Shropshire Star

Be smart with the cows' turnout

For grazing dairy cows, maximising growth rates and pasture qualities is critical, but managing dry matter intake is perhaps the most important, yet difficult, to achieve.

Published
Angus Little, NWF Agriculture

Grass plants have three fully viable leaves, a fourth will grow but the first will die away. Allowing this to happen is a waste and reduces plant establishment.

For those without a plate meter, using the three-leaf method is an accurate method determining the optimum point to graze pasture. Leaving grass too long will reduce a cow’s ability to achieve a low clean grazing residual decreasing pasture qualities.

Intake is king. Turning cows, particularly the high yielders into slightly higher grass cover, can increase grass intake per bite and total grass intake.

‘Turnout’ doesn’t have to mean cows are out all the time. Kennedy et al (2009), showed restricting time at pasture improved grazing efficiency by increasing intake per bite and per minute. This strategy can be used in two ways.

One is spring turnout - restricting access time when cows are grazing, particularly if they haven’t received their buffer pre-turnout.

Limiting pasture access to approximately three hours twice a day ensures efficient pasture intake without impacting too negatively on wet ground. Research suggests access time being split as opposed to one prolonged period at grass, encourages intake per unit of time at grass and milk yield.

The other way is looking at total dry matter intake (DMI) considering cows' grazing behaviour. A typical Friesian/Holstein requires approximately 3-3.5 per cent bodyweight in DMI, Jerseys can be slightly higher. That’s approximately 20kg DMI, with typically 12-14kg forage intake leaving another 6 to 8kg to be achieved in the parlour. This assumes forage intake can be achieved at pasture, which is often not true so 2 to 4kg silage DMI may be required. The question is, when should a buffer be fed?

Habitually, at night cows still fear from predators, but there are also photoperiod effects hence cows remain in the herd reducing grazing and intake to almost zero.

At sunrise, searching and grazing activity increases whereas the evening prior to sunset has the lowest searching, highest intake and grazing activity (adapted from Gregorini et al, 2013). It’s believed that pasture quality increases towards the end of the day, with lower proteins and fibre and higher dry matter, organic matter and water-soluble carbohydrates.

Many factors influence milk constituents, but key points should be remembered while grazing. Milk fats are closely related to rumen health and pH ensuring diets have balanced energy, while maintaining a healthy level of digestible fibre, buffering the rumen reducing a milk fat drop.

Angus Little, NWF Agriculture