Effective and accurate feeding critical to maintain summer fertility

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Length: 950 words; 3-4 minutes

Getting summer buffer feeding right is even more critical for those early lactation cows needing to get in calf before being housed for the winter, explains KW’s Charlotte Ward.

Maintaining yields and fertility through the second half of summer is a challenge faced by many herds. With potential nutrient supply from grazing dropping away, periods of heat stress still a threat and cows increasingly reliant on buffer feed intakes, close attention to detail is essential.

“July and August calvers are notoriously difficult to get back into calf,” claims KW ruminant technical manager Charlotte Ward. “Grass quality is declining – especially in low rainfall years – and shortening day length means potential grass intake is also falling.

“By the time mid-September arrives, grazed grass will support little more than maintenance plus 5-6 litres/cow, yet the nutrient demands of those summer calvers are often still climbing. Unless those summer calvers are exceptionally well fed right through the first 100 days of lactation, fertility is going to suffer.”

High financial cost

In one study, despite similar or higher submission rates, significantly lower pregnancy rates were recorded for summer calvers (55–70%) than for those calving in winter (85–92%). And the financial implications are significant – published figures suggest that each additional day beyond the target 365 day calving index (CI) costs around £2.50/cow.

“It means that a CI that’s even 12 days higher for summer calvers is costing the equivalent of 0.3ppl*. Those 12 days would also extend the length of the lactation by around 3%, cutting annual output by around 300 litres, worth another £78 or 0.8ppl*.

“Despite poor fertility being a huge cost for the dairy sector as a whole, few calculate the full implications,” Ms Ward continues. “As milk yields have steadily risen and the pressure on cows, staff and infrastructure has increased, there’s little doubt that herd fertility has suffered.

“In fact, some estimates put the total cost for a typical 200-cow herd as high as £60–70,000/year, which is 3.0–3.5ppl*!”

Better buffer feeding

Improved summer fertility levels can play an important role in reducing this loss, and the key, according to Ms Ward, is effective, high quality buffer feeding. As the weather and day length deteriorate, nutrient supply from buffer feeds has to be increased, not only to make up for the overall downward trend in grass nutrient supply, but also to provide a margin to cover day-to-day changes in grazing conditions and grass feed quality.

“Grazed grass is probably the most variable feed we offer to cows, both in terms of nutrient content and intake potential, and the weather has a major impact on both,” she states. “Grass samples tested for a recent Trouw GrassWatch report, for example, showed sugar levels as low as 4.3% and as high as 12.8%, with similar variation in crude protein (10–30%), dry matter (15-30%) and energy (10.7–12.6MJ ME/kg DM).

“Measuring and analysing what’s fed is therefore essential, with buffer and concentrate feeding adjusted daily to match changes in grass quality and intake.”

Maximising energy intakes should be the first priority, with buffer rations for summer calvers typically requiring an energy density of at least 11.7-12.0 MJ ME/kg DM. Achieving this without overloading the rumen and inducing SARA (sub-acute ruminal acidosis) is critical.

“…include moist and liquid feeds to both raise energy levels and add palatability.”

“Encouraging the necessary high intakes of the buffer ration is also important, so use high quality mixed forages as the base, and include moist and liquid feeds to both raise energy levels and add palatability,” advises Ms Ward.

“In addition, feeds like Traffordgold wheat-gluten moist feed, brewers’ grains or draff will help create a good ration structure with plenty of openness, whilst liquid feeds such as Molale minimise sorting by binding ration ingredients together. This improves consistency of nutrient intake, helps support rumen function – improving energy supply to the cow – and reduces risk of SARA.”

Balancing nutrient supply

Although grass fibre levels will be increasing, additional structural and digestible fibre will still be needed, both to balance the starch required to support early lactation yields and provide sufficient milk fat precursors. According to Ms Ward, good options for digestible fibre include soya hulls and sugar beet feed.

SodaWheat image
SodaWheat is a more rumen-friendly source of starch energy than rolled cereals.

“Aim for an overall fibre (NDF) level of around 34-38% of the dry matter, with other energy feeds chosen to create a balanced release of energy in the rumen,” she adds. “Use low acidosis risk feeds like Soda Wheat or a confectionery blend (SugaRich Dairy) to supply starch, a low protein liquid feed (Molale) for sugars, and add Goldenflake protected fat if additional energy is needed above that supplied by the rumen.

“The priority for protein is to meet cow requirements without oversupplying the rumen degradable protein (RDP) that’s so prevalent in grass. Excess RDP can negatively affect fertility, so focus on feeds high in rumen-bypass protein (digestible undegraded protein, DUP), such as NovaPro heat-treated rapeseed expeller, which is both better value than soyabean meal and has a higher DUP:RDP ratio.”

Higher intakes can also be encouraged by offering fresh feed after each milking, and potentially housing cows during the day, particularly when temperatures rise and heat stress threatens to disrupt feeding. Grazing during the night, when conditions are cooler, as well as prioritising the best grazing for those cows in early lactation, can help reduce the pressure on buffer feeds.

“There’s a lot to get right if you want to fully support these cows through the summer, particularly if you also want to make the most of low cost grazed grass,” Ms Ward concludes. “If you do get it right, however, the benefits, both in terms of summer yields and fertility, and the foundation you set for winter milk production, will more than offset the additional investment in extra feeds.”

* Based on annual yield average of 10,000 litres/cow.

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