Lush, green grass – a bit of ‘Dr Green’ as my farming forefathers would have called it. However, this poses a major health problem for cattle when they are turned out on rye/clover pastures that contain little fibre but lots of sugar and protein.
Unless high fibre is provided alongside lush pasture (and grazing animals will seek this out to balance their gut function), this high octane combination in grass can cause severe pain and distress to cattle. Ruminants have evolved to utilise tough fibrous forage – and this has become essential to the correct function of their multi-chambered stomach.
This is utilised by certain bacteria in the rumen that create unfavourable conditions that reduce efficiency of digestion, such as acid and high levels of methane gas. During spring growth, levels of protein in these types of pasture can easily exceed 30% on a dry matter basis, or even higher. Soluble sugars are produced in excess by the high rate of photosynthesis in rapid plant growth. Ruminants cannot use more than 16% protein in their total daily intake, and any excess affects the control of gas evolution from fermentation.
Bloat is a condition whereby gas produced from rumen fermentation becomes trapped and fails to coalesce to allow safe eructation (burping) – an essential part of rumen function to prevent build up and distension. High sugar consumption from lush pasture ‘feeds’ certain methane-producing bacteria, and subsequently increases the volume of gas in the rumen. Under these conditions, foamy bloat occurs, where gas bubbles are held in the rumen under a layer of soluble proteins. This causes major distension of the rumen, which is very painful for the animal. As an analogy, when brewing, soluble proteins and other compounds as a foamy scum can rise to the surface, effectively making a viscous ‘blanket’ which holds down the rest of the liquid and the gas, until it erupts violently.
Other feeds used alongside fresh pasture can ameliorate bloat conditions. Chaff or long chopped forage can physically burst the protein layer, releasing the gas. Feedstuffs, such as ground grain or fibre, can help disrupt bubble formation. The fine particle size of milled feedstuffs can break the film of the bubbles. Whole grain feeding does not have the same benefits as milled cereals, and, indeed, there is a phenomenon called ‘feed-lot bloat’ where high levels of starch from the grain promote acid conditions and fast gas production that the animal then struggles to release. So, if farmers are feeding whole grain, care needs to be taken to balance the starch with continuous intake of long, structural fibre. Added oil in the diet will reduce the surface tension of the film holding the bubbles in place, releasing the gas so it can be harmlessly eructated. Indeed, tubed infusion of oil into the rumen is a treatment for clinical bloat.
So, suitable dietary intervention can help avoid bloat in calves. Maintaining access to long, high fibre forage as well as a balanced milled feed to ensure rumen development and correct functioning. Where lush pasture is a hazard, putting out bales of hay or straw allow the animals to ‘self-medicate’ by fibre intake (which they normally will do voluntarily), which reduces any symptoms of bloat.
Talk to your local Reid’s dairy specialist today about the benefits of our mash and the products we can offer to suit your requirements on 1300 REID FEED or enquire here >
Author
Dr Lucy Waldron
Head of Nutrition and Technical Services
