Management of Dairy Heifer From Weaning to Calving Today’s heifer replacements should be tomorrow’s top producers. Attention to young stock will mean a good line of heifers entering the herd as two-year- olds capable of producing to their genetic potential. Feeding and management should meet this objective by ensuring that heifers reach: A satisfactory weight at mating An adequate size and condition at first calving The two broad post-weaning periods are: 1. Weaning to mating (3 – 15 months of age) The onset of puberty, and hence the commencement of cycling, is related to weight rather than age. A delay in the onset of puberty could mean a later conception, resulting in delayed production or, at worst, no production. Calving patterns could easily be disrupted if the onset of puberty is delayed. All heifers must reach a minimum weight before joining. Post-weaning management must provide sufficient feed to reach certain target weights. Practical experience shows that there is some flexibility in the rate at which heifers need to grow at different stages to reach a satisfactory bodyweight. For a calf weaned at a live weight of 70 kg at 70 days, the average growth rate needs to be 0.4 kg/day to reach desired target weights at mating. Heifers can gain weight at up to 1.1 kg per day. There may be periods of quite low growth rates, provided these are compensated for by periods when feed is unrestricted and of good quality. As a guide, weight gain with unrestricted feeding on dry pasture is around 0.2 to 0.4 kg per day, on hay or silage it is 0.5 to 0.7 kg per day and on green leafy pasture 0.7 to 1 kg per day. 2. Mating to calving (15 – 24 months) All heifers should calve as two-yearolds. Calving at three years of age does not return enough extra milk to cover the increased cost of feeding the heifer an extra year to calving. Herd and nutritional management may b complicated if heifers are joined to calve later than two years of age. Undersized two-year-olds are poor competitors for feed after calving and because they are still growing, feed is used for growth rather than milk production. Hence production is likely to be poor and difficulties may arise in getting the heifers back into calf. Therefore, heifer management should aim for: Well grown heifers at calving Butterfat production of first calvers to be within 30 – 35 kg of mature cows Good body condition at calving – condition score at 3 Another useful measurement is height at withers (shoulders). A relationship exists between the height of the animal and its weight. A minimum recommended wither height can be equated to minimum recommended heifer weight. Measuring wither height on the farm can be done in a number of ways. A couple of ideas are: Target weights for dairy heifers Because dairy heifers must attain satisfactory growth rates and reach sufficient size to be good producing members of the milking herd, regular checks should be made on them to ensure they are achieving these standards. Minimum recommended weights are available for different classes of livestock at certain ages. Heifers under target weight should be treated preferentially by: Walk stock through a race with a stick or similar object set at the recommended height. Stock needing to stoop under the stick are above weight, those that do not touch it need special treatment. Feeding more, and better quality pasture A better method is to mark a line on a convenient fence or race at the recommended height and run stock between the markers and yourself. By eyeing the stock with the line under weight animals can be identified. Supplementing pasture with pellets, grains and or hay, silage. Often stock weight is difficult to record on farms, since scales are not available. Alternative methods of measurement are available which give a reasonable approximation of body weight. One such measurement is chest girth. Using a dressmaker’s or similar tape, and measuring just behind the forelegs of the animal can make an estimate of the heifer’s weight. Beware of using plastic tapes, as they have a habit of stretching. The table gives the minimum target weights, chest girths and wither heights for Jersey and Friesian animals. For crossbred animals and other breeds, estimates can be made from the table for the approximate minimum recommended weight and corresponding measurements. Minimum target weights for dairy heifers Liveweight (kg) Age (months) Weaning Jersey Friesian Chest girth (cm) Jersey Friesian 2 60 70 87 12 480 230 127 Mating 15 220 290 Calving 24 320 410 92 Wither height (cm) Jersey Friesian. - - 139 100 104 137 151 109 114 157 170 116 125 Grazing management for heifers Grazing management should allow for continuous growth throughout the rearing period. Uniform growth is not necessary and may be impracticable with fluctuating pasture availability. However, it is most important to avoid periods of very low growth or weight loss. Grazing systems suitable are: that may be Rotationally graze young stock ahead of milkers Graze young stock behind milkers, grazing out a paddock for 3 – 4 days before moving onto the next paddock. Graze two replacements per pasture paddock. This provides ample feed, without affecting available milker feed. At such a low stocking rate, parasite buildup will be minimised. Rotationally graze young stock around the farm, independent of milkers. This is a good system if care is taken to ensure adequate feed is available. Agist young stick off the farm. Dry standing pasture will achieve satisfactory growth rates, providing it is in ample supply and of good quality. Quality green pasture is preference. These methods do not allocate paddocks solely for use by young stock, so more paddocks are available for grazing by the milkers. Set-stocking can result in underfeeding and a heavy worm burden on young stock unless care is taken. Feeding with hay or concentrates will be necessary as a supplement when pasture is in short supply. However, remember that pasture is the cheapest feed source on your farm, and that excessive supplementary feeding and excessive growth rates (particularly if growth rates are above 1 kg per day during the age 7 – 12 months) appear to lead to excessive fat deposition in the udder and poor milking performance. So concentrates should only be used as a supplement, not as a substitute for pasture. Stock Health With any grazing system for heifers the need to care for animal health is paramount, but too often neglected. Worm and liver fluke infestations are the most common disease problems, and a drenching programme should be adopted to minimise any build-up of parasites. A basic drenching programme would begin with both a worm and liver fluke treatment (if liver fluke is a district problem) at weaning followed by further worm treatments every three months and liver fluke treatments every six months. All replacement heifers should be vaccinated twice with “five-in-one” vaccine by four months of age. On properties where black disease is a problem annual booster vaccinations with “five-in-one” will be necessary. Vaccination for leptospirosis should be carried out before calving with two vaccinations four weeks apart. Regular observation of heifers is necessary to check for problems. The common symptoms of disease are ill-thrift, roughness of the coat, scouring or coughing. Prevention is better than cure. Disease can make a good lime of heifers lose up to a month’s condition in a few days. Mating Heifers If heifers have achieved satisfactory growth rates, they will be at a suitable liveweight for mating and be showing clear signs of cycling by 14 – 15 months of age. Many farmers use a bull over their heifers. Select a bull that is young or light-framed to avoid physical damage and preferably one known to throw a small-sized calf. When using a bull, a practical way to check whether he is performing satisfactorily is to use recognised tail paint on the heifers and observe them at least twice weekly after the start of mating. After three weeks, repaint the heifers with paint of a different colour. Continuing observation helps determine those heifers that appear to be in calf; the tail paint is not rubbed off. It also gives some guide to the fertility of the bull running with the heifers. Watch the bull at work to make sure he is actually serving the heifers. An injured or ill bull may only mount, rubbing off the tail paint, but not inseminate them. If the paint stripes on many of the heifers are being rubbed off regularly after three-week periods (that is after they should have been mated) then it can be assumed that either the bull is a at fault, or , if the heifers are thin, that they could be temporarily infertile. If the heifers are well grown and in good condition then the bull should be changed. If the heifers are thin, a better level of feeding is necessary. 60% to 70% of heifers should be mated within the first three weeks, and not return to heat in the next three weeks. A lesser percentage would suggest that the remaining heifers and the bull be examined by a veterinarian. For good conception rates, one bull for 25 – 30 heifers is the best ratio. This avoids both temporary infertility and physical incapability on the part of the bull. There is growing trend toward using artificial insemination on heifers to increase the speed of genetic improvement in the herd. By holding heifers in a handy paddock, using tail paint and regular observations, heifers in heat can be detected for insemination. This interest has led to the increased use of prostaglandins to synchronise heats in heifers for artificial insemination. Systems used include single or double injections of prostaglandins followed by visual heat detection and insemination, or blanket insemination over all synchronised heifers. Whether using a bull or AI, you should aim to mate 10 – 15% more heifers that required to allow for losses such as heifers not in calf, abortions and deaths. Also, mating heifers to calve 10 days ahead of the cows allows time to patiently break them into shed routine. Pregnancy testing after six weeks of mating permits a check on the fertility of the bull, and fecundity of the heifers. Any heifer that is not going to be able to get into calf can be culled. Stockmanship Young stock are inquisitive. Avoid putting them where there are cliffs, steep-sided drains and other death traps. They may also try to eat pieces of wire and hay bale strings, which can injure them. Handle young stock as much as possible. Regular walks through the mob and hand feeding make them quiet. This can save time when shifting stock or where fencing is inadequate. Running heifers through the milking shed routine before they calve, if done quietly, will make breaking them in after calving much easier. Summing up The penalties for management are: poor heifer Higher costs for getting animals to a satisfactory size and weight A loss of returns through low production in first lactation A high culling rate in two-yearolds because they are hard to get back in calf More money spent on stock medicines More time and money spent per animal An upset mating programme caused by a spread out calving pattern in young stock Better management of young stock through adequate care and nutrition encourages full expression of their potential.