The Government plans to sign the TPP in Auckland next week, although approval by the United States will be delayed by the presidential election later this year.
For dairy, access to new markets was more important than the removal of tariffs.
But the wine, horticulture and fishing industries would soon operate tariff-free in key markets, he said.
In a "Farm to Fridge'' report, Forsyth Barr estimated that once fully phased in, the TPP would cut $262 million from present annual tariffs and provide limited quota access to key dairy markets.
The top-end potential annual benefit for New Zealand was $445 million, the report said.
Equitable access to TPP markets could increase volumes of key products, although some volume safeguards remained, Mr Young said.
All the main agricultural sectors should benefit from the removal of tariffs in the other 11 TPP countries.
At present, New Zealand pays about $322 million in duties on its agri-exports to TPP countries each year (based on the 2012 to 2014 average of $6.7 billion worth of exports).
That is 4.8% of the value of the exports.
Once the TPP was fully phased in, the agri-sector could expect to save 81% of that.
Dairy, meat and horticulture would make the greatest savings.
Fisheries, forestry, horticulture and wine would all have tariffs removed once fully phased in.
Dairy, the biggest contributor, would see 73% of duties removed.
Beef duties remained in place in Japan, in particular, although importantly the tariffs were realigned with Australia post the Australia-Japan free trade agreement, Mr Young said.
Dairy quotas would provide additional access to the United States, Canada, Mexico and Japan.
However, by year 10, total quotas accessible to all TPP exporters would still only account for about 5.6% of New Zealand's current butter production, about 11% of total current cheese production and 4% of total current powders production.
"Access into US, Canada, Mexico and Japan is positive with those markets typically presenting higher value-add opportunities.''
Potential value was estimated at $310 million in year one, growing to $670 million by year 15 - to be shared among TPP exporters, he said.
