Rearing replacement heifers can be a major drain on farm resources even when the replacement enterprise is managed well. The growing cost of getting heifers into the herd has focused Dairylink project farmers to not only look at the cost of rearing each heifer from birth to the point of calving, but also can the rate of replacement within the dairy herd be reduced.
What is an acceptable replacement rate for a herd? The ultimate aim is to minimise the number of replacement stock needed to keep the main herd fit and healthy. A lower replacement rate may free up valuable resources of land and labour.
All replacements are born on farm between August and September, which allows heifers to calve down at 24 months in the autumn. Breeding starts on the farm in December and I focus on the first eight weeks' breeding with black and white semen. Normally 100 straws are used in the first eight weeks, with sires selected from the EBI on fertility and milk solids.
A stock bull or beef semen is used outside the first eight weeks. This keeps my replacement heifers in a tight group, allowing heifers to be reared together as one group with very little difference in size or weight right through to calving. I feel it is critical for my autumn-calving herd to maintain a compact calving profile. Last year, 24 heifers came into the herd at the start of the calving period. On average, approximately 60:40 male to female calves are born each year. However, last year it was only 31% female calves which means we are short of replacement heifers. Because I have an expanding herd I would really need more heifers to bring into the herd. This year I have bred for an additional two weeks with black and white semen to help boost replacement numbers going forward. My replacement rate of 44% is high but in effect this is due to the herd expanding and includes heifers brought into the herd and purchased stock.
Currently the two main costs for the heifer enterprise are meal feeding and forage costs, which includes fertiliser and contracting charges. 590kg/head of concentrate was fed last year, with the majority of this concentrate fed at the early stage of growth through weaning and into the first five months of life. We target a weaning weight of 85/90kg and a breeding weight of 360kg for the heifers. Heifer growth has been good this year, with the young heifer group now 260kg and still another six months before breeding. Only a growth rate of 0.5kgs/day is needed for these heifers which we can achieve on grass only.
I have skipped a lot of paddocks and taken the grass off in bales. Last week I had another six acres baled. Grass in these paddocks is between 3,000 and 3,500kg available cover. June is a busy month for my contractor so sometimes we have to wait, and with growth rates above 100kg/day, grass will bulk up fast.
On average, the grass ahead of the cows is of good quality, with low levels of stem in the sward. I have been using the topper after cows move out of paddocks to get the stemmy grass cut out of the sward, which has worked well. However, the paddocks taken out as silage have excellent quality regrowth at this stage.
Growth has slowed this week with a drop in temperature, but the rain over the past weekend will help keep growth moving. At this stage I have all the surplus grass removed from the grazing block and all paddocks are included in the grass wedge for the farm.
My daily grass demand per day is 65kg/ha and last week’s growth was recorded at 126kg/ha. Even if growth slows over the next three weeks, I can allow my average farm cover to come down before starting to increase supplement feeding. Milk protein levels have been low for the herd over the past three weeks. However, cows are milking well in terms of volume which is holding the total milk solids produced for the herd.
I am now in the eighth week of breeding, with fewer cows repeating than this time last year. Cows are in good condition and a more compact calving profile means I have more cows bred in the first six weeks than ever before. Hereford semen is used on cows from the sixth week of breeding onwards.
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