Pasture Management for Sheep

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Pasture management for sheep

Sixty per cent of UK farmland is only suitable for growing grass. These large areas of ground lock up in the region of 400 million tonnes of carbon. Efficient use of grass for our 65 million sheep is essential for many reasons; including reduction in feed costs, increased daily live weight gains, parasite management and reducing methane emissions. Josephine Child BVetMed MRCVS The UK sheep industry has a “Despite being the cheapest feed unique stratified system to Josephine graduated from maximise the efficiency of available for ruminants, grass remains the Royal Veterinary College all areas capable of growing vastly underutilised” in 2011 before moving to a grass; from the hill breeds large farm animal practice found in the Welsh mountains in Wiltshire. In 2016 she and Scottish highlands down grass growth. Despite being stocked but can’t match relocated further west to the lowland terminal breeds the cheapest feed available for animal requirements with to Dorset; joining Friars producing high quality, fast- ruminants, grass remains grass growth throughout Moor Livestock Health. growing lamb. vastly underutilised. the whole season; they are Since joining Friars Moor, only optimally grazed for a Josephine has become an The most commonly sewn Types of grazing systems short period of time. They integral member of the Dairy grass in the UK is perennial Set stocking is the oldest form are mostly grazed unevenly Sheep and Goat Consultancy ryegrass. Each individual grass of grazing management. Sheep – being either overstocked team at the practice as well plant, or ‘tiller’, starts off are stocked to the grazing leading to poaching and as continuing to develop a growing one leaf, then a second, depending on expected undernutrition with grass not keen interest in preventive third and so on, however there annual grass yield, but low reaching optimum growth, flock healthcare, fertility and will only ever be three live leaves stocking pressure. Large or understocked leading to parasites. She is midway on a tiller; as the fourth leaf areas are grazed over a long poor grass utilisation with lots through studying for a grows, the first dies. Optimum period of time which reduces of dead matter in the sward. CertAVP in production animal nutrition is found in the management impacts of Grass utilisation in a set medicine with the University 2.5-3 leaf stage, when live leaf moving animals regularly, but stocked system is often below of Liverpool. surface area of each plant is offers little control over sward 50 per cent, with average highest, growth rate is highest heights. Sward should ideally annual yields being 6t DM/ha. and sward yield maximal. be 6-8cm which is the height Rate of growth of each leaf at which most plants are likely Rotational systems are based depends on time of year, soil to be in the 2.5-3 leaf stage, on balancing sward heights type, weather, temperature but as rate of grass growth and maximising yield of and management. The rate of changes through the season, it grass while managing levels grass growth will influence how is difficult to maintain without of parasite risk for different long it can be grazed for and altering stocking rates. classes of stock. Sheep should measuring this helps to utilise aim to go into a sward at grass for optimum nutrition Hill systems and extensive 10cm and come out at 4-5cm as well as stimulating further grazing systems are set (slightly higher for weaned

Table 1. Target sward heights for sheep (AHDB, 2018)

Rotational grazing Continuous grazing Grazing (set stocking or Class of stock period Pre-graze Post-graze relaxed rotational) (cm) (cm) (cm) 0.5 hours* Turn-out – May 8-10 4-5 4 Ewes and lambs May – weaning 8-10 4-6 4-6

*Suggested Personal & Professional Development (PPD) Pre-tupping ewes Sept-Nov 8-10 4-5 6-8

PASTURE MANAGEMENT Weaned finishing lambs Jul-Sep 10-12 5-7 6-8

finishing lambs) (Table 1) systems and helps extend the only for a very short period as in Figure 1, or calculate before pasture is rested for grazing season. More labour is of time, with sheep typically a feed budget of expected a number of days. Typically, involved in moving stock and moving every couple of demand and estimated grass rotations last 20-30 days providing adequate water to days. These systems require growth to decide how many dependant on season. Using several fields. highest labour inputs for paddocks are required. pastures in this way means moving fences regularly and that each rotation is grazed Paddock grazing, also known monitoring grass growth. Parasite management quite hard but has a long as cell or precision grazing, Initial set-up costs may be high One of the main reasons for time to recover. Traditional is a more intensive form of owing to investments in fencing needing effective grazing rotational systems can reach rotational grazing. Swards and water provision. This management is parasites. grass utilisation levels of 60- remain slightly higher, in sort of grazing management With a large percentage 65 per cent. Stocking density multiple small paddocks; has been shown to increase of sheep farms in the UK is higher than in set stocked stocking pressure is high but bite rate, step count, intakes experiencing resistance and lead to higher daily live to one or more classes of Figure 1. Example calculation. weight gain per hectare with anthelmintic, it is important the added benefit of reducing to find other strategies to carbon emissions by 64 per minimise both worm burdens 1. Typical residual target (post graze cover) should be cent per production unit area and their production-limiting 1500kg DM (AHDB, 2018) (Savian, 2018). These systems effects. Grazed pasture Using your sward stick measurements (pre-graze cover) improve grass utilisation by looks after the ‘in refugia’ calculate the grazing provision available: up to 80 per cent – allowing population of parasites. pre-graze cover – post graze residual x field area for maximal grass regrowth That is, the proportion (2500 kg DM/ha – 1600kg DM/ha ) x 2 ha = 1800kg DM in between short periods of of parasites present that grazing. Annual yields can are not in the animal and 2. Allocation of DM intake varies on stage of lactation from average 10.2t DM/ha. therefore not exposed to 1-4 per cent bodyweight (AHDB, 2018) an anthelmintic treatment. Ewes with lambs at foot should be allocated 3 per cent bodyweight Developing a grazing plan Preserving a susceptible Calculate the livestock allocation: Planning grazing means in refugia population is 200 Ewes with lambs at foot = 60kg body weight x 3 per cent measuring grass growth important for preserving 200 x (60 x 0.03) = 360kg DM/day provision using a plate meter or sward activity of anthelmintics. stick. Walk each field in a ‘W’ Since 90 per cent of infective 3. Calculate how long the grazing will last by dividing step pattern; taking 40 leaf-top L3 larvae is found towards one by step two: measurements and then take the base of the sward 1800 / 360 = 5 days grazing. an average. Either calculate (Van Dijk, 2009), higher the provision of the area and sward heights can help to allocate livestock accordingly reduce parasitism.

High liver fluke risk area. Photo credit Lucy Hepworth.

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Table 2. Assessing pasture risk for worm control in sheep (AHDB, 2018)

Season High risk Medium risk Low risk Ewes and lambs grazed in the Grazed only by adult New leys or forage crops. previous year. non-lactating sheep the previous year. Grazed by cattle or cut for silage High risk of Nematodirus if or hay in the previous year pasture carried ewes and lambs Grazed by ewes and lambs (no sheep). Spring in the previous spring. the previous spring, but then (ewes and young lambs) conserved and aftermath Goats grazed the previous year. not grazed by sheep (NB Nematodirus still high risk). Store/ewe lambs grazed the previous autumn/winter. Grazed only by adult non- Grazed by cattle or cut for silage lactating sheep in the spring. or hay only in the first half of the Summer Ewes and lambs grazed in grazing season. (ewes and the spring. Grazed by cattle or cut for pre-weaned lambs) silage or hay in the spring. Forage crops or arable by-products grown. Grazed by cattle since Grazed by cattle or cut for silage mid-season. or hay only in the first half of the Late season/autumn Stocked with ewes and lambs grazing season. (weaned lambs) all season. Grazed by fit, mature dry ewes since weaning mid-season. Forage crops or arable by-products grown.

Each grazing system has its advantages for reducing parasitism; set stocked systems have low stocking rates but uneven grazing can cause higher parasite burdens in some areas. Rotational grazing provides a higher sward height for a larger length of time and intends moving sheep on to new pasture every 20-30 days before the nematode life cycle is completed, but pasture contamination will be high. Paddocks or cells are moved every few days, allowing little parasite development but care should be taken that sheep are not moved through all paddocks so quickly that they return to previously grazed paddocks before enough infective larvae has died off on the pasture. This would inadvertently increase parasitism. Since larval development time depends on moisture and temperature, appropriate time to return to a grazed rotation can range from days to weeks. Understanding the factors Paddock grazing. Photo credit Mike Miller. that affect larval development can be used to categorise

“One of the main reasons for needing References effective grazing management is parasites” ADAS (2011). Impact of grazing management on cattle and sheep parasites: REVIEW ADAS UK limited Available at http://beefandlamb.ahdb.org.uk/wp- content/uploads/2013/04/impactofgrazingmanagementoncattleandsheepparasi risk levels of pasture for how immunity in the periparturient tes_0411-final-report.pdf infected they might be. This is period and increased egg especially useful post-weaning output by ewes. Carefully AHDB (2014). Homegrown forages directory. AHDB Better Returns Programme when ewes can follow lambs selecting swards with herbs available at: http://beefandlamb.ahdb.org.uk/wp-content/uploads/2014/12/ in rotation; ensuring cleaner and legumes in them around BRP-Home-grown-forages-directory-181214.pdf grazing for weaned, fattening lambing time can increase lambs. Rotating permanent ewe milk production and, AHDB (2018). Feeding the ewe. AHDB Better Returns Programme available at grazing with arable crops or therefore, lamb growth http://beefandlamb.ahdb.org.uk/wp-content/uploads/2018/03/Feeding-the-ewe.pdf fields cut for hay or silage will rates compared to ryegrass- help to keep parasite burdens dominant pastures alone AHDB (2018). Planning grazing strategies for better returns. AHDB Better down (Table 2). (Hutton, 2011). Returns Programme available at: http://beefandlamb.ahdb.org.uk/wp-content/ uploads/2016/07/BRP-Planning-grazing-strategies-manual-8-150716.pdf Alternative grass Post-weaning, the best grass forage crops available can be used for AHDB (2018). Worm control in sheep for Better Returns. Programme available at Over recent years, there has finishing lambs and poorer http://beefandlamb.ahdb.org.uk/wp-content/uploads/2018/05/Worm-Control- been more interest in growing yielding fields for drying Guide_2018_05_03-WEB.pdf and integrating alternative off ewes. At all stages of forages into grass to further the production cycle, body Hutton, P.G. et al. (2011). ‘A herb and legume sward mix increased ewe milk improve efficiencies. Clover condition scoring of ewes production and ewe and lamb live weight gain to weaning compared to a species grow fast and provide should be used to monitor ryegrass dominant sward’ Animal Feed Science and Technology’ 164 (1) 1-7. high energy and protein progress. To increase body levels per hectare of growth, condition score by one unit is Marley, C.L. et al. (2006). ‘The effect of mixed or sequential grazing of cattle and making these swards ideal for the equivalent to feeding 1kg/ sheep on the faecal egg counts and growth rates of weaned lambs when treated finishing lambs. day of good quality grass for with anthelmintics ‘ Veterinary Parasitology 142 (1) 134-141. ten weeks. Chicory and plantain profess Savian.J.V, et al. (2018). ‘Rotatinous stocking: a grazing management innovation to have natural anthelmintic It is also important to that has high potential to mitigate methane emissions by sheep’ Journal of properties; with lambs grazed establish liver fluke history Cleaner production 186; 602-608. on chicory based-systems on the farm through faecal having a lower adult worm testing, serological testing in SCOPS (2013). ‘Sustainable control of parasites in sheep’ available at: burden, despite having lambs, and abattoir reports. www.scops.org.uk similar faecal worm egg This is essential for mapping counts when experimentally high-risk pastures, snail Somasiri, S.C. et al. (2015) ‘Growth performance and carcass characteristics of infected with trichostrongylus habitats and knowing when to lambs grazing mixes inclusive of plantain (Plantago lanceolate L.) and chicory species compared to those avoid them. Highest risk areas (Chicorium intybus L.)’ Small Ruminant Research 127, 20-27. on a grass-clover mix might be wet habitats preserved (Tzamaloukas, 2005). by environmental grazing Tzamaloukas, O. et al. (2005). ‘The consequences of short-term grazing of schemes or where sheep are bioactive forages on established adult and incoming larvae populations of Chicory-plantain clover or overwintered on wetland. Telodorsagia circumcinta in lambs’ International Journal of Parasitology 35 (3) plantain-clover mixes have 329-335. also been shown to produce Mixed grazing lambs with higher slaughter One strategy to consider and carcass weights and, is mixed (co-grazing) or therefore, higher production sequential grazing of sheep per hectare than ryegrass and and cattle. Marley et al (2006) white clover alone. found higher lamb growth rates when cattle and sheep Seasonality were co-grazed through the Some farms prefer to set whole season, and lower stock ewes around lambing, faecal egg counts in lambs especially if lambing outside. when sheep followed cattle Fields can be stocked shortly sequentially in the grazing before, and left there until all pattern. Cattle will graze the ewes have lambed. This higher sward heights, and makes observation easier and since parasites are largely reduces the requirement to species specific, it can help move periparturient ewes. to reduce contamination for Parasite burdens on these lambs that follow. pastures are likely to be high owing to relaxation of

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