Laying hens can be kept in cages, in so-called enriched cages, in floor pens, or free range (organic or conventional). Different breeds seem to behave differently under each of these conditions. Although the use of cages has been banned in Europe since 2012, not all European countries have implemented this regulation till today. Animal welfare and consumer preferences have – at the cost of economic disadvantages – been considered in this decision. The influence of housing systems on Salmonella infections has been seen as controversial. Some studies show an increase in transmission between birds in non-cage housing, whereas others demonstrate that Salmonella infections are seen significantly more often on farms keeping hens in cages. This has also been discussed by the European Food Safety Authority (EFSA) in 2007 in their scientific opinion on a possible European ban of keeping laying hens in cages. Optimal biosecurity, cleaning, and disinfection have been characterised as protective against Salmonella in laying hens in existing housing system.
Hen nutrition for sustained egg quality
- Bouvarel, … P. Lescoat, in Improving the Safety and Quality of Eggs and Egg Products: Egg Chemistry, Production and Consumption, 2011
Effects of feed presentation
Laying hens feed themselves in response to their needs but also according to their preferences and ability to recognise particular components of the diet. Interactions occur between feed preferences and physiological regulation, thus affecting food intake and consequently egg production and egg weight.
Poultry feed particles must be sufficiently large to be picked up with the beak (Rogers, 1995). Such preferences correspond to energy optimisation (cost/benefit) of feeding behaviour (Collier and Johnson, 2004). Laying hens thus select their food intake according to the relative size of the particles in relation to the beak. Using feeds presented as crumbs (72% of particles > 1.18 mm) (Portella et al., 1988) demonstrated an immediate preference by laying hens for the largest particles. In a mix of whole wheat and meal diet formulated on complete diet, birds prefer particles larger than 2 mm (Dezat et al., 2009). On the other hand, hens do not demonstrate a preference for the largest particles when the feed is presented as a fairly homogeneous meal in which ‘ mean sized’ particles are mainly between 0.60 and 2.34 mm and when it contains substantial quantities of calcium and proteins. This observation suggests that calcium is a key factor in feed consumption (Portella et al., 1988). Moreover, small particles (< 0.60 mm) disappear slowly from the trough whatever the presentation (Portella et al., 1988). These small particles often contain micronutrients such as vitamins, minerals and amino acids and percolate to the bottom of the feeding trough (Tang et al., 2006).
Joly (2004) showed that distribution of a fine meal compared with a more coarse one (31% vs 9% particles < 0.5 mm) resulted in a reduction in feed consumption, laying rate and egg weight (-0.9 g). Addition of small quantities of fat or water can solve this problem by sticking the particles together, facilitating uptake (Tang et al., 2006).
The use of moistened feed has been scarcely studied in laying hens. It stimulates consumption of dry matter (Tadtiyanant et al., 1991; El Kaseh and Forbes, 1995). In contrast, the use of fermented moist feed, which is characterised by a low pH (4.5), reduces ingestion of dry matter when fed to birds between 18-37 weeks (110 vs 125 g/day) (Engberg et al., 2009).
The physical form of the feed interacts with the ability of the hen to fit its energy intake to the energy concentration of the feed. Hens will more willingly eat feeds diluted with fibre (45% wheat bran) when presented as pellet rather than as meal (Vilarino et al., 1996). Diet presentation therefore makes it possible to improve the energy intake of low energy diets.
Moreover, it has been shown that poultry are able to learn and recognise their feed which improves their ability to change their feeding behaviour. A sudden change in feed, for example from flour meal to large particles (> 2.35 mm), can result in an immediate reduction in consumption (-28%) which in turn will affect egg weight (Portella et al., 1988).
Of Mice and Hens—Tackling Salmonella in Table Egg Production in the United Kingdom and Europe
Francesca Martelli, … Rob Davies, in Producing Safe Eggs, 2017
Laying hens can become infected with a number of non–host-specific Salmonella serovars, of which Salmonella Enteritidis and Salmonella Typhimurium (including monophasic strains) are considered the most relevant threat to public health in Europe. S. Enteritidis in particular is able to persist indefinitely on layer farms unless effective interventions are implemented. In 2014, 2.5% of adult laying flocks in the European Union were reported to be infected by Salmonella (0.9% with either S. Enteritidis or S. Typhimurium). Laying hens can become infected as a result of contact with a contaminated environment (either at the hatchery or farm). Once Salmonella infection is established in a flock, it is perpetuated through a faecal–oral cycle. Rodents, particularly house mice, play a major role in the persistence of the infection, especially for flocks infected with S. Enteritidis. Rodents can readily become infected via contact with faeces and dust and harbour salmonellae in their intestines and liver, where they can multiply to high numbers and persist for the whole life of a wild mouse. Contamination of feeding and water supply systems and surfaces of buildings and equipment by rodent droppings leads to infection in birds and contamination of egg collection equipment can directly contaminate eggs. Even when hens are vaccinated against Salmonella, the presence of breeding and young rodents shedding high numbers of organisms usually undermines vaccinal protection, although the occurrence of systemic infection of hens and internally contaminated eggs will still be reduced. When infected flocks are removed at the end of a production cycle, Salmonella can persist in the environment and infect replacement flocks. Intensive baiting of rodents before depopulation, and especially at the time when houses are empty and poultry feed has been removed, is essential to break the cycle of infection and avoid Salmonella carryover between flocks. Flies and litter beetles can also be infected for short periods and may be involved in the transmission and persistence of infection when downtime between flocks is short, or multiple age production is in place on the laying farm. Infestation by red mites can reduce the ability of birds to resist or clear infection, as a result of stress and anaemia, and red mites are the main means of transmission of the non zoonotic Salmonella Gallinarum biovar Gallinarum infection. Salmonella can survive for months in contaminated dust and laying hen houses tend to generate large quantities of dust during the long production cycle. Effective cleaning and disinfection between flocks is often costly to implement in laying houses, especially large cage units that are usually not designed to facilitate drainage after washing, leading to persistence of contamination between flocks. Removing all organic matter and using highly bioactive disinfectants such as aldehydes at the correct concentration and application rate is essential to avoid environmental persistence of Salmonella. Salmonella can be present at low prevalence in adult laying hens in mid lay and in older pullets and may therefore be difficult to detect. It is often assumed that new infections have entered laying farms when in reality the Salmonella has been continuously present but below the limits of detection of standard monitoring programs. Effective sampling and testing is therefore essential to the control of Salmonella on-farm. In the European Union, major progress on control of Salmonella in egg production has only been achieved after the introduction of effective vaccination programs and the application of severe financial penalties in terms of trade restrictions on the sale of fresh eggs from infected farms, which in many countries makes continued production from infected flocks economically unsustainable. Official sampling by the competent authority is also in place to validate operator sampling. Such incentives are usually required to ensure that effective control measures that come at a cost to the producer are fully implemented.
Laying hens can become infected with a number of non–host-specific Salmonella serovars, of which Salmonella Enteritidis and Salmonella Typhimurium (including monophasic strains) are considered the most relevant threat to public health in Europe. S. Enteritidis in particular is able to persist indefinitely on layer farms unless effective interventions are implemented. In 2014, 2.5% of adult laying flocks in the European Union were reported to be infected by Salmonella (0.9% with either S. Enteritidis or S. Typhimurium). Laying hens can become infected as a result of contact with a contaminated environment (either at the hatchery or farm). Once Salmonella infection is established in a flock, it is perpetuated through a faecal–oral cycle. Rodents, particularly house mice, play a major role in the persistence of the infection, especially for flocks infected with S. Enteritidis. Rodents can readily become infected via contact with faeces and dust and harbour salmonellae in their intestines and liver, where they can multiply to high numbers and persist for the whole life of a wild mouse.
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