In cattle, the gene pair for red (RR) or white (WW) coat color shows an absence of dominance. Heterozygotes (RW) have a roan coat. Outline a breeding procedure to establish apure breeding herd of red cattle from a roan bull and white cow.
A cattle breed wants to establish a pure-breeding herd of roan cattle. What could you tell him about his chances for success in such a venture?
A farmer has three groups of cows: white ones int eh clover patch, red ones in the alfalfa field, and roa in the corn field. He has a roan bull named Ferdinand who services the cows in all three fiels. What color calves should he expect in each field?
Ferdinand dies from a bee sting and the farmer decides to make his herd exclusively roan coat in memory of his beloved bull. He sells all the red and white cows, and vows to sell any red or white calvesborn subsequently. What color bull should be bought to replace Ferdinand if he wants to sell as many calves as possible?
His chances of success are zero to none. Roan is heterozygous. That means you cannot have a pure breeding stock. The white cattle will produce 50% white and 50% roan. The red cattle will produce 50% red and 50% roan. The roan cattle will produce 25% white, 50% roan and 25% red. If he wants to sell as many cattle as possible, he should cross a white with a white or a red with a red.
To establish a pure breeding herd of red cattle from a roan bull and white cow, the following breeding procedure can be followed:
1. Start with a roan bull (RR) and a white cow (WW).
2. Allow them to mate naturally or through artificial insemination.
3. The resulting offspring will be heterozygotes (RW) with roan coats.
4. Select a red-roan bull (RR) from the offspring and breed it with a red cow (RR). This ensures that all the offspring will be red (RR).
5. When the red-roan bull (RR) reaches maturity, breed it with other red cows (RR) to produce purebred red cattle (RR) without any white gene present.
Regarding the success of establishing a pure-breeding herd of roan cattle, it is important to note that roan coat color results from heterozygosity (RW) rather than pure breeding (RR or WW). Therefore, it is not possible to achieve a pure-breeding roan herd through inheritance alone. However, by selectively breeding red-roan cattle, it is possible to maintain a consistent roan coat color in the herd.
In the clover patch, the calves would be white (WW) as the cows in that field are white (WW).
In the alfalfa field, the calves would be red (RR) as the red cows (RR) are present in that field.
In the corn field, the calves can either be roan (RW) or red (RR) depending on whether the roan bull (RW) mates with a roan cow (RW) or a red cow (RR).
If the farmer wants to sell as many calves as possible and aims to have them all roan, he should buy a red-roan bull (RR) to replace Ferdinand. Breeding the red-roan bull with the roan cows (RW) would produce a higher number of roan (RW) offspring, increasing the chances of having roan calves for sale.
To establish a pure breeding herd of red cattle from a roan bull and a white cow, you would need to follow a specific breeding procedure:
1. Mate the roan bull (RW) with the white cow (WW) to produce offspring with the genotype of RrWw (roan).
2. Select the roan offspring (RrWw) and mate them with each other to produce the desired red cattle. This mating will result in various genotypes, including red (RR), roan (RrWw), and white (Ww).
3. Continuously select the red offspring (RR) from each generation and mate them with each other to establish a pure breeding herd of red cattle.
In terms of the chances for success in creating a pure-breeding herd of roan cattle, it would depend on the desired level of purity. If the goal is a completely pure-breeding herd with no other coat color variations, it may take several generations of selective breeding to achieve this. However, if the goal is to have a predominantly roan herd with some color variation, it may be achievable in fewer generations.
In the case of the farmer's three groups of cows, mating with the roan bull, Ferdinand, would result in the following outcomes:
- White cows in the clover patch: The offspring would have the genotype RrWw, resulting in roan coat color.
- Red cows in the alfalfa field: The offspring would have the genotype RRWW, resulting in red coat color.
- Roan cows in the corn field: The offspring would have the genotype RrWw, resulting in roan coat color.
If the farmer wants to replace Ferdinand and create a herd exclusively with roan coat color, he should purchase a roan bull. This is because mating a roan bull with the remaining roan cows (RrWw) would increase the likelihood of producing roan calves (RrWw) and minimize the chances of red or white calves.