Used for plants and animals, including pets. 雑種の犬 is a common way to say 'mixed-breed dog'. Can sound slightly informal or colloquial when applied to dogs, but is neutral in biological contexts.
うちの犬は雑種です。
Our dog is a mixed breed.
この植物は雑種で、病気に強い。
This plant is a hybrid and resistant to disease.
雑種 refers to a mixed-breed animal or plant, whereas 混血 is used specifically for people of mixed parentage and would sound odd or derogatory applied to a human.
mixed-breed dog; mongrel
F1 hybrid; first filial generation hybrid
interspecific hybrid
heterosis; hybrid vigor
hybrid cell
Compound of 雑 (ざつ, 'miscellaneous, mixed') and 種 (しゅ, 'species, breed'). The reading ざっしゅ results from assimilation of つ to っ before し.