Effectively managing dairy cow body condition throughout the season is fundamental to herd health, maximising reproductive performance and optimising milk solids production.
If we can ensure body condition meets industry targets at key times of a lactation, many health challenges can be avoided or limited, which in turn results in fertility, longevity and ultimately productivity.
Five: the magic number
The optimum Body Condition Score (BCS) target is 5 for mature cows and 5.5 for first and second calvers. Meeting this target makes a considerable difference in reproductive outcomes compared to cows with a lower BCS.
"It's all about having the cows in the right condition at calving to optimise milk production, while ensuring reproduction and animal health are not compromised," Farm Source Programme Lead Tim Johnstone says.
The modern-day dairy cow is predisposed to produce milk at the expense of body reserves during early lactation. If cows are too light in condition at calving it can damage their reproductive performance.
A cow should lose no more than 1 BCS from calving through to mating, ideally less, with the aim to have all cows past the lowest point of energy balance and at a minimum BCS of 4.0 at the planned start of mating. To achieve this you have to proactively make the call on when to dry off individuals or groups of cows, giving them sufficient time to reach optimum BCS for calving and subsequently mating.
"It's easy to over-estimate how much condition you can put on a cow in a short time - I've been guilty of it myself. A well fed-cow can put on half a condition score a month, with padding at either end of the dry period. It takes a couple of weeks to get out of milking mode and at the end of pregnancy, her uterus is so big she can’t eat enough to gain weight. If you dry off a cow at BCS 4, you need three months to bring her back to 5," Tim says.
DairyNZ has a series of videos, information sheets, and tracking tools on its website to help farmers get to grips with how to body condition score.
The importance of optimising BCS
1. Optimal Calving Health: Cows with a BCS of 5 or 5.5 at calving are better equipped to handle the physiological demands of the transition period, reducing the risk of metabolic disorders and promoting overall health.
2. Enhanced Milk Production: Cows entering the lactation cycle with an appropriate BCS are more likely to experience higher milk production. This is crucial for maintaining a profitable and sustainable dairy operation.
3. Reproductive Success: A proper BCS at calving is closely linked to reproductive success. Cows with the right condition are more likely to exhibit estrus, conceive promptly, and have a higher chance of successful pregnancies.
4. Dry Period Nutrition: Allowing cows sufficient time and proper nutrition during the dry period ensures that they can replenish body condition and meet the energy demands of the growing foetus and subsequent lactation.
5. Improved Immune Function: Cows in optimal body condition are more likely to have robust immune function, reducing the susceptibility to diseases and improving overall resilience.
The proof is in the numbers
Investing in the improvement of BCS is a capital process that pays dividends in the future. Cows with a BCS of 5 typically maintain or achieve a similar score in subsequent seasons.
There is a proven link between BCS and reproduction and production. Cows calving one BCS unit lower than target will take eight to 10 days longer to start cycling resulting in later calving next year and produce around 15 kg milksolids less in the following lactation. This adds up if your herd has lower BCS across the board.
Have a plan on how you will achieve body condition targets
There are three effective strategies tomanage BCS mid to late lactation.
1. Supplementary feed. Keep in mind it can be difficult to put condition on cows in late lactation. Extra feed tends to increase milksolids production rather than condition score, particularly with high genetic merit animals.
2. Reduced milking frequency. Cows milked once-a-day in late lactation gain about 0.25 BCS units more in three months than cows milked twice-a-day over the same period. However, cows must be offered the same amount of feed as if milked twice-a-day.
3. Drying off cows. Tim says an effective strategy to achieve calving BCS generally involves a mix of all three, and plans should be tailored for each individual cow, taking into account their condition and expected calving date.
"In New Zealand we’re prone to treating the herd as a herd, rather than individuals. When you get to drying off cows you should be looking more at the individual cows. What’s her body condition score? What's her age? When is her calving date? You might need to dry her off early to get her up to condition,” Tim says.
"Whatever strategy is used, dry cows need time as well more energy to gain BCS. Realistically dry cows only gain half a BCS unit in 30 days. 0.6 can be achieved if she is very well fed with high quality supplement, and do not expect cows to gain BCS in their final month of pregnancy. While all farmers are assessing the condition of their cows every day, it’s human nature for 'normal' to wander, and there is real value in checking skills with DairyNZ's accreditation course, refer to DairyNZ’s how-to guidance material or get an accredited assessor into check yourself against."
Tim recommends farmers download DairyNZ's Dry Off Date Tool that recommends dry off dates based on condition and calving date with specific dates for three groups of cows: three-year olds, mature early calvers and mature late calvers.
For more information about Body Condition Scoring, talk to your Farm Relationship Advisor, or visit www.dairynz.co.nz.