Having your replacements at target weight, from birth to calving, is one of the most important aspects of dairy farming.
Yet this aspect of dairying is often neglected — and only about half our replacements calve-down at less than 30 months. Many of those that calve-down at two years old are under-weight.
Based on their research trials, Teagasc has set the following targets: At six months, the target for Holstein Friesian and Holstein Friesian x Norwegian Red crosses is 175kg; 164kg for Holstein Friesian x Jersey.
Teagasc target live-weights at AI, for different breeds, are: 330kg, for Holstein Friesians and Norwegian Red crosses; 315kg, for New Zealand Friesian; and 295kg, for Friesian/Jersey crosses. These weights are about 60% of target, pre-calving, first-lactation weights. Condition scores must also be correct (Heifers at condition score (CS) 3.25 produced about 160 gallons more than heifers at CS 2.75).
Pre-calving target weights should be 550kg for all, except the Holstein Friesian x Jersey (490kg).
Based on a study with 1,400 heifers on 40 farms, the Teagasc researchers concluded:
* Live-weight at the start of mating is more important than age.
Heavier heifers produce significantly more milk than lighter heifers.
Weight at first-calving significantly affects second-lactation milk yield.
Heifers weighing less than 290kg at AI produced 160 gallons of milk less than heifers weighing over 342kg at AI.
But overweight heifers are not satisfactory.
Teagasc research showed it was practical to have heifers at the ideal weight, calving-down at 22 months, an opportunity for farmers with late-calving herds to bring forward, and compact, calving dates.
If replacement performance is not satisfactory, it will affect herd performance for years to come.
Heifer calves must be treated properly from day one. They should be gaining at least 0.8kg during the grazing season, and now is a good time to check their performance (by weighing, if possible). It is not practical, on most farms, to achieve this weight-gain without concentrates, especially this year, when there is huge demand for grass and silage.
If calves stay still, or go backward, in weight for any significant period, it will be almost impossible to make up for lost gain, because over-feeding later could endanger mammary development.
The consequences of having calves behind target are that they will usually end up calving-down under target weight, or calving late, with serious loss of milk for the first and second lactations.
Therefore, calf-rearing (and breeding) are the first steps in successful dairying. Young, or backward, calves should get special attention now, rather than later.
The ideal grazing system for calves is the leader-follower system, where calves are grazing in front of older stock — but this is not always practical.
Aftergrass is ideal for calves, because it is likely to be free from parasites, as well as being very digestible. The more often that calves get fresh, clean pastures, the better, as there is less exposure to parasites.
Excellent parasite control is essential, especially in July. There are a number of different parasite-control options available, and which ever one is chosen should be followed carefully.
Unless animals are in very good order coming out of the winter-feed regime, they may not meet breeding targets for early-calving.
Traditionally, replacements have been fed on silage for the first winter. Trials have shown that unless the silage quality is very high, they will need 1kg to 2kg of concentrates to achieve targets.
Trials in Moorepark have shown that yearlings can be satisfactorily reared on forage crops, supplemented with silage or hay.
Kale is a superior feed to silage, and can provide a significant cost-saving, but, like all forage crops, it is only suitable on very dry ground. Feeding forage crops can complicate the management system, but where big numbers are involved it is worth considering, especially this year, when there is likely to be a shortage of silage.
The best cost-saving opportunity is being able to provide good-quality early grass, where heifers will gain double the weight gain per day at half the cost of most wintering systems. The importance of early grass for replacements is often ignored.
About 18 to 20% replacement is desirable, to raise the EBI of the herd and keep it relatively young and healthy — but our national average is around 28%.
High levels of replacements reduce herd milk yields, as first-calvers usually produce only 80% of mature-cow yields.
Replacement costs in dairying are generally very high, but, due to the high value of culls this year, net replacement costs are reduced.
Farmers should do everything possible to reduce replacement costs.
What can they do?
* All replacements should be bred from AI bulls with a proven, high-fertility index.
* Reduce involuntary culling, by taking good care of the health and reproduction of cows.
* Follow best advice on having cows at the correct condition score, especially at calving and breeding.
* Avoid short lactations and low milk yields per cow. Match cows and quota.
* Late calves must get special attention, to calve-down at 22 months, early in the season at the proper weight, which will have a very favourable effect on the calving pattern.
* Almost half of our dairy heifers don’t calve under the age of 30 months, and this is a serious loss to dairy farmers. Make sure that your calves are thriving from birth to calving.
* Raising milk-yields-per-cow can have a big effect in reducing replacement costs. For example, a 20% replacement rate for a 75,000 gallons quota in a 1,000 gallon herd requires 15 heifers. A 20% replacement rate for the same size quota, in a 1,400-gallon herd, requires only 11 heifers.
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