¿A partir de cuando, o de que edad tiene un perro que montar una hembra?

No al abandono... no al maltrato... y piensas criar con tu perro?Hazle un favor a ese animal, y cástralo!Y hazle un favor al mundo, y NO cries con él.

White BoxersBoxers with white markings covering more than one-third of their coat - conventionally called "white" Boxers - are neither albino nor rare; approximately 20–25% of all Boxers born are white.[5] Genetically, these dogs are either fawn or brindle, with excessive white markings overlying the base coat color. Like fair-skinned humans, white Boxers have a higher risk of sunburn and associated skin cancers than colored Boxers. The extreme piebald gene, which is responsible for white markings in Boxers, is linked to congenital sensorineural deafness in dogs. It is estimated that about 18% of white Boxers are deaf in one or both ears,[6] though Bóxer rescue organizations see about double that number.[7][8] In the past, breeders often euthanized white puppies at birth; today, most breeders place white puppies in pet homes with spay/neuter agreements. White Boxers are disqualified from conformation showing by the breed standard, and are prohibited from breeding by every national Bóxer club in the world. They can compete in non-conformation events such as obedience and agility, and like their colored counterparts do quite well as service and therapy dogs.

http://en.wikipedia.org/wiki/Boxer_%28dog%29Copio de la Wiki.

White BoxersBoxers with white markings covering more than one-third of their coat - conventionally called "white" Boxers - are neither albino nor rare; approximately 20–25% of all Boxers born are white.[5] Genetically, these dogs are either fawn or brindle, with excessive white markings overlying the base coat color. Like fair-skinned humans, white Boxers have a higher risk of sunburn and associated skin cancers than colored Boxers. The extreme piebald gene, which is responsible for white markings in Boxers, is linked to congenital sensorineural deafness in dogs. It is estimated that about 18% of white Boxers are deaf in one or both ears,[6] though Bóxer rescue organizations see about double that number.[7][8] In the past, breeders often euthanized white puppies at birth; today, most breeders place white puppies in pet homes with spay/neuter agreements. White Boxers are disqualified from conformation showing by the breed standard, and are prohibited from breeding by every national Bóxer club in the world. They can compete in non-conformation events such as obedience and agility, and like their colored counterparts do quite well as service and therapy dogs.

Traduzco lo más importante.Los Bóxer blancos tienen mayor riesgo de quemaduras solares, y tipos de cancer de piel. El gen responsable del color blanco está ligado a la sordera congénita.Se estima que, aproximadamente, el 18% de los Bóxer blancos son sordos de uno o ambos oídos.Actualmente, la mayoría de los criadores colocan a sus cachorros blancos en hogares, con contratos de castración.Los Bóxer blancos no pueden exponerse, y su cría está prohibida por todos los clubs de Bóxer del mundo. Pueden participar en obediencia y agility.

Pues yo pienso que la cria hay que dejarla para personas que saben,No estoy de acuerdo con criar con perros que no tienen pedegree, pues no se conocen sus ancestros.Un perro sin pedegree es un mestizo.

Un Bóxer blanco puede tener pedigree. Pero ello no quiere decir que se deba criar. Si yo tengo un Golden Retriever  con pedigree, que desarrolla displasia de cadera...Es evidente que, por mucho pedigree que tenga, no es un perro apto para la cría.

En mi opinión, a partir de los 2 años de edad, es una buena edad para empezar a montar, que ya es una edad de perro adulto...Saludos