Frank Tuyttens

Stocking density effects on broiler welfare: Identifying sensitive ranges for different indicators

Although stocking density is perceived as a topic of major importance, no consensus has been reached on what density would allow for good welfare. In the present study, the welfare of 4 replicates of birds stocked at 8, 19, 29, 40, 45, 51, 61, and 72 broilers per pen (or 6, 15, 23, 33, 35, 41, 47, and 56 kg actually achieved BW/m(2)) was studied using 6 welfare indicators. Density did not affect bursa weight, mortality, or concentrations of corticosterone metabolites in droppings but did influence leg health (P = 0.015) and footpad and hock dermatitis (P < 0.001) and tended to influence fearfulness (P = 0.078). However, not every increase in density or group size, or both, led to poorer welfare for the affected indicators: leg health and fearfulness showed unexpected peaks at intermediate densities. Furthermore, the indicators were influenced at different densities: leg strength showed a steep decrease from 6 to 23 kg/m(2), hock dermatitis rose from 35 to 56 kg/m(2), and footpad dermatitis and fearfulness were only significantly higher at the highest density of 56 kg/m(2). No threshold stocking density above which all aspects of welfare were suddenly altered was found in this study. Instead, different aspects of welfare were influenced at different densities or group sizes, or both. Thus, evaluating the effects of stocking density on welfare as a whole would require either identification of acceptable levels for each separate indicator or a weighting of the indicators in an integrated welfare score. A tentative attempt to such an integration, made using equal weights for all parameters, showed a decrease in welfare as density increased (P < 0.001). The lowest 2 densities (6 and 15 kg/m(2)) scored better than most middle densities (23, 33, 35, and 47 kg/m(2)), whereas all densities scored better than the highest density (56 kg/m(2)).

Fluctuating asymmetry as an animal welfare indicator : A review of methodology and validity

It has been suggested that fluctuating asymmetry (FA) reflects an animals ability to cope with the sum of challenges during its growing period and, thus, is a potential welfare indicator. In this review we investigate the evidence of associations between FA and other welfare indicators measured at the level of the individual and of effects of welfare-relevant environmental conditions on FA in populations of captive birds and mammals including humans. As the question of validity cannot be treated independently from the quality of the available data, first a checklist for the proper measurement and analysis of FA is drafted and used to evaluate the methodological quality of the various studies. We recommend this checklist to be used as a standard for future FA studies. We found 17 relevant studies on associations between FA and other welfare indicators, and 36 studies on effects of welfare-relevant factors on FA. Frequent methodological shortcomings or insufficient methodological information allow for only cautious conclusions. The proportion of significant results supporting the link between higher FA and poorer welfare is only moderately high. Independent from statistical significance, almost all studies found the relationship between FA and welfare to be prevailingly in the expected direction. FA is a promising measure of animal welfare, despite a great number of open questions, e.g. relating to the ontogeny of FA or its sensitivity to various stressors. The considerable potential of FA as a welfare indicator makes it worthwhile to pursue more intensely validation studies as well as applied studies. These studies should pay particular attention to an appropriate methodological approach.

Welfare, Health, and Hygiene of Laying Hens Housed in Furnished Cages and in Alternative Housing Systems

The aim of this review was to compare welfare, health, and hygienic status of laying hens housed in furnished cages and in alternative systems. In alternative systems (floor housing and aviaries), birds have more freedom of movement and a more complex environment than in furnished cages. However, housing birds in much larger flocks in alternative systems leads to an increased risk of feather-pecking. Furthermore, air quality can be poorer in alternative systems than in furnished cages. This can affect health and hygienic status. There are only limited data on a direct comparison between furnished cages and alternative systems. Therefore, there is a need for an on-farm comparison of welfare, health, and hygienic status in these systems.

Design of laying nests in furnished cages: influence of nesting material, nest box position and seclusion

1. Preferences for three nesting materials and nest box positions were investigated simultaneously in two trials using a furnished cage: one with 18 individual laying hens and one with 18 groups of 5 hens. Following a habituation period in pre-test cages, every hen or group of hens was tested for 2 d: once without and once with plastic flaps at the entrance of the nest boxes. 2. Hens preferred peat and artificial turf to coated wire mesh for egg laying. 3. One nest box position was clearly preferred to both other nest boxes. The hens’ choice of nest box position was influenced by the pre-test cage in which they had been habituated. 4. The presence of plastic flaps at the entrance of the nest boxes had no influence on the proportion of eggs laid on the different nesting materials or on the proportion of floor eggs. 5. Individual and group testing resulted in the same overall results despite the presence of a distinct group effect.

Absence of an effect of dietary fibre or clinoptilolite on boar taint in entire male pigs fed practical diets

This study aimed to evaluate the possibility of reducing boar taint in boars (Piétrain×Hybrid) by addition of different feed ingredients (raw potato starch (RPS) 10%, raw potato starch 10%+wheat bran 5% (RPS+WB), lupins 10%, inulin 5%, clinoptilolite 1%) to a standard diet over a period of 4-6 weeks before slaughter. Control boars (CBOAR) as well as barrows were fed the standard diet. Efficacy of the different feed ingredients was evaluated by different boar taint detection methods: hot iron method, consumer panel, expert panel and laboratory analysis. According to all detection methods, clear differences were noticeable between boars and barrows. No differences in boar taint incidence were found between the boars on the different dietary treatments as assessed by consumers, experts, hot iron method or the concentration of skatole in fat. A significant effect on indole level was found, but no further differentiation could be made. The concentration of backfat androstenone was significantly higher for the inulin and control boar group compared to the lupin group. In conclusion, none of the feeding strategies tested in this study reduced boar taint in boars at the given percentages.

Bacteriological contamination, dirt, and cracks of eggshells in furnished cages and noncage systems for laying hens: An international on-farm comparison

For laying hens, the effects of housing system on bacterial eggshell contamination and eggshell quality is almost exclusively studied in experimental hen houses. The aim of this study was to compare eggshell hygiene and quality under commercial conditions. Six flocks of laying hens in furnished cages and 7 flocks in noncage systems were visited when hens were about 60 wk of age. Farms from Belgium, the Netherlands, and Germany were included in the study. The following parameters were determined on eggs sampled at the egg belts: 1) bacterial eggshell contamination, as expressed by total count of aerobic bacteria and number of Enterobacteriaceae; 2) proportion of dirty eggs; and 3) proportion of cracked eggs and eggs with microcracks. Considerable within-flock differences were found in eggshell contamination with total count of aerobic bacteria, both for furnished cages (P < or = 0.001, range 4.24 to 5.22 log cfu/eggshell) and noncage systems (P < or = 0.001, range 4.35 to 5.51 log cfu/eggshell). On average, lower levels of contamination with total count of aerobic bacteria (4.75 vs. 4.98 log cfu/eggshell; P < or = 0.001) were found on eggshells from furnished cages compared with noncage systems. Concerning Enterobacteriaceae, no significant difference in average eggshell contamination between both systems could be shown. The total percentage of cracked eggs was higher (P < or = 0.01) in furnished cages (7.8%) compared with noncage systems (4.1%). This was, however, due to the high percentage of cracked eggs (24%) observed on one of the furnished cage farms. We conclude that bacteriological eggshell contamination and percentage of cracked eggs differed substantially between individual farms using the same housing system. This may also explain some discrepancies between the findings of the present study versus some findings of previous experimental studies or studies on a small number of farms. Although statistically significant, the average differences in bacteriological contamination of nest eggs between both housing systems have limited microbiological relevancy.

Effect of surgical castration, immunocastration and chicory-diet on the meat quality and palatability of boars

This study evaluates 1) carcass quality, meat quality and palatability for barrows, immunocastrates and boars and 2) the effect of chicory supplemented feed during 10 days before slaughter on boar meat quality. At comparable carcass weights, estimated carcass lean meat percentage was higher in immunocastrates and boars than in barrows. Muscle thickness was higher for immunocastrates and barrows compared to boars, while fat thickness was lowest for immunocastrates and boars. Barrows, immunocastrates and boars differed in water holding capacity and boar taint. Home consumer panels were conducted to evaluate palatability. The consumers did detect differences in tenderness and juiciness, but not for boar taint. The chicory feed supplemented in boar feed decreased skatole concentration in backfat, without largely influencing meat quality or palatability. Not only boar taint, but also carcass and meat quality should be considered when evaluating alternatives for surgical castration.

Influence of breed and slaughter weight on boar taint prevalence in entire male pigs.

Piétrain (P), Large White (LW) and Belgian Landrace stress negative (BN) boars were slaughtered at 50, 70, 90 or 110 kg live weight to investigate breed differences and the effect of slaughter weight on boar taint prevalence. Boar taint was quantified by four different methodologies: sensory evaluation of neckfat heated with a hot iron in the slaughterhouse, sensory evaluation of meat by consumer panels, sensory evaluation of fat and meat by expert panels and laboratory analysis of indole, skatole and androstenone in backfat. Skatole levels in backfat were significantly higher for LW and BN than for P boars. The androstenone levels and the hot iron method revealed a significant interaction between breed and slaughter weight. On the other hand, experts detected an effect of weight on the androstenone odour perception, which was significantly higher in fat from boars slaughtered at 90 kg compared with 50 kg, and significantly higher in meat from boars slaughtered at 110 kg compared with 50 kg. Consumers did not detect differences in the sensory characteristics among breeds or slaughter weight. These results indicate opportunities to minimise the risk of boar taint in entire male pigs by carefully selecting a combination of breed and slaughter weight. Along with the optimal slaughter weight, the effectiveness of reducing boar taint by lowering slaughter weight appeared to be breed dependent.

Perching behaviour and perch height preference of laying hens in furnished cages varying in height.

1. The objective was to investigate the effect of cage height on perch height preference and perching behaviour in laying hens. Twelve groups of two hens and 12 groups of 14 hens were tested in furnished cages equipped with two wooden perches. These stepwise perches were designed such that hens could choose between 7 different heights (6, 11, 16, 21, 26, 31 and 36 cm). Day- and night-time perching behaviour was observed on 4 consecutive days with a different cage height each day: 150, 55, 50 and 45 cm. 2. Given that a minimum perch–roof distance of 19 to 24 cm was available, hens preferred to roost on the highest perches at night. 3. Lowering cage height not only forced hens to use lower perches, but also reduced time spent on the perches during the day (two-hen and 14-hen test) and night (14-hen test). Moreover, it affected daytime behavioural activities (more standing and less preening) on the perches in the two-hen tests (but not in the 14-hen tests). 4. During the day lower perches were used more for standing and walking, higher perches more for sitting and sleeping. This behavioural differentiation was most pronounced in the highest cages. 5. Perch preference and perching behaviour depend on both the floor–perch distance and the perch–roof distance. Higher cages provide more opportunity for higher perches (which hens prefer), for better three-dimensional spacing (and consequently reduced density at floor level) and for behavioural differentiation according to perch height.

A validated ultra-high performance liquid chromatography coupled to high resolution mass spectrometry analysis for the simultaneous quantification of the three known boar taint compounds.

Boar taint is an off-odour that can occur when meat or fat from entire male pigs is heated. Most of the currently available analytical methods are not capable of detecting the three known boar taint compounds (indole, skatole and androstenone) simultaneously, which renders their analysis often labour-intensive and time-consuming as separate analyses are required. In this study a validated U-HPLC-HR-Orbitrap-MS analysis method is described for the quantitative determination of the three boar taint compounds in fat. The sample pre-treatment involves a melting step followed by extraction with methanol and clean-up consisting of a freezing step and solid phase extraction (HLB cartridges). The analytes are then chromatographically separated and detected with an Exactive high-resolution mass spectrometer. Due to the absence of guidelines for the analysis of boar taint in fat, the Commission Decision 2002/657/EC [18] and ISO 17025 [19] guidelines were used as guideline for validation of the developed detection method. This resulted in limits of detection and limits of quantification between 2.5 and 7 μg kg(-1) and between 5 and 10 μg kg(-1) for the three compounds, respectively, which is far below the threshold values set at 100 μg L(-1) for indole, 200 μg L(-1) for skatole and 1000 μg L(-1) for androstenone in pig fat samples. The method obtained for the three compounds a repeatability (RSD) lower then 12.7% and a within-laboratory reproducibility (RSD) lower than 16.9%. The recovery of the three compounds ranged between 99 and 112 and an excellent linearity (R(2) ≥ 0.99) was found. In the future, this method may be extended with other compounds that turn out to be correlated with boar taint.