How to maintain milk production as grass quality declines

Adapting to changing grass quality

Grass can change considerably as the grazing season moves from late summer into autumn. As pasture matures, it generally contains more structural fibre, but digestibility and energy density can decline, while cows may also consume less dry matter.

Recognising these changes early enables farmers to adjust the ration accordingly and continue supporting milk production as the season progresses.

Late-season grass can also vary in composition. Flushes of leafy regrowth, for example, can have a higher oil concentration as grass comes out of the reproductive heading phase. While this fresh regrowth can appear nutritionally promising, its higher oil content can trigger a rumen response similar to that of early-season grazing and contribute to butterfat depression.

Keeping an eye on both grass availability and composition can help farmers respond to these seasonal shifts and make timely adjustments to the ration.

Balancing energy and rumen function

One of those adjustments is buffer feeding. It can help maintain energy intake as the contribution from pasture declines, but how that additional energy is supplied is key to supporting rumen function.

Cereals can provide additional energy, but inclusion levels need to be managed carefully. High-starch feeds ferment rapidly, increasing acid production and lowering rumen pH. Pushing cereal levels too far can actually reduce fibre digestion and increase the risk of subacute acidosis, with potential consequences for both milk yield and milk fat production.

Protecting rumen function needs to remain a priority when adjusting late-season rations. That means looking beyond how much additional energy the buffer ration provides and instead considering where that energy comes from.

Increasing energy without adding to the acid load

Rumen-protected fats provide another way to increase the energy density of late-season rations. Because they’re not fermented in the rumen, they deliver concentrated energy to the small intestine without contributing to rumen acid production.

For farmers, the benefit is being able to increase energy supply while continuing to support normal rumen function. With around 2.5-times the energy density of cereals, protected fats can supply more energy without relying on higher levels of rapidly fermentable starch.

Used as part of a balanced buffer ration, this approach can help maintain fibre digestion and rumen stability while increasing the energy available to support milk production. Research on grazing cows indicates what that can mean over an extended lactation.

Supporting milk production through late-season grazing

At the Tasmanian Institute of Agriculture’s Dairy Research Centre, a trial followed 150 pasture-based dairy cows from 20 to 220 days in milk. Half received the control ration, and the other half offered an additional 250 g/day of Megalac rumen-protected fat.

The milk response was maintained throughout the supplementation period. Cows receiving 250 g/day of Megalac produced up to 2.1 kg of additional milk per day at peak response and were still producing up to 1.5 kg/day of additional milk at 200 days in milk, while maintaining high fertility.

For farmers managing cows at grass, this sustained milk response demonstrates how strategic energy supplementation can support milk production as lactation progresses. When the nutritional contribution from pasture changes later in the season, strategic supplementation can help support milk production while continuing to protect rumen function.

Making the most of late-season grazing

Late-season feeding works best when supplementation responds to what the grass is providing. Monitoring pasture quality and availability can help farmers decide when buffer feeding needs to play a greater role and when additional dietary energy may be needed to support continued production.

As grass quality declines, rumen-protected fats can form part of that buffer-feeding strategy, increasing energy density without adding to the rumen acid load. Combined with good grazing management, this gives farmers a practical way to maintain energy supply, milk production and milk quality while protecting rumen function through to housing.

Planning supplementation around changing grass conditions can help make the most of the grazing season while supporting consistent herd performance as cows transition towards winter rations.

Want to learn more about managing nutrition through late-season grazing? Explore Megalac’s technical resources or speak to your nutritionist about incorporating rumen-protected fats into your buffer-feeding strategy.

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