Summer Feeding – Part Two – Pasture Digestibility

December 2016

In Part One we noted heat stress is not only an issue for cows; it also throws up challenges for pastures. Decreases in forage digestibility becomes an increasing challenge to maintaining dry matter intake (DMI) as we push into the summer months.

To put it simply, as the digestibility of neutral detergent fibre (NDF) in forages decreases, the feed takes longer to be processed by the rumen bugs before it is moved along the digestive tract and our cow is ready to consume her next meal. It is often explained in terms of booking people into a hotel room - you can’t check the next group in until the previous group has checked out.

Why should I keep feeding into summer?

By feeding into summer, we can slow post peak decline and potentially extend production.  The reasons for providing a nutrient-balanced, pelletised meal to support summer pasture are best explained through an example.

Let’s say a cow is consuming 15kg DM of forage daily and due to the decreased digestibility of the NDF, that’s her maximum daily intake.

If we were to add 3kg of pelletised dairy meal to daily ration, she would likely make a small adjustment to her grazing intake. Now we anticipate that she will consume 14kg DM of forage plus 3kg of pelletised dairy meal. So now she’s consuming 17kg DM daily. Her total nutrient intake (particularly energy and protein) will increase and she’s now able to produce an increased level of milk solids.

So, we can manipulate feed inputs to maintain productivity and negate the effects of post peak decline.

What does this do to my margin of return?

Remembering the basic requirements for energy for a 500kg liveweight cow:

Maintenance = 60MJ
Activity/environment = 24MJ
Milk = 5.9MJ per litre (5.1% milk fat and 3.9% milk protein)

PASTURE ONLY SCENARIO

15kg of summer pasture intake at 11MJ/kg DM gives her 165MJ energy intake. We have used 84 of these available MJ for maintenance and activity, leaving 81MJ for production, or around 13.7 litres of milk production.

Compare

PASTURE AND TOPCOW® SCENARIO

14kg DM pasture intake plus 3kg DM of TopCow Seasonal 16 at 12.2MJ per kg DM, we now have a total energy intake of 192MJ daily. We still use 84MJ for maintenance and activity, leaving 108MJ of energy or around 18.3 litres of milk production.

HOW MUCH EXTRA CAN I MAKE PER COW

At 9% milk solids, that equates to around 420 grams of additional milk solids, or $2.52 per cow daily at the current forecast payout of $6.00 per kg MS. You would have spent $1.65 per cow daily on the meal.


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