diff --git a/resources/icarReproEmbryoResource.json b/resources/icarReproEmbryoResource.json
index 332c473..e1375da 100644
--- a/resources/icarReproEmbryoResource.json
+++ b/resources/icarReproEmbryoResource.json
@@ -45,8 +45,12 @@
         "sireURI": {
           "type": "string",
           "description": "URI to an AnimalCoreResource for the sire."
+        },
+        "sirePrimaryBreed": {
+          "$ref": "../types/icarBreedIdentifierType.json",
+          "description": "ICAR Breed code for the sire. The usage of this property is not reasonable if more than one sire is provided."
         }
       }
     }
   ]
-}
\ No newline at end of file
+}
diff --git a/resources/icarReproInseminationEventResource.json b/resources/icarReproInseminationEventResource.json
index 625d757..405d1e0 100644
--- a/resources/icarReproInseminationEventResource.json
+++ b/resources/icarReproInseminationEventResource.json
@@ -34,6 +34,10 @@
           "type": "string",
           "description": "URI to an AnimalCoreResource for the sire."
         },
+        "sirePrimaryBreed": {
+          "$ref": "../types/icarBreedIdentifierType.json",
+          "description": "ICAR Breed code for the sire. The usage of this property is not reasonable if more than one sire is provided."
+        },
         "straw": {
           "$ref": "../resources/icarReproSemenStrawResource.json",
           "description": "Details of the straw, which may also include sire details."
@@ -61,4 +65,4 @@
       }
     }
   ]
-}
\ No newline at end of file
+}
diff --git a/resources/icarReproSemenStrawResource.json b/resources/icarReproSemenStrawResource.json
index 15d1b4f..1e11c56 100644
--- a/resources/icarReproSemenStrawResource.json
+++ b/resources/icarReproSemenStrawResource.json
@@ -39,6 +39,10 @@
           "type": "string",
           "description": "URI to an AnimalCoreResource for the sire."
         },
+        "sirePrimaryBreed": {
+          "$ref": "../types/icarBreedIdentifierType.json",
+          "description": "ICAR Breed code for the sire. The usage of this property is not reasonable if more than one sire is provided."
+        },
         "preservationType": {
           "$ref": "../enums/icarReproSemenPreservationType.json",
           "description": "The method of preservation of the semen (liquid, frozen)."
@@ -58,4 +62,4 @@
       }
     }
   ]
-}
\ No newline at end of file
+}