Photoperiodic responses of broilers. II. Ocular development

Abstract

1. Poultry are naturally long-sighted when they hatch, becoming emmetropic by 6 weeks of age. However, Cobb and Ross broilers exposed to <or=12-h photoperiods rapidly learn to eat in the dark, a behaviour which could adversely affect the establishment of emmetropia. And so, in the current study, eyes were enucleated, post mortem, at 40 and 54 d from broilers given various photoperiods between 2 and 24 h, and eye weight determined to indirectly assess the extent to which photoperiod might affect ocular development. 2. In both genotypes, there was an inverse linear relationship between absolute eye weight and photoperiod up to 21 h, but continuously illuminated birds consistently had heavier eyes. When expressed relative to body weight, eye weight for <or=21-h birds was inversely related to the logarithm of photoperiod. 3. The slope of the regression of relative eye weight on <or=21-h photoperiod log values was significantly less at 54 d than at 40 d in both genotypes, but constantly illuminated birds continued to have above average eye weights. 4. Cobb birds invariably had heavier eyes than Ross, both in absolute and relative (to body weight) terms. 5. The results support previous work suggesting that there is a minimum period of daily darkness required to maintain chicken eye growth within the normal range and show that very short photoperiods, as well as ultra-long photoperiods and continuous illumination, adversely affect ocular development, with potential welfare implications.

A review of environmental enrichment for laying hens during rearing in relation to their behavioral and physiological development

“…Lighting conditions during rearing play a key role for visual development. Dim light, very short, or very long continuous photoperiods can hamper the ability of chicks to focus (Lewis and Gous, 2009) and low illuminance can also cause myopia (short-sightedness) (Cohen et al., 2008, 2011). However, high light intensity is also strongly correlated with development of feather pecking, confounding use of higher intensities in commercial systems (Janczak and Riber, 2015).…”

Broilerlerde Fotoperyod Uzunluğunun Performans Parametreleri, Karkas Özellikleri ve Heterofil/Lenfosit Oranı Üzerine Etkisi

“…Lewis et al [25] indicated that continuous lighting increased the percentage of breast meat. Similarly, Lien et al [31] confirmed that the extension of the light period from 16 h to 23 h increased the percentage of the whole breast.…”

“…Similarly, it has been indicated that lighting schedules of 20L:4D and 16L:8D did not produce any statistically significant difference for broiler body weights [4] . It is suggested that broiler chickens modify their feeding behaviour according to the lighting programme they are exposed to [24,25] . Lewis et al [25] suggested that, the extension of the photoperiod length during the period up to day 21 increased feed consumption, while between days 22-35, photoperiods longer than 6 hours resulted in similar feed consumption rates.…”

Effects of the restriction of access to feed on growth performance and the development of the proximal part of the gastrointestinal tract in young broilers

“…Consequently, FR practices starting earlier than 7 d of age might not be advisable (Plavnik and Hurwitz, 1985;Camacho et al, 2004). Previous research (Lewis et al, 2009;Schwean-Lardner et al, 2016;Farghly et al, 2019) have reported that the negative effects of FR on growth performance are especially evident during the period of adaptation to the fasting strategy. However, most of these studies do not report any numerical data on the impact of FR on FI and broiler growth during the first days after the implementation of the feeding strategy.…”

“…As diurnal animals, chickens eat regularly during the light period as long as there is no restriction in feeding availability or other environmental factors (Classen et al, 2016). During the dark period, however, FI is strongly reduced and therefore, intermittent light programs are associated with FR practices (Buyse et al, 1993;Lewis et al, 2009). Several factors, such as light intensity, feeder space, and stocking density interact with the lighting program modifying the effects of the lighting patterns on bird performance.…”