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 (P2R>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

Body fatness affects feed intake of sheep at a given body weight

In a 1-yr experiment, nutritional treatments were used to produce different combinations of BW and BCS in lambs. The experiment served to quantify the effects of BW and BCS on ADFI by sheep. Ewe lambs (n = 78) were assigned to treatment groups that had ad libitum access to one feed at a time. Three feeds were used: a medium-quality chopped hay (L), a pelleted feed based on oat feed (M), and a pelleted feed based on barley (H). Three groups received only one of these feeds throughout. Two groups first received H and then were switched to M when they reached a BW of 45 or 65 kg. Two groups first received L and then were switched to M or H after reaching a BW of 45 kg. Three groups first received H or M but were switched to L after reaching a BW of 45, 65, or 95 kg. Daily feed intake, BW, and BCS were recorded, and ME content of the feeds was estimated in a separate digestibility experiment. The lambs consuming M ate more (P < 0.001) feed than lambs consuming H, but this had no significant effects on ME intake or gain in BW or BCS. Animals that had had access to L were lean for their BW when switched to H or M and showed compensatory intake and gain. Animals switched from M or H to L all lost BCS; BW change depended on the BW at the switch. The treatments produced different combinations of BW and BCS for animals with access to the same feed. The ADFI of a given feed varied systematically with BCS for animals of a given BW. The model ADFI = a x BW x [1 - (b x BCS)] gave a reasonable description of the data in all treatments. A model using BW, BCS, and their interaction gave a slightly better fit but explained little more of the variation in ADFI than the simpler model. The implications of the collected data are that BW alone is an insufficient descriptor of the animal to correctly predict feed intake and that intake predictions can be improved by taking BCS into account

A novel flexible method to split feeding behaviour into bouts

Before meal patterns can be analysed properly, a biologically relevant meal criterion must be determined in order to group short-term feeding behaviour into meals. Existing methodologies are based on modelling of the frequency distributions of intervals between feeding events but these methods cannot be used if the proper distributions cannot be clearly identified. For such cases we developed two new methods - (1) based on the analysis of the distribution of between-meal interval lengths only and (2) based on the analysis of changes in the probability of animals starting to feed with time since the last feeding event. Both methods were developed using a data set of over 700,000 records of visits to feeders obtained with broilers (Gallus gallus) aged between 2 and 5 weeks. The two methods resulted in meal criteria estimates of 20.1 and 17.5 min, respectively, which, when applied to the data set, gave statistically significant but Very small differences in meal characteristics. The new methods were tested against an independent cow (Bos taurus) data set and the resultant meal criteria compared with those predicted by an existing method. The two novel methods estimated meal criteria for cows at 27.9 and 35.5 min, compared with 28.9 min for the existing method. Again, these differences in meal criteria resulted in only very small differences in meal characteristics. Even though meal criteria were relatively similar for birds and cows, characteristics such as average daily number of meals (10.9 and 5.9). meal size (12.5 g and 7.4 kg) and meal duration (7.7 and 31.4 min) were very different. The analyses show that, if the appropriate distributions of intervals cannot be identified, meal criteria can still be estimated for species as diverse as mature cows and young birds by the novel methodologies developed here. (C) 2008 Elsevier B.V. All rights reserved

'Freedom from hunger' and preventing obesity: the animal welfare implications of reducing food quantity or quality

In animals, including humans, free access to high-quality (generally energy-dense) food can result in obesity, leading to physiological and health problems. Consequently, various captive animals, including laboratory and companion animals and certain farm animals, are often kept on a restricted diet. Quantitative restriction of food is associated with signs of hunger such as increases in feeding motivation, activity and redirected oral behaviours which may develop into stereotypies. An alternative approach to energy intake restriction is to provide more food, but of a reduced quality. Such alternative diets are usually high in fibre and have lower energy density. The benefits of these alternative diets for animals are controversial: some authors argue that they result in more normal feeding behaviour, promote satiety and so improve animal welfare; others argue that 'metabolic hunger' remains no matter how the restriction of energy intake and weight gain is achieved. We discuss the different arguments behind this controversy, focusing on two well-researched cases of food-restricted farmed livestock: pregnant sows and broiler breeders. Disagreement between experts results from differences in assumptions about what determines and controls feeding behaviour and food intake, from the methodology of assessing animal hunger and from the weighting placed on 'naturalness' of behaviour as a determinant of welfare. Problems with commonly used behavioural and physiological measures of hunger are discussed. Future research into animal feeding preferences, in particular the relative weight placed on food quantity and quality, would be valuable, alongside more fundamental research into the changes in feeding physiology associated with alternative diets. (C) 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved

Effects of maternal protein nutrition and subsequent grazing on chicory (Cichorium intybus) on parasitism and performance of lambs

Forty-eight 4- to 5-yr-old Blackface x Bluefaced Leicester (Mule) ewes and their 24-d-old twin lambs were used to assess the effects of maternal protein nutrition and subsequent grazing on chicory (Cichorium intybus) on performance and parasitism. The experiment consisted of 2 grazing periods: safe pasture period and experimental pasture period. During an adaptation period of 66 d, ewes were infected through oral dosing with Teladorsagia circumcincta infective larvae (3 d per wk) and were supplemented with protein (HP) or not (LP) for the last 45 d of this period. At the end of this period, ewes and their lambs were turned out onto a parasitologically safe pasture; all ewes continued to be dosed with parasite (once a week), and HP ewes received protein supplementation for the first 35 d. Ewes and lambs grazed the safe pasture for an additional 43 d after termination of protein supplementation and of oral dosing with parasites. Ewes and their lambs were then moved onto newly established experimental pastures sown with chicory or grass/clover (Lolium perenne/Trifolium repens). During the safe pasture period, HP ewes had decreased fecal egg counts (FEC) compared with LP ewes, whereas HP lambs had temporarily less (P 0.10) between maternal nutrition and grazed forage type on performance or parasitological measurements. Our results suggest that increased maternal protein nutrition and subsequent grazing of chicory independently improve lamb performance and reduce lamb parasitism