0.01) than calves grazing the remaining treatments, whereas animals in SAN showed the greatest concentrations of fecal CP (P < 0.01). Fecal NDF concentration was the greatest for animals grazing TF and the lowest for animals grazing SAN (P < 0.01), whereas fecal ADF concentration was greater for animals grazing TF and SAN than for animals grazing CHOICE and ALF (P = 0.02). Calcium, Mg, and Zn concentrations were the lowest in feces from calves grazing TF and the greatest for calves grazing a monoculture of either legume (P < 0.05). When averaging both periods, animals grazing SAN, ALF, or CHOICE gained more BW than animals grazing TF (P < 0.01). Thus, calves in CHOICE incorporated tall fescue into their diets, were more active, and displayed a lower number of grazing bouts than calves grazing monoculture of either legume. Herbage diversity may lead to levels of ADG comparable to legume monocultures with the potential benefit of maintaining plant species diversity in pasturelands.

Short communication: limit feeding affects behavior patterns and feeding motivation of dairy heifers

The study objective was to assess the effects of limit feeding dairy heifers on behavior patterns and feeding motivation. Ten Holstein heifers (291.6±39.2d of age, weighing 324.2±61.2kg; mean ± SD) were exposed to each of 2 dietary treatments, in a random order, over 2 successive 26-d treatment periods (14-d adaptation period and a 12-d data collection period) using a crossover design: (1) a high-forage total mixed ration (TMR), provided ad libitum (CON) and (2) a low-forage TMR, limit-fed at 2.05% body weight (LF). Heifers were fed daily at 1100h and motivation to access a low-nutritive feedstuff (straw) was assessed using a push-door apparatus at 2 time points: 3h after feed delivery (1400h) and 21h after feed delivery (0800h). The amount of weight pushed, weight pushed as percentage of body weight, and latency to access the push door were recorded on 3 different days for each heifer at each time point on each treatment. When fed CON, heifers had greater dry matter intake (12.9 vs. 7.2kg/d), greater feeding time (209.3 vs. 82.4min/d), greater ruminating time (452.2 vs. 318.3min/d), and slower rates of intake (0.06 vs. 0.09kg of dry matter/min) than when fed LF. Heifers fed LF pushed more weight as a percentage of body weight at 3h (4.5 vs. 1.9%) and 21h (9.3 vs. 2.8%) after feed delivery. At both 3 and 21h after feed delivery, latency to access the door was shorter for the LF heifers compared with the CON heifers (65 vs. 145 s). These results indicate that, in addition to decreasing feeding time, limit feeding increases motivation of heifers to access a low-nutritive feedstuff, possibly due to lack of satiety resulting from lack of physical fill or insufficient time spent foraging.

Measuring motivation for appetitive behaviour: food-restricted broiler breeder chickens cross a water barrier to forage in an area of wood shavings without food

Broiler breeders (parents of meat chickens) are selected for fast growth and become obese if fed ad libitum. To avoid this and maintain good health and reproductive ability, they are feed restricted to about 1/3 of what they would eat ad libitum. As a result, they experience chronic hunger and exhibit abnormal behaviour patterns that may indicate stress and frustration. One approach to measuring hunger is to observe how much birds will work, such as pecking a key, for access to more or different types of food. However, the sight, smell, and feedback from consumption of the feed reward changes the context and may artificially raise feeding motivation. To avoid this, we tested broiler breeders in an apparatus in which they could work for access to a wooden platform covered in wood shavings by crossing a water runway which increased in length and depth in 8 successive tests. In the wood shavings area, they could perform exploratory and foraging behaviour (the appetitive phase of feeding) but were never rewarded with feed. Sixty birds were divided into three feed quantity treatments: commercial restriction (R), and twice (2R) or three times (3R) this amount. Overall, birds fed R worked harder to reach the wood shavings area (reached it in a larger number of tests) than 2R and 3R birds (P<0.001). More restricted birds took less time to reach the area (P<0.001, R<2R<3R) and spent more time foraging while there (P<0.001, R>2R>3R). This indicates that restricted-fed birds were hungry and willing to work for the opportunity to forage even though food was never provided, suggesting that their motivation to perform the appetitive component of feeding behaviour (foraging/food searching) was sufficient to sustain their response. Thus food restriction in broiler breeders is a welfare concern. However these methods could be used to test alternative feeding regimes to attempt to find ways of alleviating hunger while still maintaining healthy growth and reproduction in these birds.

Are hungry sheep more pessimistic? The effects of food restriction on cognitive bias and the involvement of ghrelin in its regulation

Food restriction is considered to be a welfare issue in extensively reared animals. However, the effects of food restriction on the affective state, and its physiological regulation, are unknown. In Experiment 1, we aimed to assess the effects of increased plasma concentrations of acyl-ghrelin on judgement bias (an indicator of affective states) by fasting sheep for 24h or by ghrelin administration. In Experiment 2, we aimed to assess the effects of chronic food restriction on judgement bias and attention bias towards a food-related cue. For the judgement bias test, sheep were trained in an arena to approach a positive location cue associated with conspecifics and not approach a negative location cue associated with a dog. Three non-trained, non-reinforced ambiguous location cues were situated between the positive and negative locations. Attention bias towards a food-related cue was assessed by placing an empty food bucket against the wall of the arena halfway between the entry point and the positive location. In Experiment 1, sheep were divided into three treatments; 24h fast, ghrelin administration or control. Judgement bias, locomotor activity and plasma cortisol concentrations were assessed. The ghrelin treated group tended to express a more pessimistic bias compared to the control group (P<0.1), and plasma cortisol concentrations tended to be increased (P<0.1). In Experiment 2, sheep were subjected to a high feeding level (HF) or low feeding level (LF) for 7days. The LF group tended to show a more optimistic judgement bias (P<0.1). When the food-related cue was presented, LF ewes took longer to reach the positive location (P<0.001), spent longer with their head inside the bucket (P<0.001) and more time interacting with the bucket (P<0.01). This study provides preliminary evidence that food restriction alters judgement bias and attention bias towards a food-related cue which may indicate altered affective states of sheep.

The effect of food location, heat load, and intrusive medical procedures on brushing activity in dairy cows

Animals allocate time and effort to a range of core (e.g., sleeping, feeding, drinking) and "luxury" (e.g., playing, exploring) activities. A luxury activity is characterized by low resilience and, as such, will be reduced when time or energy resources are limited, including under conditions of stress or discomfort. One seemingly luxurious activity available to cows on an increasing number of dairy farms is rubbing against an automated brush. The current study examined the effect of distance from food, heat load, and an intrusive medical procedure (i.e., artificial insemination and transrectal pregnancy examination) on the resilience of brush usage. The probability of using the brush decreased significantly when food was located distantly from the brush (mean=0.53) compared with days when food was located closer to the brush (mean=0.81). Brush usage also decreased at high temperature and humidity levels, with an average decrease of 0.062 brushing events for an increase of 1 temperature-humidity index unit (95% confidence interval=-0.93-0.030). In addition, a significant reduction of approximately 50% in brushing activity was observed on days of artificial insemination compared with the preceding 3d and the following 3d. These findings show that brush usage is a low resilience activity that reduces under a range of conditions. It may thus have the potential to be used as an indicator of a range of health and welfare problems in cows. Further research should be conducted to assess the sensitivity and specificity of this suggested tool and its possible contribution to the early detection of morbidity.

Effects of dietary fibers with different fermentation characteristics on feeding motivation in adult female pigs

Dietary fibers can be fermented in the colon, resulting in production of short-chain fatty acids (SCFA) and secretion of satiety-related peptides. Fermentation characteristics (fermentation kinetics and SCFA-profile) differ between fibers and could impact their satiating potential. We investigated the effects of fibers with varying fermentation characteristics on feeding motivation in adult female pigs. Sixteen pair-housed pigs received four diets in four periods in a Latin square design. Starch from a control (C) diet was exchanged, based on gross energy, for inulin (INU), guar gum (GG), or retrograded tapioca starch (RS), each at a low (L) and a high (H) inclusion level. This resulted in a decreased metabolizable energy intake when feeding fiber diets as compared with the C diet. According to in vitro fermentation measurements, INU is rapidly fermentable and yields relatively high amounts of propionate, GG is moderately rapidly fermentable and yields relatively high amounts of acetate, and RS is slowly fermentable and yields relatively high amounts of butyrate. Feeding motivation was assessed using behavioral tests at 1h, 3h and 7h after the morning meal, and home pen behavioral observations throughout the day. The number of wheel turns paid for a food reward in an operant test was unaffected by diet. Pigs on H-diets ran 25% slower for a food reward in a runway test than pigs on L-diets, and showed less spontaneous physical activity and less stereotypic behavior in the hours before the afternoon meal, reflecting increased interprandial satiety. Reduced feeding motivation with increasing inclusion level was most pronounced for RS, as pigs decreased speed in the runway test and tended to have a lower voluntary food intake in an ad libitum food intake test when fed RS-H. In conclusion, increasing levels of fermentable fibers in the diet seemed to enhance satiety in adult pigs, despite a reduction in metabolizable energy supply. RS was the most satiating fiber, possibly due to its slow rate of fermentation and high production of butyrate.

Food sensory characteristics: their unconsidered roles in the feeding behaviour of domestic ruminants

When domestic ruminants are faced with food diversity, they can use pre-ingestive information (i.e. food sensory characteristics perceived by the animal before swallowing the food) and post-ingestive information (i.e. digestive and metabolic consequences, experienced by the animal after swallowing the food) to evaluate the food and make decisions to select a suitable diet. The concept of palatability is essential to understand how pre- and post-ingestive information are interrelated. It refers to the hedonic value of the food without any immediate effect of post-ingestive consequences and environmental factors, but with the influence of individual characteristics, such as animal's genetic background, internal state and previous experiences. In the literature, the post-ingestive consequences are commonly considered as the main force that influences feeding behaviour whereas food sensory characteristics are only used as discriminatory agents. This discriminatory role is indeed important for animals to be aware of their feeding environment, and ruminants are able to use their different senses either singly or in combination to discriminate between different foods. However, numerous studies on ruminants' feeding behaviour demonstrate that the role of food sensory characteristics has been underestimated or simplified; they could play at least two other roles. First, some sensory characteristics also possess a hedonic value which influences ruminants' intake, preferences and food learning independently of any immediate post-ingestive consequences. Further, diversity of food sensory characteristics has a hedonic value, as animals prefer an absence of monotony in food sensory characteristics at similar post-ingestive consequences. Second, some of these food sensory characteristics become an indicator of post-ingestive consequences after their initial hedonic value has acquired a positive or a negative value via previous individual food learning or evolutionary processes. These food sensory characteristics thus represent cues that could help ruminants to anticipate the post-ingestive consequences of a food and to improve their learning efficiency, especially in complex environments. This review then suggests that food sensory characteristics could be of importance to provide pleasure to animals, to increase palatability of a food and to help them learn in complex feeding situations which could improve animal welfare and productivity.

Motivation to obtain a food reward of pregnant ewes in negative energy balance: behavioural, metabolic and endocrine considerations

Low food availability often coincides with pregnancy in grazing animals. This study investigated how chronic reductions in food intake affected feeding motivation, and metabolic and endocrine parameters in pregnant sheep, which might be indicative of compromised welfare. Ewes with an initial Body Condition Score of 2.7±0.3 (BCS; 0 indicates emaciation and 5 obesity) were fed to attain low (LBC 2.0±0.0,), medium (MBC 2.9±0.1) or high BCS (HBC 3.7±0.1) in the first trimester of pregnancy. A feeding motivation test in which sheep were required to walk a set distance for a palatable food reward was conducted in the second trimester. LBC and MBC ewes consumed more rewards (P=0.001) and displayed a higher expenditure (P=0.02) than HBC ewes, LBC ewes also tended to consume more rewards than MBC ewes (P=0.09). Plasma leptin and glucose concentrations were inversely correlated to expenditure (both P<0.05) and appear to be associated with hunger in sheep. LBC ewes were in negative energy balance, with lower muscle dimensions, plasma glucose, leptin, insulin, cortisol, and insulin-like growth factor-1 concentrations and higher free fatty acids concentrations compared to HBC ewes; metabolic and endocrine parameters of the MBC ewes were intermediate. The high feeding motivation and negative energy balance of low BCS ewes suggested an increased risk of compromised welfare. Imposing even a small cost on a food reward reduced motivation substantially in high BCS ewes (despite high intake when food was freely available). Assessment of a willingness to work for rewards, combined with measures of key metabolic and endocrine parameters, may provide sensitive barometers of welfare in energetically-taxed animals.