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Effect of Supplemental Roughage on Behavior, Physiological Stress Response, and Egg Production Parameters of Farmed Partridges (Perdix perdix)

J. B. Kjaer^*,1 and B. K. Hansen

^* Federal Agricultural Research Centre, Institute for Animal Welfare and Animal Husbandry, D-29223 Celle, Germany; and University of Aarhus, Faculty of Agricultural Sciences, Institute of Genetics and Biotechnology, DK-8830 Tjele, Denmark

¹ Corresponding author: joergen.kjaer{at}fal.de

	ABSTRACT

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The objective of the present experiment was to test the hypothesis that supplemental feeding of roughages (maize silage, rucola salad, or wheat sprouts) would reduce behavioral and physiological signs of stress and increase egg production. A total of 160 adult partridge breeder birds were housed in pairs of 1 male and 1 female/cage during the egg-laying period from April to June. Birds fed on maize silage spent more time laying and less time foraging than birds in the wheat sprout treatment (P < 0.05). Birds fed wheat sprouts were more active than control birds (active 57 vs. 43% of the time, P < 0.05). Birds on the western side of the shed spent more time eating (3.9 vs. 1.24%, P < 0.01). Aggression and dustbathing were rarely seen, and feather pecking was never observed. The basal level of corticosterone (SD) was, on average, 11.4 (6.0) ng/mL of plasma and was not affected by treatments. After 15 min of crating, the average level of corticosterone was 50.0 (20.5) ng/mL of plasma, and strongly tended (P = 0.066) to be higher in the birds on the wheat sprout treatment compared with those on the control or other treatments. Fewer eggs (P < 0.05) were produced by birds on the wheat sprout treatment compared with those on the control treatment (on average, 45.9 vs. 52.1 eggs in total and 40.9 vs. 47.3 eggs for setting). Treatments did not affect egg fertility, egg hatchability, or the number of hatched chicks. In conclusion, we cannot recommend supplementing partridge diets with wheat sprouts during the egg-laying period because this seems to cause behavioral and physiological stress responses and impaired egg production. In general, partridge breeders in the production system investigated here did not show overt signs of maladaptive behavior or physiological stress when fed pelleted concentrate only or concentrate with supplements of maize silage or fresh rucola salad.

Key Words: environmental enrichment • foraging behavior • game bird • nutritional stress • welfare

	INTRODUCTION

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There is a growing concern in many countries about the welfare of animals used by humans. In the commercial production of game birds in Northern Europe, the major species are the gray-legged partridge (referred to here as the partridge, Perdix perdix), the red-legged partridge (Alectoris rufa), and the common pheasant (Phasianus colchicus). The main welfare problems of these species are related to abnormal behavior, such as feather pecking and cannibalism (Swarbrick, 1985). Pheasant (P. colchicus) chicks in particular are reported to be prone to feather pecking (e.g., Kjaer, 2004). The problem exists in young partridges as well (J. B. Kjaer, unpublished data). Adult partridges are often kept in pairs in specific breeder cages during the breeding season. The natural feeding behavior of the partridge before the onset of incubation consists of extensive exploration in a diurnal fashion (Dowell, 1990) for seeds of weeds and insects of various kinds in a variable farming landscape (Steenfeldt et al., 1991). The partridge breeder cages most commonly used in commercial partridge egg production in Denmark are relatively barren and the feed is a pelleted ration containing all the required nutrients. We therefore hypothesized that adult partridges would show physiological and behavioral signs of stress in this barren environment (e.g., higher hypothalamic-pituitary-adrenal axis reactivity, feather pecking, and extensive pacing) not seen among free-living partridges. Furthermore, we expected that supplementation of fresh roughage would reduce these signs of stress. Because supplementation of roughage to laying hens can affect egg production and consumption of feed concentrate (Steenfeldt et al., 2007), we measured these variables as well.

	MATERIALS AND METHODS

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Experimental Design
The experiment was carried out in cooperation with professional gamekeepers (Duelund Game Farm, Kjellerup, Denmark). A total of 160 adult partridges were set up in 80 breeder pairs in early February. This gave 20 pairs (replications) distributed randomly to each of 4 treatments: the control, without supplementation of roughage; maize silage; fresh rucola salad; or wheat sprouts. Maize silage, based on the whole plant cut, was brought from a local cattle farm 3 times. The silage was stored in a refrigerator until use. Rucola salad from the local supermarket was supplied on a weekly basis. Wheat sprouts were made regularly on the farm in batches from 5 kg of grain.

Animals, Housing, and Management
The birds were kept over winter in floor pens holding 100 to 200 birds, with access to an outdoor run with a sand bottom. In early February, the cocks and hens were paired at random and placed in cages in semiopen sheds. The cages measured 150 x 45 x 53 cm (length, width, height). The floor consisted partly (67%) of wire flooring (1 x 0.5 in., plastic coated) and partly of wood. The wooden area was 8 cm lower than the wire floor, had 8-cm-high sides around it, and was covered by an approximately 5-cm-deep layer of sand. A feeder was placed at the wall in the part with the wooden floor. The feeder could hold approximately 2 kg of pelleted feed mix. A commercial feed mixture (Hornsyld Koebmandsgaard, Hornsyld, Denmark) having 23.0% CP and 2,795 kcal (11.7 MJ) of ME/kg was used. The main ingredients in this mixture were 20% maize, 17 to 19% wheat, 6% oats, 6% barley, 24 to 28% soybean meal, 1 to 2% sunflower seed meal, 4% fish meal, 6% grass pellets, 1.5% soybean oil, and 1% molasses. In the wire-floored area, water was available from a nipple drinker. Feed and water were available ad libitum. Natural daylight was supplemented with artificial light. On February 1, the day length was increased by 2 h and 10 min in the evening (sunset at 1650 h, artificial light ending at 1900 h). Every other day, light was supplied for 15 min longer. Beginning on February 9, artificial light was also supplied in the morning (sunrise 0750 h, light supplied from 0730 h). Every other day, light was supplied 15 min earlier.

At total of 80 pairs of birds were used in the experiment. Beginning on April 1, the birds in the maize silage treatment (20 pairs) were supplemented with a handful (approximately 50 g/pair per day) of maize silage at 0800 h every morning. At the same time of day, the 20 pairs in the wheat sprout treatment received a handful of fresh wheat sprouts (approximately 50 g), whereas the 20 pairs in the rucola salad treatment received a handful of green rucola salad, approximately 20 g/pair. The distribution of treatments was balanced over the shed in blocks of 5 cages. Twenty pairs received no roughage (control treatment).

Data Collection
Behavior.
Behavior recordings were made in the last week of May, 8 wk after initiating roughage feeding. Only cages with the same treatment as in the neighboring cages (12 pairs/treatment) were included in the behavioral investigations. To avoid disturbing the birds while recording behavior, a video camera was used to transmit a live signal to a video monitor placed at a distance. From this monitor, behavior was recorded using a focal bird behavior sampling technique. One bird of the pair was chosen at random and time budgets were recorded for 15 min in the morning and 15 min in the afternoon. Observations were balanced over treatments, time of day, and age. The following ethogram was used: lying, standing, moving forward, foraging (moving forward while pecking the ground), eating, and drinking. The number of dustbaths (including at least 1 vertical wing shake), the number of aggressive pecks (fast pecking toward the head, forcing the receiver to escape or fight), and the number of feather pecks (pecks of a nonaggressive kind to the plumage of another bird) were recorded. Two variables were calculated based on a collation of behaviors: "passive behavior" (the sum of lying and standing behavior), and "active behavior" (the sum of moving, eating, drinking, foraging, aggressive pecking, and dustbathing behavior).

Stress Physiology.
The test of adrenal responsiveness was made after the behavioral observations were completed at approximately 10 wk after treatment initiation. The catcher entered the shed and caught a predefined bird with a small net. The bird was carried by hand to the place of blood sampling just outside the shed. On average, this part of the procedure took less than 1 min. The bird was held by a helper, and the first blood sample was drawn as fast as possible with a 2-mL syringe from the wing vein and immediately transferred to lithium-heparin-coated centrifuge tubes (Vacuvette 2 mL, Greiner Bio-One, Frickenhausen, Germany) stored on ice until further processing. The bird was then placed into a transport crate measuring 30 x 30 x 10 cm (length, width, height). The crate was lightproof except on one of the sides (10 x 30 cm), which was covered with wire mesh. A second blood sample was taken from the vein of the other wing after precisely 15 min in the crate and treated like the first sample. Blood was centrifuged for 10 min at 2,000 x g at a temperature of 4°C. Plasma samples were transferred to Eppendorf cups and 10 µL of natrium azide was added. Samples were stored in –21°C until analysis. Plasma corticosterone levels were measured in duplicate using a specific RIA (Etches, 1976). Calculations of the RIA were performed using the RIASmart program (Packard Instrument Co., Canberra, Australia).

Egg Production and Feed Consumption.
Eggs were collected by hand every morning and carried in egg baskets to the egg sorting and storage room, where they were stored at 10 to 15°C until incubation. The total number of eggs was recorded per pair of birds on a daily basis. The number of cracked eggs and eggs with pinholes or other damage was recorded per pair of birds on a 21-d (first collection) or 14-d (subsequent 3 collections) basis. The amount of feed concentrate was recorded for each pair when feeders were filled. Feed spillage was minimal. The feed value of the roughages was not included in the calculation of feed conversion.

Incubation and Hatching.
The eggs were incubated in 4 batches after a 21-d (first hatch) or 14-d (subsequent 4 hatches) collection period. The eggs were in the incubator (type I72, Victoria, Guanzate, Italy) for 21 d at a temperature of 36 to 37°C and RH of 47%. The eggs were transferred to the hatcher (type H24, Victoria) for the last 4 d. Eggs were candled after 14 d of incubation and infertile eggs were removed. The number of eggs for incubation, infertile eggs, and hatched chicks was recorded per pair of birds per hatch.

Statistical Analyses
Data were subjected to ANOVA using the GLM procedure of the SAS statistical package, version 8.1 (SAS Inst. Inc., Cary, NC). The initial model included treatment, block (side of the shed, west or east), and their interaction as fixed effects. Nonsignificant effects were removed from the model stepwise. The behavior variables were log transformed to obtain normality and homogeneity of variance. For production traits, the continuous variable, days in production, was included in the model to correct for a very variable date of first egg.

	RESULTS

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Behavior
In general, the time budgets were influenced very little by treatments (Table 1). The average time budget across treatments can be seen in Figure 1. Birds fed maize silage spent more time lying and less time foraging than birds in the wheat sprout treatment (Table 1). Birds in the wheat sprout treatment were more active than control birds (active 57 vs. 43% of the time, P < 0.05). Birds on the western side of the shed spent more time eating (3.9 vs. 1.24%, P < 0.01). Aggressive behavior was observed in only 1 pair of birds, and dustbathing was observed in 5 pairs. Feather pecking was never observed.

View larger version (24K): [in this window] [in a new window]   Figure 1. Time budget (mean percentage of observation time) spent in various behaviors by partridge breeders kept in modified layer cages; average over all treatments.

View larger version (42K): [in this window] [in a new window]   Figure 2. Basal plasma corticosterone level (ng/mL of plasma ± SE) in partridge breeders kept in modified layer cages fed concentrate only (control) or concentrate supplemented with maize silage, rucola salad, or wheat sprouts.

View larger version (45K): [in this window] [in a new window]   Figure 3. Plasma corticosterone level (ng/mL of plasma ± SE) after stress (15 min of crating) in partridge breeders kept in modified layer cages fed concentrate only (control) or concentrate supplemented with maize silage, rucola salad, or wheat sprouts. The average level of corticosterone tended to be higher in birds in the wheat sprout treatment compared to the control and other treatments. The level of corticosterone in birds from the wheat sprout treatment differed significantly (P < 0.05) from those of birds in the maize silage and rucola salad treatments, respectively.

Feed Consumption.
Birds fed wheat sprouts ate significantly less concentrate than birds in the other treatments, and birds on the rucola salad treatment ate less than control birds during the course of the experiment (Table 2). When correcting for egg production, birds in the wheat sprout treatment ate 109 g/egg, whereas those in the control treatment ate 123 g/egg. Because of the large SE, this difference was not statistically significant. Birds on the west side of the shed ate significantly more than birds on the east side (5,542 vs. 5,278 g, P < 0.05). This was not reflected in the feed consumption per egg produced, which was, on average, 117 g.

	DISCUSSION

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Feeding roughage was expected to increase the time spent foraging, as seen in domestic hens (Steenfeldt et al., 2007), but this was not the case in the present experiment. Either the sand-littered area fulfilled the need for foraging substrate, or the amount of roughage offered increased foraging only for a short period in the morning and not enough to influence the average daily time budget significantly. In any case, the behavioral activation induced by feeding roughage was too small to be detected in general, whereas a specific effect was seen in the wheat sprout treatment. This result is discussed below in relation to stress reactivity.

Contrary to our expectation, the partridges showed no overt behavioral signs of stress, either active (e.g., pacing or escape behavior, jumping to the roof, etc.) or passive (e.g., excessive lying or crouching). We were unable to find literature presenting the time budgets of partridge breeders during the egg-laying period when kept in cages. Unlike domestic caged hens (Anderson et al., 2004) and common pheasants kept in small groups in floor pens (Pulliainen, 1965; J. B. Kjaer, unpublished data) during the egg-laying period, very low levels of aggression were recorded in the present experiment, and feather pecking was not recorded at all.

The hypothesis of reducing stress reactivity by feeding roughage could not be supported by the results. On the contrary, there was a clear tendency for higher stress reactivity in the wheat sprout treatment, which, in conjunction with the higher locomotor activity seen in these birds, indicates elevated chronic stress. A possible nutritional explanation for these effects is that wheat sprouts contain a high amount of antioxidants (reducing chemicals), among others ascorbic acid (Calzuola et al., 2004). The effect of ascorbic acid levels on physiological variables of behavior and stress is not straightforward. Ascorbic acid is an antioxidant that can be synthesized by chickens (Pardue and Thaxton, 1986) and is closely associated with corticosterone production. It is found in high concentrations in the adrenal and inhibits steroid genesis by inhibiting side-chain cleavage of cholesterol and the actions of hydroxylases (Whitehead and Keller, 2003). Maintaining high adrenal concentrations of ascorbic acid has been found to limit the rise in circulating corticosterone levels in chickens under stress (Pardue and Thaxton, 1986). However, a tendency toward the opposite, higher corticosterone levels in response to a stressor (crating for 15 min), was found in the wheat sprout treatment in the present study. This might be due to the level of ascorbic acid being too low in the adrenals to show this limiting effect on corticosterone. Supplementation of vitamin C reduces fearfulness in quail (Jones et al., 1999) and broiler chickens (Satterlee et al., 1994). The mechanisms of action seem to be through multiple pathways, such as the dopaminergic, cholinergic, -aminobutyric acid-ergic, serotonergic, and glutamatergic transmission mechanisms (Rebec and Pierce, 1994). These authors found that the action of ascorbate is dose dependent such that low doses enhance and high doses antagonize dopamine-mediated behavioral effects, thus resulting in behavioral activation or immobility, respectively.

Contrary to our expectations, feeding roughages did not influence the basal levels of corticosterone and, as discussed above, a tendency was found for higher corticosterone response to a stressor (crating) in the wheat sprout treatment. However, this result corresponded well with the behavioral observations as well as egg production parameters. Although no significant differences were found in egg production, a tendency toward lower egg production in the wheat sprout treatment was found, adding to the picture of some kind of nutritional stress in this treatment. Furthermore, the feed concentrate intake was lower in the wheat sprout treatment, which might have influenced corticosterone levels, because these have been seen to increase in fasting birds (Whitehead and Keller, 2003). We were unable to find published values for basal corticosterone or adrenal reactivity in partridges, but compared with other species, the levels were approximately twice those reported in Japanese quail (Hazard et al., 2005). Guémené et al. (2002) found basal corticosterone levels in male domestic chickens of approximately 3 to 4 ng/mL, and after 15 min of restraint, approximately 7 ng/mL.

Total egg production in the present study (between 45 and 52 eggs/pair in 76 d of production) was lower than that of an Italian population kept under comparable conditions over many years and laying, on average, 58 eggs/ pair in a laying period of 75 d in their first year (Bagliacca et al., 2004). Thompson et al. (1992) reported a lower productivity (39 eggs/pair) in birds originating from the same stock as that of the present study, but approximately 20 generations (years) earlier (1986) and kept in Illinois. The discrepancies could be due to differences in environmental conditions (e.g., climatic, day length, etc.). Alternatively, the breeding technology used (artificial incubation) might have induced indirect selection for higher productivity, as shown by Bagliacca et al. (2004). In their study using the Italian population referred to above, 6 generations of reproduction using only natural brooding, unlike the normal artificial brooding, lowered production significantly, from 58 to 46 eggs/pair. Fertility (86 to 88%) was very close to that presented by Bagliacca et al. (2004; 87%), whereas hatchability of fertile eggs was somewhat lower in the present study (65 vs. 89%). The corresponding figures for the 1986-generation birds kept in Illinois were 77 and 78%, respectively (Thompson et al., 1992). The numbers of hatched chicks per pair were 25 to 29 in the present study, whereas the Italian strain produced 44 chicks/pair in their first year and the Danish strain of 1986 produced 23 chicks in Illinois (Thompson et al., 1992). Thus, the number of hatched chicks was quite superior in the Italian strain and resulted from higher egg numbers and better fertility of hatched eggs. The reason for these differences is unknown.

In conclusion, supplementing partridge diets with wheat sprouts during the egg-laying period cannot be recommended, because in the present investigation this caused behavioral and physiological stress responses and impaired egg production. Maize silage and rucola salad can be used, but we were unable to show any significant effects of this supplemental feeding with regard to minimizing stress responses or changing behavior or production. In general, partridge breeders in the production system investigated here did not show overt signs of mal-adaptive behavior or physiological stress responses when fed only the pelleted concentrate or with supplements of maize silage or fresh rucola salad.

	ACKNOWLEDGMENTS

 
The current work was partly financed by the Danish Poultry Council. We wish to thank Else and Børge Papsø, Papsoe, Duelund Vildfarm A/S, Kjellerup, Denmark, for placing their birds, facilities, and expertise at the disposal of researchers in this experiment, I.-M. Jepsen for preparing blood samples, P. Isaksen for behavioral observations, and D. Guemene for performing the corticosterone assay and for comments on an earlier version of this manuscript.

Received for publication January 10, 2007. Accepted for publication March 20, 2007.

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