Inheritance of bone characteristics affecting osteoporosis in laying hens

Abstract

1. Heritabilities of a range of morphometric, radiological and strength characteristics were measured in the bones of end-of-lay hens. 2. Tibial strength (TSTR), humeral strength (HSTR) and keel radiographic density (KRD) were moderately to strongly inherited and were combined in a Bone Index which was used as a basis for selection. Data are available on 6 generations/cohorts of hens (n=1306), the last 3 of which are the progeny of divergently selected birds. 3. All bone characteristics used in the Bone Index responded rapidly to divergent selection and were strongly correlated with each other. In the last generation, the lines differed by 25% for TSTR, 13% for HSTR and 19% for KRD. The heritability of the index was 0.40. 4. There were no apparent genotype by environment interactions between birds housed at 2 different locations. 5. The incidence of bone fractures was significantly decreased in the line selected for high bone strength compared to the line selected for low bone strength. Humerus fracture incidence differed by a factor of 6 between the lines in the last generation. There was a strong quadratic relationship between tibia strength and overall fracture incidence (r2=0.92, P<0.01). 6. The results imply that selection for enhanced bone strength can be used as a long-term strategy for alleviating the problems of osteoporosis in laying hens.

Identification of quantitative trait loci associated with bone traits and body weight in an F2 resource population of chickens

“…A significant positive phenotypic correlation between body weight and bone strength in chickens has been reported previously [4,34,41], and was observed in the F2 resource population. However, adjusting for body weight did not remove the difference in BMD observed between the layer and broiler lines, suggesting there is a significant difference in BMD that is independent of body weight.…”

“…Mandour et al [32] demonstrated an increase in humerus strength following three generations of selection in a population of broilers, where selection was based on an index of bone traits measured in progeny. Similarly, Bishop et al [4] reported a 2-fold improvement of bone strength in chickens after seven generations of divergent selection for a bone index. Although these selection experiments demonstrate that improvements in bone integrity can be made through genetic selection, they rely on measurement of traits that require euthanasia of the bird.…”

“…Additionally, variation in bone strength is influenced by genetics, with heritability estimated as 0.40 [4]. Mandour et al [32] demonstrated an increase in humerus strength following three generations of selection in a population of broilers, where selection was based on an index of bone traits measured in progeny.…”

Changes in the expression of genetic characteristics across cohorts in skeletal deformations of farmed salmonids

“…Second, it is possible that after the splitting, the same families were independently subjected to deformations in both environments. On the one hand, the first explanation seems intuitive because egg incubation and early growth are critical phases for skeletal development in fish and other animals [2,30]. On the other hand, the second explanation is supported by detailed studies of fish bone structure, showing that deformations may appear in later life stages [33].…”

Nutritional factors affecting poultry bone health

“…Although OP in hens has strong genetic and environmental components (8,9) , nutritional approaches can also alleviate the condition (10,11) . The timing of nutritional intervention is critical, however.…”