# Presentation: 349356

## Heterosis and breed differences for daughter pregnancy rate and calving ease in crossbred dairy cows

## Objectives

**Document the number and type of crossbred dairy animals in the US.**
**Estimate heterosis and breed differences for DPR and calving ease of F1 cows.**

## Crossbred Animals

**Animals are considered crossbred if available pedigrees include ancestors of more than one breed. **
**AIPL crossbred table includes over 335,000 animals of which 80,211 are F1s.**
**Crossbreds are currently updated with every evaluation.**

## Daughter Pregnancy Rate

**AIPL database has over 32 million records**
**Days open restricted from 50 to 250 d**
**Pregnancy Rate = .25 * (233 - DO)**
**Calvings since 1990**

## Daughter Pregnancy Rate

**First lactation records **
**13,540 F1 cows from 5397 herds**
**200,992 purebred contemporaries**
**Lactations 1 to 5**
**507,584 records from 6223 herds**

## DPR Model Effects

**Herd-year-season of calving**
**Linear and quadratic effects for age at first calving **
**Lactation number**
**Regression on sire PTA**
**Breed composition**
**General heterosis**

## Number of F1 and Purebred Cows first lactation

| Sire | Dam Breed |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Breed |  | AY | BS | GU | HO | JE | MS |
| AY |  | 1857 | 3 | 13 | 268 | 26 | 3 |
| BS |  | 3 | 1163 | 22 | 2262 | 59 | 11 |
| GU |  | 4 | 14 | 1892 | 286 | 20 | 0 |
| HO |  | 629 | 526 | 1584 | 186,902 | 883 | 254 |
| JE |  | 49 | 53 | 84 | 6232 | 8825 | 4 |
| MS |  | 6 | 6 | 5 | 222 | 9 | 353 |

## Number of F1 and Purebred Cows all lactations

| Sire | Dam Breed |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Breed |  | AY | BS | GU | HO | JE | MS |
| AY |  | 1990 | 3 | 14 | 300 | 29 | 4 |
| BS |  | 4 | 1331 | 41 | 2538 | 69 | 13 |
| GU |  | 7 | 23 | 1977 | 335 | 26 | 0 |
| HO |  | 712 | 600 | 1810 | 193,247 | 1038 | 316 |
| JE |  | 55 | 59 | 103 | 6841 | 9438 | 5 |
| MS |  | 6 | 6 | 7 | 260 | 12 | 409 |

## Daughter Pregnancy Rate

|  |  | First Lactation | All   Lactations | Breed Average |
| --- | --- | --- | --- | --- |
| Heterosis |  | 2.4 ± 0.6*** |    1.8 ± 0.4*** |  |
| AY |  | 0.7 ± 0.8 |    1.6 ± 0.4 | + 0.5 |
| BS |  | 0.6 ± 0.7 | — 0.2 ± 0.4 | — 0.4 |
| GU |  | 1.6 ± 1.1 |    1.6 ± 0.7** | — 1.0 |
| JE |  | 4.2 ± 0.4*** |    4.6 ± 0.2*** | + 4.7 |
| MS |  | 4.3 ± 1.7** |    4.0 ± 0.9** | + 3.7 |

## DPR Conclusions

**Estimates are similar to breed differences obtained from national breed averages of first lactation DPR.**
**JE x HO crossbreds are as fertile as purebred JE.**
**Heterosis is about 10% of mean DPR.**

## Calving Ease of F1s

**First lactation raw difficult birth score records **
**1861 F1s from 1165 herds**
**42,564 purebred contemporaries **
**Lactations 1 to 5**
**91,172 records from 2022 herds**

## Number of F1 and Purebred Cows calving ease - first lactation

| Sire | Dam Breed |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Breed |  | AY | BS | GU | HO | JE | MS |
| AY |  | 16 | 0 | 0 | 44 | 2 | 1 |
| BS |  | 0 | 65 | 1 | 535 | 3 | 3 |
| GU |  | 0 | 0 | 75 | 25 | 1 | 0 |
| HO |  | 27 | 76 | 89 | 42,128 | 86 | 6 |
| JE |  | 1 | 6 | 5 | 923 | 278 | 2 |
| MS |  | 1 | 0 | 0 | 23 | 1 | 2 |

## Number of F1 and Purebred Cows calving ease - all lactations

| Sire | Dam Breed |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Breed |  | AY | BS | GU | HO | JE | MS |
| AY |  | 109 | 0 | 0 | 73 | 5 | 1 |
| BS |  | 0 | 224 | 4 | 968 | 9 | 3 |
| GU |  | 2 | 0 | 232 | 57 | 4 | 1 |
| HO |  | 147 | 187 | 348 | 85,952 | 241 | 22 |
| JE |  | 3 | 9 | 21 | 1543 | 938 | 2 |
| MS |  | 1 | 1 | 0 | 55 | 1 | 9 |

## Calving Ease Model Effects

**Herd-year-season of calving**
**Linear and quadratic effects for age at first calving **
**Lactation number**
**Breed composition of dam**
**Service sire breed**

## F1 Daughter Calving Ease 

|  |  | First Lactation |  | All Lactations |
| --- | --- | --- | --- | --- |
| Heterosis  |  |    0.04 ± 0.1 |  | — 0.07 ± 0.5 |
| BSxHO |  | — 0.03 ± 0.2 |  | — 0.05 ± 0.1 |
| GUxHO |  | — 0.71 ± 0.9 |  | — 0.45 ± 0.3 |
| HOxBS |  | — 0.05 ± 0.4 |  | — 0.14 ± 0.2 |
| HOxJE |  | — 0.04 ± 0.3 |  | — 0.07 ± 0.1 |
| JExHO |  | — 0.11 ± 0.2 |  | — 0.14 ± 0.1 |
| JE sire |  | — 0.19 ± 0.2 |  | — 0.21 ± 0.1*** |

## Calving Ease Conclusions

**Jersey service sires had lower calving ease scores than other breeds over all lactations.**
**Holstein dams had slightly more difficulty than other breeds and breed crosses.**
**Modeling calving ease is complicated.**
**Only Holsteins are routinely evaluated.**