Photoperiodic responses of broilers. III. Tibial breaking strength and ash content

Abstract

1. A total of 7960 Cobb and Ross broiler males were reared on various photoperiods or continuous illumination in two trials to 35 or 40 d. Tibial breaking strength was measured in both, and tibial ash content determined in the first of the two trials. 2. Tibial breaking strength was significantly affected by photoperiod, body weight, testicular weight, and genotype. Although peak bone strength occurred at about 7 h for Ross and at 12 h for Cobb, with reductions in strength for both shorter and longer photoperiods than these peaks, the removal of body weight effects showed that tibial breaking strength was negatively correlated with photoperiod per se. However, after removal of photoperiodic influences, breaking strength was positively correlated with both body weight and testicular weight. 3. Ross birds had greater tibial breaking strengths than Cobb, irrespective of whether the comparisons were made at the same photoperiod, the same body weight, or the same ash content. 4. Ash content increased according to the logarithm of photoperiod, but was unrelated to body weight. Tibial breaking strength increased with ash content. Ash contents were similar for Ross and Cobb birds. 5. Despite the significant differences in breaking strength and ash content, there were no broken bones or signs of leg abnormality in any of the 300 birds sampled. Tibial breaking strength data may therefore be of limited value in assessing the benefits of photoperiod to welfare in modern broilers.

Effects of Intermittent Lighting on Broiler Growth Performance, Slaughter Performance, Serum Biochemical Parameters and Tibia Parameters

“…Further, Onba ılar et al (2007) reported that chickens reared in IL had numerically lower tibial dyschondroplasia values. As well, prior reports indicated that tibial breaking strength was significantly affected by photoperiod and genotype, and that peak bone strength was achieved with a 7 h lighting period, with reductions in strength apparent following both shorter and longer photoperiods (Lewis et al, 2009). In the present experiment, no leg abnormalities were detected among the three experimental treatments; however, the bone elastic modulus of birds reared in the 4L:4D photoperiod was greater than the corresponding measurements obtained from birds in the other two photoperiod treatments, which indicated that the 4L:4D photoperiodic lighting perhaps favored tibial growth in broilers.…”

Bringing eggs and bones to light : affecting leg bone development in broiler chickens through perinatal lighting schedules

“…Feed intake was higher for 24L compared to applying a lighting schedule and higher for the 2L:1D lighting schedule than for the 2L:6D lighting schedule in both experiments. Lewis et al (2009) demonstrated that broilers will learn to eat in dark when they are kept under prolonged (> 16 h) dark periods in a lightproof room, similar to the present study. However, they subjected broilers to an uninterrupted dark period (Lewis et al, 2009), whereas the dark period in the present study lasts a maximum 6 h at a time.…”

“…Lewis et al (2009) demonstrated that broilers will learn to eat in dark when they are kept under prolonged (> 16 h) dark periods in a lightproof room, similar to the present study. However, they subjected broilers to an uninterrupted dark period (Lewis et al, 2009), whereas the dark period in the present study lasts a maximum 6 h at a time. This may have decreased the broiler's incentive to start eating in the dark compared to a continuous long dark period, and resulted in lower overall feed intake for the 2L:6D lighting schedule compared to the other treatments.…”

“…Most previous studies were aimed at effects of light on skeletal problems at slaughter age and started with a 23L:1D lighting schedule or 24L for the first 3 or 4 days (Classen et al, 1991;Sanotra et al, 2002;, followed by their treatment lighting schedules. Although some authors did apply light-dark schedules from D1 post-hatch onwards (Lewis et al, 2009), they continued these schedules throughout the growing period. In the present study, leg bone development was investigated in a brooding system, called HatchBrood (Van der Pol et al, 2013).…”

Effect of breeder age and lighting regimen on growth performance, organ weights, villus development, and bursa of fabricius histological structure in broiler chickens

“…From June 2010, new EU animal welfare regulations included stopping the use of lighting regimen with day length longer than 18 h to improve broiler welfare. Therefore, several different types of photoperiods have been tested to decrease susceptibility to metabolic diseases, skeletal disorders, and increase tibial breaking strength (Renden et al 1996;Ingram et al 2000;Sanotra et al 2002;Lewis et al 2009;Schwean-Lardner et al 2012. Moreover, lighting regimens maintain the vitality of anatomical stress indicators such as liver (Onbasilar et al 2007;Bayram and Ozkan 2010) and bursa of fabricius and spleen, which are main organs that could refer to the immunological status as well (Pope 1991;Heckert et al 2002;Blahova et al 2007;Ahmed and El-Ghamdi 2008).…”