|Good quality forage should always be the basis of any ration
Weather conditions over summer determine to a high degree the quality of silage in winter. Wet weather can lead to low quality silage, in turn a potential cause of Sub Acute Ruminal Acidosis in dairy cows. Managing silage quality therefore is paramount.
By Dr Derek McIlmoyle, AB Vista technical director Great Britain & Ireland
Poor forage quality and in many cases lack of forage has been a major problem on many UK and Irish dairy units this winter. In 2012, the country also saw an unusually large variation in silage quality, which has presented its own problems when formulating diets in order to get cows to reach their expected performance level. In many cases milk yields are down 2-3 litres per cow as producers struggle to feed cows with below average forages.
Wet silages seem to be a common occurrence on many farms as a result of poor weather conditions over the summer. This wetter silage, combined with the problem of low forage stocks, can mean that overall forage intakes are lower than previous years.
Good quality forage should always be the basis of any ration, and when quality and/or quantity of forage dry matter intake is reduced, then cows can struggle to perform. Cows can also have a higher risk of Sub Acute Ruminal Acidosis (SARA), especially if the shortfall in forage energy intake is being met with higher levels of starchy cereals.
Milk yield loss
||Paul Sloan, nutritionist: "A ration done on a computer is no substiture for getting in among the cows."
Studies have shown that SARA can be responsible for a loss in milk yield of up to 3 litres/cow/day. Even if SARA only accounted for a reduction in yield of 1.5 litres/cow/day, at €0.32/l, this would equate to a loss of just over €6,000 for a 100 cow herd over a typical winter feeding period of four months.
Paul Sloan, ruminant nutritionist at Tullyherron Farm Feeds in Northern Ireland, says: “It’s even more important to get the best out of the total ration and in particular producers need to make the best use of their silage.”
He continued, “In many cases grass silages are lower in energy and higher in fibre this year, which places increased importance on the other components in the ration. More emphasis should be placed on using higher quality blends to help make up the shortfall from the forage portion of the ration.”
“It is important to walk through the cows regularly and observe their behaviour at both feeding and resting times, as this can tell you a lot about how the ration is performing. A ration done on a computer is no substitute for getting in among the cows,” he adds.
“Blends need to be correctly balanced with good levels of cereals to drive performance, and they should contain only quality raw materials with no filler type feeds. Getting the right level of energy and starch is important, and maize meal is a key ingredient as it has lower starch degradability to help reduce acid loading in the rumen. Good fibre sources such as soya hulls and sugar beet pulp should also be included to help balance the ration and maintain rumen health.”
Sloan says, “Maintaining rumen health is the key and we have added live yeast to most of our rations this winter to help promote rumen function. Live yeast improves fibre digestion and with the higher levels of fibre in this year’s silage the yeast is an important addition. The live yeast also helps reduce levels of lactic acid in the rumen, therefore helping to reduce the acid loading and maintain a healthier rumen environment. By taking this approach we have also seen significant reductions in laminitis-related feet problems.”
Damaging the rumen wall
Researchers Krause and Oetzel (2006) have shown that when frequent bouts of SARA occur, it can increase the risk of damage to the lining of the rumen wall. As pH drops, the normal balance of the rumen flora is disrupted and gram negative bacteria lyse, releasing endotoxins. As a result of the damaged rumen lining, bacteria and toxins from the rumen can then easily enter the blood stream which can lead to liver damage and an inflammatory response within the animal. These toxins in the blood stream can also increase the risk of laminitis occurring.
Laminitis occurs because the strength of the connective tissue within the hoof has been reduced, allowing the bone to rotate and sink into the corium, which causes swelling of the coronary band and can lead to sole ulceration. Laminitis is linked with SARA because protease enzymes within the connective tissue can be activated by the bacterial toxins in the blood. When this occurs, the proteases degrade the strength of the connective tissue within the hoof, thus causing laminitis. Live yeast can help to reduce the risk of SARA occurring by helping to maintain the rumen pH at a higher level and also reducing the time that the pH spends below 5.8 (Table 1).
A recent study carried out in 2012 at Schothorst Research Centre in the Netherlands showed that including live yeast (Vistacell, AB Vista) in the ration increased 3.5% fat corrected milk (FCM) yield by 0.8 kg/d for all cows, with first lactation heifers producing an extra 2.7 kg/d FCM. The number of cases of mastitis were reduced by 80% and somatic cell counts were also reduced significantly (P<0.05) during weeks four to six for animals fed this live yeast product, indicating a better immune and health status.
In addition to helping stabilise and raise rumen pH, live yeast will scavenge oxygen in the rumen, making the conditions more anaerobic, and certain nutrients are also produced by the yeast which helps to stimulate fibre digestion. Forages this season tend to have higher fibre contents and this improvement in fibre digestion that live yeast delivers is particularly important. This season we have seen more producers switching to live yeast to help improve feed efficiency and extract more performance out of this year’s more fibrous forages.
It is possible to observe more issues with mycotoxins in winter due to higher levels of moulds being present at the time of ensiling. With the wet weather at harvest, it can also be a problem in home produced and stored cereals such as crimped wheat. In situations where we think these toxins may be causing a problem, a wide spectrum mycotoxin binder which protects against the widest range of mycotoxins, including DON, should be considered.
A combination of factors has contributed to 2012 being a challenging one for producers in the UK and Ireland. Poor harvest weather is a major factor and that has had an impact on forage quality. Sloan concluded, “Despite the difficulties, we are seeing some excellent performance on both dairy and beef units in our trading area. However, what is important, is being able to manage what silage is left on each farm and match it to the correct high quality blend to get a ration that performs not only for the cow but also for the farmer in terms of increased milk output.”
References available on request.