Richard Dicken, of Broomhurst Way, Muxton, was locked up after pleading guilty a charge of fraud and a charge of theft from his employer Holstein UK.
The 38-year-old blamed a gambling addiction and mental health problems for his actions when he was sentenced at Shrewsbury Crown Court on Monday.
Prosecuting barrister Mr Bernard Linneman said Dicken started working at the breeds and research society in autumn 2016.
"He was employed by them as a financial assistant and was paid a salary of £19,500 which was paid into a bank account directly. It was a significant position of trust.
"His duties involved managing and processing invoices received by the company, uploading them and payment of those on the computer system and arranging for authorisation by a senior financial person for the release of the payments.
"He had access to the material as a result of his job."
Mr Linneman said that from late October 2016, Dicken began to delete the correct information from invoices from clients using a template, then add the bank details of one of his own accounts, but not the account that his salary was paid into.
He said the theft came to light in April 2017 and a total of 19 fraudulent transactions were found totalling £301,027.
"On June 1, 2017, the defendant made a phone call to the police to which they responded by going to his home address and he made some admissions saying he was not in the right frame of mind and he has been funding a gambling habit," Mr Linnenman added.
The court also heard that Dicken had a caution for theft of £5,000 from his parents in 2012 and a conviction for stealing sums from his grandmother.
Miss Debra White, defending, said: "He is remorseful. He blames his actions on his mental health."
Sentencing Dicken, Mr Recorder Gareth Evans QC said: "You are 38 years of age. You have pleaded guilty to a very serious matter. You have stolen more than £300,000 from your employer.
"Holstein UK have stated that you have placed it in a very difficult position and the workforce. You were made an exception to the rule and given a chance, they stated that they have been 'betrayed by one of our own'.
"They gave you an opportunity and you rewarded them by stealing money from them over a sustained period of time. I give you credit for your guilty plea, but it must be prison a for sentence for substantial period."
"This is the third time that you have stolen from people," he added.
For fraud and theft Dicken was jailed for three years on each count to run concurrently. He must serve half of the term before being released on licence.
The court heard that efforts will be made to recoup the cash under the Proceeds of Crime Act.