Youngstock

Calves should be weighing 23% of their mature liveweight now. For a 580kg cow, this is a calf liveweight target of 135kg in June. Remember, the mature liveweight is the summer weight of third, fourth and fifth lactation cows of the same genetics as the calves – it’s not the average of the herd. The objective of youngstock rearing is to get as many as possible to calve down at target weight within the first three weeks of calving and at the lowest cost. Dairy heifer calves born after St Patrick’s Day are facing an uphill battle. Their size and time is against them. Some farmers will keep them in a separate paddock near the yard and feed them waste milk and the first bit of the parlour rinse for the summer. While milk will improve growth rates, the issue I see on many farms that do this is that the quality of the grass these light calves are grazing is poor. By all means feed them milk, but don’t forget that they need excellent-quality grass and a kilo or two of meal too. For the calves that are on target weight, just good-quality grass should suffice to keep them on track for the summer months. Calves should be weighed every six weeks or so and regrouped based on weight. Keeping two groups should mean you will only have one group of heifers next year. Now is the time to start treating in-calf heifers with pour-on treatment for flies to prevent summer mastitis.

Grass tetany

The risk of grass tetany has really reduced with the good weather. Farmers who have been feeding meal as a grass tetany prevention should now start pulling back the meal or take it out altogether, especially where grass is plentiful. Grass tetany is dictated by magnesium uptake. Mineral levels in grass are usually lowest in April and early May when grass is growing fastest. This also coincides with the period when cows are under most stress with bulling activity and peak production so tetany risk is highest then. While grass is still growing fast now, most cows aren’t under as much pressure and are in good shape. That said, there are some other advantages of feeding a bit of meal in terms of getting cows into the parlour and covering for other minerals. The point is, 1kg or less will cover this, not 3kg or 4kg.

Reseeding

Some farmers are asking if it’s too late to start reseeding now. The risk is that there won’t be enough moisture for germination and proper growth. While land is very dry now, chances are there will be enough rain in June for germination and growth. If it remains dry, germination will be much slower and there will be some seedling mortality, but not all will be lost so it’s a chance worth taking. Fields that were reseeded earlier in the year will need to be sprayed for weeds soon. This is the most important spray you can give and is essential for dock control. They will also need to be topped up with nitrogen. Graze reseeds as soon as possible to encourage tillering. This is determined by doing the “pluck test”. Pluck a bit of grass and if the leaf breaks off, but the roots stay in the soil then it is fit to graze.

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