Effects of Feed Contaminant Deoxynivalenol on Plasma Cytokines and mRNA Expression of Immune Genes in the Intestine of Broiler Chickens

An experiment was conducted to investigate the individual and combined effects of dietary deoxynivalenol (DON) and a microbial feed additive on plasma cytokine level and on the expression of immune relevant genes in jejunal tissues of broilers. A total of 40 broiler chicks were obtained from a commercial hatchery and divided randomly into four groups (10 birds per group). Birds were reared in battery cages from one day old for 5 weeks. The dietary groups were 1) control birds fed basal diet; 2) DON group fed basal diet contaminated with 10 mg DON/ kg feed; 3) DON + Mycofix group fed basal diet contaminated with 10 mg DON/ kg feed and supplemented with a commercial feed additive, Mycofix® Select (MS) (2.5 kg/ton of feed); 4) Mycofix group fed basal diet supplemented with MS (2.5 kg/ton of feed). At 35 days, the plasma levels of tumor necrosis factor alpha (TNF-α) and interleukin 8 (IL-8) were quantified by ELISA test kits. Furthermore, the mRNA expression of TNF-α, IL-8, IL-1β, interferon gamma (IFNγ), transforming growth factor beta receptor I (TGFBR1) and nuclear factor kappa-light-chain-enhancer of activated B cells 1 (NF-κβ1) in jejunum were quantified by qRT-PCR. The results showed that the plasma TNF-α decreased in response to DON, while in combination with MS, the effect of DON was reduced. DON down-regulated the relative gene expression of IL-1β, TGFBR1 and IFN-γ, and addition of MS to the DON contaminated diet compensates these effects on IL-1β, TGFBR1 but not for IFN-γ. Furthermore, supplementation of MS to either DON contaminated or control diet up-regulated the mRNA expression of NF-κβ1. In conclusion, DON has the potential to provoke and modulate immunological reactions of broilers and subsequently could increase their susceptibility to disease. The additive seemed to have almost as much of an effect as DON, albeit on different genes.     

Exposing broiler eggs to green,red and white light during incubation

Previous work has shown that exposing broiler eggs to white light during incubation can improve hatchability and post-hatch animal welfare. It was hypothesized that due to how different wavelengths of light can affect avian physiology differently, and how pigmented eggshells filter light that different monochromatic wavelengths would have differential effects on hatchability and post-hatch animal welfare indicators. To determine, we incubated chicken eggs (n=6912) under either no light (dark), green light, red light or white light; the light level was 250 lux. White and red light were observed to increase hatch of fertile (P<0.05) over dark and green light incubated eggs. White, red and green light exposure during incubation improved (P<0.05) the proportion of non-defect chicks over dark incubated eggs. Post-hatch 45-day weight and feed conversion was not affected by light exposure of any wavelength (P>0.05). Fear response of during isolation and tonic immobility was reduced (P<0.05) in broilers incubated under white or red light when compared with either green or dark broilers. Broilers incubated with white or red light had lower (P<0.05) composite asymmetry scores and higher (P<0.05) humoral immunity titers than dark incubated broilers, however, green light broilers did not differ (P>0.05) from dark incubated broilers. All light incubated broilers had lower (P<0.05) plasma corticosterone and higher (P<0.05) plasma serotonin concentrations than dark incubated broilers. These results indicate that white light and red light that is a component of it are possibly the key spectrum to improving hatchability and lower fear and stress susceptibility, whereas green light is not as effective. Incubating broiler eggs under these spectrums could be used to improve hatchery efficiency and post-hatch animal welfare at the same time.     

Single and Combined Effects of Deoxynivalenol Mycotoxin and a Microbial Feed Additive on Lymphocyte DNA Damage and Oxidative Stress in Broiler Chickens

The immune and intestinal epithelial cells are particularly sensitive to the toxic effects of deoxynivalenol (DON). The aim of this experiment was to study the effects of DON and/or a microbial feed additive on the DNA damage of blood lymphocytes and on the level of thiobarbituric acid reactive substance (TBARS) as an indicator of lipid peroxidation and oxidative stress in broilers. A total of forty 1-d-old broiler chicks were randomly assigned to 1 of 4 dietary treatments (10 birds per group) for 5 wk. The dietary treatments were 1) basal diet; 2) basal diet contaminated with 10 mg DON/kg feed; 3) basal diet contaminated with 10 mg DON/kg feed and supplemented with 2.5 kg/ton of feed of Mycofix Select; 4) basal diet supplemented with Mycofix Select (2.5 kg/ton of feed). At the end of the feeding trial, blood were collected for measuring the level of lymphocyte DNA damage of blood and the TBARS level was measured in plasma, heart, kidney, duodenum and jejunum. The dietary exposure of DON caused a significant increase (P = 0.001) of DNA damage in blood lymphocytes (31.99±0.89%) as indicated in the tail of comet assay. Interestingly addition of Mycofix Select to DON contaminated diet decreased (P = 0.001) the DNA damage (19.82±1.75%) induced by DON. In order to clarify the involvement of lipid peroxidation in the DNA damage of DON, TBARS levels was measured. A significant increase (P = 0.001) in the level of TBARS (23±2 nmol/mg) was observed in the jejunal tissue suggesting that the lipid peroxidation might be involved in the DNA damage. The results indicate that DON is cytotoxic and genotoxic to the chicken intestinal and immune cells and the feed additive have potential ability to prevent DNA damage induced by DON.     

Frequent range visits further from the shed relate positively to free-range broiler chicken welfare

Little is known about the implications of accessing an outdoor range for broiler chicken welfare, particularly in relation to the distance ranged from the shed. Therefore, we monitored individual ranging behaviour of commercial free-range broiler chickens and identified relationships with welfare indicators. The individual ranging behaviour of 305 mixed-sex Ross 308 broiler chickens was tracked on a commercial farm from the second day of range access to slaughter age (from 16 to 42 days of age) by radio frequency identification (RFID) technology. The radio frequency identification antennas were placed at pop-holes and on the range at 2.7 and 11.2 m from the home shed to determine the total number of range visits and the distance ranged from the shed. Chickens were categorised into close-ranging (CR) or distant-ranging (DR) categories based on the frequency of visits less than or greater than 2.7 m from the home shed, respectively. Half of the tracked chickens (n=153) were weighed at 7 days of age, and from 14 days of age their body weight, foot pad dermatitis (FPD), hock burn (HB) and gait scores were assessed weekly. The remaining tracked chickens (n=152) were assessed for fear and stress responses before (12 days of age) and after range access was provided (45 days of age) by quantifying their plasma corticosterone response to capture and 12 min confinement in a transport crate followed by behavioural fear responses to a tonic immobility (TI) test. Distant-ranging chickens could be predicted based on lighter BW at 7 and 14 days of age (P=0.05), that is before range access was first provided. After range access was provided, DR chickens weighed less every week (P=0.001), had better gait scores (P=0.01) and reduced corticosterone response to handling and confinement (P<0.05) compared to CR chickens. Longer and more frequent range visits were correlated with the number of visits further from the shed (P<0.01); hence distant ranging was correlated with the amount of range access, and consequently the relationships between ranging frequency, duration and distance were strong. These relationships indicate that longer, more frequent and greater ranging from the home shed was associated with improved welfare. Further research is required to identify whether these relationships between ranging behaviour and welfare are causal.     

Effects of β-glucanase supplementation of barley diets on growth performance of broilers

A trial was performed to examine the effects of levels of barley substitution and supplementation with β-glucanase in a corn-soybean diet on growth performance and intestinal characteristics of broiler chickens. The experiment involved five levels of barley substituted for corn (0, 125, 250, 500, and 1000 g/kg) and two levels of β-glucanase supplement (with 0.5 g/kg and without) in a factorial arrangement with two replicates. Four hundred day-old commercial strain Harber broiler chickens were randomly allocated into twenty groups of ten dietary treatments for a six-week feeding trial, growing (0-3 week) and finishing period (4-6 week). Unless supplemented with β-glucanase, broilers receiving the diet with more than 250 g/kg of the barley substitute gained slower during the growth period. Conversely, supplementing β-glucanase did not improve total weight gain (0-6 weeks) with a diet of 500 g/kg barley substitution. As the level of barley substitution increased, feed intake in the growing period decreased significantly and viscosity of the intestinal contents increased. However, such an increase did not significantly influence feed conversion (P > 0.05). Supplementation with β-glucanase on diet up to 250 g/kg of barley substitute not only enhanced body weight gains of growing broilers, but also improved the live-weight of six-week-old broilers (P < 0.05).     

Effects of low to moderate levels of deoxynivalenol on feed and water intake,weight gain,and slaughtering traits of broiler chickens

The aim of the study was to evaluate the effects of low to moderate oral exposure to the Fusarium toxin deoxynivalenol (DON; derived from culture material) on performance, water intake, and carcass parameters of broilers during early and late developmental phases. A total of 160 Ross 308 broilers were randomly allocated to four different feeding groups (n = 40/group) including 0 (control), 2.5, 5, and 10 mg DON/kg wheat-soybean meal-based feed. Three consecutive replicates of the experiment were performed. Half of the broilers were slaughtered in week 3 of the trial whereas the other half were slaughtered in week 5. Dry matter intake (DMI) and water intake (WI) were recorded on a daily basis and the body weight (BW) and BW gain (BWG) were determined weekly. The following carcass traits were recorded and calculated in absolute and relative data: dressed carcass weight, breast muscle weight, leg weight, and liver weight. Data showed that BW (P < 0.001), BWG (P = 0.005), and DMI (P < 0.001) were reduced by DON-feeding during the entire feeding period. The ratio of DMI to body weight gain (DMI/BWG) was not affected by the treatment. However, the ratio of water to DMI (WI/DMI) increased in DON-treated birds (P = 0.021). Contrast analysis showed that DON tendentially reduced slaughter weight (P = 0.082) and decreased leg yield (P = 0.037) in DON-fed chickens in week 5 of the experiment. Liver organ weight decreased in the 3-week-old DON-fed broilers compared to that in the control-fed birds (P = 0.037). In conclusion, the study suggests that DMI and BW were negatively affected under the experimental conditions at DON levels lower than the current guidance value in the European Union of 5 mg/kg feed. The study also indicates that broilers fed on low to moderate level DON-contaminated diets showed increased WI/DMI ratio which might have negative influence on wet litter syndrome.     

Play behaviour,fear responses and activity levels in commercial broiler chickens provided with preferred environmental enrichments

There is currently a lack of research investigating the effectiveness of commercial broiler enrichments, and in particular the ability of these additions to create opportunities for positive welfare. One aim of this study was to investigate whether offering broiler chickens enrichments that have recently been found to be preferred leads to increased levels of activity. A second aim was to investigate the emotional effects of provision of these enrichments by assessing levels of fearfulness and play-like activity. Commercially housed broilers were assigned to treatment houses containing either: (1) platform perches, (2) platform perches+peat dust baths, (3) no enrichment (control). Activity levels and play behaviours in unenriched areas of the house were measured in weeks 3, 4 and 5. Levels of active behaviours, such as foraging and locomotion, were determined from video recordings of undisturbed birds in unenriched areas of the house. To stimulate play-like behaviours an observer walked through the birds, displacing them and creating a space. The broilers using the space were then filmed for 5 min and the occurrences of frolicking, sparring and food-running were recorded. Fearfulness of broilers in unenriched areas of the house, and also when using enrichments, was measured using observer avoidance tests in week 5. We found that creating space among the broilers was a successful method of stimulating play (largely sparring and frolicking), with play being observed in 93% of videos, however the presence of enrichments did not have an effect on the level of play recorded (P>0.05). There was also no treatment effect on activity levels of broilers in unenriched areas (P>0.05), however levels of overall activity decreased as broilers aged. Compared with the control, flight distances in unenriched areas were significantly lower in the perches+dust bath treatment (P=0.026), and were numerically lower in the perches treatment. This suggests a reduction in fearfulness with increased environmental complexity, and thus possible welfare benefits. It is suggested that further research should investigate whether increasing the level of provision of these enrichments leads to more marked improvements in welfare.     

Nanoencapsulation (in vitro and in vivo) as an efficient technology to boost the potential of garlic essential oil as alternatives for antibiotics in broiler nutrition

The addition of essential oil (EO) as chitosan encapsulated can increase the efficiency of these oils in broiler feeding. Therefore, the objective of the current research was to explore the antibacterial and antioxidant potential of garlic essential oil (GEO) (free vs. nanoencapsulated) and their effects on performance, gene expression of mucin2, microbial, and morphology of intestine in broilers. A total of 900 1-day-old male broilers (Ross 308) were assigned to six dietary treatments (0, 100, and 200 mg/kg free GEO and 0 (contain of chitosan), 100 and 200 mg/kg nanoencapsulated GEO) with a 2 × 3 factorial arrangement based on completely randomized design. Garlic essential oil encapsulation with chitosan significantly enhanced antibacterial and antioxidant parameters. At 100 mg/kg nanoencapsulated GEO had significant (P < 0.01) advantages in improving BW gain (BWG) (22–42 and 0–42) and feed conversion ratio (FCR) (0–42). Maximum feed intake (FI) was also associated with the control group (P < 0.05). Broilers fed on 100 mg/kg of nanoencapsulated GEO showed higher villi length and width relative to other treatments and villi length to crypt depth ratio as well (P < 0.01). The nanoencapsulation process of GEO (P < 0.01) affected the Lactobacilli population in the digesta of ileo-caecum and mucin2 gene expression. In broiler chickens, the tested EO, especially nanoencapsulated type, enhanced more evaluated parameters. Because of its ideal properties, nanoencasulating with chitosan may also be an effective and inexpensive way to protect bioactive compounds and improve GEO effects in broiler chickens.     

Deoxynivalenol Impairs Hepatic and Intestinal Gene Expression of Selected Oxidative Stress,Tight Junction and Inflammation Proteins in Broiler Chickens,but Addition of an Adsorbing Agent Shifts the Effects to the Distal Parts of the Small Intestine

Broiler chickens are rather resistant to deoxynivalenol and thus, clinical signs are rarely seen. However, effects of subclinical concentrations of deoxynivalenol on both the intestine and the liver are less frequently studied at the molecular level. During our study, we investigated the effects of three weeks of feeding deoxynivalenol on the gut wall morphology, intestinal barrier function and inflammation in broiler chickens. In addition, oxidative stress was evaluated in both the liver and intestine. Besides, the effect of a clay-based mycotoxin adsorbing agent on these different aspects was also studied. Our results show that feeding deoxynivalenol affects the gut wall morphology both in duodenum and jejenum of broiler chickens. A qRT-PCR analysis revealed that deoxynivalenol acts in a very specific way on the intestinal barrier, since only an up-regulation in mRNA expression of claudin 5 in jejunum was observed, while no effects were seen on claudin 1, zona occludens 1 and 2. Addition of an adsorbing agent resulted in an up-regulation of all the investigated genes coding for the intestinal barrier in the ileum. Up-regulation of Toll-like receptor 4 and two markers of oxidative stress (heme-oxigenase or HMOX and xanthine oxidoreductase or XOR) were mainly seen in the jejunum and to a lesser extent in the ileum in response to deoxynivalenol, while in combination with an adsorbing agent main effect was seen in the ileum. These results suggest that an adsorbing agent may lead to higher concentrations of deoxynivalenol in the more distal parts of the small intestine. In the liver, XOR was up-regulated due to DON exposure. HMOX and HIF-1α (hypoxia-inducible factor 1α) were down-regulated due to feeding DON but also due to feeding the adsorbing agent alone or in combination with DON.     

Dietary L-arginine supplementation reduces abdominal fat content by modulating lipid metabolism in broiler chickens

This study investigated the effects of different levels of dietary L-arginine (L-Arg) supplementation on the abdominal fat pad, circulating lipids, hepatic fatty acid synthase (FAS) gene expression, gene expression related to fatty acid β-oxidation, and the performance of broiler chickens. We tested whether the dietary L-Arg levels affected the expression of genes related to lipid metabolism in order to reduce body fat deposition. A total of 192 broiler chickens (Cobb 500) aged 21 days with an average BW of 920 ± 15 g were randomly assigned to four groups (six broilers per replicate and eight replicates per treatment). The control group was fed a basal diet, whereas the treatment groups were fed basal diets supplemented with 0.25%, 0.50%, or 1.00% L-Arg for 3 weeks. The average daily feed intake, average daily gain and feed : gain ratio were not affected by the dietary L-Arg levels. However, chickens supplemented with L-Arg had lower abdominal fat content, plasma triglyceride (TG), total cholesterol (TC) concentrations, hepatic FAS mRNA expression and increased heart carnitine palmitoyl transferase1 (CPT1) and 3-hydroxyacyl-CoA dehydrogenase (3HADH) mRNA expression. These findings suggest that the addition of 0.25% L-Arg may reduce the plasma TC concentration by decreasing hepatic 3-hydroxyl-3-methylglutaryl-CoA reductase mRNA expression. This may lower the plasma TG and abdominal fat content by suppressing hepatic FAS mRNA expression and enhancing CPT1 and 3HADH (genes related to fatty acid β-oxidation) mRNA expression in the hearts of broiler chickens.     

The learning ability and memory retention of broiler breeders: 1 effects of reduced balanced protein diet on reward based learning

Learning and mental abilities of farm animals are important for their adaptation to new environments and could serve as an indicator for welfare and performance. This study assessed the learning ability and memory retention of broiler breeders through a T-maze test with a reward v. no reward set-up. Feed supplemented with or without meal worms served as a reward. Two trials were conducted with either parent stock (PS) breeders or pure line A (PL) breeders and with the same dietary treatment namely a control (C) group fed with standard commercial diets and a reduced balanced protein (RP) group fed with RP diets (25% reduction of CP and amino acids). To maintain similar target BW, the RP group received on average 10% more feed. A tonic immobility (TI) test was performed to estimate the fearfulness of PS breeders. Most breeders were capable of completing the T-maze tests, but the C group needed less time compared with the RP group when their own feed was given as a reward. However, when meal worms were provided as an extra incentive, the RP group completed the maze significantly faster than the C group. Compared to the C breeders, the RP breeders remained longer in a TI state, indicating a higher level of fearfulness. Long-term memory retention in the T-maze test was observed in both groups. It is concluded that the RP diet had no influences on the learning ability of the reward v. no reward discrimination test and its memory retention of broiler breeders. The increased amount of time the RP breeders needed to solve the test was probably due to a higher sense of fear. Furthermore, the RP diet enhanced the motivation of breeders to obtain an alternative feed such as meal worms.     

Real-time quantitative PCR measurement of ileal Lactobacillus salivarius populations from broiler chickens to determine the influence of farming practices

A real-time quantitative PCR assay targeting a 16S-23S intergenic spacer region sequence was devised to measure the sizes of populations of Lactobacillus salivarius present in ileal digesta collected from broiler chickens. This species has been associated with deconjugation of bile salts in the small bowel and reduced broiler productivity. The assay was tested as a means of monitoring the sizes of L. salivarius populations from broilers fed diets with different compositions, maintained at different stocking densities, or given the antimicrobial drugs bacitracin and monensin in the feed. Stocking densities did not influence the numbers of L. salivarius cells in the ileum. A diet containing meat and bone meal reduced the size of the L. salivarius population relative to that of chickens given the control diet, as did administration of bacitracin and monensin in the feed. These changes in the target bacterial population were associated with improved broiler weight gain.     

Non-intrusive tracking of commercial broiler chickens in situ at different stocking densities

Unlike several other farm animal species, the broiler chicken remains unprotected by species-specific legislation. The densities at which broilers should be kept is a highly contentious issue—some studies have demonstrated increased welfare problems at higher densities, whilst a few others have, contrary to expectations, suggested that broilers may actually find crowds of other birds attractive. A tracking method was developed and used to provide an insight into the social preferences of commercial broiler chickens in situ—inside commercial, closed-system broiler houses. The aim was to simultaneously assess the relative impact of global measures of density, such as target and actual stocking densities and local measures of the social environment on the behaviour and route taken to feed by focal birds. Birds were tracked inside 20 commercial broiler houses across the UK. Results from this study show that stocking density per se seems to have little direct effect on the individual behaviours of focal broiler chickens. However, there may still be an indirect effect of stocking density on broiler behaviour, mediated through the local social environment.     

The effects of regular handling on fear responses in the domestic chick

Reduction of fear in the domestic chick by regular handling was assessed and an attempt was made to determine whether such an effect was due specifically to reduced fear of human beings or to a general reduction in fearfulness. Regular handling decreased the tonic immobility response, a fear-potentiated phenomenon, and increased approach to a human being, but had no effect on approach towards an inanimate object. These findings were common to three strains (two layer, one broiler), and suggest that handling does not depress general fearfulness, but specifically reduces fear of human beings, presumably through habituation.     

The effects of feed restriction on plasma biochemistry in growing meat type chickens (Gallus gallus)

The effect of feed restriction on plasma hormones (triiodothyronine - T(3), thyroxine - T(4), and corticosterone), protein, lipid, carbohydrate, and mineral metabolism and activity of plasma enzymes (creatine kinase, alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase) were studied in meat type female chickens (Gallus gallus). Ad libitum fed birds were compared with those subjected to severe and moderate quantitative feed restriction from 16 to 100 days of age. Feed restriction elevated plasma T(4) and corticosterone levels and reduced T(3). A feed restriction-induced decrease was observed for plasma protein and albumin concentrations, but not for uric acid and creatinine. Total plasma lipids, triacylglycerols, cholesterol, high density lipids, and calcium were lower for the feed restricted chickens, in particular during the latter phase of the experiment. Concentrations of glucose and phosphorus were not altered by feeding treatment. Activity of alkaline phosphatase was significantly increased in restricted chicks from day 58. Significant changes of plasma biochemical parameters induced by severe and moderate quantitative feed restriction illustrate that limiting feed intake poses an intensive stress on meat type chickens during the rapid growth period. However, activities of creatine kinase, aspartate aminotransferase, and alanine aminotransferase were significantly higher in ad libitum fed chickens during this period. This elevation in enzymatic activity may be in response to tissue damage, indicating potential health and welfare problems also in ad libitum fed meat type chickens, resulting from selection for intensive growth.     

Dietary deoxynivalenol does not affect mineral element accumulation in breast and thigh muscles of broiler chicken

Deoxynivalenol (DON), a well-known contaminant of feed, can have negative effects on gut permeability and function in poultry, which then could affect major and trace element content of the broilers’ breast and thigh muscles, and ultimately reduce meat quality. To study this hypothesis, DON-contaminated diet was fed to broiler chicks. Two groups of birds were housed in metabolic cages with free access to water and feed, with or without DON (10 mg/kg). After 5 weeks, birds were dissected and samples of the breast and thigh muscles, feed and droppings were analysed for five macro (Ca, K, Mg, Na, and P) and ten micro elements (Al, Cr, Cu, Fe, Mn, Li, Mo, Ni, Pb, Rb, and Zn) by inductively coupled plasma optical emission spectrometry (ICP-OES) or inductively coupled plasma mass spectrometer (ICP-MS) methods. In both groups, increased (p?<?0.05) concentrations of Ca Na, Fe, Mn, and Zn were found in thigh muscles compared with the breast, whereas the concentrations of Mg, P, and Rb were higher in the breast muscles. DON had no effect on the elemental contents of the broilers’ breast and thigh muscles. In conclusion, DON at a level of 10 mg/kg feed to broiler chicken over of 5 weeks did not alter the macro or micro element composition in muscle meat.     

Investigation on the effect of different levels of dried sweet orange (Citrus sinensis) pulp on performance,carcass characteristics and physiological and biochemical parameters in broiler chicken

Utilization of agricultural by-products in animal nutrition is a matter of great concern. Dried sweet orange (Citrus sinensis) pulp (DCSP) is a potential source of valuable nutrients and natural antioxidants for poultry feed. In the experiment, a feeding trial was conducted in order to investigate the effect of different levels of dried orange residues in diet on broiler growth performance, carcass characteristics, blood metabolites, humoral immunity, and cecum microbial population. A total of 200 one day experimental broiler chicks were distributed into a completely randomized design (CRD) which included 5 dietary treatments with 4 replicates per each treatment and 10 birds fed in each replicate. The experimental treatments consist of a control group (without additive), 0.5%, 1.0%, 1.5%, and 2% of DCSP (residue) in diet. Weight gain, feed intake and feed conversion ratio (FCR) were measured. Blood parameters and carcass traits were measured in the postnatal 35th day. The highest level of dried orange residues in treatment 5 (T5) had significantly increased the feed intake and body weight of broilers in groups and overall during the rearing period (P > 0.05). Different levels of dried orange residues had no significant effect on chicken FCR. Using of dried orange residues significantly decreased the liver and abdominal fat of broilers (P < 0.05). T5 has also significantly lower level of triglyceride than the control (T1) and treatment 2 (T2) (P < 0.05). In conclusion, the use of dried orange residues improved some performance (e.g. feed intake and body weight gain), decreased liver and abdominal fat and also serum triglyceride level in broiler chicken.     

Effects of dark brooders and overhangs on free-range use and behaviour of slow-growing broilers

Broiler chickens often make limited use of the free-range area. Range use is influenced by type of shelter available. Range use may possibly be improved by a more gradual transition from the house to the range and by using dark brooders (secluded warm, dark areas in the home pen) that mimic aspects of a broody hen and possibly reduce fearfulness. The aim of this study was to assess effects of dark brooders on fearfulness, free-range use and behaviour later in life. Another aim was to test the chickens’ preference for shelter type and the effects of overhangs outside of the pop holes to provide a gradual transition to the range. Three production rounds, each with 440 Sasso broiler chickens (110/group), were completed. Chicks were housed indoors from days 0 to 25; per round, two groups had access to a dark brooder, whereas the other two groups had conventional IR lamps. Fearfulness was assessed by the open field (OF) and tonic immobility (TI) tests on days 22 to 24 on 25 chicks/group per round. Birds were then moved to four mobile houses from which they could access both grassland with artificial shelter (AS) and short rotation coppice (SRC). Two of the houses had overhangs extending from the pop holes; these were switched between the four houses weekly. Free-range use and behaviour were observed three times daily from Monday to Friday. Dark brooders did not affect results from the OF or TI test, except for jumps in the OF test which tended to occur less often in brooded chicks. Neither dark brooders (34.9% without v. 31.7% with brooder) nor overhangs (32.5% without v. 34.1% with overhangs) influenced the percentage of chickens outside. Chickens showed a clear preference for SRC, range use increased over time in SRC, and more birds ranged farther from the house in SRC. Behaviours of chickens observed outside were mainly influenced by shelter type, age of the birds and distance from the house. Locomotion tended to occur more in the presence of overhangs. Overall, these results could not confirm the hypothesis that dark brooders would decrease fearfulness and thereby increase free-range use. Overhangs also did not improve free-range use, and neither brooders nor overhangs had considerable impact on behaviour of chickens outside. Chickens clearly preferred dense natural vegetation over AS and ranged farther in it, indicating that this type of shelter is more suitable for slow-growing free-range broilers.