Closure exposure of brain or spinal tissue other

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Unformatted text preview: ws Belgian Blue X Braford Crossbred Calves: All Sold as Feeders Tibial Hemimelia --A new defect in Shorthorns • skeletal defects • failure of pelvic fusion – abdominal hernia • shortened or absent tibia – severe distortion of rear leg structure • failure of proper neural tube closure – exposure of brain or spinal tissue • other defects • Severe abdominal hernias, cryptorchidism, invariably lethal • calves may be born alive – fail to thrive, euthanized Background • recognized in Galloway cattle in early 70‟s (Ojo et al. 1974) – genetic inheritance • Reported in in Shorthorn cattle in 2000 (Lapointe et al., 2000) – 3 of 6 calves reported of Canadian origin • ancestry common among all calves Genetics – unaffected parents (i.e., normal is dominant) – equal frequency among sexes – pedigree analysis reveals common ancestry on both sides of pedigree – expected ratios of offspring among matings between carrier (heterozygous) parents • 3:1 ratio of normal to affected offspring • recessive Mendelian inheritance • animals homozygous for defect (mutation) are affected • both parents of affected calves must be carriers Potential Impact • worldwide – putative common ancestor is early Irish import • one of few direct imports – extensively used • circa ~1975 – multiple generations of dispersion • US (2004 perspective) – more than half of the top 10 sires for number of Shorthorn registrations are putative carriers – popular club calf sire is suspected carrier • estimated 80,000 units of semen sold – In 2005, 21 of 24 black, composite AI sires offered by a single vendor are tested as carriers Curiosities • selection paradox – carriers are the “best” • probably led to greater use of heterozygous sires – non-pathological manifestation in heterozygotes? • structural differences in hindquarters Pulmonary Hypoplasia with Anasarca (PHA) • pulmonary hypoplasia • absent or near absence of lungs – normal cardiovascular system • anasarca • tremendous fluid accumulation in affected calves • lack of lymphatic development – absence of lymph duct and nodes, athymia • invariably lethal • all near term calves born dead • other • early embryonic lethal – increased open rate after confirmed pregnancy Genetics – unaffected parents (i.e., normal is dominant) – equal frequency among sexes – pedigree analysis reveals common ancestry on both sides of pedigree – deficiency of affe...
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This note was uploaded on 07/16/2011 for the course ANS 3384 taught by Professor Olson during the Spring '09 term at University of Florida.

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