By Lorna MacPherson, dairy consultant, SAC Consulting

Results from SAC Consulting’s forage analysis service indicates that on average, dairy first cut silages are drier than last year, with slightly higher protein and similar energy results.

Sugar levels are also slightly higher, with a greater intake potential. Average analyses with minimum and maximum levels are compared to SAC’s 2019 dairy first cut silages in the table below:

Dairy first cut silage results 2020

Nutrient Average Minimum Maximum

Year 2020 2019 2020 2019 2020 2019

Dry matter (g/kg DM) 309 265 198 162 495 390

ME (MJ/kg DM) 11.5 11.5 10.3 10.4 12.3 12.3

Protein (g/kg DM) 137 131 108 99 166 167

D Value (%) 71.7 71.9 64.4 65 77 77

NDF (g/kg DM) 447 467 357 377 545 617

Silage Intake Potential (gDM/kgLW^0.75) 107 99 90 79 125 124

Sugars (g/kg DM) 76 67 35 30 103 92

Ash (g/kg DM) 81 80 66 43 97 98

PAL (Meq/kg DM) 828 902 744 755 1023 1133

pH 4.3 4.1 3.7 3.5 4.8 4.6

The main difference this year is the dry matter – up from 265g/kg DM to 309g/kg DM, reflecting the dry weather conditions in May. Note that averages hide a wide range in quality, and even though silage is only about 50% of the total ration, it can have a big impact on milking performance. A difference in ME of 1MJ/kg DM can affect milk yield by almost 2kg based on a 10kg dry matter intake of silage.

If feeding silages with a high dry matter content (>35%) the ration will likely be on the dry side, especially where moist feeds such distillery by-products, potatoes or fodder beet are not included. The target dry matter for TMR’s should be in the region of 40 to 45% dry matter (and even slightly less for those practicing compact feeding).

Incorporation of dry silages in TMR’s can result in reduced intakes, ration sorting, poorer rumen health and reduced milking performance, leading to financial losses.

By sorting the ration, cows eat finer forage particles and concentrates almost exclusively during the first 12 hours, setting themselves up for acidosis. Latterly, cows are forced to eat more of the longer particles that have been sorted out earlier.

This is why sorting can affect dung consistency and butterfat percentage due to inconsistent feed and conditions in the rumen. If the ration is greater than 45% dry matter, consider adding water to target a dry matter around 40 to 45%.

Silages with a high dry matter will be more susceptible to heating and spoilage (both in the clamp and in the feed trough) and are more likely to contain mycotoxins. If the pH is higher than 4.4, the risk of spoilage is much greater and can occur quickly. Remember mycotoxins can be present despite no visible mould growth.

Whether you are working with very wet or very dry forages this winter, accurate assessment of dry matter intake is important to determine whether there is room for improvement, which in turn may benefit health, production and fertility.

Accurate measurement of feed intake is not common practice on many farms, as this takes into account refusals which are not often weighed. However, monitoring and improving intakes can greatly impact on feed efficiency, reduce waste and increase milk output.

Aim to feed for no more than 3 to 5% refusals for the milking herd and weigh leftovers to accurately assess dry matter intake.

Once intake is known, feed conversion efficiency (FCE) can be calculated from milk yield (kg) divided by dry matter intake (kg), with the target being around 1.5. FCE varies according to lactation stage, and will be highest in early lactation, as milk yield peaks before dry matter intake peaks.

In early lactation, once maintenance requirements are met, every extra 1kg dry matter consumed, will support on average an extra 2kg of milk. An improvement of just 0.1 in FCE can reduce feed costs by approximately 1ppl.

FCE is driven by forage quality, with higher NDF (neutral detergent fibre) silages lowering FCE. To some extent, feed additives such as yeasts, plant extracts and rumen buffers can help improve FCE. Management practices can also play a role.

Consider the following: more regular pushing up of feed, moving from once a day to twice a day feed out, ensuring proper mixing of the TMR and adequate processing of forages. All of these things can help reduce wastage and encourage intakes.

Feed space is also very important, especially for newly calved cows and 1st lactation heifers. They are most susceptible to low feed intake and most negatively affected by it. A minimum 24 inches of feed space is commonly recommended but fresh cows will benefit from more, with 36 inches being optimal.