Bull semen worth $100,000 is part of a haul of allegedly stolen wagyu cattle uncovered by police.

A 34-year-old man from Grafton, in northern NSW, faces 20 charges including cattle theft and obtaining financial advantage after allegedly stealing more than 100 cattle from his employer.

A vet allegedly contacted by the 34-year-old also faces animal cruelty charges for failing to provide treatment to some of his cattle.

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The cattleman was asked by his boss to sell 200 breeding cattle, but instead is accused of arranging to sell 114 of the animals, including 45 valuable fullblood wagyu cows, to himself.

The allegedly deceptive sale led to a discount of almost $100,000 after the man bought the herd through a third-party at a greatly reduced price.

A search warrant connected to the theft allegedly uncovered a liquid nitrogen storage tank containing bull semen stolen from the employer, worth another $100,000.

Embryos for breeding were also part of the alleged haul.

After his Belmore River property was searched, police allegedly told the 34-year-old to seek treatment from a veterinarian for six ill wagyu bulls.

Police say the vet produced false documents saying he had treated the cattle without doing so, with two of the bulls later dying.

The vet has been charged with committing an aggravated act of animal cruelty and failing to provide vet treatment.

This comes after wider allegations of fraud and stolen genetics in Grafton, with search warrants being carried out at multiple properties in March and over 500 cattle mustered and checked.

He was granted bail to appear at Grafton Local Court on August 11.