February-born calves are now approaching five months of age. The target liveweight for most February-born heifers is 147kg on 1 July if mature liveweight is 550kg, or to be 27% of their mature liveweight. For these heifers to be at 330kg on 1 May next, they will need to have an average daily liveweight gain of 0.61kg/day between now and then.

But what of heifers that were born later or did not thrive as well up to now? Calves weighing 120kg now need to do 0.7kg daily liveweight gain to be at 330kg on 1 May. Why 1 May? This is the weight at mating and it is the most important weight target as it determines conception rates and ultimately calving date next season, and seasons to come.

So there is a difference of about 0.1kg/day of daily liveweight gain (DLWG) to be achieved between the calves that are on target and those that are behind. The first thing to work out is how difficult it is to achieve the standard DLWG of 0.61kg/day. Keep in mind that the 10-month period between now and 1 May includes the winter period where DLWG drops to around 0.4kg/day to 0.5kg/day, even with 1kg to 2kg of meal in the diet.

If we presume a three-month winter, this means that heifer calves need to achieve 0.68kg DLWG for the seven grazing months between now and mating. This shouldn’t be too difficult to achieve with reasonable grassland management and parasite control.

Youngstock that are 30kg behind target weight now will need to achieve 0.76kg DLWG at grass, presuming they don’t do any better than 0.45kg/day over the winter. It should be possible to achieve this average DLWG on grass only, but quality needs to be excellent and they must get plenty of it.

It is very doable to achieve a DLWG of over 0.8kg or 0.9kg from grass only during the summer and early spring. However, liveweight gain will decrease in autumn as grass quality deteriorates so maximising performance now is important.

Grass

Calves that are light now should be kept in small groups and grazed ahead of other stock, so they get access to the best grass without overly affecting the quality of the grass for the animals cleaning up behind them. Heifers should be weighed every six weeks and resorted depending on target weight.

Calves usually eat around 3% of their bodyweight daily, so they are currently eating around 4.5kg of dry matter per day. Feeding 1kg of meal per head per day means 20% of their diet is supplement, equivalent to feeding 3.6kg of meal to milking cows. The questions are whether this meal is necessary and if farmers are getting value for money from feeding it?

At €300/t, every 1kg of meal costs 30c. Over the next two months, this will add €18 to the cost of rearing replacements. If calves are on target weight and grass quantity and quality is reasonable, then meal should not have to be fed until housing in November, saving a further €18/head. The potential to save €36/head is substantial.

Some farmers will feed meal because they’ve always fed meal. But as the figures show, most calves won’t need meal for growth, especially not over the summer. Beating the liveweight targets and having super calves is not something to aim for. The targets are the targets, not a minimum weight target.

Emer Kennedy’s research work in Moorepark has shown that heifers that are above target weight at mating have a lower conception rate and are more likely to be infertile after their first lactation.

“We stopped feeding meal last weekend. This is a few weeks later than last summer but I didn’t feel grass quality was good enough until now. The heifers are going to be weighed for the first time next week, but I’m guessing they are weighing 170kg.

‘‘My cows weigh about 600kg so the target weight for the calves is just over 160kg. The spread between the heifers is very small, maybe about 20kg as they were all born within a two-week period. We only breed enough for what we want so we get them to calve compactly. If there were a few lighter ones, I would pull them out and keep them separate but I’m fairly sure they’re all on target.

‘‘They had been on three-quarters of a kilo of meal but they’ll be on grass only from now until September when they will get 1kg per head until January. When in September to go back on meal will depend on grass quality and the weather. The plan is to move them to fresh grass every couple of days to keep performance up.”