# Presentation: 566833

## Considering Inbreeding in Making Breeding Decisions

## What is inbreeding?

**The likelihood that an animal inherits the same gene from each parent because the parents have ancestors in common**

## Why is inbreeding important?

**The higher the inbreeding, the more likely deleterious recessives will be expressed**
**Inbreeding depression = the resulting reduction in performance**

## Inbreeding depression per 1% inbreeding

| Milk | -65.3 | lb | DPR | -0.078 | % |
| --- | --- | --- | --- | --- | --- |
| Fat | -2.37 | lb | SCS | +0.003 | score |
| Protein | -2.14 | lb | PL | -0.2 | mo |

## How inbreeding is used in calculation of PTA’s

**Lactation records and relationship matrix are adjusted for inbreeding**
**Evaluations are adjusted for expected future inbreeding**
**Expected future inbreeding is half the relationship of the animal to 600 recent cows**

## Benefits of AIPL procedure

**Bull not penalized if daughters are inbred**
**Bulls docked if they are more highly related to potential mates than average**

## Ten most highly related Holstein sires to cows in Aug 2005inbreeding coefficient calculated to 1960 base

| Name | BYR | Bull F | Past F | Exp. F |
| --- | --- | --- | --- | --- |
| TO-MAR BLACKSTAR-ET | 1983 | 4.7 | 3.9 | 7.9 |
| ROUND OAK RAG APPLE ELEVATION | 1965 | 0.0 | 1.2 | 7.6 |
| PAWNEE FARM ARLINDA CHIEF | 1962 | 0.0 | 0.3 | 7.4 |
| MJR BLACKSTAR EMORY-ET | 1989 | 4.3 | 4.7 | 7.1 |
| WA-DEL RC MATT-ET | 1989 | 4.5 | 4.9 | 7.0 |
| CAL-CLARK BOARD CHAIRMAN | 1976 | 1.6 | 3.0 | 6.9 |
| KED JUROR-ET | 1990 | 4.5 | 5.1 | 6.9 |
| S-W-D VALIANT | 1973 | 0.0 | 1.1 | 6.8 |
| RICECREST EMERSON-ET | 1994 | 5.0 | 5.4 | 6.8 |
| WALKWAY CHIEF MARK | 1978 | 0.0 | 2.7 | 6.6 |

## Limitation of AIPL procedure

**PTA is not adjusted for the bull’s relationship to a particular mate**

## What can be done about inbreeding?

**When breeding a cow, use an unrelated sire**
**Progeny of a highly inbred cow will not be inbred if she and the mating sire have no common ancestors**

## Is this practical?

**Usually, no**
**Intensive selection has led to rising levels of inbreeding**
**Popular sires are likely to be related to many cows**

## Holstein Inbreeding

## What are mating programs?

**Computer programs that recommend a service sire for a cow**
**The more pedigree data they have, the better recommendations they can make**
**Use of a mate that will cause higher inbreeding in the calf is justified if the superiority in PTA exceeds the additional inbreeding depression**

## Examples of mating programs

**Holstein Inbreeding Calculator**
**Jersey-Mate**
**Stud programs**

## Crossbreeding

**Mating parents of different breeds**
**Provides relief from inbreeding**
**Heterosis**** – superiority over the average of the parents**

## Average heterosis value

| Milk | +700 | lb | DPR | +1.8 | % |
| --- | --- | --- | --- | --- | --- |
| Fat | +35 | lb | SCS | +0.02 | score |
| Protein | +26 | lb | PL | +0.3 | mo |

## Crossbreds in genetic evaluations

**Methods to include records of crossbreds are being developed**
**All breeds can be included in the same evaluation**
**Requires pedigree of crossbreds including parental breed**
**On farm software may choke on:**
**Norwegian Red**
**Montbéliard**
**Ranking depends on breed of mate**

## Conclusions

**Inbreeding reduces productivity**
**Semen should be allocated to minimize the inbreeding of progeny**
**Mating programs can be profitable**
**Crossbreeding gives heterosis (relief from inbreeding depression)**
**Genetic evaluations that include crossbreds are coming**

## Other research at AIPL

**Evaluations for:**
**Stillbirth**
**Male fertility**
**Persistency**
**Disease resistance**
**Change in PL to credit longer lactations**
**Detecting abnormal distributions of calving ease scores**

## Other research at AIPL (Cont)

**Parentage verification based on Single Nucleotide Polymorphisms (SNP)**
**Determine the rate of parentage errors**
**Using SNP to trace inheritance of chromosomal segments**
**Potential to greatly increase accuracy of parent average**