First off, I know nothing about the jersey cow breed in particular
Feed input is directly related to yield, also how much she is putting out, so if she has one calf then she will produce less milk than if she has 4 (or is milked full time)
If Hillie is giving 25 litres per day and has a 2 month dry period, (no idea how long her dry period is?) then she is milking for 300 days per year, thats 7,500 litres per year!! thats as much as some of our mid-lower yielding fresians who are (currently) grazing on ryegrass and clover leys and being buffer fed a TMR plus cake in the parlour.
The amount of cake we feed is based on litres given above 10, if a cow gives 10 litres per milking (20 litres per day) she gets 1kilo of cake fed in parlour per feed, for every 5 litres per day above that we give an extra 0.5 of a kilo, so a cow giving 25 litres will be given 3 kilos of cake per day, 1.5kilo per feed
The cows are fed 40-50kilo per cow per day of TMR during the winter (no grazing time) when they are grazing they are just buffer fed
During the fist 30 days in milk they tend to loose weight and look a little ribby, however with the cake and TMR we soon get them looking nice, these are not holteins, they are friesians and look like this when in good condition
http://www.cogentuk.com/images/118-kirkby-monica-7-jpgHowever I do know that jerseys are small and will not require the amount of feed as the friesians would
When a cow calves and gets moved to the "fresh" group, she is put onto top rations that the high yielders are on, this is a different blend to the normal ration, it is higher in fats and proteins in order to keep the weight on whilst they are giving a high yield.
If a calving cow is fed lots just after calving her body produces more milk as food is plentifull, so after calving the cow is fed loads of good food and milked as much as she will give wich sets her up for a higher yield rest of her lactation, after 30 days on this ration if her yield is less than 25litres per day she is moved to the low yielders as she wont be able to peak higher.
Last year during an awful TB time on the farm, which gave us a 60day standstill, some heifers calved down the road and we werent able to bring them home for 2 weeks, they only had grazing and 1 calf on each, we didnt take them silage as then they would produce too much milk and lift the risk of mastitis.
These cows when brought home didnt ever produce much in the first lactation, as they didnt need to, they also kept condition on well (too well) as they were only milking for one calf and not being fed a huge amount.
So depending on how far she is in to her lactation, if you milked less and gave her bland-er foods, barley straw, maize silage, high DM hay then she may reduce her yield, or to keep body condition on her as she is producing a large amount of milk, I would give her 3 kilo of cake per day, and buffer her grass with silage or high sugar hay whilst she is being milked, or offer in a rack out at grass, also protein in the form of molasses helps at the rate of 2 kilo (2 litre) per cow per day
If she has been bred for milk production then it may be best to feed her like a dairy cow and utilize the milk, 25 litres is a good amount! or milk her less and make her food blander but dont leave her hungry, straw is good or hay
Hope this helps, not sure what else to suggest
Jess