Grass growth is on the way, even if it’s slow on some farms. Where ground conditions are dry, growth is more obvious, while on wet lower land, where soil temperatures are low, grass growth is slower. A week of higher temperatures will make a difference at this stage.

Grass silage is still the easiest way to produce winter feed for most farms. The conditions for quality grass silage are determined by soil fertility.

There is an obvious need for lime on many farms to ensure that nitrogen fertilizers can deliver quality grass crops.

There are opportunities to look at machine systems and operation techniques to manage the silage-making costs.

While contractors dominate the silage-making scene, a growing numbers of farmers are considering the option of going alone, which means they can control harvesting dates more effectively.

This will only significantly impact on silage quality when everything else is in place, such as soil fertility and a quality grass sward. Don’t make that decision in isolation of a longer overall farm plan. The investment required is more than the mower and the harvester in many cases.

And follow the rules of good silage making – cut clean swards, wilt if possible and, if not, consider an additive. Harvest the grass in good conditions and consolidate the pit well, followed by sealing it effectively. A job well done will last for more than one season as a silage feed source, so it’s worth making the extra effort.

Additive can boost fertility

Silage inoculants are usually seen as a way to improve silage preservation supplies. However, one product and bacterial strain has been linked to improvements in fertility also. A study in 2012 showed that farmers who treated their silage with Genus ABS Powerstart claimed to have achieved, on average, a 10-day reduction in calving to conception interval, worth €60 (£50) per cow.

Dr Dave Davies of silage additive supplier Silage Solutions and formerly of the Institute of Grassland and Environmental Research (IGER) has carried out an independent review of research literature. He wanted to explain why a silage inoculant additive can affect how quickly cows get back in calf.

He says that the answer lies in the way the silage is fermented and how the forage is utilised in the rumen. Dr Davies explains that Powerstart contains just one strain of bacteria, a strain of the homofermentative bacterium lactobacillus plantarum. This bacterium, he claims, is able to make better use of all the sugars available in grass, which results in a more rapid fermentation with two significant consequences for the nutritional value of the silage.

“The first is that by making use of all the sugars in grass, less of the available sugar is used during the fermentation, which means that there is more sugar in the resultant silage and available to the cow,” he says. “The second is that by accelerating the rate of fermentation the protein in the grass is preserved more effectively with a higher proportion of true protein and fewer free amino acids, something that will not show up on a silage analysis.”

Dr Davies claims that the impact of faster fermentation and better nutrient retention is important when the silage is digested in the rumen. He claims that when Powerstart-treated silage is fed, the high proportion of true protein combined with the higher sugar levels mean the rumen digests the forage more efficiently. In a typical silage with more free amino acids and ammonia combined with less available sugar, there can be an imbalance in the rumen fermentation. Too much nitrogen will be released and there will be a shortage of rumen available energy, he claims.

“The consequence is a large proportion of protein is lost as rumen ammonia which is excreted as urea into the blood and milk. In silage fermented with L plantarum Aber F1, the improved balance of sugars and true protein gives more effective rumen fermentation and results in less surplus ammonia and consequently lower urea levels,” he claims. “If the rumen is producing a lot of ammonia it has to be removed, which uses up energy.”

Dr Davies believes that if less energy is available from the diet, the consequence in early lactation is that cows will be in extended negative energy balance and will lose more condition over a longer period of time, which is well understood to have a negative effect on fertility.

Dr Davies explains why higher blood urea levels reduce fertility in three ways: “Firstly, cows with high urea levels have longer intervals between heat periods which mean you have fewer opportunities to breed cows.”

Secondly, high urea and ammonia levels have been shown to hamper the development of the eggs in the ovary, leading to poorer quality eggs, which reduces the chance of fertilisation. Finally, high blood urea levels alter the environment in the uterus and reduce progesterone levels which mean cows are less able to maintain a pregnancy.

He claims that silage fermented using L. plantarum Aber F1 has a direct benefit in reducing the reproductive problems associated with high blood urea. Dr Davies claims that it also reduces the energy required to deal with waste urea, leaving more energy for the cow, for production and to reduce negative energy balance.