Sharper focus on nutrition can help get best from grazing

With feed costs set to rise by up to 3p/litre, making more milk from grass will be essential to maintaining profit this coming season.

However, Advanced Nutrition’s Adam Clay says by bringing nutrition management into sharper focus, farmers are more likely to minimise the variables that pose the real challenge.

He outlines five key areas for attention when grazing:

1) Grass dry matter

Grass dry matter is the biggest variable for grazing cows. Dry matter is impossible to manage, but easy to keep in mind. Grass dry matters will affect the level of grass consumption needed to achieve certain energy intakes – for example, the difference between a 16% DM and 22% DM is 27kg fresh weight grass.

While a cow will be able to eat 73kg fresh weight grass a day, she will never be able to physically achieve a daily intake of 100kg fresh weight. So, when spring grass is clearly wet, then accept cows need to get as much grass as they can in a set amount of time.

Solution: Remember, every 1kg DM of grass silage will displace 1kg DM of grazed grass. So when conditions allow, maximise grass intakes, but when it is wet and dry matters drop, cows must make up the loss in DM intake with buffer. For example, maize silage contains low protein and high energy/starch and balances grass very effectively with low substitution rates.

2) Neutral detergent fibre (NDF)

While DM intakes can vary, NDF intakes will remain at a maximum level of 6.8-7.2kg a cow a day depending on cow size. NDF is vital for butterfats and rumen health, and should formulate 35-40% of the diet; a minimum of 22% NDF from forage should help rumen health and minimise the risk of acidosis.

Solution: When grass is high in NDF and you are offering a buffer, you may end up with surplus grass and a flat grazing wedge. Alternatively, when little grazing is available at turnout and you need to extend the grazing round, then high NDF feeds such as soya hulls, moist feeds such as brewers grains or simply grass silage will take the pressure off the grass and build covers while still maintaining NDF intakes.

3) Residuals

Grass should be grazed down to a minimum 1700kg/ha DM, and ideally 1500kg/ha DM in good conditions. Achieving consistently good residuals is critical to maintaining high energy levels throughout the grazing season and therefore maintaining or increasing milk from grass.

Solution: Allocation is key. Good residuals will only be achieved with the correct entry covers of 2800kg/ha DM, or 3,000kg/ha DM in good conditions. Proportionally, as grass height and therefore NDF levels rise, energy decreases. So once the plant has three fully grown leaves, the quality is at its best and any extra growth will result in higher fibre and lower energy density.

4) Supplementary protein

Grazing diets are high in protein, so managing supplement choice is essential for cow health. Excessive protein in the rumen requires energy to use it so over-feeding can eventually leave cows, particularly those in early lactation, in a more severe negative energy balance. It can also result in high ammonia levels, which can damage soft tissue.

Solution: At turnout, reduce concentrate to 16% CP, and as soon as grass becomes a major part of the diet, replace with a 14% CP concentrate. Monitor body condition score change to prevent excessive loss. Monitoring milk fat and protein ratio may also be a good indicator.

5) Magnesium

Supplementary magnesium is essential to avoid grass staggers. High potassium and low magnesium levels in spring grass combine to leave cows low in magnesium. Also, after spring grass is broken down in the rumen, oils coat the fibre and increase the rate it passes through the rumen, thereby leaving insufficient time for the rumen bugs to extract and use the magnesium.

Solution: Introduce mag chloride flakes to the drinking troughs. When you are concerned about water taint, use cal mag or a mineralised lick.

“Milk from grass will come down to achieving consistently high energy levels this spring, which can be achieved through tight management, accurate buffer feeding and good attention to detail,” Mr Clay says.

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