Random amplified polymorphic DNA comparisons among broiler lines selected for incidence of tibial dyschondroplasia

The effects of broiler chicken growth rate on valgus, varus, and tibial dyschondroplasia

An experiment was conducted to test the hypothesis that the growth rate of broilers influences their susceptibilities to bone abnormalities, causing major leg problems. Leg angulations, described in the twisted legs syndrome as valgus and bilateral or unilateral varus, were investigated in 2 subpopulations of mixed-sex Arkansas randombred broilers. Valgus angulation was classified as mild (tibia-metatarsus angle between 10 and 25°), intermediate (25-45°), or severe (> 45°). Body weight was measured at hatch and weekly until 6 wk of age. There were 8 different settings of approximately 450 eggs each. Two subpopulations, slow growing (bottom quarter, n = 581) and fast growing (top quarter, n = 585), were created from a randombred population based on their growth rate from hatch until 6 wk of age. At 6 wk of age, tibial dyschondroplasia incidences were determined by making a longitudinal cut across the right tibia. The tibial dyschondroplasia bone lesion is characterized by an abnormal white, opaque, unmineralized, and unvascularized mass of cartilage occurring in the proximal end of the tibia. It was scored from 1 (mild) to 3 (severe) depending on the cartilage plug abnormality size. Mean lesion scores of left and right valgus and tibial dyschondroplasia (0.40, 0.38, and 0.06) of fast-growing broilers were higher than those (0.26, 0.28, and 0.02) of slow-growing broilers (P = 0.0002, 0.0037, and 0.0269), respectively. Growth rate was negatively associated with the twisted legs syndrome and a bone abnormality (tibial dyschondroplasia) in this randombred population.

Within- and between-strain genetic variability in White Leghorn population detected through RAPD markers

1. Five White Leghorn (WLH) strains, namely G, H, I, J and C, differing in selection history, were screened for randomly amplified polymorphic DNA (RAPD) polymorphism using 50 random decamer primers. 2. Only 12 primers detected polymorphism between the strains. Out of 96 bands scored using these primers, only 21 (21.9%) were found to be polymorphic. 3. Strains differed considerably for within-population genetic similarity, estimated either by band sharing (WS=0.836 to 0.968) or band frequency (WF=0.820 to 0.969). 4. Between-strain genetic similarity estimates, based on band sharing (BS) as well as on band frequency (BF) ranged from 0.756 to 0.958 and from 0.830 to 0.996, respectively. Strains C and H were most closely related to each other, while J appeared to be more distant from other strains. 5. The between-strain genetic distance estimates also revealed similar trends. 6. A phylogenetic tree, derived using Nei's coefficient of similarity revealed similar relationships between the WLH strains.

Genetic distinctness of African, Asian and South American local chickens

The genetic variability of various local chicken populations derived from Bolivia, India, Nigeria and Tanzania was evaluated with 22 microsatellites. Between two and 11 alleles per locus were detected. All populations showed high levels of heterozygosity with the lowest value of 45% for the population named Aseel from India and the highest value of 67% for Arusha from Tanzania. A dendrogram was constructed based on CHORD distance by upgMa analysis. Within this tree the populations were assorted according to their geographical origin. Bootstrapping values within the dendrogram were between 37 and 99%. The contribution of the determination of genetic variability with genetic markers to the decision on conservation and/or further use of the populations in crossbreeding programs designed to create genetic stocks with improved adaptability and productivity in tropical countries is discussed.

Measurement of within and between population genetic variability in quails

1. To detect polymorphism in various quail lines, Randomly Amplified Polymorphic DNA (RAPD) markers were tested and were found to be effective. 2. Twenty decamer primers were selected at random and tested, and 6 of these generated distinct polymorphic patterns between the quail lines. 3. Out of a total of 60 bands amplified using 6 selected primers, 19 (31.7%) were found to be polymorphic. 4. Genetic similarity within the lines ranged from 0.726 in HBW to 0.836 in KLQ. 5. Genetic similarity estimates between the populations ranged from 0.709 to 0.808.

Randomly amplified polymorphic DNA (RAPD) for evaluating genetic relationships among varieties of guinea fowl

The present study investigated the use of randomly amplified polymorphic DNA (RAPD) in estimating the intra and inter varietal genetic variation in three varieties of guinea fowl (Lavender, Pearl and White). The estimates, measured as band sharing were high for within population (0.946-0.971) and between population (0.990-0.999) genetic similarity. The respective estimates were 0.898-0.929 and 0.923-0.928 when estimated as frequency of occurrence of bands. The results indicated a very low level of intra and inter varietal genetic variation in these guinea fowl varieties, which in turn suggested the low level of genetic variation in these populations. The possible reasons for this high genetic similarity has been discussed.

Use of randomly amplified polymorphic DNA markers for the genetic analysis of relatedness and diversity in chickens and turkeys

A study involving the use of random amplified polymorphic DNA (RAPD) was conducted to evaluate genetic polymorphism and relatedness within and among four chicken breeds: Araucona, Rhode Island Red, White Leghorn, and White Plymouth Rock, and two turkey populations, a long-term randombred and a commercial strain. A total of 60 random primers were used in the RAPD analyses. Forty-two of the 60 primers tested amplified patterns with at least one polymorphic fragment in one or more of the populations. Six of these 42 primers amplified polymorphic fragments in each of the six strains with a within- and between-population average band-sharing frequency of less than one but above zero (P < 0.05). Differences among the six primers for genetic distance (D) among populations were significant (P < 0.05). A consensus dendogram was therefore developed to show the phylogenetic relationships among the populations. As expected, estimates of D between populations were lowest within species and highest between species. The results provide evidence of the applicability of RAPD to determining genetic relatedness within and among different poultry populations and in developing reproducible markers useful in evaluating individual variation in chickens and turkeys.