J. J. R. Feddes

Bone Mineral Density and Breaking Strength of White Leghorns Housed in Conventional, Modified, and Commercially Available Colony Battery Cages

Limited opportunity for movement and load-bearing exercise for conventionally caged laying hens leads to bone loss and increased susceptibility to osteoporosis, bone fractures, and cage layer fatigue, all of which compromise hen welfare and have negative consequences for production. The objective of this study was to compare bone mineral density (BMD) and strength measures of White Leghorns housed in conventional battery cages (CONV), cages modified to incorporate a nest box and perch (MOD), and commercially available, furnished colony cages with (CWDB) or without (CWODB) a raised dust bath. Hens reared on floor litter were randomly allocated to 1 of 4 cage systems at 19 wk of age. Hen-day production and egg quality were measured between 20 and 64 wk. At 65 wk, hens were killed, and right femur, tibia, and humerus were excised. Bone mineral density was assessed using quantitative computed tomography, and breaking strength was measured with an Instron Materials Tester. In the femur and tibia, CONV hens exhibited lower total BMD, bone mass, cortical bone area, cortical bone mass, and bone-breaking strength than CWDB, CWODB, and MOD hens. Density and cross-sectional area of bone in the trabecular space was highest in CONV. In the humerus, total and cortical BMD and mass and breaking strength values were higher for colony-housed birds than hens in CONV and MOD. The MOD birds did not exhibit increased humeral BMD or strength measures over CONV hens. These findings provide evidence that hens housed in modified and colony cages, furnished systems that promote load-bearing movement, are better able to preserve cortical structural bone than conventionally caged hens and simultaneously have stronger bones. Furthermore, inclusion of raised amenities that encourage wing loading is necessary to reduce humeral cortical bone loss. The overall absence of correlation between egg production or quality and bone quality measures also suggests that improved bone quality in CWDB, CWODB, and MOD furnished cages is not the result of lowered egg production or quality.

The Effects of Body Weight and Long Ahemeral Days on Early Production Parameters and Morphological Characteristics of Broiler Breeder Hens

Shaver Starbro broiler breeder pullets were used to study the effect of day length (24 and 28 h) on egg production parameters and egg traits from 22 to 30 wk of age, and ovarian and morphological characteristics at 30 wk of age. Floor-housed pullets were raised in a light-tight facility from 1 d of age until housing in individually illuminated cages at time of photostimulation (22 wk). Cages were equipped with hardware to monitor egg laying time. The photoschedule during rearing was 24 h light: 0 h dark for the first 3 d followed by 8 h light: 16 h dark from 3 d to photostimulation. Body weight was monitored throughout the trial to maintain weights at targets set by Shaver Poultry Breeding Farms, Ltd. The experimental design was a 2 x 2 factorial with two day lengths [hemeral (24 h) and ahemeral (28 h)] and two BW groups [high (HBW) and low BW (LBW)], with the LBW weighing 327 g less than the HBW birds at 22 wk of age. The hemeral photoschedule was 14 h light: 10 h dark, and the ahemeral photoschedule was 14 h light: 14 h dark. Differences in BW remained throughout the trial. Egg numbers were not increased by the 28-h day (24 h = 25.4 eggs; 28 h = 23.1 eggs). The 24-h hens laid more double-yolked eggs (0.9% of total egg production) than did the 28-h birds (0.3%). Egg formation time was consistently longer for the 28-h hens (26.8 h at 25 wk of age and 25.8 h at 29 wk of age) compared with the 24-h hens (25.4 h at 25 wk of age and 24.8 h at 29 wk of age). Mean egg weight was higher for the 28-h birds (55.1 g) compared with the 24-h birds (53.0 g). Egg specific gravity was higher in eggs from the 28-h hens than eggs from the 24-h hens. Some of the increase in egg weight between the 28- and 24-h birds was due to shell weight. Absolute and proportional weights of the egg shell were 5.5 g and 10.0% of the total egg weight for the 28-h birds and 4.9 g and 9.3% for the 24-h birds, respectively. The 28-h hens had higher proportional breast muscle weight, smaller livers and oviducts, and lower ovary weight compared with the 24-h birds. The data indicated that, although egg size can be increased with the use of long ahemeral days early in lay, this result may be at the expense of egg numbers. Early in lay, follicular maturation rates are fast, and egg production may be limited to one ovulation per 28 h.

Influence of parent flock age on embryonic metabolism in modern turkey strains

The metabolic response of some galliform embryos to embryonic heat production (EHP) and how incubation conditions have been adjusted to prevent overheating of embryos is well established in broiler breeders. However, the daily metabolic status of turkey embryos has not been studied or established in turkey embryos. The objectives of the current research were therefore to determine the respiratory (eggshell conductance, G) and metabolic status (EHP) of 2 modern turkey genetic strains [Hybrid (H) and Nicholas (N)] and 4 parent flock ages [young (Y, 30 wk), peak (P, 34 wk), mature (M, 55 wk), and old (O, 60 wk)] during incubation. To measure G, moisture loss from 15 eggs/genetic strain per flock age and saturated vapor pressure measured between the eggshell and its immediate environment were used. Daily embryonic O(2) consumption and CO(2) production rates were assessed 6 times each day from embryos of eggs (n = 11 eggs/genetic strain per flock age) incubated in individual metabolic chambers and were used to determined daily EHP. Data were analyzed using the mixed model procedure of SAS at P ≤ 0.05. The results showed that the G values (g/d per mmHg) were significantly different for the interaction between genetic strain and parent flock age (H × Y = 17.71, H × P = 17.53, H × M = 19.73, H × O = 26.46, N × Y = 16.70, N × P = 20.96; N × M = 25.47, N × O = 26.05; P = 0.0227). Daily EHP (mW) was higher in embryos from the O flock than in embryos from the Y flock during all days presented except at 8, 25, and 28 d of incubation (4 d: Y = 1.00, P = 0.93, M = 1.60, O = 1.75; 12 d: Y = 19.0, P = 20.0, M = 21.6, O = 23.4; 16 d: Y = 51.7, P = 60.5, M = 65.9, O = 70.8; 20 d: Y = 129, P = 146, M = 144, O = 155; 24 d: Y = 154, P = 188, M = 167, O = 180; 26 d: Y = 169, P = 199, M = 197, O = 230; and 27 d: Y = 231, P = 265, M = 288, O = 307; P < 0.05). The data showed that metabolic differences existed between embryos from flocks of different ages and that embryos from older flocks were metabolizing at a higher rate and could be subject to overheating, which requires further investigation. On the basis of the data, turkey eggs from flocks of different ages should be incubated separately for optimal physiological performance.