Illuminance, sexual maturation, and early egg production in female broiler breeders

Effect of light intensity and stocking density on the performance, egg quality, and feather condition of laying hens reared in a battery cage system over the first laying period

The present study aimed to determine the effects of varying light intensity (high 121.8, medium 57.4 and low 11.9 lux) and stocking density (high 552.3, medium 736.3, and low 1104.5 cm² cage floor area per hen) treatments on the performance, egg quality, and certain feather condition traits of Lohmann-Brown hens reared in a battery cage system between 20 and 40 weeks of age. Body weight was determined individually at 19 weeks and at 50% yield age (sexual maturity). Feed intake, egg yield, egg weight, and feed conversion ratio were determined weekly. Feather condition was also evaluated individually at 40 weeks of age. Hens reared under high light intensity and low stocking density reached sexual maturity and peak yield earlier than others. The highest body weight was determined for hens reared under high light intensity (1536.6 g), while the lowest in the medium light intensity group (1461.2 g). Hens reared under high and medium light intensity showed higher egg yield than those reared in low intensity (120.5, 120.0 and 112.8 eggs, respectively). In addition, hens reared at low and medium stocking density had higher egg yield than high density (119.7, 120.7, and 112.9 eggs, respectively). Hens reared under low (61.6 g) and medium (61.0 g) light intensity produced heavier eggs than hens in high light intensity (59.6 g). While feed intake was not affected in any treatment, hens reared at low and medium stocking density had a better feed conversion ratio than hens at high density (2.19, 2.20, and 2.40, respectively). Our study results showed that a sustainable production is possible by maintaining the welfare-performance balance when 50-60 lux light intensity and 700-800 cm² cage floor area per hen are provided.

Influence of a raised slatted area in front of the nest on leg health, mating behaviour and floor eggs in broiler breeders

European farms for broiler breeders often have raised slatted areas in front of the nests, but in other regions of the world no raised slatted areas are provided. This study aimed to investigate the effects of a raised slatted area on leg health, mating behaviour and floor laying behaviour. Ten groups of 33 broiler breeder hens and three males were housed in two pen types: with or without a raised slatted area in front of the nests. Each pen had one plastic and one wooden nest. Between 25 and 31 weeks of age, ten marked hens per pen were weighed and assessed weekly on foot pad dermatitis, hock burn and wounds. At the end of week 31, animals were euthanized and bone strength of the tibia and humerus of these individuals was assessed. At 24, 27 and 30 weeks of age, mating behaviour was observed for an hour per pen, noting both numbers of successful and unsuccessful copulations. The number of eggs laid in the nests and on the floor was recorded daily between 20 and 31 weeks of age. Foot pad dermatitis scores were affected by age, but not by pen type. Generally, there were only minor issues with foot pad dermatitis (scores <11 on a 0-100 scale), probably due to the young age of the hens. Body weight was not affected by pen type, while the prevalence of hock burns was too low to analyse and no difference in bone strength was found for the tibia and the humerus. Overall, mating behaviour was less frequent in pens with raised slats than in pens without raised slats (29 ± 2 vs 35 ± 3 times/h) and more frequent at 27 weeks of age than at 24 and 30 weeks of age (38 ± 1 vs 31 ± 4 and 27 ± 2 times/h). The pens with raised slats had a lower percentage of floor eggs than pens without raised slats (11.2 ± 0.4 vs 19.3 ± 0.5%). The wooden nest was preferred over the plastic nest as on average 63% of the eggs were laid in the wooden nest. This study shows that providing raised slats decreases mating behaviour and percentage of floor eggs, although its effects on leg health remain inconclusive.

Developmental phenotypic plasticity helps bridge stochastic weather events associated with climate change

The slow, inexorable rise in annual average global temperatures and acidification of the oceans are often advanced as consequences of global change. However, many environmental changes, especially those involving weather (as opposed to climate), are often stochastic, variable and extreme, particularly in temperate terrestrial or freshwater habitats. Moreover, few studies of animal and plant phenotypic plasticity employ realistic (i.e. short-term, stochastic) environmental change in their protocols. Here, I posit that the frequently abrupt environmental changes (days, weeks, months) accompanying much longer-term general climate change (e.g. global warming over decades or centuries) require consideration of the true nature of environmental change (as opposed to statistical means) coupled with an expansion of focus to consider developmental phenotypic plasticity. Such plasticity can be in multiple forms - obligatory/facultative, beneficial/deleterious - depending upon the degree and rate of environmental variability at specific points in organismal development. Essentially, adult phenotypic plasticity, as important as it is, will be irrelevant if developing offspring lack sufficient plasticity to create modified phenotypes necessary for survival.

Illuminance and egg production in broiler breeders

1. Ross broiler breeders were reared at a nominal illuminance of 15, 20 or 45 lux and transferred to a nominal illuminance of 25, 55 or 70 lux at 20 weeks. 2. There were no significant interactions between the response to illuminance during rearing and in lay. This means that it matters not whether illuminance is increased, decreased or held constant on transfer to the laying house, provided it equals or exceeds the biological optimum for satisfactory egg production. 3. Whilst there were no significant effects of illuminance in either the rearing period or laying periods on egg numbers, peak rate of lay, terminal rate of lay, egg mass output or liveability, meta-analyses of these and other data indicated biological optima of 15 lux during rearing and 7 lux in the laying period. Birds reared at 45 lux had a lower mean egg weight (and earlier sexual maturity) than birds reared at 15 lux, and hens illuminated at 25 lux in the laying period laid more eggs on the floor than at either 55 or 70 lux. 4. Typical primary breeder recommendations of 10-20 lux during rearing and 30-60 lux in lay are appropriate for floor-housed birds; however, an illuminance of 7 lux could be used for caged birds, subject to welfare-code compliance.