Weigh-up advice over milking strategy

DairyNZ is advising farmers to consider the costs and benefits carefully before deciding to milk once-a-day (OAD) in early lactation.
Recent research undertaken by DairyNZ has challenged views that short periods of OAD milking in early lactation have little effect on milksolids yield while improving cow reproduction.
"OAD milking has become popular in early lactation to allow farmers to get systems in place to manage springers, colostrum cows, calves, animal recording, difficult weather conditions and a shortage of labour during this time," says DairyNZ principal scientist and project leader Dr John Roche.
"These are valid reasons to milk cows OAD in early lactation. What our research has shown is that even short periods (three-six weeks) of OAD milking has significant milk production costs, with no effect on body condition score (BCS) loss, or reproduction."
Two experiments were undertaken during the 2009/10 season. At DairyNZ's Lye Farm, near Hamilton, milking OAD for three weeks immediately post-calving, milking OAD for six weeks immediately post-calving and milking twice-a-day (TAD) throughout were compared.
At the Taranaki Agricultural Research Station cows were feed-restricted for three weeks in early lactation to simulate a flood or severe weather with one herd milked OAD and one TAD.
"This gave us the opportunity to determine the costs and benefits of milking OAD versus TAD and to examine some of the likely scenarios that farmers may face during this time," says John.
"Individual cows milked OAD for three weeks in early lactation produced 15 per cent less milksolids (MS) during that period and 7 per cent less total MS over the full season than cows milked TAD.
"This translates to a MS production decline of 4 per cent over the full season in the situation where a herd is milked OAD for the first three weeks of calving. This equates to about $10,870 annual revenue lost per 100-cow herd (assuming 400kg mature cow MS and $6.50 per kg MS payout).
"Trial cows milked OAD for six weeks after calving produced 12 per cent less MS (on an annual basis) than those milked TAD.
"Milking cows OAD during a feed restriction in early lactation reduced MS production by 50 per cent more than the restriction alone in this trial, indicating that the negative effects of feed restriction and milking OAD are additive.
"There are often claims that gains are made in BCS and reproduction when milking OAD in spring.
"In our trials there was no difference in liveweight or BCS loss, submission rate, either three or six week in-calf rate, or final empty rate between those cows milked OAD or TAD.
"These results, particularly the financial implications, will be thought-provoking for farmers milking or considering milking OAD this spring," he says.
"There are still questions to be answered around the factors that affect full-season results at an individual farm level.
"In these trials we were not able to measure feed intakes or feed conversion efficiency. However, this research has confirmed under New Zealand conditions with New Zealand cows, evidence from previous overseas studies that showed that the longer you put cows onto OAD after calving, the greater the drop in immediate milk production followed by a subsequent carry-over loss."
DairyNZ strategy and investment leader for productivity Dr Bruce Thorrold advises farmers to be cautious.
"While the gains in time are easy to see, the losses in milk production over the season may be significant but not obvious on-farm because there is no comparison available.
"The differences expected from milking OAD for three weeks are less than year-to-year variability, so you can't measure the effects by comparing between seasons with different management.
"If you are going to milk OAD then we advise to minimise the period of OAD and pay close attention to feed management throughout the season.
"This is vital to ensure the effects of OAD on milk production are minimised."
This research is part of the DairyNZ Strategic Lactation Management Research Programme which aims to define optimum milking frequency and nutrition regimes.
To see the full research report or to get further advice on the pros and cons of milking OAD in early lactation visit the DairyNZ website: www.dairynz.co.nz.