With variation in where the rain falls, comes variation in pasture cover.
And so it follows with cow condition. At the beginning of autumn there was a wide range in cow condition, both between farms and within herds.
Below I cover off what you should be thinking about to ensure cow condition is protected through autumn and winter.
Low Cow Condition
Cow condition and feed planning are two areas requiring careful monitoring to ensure the season’s milk production and reproduction is not dictated by climate.
As lactation goes on during the season, it becomes clear who the high producers are within a herd.
High performance cows tend to keep milking despite limited levels of feed, and lose weight in the process.
Meanwhile, other cows (often lower-PW cows) will begin to partition energy toward BCS gain, getting fat in the process.
If the situation is not managed well, the herd average BCS may appear okay, but the range of cows can be 3.0 to 6.0 by late autumn.
To optimise opportunity for profit, DairyNZ research re-iterates industry targets (at calving) of 5.0 body condition score (BCS) for mixed age (MA) cows, and 5.5 BCS for first- and second-calvers.
These are not merely ‘nice targets to achieve’.
They should be the aim of every farmer at calving – because condition will directly affect milk production and reproduction potential.
DairyNZ’s research shows that the net gain in milk production – through calving cows at 5.0 BCS rather than 4.5 BCS – is 7.5kgs of milksolids.
A separate (DairyNZ) study also shows that cows calving at BCS 4.0, compared to BCS 5.0, results in a seven percent lower chance of cycling at planned start of mating (PSM), and will take about nine days longer to begin cycling.
Cows that have not cycled at PSM typically have:
a 16 percent lower six-week in-calf rate, and;
a six percent higher empty rate.
So what is the best way to manage your herd?
If you’re not already doing so, start body condition scoring your herd to get a realistic understanding of condition – as opposed to the mind-set that ‘they’re okay apart from the odd light one’.
Aim to do at least 70 cows to get a good cross-section of the herd.
Once you have worked out what percentage of your herd are in the ‘4.0 BCS or lower’ category, decide what management changes you can make to hit BCS targets by the planned start of calving (PSC).
So what are the best options for managing BCS in the dry period?
Quantify what supplements are needed for late winter and spring.
Do a feed budget to project if your annual pasture cover (APC) will be at target at the PSC and will track okay through spring to balance date.
Build into the feed budget the required amount of feed to lift the BCS to have the entire herd at 5.0 for MA cows and 5.5 for R2s and R3s.
You cannot expect any BCS gain in the final three weeks of gestation. Also, realistically you cannot expect more than half a BCS gain in 30 days, unless you are using some form of a high quality supplement.
The types of feed can have a major influence on whether you can gain more than half a BCS in 30 days. To gain 1 BCS, a Friesian cow of 500 kgs will need to consume either 200 kgs of dry matter of autumn pasture, 160 kgs of grass or maize silage, or 125 kgs of PKE above her maintenance needs.
So in (early winter),
a Friesian cow calving (in mid-to-late winter), t hat is 4.5 BCS, is going to need about 9.5 kgs offered of pasture dry matter (DM) for maintenance, and will need about 5 kgs of PKE offered per day to reach the 5.0 BCS target three weeks out from calving.
On crops, the same cow will need to consume 210 kgs of DM of kale, 180 of swedes and 155 of Fodder Beet above maintenance. This explains why after allowing for feed wastage, 14 kgs DM offered of feed can be needed to gain 1 BCS over 60 days on winter crops.
This highlights the importance of drying cows off in the autumn based on calving date and BCS in a timely way so that you are not chasing BCS when time is short.
A cow calving on 1 October has a lot more time to lift from a 4.0 BCS, than say, a cow calving on the 1 August (she can therefore be fed differently).
By being proactive (in not letting BCS slip) and by altering management now, you should help provide the farm with options for days in milk at a lower cost structure.
- By Darren Sutton, FarmWise consultant, Waikato