BALANCING WINTER RATION SUPPLEMENTATION FOR OPTIMAL COW PERFORMANCE
As producers begin to open maize and grass silage clamps, paying close detail to forage quality is essential to ensure the nutritional requirements of dairy herds are met, says Dr Richard Kirkland, ruminant nutritionist for Volac Wilmar Feed Ingredients.
“Balancing a winter ration should begin with silage analysis to fully understand the quality of the basal forage to enable appropriate supplementation with key macronutrients including fibre, starch, sugar, protein and fat,” he says. “The primary target – ensuring energy supply is maximised.”
Delivering adequate energy to support milk production will always be a challenge with modern high-yielding cows and that energy will necessarily come from a range of sources.
“High D-value silages targeted to the highest-yielders will improve energy availability, but when it comes to supplementation we must look for a range of energy sources to give the ration the balance needed,” says Dr Kirkland.
Starchy cereals provide a boost over digestible fibre sources of energy but limits will soon become clear as over-reliance on either of these types of raw material will lead to problems or productivity shortfalls. With wheat and barley, rapid rates of starch fermentation in the rumen generates acid which drives down rumen pH, and with that an increased risk of acidosis. This effect will be acutely evident in the milk cheque with a fall in milk fat percentage, but the knock-on effects of poor rumen function will reduce fibre digestibility – reducing energy delivered from the basal forage, as well as increasing lameness issues. With a slower fermentation rate, maize offers a somewhat ‘safer’ form of starch than the other cereals and has a slightly higher energy density making it a good addition for starch supply.
Digestible fibre sources such as soya hulls, citrus and sugarbeet pulp will help balance the starchy energy sources and aid rumen function and milk fat, though offer less of the rumen ‘tickle’ factor than fibrous forages. With lower energy concentration than the cereals, the greater bulk will limit the potential to deliver those vital megajoules (calories).
“As we’re well aware from our own dietary habits, the number one energy source is fat. With around 2.5-times higher energy concentration per kilo than cereals, fat punches well above its weight, but with the key benefit that it doesn’t generate acid in the rumen to risk acidosis. It’s all about getting more energy in every bite,” explains Dr Kirkland. “As with the other macronutrients, research has defined requirements for optimal milk production and data indicate that dairy cows require 15-20% of their energy supply to be in the form of fat. From a more practical perspective, this means that rations heading toward 6% fat in the dry matter could be required to meet the needs for milk production.”
Using fatty acids to support cow performance
Aside from a concentrated source of megajoules, Dr Kirkland says the response to fat supplements will vary according to the blend of fatty acids making up the fat. The supplement most suitable to an individual farm will depend on factors including requirements for milk contract, stage of lactation and the drive for fertility.
For early lactation cows, the challenge is to minimise body condition score loss and to get back in calf. As a general rule, each one-unit loss in condition will reduce conception rates by 10%. During this period, C18:1 (oleic acid) is a key fatty acid, particularly when targeting those key additional megajoules as it effectively increases the digestibility of total diet fat to provide an additional energy boost and greater feed efficiency.
“Nutrients can only provide energy if they are actually digested and absorbed by the animal. The latest research also demonstrates the beneficial effects of C18:1 on insulin status, increasing partitioning of energy and nutrients to improve body condition,” says Dr Kirkland. “We also see C18:1 directly influencing the development of fertilised eggs and the likelihood of successful pregnancy.”
“However, to realise these beneficial effects, C18:1 must be delivered through the rumen to the small intestine. This can only be achieved by supplementing with rumen-protected forms of the fatty acids which in practical terms is provided by the calcium salt supplements. Data collated using the Megalac product indicates that larger granule size supplements are more effective at avoiding breakdown in the rumen, enabling delivery of the vital C18:1 to the intestine for absorption in its active form.”
Where milk fat is a key target, then supplements with higher levels of C16:0 (palmitic acid) are most appropriate. Recent data demonstrate an increase in fibre digestion with these supplements which will also aid milk fat, but care should be taken in early lactation as these supplements can drive milk production at the expense of body fat, leading to poorer cow condition which we need to avoid.
A multi-purpose fat supplement like Mega-Max with a scientifically proven ratio of around 60% C16:0 and 30% C18:1 is an effective way to meet nutritional needs of the entire herd at different stages of lactation.
“A balanced ration is important to keep the engines running smoothly in modern dairy cows, but remember the primary need is for energy which will always be a challenge to meet,” concludes Dr Kirkland.