Highly digestible forage fibre is the key

Improving forage fibre digestibility is critical in optimising milk production, according to Woodley Dairy Direction Director, Bill Woodley. One of the keynote speakers at the ‘Meeting the genetics of the modern dairy cow’ seminar, Bill gave an in-depth presentation on the importance of fibre in rumen function and nutrient supply for the modern dairy cow.

Why is fibre digestibility so important for the dairy cow?

The dairy cow (ruminant) has a unique ability to ferment and digest fibre that would be unavailable for a monogastric. “It’s important to consider forage quality, not just in terms of its nutritional value but in terms of its fibre quality and hygiene. Improved forage fibre digestibility has consistently shown to improve DMI and milk production. DMI is more important than increasing the energy density of the diet as it represents the majority of the energy intake. Increasing forage fibre digestibility will lead to less reliance on starch and fats to provide the energy required for milk production.”

Conversely low-quality forage fibre requires more energy to digest. Plus, the diet will require more purchased energy, in the form of grain and fat, to be added to the diet to maintain milk production.
What affects fibre digestibility?

Forage fibre digestibility is highly influenced by maturity at harvest. This will apply to both legumes and grasses – both annual and perennial species. Cutting early will improve fibre digestibility. This doesn’t necessarily apply to corn silage as most of this crop is harvested at maturity. Fibre digestibility has largely been determined by the growing conditions (weather) pre-tassel. After tasselling, the plant is in the reproductive phase and will be converting sugars into starch (grain). There is virtually no impact on fibre digestibility during the reproductive phase.

But recent research has also demonstrated that length-of-cut can have a profound impact on fibre digestibility. Reducing the TLC (theoretical length of cut) to between 12 and 19 mms can improve digestibility. This is quite apparent with low quality forages. Bill commented that “If you know you are going to harvest low digestible fibre silage (too mature), then cut it finer”.

Calf and Heifer Management

Bill also addressed the importance of actively managing nutrition programs for calves and replacement heifers, rather than continuing to implement ‘set and forget’ rearing programs. “The calf is born with a genetic make-up you can’t change, but you can affect the way it expresses those genes,” he says. The objective is to make sure your heifers reach 85 to 90% of their mature body weight and are in optimum body condition at calving. The more the calf grows in the first two months, the more that heifer will produce in the first two months of milking.

“It’s quite amazing but the amount of milk replacer and pellets you feed in those first few weeks has a direct bearing on growth rates and ultimately, milk production. With the right program, you can easily add 24 kg of body weight gain during the first two months alone.”

Bill also discussed the incorporation of a “dry TMR” concept for feeding the post-weaned calf from 2 to 6 months. Bill commented that the dry TMR concept is a game-changer for raising calves. “We have dairy calves now gaining more than 1.5 kgs ADG during this critical time frame”. “This can easily add another 50 kg liveweight to your heifers,” he says.

The dry TMR contains 15% finely chopped straw and 85% calf grain and is approximately 19% protein with low starch.

The goal is to achieve 900 g/day during the first two months and 1.5 kg/day for the next four months. Heifers should be 40% of their mature weight by puberty and 55% by mating. But the key measurement is body weight at calving with the recommendation to be >85% of mature body weight (post-calving).

“The goal is to maximise pre-pubertal weight gain and then to optimise condition during gestation. Pre-pubertal weight gain is associated with increased milk production; post-pubertal weight gain is associated with decreased milk production.

“Greater attention to nutrition can easily add 60-80 kg to your replacement heifers. The more you feed, the more they will gain and the more milk they will produce. Big heifers produce more milk, smaller heifers produce less – it’s as simple as that.”

About the speaker:
Bill Woodley has more than four decade’s experience in dairy nutrition and management after a lengthy career with a major feed supplier in Canada. For the past decade, he has conducted a consultancy for dairy producers focussing on nutrition and management strategies to improve productivity. He is particularly focussed on identifying and addressing the roadblocks that limit production and developing timelines for expected production responses. Bill is a regular contributor to various dairy publications, including Dairy Global. Bill holds a Bachelor of Science (Animal Science) from the University of Guelph, Canada.