Use teasers to synchronise ewes and lift weaning rates

Transcription

1 Use teasers to synchrone ewes and lift weaning rates Lamb loss in the first week after birth the biggest sue facing the Australian sheep industry. Animal reproduction expert Graeme Martin outlines some options Merino producers can use to improve flock reproductive efficiency and wean more lambs. by Graeme Martin, UNIVERSITY OF WESTERN AUSTRALIA Merino producers keen to lift weaning rates in flocks mated between October and the end of January can do so by teasing ewes. Teasing involves introducing vasectomed rams or testosterone-treated wethers to a flock of ewes. The practice advances the breeding season and synchrones the ewes breeding cycles so they mate with sires at the same time, so most ewes lamb within a defined period of 7 10 days. In addition, teasing gives sheep producers more control over when their lambs will be born, enabling feed supplies and supplements, and lambing conditions, to be planned to ensure the maximum number of lambs survive. Synchroned breeding A ewe s natural breeding season (the period when she produces an egg or ovulates) runs from February to May (see Figure 1). During th time, a ewe will produce an egg every 17 days. Ewes that are not cycling or At a glance Teasing early joined ewe flocks has several advantages. Most ewes are cycling when the entire rams are introduced. Pre-mating or pre-natal feed supplements are used more costeffectively because most ewes will cycle or lamb when expected. The lamb drop concentrated. The mating period can be reduced to 35 days. The efficiency of lamb marking, vaccination, mulesing and early weaning increased. The better the nutritional management of ewes, the more likely they are to have twins. Scanning to identify and segregate empty, single and twin-bearing ewes can be used. have had no contact with rams can be stimulated to start ovulation and breed earlier than their natural breeding season using the ram effect (also known as teasing ) The ram effect involves the sudden introduction of rams, vasectomed rams or testosterone-treated wethers (also known as teasers). Outside the natural breeding season a ewe s reproductive system shut down (anoestrus) and she does not ovulate (anovulation) unless she brought into contact with rams. FIGURE 1 A Merino ewe s breeding pattern Ewes ovulating (%) 100 January February March April May June July August 50 0 Breeding season But amazingly for Merino ewes, the introduction of rams (or teasers) during September to January will stimulate hormones in the ewes to switch on their reproductive systems. The process happens within seconds in response to the sight, sound and smell of the rams. For the ram effect to work, ewes need to be completely olated from males for at least two weeks. After mid-january, the ewes cycle without the need for the ram stimulus so teasing no longer works. Introducing a ram or teaser brings forward the breeding season. September October November December Non-breeding season January February March Note: The sudden introduction of a ram or teaser (testosterone-treated wether or vasectomed ram) advances the start of the breeding season and synchrones heat (oestrus) in ewes. 58

2 Livestock Within two days of introducing rams (or teasers) to the flock, ewes will produce their first egg and then go on to show a series of regular cycles. The ram effect a powerful tool that can allow sheep producers to synchrone the flock s reproductive activity. Large numbers of ewes ovulate, conceive and lamb over a short period and in concentrated bursts. Th maximes conception rates in a controlled joining, increases the costeffectiveness of predator control because the ewes all lamb over a short period of time, ensures lambs are an even size at marking, weaning and shearing, and improves the likelihood of most maiden ewes reaching the required weight at their first joining. For example, experiments at Western Australia s Narrogin Agricultural College used 1173 ewes, of which 879 were teased with testosterone-treated wethers. After three weeks of subsequent mating, 19 per cent more teased ewes had conceived than ewes that had not been teased. In one experiment, the lambs were weighed four days after the last lamb was born to measure the effect of the concentrated lambing. The lambs from the teased ewes weighed an average of 13.5 FIGURE 2 Merino ewe response to rams Percentage of ewes in oestrus each day 10 5 Ovulate, no oestrus Ovulate, no oestrus Ovulate, oestrus Ovulate, oestrus Days after introduction of rams kilograms, while those from the unteased ewes only had an average weight of 12.7kg. Understanding Merino cycles During a ewe s first ovulation two days after the teasers are introduced to the flock a ewe will produce an egg but she will not come on heat (no oestrus). Th initial ovulation sometimes known as a silent heat, which cannot be detected by the rams (see Figure 2). A silent heat charactertic of: the first ovulation of the breeding season; the first ovulation induced by the ram effect; and probably the first ovulation of puberty. As a result, the first mating will not occur until another 17 days later when the ewe ovulates for the second time. Th why farmers are often two or three weeks out when they estimate the lambing time of their flock. For example, a farmer who introduces rams into the flock at the start of December will expect the ewes to lamb five months later but the peak of lambing usually 2 3 weeks after the expected date. Short cycles Another complication that some ewes (perhaps half the flock) will undergo a 6 8- day cycle after the first ovulation, instead a normal 17-day cycle. In th case, some of ewes will be ready to mate about three weeks after the rams enter the flock, while the rest will not be ready until about one week later. As a result, lambs are born at two different periods. The dadvantage of th phenomenon that it will produce two peaks of lambing and mean that management can be more of a Th 59

3 Th challenge because lambs are at slightly different stages of growth. Types of teasers Sire rams can be used as teasers but they will waste their energy competing for ewes in the first 2 3 weeks (when the ewes will not be coming on heat). In addition, there could be a few ewes cycling before teasing, causing problems by lambing 2 3 weeks earlier than the rest of the flock. All of these problems can be avoided by sterile mating (teasing the ewes with vasectomed rams or testosterone-treated wethers). Vasectomed rams are difficult to manage because they look like normal rams but they are infertile. A mtake could be potentially costly if animals were mtaken. From a farmer s perspective, wethers injected subcutaneously with five millilitres of testosterone look exactly the same before and after the injection but as far as a ewe concerned they smell and behave differently, allowing them to induce ovulation in ewes. Although wethers are becoming more difficult to find because they are being sold into the meat market for attractive prices, it not difficult for farmers to keep a small flock of wethers to be used as teasers. Teasing ewes with testosterone-treated weathers means all the ewes will respond to the rams at roughly the same time. Th means most of the ewes will come on heat over 7 10 days and then lamb over 7 10 days. When treating wethers with testosterone, observe the withholding periods and avoid selling these animals into the food chain. Identify testosterone-treated wethers using dtinct ear tags and re-use these wethers for teasing in following years. How many teasers are necessary? For the ram effect to work, keep ewes olated from males (no sight, smell or sound) for at least two weeks. For example, keep ewes separated from the flock rams (and the neighbours rams) by a dtance of one kilometre. Seven days before wethers are introduced to the flock, inject 5mL of testosterone (Synarot, Banrot or Tesgro, 75mg/mL, regtered for the control of pizzle rot in wethers) under their skin, near the base of the ear. Th makes the wethers produce pheromones and exhibit mating behaviour similar to that of rams for a few weeks. Two per cent of teasers will be enough to stimulate the ewes but a higher percentage, TABLE 1 Sheep scanning contractors Th Name Location Phone Pearce Stock Scan O Connell, NSW (02) Sheep Scanning (Justin May) Orange, NSW Ed Langron Warren, NSW Rob Powell Armadale, NSW Colin Norton Port Macquarie, NSW (02) Andrew Shearman Dubbo, NSW (02) Andrew Scott Coolac, NSW (02) David Kingston The Rock, NSW (02) Col Roberson Mangoplah, NSW (02) Josh Clayton Yeoval, NSW (02) Jock Dunn Ultra Sound Hay, NSW (02) Allbreed Genetics Wellcamp, (07) Artificial Breeding Centre Queensland Mike Rival Goondiwindi, Queensland (07) Darren Evans Derrinallum, Victoria (03) Genstock Kojonup, WA (08) Stocksmart Kojonup, WA (08) David Mitchell Narrogin, WA (08) Greg Fitzgerald Keith, SA Colin Trengove Naracoorte, SA Paul Cousins Booborowie, SA (08) Note: Th information has been compiled to asst members locate scanning contractors. It in no way acts as an endorsement of the suppliers of such services. Members are encouraged seek references from each contractor before engaging their services. 60

4 Livestock such as 6%, will probably induce a more synchroned mating. It could be useful to fit harnesses with raddles on the teasers to indicate how much of the ewe flock already cycling. After two weeks, remove the teasers and introduce the entire rams. Removal of teasers worthwhile because they compete with sires for ewes and may delay pregnancy until the teasers testosterone wears off. Th synchroned mating means 20% or more of the ewes could be coming on heat each day (compared with 6% when the ewes are cycling by themselves, after January). Provided there are enough rams (3% ideal) to handle the load when all the ewes are on heat within a 10-day period, the pregnancy rate will be high. Synchroned lambing allows producers to improve control of the lambing conditions provided shelter, feed and water to improve lamb survival. Leave the rams with the ewes for 30 days as th allows two opportunities for the ewes to mate days and days Feed animal needs Before introducing rams into the flock it important to feed them correctly, enabling their testes to grow and subsequently produce more sperm. Bigger testes allow rams to fertile more ewes within a short joining period. It takes about eight weeks to maxime test size and for the process of sperm production to be completed. Up to 750 grams of lupin per head daily recommended but if rams are on quality feed, they may not need lupins. It vital to measure the condition score of rams. They should be score three and not falling. Do not overfeed the rams as fat and unfit rams perform poorly. Ewes also need to be fed so they can maintain a condition score of three. Th enables the ewes to have enough body reserves to cope with pregnancy, particularly for twins. Remember that Merino ewes stimulated by the ram effect are mating outside their natural breeding season and so the number of twin ovulations will be lower than normal. Feeding lupin to ewes for one month before the teasers are introduced to the flock will trick the ewes into believing they are in good enough condition to gamble on twins (if their genes allow). When ewes are above a condition score of three, lupin might not be worthwhile but a few days of lupin feeding could be cheaper than maintaining ewes in a condition score of three. Other feeds can be used but lupin can be used in large amounts without causing acidos and they are an effective supplement TABLE 2 Mating before mid-january Day Activity 42 Prepare rams. Check: health, testes, teeth, hooves. Feed well until mating (for example, up to 750g of lupin per head daily). Fit but not fat. Prepare ewes Feed to maintain a condition score of three or plan to supplement with lupin. 28 Isolate the ewes from the rams (no sight, smell or sound for four weeks). 7 Prepare teaser wethers. Inject testosterone 5mL subcutaneously. 0 Put teaser wethers (up to 6%) with ewes. Use harnesses to indicate how many ewes are cycling. 15 Remove teasers. Put rams (up to 3%) with ewes. Feed ewes with lupins daily, up to 500g/head to days After day 22 reduce the lupin supplement to 100g per day to lower the rk of embryo mortality. 45 Remove rams Scan. Remove empty ewes (cull those who failed to fall pregnant twice). Separate singles from twin-bearers. Classify twin-bearing ewes as early and late Put twin-bearers and maidens in maternity ward 12 days before lambing 12 days before lambing Shelter, calm. of early lambers. of late lambers. Feed (such as pasture or a standing oat crop) and water nearby Supplement twinners and maidens 10 days before lambing 10 days before lambing Feed barley or maize grain of early lambers. of late lambers. (at 1% of bodyweight daily) or an appropriate pelleted diet. 13 weeks after lambing 13 weeks after lambing Weaning Nutritional management for growth. for ewes on dry feed. Continue feeding the ewes with lupins daily (up to 500g/head every day) up until three weeks after the introduction of the teasers, after which the lupin supplement can be reduced to 100g per day to reduce the rk of embryo mortality. Other useful tools Farmers who breed sheep from February onward can maxime their weaning rate by using ultrasound scanning. Ultrasound scanning will detect ewes that are empty, carrying a single lamb or twins. Such knowledge can help producers better plan their pre- and post-lambing feeding strategies, and their lambing conditions, to optime the weaning rate. If the mating has been poor, ultrasound scanning enables producers to adopt a backup plan or if mating has been successful, the scanning operator can indicate how many lambs were conceived and perhaps when they will be born, enabling feed resources to be planned. Dry ewes can be managed separately. If it their second unsuccessful mating, these ewes can be culled from the flock. Cost-effectiveness of scanning Ultrasound scanning will cost about $0.50 per animal to identify pregnant and empty ewes, $0.80/ewe to identify empty, singles or twins and up to about $2/ewe to detect the age of the fetus but competition between service providers (see Table 1) driving prices down. Often farmers with large flock numbers worry about spending money on scanning and then place too much pressure on scanning operators to maxime their daily 61

5 Questions remain While much known about the reproductive cycle of Merino ewes, some questions remain. Why do ewes fail to come on heat during their first ovulation? Why do some lambs have short cycles? Why do other breeds fail to respond to the ram effect? How long do ewes need to be kept in a condition score of three to maxime twinning? What the best percentage of teasers? What the best type of teaser? Is competition between teasers and sires a problem? What other feed types are as effective as lupins for increasing twinning? Why does lupin fail to work perfectly every time? Why cannot ewes be synchroned with teasers in their normal breeding season, from February onward? What other natural methods could be used to synchrone ewes at the time? Five to 10 years of concentrated research should answer many of these questions. Th throughput. But quality information worth paying for if it results in an increased value of lambs turned off the property. Management of twin-bearing ewes After ultrasound scanning has been carried out, it worth separating the twin-bearing ewes from the rest of the mob. These ewes are most likely to lose their lambs but have twice the number of potential lambs, so it pays to place them in a maternity ward of high-quality feed. Aim for ewes to lamb in a condition score of 2 3. A paddock with at least 200 millimetres of pasture or standing oat crop will provide adequate feed for the ewes and shelter for the lambs, improving their survival. Ensure water readily available. Merinos are not famous for being calm and th why they are such poor mothers. When dturbed by a motor bike, utility or dog, Merino ewes run away, often so far that they cannot find their lamb afterward. The same applies if they have to look for food or water. Supplementation of Merino ewes Merinos are not high producers of colostrum the first milk that essential for TABLE 3 Mating after mid-january lamb survival. One week of feeding just before lambing can double colostrum production in twin-bearing ewes. Barley, maize or an appropriate pelleted diet fed daily at 1% of the ewes bodyweight are excellent supplements for boosting colostrum production. Writing down the key management events when mating before or after mid- January (see Table 2 on page 61 and Table 3) can take the guesswork out of joining and allow sufficient feed to be provided to maxime lamb survival. Acknowledgements: Department of Agriculture, Western Australia, University of Sydney and Queensland Department of Primary Industries and Fheries. About the author Professor Graeme Martin an expert in animal reproduction. He based at the Faculty of Natural and Agricultural Sciences at the University of WA. gmartin@animals.uwa.edu.au Phone: (08) ; Fax: (08) Day Activity 56 Prepare rams Check: health, testes, teeth, hooves. Feed to maintain a condition score of three (fit but not fat). Lupin at up to 750g per head daily. 7 Flush the ewes Start to feed ewes daily with lupin (up to 500g/head). 0 Put rams out with ewes (2%) Continue feeding ewes daily with lupin (up to 500g/head). Use raddles to indicate how many ewes are mated during the first cycle. 7 Reduce the level of lupin fed but feed enough lupins to hold ewes in condition score three for the remainder of the mating. 35 Remove rams A 35-day joining gives the ewes two opportunities to mate. Th should be sufficient for good fertility if there are enough quality rams. A brief mating means a brief lambing Scan Remove empty ewes (cull those who failed to fall pregnant twice). Separate single-bearers from twin bearers. Classify twins as early and late Put twin-bearers and maidens in maternity ward. 12 days before lambing 12 days before lambing Shelter, calm. of early lambers. of late lambers. Feed (such as pasture or a standing oat crop), water nearby Supplement twinners and maidens 10 days before lambing 10 days before lambing 1% of bodyweight with barley or of early lambers. of late lambers. maize grain or an appropriate pelleted diet fed daily. 13 weeks after lambing 13 weeks after lambing Weaning Nutritional management for growth. 62