Genetic Conditions

The International Brangus Breeders Association is currently monitoring genetic conditions as they relate to pedigrees within the IBBA herdbook.
Questions regarding genetic conditions can be addressed to IBBA staff by calling 210-696-8231 or by email.

IBBA Genetic Defect Policy

The International Brangus Breeders Association Board of Directors has adopted a Genetic Defect Policy that can be downloaded.

Genetic Condition Result Definitions

Result Definition
Affected / Homozygous Recessive (A) Animal has been tested and has two (2) copies of the allele.
Carrier (C) Animal has been tested and has one (1) copy of the allele.
Free (F) Animal has been tested and exhibits zero (0) copies of allele.
Free Pedigree (FP) Animal has not been tested, but is predicted to be free by pedigree.
Potential Carrier (PC) Animal has not been tested, but is a potential carrier of the allele.

Genetic Condition Definitions

Condition Definition
Albinism (AB)  
Arthrogryposis Multiplex (AM) Arthrogryposis Multiplex (AM) is a lethal condition caused by a DNA deletion event within the genome of Angus and Angus-influenced cattle and exhibits a recessive inheritance pattern. Affected calves are known to be still-born with a twisted spine, and extended and contracted limbs. AKA Curly Calf Syndrome.
Contractural Arachnodactyly (CA) Contractural Arachnodactyly (CA) is a lethal disorder linked to a genetic condition caused by a recessive mutation that affects Angus and Angus-influenced cattle. While CA-affected calves are born alive, and most can walk, suckle and survive, their upper limb joints (particularly hip, stifle and hock) have a reduced range of motion. Affected calves appear normal by four (4) to six (6) months of age, but most perform poorly and are relatively tall and slender, with compromised feet and leg conformation. AKA Fawn Calf Syndrome.
PRKG2 Gene Mutation for Dwarfism (D2)  
Developmental Duplication (DD) Developmental Duplication (DD) and is genetically transmitted as a simple recessive gene. When the gene associated with DD is paired (two copies of same allele) in a mating, the results are either:

  • High probability of early embryonic death
  • Calves born with multiple limbs

Other than an increase in the occurrence of mortality associated with dystocia, calves born with polymelia (born with extra limbs) often thrive, especially with removal of the limb or limbs at or soon after birth. Those animals identified as carriers (only one recessive allele) show no visible signs of the genetic condition and typically lead a normal life.

Double Muscling (DM)) Double Muscling (DM) is a mutation which represses the myostatin protein, consequently augmenting muscle growth.
Dwarfism (DW)  
Horn Gene (HG)  
Heterochromia Iridis (HI) Heterochromia Iridis (HI) is a rare autosomal recessive mutation characterized by calves born with different colored irises.
nt821 Mutation for Double Muscling (M1)  
Alpha-Mannosidosis (MA) Lethal nervous disease of Angus and Angus-drived cattle. Cattle affected with Alpha-Mannosidosis usually fail to thrive and develop a progressive incoordination and an aggressive disposition when disturbed. Affected animals usually die before reaching sexual maturity.
Neuropathic Hydrocephalus (NH) Neuropathic Hydrocephalus (NH) is a lethal disorder linked to a genetic condition caused by a recessive mutation that affects Angus and Angus-influenced cattle. Affected calves are born dead with an extremely large cranium with little or no brain material or spinal cord. It is probable that a large percentage of mortalities relating to NH occur through embryonic or fetal loss during gestation, which causes the defect to go misdiagnosed or unnoticed. AKA Water Head Syndrome.
Osteopetrosis (OS) AKA Marble Bone.
Syndactyly (SN) AKA Mule Foot.