961 resultados para Commercial egg-laying
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The PhD project was focused on the study of the poultry welfare conditions and improvements. The project work was divided into 3 main research activities. A) Field evaluation of chicken meat rearing conditions kept in intensive farms. Considering the lack of published reports concerning the overall Italian rearing conditions of broiler chickens, a survey was carried out to assess the welfare conditions of broiler reared in the most important poultry companies in Italy to verify if they are in accordance with the advices given in the European proposal COM (2005) 221 final. Chicken farm conditions, carcass lesions and meat quality were investigated. 1. The densities currently used in Italy are in accordance with the European proposal COM 221 final (2005) which suggests to keep broilers at a density lower than 30-32 kg live weight/m2 and to not exceed 38-40 kg live weight/m2. 2. The mortality rates in summer and winter agree with the mortality score calculated following the formula reported in the EU Proposal COM 221 final (2005). 3. The incidence of damaged carcasses was very low and did not seem related to the stocking density. 4. The FPD scores were generally above the maximum limit advised by the EU proposal COM 221 final (2005), although the stocking densities were lower than 30-32 kg live weight per m2. 5. It can be stated that the control of the environmental conditions, particularly litter quality, appears a key issue to control the onset of foot dermatitis. B) Manipulation of several farm parameters, such litter material and depth, stocking density and light regimen to improve the chicken welfare conditions, in winter season. 1. Even though 2 different stocking densities were established in this study, the performances achieved from the chickens were almost identical among groups. 2. The FCR was significantly better in Standard conditions contrarily to birds reared in Welfare conditions with lower stocking density, more litter material and with a light program of 16 hours light and 8 hours dark. 3. In our trial, in Standard groups we observed a higher content of moisture, nitrogen and ammonia released from the litter. Therefore it can be assumed that the environmental characteristics have been positively changed by the improvements of the rearing conditions adopted for Welfare groups. 4. In Welfare groups the exhausted litters of the pens were dryer and broilers showed a lower occurrence of FPD. 5. The prevalence of hock burn lesions, like FPD, is high with poor litter quality conditions. 6. The combined effect of a lower stocking density, a greater amount of litter material and a photoperiod similar to the natural one, have positively influenced the chickens welfare status, as a matter of fact the occurrence of FPD in Welfare groups was the lowest keeping the score under the European threshold of the proposal COM 221 final(2005). C) The purpose of the third research was to study the effect of high or low stocking density of broiler chickens, different types of litter and the adoption of short or long lighting regimen on broiler welfare through the evaluation of their productivity and incidence of foot pad dermatitis during the hot season. 1. The feed efficiency was better for the Low Density than for High Density broilers. 2. The appearance of FPD was not influenced by stocking density. 3. The foot examination revealed that the lesions occurred more in birds maintained on chopped wheat straw than on wood shaving. 4. In conclusion, the adoptions of a short light regimen similar to that occurring in nature during summer reduces the feed intake without modify the growth rate thus improving the feed efficiency. Foot pad lesion were not affected neither by stocking densities nor by light regimens whereas wood shavings exerted a favourable effect in preserving foot pad in good condition. D) A study was carried out to investigate more widely the possible role of 25-hydroxycholecalciferol supplemented in the diet of a laying hen commercial strain (Lohmann brown) in comparison of diets supplemented with D3 or with D3 + 25- hydroxycholecalciferol. Egg traits during a productive cycle as well as the bone characteristics of the layers have been as well evaluated to determine if there the vitamin D3 may enhance the welfare status of the birds. 1. The weight of the egg and of its components is often greater in hens fed a diet enriched with 25-hydroxycholecalciferol. 2. Since eggs of treated groups are heavier and a larger amount of shell is needed, a direct effect on shell strength is observed. 3. At 30 and at 50 wk of age hens fed 25 hydroxycholecalciferol exhibited greater values of bone breaking force. 4. Radiographic density values obtained in the trial are always higher in hens fed with 25-hydroxycholecalciferol of both treatments: supplemented for the whole laying cycle (25D3) or from 40 weeks of age onward (D3+25D3).
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Antimicrobial resistance is an emerging concern to public health, and food-producing animals are known to be a potential source for transmission of resistant bacteria to humans. As legislation of the European Union requires to ban conventional cages for the housing of laying hens on the one hand, and a high food safety standard for eggs on the other hand, further investigations about the occurrence of antimicrobial resistance in alternative housing types are required. In this study, we determined antimicrobial resistance in indicator bacteria from 396 cloacal swabs from 99 Swiss laying hen farms among four alternative housing types during a cross-sectional study. On each farm, four hens were sampled and exposure to potential risk factors was identified with a questionnaire. The minimal inhibitory concentration was determined using broth microdilution in Escherichia coli (n=371) for 18 antimicrobials and in Enterococcus faecalis (n=138) and Enterococcus faecium (n=153) for 16 antimicrobials. All antimicrobial classes recommended by the European Food Safety Authority for E. coli and enterococci were included in the resistance profile. Sixty per cent of the E. coli isolates were susceptible to all of the considered antimicrobials and 30% were resistant to at least two antimicrobials. In E. faecalis, 33% of the strains were susceptible to all tested antimicrobials and 40% were resistant to two or more antimicrobials, whereas in E. faecium these figures were 14% and 39% respectively. Risk factor analyses were carried out for bacteria species and antimicrobials with a prevalence of resistance between 15% and 85%. In these analyses, none of the considered housing and management factors showed a consistent association with the prevalence of resistance for more than two combinations of bacteria and antimicrobial. Therefore we conclude that the impact of the considered housing and management practices on the egg producing farms on resistance in laying hens is low.
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We investigated the effects of different dietary vitamin D regimen on selected blood parameters in laying hens. Supplementation with vitamin D-3 only was compared with a combination of vitamin D-3 and its metabolite 25-hydroxy-cholecalciferol (25(OH)D-3). Blood concentrations of total calcium, phosphate and 25 (OH)D-3 were determined. Four thousand one-day-old LSL chicks were split in two treatment groups and distributed to eight pens. The control group was given a commercial animal diet containing 2800 IU synthetic vitamin D-3 in the starter feed and 2000 IU synthetic vitamin D-3 in the pullet feed. The experimental group was fed the same commercial diet in which half the synthetic vitamin D-3 content had been substituted with 25(OH)D-3 (Hy center dot D (R)). At 18 weeks of age, pullets were transferred to the layer house. At the ages of 11, 18 and 34 weeks, between 120 and 160 blood samples were collected from both the control and the experimental groups, respectively. The experimental group had higher levels of 25 (OH)D-3 than the control group at all three ages. Serum calcium levels did not differ between the treatment groups at any age. With the onset of laying, calcium levels rose significantly. Whereas blood serum concentration at 18 weeks was 3 mmol/L in both treatment groups, it increased to 8.32 mmol/L in the control group and to 8.66 mmol/L in the experimental group at week 34. At weeks 11 and 34, phosphate was significantly lower in the experimental group. In conclusion, HyD (R) significantly affected serum phosphate and 25(OH)D-3 levels. No effects of (25(OH)D-3 supplementation on performance, shell quality and fractures of keelbones were found.
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Low rates of nest acceptance by laying hens are a major problem in commercial poultry farming operations with aviary systems, leading to costly manual collection and cleaning of mislaid eggs. To gain knowledge about factors affecting nest use, laying hens' preferences for different nest locations were tested. Nests are normally installed at one of two sites: against a wall of the hen house or integrated into one tier of the aviary rack The preferences of laying hens for different nest sites have never been examined under commercial conditions. The aim of this study is to investigate whether behavioural differences can be detected between the different nest sites. The study consists of two consecutive trials involving 5027 Lohmann Selected Leghorn hens (LSL) and 601 layer hybrids selected for extensive housing conditions (EXT). The hens were randomly assigned to eight compartments per trial in groups of 355-360 LSL or 300 EXT in a laying hen house. Four compartments were equipped with a Volito Voletage (R) aviary system (VV), and four were equipped with a Rihs Bolegell (R) aviary system (RB), both of which contained either integrated or wall-placed nests when the experiments started. A strongly balanced crossover design with four periods was used. At 36, 44 and 52 weeks of age, the nest site in four out of the eight compartments was switched. Before each change, the fronts of half of the nests were videotaped during the light period, and the behaviour throughout the main laying period was analysed. Furthermore, the numbers of nest eggs and mislaid eggs in each compartment were recorded every day. No differences in the number of mislaid eggs between the two nest sites could be detected, except at the age of 20/21 weeks when hens in VV aviaries mislaid more eggs when nests were integrated (P = 0.0012). More hens stood simultaneously in front of the integrated nests than in front of wall-placed nests (P = 0.015). Activity of the laying hens increased (P = 0.0073), and stationary behavioural patterns declined (P = 0.0093), when the nests were placed by the wall. Hens inspected integrated nests for a longer duration than wall-placed nests, but wall-placed nests were visited more frequently. In addition to the nest site, the width of the platform in front of the nest influenced laying hen behaviour. Compared with narrower platforms, balance movements decreased on wider ones. Additionally, the platform design had to be taken into account as well, given that hens could not stand or walk as securely on wooden slats as on a grid floor. (C) 2011 Elsevier B.V. All rights reserved.
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Fractures of the keel bone, a bone extending ventrally from the sternum, are a serious health and welfare problem in free range laying hens. Recent findings suggest that a major cause of keel damage within extensive systems is collisions with internal housing structures, though investigative efforts have been hindered by difficulties in examining mechanisms and likely influencing factors at the moment of fracture. The objectives of this study were to develop an ex vivo impact protocol to model bone fracture in hens caused by collision, to assess impact and bird-related factors influencing fracture occurrence and severity, and to identify correlations of mechanical and structural properties between different skeletal sites. We induced keel bone fractures in euthanized hens using a drop-weight impact tester able to generate a range of impact energies, producing fractures that replicate those commonly found in commercial settings. The results demonstrated that impact energies of a similar order to those expected in normal housing were able to produce fractures, and that greater collision energies resulted in an increased likelihood of fractures and of greater severity. Relationships were also seen with keel's lateral surface bone mineral density, and the peak reactive force (strength) at the base of the manubrial spine. Correlations were also identified between the keel and long bones with respect to both strength and bone mineral density. This is the first study able to relate impact and bone characteristics with keel bone fracture at the moment of collision. Greater understanding of these relationships will provide means to reduce levels of breakage and severity in commercial systems.
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INTRODUCTION The omega-3 and omega-6 polyunsaturated fatty acids (PUFAs) are the immediate precursors to a number of important mediators of immunity, inflammation and bone function, with products of omega-6 generally thought to promote inflammation and favour bone resorption. Western diets generally provide a 10 to 20-fold deficit in omega-3 PUFAs compared with omega-6, and this is thought to have contributed to the marked rise in incidence of disorders of modern human societies, such as heart disease, colitis and perhaps osteoporosis. Many of our food production animals, fed on grains rich in omega-6, are also exposed to a dietary deficit in omega-3, with perhaps similar health consequences. Bone fragility due to osteoporotic changes in laying hens is a major economic and welfare problem, with our recent estimates of breakage rates indicating up to 95% of free range hens suffer breaks during lay. METHODS Free range hens housed in full scale commercial systems were provided diets supplemented with omega-3 alpha linolenic acid, and the skeletal benefits were investigated by comparison to standard diets rich in omega-6. RESULTS There was a significant 40-60% reduction in keel bone breakage rate, and a corresponding reduction in breakage severity in the omega-3 supplemented hens. There was significantly greater bone density and bone mineral content, alongside increases in total bone and trabecular volumes. The mechanical properties of the omega-3 supplemented hens were improved, with strength, energy to break and stiffness demonstrating significant increases. Alkaline phosphatase (an osteoblast marker) and tartrate-resistant acid phosphatase (an osteoclast marker) both showed significant increases with the omega-3 diets, indicating enhanced bone turnover. This was corroborated by the significantly lower levels of the mature collagen crosslinks, hydroxylysyl pyridinoline, lysyl pyridinoline and histidinohydroxy-lysinonorleucine, with a corresponding significant shift in the mature:immature crosslink ratio. CONCLUSIONS The improved skeletal health in laying hens corresponds to as many as 68million fewer hens suffering keel fractures in the EU each year. The biomechanical and biochemical evidence suggests that increased bone turnover has enhanced the bone mechanical properties, and that this may suggest potential benefits for human osteoporosis.
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Recent studies in laying hens have shown that feather peckers eat more feathers than nonpeckers. We hypothesized that food pellets containing feathers would decrease the birds' appetite for feathers and thereby also decrease feather pecking. To separate the effect of feathers from that of insoluble fiber per se, additional control groups were fed pellets containing similar amounts of cellulose. Sixty (experiment 1) and 180 (experiment 2) 1-d-old Lohmann-Selected Leghorn birds were divided into 12 groups of 5 (experiment 1) and 15 (experiment 2) birds, respectively, and kept on slatted floors. During the rearing period, 4 groups each had ad libitum access to either a commercial pelleted diet, a pelleted diet containing 5% (experiment 1) or 10% (experiment 2) of chopped feathers, respectively, or a pelleted diet containing 5% (experiment 1) or 10% (experiment 2) of cellulose, respectively. In the consecutive laying period, all groups received a commercial pelleted diet. In experiment 1, feather pecking was recorded weekly from wk 5 to wk 16. In the laying period, observations were made in wk 18, 20, 22, 23, 24, 25, 26, 27, 28, and 30. In experiment 2, feather pecking was recorded weekly from wk 5 to 11, in wk 16 to wk 18, and in wk 20 and 21. At the end of the rearing period, plumage condition per individual hen was scored. Scores from 1 (denuded) to 4 (intact) were given for each of 6 body parts. The addition of 10% of feathers to the diet reduced the number of severe feather-pecking bouts (P < 0.0129) and improved plumage condition of the back area (P < 0.001) significantly compared with control diets. The relationship between feather pecking/eating and the gastrointestinal consequences thereof, which alter feather pecking-behavior, are unclear. Understanding this relationship might be crucial for understanding the causation of feather pecking in laying hens.
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Between 2008 and 2012, commercial Swiss layer and layer breeder flocks experiencing problems in laying performance were sampled and tested for infection with Duck adenovirus A (DAdV-A; previously known as Egg drop syndrome 1976 virus). Organ samples from birds sent for necropsy as well as blood samples from living animals originating from the same flocks were analyzed. To detect virus-specific DNA, a newly developed quantitative real-time polymerase chain reaction method was applied, and the presence of antibodies against DAdV-A was tested using a commercially available enzyme-linked immunosorbent assay. In 5 out of 7 investigated flocks, viral DNA was detected in tissues. In addition, antibodies against DAdV-A were detected in all of the flocks.
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Measuring the ratio of heterophils and lymphocytes (H/L) in response to different stressors is a standard tool for assessing long-term stress in laying hens but detailed information on the reliability of measurements, measurement techniques and methods, and absolute cell counts is often lacking. Laying hens offered different sites of the nest boxes at different ages were compared in a two-treatment crossover experiment to provide detailed information on the procedure for measuring and the difficulties in the interpretation of H/L ratios in commercial conditions. H/L ratios were pen-specific and depended on the age and aviary system. There was no effect for the position of the nest. Heterophiles and lymphocytes were not correlated within individuals. Absolute cell counts differed in the number of heterophiles and lymphocytes and H/L ratios, whereas absolute leucocyte counts between individuals were similar. The reliability of the method using relative cell counts was good, yielding a correlation coefficient between double counts of r > 0.9. It was concluded that population-based reference values may not be sensitive enough to detect individual stress reactions and that the H/L ratio as an indicator of stress under commercial conditions may not be useful because of confounding factors and that other, non-invasive, measurements should be adopted.
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Laying hens in loose-housing systems select a nest daily in which to lay their eggs among many identical looking nests, they often prefer corner nests. We investigated whether heterogeneity in nest curtain appearance – via colours and symbols – would influence nest selection and result in an even distribution of eggs among nests. We studied pre-laying behaviour in groups of 30 LSL hens across two consecutive trials with eight groups per trial. Half of the groups had access to six identical rollaway group-nests, while the others had access to six nests of the same type differing in outer appearance. Three colours (red, green, yellow) and three black symbols (cross, circle, rectangle) were used to create three different nest curtain designs per pen. Nest position and the side of entrance to the pens were changed at 28 and 30 weeks of age, respectively, whereby the order of changes was counterbalanced across trials. Nest positions were numbered 1–6, with nest position 1 representing the nest closest to the pen entrance. Eggs were counted per nest daily from week of age 18 to 33. Nest visits were recorded individually with an RFID system for the first 5 h of light throughout weeks 24–33. Hens with access to nests differing in curtain appearance entered fewer nests daily than hens with identical nests throughout the study but both groups entered more nests with increasing age. We found no other evidence that curtain appearance affected nest choice and hens were inconsistent in their daily nest selection. A high proportion of eggs were laid in corner nests especially during the first three weeks of lay. The number of visits per egg depended upon nest position and age: it increased with age and was higher after the nest position change than before in nest position 1, whereas it stayed stable over time in nest position 6. At 24 weeks of age, gregarious nest visits (hens visiting an occupied nest when there was at least one unoccupied nest) and solitary nest visits (hens visiting an unoccupied nest when there was at least one occupied nest) accounted for a similar amount of nest visits, however, after the door switch, gregarious nest visits made up more than half of all nest visits, while the number of solitary nest visits had decreased. The visual cues were too subtle or inadequate for hens to develop individual preferences while nest position, entrance side, age and nest occupancy affected the quantity and type of nest visits.
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Non-cage housing systems for laying hens such as aviaries provide greater freedom to perform species-specific behavior and thus are thought to improve welfare of the birds; however, aviaries are associated with a high prevalence of keel bone damage (fractures and deviations), which is a major welfare problem in commercial laying hens. Potential causes of keel bone damage are falls and collisions with internal housing structures that occur as birds move between tiers or perches in the aviary. The aim of this study was to investigate the scope for reducing keel bone damage by reducing falls and collisions through modifications of aviary design. Birds were kept in 20 pens in a laying hen house (225 hens per pen) that were assigned to four different treatments (n = 5 pens per treatment group) including (1) control pens and pens modified by the addition of (2) perches, (3) platforms and (4) ramps. Video recordings at 19, 22, 29, 36 and 43 weeks of age were used to analyze controlled movements and falls (including details on occurrence of collision, cause of fall, height of fall and behavior after fall) during the transitional dusk and subsequent dark phase. Palpation assessments (focusing on fractures and deviations) using 20 focal hens per pen were conducted at 18, 20, 23, 30, 37, 44, 52 and 60 weeks of age. In comparison to the control group, we found 44% more controlled movements in the ramp (P = 0.003) and 47% more controlled movements in the platform treatments (P = 0.014) as well as 45% fewer falls (P = 0.006) and 59% fewer collisions (P < 0.001) in the ramp treatment. There were no significant differences between the control and perch treatments. Also, at 60 weeks of age, 23% fewer fractured keel bones were found in the ramp compared with the control treatment (P = 0.0053). After slaughter at 66 weeks of age, no difference in keel bone damage was found between treatment groups and the prevalence of fractures increased to an average of 86%. As a potential mechanism to explain the differences in locomotion, we suggest that ramps facilitated movement in the vertical plane by providing a continuous path between the tiers and thus supported more natural behavior (i.e. walking and running) of the birds. As a consequence of reducing events that potentially damage keel bones, the installation of ramps may have reduced the prevalence of keel fractures for a major portion of the flock cycle. We conclude that aviary design and installation of specific internal housing structures (i.e. ramps and platforms) have considerable potential to reduce keel bone damage of laying hens in aviary systems.
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Glaucous gulls (Larus hyperboreus) and their eggs from Svalbard (Norwegian Arctic) have been used as biomonitors of contaminants in the marine environment. In this study, the enantiomer fractions (EFs) of chiral chlordanes and atropisomeric polychlorinated biphenyl (PCB) congeners were determined in the blood plasma of adult male and female glaucous gulls from three breeding colonies in Svalbard. Plasma EFs were similar in magnitude and direction to EFs previously reported in glaucous gulls from other arctic food webs, suggesting overall similarities in the biochemical processes influencing the EFs of bioaccumulated organochlorine (OC) contaminants within the food webs at those locations. Additionally, EFs in yolk of eggs collected concurrently from within the same nesting colonies varied with location, laying date, and OC concentrations, and may be influenced by changes in the local feeding ecology between those colonies. No differences were found between the EFs for any analyte in female gulls compared to those found in egg yolk, indicating that processes involved in the maternal transfer of chlordanes and PCBs to eggs do not modulate the stereochemical ratio between enantiomers. Therefore, the use of eggs as a valuable and noninvasive means of OC biomonitoring may also extend to enantiomer compositions in glaucous gulls, and perhaps also in other seabird species from arctic regions.
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A total of 108 eggs from a group of 100 brown laying hens housed in standard cages were analyzed. Thirty-six eggs were retired when the hens had 30 week of age, other 36 eggs were retired when the hens had 35 week of age and the remaining 36 eggs were retired five weeks afterwards. Each group of 36 eggs was radomly divided in three groups of 12 eggs. First group was analyzed at once, second group one was kept during one week in the refrigerator (5°C) and third group was kept also one week but on ambient temperature (25°C). Shell color, shell thickness, specific gravity, albumen height and Haugh units wre obtained. The bird age had significant effect on shell color and shell thickness, but the storage system had not influence on such variables. The hen age had not effect on specific gravity, but the storage system affected to this variable. Hen age and storage system had significant influence (P<0.05) on albumen height and Haugh units, and the interaction age × storage system was significant for these variables. The specific gravity had positive relations with shell thickness, yolk color, albumen height and Haugh units. It is concluded that bird age and storage system under high temperatures reduced the egg quality.
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En la presente Tesis Doctoral se ha estudiado el efecto de una metodología para inducir la muda en dos estirpes de gallinas ponedoras comerciales, una ligera y otra semipesada, mediante el suministro de tres alimentos: salvado de trigo, cebada en grano y un pienso comercial de ponedoras aportado en cantidad restringida. Se realizaron dos pruebas en dos lotes diferentes de gallinas. En la primera de ellas se utilizaron 472 animales (236 de cada estirpe) alojados en jaulas con cuatro o seis gallinas por jaula, con una estructura factorial 2 x 3 x 2 (2 estirpes, 3 alimentos, 2 densidades) y una duración total de 32 semanas (4 de muda y 28 de producción posmuda). En la segunda prueba fueron 432 animales los utilizados (216 de cada estirpe), alojados en grupos de cuatro aves por jaula, con una estructura factorial 2 x 3 (2 estirpes, 3 alimentos) y una duración de 27 semanas (4 de muda y 23 de producción postmuda). En los dos experimentos realizados se estudió el efecto del uso de los alimentos citados para inducir de la muda sobre los resultados cuantitativos: pérdida de peso vivo durante la muda e intensidad de puesta, peso medio del huevo y masa de huevo diaria, durante y después de la muda, así como la distribución de la puesta en clases comerciales durante el segundo ciclo de puesta. Así como sobre los resultados cualitativos después de la muda: color de la cáscara de los huevos morenos, espesor de la cáscara, peso específico del huevo, altura del albumen, unidades Haugh y color de la yema. En la primera prueba se estudió, además, el efecto que la inducción de la muda mediante los tres alimentos considerados tuvo sobre la regresión del aparato reproductor de las gallinas durante este período de muda. En el primer experimento se observaron diferencias entre estirpes. Las gallinas ligeras tuvieron una más rápida regresión del aparato reproductor (ovario+oviducto) (P=0,003) que las semipesadas, aunque la regresión total no presentó diferencias significativas. Las gallinas semipesadas tuvieron mejores resultados después de la muda en intensidad de puesta (P<0,0001), en peso medio del huevo (P<0,0001) y en masa de huevo diaria (P=0,0002). También hubo diferencias significativas para las variables cualitativas espesor de la cáscara (mayor en huevos de gallinas semipesadas) mientras que los huevos procedentes de gallinas ligeras presentaron mejores valores de altura del albumen, de unidades Haugh y de color de yema; todas estas variables tuvieron un nivel de significación P<0,0001. El suministro restringido de pienso dio lugar a un mayor porcentaje de pérdida de peso vivo (P<0,0001) aunque la regresión de los órganos del aparato reproductor fue la más baja (P<0,003), no habiéndose encontrado diferencias entre los otros dos alimentos utilizados. Con este alimento también fue más lenta (P<0,0001) la disminución de la puesta durante la muda, aunque fue mayor la producción durante el segundo ciclo (P<0,0001). La única variable cualitativa afectada fue el espesor de cáscara (P<0,0001), con valores más altos en los huevos producidos por las gallinas mudadas con cebada. Los grupos de seis gallinas por jaula produjeron más huevos durante la muda (P<0,0001) aunque después de ésta la densidad de animales no tuvo efecto significativo, como tampoco lo hubo sobre los parámetros de calidad del huevo. En la segunda prueba las gallinas semipesadas experimentaron un menor porcentaje de pérdida de peso corporal (P<0,01) pero tuvieron mayores índices de puesta (P<0,001) y de huevos clasificables (P<0,001) durante la muda. En cambio, durante el segundo ciclo de producción las gallinas ligeras produjeron más huevos (P=0,0041), de menor peso (P<0,02) y con menor consumo de pienso (P<0,001). Los huevos puestos por las gallinas semipesadas tuvieron mayor espesor de cáscara y mayor color de yema, pero peor calidad de albumen (P<0,0001). La mayor pérdida de peso la experimentaron las gallinas mudadas con salvado (P<0,02). La producción durante la muda fue mayor (P<0,001) en las gallinas que consumieron pienso en cantidad restringida y también fueron las que tuvieron menor intensidad de puesta (P<0,006) y masa de huevo diaria (P<0,042) durante el segundo ciclo. El tratamiento de muda no tuvo efecto significativo sobre la calidad del huevo en esta segunda prueba. La principal conclusión que merece destacarse es que es posible inducir la muda a las gallinas ponedoras utilizando alimentos bajos en energía o en proteína, o altos en fibra, con un porcentaje de pérdida de peso vivo no tan alta como las recomendaciones tradicionales, y alcanzar buenos resultados productivos, tanto cuantitativos como cualitativos, durante el segundo ciclo de puesta. ABSTRACT Present Doctoral Thesis has studied the effect of a methodology to induce molting in two strains of commercial laying hens, one light and another semi-heavy one, through the provision of three feed: wheat bran, barley grain and a commercial laying hens feed provided in limited quantity. Two tests were performed in two different lots of layers. In the first 472 animals were used (236 of each strain) housed in cages with four or six hens per cage, with a structure 2 x 3 x 2 factorial (2 strains, 3 meals, 2 densities) and a total duration of 32 weeks (4 of molt and 28 of postmolting). In the second test 432 animals were used (216 each strain), housed in groups of four birds per cage, with a structure factorial 2 x 3 (2 strain, 3 meals) along 27 weeks (4 of molt and 23 of postmolting). In both experiments, we studied the effect of the use of above mentioned foods to induce molting on the quantitative results: body weight lost during the molt and laying index, average egg weight and egg mass daily during and after the molt, as well as on grading in commercial classes during the second laying cycle. As well as on qualitative outcomes after the molt: colour of Brown eggsshell, shell thickness, specific density, albumen height, Haugh units and yolk colour. In the first test was studied, in addition, the effect of induction of molting through the three feed considered on the regression of the reproductive tract of hens during molting period. In the first experiment, differences between strains were observed. Light hens had a faster regression of the reproductive tract (ovary+oviduct) (P=0,003) than semi-heavy hens, although the total regression did not present significant differences. Semi-heavy hens had better outcomes after the molt in laying index (P<0.0001), in average egg weight (P<0.0001) and daily egg mass (P=0, 0002). There were also significant differences for the qualitative variables (higher in semi-heavy hen eggs) as shell thickness while light chicken eggs showed better values of albumen height, Haugh units and yolk color; all these variables had the same level of significance (P<0.0001). Restricted supply of layer feed resulted in a greater percentage of live weight loss (P<0.0001) although the regression of the reproductive organs was the lowest (P<0.003), having not found differences between the other two feed used. With this food decreasing of laying during molting period was also slower (P<0.0001), although production was higher during the second cycle (P < 0.0001). The only qualitative variable affected was shell thickness (P<0.0001), with higher values in the eggs produced by hens molted with barley. Groups of six hens per cage produced more eggs during the moult (P<0.0001) but after this animal density had no significant effect, as neither had it on egg quality parameters. In the second trial hens semi-heavy experienced a lower percentage of body weight loss (P<0.01) but had higher rates of egg production (P<0.001) and of grading eggs (P<0.001) during the moult. On the other hand, during the second production cycle light hens produced more eggs (P=0,0041), of lower weight (P < 0.02) and with less feed intake (P<0.001). Eggs from semi-heavy hens had thicker shell and greater color yolk, but poorer quality of albumen (P<0.0001). The greater weight loss was experimented by the hens molted with wheat bran (P=0.02). Production during molting period was greater (P<0.001) in hens which consumed feed in restricted quantities and were also less the laying index (P=0.006) and daily egg mass (P=0.042) during the second cycle. The molting treatment had no significative effect on the quality of the egg in this second test. The main conclusion that deserves to stand out is that it is possible to induce molting hens using foods low in energy or in protein or high in fiber, with a percentage of live weight loss not as high as the traditional recommendations, and achieve good productive, both quantitative and qualitative results during the second implementation cycle.
Resumo:
1 Accurate assessment of the impact of natural enemies on pest populations is fundamental to the design of robust integrated pest management programmes. In most situations, diseases, predators and parasitoids act contemporaneously on insect pest populations and the impact of individual natural enemies, or specific groups of natural enemies, is difficult to interpret. These problems are exacerbated in agro-ecosystems that are frequently disrupted by the application of insecticides. 2 A combination of life-table and natural enemy exclusion techniques was utilized to develop a method for the assessment of the impact of endemic natural enemies on Plutella xylostella populations on commercial Brassica farms. 3 At two of the experimental sites, natural enemies had no impact on P. xylostella survival, at two other sites, natural enemy impact was low but, at a fifth site, natural enemies drastically reduced the P. xylostella population. 4 The calculation of marginal death rates and associated k-values allowed the comparison of mortality factors between experimental sites, and indicated that larval disappearance was consistently the most important mortality factor, followed by egg disappearance, larval parasitism and pupal parasitism. The appropriateness of the methods and assumptions made to calculate the marginal death rates are discussed. 5 The technique represents a robust and easily repeatable method for the analysis of the activity of natural enemies of P. xylostella, which could be adapted for the study of other phytophagous pests.
