There are many possible ways of splitting up dairy cows for health, production or management purposes, but looking at logistics and dietary requirements of each group is paramount before making the change.
Speaking at a meeting held by Mole Valley Farmers at Reaseheath College, Cheshire, Bill Weiss, a professor at Ohio State University, said in most situations the highest priority when grouping cows should be by their parity.
He said: “If a farmer wanted just two diet groups it was better split them into a heifer group and a cow group.”
In a very close second place, fresh cows, defined as being in the first three weeks of lactation, should be grouped separately from later lactation cows, he said. But this situation would call for one small fresh group and one much larger later lactation group, which may cause logistical issues.
Research showed even just separating two-year-olds from the older cows in the herd, with no changes to diet or management, meant they laid down more, ate more and ate more frequently. All factors which contributed towards higher milk production and better rumen and foot health.
Dr Weiss said: “This does not add any cost and even in a grazing situation, heifers which were separated ate more and produced more milk.”
However, the cow most susceptible to infection on-farm was a pre-fresh cow said Dr Weiss, which was closely followed by a fresh cow due to suppression of the immune system in late pregnancy and early lactation.
Therefore, Dr Weiss explained that if the aim of splitting cows was to decrease metabolic conditions post-calving, there must be a pre-fresh group too.
He said: “When implementing a pre-fresh diet, make sure there is adequate housing and facilities for it. If there is not, a diet is not going to work. You cannot fix overcrowding with a good diet.”
Every time a group was added, it demanded more labour for feeding, bedding, milking and more management time.
He said in a pre-fresh group, fill just 80 per cent of the headlocks or cubicles in the building. Build the facility for 120 per cent of the expected number of pre-fresh cows.
The biggest reason to have a pre-fresh group was lowering incidence of ketosis and also hypocalcaemia through the application of a dietary cation-anion diet (DCAD).
DCAD diets which are high in sulphur and chloride should be fed two to three weeks pre-calving he said, to protect against hypocalcaemia. But studies showed this was not a good diet for heifers.
When formulating a diet for pre-fresh cows, Dr Weiss said feeding higher protein diets to them was a waste of money.
He said: “A crude protein diet of 11 per cent would provide enough metabolisable protein for a pre-fresh cow. However, pre-fresh heifers do require more and a diet of about 15 per cent crude protein is sufficient.
“Most farms are not able to split pre-fresh heifers and cows so the compromise is about 13-14 per cent crude protein in the diet.
In terms of trace mineral requirement, meeting the standard values was adequate, but vitamins were different.
“There is good evidence saying pre-fresh cows should be given higher levels of vitamin A and E to improve health of the cow and the calf. The in-utero transfer of vitamin A and E is very poor.
“The reason we see a good calf response to vitamins A and E is that calves are born with almost none in their system, instead they get this from the colostrum. By feeding the cow you enrich colostrum even more,” said Dr Weiss.
Feeding more vitamin E in the pre-fresh diet also reduced post-calving mastitis, metritis and retained placenta. The diet should have been enriched with double the normal levels of vitamin E and 50 per cent more vitamin A, he explained.
Dr Weiss said if farmers were going to opt for having a fresh group it should only be for cows up to three weeks post-calving. Once over this period, the benefits of a fresh group started to diminish.
Fresh cows produced a lot of milk but did not eat much so they could not be given the same diet as later lactation cows. He said they needed to be provided with more nutrients in a smaller amount of feed.
Studies carried out on the intakes of fresh cows showed high protein diets of 19 or 21 per cent caused a 2kg increase in intake per day versus a diet of 16 per cent protein which is a huge increase for a fresh cow.
Dr Weiss said that although it did increase milk production, which was usually not advisable in very early lactation due to the risk of ketosis, they did not have the highest levels of non-esterified fatty acids (NEFA).
In fact, the cows on the low protein diet had the highest risk of ketosis as they produced less milk but they also ate less.