Temporal dynamics of gut microbiota in caged laying hens: a field observation from hatching to end of lay.

Gut health has major implications for the general health of food-producing animals such as the layer birds used in the egg industry. In order to modulate gut microbiota for the benefit of gut health, an understanding of the dynamics and details of the development of gut microbiota is critical. The present study investigated the phylogenetic composition of the gut microbiota of a commercial layer flock raised in cages from hatch to the end of the production cycle. This study also aimed to understand the establishment and development of gut microbiota in layer chickens. Results showed that the faecal microbiota was dominated by phyla Firmicutes and Proteobacteria in the rearing phase, but Bacteroidetes in mid lay and late lay phase. The gut microbiota composition changed significantly during the transfer of the flock from the rearing to the production shed. The richness and diversity of gut microbiota increased after week 6 of the flocks age and stabilized in the mid and late lay phase. The overall dynamics of gut microbiota development was similar to that reported in earlier studies, but the phylogenetic composition at the phylum and family level was different. The production stage of the birds is one of the important factors in the development of gut microbiota. This study has contributed to a better understanding of baseline gut microbiota development over the complete life cycles in layer chickens and will help to develop strategies to improve the gut health. KEY POINTS: • Faecal microbiota of caged hens was dominated by phyla Firmicutes and Proteobacteria in the rearing phase. • The gut microbiota composition changed significantly during the transfer of the flock from the rearing to the production shed. • The richness and diversity of gut microbiota increased after week 6 of the flocks age and stabilized in the mid and late lay phase.

Influence of sunflower meal utilisation on growth performance and digestive tract traits of white strain pullets fed from 29 to 112 d of age.

1. A trial was conducted to study the effects of partial replacement of sunflower meal (SFM) for soybean meal (SBM) on growth performance and gastrointestinal tract traits (GIT) in pullets.2. A total of 600 pullets (29 d of age) was randomly assigned to three dietary treatments and fed for 84 d. The birds were fed a practical diet with a low level of crude fibre (CF; LF) or test diets containing a medium or high level of CF (MF and HF) by partial (50% to 75%) replacement of SBM with SFM. Accordingly, the grower diets contained 29, 40 and 51 g CF/kg, which corresponded to 31, 45 and 59 g CF/kg in developer diets. Each dietary treatment was replicated 8 times (25 pullets per replicate).3. Body weight did not differ significantly among treatments at d 29, 84 and 112 d but increased (P < 0.05) with SFM supplementation at d 54. From 29 to 112 d of age, daily feed and energy intake linearly increased (P < 0.01) with SFM supplementation, but body weight gain and feed conversion ratios were comparable amongst the groups.4. Digestive organ size was not affected by the dietary treatments, but gizzard weight increased in pullets fed MF and HF diets (P < 0.01). Digesta pH in the gizzard, duodenum, jejunum and ileum were reduced linearly (P < 0.01) with SFM supplementation, while a quadratic response was observed for proventriculus pH (P < 0.05).5. Small intestine morphology traits improved with a moderate level of CF intake, whereas no benefit was observed with a high level of CF consumption.6. The results showed that use of SFM up to 140 g/kg can be recommended for pullets fed diets based on corn and soybean meal. However, smaller intestinal absorptive capacity with higher SFM supplementation may occur.

Incidence and associated risk factors of necrotic enteritis in Belgian layer pullet flocks.

Necrotic enteritis (NE) caused by Clostridium perfringens is commonly reported in broilers. Recently, increased NE prevalence in layer breeds was reported in the Indian subcontinent. NE is also frequently observed by veterinary practitioners in Europe, mainly during the pullet rearing phase. In this study, data from layer pullet flocks in Belgium over a 5-year period (2013-2017) were used to assess the incidence of NE and identify potential risk factors for NE in layer pullets. NE was observed in 26% of the layer pullet flocks receiving veterinary intervention. This accounts for an overall estimated NE incidence of 12.3% in Belgian layer pullet flocks. Occurrence of NE was significantly associated with coccidiosis, with flocks being diagnosed with coccidiosis being two-fold more likely to develop NE. Additionally, birds kept in aviary houses were less prone to NE than flocks reared in floor systems or enriched cages. At necropsy, necrotic lesions in the small intestine were comparable to NE in broilers. A single strain of C. perfringens was isolated from the necrotic lesions of three different birds from the same flock; however, no NetB could be detected.

Relative contribution of vertical, within-farm and between-farm transmission of Mycoplasma synoviae in layer pullet flocks.

In this study, the relative contribution of vertical transmission, within-farm transmission and between-farm transmission of Mycoplasma synoviae in layer pullet flocks was quantified using logistic regression analysis. Data from 311 Dutch pullet flocks, of which 172 (55%) were positive for M. synoviae, were included in the study. Also the M. synoviae status of the parent stock of these flocks was included. The M. synoviae status was determined with the M. synoviae rapid plate agglutination test. Data analysis showed that vertical transmission was the most important transmission route for M. synoviae in layers as is demonstrated by an odds ratio of 5.8 (P = 0.000). A positive association with M. synoviae infections was found for layer pullet flocks on a multi-house farm where at least one other flock was M. synoviae-positive compared to single-house farms (odds ratio 3.1, P = 0.022), while a negative association was found when no other M. synoviae-positive flocks were present (odds ratio = 0.2, P = 0.003). No association was found between M. synoviae status of pullet flocks and poultry farm density. Odds ratios were 0.54 (P = 0.288) and 0.34 (P = 0.073), respectively, for medium and highest poultry farm density compared to lowest poultry farm density. This is the first time that the relative contribution of horizontal and vertical transmission of M. synoviae has been quantified. These results can be extrapolated to M. synoviae control in general, and emphasize the importance of M. synoviae control in parent stock and practical channelling.

Bacillus subtilis Strain DSM 29784 Modulates the Cecal Microbiome, Concentration of Short-Chain Fatty Acids, and Apparent Retention of Dietary Components in Shaver White Chickens during Grower, Developer, and Laying Phases.

This study investigated the efficacy of a single strain of Bacillus subtilis (SSB) in modulating the composition of cecal microbiota and its link to the concentration of short-chain fatty acids (SCFA) and apparent retention (AR) of components. A total of 720, 4-week-old Shaver White chicks were allotted to control (CON), 1.1E+08 (low, LSSB), 2.2E+08 (medium, MSSB), or 1.1E+09 (high, HSSB) CFU/kg of diet groups. At grower (10-week), developer (16-week), and laying (28-week) phases, excreta and cecal digesta samples were taken for AR, microbial, and SCFA analyses. Microbial analysis involved high-throughput sequencing of the V3-V4 hypervariable regions of 16S rRNA gene. Bacterial diversity decreased (P < 0.05) at the developer phase as the SSB dose increased; however, a distinct clustering pattern (P < 0.05) of bacterial community was noted. Bacteroides and Faecalibacterium were differentially enriched in the developer for SSB-fed compared to CON-fed birds. Although no differences in microbial diversity were detected in grower and layer phases, different species of Clostridium (XVIII, XIVa, IV, and XIVb)-major butyrate producers-were identified in all phases, with stronger effect sizes for SSB-fed compared to CON-fed birds. Isobutyric acid was elevated in dose response (P = 0.034) in layer phase. In addition, the relative abundances of Alistipes, Lactobacillus, and Bifidobacterium were positively correlated (P < 0.05), with AR of most components for SSB-fed birds in the pullet phase. The results suggested that supplementing chickens' diet with B. subtilis DSM 29784 may selectively enrich beneficial bacterial communities, which in turn are critical in promoting the growth and performance of hens.IMPORTANCE In egg-laying chickens, the trend in the move away from the cage to alternative housing systems and restriction in antimicrobial use requires alternative approaches to maintain health and prevent diseases. There is increased research and commercial interest toward alternative gut health solutions while improving the performance and product safety in poultry production systems. One such approach, in recognition of the importance of the gut microbial community, is the use of microbes as feed supplements (such as probiotics). Unlike meat-type chickens, studies assessing the efficacy of such microbial supplements are limited for egg-laying chickens. Thus, by conducting a comprehensive assessment of the hen microbiota in response to various levels of B. subtilis DSM 29784 during the pullet phase (grower and developer) and the layer phase, the present study demonstrates the importance of direct-fed microbes in modulating gut microbiome, which may relate to improved performance efficiency in the pullet and layer phases.

Nitrogen maintenance requirements and potential for nitrogen retention of pullets in growth phase.

Experiments were conducted to estimate daily N maintenance requirements (NMRs) and the genetic potential for daily N retention (NRmax T) of pullets in growth phase. Three nitrogen balance trials were conducted, and a total of 48 Hy-line W-36 pullets were used in each trial in age periods (starter: 14-28, grower: 56-70 and developer: 98-112 days). The treatments consisted of six graded levels of nitrogen in the diets (L1 = 8, L2 = 16, L3 = 24, L4 = 32, L5 = 40 and L6 = 48 g N/kg of feed), formulated using the dilution technique. The regression analyses between nitrogen intake and nitrogen excretion were performed to fit the exponential function and to determine the NMR. The daily NMRs that were estimated at 294, 331 and 355 mg/BWkg 0.67 for the initial, grower and developer periods, respectively, were applied for further calculation of NRmax T as the threshold value of the function between N intake and daily N balance. The NRmax T was estimated by a statistical procedure following several iteration steps by the Levenberg-Marquardt algorithm until the sum of the squares of the residual was minimized. The NRmax T was estimated at 3,200, 2,633 and 1,826 mg/BWkg 0.67 for starter, grower and developer periods respectively. The determined model parameters were the precondition for modelling of the amino acid requirement based on an exponential N-utilization model and depended on performance and dietary amino acid efficiency. This procedure will be further developed and applied in the subsequent study.

Fowl aviadenovirus serotype 1 confirmed as the aetiological agent of gizzard erosions in replacement pullets and layer flocks in Great Britain by laboratory and in vivo studies.

An investigation into the aetiology and pathogenesis of adenoviral gizzard erosion has been conducted following three natural outbreaks affecting one flock of 6-week-old replacement pullets and two consecutive placements of free range layers at the age of 21 and 23 weeks. Affected flocks showed increased mortality (0.12-0.30% per week), and gizzard lesions were consistent with fowl aviadenovirus (FAdV) involvement. To substantiate the initial findings, a selection of archived formalin-fixed paraffin-embedded gizzard samples from another 12 pullet and layer flocks, for which macroscopic and histopathological diagnosis of the disease were recorded in Great Britain during the period 2009-2016, were also investigated. In situ hybridization (ISH), virology and/or PCR confirmed the presence of FAdV species-A, serotype-1 (FAdV-A, FAdV-1) DNA in gizzard samples of all 15 cases investigated. Co-infections with additional FAdV serotypes including FAdV-8a were detected by serology and/or virology in two of the pullet flocks. However, species-specific in situ hybridization revealed that pathological changes of affected gizzards were only associated with the detection of FAdV-A. A subsequent in vivo study infecting 21-day-old SPF pullets with FAdV-1 or FAdV-8a strains isolated from the 6-week-old replacement pullets revealed characteristic pathomorphological changes only in the gizzards from birds infected with FAdV-1. While infection with FAdV-8a was confirmed by virology and serology, infected SPF birds did not develop pathomorphological changes. Therefore, the aetiological involvement of the isolated FAdV-8a in the development of adenoviral gizzard erosion in commercial pullets has been ruled out.

Determination of body width in brown and white layer pullets by image analyses.

1. Specific legal requirements for keeping pullets are not available in the European Union. However, two of the most important rearing factors for pullets are sufficient perching and feeder space. Both factors represent horizontal space dimensions which derive from the body width of the birds. 2. The body width of two strains of layer pullets (brown (BL) and white (WL) layer pullets) based on the measurement of distances in digital images was conducted on front-view digital photographs of BL and WL pullets taken at 8, 12 and 19 weeks of life. 3. Depending on live weight, age and body position, BL pullets measured an average body width between 10.70 ± 1.10 and 13.96 ± 1.11 cm. The width of WL pullets ranged from 10.30 ± 0.86 to 13.00 ± 1.14 cm. 4. Compared with WL, BL pullets occupied more horizontal space during rearing. Age influenced the body width of BL and WL pullets at the end of rearing. The tested body positions of the pullets did not affect the measured body width. 5. The biometric data obtained in this study are a useful basis for developing legal requirements for pullets, especially for defining minimum perch width and feeder space allowances.

High genetic diversity among extraintestinal Escherichia coli isolates in pullets and layers revealed by a longitudinal study.

BACKGROUND: Various information about the genetic diversity of Escherichia coli isolates from chickens are available but a detailed epidemiological investigation based upon isolates obtained from interrelated pullet and layer flocks is still missing. Therefore, in the course of a longitudinal epidemiological study on pullets and layers, 144 E. coli isolates from chickens with or without pathological lesions of the reproductive tract were serotyped and genotyped with pulsed-field gel electrophoresis (PFGE). These isolates were collected during rearing, peak and at the end of production. The actual study is the first of its kind so as to elucidate genetic relatedness among extraintestinal E. coli isolated from chickens with varying pathological conditions in interrelated layer farms/flocks at different stages of rearing. RESULTS: Serotyping revealed that 63.19 % of the isolates could not be assigned to any of the three serotypes tested whereas 30.55 % of the isolates belonged to serotype O1:K1, 4.86 % to O2:K1 and 1.38 % to O78:K80. After macrorestriction digest with XbaI, 91.66 % of the isolates were typeable resulting in 96 distinct PFGE profiles. Among them, five PFGE types included isolates collected from diseased chickens as well as from birds without pathological lesions. This finding shows that pathogenicity of E. coli in layers seems to be largely influenced by concurrent susceptibility factors. Furthermore, in six out of eight cases where two isolates were collected from each of eight birds, different PFGE types were found in the same or different organs of the same bird. The existence of predominant or persistent E. coli genotypes was only observed in two cases. CONCLUSIONS: It is concluded that extraintestinal E. coli genotypes and serotypes in pullets and layers are heterogenous and also do not maintain a single clonality within the same bird. The facts that E. coli strains did not show any definite clonal population structure based on geographical region, age of the host and pathological lesions should have relevance in further epidemiological studies and control strategies.

Effect of wet-cold weather transportation conditions on thermoregulation and the development of accidental hypothermia in pullets under tropical conditions.

The present study examines onboard thermal microclimatic conditions and thermoregulation of pullets exposed to accidental hypothermia during wet-cold weather transportation conditions, and the effect of rewarming on colonic temperature (CT) of the birds immediately after transportation. A total of 2200 pullets were transportation for 5 h in two separate vehicles during the nighttime. The last 3 h of the transportation period was characterized by heavy rainfall. During the precipitation period, each vehicle was covered one fourth way from the top-roof with a tarpaulin. The onboard thermal conditions inside the vehicles during transportation, which comprised ambient temperature and relative humidity were recorded, while humidity ratio and specific enthalpy were calculated. The CT of the birds was recorded before and after transportation. During transportation, onboard thermal heterogeneity was observed inside the vehicles with higher (p < 0.05) values in the front and center, and lower values recorded at the air inlets at the sides and rear planes. The CT values recorded in birds at the front and center planes were between 42.2 and 42.5 °C, indicative of mild hypothermia; while lower CT values between 28 and 38 °C were recorded at the sides and rear planes, indicative of mild to severe hypothermia. Several hours of gradual rewarming returned the CT to normal range. The result, for the first time, demonstrated the occurrence of accidental hypothermia in transported pullets under tropical conditions and a successful rewarming outcome. In conclusion, transportation of pullets during wet weather at onboard temperature of 18-20 °C induced hypothermia on birds located at the air inlets, which recovered fully after several hours of gradual rewarming.

Welfare and performance in layers following temporary exclusion from the litter area on introduction to the layer facility.

When introduced to the laying facility, pullets are sometimes temporarily excluded from the litter area in order to help them locate food and water, and to prevent floor-laid eggs. This procedure is not permitted in Sweden, because it involves denying access to both litter and space, which may have a negative effect on bird welfare. The present study investigated how the welfare and performance of layers were affected by this temporary exclusion on introduction of hens to the laying facility. The study included 600 floor-reared Dekalb White layers obtained at 16 wk age and housed in 6 groups of 100 in a conventional single-tier floor-laying system. Birds were either given full access to the litter area during the whole study or were excluded from the litter area during the first 2 wk after transfer to the laying facility. From 18 to 72 wk age, birds in both treatments had full access to the litter area. Excluding birds from the litter area for 2 wk resulted in better feather cover and reduced fearfulness, according to novel object and tonic immobility tests. Furthermore, birds initially excluded from the litter area produced eggs with a lower proportion of shell irregularities than birds with full access to the litter area throughout. No difference was found in corticosterone metabolites in droppings rate of lay, mortality, or proportion of floor-laid eggs. In conclusion, none of the parameters studied indicated that the welfare of laying hens was compromised by temporary exclusion from the litter area on introduction to the laying facility. In fact, some of the data suggested that bird welfare had improved.

Effect of rearing environment on bone growth of pullets.

Alternative housing systems for laying hens provide mechanical loading and help reduce bone loss. Moreover, achieving greater peak bone mass during pullet phase can be crucial to prevent fractures in the production period. The aim of this study was to determine the housing system effects on bone quality of pullets. Tibiae and humeri of White Leghorn pullets reared in conventional cages (CCs) and a cage-free aviary (AV) system were studied. At 16 wk, 120 birds at random from each housing system were euthanized. Right and left tibiae and humeri were collected and further analyzed. Cortical bone density and thickness were measured using computed tomography. Periosteal and endosteal dimensions were measured at the fracture site during mechanical testing. At 4, 8, 12, and 16 wk, serum concentrations of osteocalcin and hydroxylysyl pyridinoline were analyzed as markers of bone formation and resorption. Cortical bone density was higher (P<0.05) in humeri of AV pullets, and tibiae were denser (P<0.05) for AV pullets in the distal section of the bone compared to CC pullets. Ash content was higher (P<0.05) in AV humeri with no difference in tibiae ash content. Tibiae and humeri of AV pullets had a thicker cortex than the CC pullets (P<0.05). Additionally, the tibiae and humeri of AV pullets had greater (P<0.05) second moment of areas than the CC pullets. While some bone material properties between groups were different (P<0.05), the differences were so small (<7%) that they likely have no clinical significance. Serum osteocalcin concentrations were not different between the treatments, but hydroxylsyl pyridinoline concentrations were higher in CC pullets at 12 wk compared to the AV pullets and the effect reversed at 16 wk (P<0.05). These findings indicate that tibiae and humeri respond differently to load bearing activities during growth. The improved load bearing capability and stiffness in bones of AV pullets were related to increased cross-sectional geometry.

Innate immune response of pullets fed diets supplemented with prebiotics and synbiotics.

Prebiotics and synbiotics are considered to be among the most promising replacements for in-feed antibiotic growth promoters (AGP) in poultry feed. The current study was designed to study the effect of Bacitracin methylene disalicylate (BMD) (Control), yeast-derived carbohydrates (YDC), and a blend of YDC and probiotics [Lactobacillus acidophilus, Lactobacillus casei, Streptococcus faecium, Bacillus subtilis, and YDC] (SNB) in the performance and innate immune response of pullets. Feed intake and BW were measured on a weekly basis. At the end of the study (d 21), 10 birds/treatment were sacrificed by cervical dislocation and ileum, cecal tonsil, and spleen samples were collected for gene expression analysis. No significant difference (P > 0.05) in feed intake and G:F was observed among treatments. In the second and third wk age, higher BW gain was observed in SNB treatment compared to control and both control and YDC treatments, respectively. Expression of TLR2b was upregulated in YDC and SNB in the ileum, and in SNB in the spleen (P < 0.05). Expression of TLR4 was downregulated in SNB in the cecal tonsil. Expression of TLR21 was downregulated in YDC in the ileum, while it was upregulated in SNB in the spleen (P < 0.05). In the ileum, YDC resulted in downregulated IL-12p35, CxCLi2, and IL-13, and SNB resulted in upregulated IL-6, interferon (IFN)-γ, and IL-4 (P < 0.05). In the cecal tonsil, YDC resulted in upregulated IL-12p35, IL-2, IL-13 and IL-10, and SNB resulted in downregulated IL-2 and upregulated IL-13 and IL-10 (P < 0.05). In the spleen, YDC resulted in dowregulated IL-2 and CxCLi2, and SNB resulted in upregulated IL-6, IFN-γ, IL-4, and IL-10 (P < 0.05). In conclusion, no change in performance was observed. Innate immune response analysis showed SNB with a more potent effect compared to YDC where the former showed a balanced T-helper (Th)-1/Th-2 response locally and a more Th-2-dependent response systemically; SNB might provide a more beneficial immune modulation with maintaining immune homeostasis, which was observed in a strong IL-10 response.

Inclusion of fiber in diets for brown-egg laying pullets: Effects on growth performance and digestive tract traits from hatching to 17 weeks of age.

We investigated the effects of fiber inclusion in the diet on growth performance and digestive traits in pullets from hatching to 17 wk of age. The control diets of the 3 feeding periods (0 to 5 wk, 5 to 10 wk, and 10 to 17 wk) were based on corn and soybean meal and did not include any additional fiber source. The experimental diets included 2 or 4% of cereal straw or sugar beet pulp (SBP) at the expense (wt:wt) of the control diet. From 0 to 5 wk of age, fiber inclusion did not affect pullet performance. From hatch to 17 wk of age, the inclusion of straw had little effect on pullet performance but the inclusion of 4% SBP reduced (ADG) (P < 0.05) and reduced feed conversion ratio (FCR; P < 0.001). Pullets fed straw had greater ADG (P < 0.05) and better energy conversion ratio (P < 0.01) than pullets fed SBP. An increase in fiber from 2 to 4% reduced FCR (P < 0.05). Body weight uniformity was not affected by diet. Fiber inclusion increased the relative weight (% BW) of the gizzard at 5 wk (P = 0.056) and 10 wk (P < 0.01) of age, but no differences were detected between fiber sources. At same ages, the relative length (cm/kg BW) of the pullets (P = 0.058 and P < 0.01, respectively) and tarsus (P = 0.079 and P < 0.05, respectively) was higher in pullets fed SBP than in pullets fed straw. Fiber inclusion, however, did not affect any of these traits at 17 wk of age. In summary, the inclusion of 2% straw at the expense (wt:wt) of the whole diet did not affect pullet performance at 17 wk of age. An increase in the level of straw from 2 to 4% reduced FCR but did not affect ADG. The inclusion of SBP, however, reduced pullet growth, with effects being more pronounced at the higher level.

Development and Evaluation of Mycoplasma gallisepticum Challenge Model in Layer Pullets.

Manufacturers of Mycoplasma gallisepticum (MG) modified live vaccines usually recommend a single application at 8 wk of age. This makes 12-16-wk-old layer pullets suitable for challenge studies intended to evaluate these vaccines. Numerous challenge models in different poultry species and ages have been reported. However, there is not an established layer pullet challenge model for this age. The aim of this study is to develop a suitable challenge model in 12-wk-old layer pullets. MG Rlow strain was used as the challenge strain, and its ability to induce clinical signs and lesions in 12-wk-old Hy-Line W-36 layer pullets was evaluated. Three different doses (low, 7.95 × 104 color-changing units [CCU]/bird; medium, 7.95 × 106 CCU/bird; and high, 7.95 × 108 CCU/bird) via three different routes (eye drop, fine spray, and contact infection) were compared and evaluated using different parameters. At 14 days post-challenge, there were no mortalities in any of the groups throughout the study. Layer pullets directly challenged with the high dose via the fine spray route showed the clearest and most consistent results (clinical signs, positive quantitative real-time PCR [qPCR], seroconversion, air sac scoring, and histopathological changes of the tracheal mucosa). Medium and low challenge doses applied via fine spray or eye drop did not show consistent results. Rlow strain was able to spread to the contact infection birds, as confirmed by the positive qPCR results; however, none of the contact-infected birds showed any clinical signs or gross or microscopic lesions. Our results suggest that a high dose (7.95 × 108 CCU/bird) administered through a fine spray route is the model of choice in any future MG vaccine evaluation trials in 12-wk-old layer pullets.

Nota de investigación- Desarrollo y evaluación del modelo de desafío para Mycoplasma gallisepticum en pollitas de postura. Los fabricantes de vacunas vivas modificadas contra Mycoplasma gallisepticum (MG) suelen recomendar una sola aplicación a las ocho semanas de edad. Esto hace que las pollitas de postura de 12 a 16 semanas de edad sean adecuadas para estudios de desafío destinados a evaluar estas vacunas. Se han reportado numerosos modelos de desafío en diferentes especies y edades de aves de corral. Sin embargo, no existe un modelo de desafío establecido para pollitas de postura de esta edad. El objetivo de este estudio fue desarrollar un modelo de desafío adecuado en pollitas ponedoras de 12 semanas de edad. Se utilizó la cepa Rlow de Mycoplasma gallisepticum como cepa de desafío y se evaluó su capacidad para inducir signos clínicos y lesiones en pollitas ponedoras Hy-Line W-36 de 12 semanas de edad. Tres dosis diferentes (baja, 7.95 × 104 unidades de cambio de color [CCU]/ave; media, 7.95 × 106 CCU/ave; y alta, 7.95 × 108 CCU/ave) a través de tres rutas diferentes (gota en el ojo, aerosol con gota fina e infección por contacto) se compararon y evaluaron utilizando diferentes parámetros. A los 14 días posteriores al desafío, no hubo mortalidades en ninguno de los grupos durante todo el estudio. Las pollitas de postura expuestas directamente a la dosis alta a través de la ruta de aerosol con gota fina mostraron los resultados más claros y consistentes (signos clínicos, PCR cuantitativa en tiempo real [qPCR] positiva, seroconversión, puntuación de lesiones en los sacos aéreos y cambios histopatológicos de la mucosa traqueal). Las dosis de desafío medias y bajas aplicadas mediante aerosol con gota fina o gota en el ojo no mostraron resultados consistentes. La cepa Rlow pudo propagarse a las aves infectadas por contacto, como lo confirmaron los resultados positivos de qPCR; sin embargo, ninguna de las aves infectadas por contacto mostró signos clínicos o lesiones macroscópicas o microscópicas. Estos resultados sugieren que una dosis alta (7.95 × 108 CCU/ave) administrada a través de una ruta de aerosol con gota fina es el modelo de elección en cualquier ensayo futuro de evaluación de vacunas para M. gallisepticum en pollitas de postura de 12 semanas de edad.

Response of broiler breeder pullets when fed hydrolyzed whole yeast from placement to 22 wk of age.

The study examined the effects of feeding broiler breeder pullets hydrolyzed whole yeast (HY) from hatch to 22 wk of age (WOA). A total of 524-day-old Ross 708 pullets were placed in floor pens (∼24 birds/pen) for the starter (0-4 WOA) and grower (5-18 WOA) phases, then transferred to the egg production facility and redistributed to ∼20 birds/pen for the prelay phase (19-22 WOA). Two diets were allocated to pens (0-18 WOA; n = 11) and (19-22 WOA; n-12). The diets were a control corn and soybean meal diet formulated to meet specifications and control plus 0.05% HY (HY). Birds had ad libitum access to feed in the first week and daily feed allocation based on pen BW from 2 WOA. Birds had free access to water throughout the trial. Body weight (BW) and uniformity (BW CV) were monitored. Boosters for infectious bronchitis and New Castle disease vaccines were administered at 18 WOA, and samples of pullets bled for antibody titer 5-day later. One pullet/pen was randomly selected, weighed, bled for plasma biochemistry, and necropsied for organ weights, ceca digesta for short-chain fatty acids (SCFA), and leg bones morphometry. In the starter and grower phases, birds fed HY were lighter and gained less (P < 0.05) than control birds. However, there were no diet effects (P > 0.05) on growth, the BW prelay phase, or BW uniformity throughout the trial. There were no (P > 0.05) diet effects on breast, gastrointestinal, liver and bursa weights, serum antibody titers, plasma biochemistry, SCFA and bone attributes. However, pullets fed HY had heavier (P = 0.047) spleen and tended to have lower (P = 0.080) plasma concentrations of aspartate aminotransferase (AST) relative to control pullets. In conclusion, the parameters assessed showed no negative consequences of feeding HY to broiler breeder pullets. However, effects on the spleen and plasma AST may indicate modest modulation of immunity and metabolism. The impact of the provision of HY during broiler breeder pullet phase on reproductive performance and chick quality should be investigated.

Graded levels of Eimeria infection linearly reduced the growth performance, altered the intestinal health, and delayed the onset of egg production of Hy-Line W-36 laying hens when infected at the prelay stage.

The aim of this experiment was to investigate how different levels of Eimeria infection affect the performance, intestinal health, oxidative status, and egg production of Hy-Line W-36 pullets and laying hens. Three hundred and sixty Hy-Line W-36 pullets, aged 15 wk, were randomly distributed into 5 treatment groups, each comprising 6 replicates and a nonchallenged control. At 15 wk, pullets were inoculated with different levels of mixed Eimeria species as high-dose, medium-high, medium-low, and low-dose treatments. The growth performance and average daily feed intake (ADFI) were measured from 0- to 18-days postinoculation (DPI), whereas hen day egg production (HDEP) was recorded from wk 19. The markers of gastrointestinal health and oxidative status were measured at 6 DPI, 14 DPI, and 23 wk of age. The findings revealed a significant linear reduction in growth performance in response to increased Eimeria challenge dosage on 6 and 14 DPI (P < 0.0001, P-L < 0.0001). An interaction between the graded level of Eimeria infection and DPI was observed for ADFI. The challenged pullets showed a reduction in ADFI starting at 4 DPI, which persisted until 14 DPI, when ADFI recovered back to normal. The most significant drop in feed intake was observed in 6 DPI in all the Eimeria-infected groups. The markers of gastrointestinal health (gastrointestinal permeability and tight junction proteins) were upregulated in challenged pullets because of infection, whereas the relative mRNA expression of key nutrient transporters was downregulated following infection on 6 and 14 DPI (P < 0.05). As a result of an infection on 6 DPI, the oxidative equilibrium was shifted toward the oxidative stress, and at the same time, upregulation of proinflammatory and inflammatory cytokines was observed (P < 0.05). An interaction between the Eimeria challenge dosage and bird age was observed for HDEP (P = 0.0427). The pullets infected with Eimeria started to lay eggs later than the Control birds. However, the HDEP of the challenged groups became similar to Control only at wk 22, 3 wk after laying eggs. In conclusion, coccidiosis reduced growth performance, altered gastrointestinal health, induced oxidative stress, and delayed egg production when infected at the prelay stage of pullets and negatively impacted the laying hens' overall performance.

Making the most of life: environmental choice during rearing enhances the ability of laying hens to take opportunities.

Introduction: The potential of aviary housing for improving laying hen (Gallus gallus domesticus) welfare will be constrained if rearing conditions limit the hens' behavioral ability to take opportunities. Incorporating theories on developmental plasticity and animal agency, this study aimed to determine: (1) whether a choice of litter and perch types during rearing would promote long-lasting changes in use of novel locations and resources, and (2) the influence of timing of choice provision. Methods: Laying hen chicks were assigned to either a "Single-choice" (one litter and perch type) or "Multi-choice" environment (four litter and perch types) during "Early" (day 1-week 4) and "Late" rearing (week 5-15). The environments were switched in half of the 16 pens in week 5, resulting in a 2 × 2 factorial design with four choice environment by period combinations. The allocation of perch and litter space was the same across all treatment combinations. In week 16, all groups were moved to standard aviary laying pens (Laying period, week 16-27). Results: When first moved to the laying pens, hens with Multi-choice in either or both rearing periods were quicker to spread out in their pen than hens with Single-choice throughout rearing. Multi-choice in Early rearing also reduced the latency to use novel elevated structures (perches and nests) in the laying pens. Multi-choice during Late rearing increased success in finding and consuming hidden mealworms (tested in weeks 9-17) and increased the proportion of eggs laid on elevated nesting trays. Numerically, hens switched from Multi-choice to Single-choice in week 5 used the outdoor range less than hens switched from Single-choice to Multi-choice. Discussion: These results support the hypothesis that offering multiple resource choices during rearing improves hens' ability to make the most of new opportunities by being more proactive in exploring and exploiting newly available resources. In different opportunity challenges, hens showed positive outcomes in response to choice during Early, Late or both stages of rearing, suggesting that best results can be obtained by offering environmental choice throughout rearing.

Dynamic responses of systemic immunity and splenic inflammation to long-term cyclic high-temperature exposure in growing pullets and laying hens.

Two trials were conducted to draw the phase-response curve of productive and immunological variables in heat-exposed layer chickens at different ages (71 to 130 d, and 211 to 270 d). Birds were acclimated to the following conditions for 60 d: constant optimal ambient temperature at 24°C and high ambient temperature at 34°C for 8 h/d (10:00-18:00). Data collection and biochemical measurements were performed every 10 d. In both age ranges, high temperature favored the innate immunity (P < 0.01) at the cost of performance (P < 0.05) during a given period, including the relative abundance of B and T-helper lymphocytes, lymphocyte proliferation ratio (B and T lymphocytes), and serum immunoglobulin contents (IgG and IgM) in the peripheral blood, as well as splenic expression of inflammation-related genes (iNOS, TLR-4, TNF-α, IL-6, and INF-γ). Compared with laying hens, growing pullets showed a time-delayed activation of immune response following heat challenge, and had no immunosuppression up to the end of exposure. Overall, the immune system of layer birds has a trade-off with production tissues in a hot environment, and exhibits distinct age-range-specific responses of acclimatization.

The Effect of Short-term Classical Music stimulus on Behavior and Tonic Immobility Reaction of Pullets.

The purpose of this study was to investigate the effect of short-term stimulation of classical music on the behavior of pullets and to explore whether classical music as an auditory enrichment factor reduces the fear level in pullets. One hundred and twenty 10-weeks'old Roman white pullets were randomly divided into two treatments of which one group was exposed to classic music (M), and another one was the control group (N). The music was played during 8:00-18:00 every day for 7 consecutive days. The behavior of the focal animals was observed from 11:00 to13:00 every day for 7 days. The results showed that during the observation period, the pullets in group M had more comforting (P < .05) and preening (P < .05), but less aggressive (P < .01) and feather-pecking (P < .01) behaviors than those in group N. No significant difference was found in other behaviors and the duration of tonic immobility between the two groups. Therefore, auditory enrichment as a means of environmental enrichment can increase the welfare level of pullets to a certain extent.