BOVINE CITRULLINAEMIA
In animal breeding, genetic disorders are one of the most important issues for breeders. These monogenic recessive autosomal defects cause early embryonic mortality, abortion or death at early age after birth. Widespread use of artificial insemination (AI) and international trading of semen and breeding bulls accelerates the spread of undesirable genes in population. Regular screening of the breeding bulls used for AI reduces the risk of dissemination of these deleterious genes in the animal population.Four major genetic disorders namely Bovine Leukocyte Adhesion Deficiency (BLAD), Citrullinaemia, DUMPS (Deficiency of Uridine Monophosphate Synthase), Factor XI deficiency syndrome are tested in the laboraotory.
Bovine Citrullinaemia is anautosomal recessive inherited disorder of urea cycle that is lethal in early postnatal period. It is a consequence of a deficiency of argininosuccinate synthase (ASS), one of the enzymes of the urea cycle.Calves affected with bovine citrullinaemia appear normal immediately after birth. However, between the 3rd and 5th day, the disease progresses rapidly. Deathusually occurs within 12 hours of onset of these clinical signs. The clinical signs of citrullinaemia are believed to be a consequence of accumulation of ammonia in the brain of the affected calves.
Genetic disorders cause physical or functional anomalies by producing negative impact on vitality. Bovine citrullinaemia (BC) is a Holstein-specific autosomal recessive genetic disorder (Meydan et al., 2010). With the wide use of artificial insemination (AI) and international trading of semen and breeding bulls, the genetic diseases have already been spread to a large population, as animal carriers of the diseases look normal. In India, where Holstein Friesian (HF) bulls and their semen are extensively used for crossbreeding programmes with indigenous cattle, it has become necessary to screen all HF and HF crossbreds, especially AI bulls, to minimize the risk of spread of these diseases among future bulls or bull mothers (Patel et al., 2007). In BC the homozygous cattle dies during the first seven days of life (Robinson et al., 1993). The carriers of BC have been detected in USA (Robinson et al., 1993) and Australia (Healy et al., 1991). There is insufficient information of BC determination and its incidence in Madhya Pradesh. Polymerase Chain Reaction – Restriction Fragment Length Polymorphism (PCR-RFLP) is the most reliable and inexpensive method for identification of BC. The investigation was therefore, undertaken with the objectives to standardize PCR-RFLP technique for the detection of BC in Holstein Friesian and its crosses, to find out the incidence of BC and to determine their gene and genotype frequency.
Bovine Citrullinaemia is a genetic disease, which has only been reported in Holstein cattle (Fesus et al., 1999). It is urea cycle disorder in humans and animals. A deficiency of the urea cycle enzyme results in a lethal neurological disease in newly born calves. The urea cycle involves a series of biochemical steps in which nitrogen, a waste product of protein metabolism, is removed from the blood and converted to urea. Calves affected with the disease appear normal immediately after birth. However, by the second day of life they become depressed and feed poorly. By the third day, they are often seen aimlessly wandering about their enclosure or standing with their head pressed against a fence or wall. Between day 3 and 5 the disease progresses rapidly. The calves appear to be blind and then they collapse. Death usually occurs within 12 hours of onset of these clinical signs (Healy et al., 1990). The clinical signs of Citrullinaemia are believed to be as a consequence of accumulation of ammonia in the brain of the affected calves. Bovine Citrullinaemia was reported in Australia in 1986 (Harper et al., 1986) and the mutation responsible traced to a North American sire named Greyview Crisscrossh, the semen of whose son Linmack Kriss King (LMKK) was used extensively in Australia (Healy et al., 1991). About 8% of bulls considered for Artificial Insemination in Australia have proven to be heterozygous for the defective gene. LMKK-derived semen has been used extensively in New Zealand. However, no carriers were found black & white cattle in Germany (Grupe et al., 1996), Korea (Lee et al., 2002), India (Patel et al., 2006), Czech Republic (Citek et al., 2006), Turkey (Oner et al., 2010) and Iran (Eydivandi et al., 2012). Many carriers were detected in Australia (Healy et al., 1991), USA (Robinson et al., 1993), India (Muraleedharan et al., 1999), Hungary (Fesus et al., 1999), Taiwan (Lin et al., 2001), China (Mei et al., 2009; Li et al., 2011), etc. It has been established that bovine Citrullinaemia is a consequence of a deficiency of Argininosuccinate synthetase (ASS), one of the enzymes of the urea cycle. The deficiency of ASS occurs when a calf inherits a copy of the mutant gene encoding for ASS from each parent. The mutation occurs almost in the center of a particular segment of ASS DNA. The mutation is caused by a transition of cytosine (CGA/ Arginine) to thymine (TGA/stop codon) at codon 86 within exon 5 in the gene coding for ASS leading to impaired enzyme, which cannot participate in urea cycle (Dennis et al., 1989). The gene is located on chromosome No.11 (BTA11).
Compiled & Shared by- Team, LITD (Livestock Institute of Training & Development)
Image-Courtesy-Google
Reference-On Request.
