ABSTRACT This study aimed at evaluating beak-trimming methods and intensities on the performance, beak length and uniformity, and egg parameters of commercial layers. During the rearing period, birds were distributed in randomized blocks, with a 2x3 factorial design + two treatments, consisting of beak trimming with infrared (IR) radiation (moderate or severe); three IR intensities (low: 42 nm, intermediate: 46 nm, or high: 52 nm); and two control hot blade (HB) beak trimming treatments (moderate or severe) with eight treatments and five replicates of 21 chicks each, totaling 840 birds. During the growing phase (second experiment) the factorial design was modified to 2 x 3 x 2 + 4, comprising two IR beak-trimming intensities (moderate or severe); three IR radiation intensities (low, moderate and high), second beak trimming at 11 weeks of age or not, and four additional HB beak-trimming treatments (moderate or severe) beak-trimming intensities, and second beak trimming at 11 weeks of age or not. There were 16 treatments with six replicates of seven birds each, totaling 672 laying hens, out of which 576 were selected for evaluation during the production period, with the same number of treatments and replicates of the previous phase. Weight gain (g), body weight (g), body weight uniformity (%), beak length (mm) and uniformity (%), absence of cannibalism (%), livability (%), egg production (%), feed intake (g), feed conversion per eggmass, eggmass, specific gravity, eggshell strength, Haugh unit, % yolk were evaluated. Beak trimming by infra-red radiation may be employed in commercial laying hens.

ABSTRACT The aim of this study was to compare the effects of beak trimming by hot blade or infrared radiation on production indicators and plasma levels of corticosterone in pullets. During the rearing phase, an entirely random delineation was used a 2 x 3 factorial design (two different techniques for beak trimming x 3 strains), a total of six treatments with six repetitions of 20 hens. In the growing phase, the previous treatments were divided into 12, with eight repetitions with seven hens. These treatments were then distributed in a factorial design of 2 x 3 x 2 (two methodologies for beak trimming during rearing phase x three strains x with or without beak trimming at ten weeks of age). In the rearing phase the birds treated by infrared radiation had a lower total consumption and a longer beak length. In the growing phase, the execution of beak trimming at ten weeks of age, led to a lower total consumption and a lower body weight, but a better food conversion, when compared to those hens that did not have beak treatment. Beak trimming at ten weeks did not change the plasmatic levels of corticosterone.

A total of 405 23-week-old ISA® Brown layers were distributed in a completely randomized experimental design in a factorial arrangement with nine treatments consisting of three dietary calcium levels (3.5, 3.75, and 4.5%) and three limestone particle sizes (100% fine limestone (FL), 70% FL + 30% coarse limestone (CL) and 50% (FL) + 50% (CL)), with nine replicates of five birds per cage. The following parameters were evaluated: percentage of lay, defective eggs, egg weight, egg mass, feed intake, feed conversion ratio (per kg eggs and per dozen eggs), and mortality. Dietary Ca levels significantly affected lay, with birds fed diets containing 4.5% calcium producing less eggs as compared to those fed 3.0 and 3.75% Ca. Egg production linearly decreased as dietary Ca levels increased, but blood Ca levels (mg/L) increased in 28-week-old birds. The interaction of dietary Ca levels and limestone particle sizes resulted in a reduction in tibial ash Ca content as dietary Ca levels increased and as fine limestone was replaced by coarse limestone. It is concluded that a dietary Ca level of 3.75% and 100% fine particle limestone are required to maintain adequate egg production and available Ca blood level.

This study aimed at studying alternative methods to induce molting and to compare them with the conventional forced-molting method (fasting). In the experiment, 420 70-week-old layers were used. The total experimental period was 140 days. Molting was induced during the first 28 days, when birds were submitted to the experimental treatments, and bird performance and egg quality parameters were determined during 112 subsequent days. A completely randomized experimental design was applied in a 5x2 factorial arrangement of five feed restriction regimes (0, 15, 30, 45, or 60g feed/bird/day) and with or without the addition of coarse-particle limestone to the feed, with seven replicates of six birds each. Egg quality was evaluated at the end of each 28-day period for three consecutive days, using three eggs per experimental unit (21 eggs/treatment), with a total of 210 eggs. It was concluded that feeding 15g feed/bird/day to induce molting is feasible, as birds submitted to this treatment presented similar performance and better egg quality than those submitted to fasting during molting. The use of coarse-particle limestone during molting did not influence post-molting bird performance or egg quality.

This study evaluated the effect of dietary calcium levels and limestone particle size distribution on first-cycle layer performance and egg quality. A completely randomized experimental design in 4x3 factorial arrangement (four Ca levels - 3.0, 3.5, 4.0, 4.5%; and three limestone particle size distributions - 100% fine, 50% fine and 50% coarse, 30% fine and 70% coarse) was applied, totaling 12 treatments with six replicates of eight birds each. The treatments did not influence the most of evaluated performance and internal and external egg quality parameters. However, limestone particle size distribution quadratically affected with percentage of defective eggs, with the lowest percentage obtained with the distribution 61.75% fine limestone and 38.25% coarse limestone. Increasing dietary Ca levels significantly increased eggshell weight per surface area and the percentage of Ca excreted in the feces. It was concluded that the combination of the highest dietary Ca level (4.5%) with 50% replacement of fine-particle limestone by coarse limestone results in better eggshell and increases the number of marketable eggs.

This experiment studied the effect of four calcium (3.0, 3.5, 4.0, and 4.5%) and four available phosphorus levels (0.25, 0.30, 0.35, and 0.40%) in the diet of semi-heavy commercial layers after molting. Hisex Brown® layers between 90 and 108 weeks of age were distributed in a completely randomized experimental design with a 4x4 factorial arrangement with 16 treatments of five replicates of eight birds each. mortality, egg production, feed intake, egg mass, average egg weight, calcium and phosphorus intake, feed conversion ratio (per dozen eggs and per kg eggs), eggshell percentage and thickness, eggshell strength, eggshell weight per surface area (ESWSA), yolk percentage and color, albumen percentage, albumen and yolk heights, and blood and excreta calcium and phosphorus concentrations. There was no interaction (P>0.05) between dietary Ca and avP for any of the studied parameters. There were linear increases in Ca intake (P<0.01), eggshell percentage (P<0.05); ESWSA (P<0.05); yolk color (P<0.05); Ca concentration in the blood (P<0.05) and excreta (P<0.01) as dietary Ca level increased. The intake of avP linearly increased (P<0.01) with dietary avP levels. The remaining parameters were not influenced (P>0.05) by dietary Ca and avP levels. The diet containing 4.5% calcium improved feed conversion ratio per dozen eggs and eggshell quality. The lowest avP level fed (0.25%) is sufficient to maintain the performance and the egg quality of semi-heavy commercial layers after molting.