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C.F.M. De Lange1 And S.K. Baidoo2
The ultimate goal in commercial pork production is to efficiently produce a high quality pork. Efficiency in pork production is closely related to profitability, i.e. to maximizing the difference between the value of the output (carcass and meat quality) and costs of production (feed, capital, labour, services)
In this article some of the feeding and management factors that determine the efficiency of pork production will be addressed.
Main factors Affecting Efficiency of Pork Production
Lean Growth Rates and Potentials Lean growth, or lean meat deposition, represents the gain of the valuable parts in the pig's body. Due to the high water and low fat content (as compared to that in fat tissue), it is energetically approximately 4 times more efficient to produce 1 kg of lean meat than 1 kg of fat tissue. Lean growth rate in grower-finisher pigs is thus closely related to live weight gain, carcass quality and feed efficiency. In addition, lean growth rate is the single most important factor that determines the daily requirements for amino acids (protein and one of the main factors determining the requirements for energy in grower-finisher pigs. Energy and protein contribute to more than 85% of the ingredient cost in practical pig diets.
The expected performance of pigs with high, medium or unimproved maximum lean growth rates, and consuming average quantities of feed, are presented in Table 1. The difference in gross margin per pig between the two extremes will be close to $6 per pig. In order to maximize profitability it is important to achieve high lean growth rates in pigs and to closely monitor lean growth rates in individual units.
Table 1. Estimated performance of growing pigs (25 to 105 kg) with high, medium, or unimproved lean growth potentials*
|Lean growth potential||High||Medium||Unimproved|
|Average daily gain (g/d)||834||785||728|
|Feed: gain (g/g)||2.98||3.17||3.41|
|Dressing percentage (96)||79.4||79.8||80.3|
|Lean yield (%)**||60.6||58.7||57.0|
|Carcass index (%)||109||107||104.5|
* Diets contain 3150 kcal DE/kg and optimum levels of amino acids and other nutrients; feed intake is 90% of voluntary intake according to NRC (1988). A feed wastage of 3% is included.
** % of cold carcass weight, 1995 grading system.
Lean growth potentials of pigs are largely determined by genotype and sex (see also Table 3). For various reasons actual lean growth rates may be lower than the animal's potential. Pigs may not show their potential when energy intake is limited, insufficient amino acids or other nutrients are supplied, or if the environmental conditions are less than optimal. Furthermore, some recent studies have demonstrated that the presence of disease can significantly reduce lean growth rates in pigs (e.g. Williams et al, 1993; Dionissopoulos et al., University of Guelph, unpublished: Table 2). The data in Table 2 clearly illustrate the negative effects of SEW systems on lean growth potentials when newly weaned piglets from a large number of sow herds are mixed when moved into the SEW nursery.
Table 2. Growth performance and carcass lean yield in the three groups of pigs with a similar genetic background, managed under similar conditions between 25 kg body weight and market weight, and fed high quality diets. The pigs were derived from different commercial units.*
Management during rearing/health status
Body weight, kg.
|Feed intake**, kgld||2.24||2.22||1.92|
|Carcass weight, kg||85.4||86.4||85.5|
|Carcass lean yield, %||61.8||61.1||62.0|
|Lean gain, kg/d***||.43||.42||.35|
* High health status (specific pathogen free; SPF), Conventional health status, or from a segregated early weaning system were piglets from six different herds were weaned and mixed in a common SEW nursery.
** These data include performance of all pigs, including the pigs that were removed from the trial before they reached market weight, and on a per pen basis. Gain and feed:gain are statistically corrected for differences in initial body weight between the three groups.
*** calculated based on determined lean yields in the cold carcass sides (grading probe), an assumed difference of 8 kg between hot carcass weight and weight of cold carcass sides, and a lean content of 35% of initial body weight.
**** calculated as lean gain / 2.5.
Finally, it is important to consider how lean growth rates change with changing body weight; i.e. to establish lean growth curves rather than average lean growth rates over large body weight ranges. The latter is extremely important for determining the optimum shipping weight for the various pig (geno-) types (see also determining the optimum shipping weight later in this paper)
The Important of Feed Intake Feed intake is closely related to growth rate, feed conversion, carcass value and thus profitability. Estimates of feed intake are also important for nutritionists to determine the optimum level of nutrients in the diet once the daily nutrient requirements are established. Since feed intake varies largely between different farms and with the season, feed intake and the main factors that affect feed intake should be closely monitored. As we continue to further fine-tune feeding programs (split-sex feeding, phase feeding, feeding to genetic potential) it becomes more critical to obtain estimates of feed intake at the various stages of production, i.e. to establish a feed intake curve. Typical feed intakes (90% of voluntary feed intake according to NRC, 1988; diet DE content 3150 Kcal/kg) are summarized in Table 3.
Table 3. Marginal and cumulative performance of growing pigs from 20 to 110 kg live body weight*.
Body Weight (kg)
Average Daily Gain (g/d)
* Feed intake is average of what can be expected under commercial conditions (90% of NRC, 1988; NOT FEED WASTAGE); dietary DE is 3150 kcal/kg; growth follows the Gompertz function.
In growing pigs, up to approximately 50 kg live body weight, energy intake generally limits lean growth. In these pigs the daily energy intake should be maximized. Finishing pigs, especially those with medium or unimproved lean growth potentials and consuming large quantities of feed, consume more energy than what is required for maximum lean growth. In these pigs excessive body fat is deposited and as a result, carcass value is reduced. In finishing pigs with unimproved or average lean growth potentials, carcass value and feed efficiency can be improved by restricting the daily energy intake. It should be pointed out that as lean growth potentials continue to improve, energy intake is likely to determine lean growth rates up to higher body weights. The body weight at which pigs change from a grower pig, where limits lean growth, to a finisher pigs, where energy intake no longer limits lean growth, remains to be determined for the various modern pig genotypes. At least three recent studies suggest that energy intake limits lean growth up to about 80 to 90 kg body weight in specific modern pig genotypes.
Factors Affecting Feed Intake Feed intake is affected by a whole range of factors, associated with the animal (body weight, sex, genotype, health) the feed (energy density, large nutrient imbalances, freshness, presence of toxins, processing) and the environment (effective environmental temperature, pig density, feeder design location and management, quality and available of water, etc.) (NRC, 1987). It is beyond this article to discuss these factors in detail. However, it is important to monitor the main factors that affect feed intake: effective environmental temperature, health (Table 2), feeder design and management, genetics and feed quality. These observations can be used to explain why feed intake is different from standard feed intake curves on individual production units Table 3; Swine Nutrition Guide, 1995).
An important point to consider is the environmental temperature. When pigs are kept dry and in a draft free environment, the room temperature should be maintained at approximately 18 - 20°C when pigs first enter the grower barn at approximately 25 kg body weight); it can be gradually decreased to approximately 14°C as pigs are approaching market weight (ASAE, 1991). Too often the room temperature is maintained too high for finishing pigs. As a result feed intake will be reduced substantially. Per 1°C increase in environmental temperature feed intake will reduce by approximately 2% in weight. It is clear that compromizes need to be made in choosing the environmental temperature when pigs at different stages of growth are all kept in one common airspace.
A study at Purdue University clearly demonstrates the large effects of pig genotype and sex on voluntary feed intake (Schinckel, 1994; Table 4). In feeder pigs managed under the same conditions and fed similar diets, observed difference in feed intake between the various lines of pigs were as high as 20-30%. Pigs that have been selected for (lean) feed efficiency, rather than for lean growth rates, may have lower feed intake capacities as compared to the unselected controls. The results also indicate that the difference in feed intake - between barrows and gilts is not the same for all genotypes: for genotype 7 it was 12% while for genotype 9 it was only 3%. This clearly demonstrates that it is too simple to assume that there is one specific feed intake curve that can be used as a target intake curve for the different types of pigs and pig production units.
Table 4. Feed intake and other performance traits in a sample of pig genotypes (Schinckel, 1994)*.
|Feed Intake (kg/d)||Weight Gain (kg/d)||Lean Gain (g/d)||Fat gain (g/d)||Fat gain per 100 g of lean gain|
* 25-117 kg body, weight; pigs were fed four diets, 3.48Mcal ME/kg, 1.3, 1.15, 1.05 and .95 lysine; lean gain is fat-free lean gain, fat gain is total lipid in the soft-carcass tissue.
Developing Feeding Programs
It is important to develop a feeding program where the animal's requirements for nutrients (energy, amino acids, vitamins and minerals) are closely met for two reasons. First, underfeeding of nutrients will reduce animal performance, carcass value and profitability. Second, overfeeding will unnecessarily increase feeding cost and will not result in any improvement in animal performance. Diets should thus be formulated to meet the unique requirements of various groups of pigs managed under various conditions. The following points should be considered when feeding programs are developed.
For the most expensive (energy, amino acids) some general recommendations can be made.
Optimum Energy Density
In finishing pigs there is no clear relationship between dietary energy density and daily energy intake. If the energy density in the diet is reduce, finishing pigs simple eat more feed to achieve a constant daily energy intake. For the finishing diet it is thus important to determine the dietary energy density at which the cost per unit of available energy, balanced with other nutrients, is the lowest. This can be achieved by (least-cost) formulating diets with varying energy densities while the ratio of all other nutrients (amino acids, vitamins and minerals) to energy is maintained constant in each of these diets. For the various diets the cost per unit of energy (balanced with all other nutrients) is then calculated by dividing diet cost (ingredient cost and the cost of feed handling and preparation) by the energy densities in the various diets.
For growing pigs, where "gut fill" generally limits energy intake and lean growth, the daily energy intake increases as the energy density in the diet increases. In the grower diet, the optimum energy density is thus not only determined by the cost per unit of available energy balanced with the other nutrients, but also by the value of improvements in lean growth rate and throughput.
Suggested Dietary Levels of Available Lysine In practical swine diets, lysine is the first limiting amino acid. Available lysine requirements are primarily affected by the animals' lean growth rate and body weight. Since lean growth rates are relatively constant and feed intake increases as pigs grow heavier, the dietary levels of available lysine and other nutrients can be reduced as animals approach market weight. The largest advantage of using different diets that vary in nutrient levels (known as phase feeding) is that the changing nutrient requirements can be accurately met while no expensive nutrients are wasted as animals grow heavier.
The suggested dietary levels of available lysine in relation to bodyweight and lean growth rates are presented in Table 4. These levels indicate the suggested available lysine to DE ratio in diets for growing pigs, where energy intake limits lean growth, and the suggested daily intakes for finishing pigs when energy intake does not limit lean growth. These recommendations are independent of feed intake. However, in order to use this information in feed formulation, the dietary energy density in the grower diets and the actual feed consumption on the finisher diets should be known. The values in parenthesis are the available lysine levels in diets with average nutrient densities and on average feed intakes (Table 3).
Table 5. Suggested daily average (apparent ideal digestible) lysine allowances (% of the diet) for growing pigs in relation to lean growth rate and live body weight.
Live Body Weight (kg)
|Lean growth rate||25||45||60||70|
|High||2.70 g/Mcal DE (.86%)*||2.35 g/Mcal DE (.74%)*||20.0 g/d (.67%)*|
|Medium||2.25 g/Mcal DE (.71%)*||17.5 g/d (.61%)*|
|Unimproved||1.95 g/Mcal De (.61%)*||15.5 g/d (.54%)*|
* Level in a practical diet (3150 Kcal DE/kg), feed intake levels are similar to the average feed intake observed on commercial farms (90% of NRC, 1988; Table 3). If observed dietary energy densities or observed levels of feed intake differ, then dietary available lysine levels should be adjusted to ensure a constant available lysine to DE ratio (g LYS/Mcal DE) when energy intake limits lean growth growing pigs) or a constant daily lysine intake (g LYS/d) when energy intake does not limit lean growth (finishing pigs). Adjusted from: Swine Nutrition Guide (1995)
If only one grower-finisher feed is used, it is too expensive to feed a diet that will meet the amino acid requirements for pigs in the early growth stages. Some performance in the early growth stages should be sacrificed to optimize profitability if no phase feeding program is applied.
Suggested Levels of Other Amino Acids: Ideal Protein Once the requirements for available lysine are established, the requirements of other essential amino acids can be determined using the concept of ideal protein. The amino acid composition of ideal protein represents the balance in which amino acids are required by pigs. It can be estimated that per 100 g of available lysine, growing pigs require approximately 60-65 g of available threonine, 58-63 g of available methionine plus cystine and 18-20 g of available tryptophan. The ratio of these amino acids to lysine increases as animals grow heavier or with reduction in lean growth potentials. At least 53% of the dietary methionine plus cystine needs to be supplied by methionine. It should be noted that these optimum ratios will differ when diets are formulated based on total, rather than digestible, amino acid contents in the feed ingredients. For example, due to differences in digestibilities, the optimum threonine to lysine ratio is higher when based on total amino acid levels than when based on digestible amino acid levels. The amino acid composition of ideal protein also determine the maximum amount of synthetic lysine (Lysine.HC1, 79% lysine) that you can add to a practical diet. If, as a result of adding synthetic lysine to a diet, another amino acid becomes first limiting (threonine, tryptophan, methionine) and any further additions of synthetic lysine to the diet will not further enhance performance; it will only increase feed cost.
Practical Performance Monitoring
What And How To Monitor In order to get a better understanding of current levels of performance and to identify means to improve performance in growing-finishing pigs, performance should be closely monitored. Important aspects of performance include:
The information concerning carcass weights and carcass index can be obtained relatively easily from the grading slips. It is generally more difficult to obtain estimates of growth rate and feed usage. These can be obtained using two approaches:
INSERT FIGURE 1
Practical Management That Can Be Addressed When Performance is Monitored
Feed Intake Management The important of feed intake and the main factors that determine feed intake were discussed previously.
Lean Growth Management When carcass information (average lean yield) is combined with growth rates, lean growth rates can be calculated. For calculating average lean growth rates, between the weight at which pigs enter the barn (approximately 25 kg body weight) and market weight, it can be assumed that the lean meat content in pigs at approximately 25 kg body weight is relatively constant at 35% of body weight. In the current carcass grading grid, lean yield is expressed as a percentage of sides of the cold carcass. The difference in weight between the cold and dressed warm carcass is approximately 8 kg. This weight difference should be considered when calculating the lean content at the final body weight. Lean yield at the final weight is lean yield % x (warm dressed carcass weight - 8) (Uttar-o et al, 1995). Lean growth rates can then be calculated as (kg. Lean at final weight - kg lean at initial weight) / (number of days to grow from initial to final weight).
The average lean growth rates in groups of growing-finishing pigs can be estimated quickly from observed growth rates and carcass lean yields (Table 6).
Table 6. Relationships between lean growth rate, average daily gain and carcass lean yield in growing pigs (25 to 105 kg live weight)*.
|Carcass lean yield, %**||Growth rate (g/d), between 25 and 105 kg body weight|
|59 - 61||High||High||Medium||Medium||Unimpr.|
|57 - 59||High||Medium||Medium||Unimpr.||Unimpr.|
|* The maximum protein deposition rates are 150, 130 and 110 grams per day in the high, medium and unimproved lean growth rates respectively.|
*** % of cold carcass weight, 1995 carcass grading system.
The actual growth curves will allow producers to identify the specific areas where the largest potential improvements can be made to improve overall growth rates. For example, this information can be used to determine when pigs should be moved or when overcrowding likely occurs. Estimates of both feed intake and growth are required to establish the feed : gain ratio (FCR).
The actual growth rates and FCR for pigs with an average growth rate of 750 g/d and at average levels of feed intake are presented in Table 3. The marginal gains and FCR represent the gains and FCR within the 5 kg body weight ranges and the cumulative gains and FCR represent the gains and FCR from 20 kg body weight.
An important parameter that determines throughput in the G/F barn in the amount of variation in growth rate within groups of pigs. For calculating the total number of days per rotation (or the number of days between starting subsequent lots of pigs), the average and variation in growth rate as well as time required to clean pens between lots of pigs needs to be considered. A simple means to quantify this variation in growth is to determine the number of open days per rotation. This number is defined as the difference between days per rotation and the number of days to market for the average pig in that lot. If, for example, pigs from a pen take on average 100 days to reach market weight and they are shipped over a 4 week period, the first pigs will be shipped at 86 days (100-14) and the last pigs will be shipped at 114 days. If not time is required to clean the pen, the number of open days per rotation is 14 (114-100). In other words, the pen is used at approximately half is capacity over a 28 day period and 14 open days are collected per pig place and per rotation. The effect of reducing the number of open days per rotation on gross margin per pig place per year for a facility with unlimited access to weaner pigs is summarized in Table 7.
Table 7. Estimated effect of a reduction in the number of open days per rotation on financial performance.
|Number of open day per rotation||21||14|
|Days to market||98||98|
|Days per rotation||119||112|
|Number of rotations per year||3.067||3.259|
|Cross margin ($/pig)||30.22||30.22|
|Gross margin ($/pig place/year)||92.69||98.48|
* Animal performance and prices are as Table 6, alternative 1.
Management practices that should be considered in reducing the number of open days per rotation are:
For example, in a G/F facility where space is limiting (the objective is to maximize profit per pig place per year rather than to maximize profit per pig), approximately half of the financial advantage of split-sex feeding results from a reduction in open days on pig places. Since barrows grow faster than gilts, the barrow pens can be turned over more quickly than gilt pens. That is, fewer barrow pens are required than gilt pens in order to produce the same number of pigs of each sex.
Determining the Optimum Shipping Weight
When feed intake and growth curves are established the marginal production costs as animals approach market weight can be determined. The relationship between carcass weight and carcass index can be derived from the receipts from the marketing board. Utilizing this information you can quickly evaluate the effect of varying the shipping weight on the gross margin per pig and the gross margin per pig place per year. Various alternative shipping weights can be evaluated based on the average carcass index that corresponds to the projected carcass weight and the costs to produce market pigs up to these various weights. It can generally be assumed that dressing percentage is not significantly affected by body weight at shipment.
In Table 8, the effect of various shipping weights on gross margin per pig and gross margin per pig place per year are presented for the pigs at Prairie Swine Centre Inc. (PSCI). By increasing the average shipping weights from 103.5 to 108 kg, the estimated gross margin per pig was increased by more than $2.00/pig. At the PSCI it makes more sense to ship heavier (carcass weights over 87 kg) rather than lighter (carcass weights below 80 kg) (Table 8). It should be noted that these calculations relate to the carcass grading grid in Saskatchewan. However, calculations can be quickly repeated for different farms and for different carcass grading system.
Table 8. The effect of shipping weight on animal and financial performance in PSCI gilts and barrows*.
|Carcass weight range (kg)||75-80||80-83.5||83.5-87||87-90|
|Final body weight (kg)||98.10||103.48||107.91||88.5|
|Carcass weight (kg)||77.50||81.75||85.25||105.15|
|Carcass index (kg)||106.42||107.26||107.41||107|
|Days to market||89||95||101||3.17|
|Rotations per year||3.54||3.35||2.83||3.02|
|Feed : Gain||2.72||2.78||119.04||2.88|
|Carcass Value ($/pig)||107.22||113.99||40.35||120.98|
|Feed cost ($/pig)||34.17||37.48||21.68||43.16|
|Gross margin ($/pig)||16.05||19.51||68.79||20.82|
|Gross margin ($/place/year)||57.11||65.14||112.03||63.05|
|* Based on feed intake and growth curves for PSCI pigs; initial weight is 25 kg; 14 open days per rotation; carcass index (average of gilts and barrows) at the various carcass weights are derived from sales receipts; weaner pig price is $45/pig; variable costs are $12/pig; feed cost is $172/tonne; pork price is $1.30/kg; GrowthMaster.|
It should be noted that in these calculations not only the average, but also variation in carcass weight should be considered. Typically, the standard deviation in carcass weight is about 4 kg. This means that at an average carcass weight of 85 kg, typically 66% of the carcasses will be between 81 and 89 kg body weight. However, the amount of variation on carcass weights will differ considerably between farms. In most Canadian carcass grading systems the penalty for shipping pigs too heavy is larger than shipping these too light. This implies that, if the variation in carcass weight is minimized the optimum shipping weight can be increased. In that case, most carcasses will be within the core of the grading grid, and there will be few carcasses that are (too) heavy. If the variation in carcass weight is high, then producers should reduce the average shipping weight in order to maintain most of the carcass weights within the core. The combined effects of average carcass weights and variation in carcass weight on the optimum shipping strategy can be evaluated for individual pork production unit using PorkMaster, the new computerized performance monitoring system developed at the University of Guelph.
Fine-tuning the Feeding Program As described previously, estimate of the animals' lean growth potential and feed intake at various stages of production are important for developing cost-effective feeding programs. Given the lean growth rate and observed feed intakes, the optimum level of available lysine and other amino acids in the various diets can be established. When this approach was used to develop a phase and split-sex feeding program for the pigs at PSCI, the improvements in financial performance were more than $15 per pig place per year as compared to a one-phase feeding program where the sexes were not fed separately (de Lange et al., 1994).
The "cost" of using incorrect estimates of feed intake to estimate the optimum available amino acid levels in the diet can be substantial. If feed intake is approximately 10% less than what is assumed when the optimum dietary amino acid levels were determined, then gross margin per pig place per year is reduced by close to $10 in a two-phase feeding program. However, when adjustments are made to the feed (increase in the amino acid levels in the finishing diet) to overcome the difference between actual and assumed levels of feed intake, the gross margin per pig place per year can be improved by close to $4 (Table 10).
Table 10. Estimated effect of feed intake and dietary amino acid levels on animal and financial performance in pigs with better than average lean growth potentials (Western Canadian Conditions: Swine Nutrition Guide, 1995).
|Level of feed intake||90% of NRC||80% of NRC||80% of NRC|
|Feeding program||Optimum||Optimum; adjusted for lower intake||sub-optimal; as for I|
|Feed : Gain||2.97||2.88||2.94|
|Cross margin * ($/pig)||30.22||31.42||30.70|
|Gross margin ($/place/year)||98.50||92.50||89.00|
|# Canadian carcass grading system; carcass index is a reflection of carcass lean yield and carcass weight. It used to derive the payments per kg of carcass to producers.|
* Cross margin is calculated as carcass value [bid price ($/kg carcass) x (index / 100) x carcass weight] minus feed costs and variable costs per pig.
Profitability in commercial pork production is determined by many factors. Ideally on-farm parameters should be established to determine the feeding strategies that optimize carcass quality and profitability in individual situations. Some general recommendations can be made based on observed lean growth rates and levels of feed intake. Producers should closely monitor performance to identify opportunities to improve performance and to ensure that changes in feeding recommendations result in expected changes in performance.
de Lange, C.F.M., B. Piwarski and D. Gilles. 1994. Please and split-sex feeding of growing-finishing pigs. 1994 Annual research report. Prairie Swine Centre Inc. P.O. Box 21057,2105 8th Street East, Saskatoon, SK S7H 5N9. pp. 26-29
de Lange, C.F.M., B.J. Marty and B. Szkotnicki. 1995. Modelling as an aid to nutritional management. In: Advances in Pork Production (ed. G. Foxcroft). Department of Animal Science, University of Alberta (these proceedings.)
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National Research Council (NCR). 1988. Nutrient requirements of swine. National Academy Press, Washington, D.C.
Patience, J.F., P.A. Thacker and C.F.M. de Lange. 1995. Swine Nutrition Guide 2nd Ed. Prairie Swine Centre Inc. P.O. Box 21057,2105 8th Street East, Saskatoon, SK S7H 5N9.
Schinckel, A.P. 1994. Nutrient requirements for modern pig genotypes. In (Garnsworthy, P.J. and D.J.A. Cole, Ed.): Recent advances in animal nutrition. Univ. Of Nottingham press, Nottingham, U.K. pp. 133-169
Uttaro, B.E., R.O. Ball and C. Vandervoort. 1995. A comparison of the former and present destron probe lean yield equations with the dissected lean yield of Ontario purebred hogs. Ontario Swine Research Report. pp. 25-28
Williams, N.H., T. Stahly and D.R. Zimmerman. 1993. Impact of immune system activation and dietary amino acid regimen on nitrogen retention in pigs. J. Amim. Sci. (abstract) 71: 171.