Managing acidosis in dairy herds
Consistent and high energy intakes are needed for high levels of production of milk solids by dairy herds. When ruminants are fed a diet high in readily fermentable carbohydrates from grain, byproducts and highly digestible pasture, a condition known as rumen acidosis can occur. Most commonly, acidosis is present as a sub clinical condition causing lost productivity and unhealthy cattle.
Combating the effects of heat stress
Heat stress is emerging as a major issue with a change in climatic conditions and higher temperatures during the summer months. Milk production and income are the major impacts of heat stress. Heat stress may have longer lasting impact on some herds well beyond those hotter months including decreased cow fertility and cow health. Body heat content or ‘heat load’ is actively managed by the cow all the time. The cows heat load will build if metabolic heat produced internally and heat gained from external environment begins to exceed that lost. Therefore heat stress will begin to occur and major impacts will result.
Heat load (metabolic and environmental heat)
Metabolic heat is related to the amount of heat generated internally due to the eating and digesting of feed. Optimum body temperature for dairy cows is between 38.6˚C and 39.3˚C. With heat also absorbed into the cow from external environment it can be difficult for cows to offload heat in the hotter months. The primary mechanism for heat loss in cows is Evaporation. Evaporation is in the form of sweating and breathing: 70% of total evaporative heat loss is due to sweating, 30% is from breathing (moisture losses from the respiratory system).
Impacts on herds
Cows will expect to have an increase usage of 20-30% in maintenance energy to try and keep themselves cool. Dry Matter Intake (DMI) will also decrease by 10-20% when the air temperature reaches 26˚C or above, therefore with less DMI this can result in an average production decrease of 10-25% and up to 40% in extreme circumstances. Not only will litres drop but milk solids will follow with milk protein percentage decreased by 0.2%-0.4%. A few observable signs of excessive heat load may help judge the seriousness of the problem and decide when to take some measures to limit the stress. Signs may include: drooling excessively, grouping to seek shade from herd mates, reduced feed intake, agitation or restlessness, seeking shade, refusing to lie down and increased breathing rate (>60 breaths p/ minute).
Nutritional Strategies for Heat Stress
As daily DMI decreases in heat, the quality and amount of fibre sources fed is an important factor in balancing the rumen. High quality fibre is the best feed source to maintain rumen stability without producing excessive metabolic heat. It will also help to increase nutrient density. High fibre intakes will help cows recover better after excessive heat load. Lifting the amount of high fibre products such as grain/concentrates will help achieve this. Anothermethod to limit the impact of heat stress is to provide the cows with starch as cows require a greater need for glucose in these conditions. It should be provided in a more slowly fermented form, as slow fermentation starch can be broken down in the small intestine thereby producing less heat and reduce the chances of acidosis. The slowest fermenting starch is maize. Speak to Irwin Stockfeeds experienced sales nutritionists for advice on how to achieve a balanced diet.
10 Steps to consider to combat heat stress (reference: 10 Steps easy to implement things to consider; coolcows.com.au)
1. Plant trees on western side of dairy yard
2. Set up a sprinkler system in dairy yard
3. Install a large water trough on the exit side of the dairy
4. Delay afternoon milking until 5 pm during hot season
5. On hot days, wet dairy yard for an hour before cows arrive
6. Sprinkler cows for 30-60 mins while standing in dairy yard during milking on hot days or when cow breathing rate exceeds 60 breaths per minute or THI is above 78
7. In hot weather provide cows with the highest quality pasture available to graze overnight when they are cooler
8. Increase your cows grain/concentrate feeding rate, feed high-quality forage fibre and higher-quality protein sources and increase intakes of potassium, sodium and magnesium
9. On very hot days, if you don’t have a shade shed, bring the herd back to dairy yard around midday and use sprinkler system to cool cows – if possible provide access to high quality hay or silage
10. Mate more heifers to compensate for lower in-calf rates expected in milkers during the hot season to help maintain your desired calving pattern.
Speak to Irwin Stockfeeds experienced sales nutritionists for all your herd needs this summer.
