The plant now features a new lairage, curved solid walls, baffled gate locks to cut down on noise and uniform colour and lighting throughout. All features have been proved to reduce animal stress, ABP said.
The changes mean it is one of the most efficient and sustainable beef processing operations in Europe, the company claimed.
The remodelled site was opened by Mike Coupe, chief executive of Sainsbury's, a major customer of ABP for 50 years. The plant employs 727 people and receives cattle from over 2,000 farmers mainly from Shropshire and Cheshire in England and from Powys in Wales.
As well as the changes designed to improve animal stress levels, the plant has also introduced Video Imaging Analysis (VIA) for improved carcase grading. The new technology takes a 3D image of every carcase being taken and stored - providing feedback to farmers, designed to help them to improve the yield of future cattle.
Speaking during the opening, Steve Thompson, business unit director for ABP, said: "Today marks a very significant and exciting milestone for ABP Ellesmere and shows genuine investment into the beef supply chain. The completed development now positions Ellesmere at the very forefront of British and European beef production.
"The new facilities will ensure the continued production of quality British beef for years to come under the very highest standards in animal welfare. I would also like to thank our farmers for their continued patience and support during the redevelopment process."
ABP Ellesmere covers an area of 60,000 square metres - the equivalent of 15 football pitches. The site includes an abattoir, a deboning hall and retail packing facilities. Fresh beef products are supplied mainly to the retail trade in the UK. Product is also exported to the foodservice industries in France, Holland, Germany and Italy. ABP Ellesmere is part of the ABP Food Group - the UK's largest processor of beef.
Elsewhere within the group, APB wants to renovate its site at Langport with four new chillers, a dry goods storage facility and a covered area for arriving livestock. In addition, the company is planning a new security office at the main entrance plus new changing rooms for staff, according to plans submitted to South Somerset district council.
Site manager Alastair Lyle said: "These plans are part of a 20-year plan of action for the site. Our priority at the moment is the refrigeration of carcases on the far side of the site; we would move on to the other aspects later."
Earlier this week, parish councillors in Huish Episcopi voted to recommend approval of the plans, but stressed that ABP Foods should "maintain a robust dialogue with its neighbours, addressing their concerns regarding privacy, proximity and access as this proposed development of the site progresses".
Planning officials at South Somerset district council will make a final decision by 7 December.