Understanding semen catalog

Genetic Improvement Program - Results

Analysis Model for Genetic Evaluation and breeding values:

In this case, an Animal Model with Repeated Observations was applied for the estimation of the genetic values of the sires through the use of the MTDFREML software package (Boldman et al., 1995). The effects included in this analysis model were:

  • Fixed effects:
    • Herd-Year Interaction (915 levels),
    • Kidding Month (12 levels),
    • Type of Kidding (5 levels)
  • Linear and quadratic covariate: Age of the goat at birth.
  • Random effects:
    • Additive genetic value of the animal.
    • Permanent Environmental Effect (26,982 levels).

The response variables were the production in kilograms of milk, fat, protein and total solids, all standardized to 210 days.

Population Milk Production and Components

The table below shows the results of milk production averages in the 2019 evaluation. All the sires in this catalog come out of the selective nucleus.

Understanding Casein Genotype

Protein is one of most important milk components and it is essential for cheese making as it is the main component that determines cheese yield. Caseins represent between 75 to 80% of total milk proteins. There are four different types of casein proteins: αs1-, αs2-, β-, and κ-caseins (alpha s1, alpha s2, beta and kappa, respectively), each type of casein has a different roles during the process cheese making, from coagulation to maturation.

The milk content of caseins is determined by the genotype of an animal and there are several different possible genetic combinations of alleles (genetic polymorphism) leading to different amounts of caseins in milk.

There are strong alleles leading to a higher amount of casein and weaker alleles leading to lower amount of casein in the milk. The table bellow shows the different alleles for the αs1 and κ-casein.

For example:
A buck which genotype for ?s1-Casein is BB means that all his progeny will have at least one allele B. His progeny will have at least on B (strong Allele). And therefore it will. by it self, increase protein content of his daughter’s milk. On the contrary if a Buck genotype has weak or null alleles (FF, NN, FN etc…) will not increase the protein production of his daughters.

Genotyping of Caseins is very important when considering milk and cheese making asein (alfa s1 casein) is associated with high protein and also fat content while ?-casein (kappa-casein) is associated with .

The MG Goat breeder’s association has genotyped all the males at the Semen Collection Center for the αs1 and κ-casein.