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

Lack of energy results in body condition loss , health problems and poor fertility .

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

Dr Richard Kirkland , Global Technical Manager for Volac Wilmar Feed Ingredients

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 .