Fonterra is still struggling to provide calf milk powder and calf rearers are desperate, says a rural animal feed store.
Elizabeth Howarth - the owner of Bunnythorpe Feeds near Fielding - was told by Fonterra two weeks ago that the shortage would last a few weeks and they were making more powder.
The co-operative said the shortage of its Ancalf powder was due to retail sales being unusually high this season - at nearly double those of last year.
Farmlands said in a statement that the issue was more serious than first forecast and the lack of milk powder could last another month.
Mrs Howarth said this was not good enough.
"Fonterra say they are back in production but supply is still completely strangulated, all they are doing is supplying back orders and small stores such as me will not be able to order any Ancalf until November."
The season was finishing by then, so it was a bit of a waste of time, said Mrs Howarth.
"They [calf rearers] are absolutely desperate. Some of them are resorting to using Anlamb, which in my view is absolutely not advisable - Amlamb is a different formulation and potentially could cause scours."
Mrs Howarth said she had lost substantial business because of Fonterra's calf milk powder shortage.
"I usually sell a tonne and a half of Ancalf, and at the beginning of the season I sold six bags and then that was it.
"To go from supply to zero supply within the space of three weeks - they've got something very wrong."
Fonterra said in a statement that it had made food-grade whole milk powder available in Farm Source as a calf milk replacer.
The co-operative was encouraging farmers to use milk from the vat to feed calves.