Gain the Benefits from Efficient Grazing
William McCulloch, CAFRE Dairy Development Adviser, Coleraine
Poor weather over the past two summers has made many producers question the benefit of grazing cows. Common remarks include:
- Calving pattern has suffered badly over the past two years. I have more late spring calvers than normal. I have always found it hard to get cows back in calf at turn-out, so calving spread will only get worse.
- A lot of these late calvers are giving 35-45 litres. I couldn’t maintain these yields at grass. Wet grass is a variable feed while at least I know what the cows are eating when they are housed.
It must be remembered that in Northern Ireland, high quality forages underpin the profitability of ALL milk production systems. Whether you run a total confinement system, graze by day and house at night or graze full-time, achieving high intakes of quality forage are essential to minimise feed costs. On many farms the stocks of silage still to be eaten are of low/medium quality and cow performance is being limited despite feeding high levels of concentrates.
Poor/medium quality silage can only support maintenance and four to eight litres of milk production per day. Spring grass has the potential to support maintenance + 25 litres per day. For your business going to grass could mean increasing milk yield and protein level while cutting back concentrate feed level by up to 8-10KGs. Grazing high quality grass this spring must be given priority.
Maintaining herd fertility and performance on grass
A drop in herd fertility at turn-out is related to the sudden nutritional change experienced by the cow. To reduce the effect the transition from winter feeding to grazing should be carried out gradually. Start by turning cows out for two to three hours and build up to a half day over seven to ten days. Allow winter and summer concentrates to mix in the storage bin if possible.
Research evidence suggests that excess protein intake in early pregnancy can cause embryo loss. Spring grass has a crude protein (CP) content of 19-22 percent. As the target CP content in a cow’s total diet is 18 percent the CP content of the summer concentrate should be reduced to 16-18 percent as fed depending on milk yield and levels of meal and buffer feeding.
If there is a high number (30 +) of fresh calvers yielding over 35 litres, and handling facilities allow, there could be a case for grazing them by day and housing at night if a high quality silage is available. In variable grazing conditions this gives more control over intakes, benefitting herd fertility and cow performance. The problem with housing the whole herd would be the extra expense of feeding silage and meal to stale, late lactation cows which are already safely back in calf and capable of obtaining sufficient feed from full-time grazing.
For herds using AI, heat detection is normally less effective after turn-out as cows are usually only seen at milking time. Ideally they should be observed with the best time being in the evening between 8 and 10 pm. Heat detection aids such as tail-painting and kamars can prove very useful.
Under ideal grazing conditions in late April/May, grass can support 25 litres of milk. For production above this level, concentrate have to be fed:
- 3 KGs for 30 litres
- 6 KGs for 35 litres
- 9KGs for 40 litres
Between the 1st April and 1st May grass growth normally increases rapidly, from approximately 15 to almost 100 KG dry matter per hectare per day. It is this surge in early season growth which often leaves cows struggling through heavy covers during May. If you delay turn-out until there is an ‘ideal’ grass cover on the first field to be grazed you are going to be grazing very heavy covers by the end of the first cycle. Cows will be unable to graze out these swards cleanly - this will reduce grass quality and cow performance for the rest of the grazing season.
For most of the grazing season the ‘ideal’ grazing cover is 3000-3300KGs dry matter/ha (grass height 6”). At the start of the season, however, you must graze swards with a cover of 2500-2700KGs DM/ha (grass height 4”) to ensure you can complete the first cycle before covers are too heavy. Turning cows out to graze at the correct time is critical to controlling grass growth and maintaining high grass quality throughout the season.
Grazing in wet weather
Be flexible and graze the dry fields - you don’t have to follow a set rotation. Hoof marks are not ‘poaching’ and grass swards will recover very quickly in May from limited damage. Remove some permanent fencing and provide several entrances to fields. Use a back fence and limited grazing times (two to three hours) to reduce sward damage if the wet spell lasts for several days.
Grazing – Management priorities for May
- Turn cows unto swards with a cover of 3300-3500 KG DM/ha (15cms tall) and graze down to 1600-1800 KG DM/ha (6-7 cms tall).
- Walk grazing twice per week for early identification of a grass surplus.
- Use the AgriSearch Grasscheck grass growth figures in agricultural press or on the internet on your farm. If your cows are grazing swards with covers over 4000 KGs DM/ha, the sward to graze in 10 days time already has a cover of 3000 KGs DM/ha. and Grasscheck is predicting growth rates of 80-90 KGs DM/day grazing will get further ahead of the herd. Cut surplus grass immediately for silage.
- Towards the end of the month start topping swards if required.
Dairy farmers need to regain their confidence in grass. It is a complete feed for producing up to 25 litres if well managed. In the current economic climate it will certainly pay you to use grass efficiently and effectively this May.
Dairy cows grazing a target cover of 2700KG DM in May
