OPTIMISING BEEF PRODUCTION FROM PASTURE Duncan Smeaton, AgResearch, Ruakura Research Centre, Hamilton

Transcription

1 CHAPTER 6 OPTIMISING BEEF PRODUCTION FROM PASTURE Duncan Smeaton, AgResearch, Ruakura Research Centre, Hamilton Summary A key competitive advantage of the beef industry in New Zealand is the relatively low cost of consumed pasture. However, it is a seasonal feed supply. The challenge for beef farmers is to utilise a high proportion of feed grown and achieve biological efficiency on the one hand, compatible with optimum marketing or selling decisions on the other hand. These do not always complement each other. The feed demand of growing animals does not match the seasonal pasture growth curve very well. In the end, the most profitable beef production system may well not be the most biologically efficient one or one, that utilises the most pasture. There are various ways by which farmers match feed supply and demand, and some are more profitable than others. Pasture production varies depending on numerous factors. Beef production systems demand high quality pasture and high cattle growth rates, which are conflicting requirements. Maintaining high animal growth rates and high pasture quality at the same time is very difficult. Many farmers use a low priority stock class, such as a breeding cow, to do this. However, this can be a cost in its own right. Grazing affects pasture growth. As pasture mass increases, pasture decay at the bottom of the sward also increases, thereby offsetting the gains from new growth. Because 60-70% of pasture growth occurs during the spring early summer, a substantial proportion may not be consumed. Management of the quality of this surplus feed is one of the greatest challenges of livestock farming. There are various tools for maintaining a supply of high nutritive value feed to cattle. These include: fertiliser and nitrogen application, maintaining pastures at the appropriate grazing height, topping and conservation of surplus pasture, subdivision, flexible stocking rates by buying and selling stock, forage cropping for feed deficit periods, use of supplements and manipulation of winter and spring rotation lengths to take advantage of compensatory growth. CHAPTER 6 Optimising Beef Production from Pasture 61

2 Use of supplements, may or may not be profitable. Features of supplementation to be aware of include: Wastage at all stages The problem of substitution (whereby cattle substitute the intake of supplement for pasture) Animal health risks (acidosis which occurs with supplements that have a high concentration of soluble carbohydrates). Introduction As described in the previous chapter, beef production is a complex assortment of trade-offs between the need for good FCE (feed conversion efficiency), maintenance of pasture quality, fitting growing animal feed requirements with a variable and seasonal pasture production curve, and fitting in with marketing requirements. Markets want a product that is supplied consistently all year round. This is a real, but difficult supply issue, because it conflicts with the seasonal nature of our pasture production system. Still, it is the reality and beef producers have to get as close to meeting the demands of the market as they can, while making an acceptable profit. To further complicate the above issues, many farms also have other stock classes that require attention such as ewes, lambs, and breeding cows. These other stock classes create flexibility in terms of pasture management, but also create complications, in terms of managing the production of beef cattle. Some general principals A key competitive advantage in the pastoral industry in New Zealand, compared to Northern Hemisphere beef producers, is the relatively low cost of consumed pasture. This is of the order of 6-10 cents per kg DM, although it can be argued that its relative value varies during the year (Chapter 13, Table 2). Intensive overseas operations have considerably greater costs, although our comparative advantage has been declining in recent years. Achieving an efficient and profitable beef finishing system is a challenge. Increasingly, success is the blend of efficient farm production and marketing decisions. These decisions are not always complementary to one another. Market driven trends of more cattle, larger carcasses, out-of-season supply and product uniformity are more demanding on our pasture-based systems. This is from a perspective of both feed supply and animal quality. In the past, key issues have been: Stocking rates that have been a compromise between efficient feed usage and adequate animal performance. Calving, lambing, purchasing and disposal dates that provide the major means of coping with variations in seasonal feed supply. 62 CHAPTER 6 Optimising Beef Production from Pasture

3 Mixtures of stock classes that complement each other and feed demand (quantity and quality). High value markets, with their requirements for continuous production, result in more demanding systems that are potentially poorly matched to seasonal patterns of pasture production and therefore biologically less efficient. Figure 1 shows that the feed demand of growing beef animals does not match the seasonal pasture production growth-curve very well. In fact, ewes weaning 150% lambs match pasture supply better than the cattle systems shown. The most biologically efficient farming system is one in which the maximum amount of pasture grown is utilised by the animals. However, the most profitable farming system may be that, which in fact is less efficient than the ewe system shown in Figure 1, but achieves animal production targets that are closely aligned with market requirements. Beef cattle production, as in all types of pasture livestock production, is a tradeoff between optimum biological efficiency on the one hand, and optimum financial productivity on the other. The present chapter aims to address these issues. Figure 1 implies that a lot of feed grown is wasted. While this may apply on some farms, many operators achieve a much closer match between supply and demand than indicated by: buying and selling stock manipulating stock performance to match pasture growth conserving surplus feed, as supplements to be fed during times of feed deficit using animal body condition as a means of storing and then feeding surplus feed purchasing feed supplements if the returns are deemed to be worth the cost manipulating calving dates and stocking rate removing paddocks from the rotation for the production of forage crops The above factors alter feed demand. Pasture growth rate can also be manipulated to help match animal demand, by using fertiliser and/or artificial nitrogen applications. Fertiliser has a long-term effect on pasture growth rate (Figure 2) and feed quality, while nitrogen provides a 4 to 8 week boost in growth rate, depending on growing conditions. CHAPTER 6 Optimising Beef Production from Pasture 63

4 Figure 1: Pasture growth on Whatawhata easy hill-country and feed demand of various stock classes/hectare/day, derived from Stockpol. This figure will vary depending on the pasture growth curve: for example, Figure 2. Successful management involves knowing which of the above options are profitable and which are not. Sometimes the most profitable option is to accept poorer performance, or more wasted pasture. Lateral thinking is often required to obtain the best solution and to utilise as much of the pasture that is grown, as possible. Pasture growth and production Figure 1 clearly demonstrates the dominating effect of rainfall and temperature or climate on pasture productivity and growth. This is relevant to different regions or land of different contour and can vary greatly between regions and years. Figure 2 shows the growth pattern for an area where rainfall clearly favours a small flush of growth in the autumn. This variation precludes the use of prescriptive recipes. Rather, managers need to be armed with principles and facts that they apply to their particular circumstances. It should be noted that differences in pasture growth between years are greatest between December and April as a consequence of rainfall. That is the reason why breeding systems involving sheep or cows with stable capital stock numbers over winter, and flexible disposable stock policies over summer and autumn, have been biologically very successful. Pasture production is dependent not only on climate, but also soil fertility (Figure 2). More fertile, developed pastures produce relatively better growth rates going into dry conditions and during winter, early spring: the two main crisis periods in the beef production system. Beef finishing systems demand higher levels of productivity over these times and are therefore much less suited 64 CHAPTER 6 Optimising Beef Production from Pasture

5 to low fertility farms, as shown in the comparison in Figure 2. Soil fertility not only affects pasture growth rate but also pasture quality. High fertility soils result in a change in pasture composition in favour of ryegrass and white clover, both of which are highly digestible. Figure 2: Example pasture growth rate pattern for a low fertility (soil Olsen P level less than 12) and a high fertility farm (soil Olsen P level greater than 20). The graph will also vary depending on climate and location. The performance targets for all stock on sheep and beef properties have also lifted in recent times. On many farms the proportion of working animals that can be used for pasture cleanup and maintenance of pasture quality has decreased because of the otherwise diminished profitability of these animals, relative to other stock classes. Instead, management techniques that prevent loss of control of rank pasture are attracting increased interest. The move towards more fecund sheep, heavier lamb weaning weights, and the perception that breeding cows are less profitable than other stock classes, means there is reduced opportunity to underfeed ewes and or cows and their replacements. There are fewer cows on sheep and beef farms than in previous years and those that remain are often expected to produce heavy weaner calves. This is a big ask for cows that are also expected to eat poor quality feed to maintain pasture quality for growing animals. Replacement of some, or all of the breeding cow component with finishing cattle, on the grounds of increased profitability, has compounded the pasture management problem. Finishing cattle must grow rapidly for biological efficiency, which requires high feed intakes and lax grazing of pasture. Unfortunately, this induces the production of rank, low quality feed especially in the late spring and early summer. As producers strive to improve the performance of their livestock, the way CHAPTER 6 Optimising Beef Production from Pasture 65

6 they are fed becomes more critical. Management of feed quality on sheep and beef properties is now acknowledged as one of the key factors in achieving high production targets. Improving pasture quality is one of the greatest opportunities farmers have to improve livestock performance, if they can successfully tread the narrow line between maintenance of feed quality and high cattle growth rates. Effects of animal management on pasture performance, competition and growth The type of grazing animal has a significant impact on pasture composition. Grazing predominantly with cattle reduces pasture density (especially ryegrass) and may cause soil surface damage or pugging which can take months to recover, causing lost pasture production. Some soil types such as clays are affected more than others. Annual pasture productivity may decline by up to 10-25% as a consequence. It is important therefore, that sheep, because of their different grazing behaviour, are occasionally grazed in cattle blocks. It is important to ensure that large cattle are not mobbed or grazed closely through steep country during the winter and early spring period (refer Chapter 10). Variations in grazing pressure have the most influence on pasture quality and clover content during October to March. Clover responds well to light and so is encouraged by close grazing during its maximum growth period of October to December. Low quality grasses such as Browntop, Yorkshire Fog and Danthonia, and weeds, are also discouraged by avoiding the growth of rank pastures during the December/March period. Maintaining pasture control also benefits pasture quality, and hence animal performance, during the summer and autumn period. It also encourages pasture density for maximum winter growth. This is particularly so for steeper hill country, which suffers most from mismanagement. Unfortunately, beef-finishing systems are in conflict with the above pasture needs. Impacts of grazing on pasture growth Pasture growth is determined mainly by climate and soil fertility, as described earlier in Figures 1 and 2. Pasture growth is also determined by leaf cover or pasture mass as shown in Figure 3. At low pasture mass levels, leaf cover is less than that required for the optimum interception of sunlight energy and hence pasture growth rate. At mass levels greater than 2000 to 2500kg DM/ha, pasture decay (equivalent to negative growth) increases significantly due to shading in the lower zone of the sward, while new growth rates do not increase further than the maximum level shown (Figure 3). The result is that the rate of net pasture accumulation or growth actually declines beyond an optimum pasture mass level (approximately 2000kg DM/ha in Figure 3). 66 CHAPTER 6 Optimising Beef Production from Pasture

7 Late winter/early spring and following drought periods are the times most likely to have insufficient leaf cover to achieve maximum potential pasture growth. Winter saved pasture and that grown in late spring to early summer can produce sward conditions when high pasture mass is most likely to detrimentally affect net growth. A pasture cover of a minimum of 1500kg DM/ha is required for optimum growth. Figure 3: A diagrammatic representation of the components that determine the rate of pasture accumulation (growth) across a range of pasture mass levels. The vertical difference between the new growth and the net growth lines is due to pasture decay, which is equivalent to negative growth. Clearly, a disciplined approach to rationing feed over the winter period is important for maintaining early spring pasture covers, to ensure maximum pasture growth rates are achieved over this critical time. As usual, a compromise is required. Rationing pasture in winter involves the use of long rotation lengths behind electric fences, with paddocks or grazing breaks grazed to low residual pasture levels of less than 1200kg DM/ha. These breaks will then have a period of less than optimum pasture growth. However, this is the price that has to be paid to ensure average farm or block cover is maintained at an optimum level. Disciplined pasture rationing is often more likely to be successful if the number of mobs is reduced. Integrated grazing of sheep and cattle during winter (for example cows with or before ewes, steers, heifers before hoggets) etc can reduce mob numbers and achieve priority feeding. It needs to be stressed that advancing calving and more particularly lambing dates does nothing to achieving this objective of minimum cover at the beginning of CHAPTER 6 Optimising Beef Production from Pasture 67

8 spring. For example, earlier lambing (late July versus late August) can increase lamb weaning weights by 2-3kg. But, research information has indicated that subsequently, ewes and finishing cattle will be lighter (4-5kg and 20-30kg respectively), and overall farm income will be lower. As an alternative to reducing numbers of mobs, many finishing beef farmers now run their cattle in specially dedicated, intensively subdivided areas to ensure accurate rationing and to avoid conflict with the feed requirements of other stock classes. High pasture quality and high cattle growth rates in the early spring are a positive feature of these systems. However, their monoculture nature can create animal health complications, especially with internal parasites (see Chapter 7). Some farmers attempt to minimise this by periodically running another stock species through the area, or by periodically growing forage crops. This eliminates most of the parasite load in the pasture. Ewes are effective in that they can often graze beneath intensive single electric-wire fences, thereby cleaning up large areas quickly. Grazing management can alter pasture performance during, and coming out of drought conditions. Reduced grazing pressure during the dry spell is the key to success under these circumstances, along with timely stock disposal as an additional, important tool. Recovery from drought can be aided by feeding supplements, once soils have become wet again. Feeding of hay or silage to breeding ewes and/or cows can be a means of increasing pasture cover after a dry summer/autumn. This increase in pasture cover can be critical to achieving adequate weight gains (greater than 0.5kg per day) on finishing cattle, during the subsequent winter and early spring. Pasture growth and utilisation Because 60-70% of pasture growth occurs during the spring early summer period and because of limitations to animal consumption, even under ad lib feeding conditions, a substantial amount of pasture produced over this period may not be consumed. The consequences of this are a reduction in the accumulation of pasture as shown in Figure 3 above and a subsequent decline in feed quality due to the accumulation of dead matter. The option to avoid this is to harvest surplus feed as hay or silage, to defer or set aside sacrifice lax grazed paddocks, to put paddocks into a summer crop, or to buy in extra stock to eat the surplus pasture. All these options have a cost which is difficult to quantify. The accumulation of dead matter results in a decline in pasture quality. This has been estimated such that for every 1% of extra dead material in the diet, feed digestibility declines by 0.5%. The significance of this is that with 40% dead matter in the diet (quite common during the summer/autumn period), digestibility will decline to 60-65%. This compares with leafy late-winter or early-spring pasture, which has a digestibility of 80%. As pasture digestibility declines, daily intake can also be expected to decline by one third from 68 CHAPTER 6 Optimising Beef Production from Pasture

9 maximum levels. This reduces the animal s intake to close to maintenance levels and helps to explain the reason for growth rates of young cattle over the summer/autumn period often not exceeding kg liveweight gain/day. The significance of the above relationships is that stock policy has a major effect on the size of the November to January feed surplus, the extent of seed head and dead DM accumulating in the sward and subsequent impacts on animal performance. From a grazing point of view, the key objective, as has been stated many times, is to achieve a balance between high pasture intake, pasture rejection and maintenance of pasture quality. Feed budgeting and assessment of pasture mass and quality Matching pasture supply with animal requirements, to ensure target performance is met, clearly requires knowledge of pasture availability and its quality. In addition, prediction of future surplus and deficit periods (as in financial performance budgeting) can only be achieved with accuracy, if future feed supplies and requirements are budgeted. Feed budgeting enables the farm manager to predict the size of feed deficit periods and their timing. This then allows him/her to determine what type of reaction (such as the use of supplements, stock sales or even doing nothing, which equates to accepting lower animal performance) is best. Feed budgeting allows a planned response to feed deficit situations and helps avoid emergency responses, which are almost always more costly. To be really effective, feed budgets need to be updated on a regular basis. Typically they operate on a daily basis and are averaged monthly, although other periods may be perfectly acceptable. Information required includes: Knowledge of feed on-hand. This requires an ability to assess pasture mass (kg DM/ha: see Appendix II) Assessment of pasture quality. As described above, pasture quality in the summer-autumn period can have an important impact on animal performance: see Further Reading below Knowledge of local pasture growth rates (The first Further Reading item contains this information) Farm or block area, available supplementary feeds (Appendix I), stock numbers and their target performance levels translated into daily feed intake requirements (Chapter 5) The rest of the process involves calculating feed demand and feed supply, determining the size of any deficits and considering what actions need to be taken to rectify the deficit if it exists. Computerised feed budgeting programmes are available, with some capable of handling several land and stock classes. In this category are programmes CHAPTER 6 Optimising Beef Production from Pasture 69

10 such as Stockpol and Bo-Vision. Alternatively, it is quite possible to set up a feed budget on a computer spreadsheet. Maintaining a supply of high nutritive value feed for growing cattle There is a wide range of means and techniques for maintaining or increasing the supply of high quality pasture to cattle. Some of these are pasture or paddockbased and are relatively simple to implement. Other techniques involve larger areas, or even the whole farm and may even require off-farm implementation or supplementation. Some effects are short term, others much longer. The list of options available is shown below, in increasing order of cost or difficulty. Fertiliser application. Aspects of this have been discussed above. Soil fertility has only small, direct affects on nutritive value, the most noticeable being the increase in protein content with nitrogen application and the correction of trace element deficiencies. However, the indirect affects of fertiliser are substantial. Removing soil fertility deficiencies are commonly associated with increased clover content, higher ryegrass content, faster nutrient cycling and quicker breakdown of dead material. As soil fertility increases, content of high-fertility type pasture and clover species increases and the content of low fertility tolerant species such as browntop, and sweet vernal, declines. Although quality of green leaf produced by these two groups of species are similar, ryegrass dominant pastures are easier to manage than browntop/sweet vernal-based pastures and there is less tendency for accumulation of stem and dead material in the summer with the higher fertility grasses. In addition the stem and seed head of ryegrass is more digestible than that of the lower fertility grasses. The growth pattern of ryegrass is more even and shows less of a peak than the lower fertility species. Maintenance of pasture quality over the summer/autumn period is best achieved by keeping pastures between 2000 to 3000kg DM/ha within a day grazing rotation. When pre-grazing pasture levels start to exceed 3000kgDM/ha, paddocks should be dropped out of the rotation (preferably the easy contoured paddocks on the farm). These paddocks can be harvested for hay or silage or grazed by cows or other low priority stock in the January/February period. This ensures that the steeper land on the farm is controlled. This is important because pasture and stock performance suffers most, if pasture control is lost on the steep land. Pasture quality is not easily or quickly regained on steep country. In addition, repeated loss of control on steep land encourages reversion to scrubby, woody weeds. 70 CHAPTER 6 Optimising Beef Production from Pasture

11 Set stocking during periods of rapid pasture growth is one method of maintaining better pasture control because it maximises the opportunity for the animals to eat all the pasture that is placed in front of them. The key to successful set stocking is to choose the appropriate stocking rate for that stock class. Mixing of stock classes can be useful in this situation: For example, rotating older cattle or cows through set stocked ewes and lambs. Topping and conservation of pastures. Mechanical topping is an effective, though inefficient way of reducing the development of stem in pastures in the spring. It results in the total loss through decay of topped pasture. Chemical topping, using low rates of glyphosate herbicide (200ml/ha), is potentially another way of reducing reproductive growth of grasses. However, some beef markets may regard annual blanket application of herbicide to pastures as undesirable in future. It also entails some risk as incorrect application beyond fairly fine tolerance margins can result in significant destruction of pasture. Conservation of surplus pasture early in the season (November), can be a potent and effective tool for maintaining pasture quality. The objective is to increase stocking rates in spring, on paddocks that cannot be harvested mechanically, by shutting up easy contour areas for silage or hay. If timed right, these paddocks come back into the grazing round as growth rates slow down a little from the spring flush. Many farmers find this timing difficult to manage, with paddocks not coming back into the grazing round soon enough. Subdivision is a very effective tool for maintaining pasture quality and grazing control. Intensive subdivision reduces the opportunity for animals to only graze favoured areas of a paddock. Recent advances in electric fencing technology have enabled high levels of subdivision to be achieved at relatively low cost. Integration of stock classes is an effective way of maintaining pasture quality in the spring/summer period. Lax grazing high quality pasture with growing cattle, which allows them to select the best quality feed to maintain high liveweight gain, means that residual feed quality can be lower, particularly later in the season if not removed. A lower priority stock class, such as breeding cows or older growing cattle, therefore, is an essential complement to a successful beef finishing system, especially where removal of pasture surpluses as hay or silage is not a practical option. However, in recent years, an increase in the proportion of highprofit finishing cattle has placed added pressure on the availability of low CHAPTER 6 Optimising Beef Production from Pasture 71

12 priority stock classes like breeding cows for cleaning up pasture. Most gross margin budgeting systems fail to take into account the value of pasture management from animals such as breeding cows, mainly because of the difficulty in ascertaining the exact value of these animals in this pasture management situation. Without doubt cows can play an extremely valuable role in removing poor quality feed. They can maintain good calf growth rates while removing feed that other animals will not eat. Adjusting seasonal stocking rates (see comments above also) is critical for successfully managing pasture quality and feed quantity. Adjustments, especially in spring can be achieved by buying, selling, taking on grazers, or grazing stock off, manipulating lambing, calving and weaning dates and increasing the proportion of high fecundity ewes. A flexible slaughter policy allows target liveweights of replacement younger calves to be met through the summer-autumn period by reducing the total feed demand. The flexibility to slaughter older animals when required, depends in turn on earlier target liveweights being met. For example, if 16 month old cattle are grown so that a significant percentage weigh 440kg or greater in early summer, flexibility exists to slaughter these animals, or to retain them to higher weights should summer pasture production be high. A carefully planned slaughter pattern over the summer-autumn period is important to ensure that the required pasture cover on the farm is achieved at the start of winter. Strict decision rules for stock disposal timing need to be in place. This is to ensure that only animals to be wintered are on the property, with no carryover animals remaining to be finished over the winter period when pasture is in short supply and costly (Table 2, Chapter 13). Nitrogen fertiliser almost always provides high quality pasture although its effects are often short term. Applied at the wrong time of the year (for example mid-spring) it could actually reduce pasture quality by increasing the pasture surplus on the farm. However, it is a most effective supplement and one of the cheapest available. At approximately 10 cents/kg DM and provided growing conditions are favourable, nitrogen is a most effective supplement in times of shortage, although its need has to be anticipated and planned several weeks in advance of using it. Nitrogen application, usually in the form of urea, is a grossly underutilised, profitable and effective supplement for many beef finishing systems, particularly over the late autumn, winter and early spring periods. Lack of significant nitrogen use on many beef finishing 72 CHAPTER 6 Optimising Beef Production from Pasture

13 properties remains one of the great mysteries of the modern beeffarming world. Up to 150 to 200kg nitrogen/hectare/year may be applied without unacceptable environmental impact (Chapter 10). Optimum use involves several applications at strategic times, at the rate of 30 to 50kg nitrogen/ hectare each time, to ensure a maximum pasture growth rate response is achieved. Regrassing and the use of forage crops can be a way of ensuring availability of high quality feed for young stock in the summer, autumn or winter periods. New pastures generally have less dead material than the pastures replaced, and are also often lower in levels of fungal toxins and parasitic larvae. The most important factors governing the effectiveness of these crops and new pastures are the success with which they are established, and the cost relative to their benefits. Cropping removes pasture from the grazing rotation in the spring. This can assist in pasture control on the remaining areas of the farm, by effectively increasing farm stocking rate. High-energy supplements or concentrates are an option when it is apparent that feed quality or quantity is insufficient to achieve planned liveweight gains. The increase in liveweight gained from a supplement will be related to the quality of the supplement, for example: Grain supplementation is a reliable means of improving cattle growth rates during summer and winter with a response rate of about 5kg grain/kg liveweight gain (6kg DM/kg liveweight gain). Grass silage will improve cattle growth only if it is of higher quality than the pasture that is offered, or if the animals would otherwise have been severely restricted. Much silage and hay has an ME content of less than 10 MJ/kg DM (frequently less than 8.5 MJ ME). However, it is possible to make high quality grass silage in the right conditions with an ME content greater than This silage can give a response rate of 7kg DM/kg liveweight gain. Use of nitrogen-grown pasture (see above) during the winter has provided a response of 6kg DM/kg liveweight gain and is almost as effective in terms of animal performance as grain. Grain and many other supplements are most effective when used as tactical finishing tools. This is due to the fact that unless the animals are slaughtered when feeding stops, some of the advantages will be lost, compared to animals that were not supplemented, due to the effects of compensatory gain. CHAPTER 6 Optimising Beef Production from Pasture 73

14 Compensatory gain can be a means of helping to align animal requirements with seasonal pasture growth patterns. For example, cattle on restricted feeding during the winter will have higher growth rates during the spring, than cattle that were fed well during the winter. However, for cattle to show this compensation, pasture-feeding levels need to be high during the spring, to enable them to eat the feed necessary to make the extra gain (See Chapter 2 for more details). Winter rotation lengths have proved, under some circumstances, to be of little consequence in terms of final slaughter weights, due to the effects of compensatory growth. In experiments at Whatawhata Research Centre, beef animals on a 40-day winter rotation were heavier at the end of winter than those on a 120-day rotation. However, the 120-day rotation animals had more feed on hand at the end of winter and these animals showed considerable compensatory gain during the spring. By the end of summer, both rotation length groups were of similar weight, indicating that winter rotation length ultimately had little impact (Figure 4). The decision about rotation speed during winter will depend on the balance of pasture supply and demand, and the element of risk that is acceptable with regard to maintaining late winter/early spring pasture covers. The use of a slow rotation during winter reduces this risk. The extent of this feed restriction depends on the need to maintain positive growth over the winter period to achieve targeted marketing times and weights. The choice of winter rotation speed therefore lies in the management of risk and achieving market targets rather than the effect on total system production. Many farmers operate a winter rotation length of days. Figure 4: Average liveweights of steers grazed on either a 40- or 120-day winter rotation followed by a fast rotation (both groups) in the spring. Data extracted from Boom and Sheath (2000). 74 CHAPTER 6 Optimising Beef Production from Pasture

15 Optimum stocking rate Biological efficiency of beef production can be improved by using high stocking rates to improve pasture utilisation. However, as described earlier, increased liveweight gain also increases efficiency because it shortens the production cycle and therefore reduces the total energy cost of maintenance of the animal. High liveweight gain requires high pasture DM intake, which in turn is associated with reduced pasture utilisation and the negative impacts that has on pasture quality at subsequent grazings. The combination of these competing or conflicting forces is that neither very low, nor very high stocking rates can optimise biological efficiency. Data from the long-term bull beef production project of Brougham and Clark at Aorangi Research Station near Palmerston North does provide much assistance in determining optimum stocking rate. Figure 5 shows that optimum liveweight gain/ha/year on that project occurred at about 7 bulls/ha although 5 bulls/ha was also near the optimum. At both 5 and 7.5 bulls/ha, pasture utilisation/year was 95%, whereas at the lowest stocking rate, it was only 67%. Note also, that liveweight gain/head/year declined steadily as stocking rate increased. This was on pastures which produced 15,000kg DM/ha/year; more than on many hill country pastures. Figure 5: The observed relationships of net liveweight gain/ha/year, and liveweight gain/head/year, to stocking rate (bulls/ha) in the bull production trial of Clark (1992). The important question of course, is what is the most profitable stocking rate? Clark (1992) carried out gross margin analyses on the data and derived Figure 6 which showed optimum stocking rate to be about 3.75 bulls/ha in order to maximise gross margin $/ha. The difference between the optimum stocking rate for biological and economic efficiency arose firstly, because the per kg purchase price of the calf is much greater than the selling price, and secondly, because the heavier carcasses generated at lower stocking rates are worth more per unit weight. CHAPTER 6 Optimising Beef Production from Pasture 75

16 The optimum stocking rate for economic efficiency will vary from year to year and between farms depending on: Pasture production. Pastures producing less than the 15,000kg DM/ha/year on the Aorangi project will have to be stocked lower according to their production. Calf purchase price. Beef schedule price and the level of premiums for heavier carcasses. The latter 2 items are critical determinants of optimum gross margin/ha. In Figure 6, the relationship was established for a ratio of calf purchase price ($/kg liveweight) to bull schedule price ($/kg CW) of Figure 6: The predicted relationship of gross margin ($/ha) to stocking rate (bulls/ha) from the bull production trial of Clark (1992). Current estimates are that the ratio is 1.06 for a weaner bull at 100kg worth $350 and a bull schedule price of $3.30/kg. In this case, and with reference to Clark s paper, the optimum stocking rate is still in the range 3-5 bulls/ha, with little variation in profitability over that range. Decisions on which precise stocking rate to use may depend on factors such as: Attitude to risk Labour availability Size of operation Interaction with other enterprises At high stocking rates, financial risk is a major factor because quite small changes in the ratio of calf price to bull schedule price 12 months later, can substantially alter profitability. 76 CHAPTER 6 Optimising Beef Production from Pasture

17 At low stocking rates, financial risks are reduced, but high liveweight gains are required throughout the year, to maximise profitability. Poor pasture quality will place the enterprise at risk. The incomplete utilisation of pasture is a very important factor at low stocking rates and must be carefully managed. Use of supplements to maintain animal performance during pasture deficit periods Aspects of supplementation have been discussed above. Whole books have been devoted to the subject (see Reading List at the end of this chapter), so the following discusses general principles only. Determining the economics of the use of supplements is discussed in Chapter 12. In most cases, supplements are fed with pasture. Quite often the response is poor. Major reasons for this are briefly described below. Wastage In practise, not all of a supplement fed is consumed, particularly when fed on pasture. This results in an over estimate of the amount of feed required to produce a unit increase in production. For example, with paddock fed silage, about 25% of the silage may be wasted. Similar losses are clearly evident when crops are grazed off, or when hay is fed, especially in wet conditions or when pasture is reasonably plentiful. High carcass weight gains relative to live weight gains have occurred in a number of experiments where concentrates or maize silage have been used as the supplement. This is probably because gut fill decreases significantly on a high concentrate diet. Conversely, with bulky feeds such as hay, very good live weight, but disappointing carcass weight gains have been observed. Care is therefore needed in interpreting the value of supplementary feeds in terms of live weight gain alone. Substitution When given supplements, cattle very seldom continue to eat the same amount of pasture as they did prior to receiving the supplement. They reduce consumption of the pasture in favour of the supplement and such substitution can be a major cause of inefficient responses to supplements. On the other hand, such pasture sparing effects of supplements reduce over-grazing, or allow pasture to be saved for consumption later. The rate of substitution depends on a number of factors as described below: The level of feeding of pasture is very important, although little substitution with supplement occurs when feeding is below maintenance. Both the quality of the supplement and the quality of the base pasture ration are likely to affect the level of substitution. Greater substitution CHAPTER 6 Optimising Beef Production from Pasture 77

18 occurs with high quality supplements, and the rate of substitution is often in the range of kg reduction in pasture DM intake/kg of extra supplement DM. In addition, the poorer the quality of the base pasture rations, the higher the likely rate of substitution when animals are being fed above maintenance. Substitution rates of 1 : 1 may well occur. The actual response rates to supplements are very variable. Limited results with growing beef cattle indicate that it frequently takes 4-10kg of supplementary DM to produce an extra 1kg of live weight gain (see earlier comments above also). The responses have been small in many experiments, but when the effects of carcass weight gain of growing cattle and the feed sparing effect through substitution are taken into account, more efficient responses are obtained. In considering the economics of providing supplementary feed, these additional benefits should be allowed for, although they are hard to quantify. As described above, compensatory growth of previously underfed cattle, compared to those fed supplement, can seriously reduce the relative efficiency of responses to a supplement, unless the animals are slaughtered immediately after cessation of supplementary feeding, that is, before compensation has time to take effect. In this respect, supplements may be used as a strategic tool to finish cattle to some price sensitive target weight that could not be achieved by waiting for compensatory gain. Risks of supplementation There are risks to feeding supplements, in addition to those described above of not achieving a profitable outcome due to disappointing responses. These risks apply to the feeding of concentrates, which are energy dense (high ME content/ kg DM) because they contain a relatively high proportion of soluble carbohydrate. Supplements that fall into this category include grains, root crops, maize silage and waste fruit such as kiwifruit. Ingestion of excessive quantities of such readily fermentable carbohydrate by cattle, which have not been adequately adapted to the feed, may cause acidosis, which can be fatal. Ingestion of the feed can cause the production of large quantities of lactic acid leading to digestive disturbances characterised by a rapid fall in rumen ph and loss of appetite. Lactic acid in the blood results in acidosis and dehydration of body tissues. This problem can be avoided, by gradually increasing the proportion of supplement in the diet, by maintaining an adequate proportion of fibrous feeds in the diet, or by use of rumen buffers such as sodium bicarbonate and magnesium oxides. The general recommendation is that levels of concentrate feeding should not exceed 40% of the total diet. 78 CHAPTER 6 Optimising Beef Production from Pasture

19 Other problems such as nitrate poisoning, kale anaemia and reproductive problems, caused by some crops, are relatively rare, but real risks associated with feeding crops, especially when the supplement is not introduced gradually. Refer to a Veterinarian or the reading list at the back of this chapter for more details. Available supplements Available supplements are many and varied. Their availability varies with time of the year, climate and locality. For example, in droughts, supplements are often in short supply and expensive. Early planning helps with these sorts of problems but it can be expensive to have supplements, that in the event, prove not to be needed if, for example, it rains. Storage of supplement is often not always straightforward. Spoilage or wastage due to rodents etc can reduce the value of stored supplement. Appendix I at the back of this book provides a list of commonly available supplements along with their feed values. Knowing the cost of the supplement, it is then fairly straightforward to calculate whether it is worth using it or not (See Chapter 12). Be$tFeed, a computerised feed support system, is designed to assist with making decisions about using supplementary feeds. For more details refer to the end of Chapter 12. Further reading AgResearch In Pasture quality: Principles and management, The Q Graze Manual. A reference document to accompany The Meat New Zealand pasture quality workshops, Published January 2002 Meat New Zealand, PO Box 121, Wellington, pp Anon More profit from brassicas, Issue 3, April 2002, Meat New Zealand, P.O.Box 121, Wellington. Anon Perenial grasses what you need to know. More profit from pastures, Issue 2, November 2001, Meat New Zealand, PO Box 121, Wellington. Anon Using chemical topping to prevent pasture reversion. R & D Brief, March 2000, Meat New Zealand, PO Box 121, Wellington. Boom, C. J Setting and achieving finishing cattle growth paths. In Profitable beef systems. A Northland Beef Council Field Day, May 1999, Meat new Zealand, PO Box 121, Wellington, pp Boom, C. J.; Sheath, G. W The effects of winter rotation speed on the performance of beef finishing systems. Proceedings of the New Zealand Society of Animal Production 60: CHAPTER 6 Optimising Beef Production from Pasture 79

20 Charlton, J. F. L.; Weir, J. H TechnoGrazing a new grazing concept. Proceedings of the New Zealand Grasslands Association 63: Clark, D.G The effect of stocking rate on bull beef production. Massey Dairy Farming Annual 42: Drew, K.R.; Fennessy, P.F. (Editors) Supplementary feeding. A guide to the production and feeding of supplements for sheep and cattle in New Zealand. New Zealand Society of Animal production. Occasional Publication No. 7. Marshall, P.R.; McCall, D.G.; Johns, K.L Stockpol: A decision support model for livestock farms. Proceedings of the New Zealand Grasslands Association. 53: Mathew, C.; Hodgson, J.; Mathews, P.N.P.; Bluett, S Growth of pasture Principles and their application. Massey Dairy Farming Annual 47: McCall, D.G.; Smeaton, D.C.; Gibbison, M.L.; McKay, F.J.; Hockey, H.U.P The influence of sheep to cattle ratios on live-weight gain on pastures grazed to different levels in late spring-summer. Proceedings of the New Zealand Society of Animal Production 46: Nicol, A.M.; Kitessa, S.M Compensatory growth in cattle revised! Proceedings of the New Zealand Society of Animal Production. 55: Ogle, G.; Tither, P An analysis of the risks and benefits of beef intensification. Proceedings of the New Zealand Grasslands Association 62: Rollo, M.D.; McCall, D.G.; Boom, C.J.; Sheath, G.W Evaluation of a beef growth model for use in beef finishing decisions. Proceedings of the New Zealand Grasslands Association. 57: Sheath, G. W The grass factory the foundation for efficient/profitable beef production. Proceedings of the beef finishing and marketing conference, New Zealand Beef Council, Meat New Zealand, PO Box 121 Wellington. Sheath, G. W.; McCall, D. G Finishing systems for beef cattle. Proceedings of the 24 th Seminar of the Sheep and Beef Society, New Zealand Veterinary Association. Publication No. 159, pp CHAPTER 6 Optimising Beef Production from Pasture