نقايص مادرزادي در گوساله هاي نژاد هلشتاين گله هاي شيري

Congenital defects in calves of the Holstein breed of dairy farms

نقايص مادرزادي و اختلالات ارثي، ناهنجاريهايي در ساختمان، شكل، و وضعيت يا كاركردي هستند كه از بدو تولد وجود دارند. گوساله نوزاد ناقص، موجودي زنده و سازش يافته با رويدادي مخرب (disruptive event) است كه به وسيله توارث دام يا محيط زندگي دام در دوران جنيني يا به وسيله واكنش بين توارث و محيط ايجاد مي شود. مكانيسم ايجاد كننده نقايص را نقص در تشكيل (formation defects) مي ناميم. در بيشترين موارد جنين قبل از تكميل مراحل تكاملي مي ميرد و به شكل مرگ فتوس، موميايي شدن، سقط ، عدم تكامل، تولد نوزاد نارسو مرده زاييبروز مي نمايد. در غير اين صورت، بقيه مراحل تكامل به طورطبيعي طي مي گردد و بسته به دامنه نقايص، نوزادي با انحرافات خفيف از حالت طبيعي تا مبتلا به نقايص متوسط، شديد و حتي ناقص(عجيب)الخلقه متولد مي شود. با توجه به تفاوت محيط و توارث دام ها در گله هاي مختلف، فراواني و انواع نقايص نيز مي تواند به طور كامل متغير باشد. با وجود اين، دامنه تغييرات و ارزيابي هاي اوليه به ما در فهم ماهيت و اهميت نقايصي كه احنمالا با آنها مواجه مي شويم، كمك مي كنند.نكته بسيار مهم آن كه ميزان فراواني نقايص نه تنها به رويدادهاي مسبب نقايص، بلكه به ميزان دقت و جديت در معاينات و آزمايشات نيز بستگي دارد.

Congenital defects and inherited disorders, are abnormalities in the structure, shape and condition or function that exist from birth. An incomplete calf, is a live and compromised creature with a destructive event which is created by livestock inheritance or environment in fetal life, or by reaction between heridity and the environment. The mechanism that creates the defects is called defective formation. In most cases the fetus dies before it completes evolutionary stages and it happens in the form of fetal death, mummification, abortion, lack of development, premature birth and stillbirth. Otherwise, the rest of the stages of natural evolution will follow and depending on the extent of the defects, calf born with slight deviations from normal to moderte and severe defects, and even in the form of monsters. Due to difference in the environment and inheritance of livestock in different herds, the frequency and variety of defects can also be completely variable. Nevertheless, the range of changes and initial evaluations help us understand the nature and importance of defects.The very important thing is that the frequency of defects not only depends on the causes of the defects but also depending on accuracy and severity of the examination and tests. Evaluation of Congenital defects in calves of the Holstein breed of two large dairy farms Within six years in two large dairy farms, 16039 live calves for the possibility of congenital defects, were under clinical examination and or necropsied. The number of calves with congenital defects in two farms (one & two) were 270 (3.23%) and 150 (1.96%), respectively. A total of 420 (2.62%) defective calves were identified.