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1.
Effect of access to wood shavings on gizzard activity was examined for birds fed pelleted wheat and oat diets with or without whole cereal inclusion. Layers on litter floor fed wheat diets with access to coarse wood shavings showed up to 60% higher weight of the gizzard and its content than caged layers fed the same diets without access to wood shavings. No such effect was found by feeding oat diets. Thus, a significant interaction was found, indicating that the appetite for wood shavings may be dependent of fiber level of the diet. Appetite for wood shavings and paper was examined for birds fed wheat and oat diets in 2 other experiments. The intake of wood shavings and paper by birds fed a wheat-based diet was numerically twice as high as in birds fed an oat-based diet. However, the individual variation was remarkably high. Neutral detergent fiber (NDF) concentration in the gizzard of birds fed the oat diet was up to twice (P < 0.05) the fiber concentration in the gizzard of birds fed the wheat diet. Passage of structural fibers through the gizzard and the appetite for feathers in the absence of structural fibers were also studied in an experiment using diets based on rice and casein. Coarse fiber structures were observed to accumulate in the gizzard. In the absence of fiber, birds ate feathers, indicating that birds may eat feathers to compensate for the lack of structural components in the feed.  相似文献   

2.
1. An experiment was conducted to study the effects of inclusion of oat hulls in diets based on whole or ground wheat for broilers. Effects of wood shavings on layers were investigated in a further experiment. 2. Inclusion of oat hulls in wheat-based broiler diets did not affect weight gain. Feed conversion efficiency (FCE), corrected for insoluble fibre contents, was improved by oat hull inclusion. 3. Gizzard size increased with inclusion of oat hulls, whole wheat, wood shavings and grit. 4. Starch digestibility was significantly increased by inclusion of oat hulls for broilers, and by wood shavings for layers. 5. Wood shavings and whole wheat did not affect bile acid concentration of gizzard contents. However, the total amount of bile acids in gizzard increased with access to wood shavings due to an increase in the weight of gizzard contents, indicating an increased gastroduodenal reflux. 6. Fibre concentration was considerably higher in the gizzard contents than in the feed. 7. Duodenal particle size decreased with access to grit. No effect of hulls or whole wheat inclusion was found, indicating that all particles are ground to a certain critical size before leaving the gizzard.  相似文献   

3.
The availability of wood by-products for bedding material is falling in many regions due to rising demand for other uses. The objective of this study was to evaluate six alternative litter sources—river bed sand, coconut husk, rice hulls, Guinea grass, newspaper, and corncob—as a substitute for wood shavings (WS). The trial was carried out over 35 days in an open-sided and naturally ventilated broiler house under conditions of high ambient temperatures and relative humidity. During the brooding period (0 to 14 days), chicks raised on grass had lower (P?<?0.05) footpad temperature than those grown on WS. After the brooding period (15 to 35 days), the temperatures of both litter and birds were higher (P?<?0.05) for coconut husk than for WS. Grass litter resulted in lower (P?<?0.05) final BW, FCR, and production efficiency. Sand and rice hulls were associated with lower (P?<?0.05) survival rate and higher (P?<?0.05) gizzard weight. Litter type did not affect carcass and meat yields. The footpad dermatitis score, associating incidence and severity, was not statistically different among the litter substrates tested, although numerically higher in coconut husk, grass, and corncob. The results obtained in this experiment indicate that, in a hot and humid environment, all materials except grass can be used as a substitute for wood shavings with comparable production efficiency.  相似文献   

4.
1. The objective was to compare the effect of two litter types (wheat straw and wood shavings) and two different rearing conditions (Treated and Control) on welfare indicators, broiler performance, carcase injuries, particularly hock and foot pad dermatitis (FPD), litter characteristics and meat quality. 2. Treated conditions were characterised by a low stocking density (11 birds/m(2)), short photoperiod (16 h light: 8 h dark) and a large amount of litter (3 to 4.5 kg/m(2), respectively, for wheat straw or wood shavings). Control conditions were a high stocking density (14 birds/m(2)), long photoperiod (23 h light:1 h dark) and small amount of litter (2.3 to 3 kg/m(2), respectively, for wheat straw or wood shavings). In addition, the effects of two widely used litter materials, wheat straw and wood shavings, were investigated. 3. The combined effects of lower stocking density, greater amount of litter material and a photoperiod similar to the natural one, reduced the occurrence of FPD in Treated groups keeping the FPD score under the European threshold. 4. Improved rearing conditions led to faster growth rate associated with inferior feed efficiency, whereas litter type exerted negligible effects on broiler performance. 5. Litter moisture content, nitrogen and ammonia released by the litter were lower in Treated groups than Control groups. The use of wood shavings resulted in lower moisture and nitrogen concentrations in the litter.  相似文献   

5.
1. The experiment was to study the effects of floor type and probiotic supplementation (Enterococcus faecium) on performance, morphology of erythrocytes and intestinal microbiota of male Ross 308 broiler chickens. 2. The experimental design was a factorial 2 × 2 with 6 replicates. The factors were floor type (wire floor versus wood shaving litter) and the presence or absence of probiotic. 3. Birds housed on wood shavings exhibited significantly improved weight gain and food intake. 4. Addition of E. faecium led to significantly decreased food intake and gizzard weight. Supplementation with E. faecium positively influenced the ileal and caecal microbiota, with a significant decrease in the population of Escherichia coli. 5. Erythrocyte length decreased and erythrocyte width increased in the birds housed on wood shavings.  相似文献   

6.
ABSTRACT

1. Divergence in outcomes from studies on the effects of litter materials on body weight, feed intake, feed conversion and mortality in broilers has led to a need for a meta-analysis to quantify their effects.

2. A systematic search of published quantitative research relating to wood shavings and alternative bedding litters was conducted using databases.

3. Means, standard deviations and sample sizes were extracted from each study. The response variables were analysed using the standardised mean difference (SMD, control treatment minus alternative litters).

4. The literature demonstrated that alternative materials have no impact on feed intake in broilers, compared to wood shavings (SMD = 0.064, 95% CI = ?0.101–0.229, P = 0.44).

5. There was a positive overall effect of wood shavings on body weight (SMD = 0.253, 95% CI = 0.073–0.433, P = 0.006), feed conversion (SMD = ?0.169, 95% CI = ?0.327 – ?0.012, P = 0.03) and mortality (SMD = ?1.069, 95% CI = ?1.983 – ?0.155, P = 0.02) of broilers, compared to other litter types.

6. Subgroup meta-analysis revealed that straw, when used as an alternative litter material to wood shavings, may be responsible for lower body weight (SMD = 0.654, 95% CI = 0.162–1.146, P = 0.009), worse feed conversion (SMD = ?0.487, 95% CI = ?0.828 – ?0.145, P = 0.005) and higher mortality rates of broilers (SMD = ?3.25, 95% CI = ?5.681 – ?0.819, P = 0.009). Rice husks impaired body weight compared to wood shavings (SMD = 0.535, 95% CI = 0.065–1.004, P = 0.02).

7. It was concluded that different litter types do not affect the broilers’ feed intake. Conversely, broilers kept on straw showed lower body weights, worse feed conversion and higher mortality rates, in comparison to wood shavings. Rice husks decreased body weight compared to wood shavings.  相似文献   

7.
An experiment was conducted to examine the suitability of chopped palm leaves to utilize as a bedding material, compared to wood shavings or wheat straw, on growth performance, immune response, and air quality for broiler production. Three bedding materials were used: wood shavings, chopped palm leaves, and wheat straw. A total of 3,240 one-day-old broiler chicks (Ross 308) was randomly distributed into 3 litter groups (1,080 birds each). Each group had 6 replicate pens (180 birds/pen). All birds were kept under similar environmental conditions, except for bedding material. The obtained results revealed that the growth performance and total mortality rate were not significantly affected by bedding material type. However, using chopped palm leaves as bedding material significantly reduced (P < 0.05) ammonia emission compared to wood shavings and wheat straw (4.1, 7.3 and 8.4 ppm, respectively). A similar trend was observed for settled dust concentration (4.0, 10.3, and 5.9 g/m2, respectively). Moreover, an improvement in cell-mediated immunity was observed in boilers kept on chopped palm leaves. Carcass characteristics were not significantly affected by bedding material. It was concluded that chopped palm leaves are a good alternative bedding material to wood shavings and wheat straw in commercial broiler production.  相似文献   

8.
ABSTRACT

1. This study aimed to investigate effects of dietary fibre and grit on growth performance, gastrointestinal tract development, and gizzard grit retention of geese.

2. The trial had a 3 × 2 factorial design consisting of three levels of dietary crude fibre (CF, 4%, 7% and 10%, adjusted by grass powder), with or without grit addition (1–4 mm river sand).

3. In total, 648, 22-d-old male goslings were randomly allotted to six treatments (six pens/treatment). At 49 d and 70 d of age, one goose per pen was euthanised to collect samples.

4. The birds fed 10% CF had decreased feed conversion ratio (FCR) during 22–49 d, but this effect was less in older geese. Increasing dietary CF levels increased relative weights of gizzards for geese aged 49 d and 70 d. Grit addition decreased the relative weights of gizzard and duodenum of geese aged 49 d. The gizzard of geese could selectively retain grit from feed even with no grit added. With adequate supply, most grit in gizzard was 0.45–3 mm in size.

5. In conclusion, supplement of CF and grit mainly affected gastrointestinal tract, and the amount of CF affected FCR. Geese aged 22–49 d could utilise dietary CF levels of 4%-7% and older birds could feed on diets with up to 10% CF. The gizzard of goose selectively retained grit of a particle size of 0.45–3 mm.  相似文献   

9.
Microflora of two different types of poultry litter   总被引:1,自引:1,他引:0  
1. The microbiological composition of litter (straw and wood shavings) was sampled, prior to placing 1-d-old chicks, during housing of the birds and after depopulation. Two independent trials were conducted. 2. The total aerobic plate count (APC) was determined and the predominant microflora of the samples was identified using flow charts. 3. Before chick placement, the APC of wood shavings (about 4.0 log/g) was lower than the APC of straw (about log 7.5/g). With stocking, in both types of litter the APC increased to about log 9.76/g straw-litter and log 9.89/g wood shavings, respectively. After depopulation, the APC remained high (> log 9 in both types of litter) within the period of observation. 4. From both experiments, 1981 isolates were collected and identified, most of them were Gram-positive. During stocking the birds, the number of Gram-positive isolates (in particular Gram-positive irregular rods and Micrococcaceae) increased; after depopulation it stayed at that high value, whereas the number of Gram-negative isolates remained low. In both types of litter the isolates were obtained in a comparable proportion.  相似文献   

10.
Actions concerning animal health in turkey production are coming more and more to the fore. Litter quality has a great impact on the bird's health and welfare. This study aimed at evaluating the effects of using floor heating, different litter materials, and exposure to litter with a "critical moisture content" of 35% for 16 or 24 hr/day on the severity of foot pad dermatitis (FPD), a widespread disease in fattening turkeys. Four groups of 2-wk-old female turkeys, with 20 birds in each, were reared during 3 wk. All turkeys were fed a commercial pellet diet ad libitum. The first two groups were kept on wood shavings (35% moisture) without and with floor heating. The other two groups were housed on lignocellulose (Soft Cell) of 35% moisture without and with floor heating. In each group, half of the birds were housed for 8 hr/day in adjacent separate boxes where the litter was kept clean and dry throughout the experimental period. Foot pads were assessed weekly for external and at day 35 for histopathologic scoring (scores: 0 = healthy; 7 = ulcer). At day 14 each bird had normal and healthy foot pads. The results indicate that using floor heating resulted in significantly lower FPD scores (0.8 +/- 0.2) compared to groups without floor heating (2.0 +/- 0.8). Using lignocellulose as a litter material resulted in significantly lower histopathologic FPD scores (1.4 +/- 0.7) compared with wood shavings (1.7 +/- 0.8). In all birds housed on dry litter for 8 hr/day, significantly lower FPD scores were found compared to birds housed on wet litter for 24 hr. In conclusion, using floor heating, even with wet litter (35% moisture), independent of the litter type, resulted in reduced severity of FPD compared to those birds housed in pens without using floor heating. Additionally, using lignocellulose as a litter material resulted in lower FPD compared with wood shavings. Keeping litter dry and "warm" could be achieved by using floor heating, which is considered a practical step to enhance animal health and welfare.  相似文献   

11.
In an experiment including 2400 layers, a diet with 40% whole oats incorporated into 3 mm pellets (experimental diet) was compared with a complete diet, also as 3 mm pellets, but containing no whole oats (control diet). These diets were examined in conventional 3-hens cages and two furnished cage systems with 8 or 16 birds per group including nest, perches and litter. The effects of diet, rearing condition and cage system on performance, plumage condition, comb lesions and rear body wounds were studied. Furthermore, the effect of feed structure on gizzard characteristics and interactions with access to litter during rearing and laying periods were examined. The hybrids LSL and Shaver 2000 were included in the experiment. Egg production was lower (P<0.05) in furnished cages than in conventional cages. No difference in plumage condition was found between diets, but a significantly poorer plumage condition (P<0.05) was observed with increasing group size. Also, the frequencies of rear body (P<0.05) wounds increased as the group sizes increased, while no such effect was observed for comb lesions. Higher (P<0.05) feed consumption was observed in furnished cages than in the conventional, causing a corresponding increase (P<0.05) in feed conversion rate (FCR). Higher (P<0.05) FCR was observed for birds fed pellets with whole oats than the control. Whole oats also increased (P<0.05) the weight of gizzard and gizzard contents. For LSL, better (P<0.05) plumage condition was found for birds reared on a deep litter floor compared to cage rearing. It was concluded that no beneficial effect of replacing high amounts of ground oats with whole oats was observed. Genotype and rearing method may interact with housing system.  相似文献   

12.
Mertect 340-F (thiabendazole) was evaluated as a mold inhibitor for litter in turkey confinement housing using green oak wood shavings heavily contaminated with mold spores. One day before the addition of shavings, two environmentally controlled rooms were sprayed with Mertect 340-F at a rate of 51.0 ml in 11.37 liters of water (16 fl. oz./6000 sq. ft.). After the litter was added, it was treated with Mertect 340-F at a rate of 33.0 ml in 75.8 liters of water (32 fl. oz./6000 sq. ft.). The litter was treated again at 6 and 12 weeks. Mertect 340-F-treated litter had significantly lower mold spore counts than water-treated litter. Turkeys reared on Mertect 340-F-treated litter displayed no adverse effects. No obvious differences between groups were noted post mortem. Microscopically, however, lungs from turkeys on water-treated litter had a higher incidence of granulomas and mycelia than lungs from birds on Mertect 340-F-treated litter.  相似文献   

13.
Sources of Salmonellae in broiler chickens in Ontario.   总被引:3,自引:2,他引:1       下载免费PDF全文
Sources of Salmonellae infecting broiler chicken flocks in Ontario were investigated from July, 1975 to April, 1976. Three broiler flocks were investigated on each of four farms which received chicks from a common hatchery. Samples of feed and new litter were preenriched in nonselective broth subcultured to Salmonella-selective enrichment broth and plated on Salmonella-selective differential agar.Samples of used litter, water, culled chicks, insects, mice, wild birds and environmental swabs were not cultured initially in the nonselective broth. Fecal samples from principal and occasional flock attendants were examined for Samonellae. Salmonella infection, as judged by contaminated flock litter was detected in six flocks on two of the farms while the flocks on the other farms remained negative. Salmonellae were isolated from 23 of 412 feed samples (nine serotypes), six of 35 new wood shaving samples (four serotypes), one of 29 pools of culled chick viscera (one serotype) and 44 of 267 used litter samples (14 serotypes). These results indicate that broiler chicken flocks were infected with diverse Salmonellae introduced in day old chicks, pelleted feeds, wood shavings and residual contamination from the preceding flock.  相似文献   

14.
Among other factors (eg, feed), bedding material has an important effect on stable air quality with respect to airborne particle formation. This study was designed to establish which material is suited to create an improved stable environment for horses. First, the following materials were analyzed under standardized conditions in a laboratory experiment: wheat straw, dry wood shavings, hemp shives, linen shives, wheat straw pellets, paper cuttings (unprinted newspaper). The second investigation was carried out under in situ conditions in which three of these bedding materials (wheat straw, wood shavings, and straw pellets) were analyzed under practical conditions. In both experiments, airborne particle concentrations were detected online with the gravimetrically measuring analyzer TEOM 1400a (Rupprecht & Patashnick Co., Franklin, MA). In the laboratory experiment, the TEOM was equipped successively with different inlets to measure the particle fractions PM1, PM2.5, PM10, and PM20. During the in situ experiment, only the fraction PM10 was detected. In the laboratory experiment, hemp and linen had the highest generation of airborne particles in all fractions. The lowest particle generation was detected with straw pellets. Results of the in situ investigation supported results of the laboratory experiment with respect to mean particle generation of straw pellets. With an average of 111.2 ± 149.2 μg/m3, it was significantly lower than the mean particle generation of wheat straw with 227.5 ± 280.8 μg/m3. The particle generation of wood shavings had an average of 140.9 ± 141.9 μg/m3 and also was significantly lower than the generation by wheat straw. An activity-correlated variation of particle concentrations was found. In conclusion, taking both experiments into consideration, straw pellets seemed to be suitable for horse stables, to promote an improvement in the stable climate in relation to airborne particle formation.  相似文献   

15.
1. Hazelnut husks and some other litter materials were compared for litter properties and their effects on broiler performance. 2. A total of 750 1-d-old broiler chicks were weighed and assigned at random to 1 of 5 treatments, with each treatment replicated 3 times. 3. The treatments were wood shavings (control), wheat stalks, rice hulls, hazelnut husks, and a mixture of 50% rice hulls and 50% hazelnut husks. 4. Although hazelnut husks were associated with lower body weights at 49 d of age, food efficiency mortality, carcase yield, breast blisters and production index were similar to birds on wood shavings. Hazelnut husks had the highest litter moisture. 5. The results show that hazelnut husks alone and when mixed with rice hulls are a potential alternative litter material for broiler production.  相似文献   

16.
1. An experiment was conducted to study the effects of whole wheat, oats and barley at different inclusion levels on performance, starch digestibility, duodenal particle size distribution, gizzard weight and pH of gizzard contents for broiler chickens. 2. Feed consumption and weight gain were significantly reduced when ground cereals were replaced by whole cereals (P < 0.05). However, feed conversion efficiency was not affected by inclusion of up to 440 g/kg of whole wheat, and up to 300 g/kg of whole oats and barley. 3. Duodenal particle size was measured by laser diffraction to below 1 micron in size. A remarkably large proportion of particles were below 100 microns, with as much as 50% of the particles in the duodenum being below 40 microns in size. Inclusion of moderate amounts of whole cereals reduced the duodenal mean particle size. Large inclusions of whole cereals decreased (P < 0.05) the proportion of particles up to 40 microns in size, and increased (P < 0.05) the proportion with size between 100 and 300 microns. 4. Starch digestibility was improved (P < 0.05) by replacing ground wheat or barley with whole wheat or barley. 5. There was no consistent effect of cereal species or feed form on the pH value of the gizzard contents.  相似文献   

17.
Poultry are normally reared on bedding materials such as wood shavings or rice hulls. Poultry litter reuse for multiple flocks has become economically important in modern broiler production. However, this practice results in the litter serving as a reservoir of numerous microbial organisms, including, yeasts, molds, multiple types of viruses, and bacterial pathogens such as Salmonella, Escherichia, Campylobacter, Clostridium, Staphylococcus, and Pseudomonas. The foodborne pathogens are of particular importance for poultry producers. During the preharvest feed withdrawal period, consumption of contaminated litter and feces by the birds can lead to infection of the upper gastrointestinal tract with Salmonella, which presents substantial problems at processing. The current study was conducted to determine whether the use of a liquid bacterial product (LBP), such as LT1000, could reduce the load of Salmonella Typhimurium in poultry manure. The LBP was added to sterile poultry manure then challenged with 108 cfu/mL of Salmonella Typhimurium. The concentration of Salmonella Typhimurium was measured over 9 d or until the Salmonella Typhimurium was no longer detected. In 91% of the trials, Salmonella Typhimurium was completely eliminated within 9 d. This demonstrates that the LBP used in the current study has the potential to substantially improve the overall microbiological safety of used poultry litter.  相似文献   

18.
High dietary protein is thought to increase the incidence of foot pad dermatitis (FPD) as a result of increased uric acid and secondary ammonia production in the excreta or litter. This study was conducted on female turkeys over a period of 3 wk to test the effects of water alone, and also of these end products of protein metabolism, independent of the presence of excreta, on the development and severity of FPD. The animals were allocated into four groups, with 20 birds in each, and housed in floor pens on dry, clean wood shavings (changed daily) throughout the experiment. The control group was housed continuously in its pen, whereas the other groups were additionally exposed daily (for 8 hr) to experimentally treated wood shavings, in adjacent separate boxes, enriched with water alone or water with NH4Cl or uric acid. NH4Cl and uric acid were added via water to the litter to achieve the concentrations of ammonia and uric acid in the litter as found in the excreta of turkeys (about 0.50 g ammonia and 20 g uric acid/kg). The wet litter was kept clean by removing the excreta twice daily and by changing the litter twice a week. The foot pads of all birds were examined on days 0, 7, 14, and 21 and scored externally (macroscopically). Three birds were selected from each group on days 0, 7, and 14, while the remaining 11 birds/group were sacrificed on day 21 for histopathologic assessment of foot pads. The severity of FPD was found to be markedly higher (about 3 times) on wet than on dry litter. There were no negative effects of ammonia and uric acid on foot pad lesions. The results indicate that high litter moisture is the most likely factor causing FPD in turkeys. A focus on nitrogenous irritants in the litter was not substantiated. Exposure of birds to wet litter (in the absence of excreta) for only 8 hr/day was sufficient to develop foot pad lesions. The present results suggest that a focus on the protein content of the diet as a cause of FPD may be misplaced, but all dietary factors which increase excreta or litter moisture, or both, should be considered. The prevalence and severity of FPD can be reduced by maintaining dry litter.  相似文献   

19.
1. As part of a programme investigating the causation of pecking damage in fowls, this experiment tested a proposal that birds may receive more feather pecks when their plumage colour contrasts with floor litter colour, because litter particles on plumage (as a consequence of dustbathing) may then have greater stimulus value. 2. Groups consisting of 7 light- and 7 dark-coloured bantams were reared from 1 to 11 weeks of age in pens with either wood shavings (light coloured, n=6) or peat (dark coloured, n=6) floor litter. 3. Feather loss from pecking commenced in the 3rd week of life and increased thereafter, but observed pecking damage scores were not consistent with the hypothesis being tested. 4. Despite many more pecks at birds being seen (over 10 weeks) in the wood shavings groups' (661 at particles on plumage, 1795 not at particles) than in peat groups (205, 787), there was no effect of litter substrate on pecking damage. The only evidence supporting the proposal was the finding that, in groups on wood shavings, significantly more pecks at particles on plumage were directed from light coloured birds towards dark ones, than from light to light, dark to light, or dark to dark. 5. Feather eating was confirmed from the presence of feather material in 2% to 15% of faecal droppings collected from each group at 11 weeks, but these proportions were not correlated with pecking damage scores. 6. The results imply that only some feather pecks/pulls were damaging and only some eaten feathers were pulled from other birds.  相似文献   

20.
1. A field experiment was conducted with commercial broiler breeder females to assess the hypothesis that the provision of bunches of string and bales of wood shavings would provide attractive environmental enrichment and improve welfare by decreasing aggression and feather damage. 2. The experiment was a randomised block factorial design conducted in a commercial flock of 21,600 female broiler breeders in 12 pens of 1800 chicks. Treatments were environmental enrichment (4 plastic coated bales of wood shavings and 50 bunches of string) from hatch (EE1) or 8 weeks of age (EE2) and a control treatment with no environmental enrichment. There were 4 replicates (rooms). 3. Bird activity was videotaped at 5, 10 and 16 weeks of age and subsequently scored for the number of birds using the perch or pecking at a bale, drinker, litter and section of the wall at 10-min intervals for 4 h throughout the photoperiod (24 times/d). Aggression was assessed by determining the number of aggressive acts in 2-min intervals during 8 periods of the day. The skin and feather condition of 25 birds in each pen were scored at 6, 12 and 18 weeks and the condition of the string bunches was scored at the end of the experiment. 4. The proportion of birds pecking the bales, wall and litter declined and the proportion pecking at the drinker and using the perch increased with age. The number of birds pecking at the bale was similar in EE1 and EE2 at 10 and 16 weeks of age. 5. The string bunches were not extensively used. The condition of the bunches of string in EE2 was worse than in EE1 at the end of the experiment. 6. The number of aggressive acts increased with age and there was no consistent difference between treatments. 7. There was an increase with age in the damage score for feathers over the back and wings and around the tail and vent but no differences between treatments.8. Provision of litter in the form of unopened bales of wood shavings was a commercially acceptable form of environmental enrichment, but there was no evidence that behavioural changes associated with feed restriction, including the prevalence of aggression, were improved.  相似文献   

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