Growing-Finishing Swine Nutrient Recommendations and Feeding Management

Profitability of commercial swine enterprises is affected by a variety of factors, such as the pigs genetic potential, environment, feed intake, ingredient availability and market prices. Each of these factors needs to be considered in designing the most optimal and profitable feeding and management system. The final feeding and management strategy implemented may be different for each individual production unit and will also vary with changing environmental and economical conditions. The challenge to the producer is to manage all variables in such a way that productivity and profitability are optimized. Feed represents approximately 65 to 75% of the total cost of producing pork and approximately 75% of this amount is fed in the grow-finish phase of production. Close attention is needed to develop a nutrition and feeding management program to increase the potential for profitability.

 

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Objectives

 

The objectives of this paper are to review factors that influence the nutrient requirements and nutrient recommendations for finishing pigs of different body weight and lean gain potential, and to discuss practical feeding strategies.

 

Lean Gain Potential

 

The maximum lean gain potential of the pig needs to be known to set the upper limit of daily amino acid and energy requirements for that pig. A tremendous amount of variation exists in the maximum lean gain capacity of pigs, which is related to their genetic potential, gender, nutrient availability, intake, environment and health status. If all management, environmental and nutritional factors were ideal, the maximum lean gain capacity of the pig could be reached. However, under practical conditions some factors will limit lean gain to some extent resulting in suboptimal lean gain.

 

 

The amount of lean a pig deposits depends on it’s stage of growth. Lean gain deposition increases as pigs advance in body weight up to approximately 125-140 lbs, after which it decreases (Figure 1). In contrast, fat deposition increases as pigs age, which occurs at an even faster rate as pigs reach maturity. Differences in rate of gain and composition of gain also exist between barrows and gilts. Barrows grow at a faster rate than gilts, but tend to be less lean. Knowing the amount of lean a pig deposits sets the daily requirements for amino acids, which follow the same pattern as lean gain.

 

Determining Lean Gain

 

Lean tissue is composed of approximately 76% water, 20% protein, and 4% lipid. Standardized fat free lean is often used to indicate the % lean in the carcass. Packing plants may have their own equations to calculate % lean and will indicate this on the carcass grading grid. Percent lean is commonly calculated from measurements of back fat, loin eye area or loin depth and yield using one of the equations below. How and where these measurements were taken and what information is available to you will dictate which equation to use for calculating lean.

 

Equations to use for calculating the amount of standardized fat-free lean (SFFL) in the carcass (in lbs) can be summarized as follows [1]:

1. For ribbed carcasses using 10th rib back fat thickness and loin eye area
   SFFL (lbs) = 8.588 + (0.465 x hot carcass weight, lbs)
   – (21.896 x 10^th rib fat depth, in.)
   
   + (3.005 x 10^th rib loin muscle area, in²)
2. For unribbed carcasses using a ruler to measure back fat thickness at the last rib
   SFFL (lbs) = 23.568 + (0.503 x hot carcass weight, lbs)
   – (21.348 x last rib fat depth, in.)
3. For carcasses using a Fat-O-Meter to measure fat thickness and loin muscle depth
   SFFL (lbs) = 15.31 + (0.51 x hot carcass weight, lbs)
   – (31.277 x fat depth, in.) + (3.813 x loin muscle depth, in.)
4. For live pigs using Ultrasound and measuring 10th rib back fat thickness and loin muscle area
   SFFL (lbs) = -0.534 + (0.291 x live weight, lbs)
   – (16.498 x 10^th rib fat depth, in.)
   + (5.425 x 10^th rib loin muscle area, in²)
   + (0.833 x sex of the pig, where barrow=1 and gilt=2)

 

The percentage of lean in the carcass can be calculated by dividing the lbs of SFFL from the equations above by carcass weight and then multiplying it by 100. A theoretical value of 74 for yield can be assumed if carcass weight is not known to calculate carcass weight as 0.74 x live body weight.

 

Lean gain (lbs/day) can be calculated as follows:
[lb. of lean in carcass – lb. of lean in feeder pig]/days on test

 

To calculate the amount of lean in the carcass, use the appropriate equation described previously. The pounds of lean in a feeder pig can be estimated from the following equation [2]:

lb. of lean in feeder pig = (0.418 * live weight, lb.) – 3.650

 

Table 1 shows calculated daily lean gain for a variety of fat-free lean percentages and days to market scenarios and can serve as a guideline. For example, a pig slaughtered at 260 lbs with a carcass yield of 74% and a fat-free lean percentage of 54% would produce a total of 260 x 0.74 x 0.54 = 103.9 lbs of lean. At a starting weight of 50 lbs, the amount of lean at the beginning of the feeding period would have been 0.418 x 50 – 3.650 = 17.25 lbs of lean. Thus, the pig in this example deposited a total of 103.9 – 17.25 = 86.6 lbs of lean during the finishing period. If it took 120 days from 50 to 260 lbs of body weight, then the average daily lean gain in this example would be 86.6/120 = 0.72 lbs per day. In general terms, pigs with more than 0.80 lbs of lean gain per day can be classified as high lean gain pigs. Pigs gaining between 0.65 to 0.80 lbs of lean per day constitute medium lean gain pigs and pigs gaining less than 0.65 lbs of lean gain can be considered as low lean gain pigs.

 

Table 1. Daily lean gain calculated from a range of fat-free lean percentages and days to market assuming a starting weight of 50 lbs, a final weight of 260 lbs, and a carcass yield of 74%.

 

Feed intake

 

Feed intake can be either measured or predicted. When feed intake is measured at different weight ranges, on- farm feed intake curves can be developed. The limitation of such an approach is that prediction of future feed intake is completely dependent on the conditions under which the initial measurements were made. When feed intake is measured, it is generally measured by determining the amount of feed that disappears, which does not compensate for feed wastage. The amount of feed a pig wastes can be significant and highly variable depending on feeder type and management. Prediction of feed intake is difficult, because feed intake is affected by a large number of factors. For example, energy density of the diet will impact feed intake. Generally speaking, increasing the energy density of diets decreases feed intake, whereas lowering energy density increases feed intake. Genotype of the pig also influences feed intake. Pigs selected for improved lean gain potential will consume more feed in order to accomplish the improvement in lean gain. Pigs selected for improved lean efficiency (lean gain per unit of feed intake) tend to eat less and have a lower overall daily gain, because selection emphasizes carcass lean and feed efficiency [3]. Environmental factors, such as floor space allowance, temperature, and disease (or health) status have a great impact on feed intake. Feed intake curves that illustrate the relationship between feed intake and body weight can be developed for different genetics and different sexes under ideal conditions. A suggested feed intake pattern for growing-finishing pigs housed under superior conditions is shown in Table 2. Adjustments can then be made for each individual farm for one or more environmental factors that may not be ideal, as described below.

 

Table 2. Feed intake guidelines (lbs/day) for gilts and barrows housed under superior conditions

 

Environment

 

Temperature: Pigs have a comfort zone for the environmental temperature that they prefer, referred to as the thermoneutral zone. This comfort zone ranges from approximately 55 °F on the low end to 75 °F on the upper end for finishing pigs. Pigs that are housed below the lower critical temperature (55 °F) will consume more feed to maintain their body temperature. The increase in feed intake is estimated to be approximately 0.03 to 0.05 lbs per °F below 55 °F [4]. Moderately low temperatures will not reduce growth rates, but because of greater feed consumption, feed efficiency will be poorer. If pigs are kept in an environment that is too hot, feed intake will be reduced by approximately 0.05 to 0.08 lbs per °F above 75 °F [4]. Growth rate is expected to decrease in hot environments, approximately 0.03 to 0.04 lbs/d for every °F above 75 °F. The impact of temperature is dependent on the weight of the pig. Heavier pigs are more sensitive to high temperatures than younger, lighter pigs [5], while smaller pigs are more susceptible to heat loss; therefore, lower temperatures have a greater effect on smaller pigs compared to larger pigs.

 

Floor Space: The floor space requirement for pigs depends on their body size, which can be related to body weight. A 240 lb pig has a floor space requirement of approximately 8.3 ft2, whereas a 265 lb pig requires 8.9 ft2 [6]. Lowering the amount of space per pig below the required amount will reduce performance. For each 3% reduction in space, daily gain and daily feed intake will change approximately 1% for pigs raised in fully slatted barns.

 

Pig Health Status: The health status of pigs can have a dramatic effect on pig performance. Although disease status is difficult to measure objectively, a general impression of the health of pigs can usually be obtained by disease profiling the herd using serology. Greater health status may be expected in farms that apply stringent biosecurity, all-in-all out, strict isolation procedures, thorough cleaning between groups of pigs, etc. Pigs exposed to poor health conditions grow slower, consume less feed, have less lean, and have poorer feed conversion than healthy pigs. Poor health status decreased daily gain, feed intake, gain:feed, lean deposition, and feed intake by approximately 23, 10, 15, and 23%, respectively [7]. More specific information on the interaction between health and diet can be found in PIG Factsheet # 07-01-16 (Diet and Health Interactions in Swine).

 

Estimating Nutrient Requirements

 

Amino Acids: When lean growth rates are known, estimates can be made on how much lean and how much fat a pig will produce during a given amount of time or during a certain weight range. Daily amounts of protein (amino acids) and energy required to accommodate these weight gains can then be estimated based on biological relationships that exist in utilizing dietary nutrients for tissue growth. For example, 1 gram of protein contains approximately 0.07 grams of lysine and the efficiency of lysine utilization for protein gain is estimated to be approximately 58% [8]. Therefore, to gain 1 gram of protein, 0.12 grams of digestible lysine is needed. The requirements for other amino acids can be calculated in a similar way. However, in practice, the requirements of other amino acids are expressed as a percentage relative to lysine. Lysine is typically the first and most limiting amino acid in swine diets, which means that it is the first amino acid that needs to be supplemented to meet the requirements of the pig. Expressing the requirement for the other amino acids relative to lysine (ie. lysine is set at 100%) makes it easy to calculate these requirements at any stage of growth. Ratios of other amino acids to lysine are provided in Table 3. As an example, if a high lean gain pig at 60 lbs of body weight requires 1.07% lysine, then its threonine requirement is 0.63 x 1.07 = 0.67%. More detailed information on the establishment and application of amino acid ratios can be found in PIG Factsheet #07-02-03 (Understanding Swine Nutrient Recommendations).

 

The digestibility of amino acids in feedstuffs is another important factor to consider when formulating diets. Amino acids are digested in the small intestine and digestibility of feed ingredients can be determined by measuring the amino acids at the end of the small intestine, referred to as the ileum. Subtracting the undigested portion of amino acids at the end of the ileum from total amino acid intake provides an estimate of digested amino acids. Digestibility (%) can then be calculated from the fraction of digested amino acids relative to total amino acid intake. This value is then standardized for the amino acids an animal itself loses (called endogenous losses) in the effort of digesting the feed. These losses include enzymes secretions, intestinal cells that are sloughed off during digesta transit, mucus, and bacterial protein. The resulting calculation is the standardized ileal amino acid digestibility (SID).

 

Table 3. Amino acid ratio recommendations for growing and finishing swine^a

^aAll diets are full fed under thermoneutral conditions. ^bRactopamine hydrochloride (Paylean®).
 

The recommended daily amounts of total lysine and standardized ileal digestible lysine for high, medium, and low lean gain lines of finishing pigs for different body weights are shown in Table 4. If we assume a lean gain of 0.85 lbs/d for the period of interest (e.g. Phase 4), we can calculate that to be equivalent to 151 g protein/d (based on the assumption that 1 g of lean contains 0.392 g of protein [8]; 0.85 lbs/d of lean = 385 g/d of lean = 385*0.392 = 151 g protein/d). As stated previously, 0.12 g of SID lysine is required to gain 1 gram of protein. Thus, in this example, the pig requires 151 g protein gain/d * 0.12 g SID lysine/g of protein = 18.12 g SID lysine to support that protein gain. In addition, the pig requires 0.036 g SID lysine per kg of metabolic body weight for maintenance [8], which is 1.07 g/d (92 kg BW = 29.7 kg BW0.75, multiplied by 0.036 = 1.07 g/d). Thus the SID lysine requirement in this example is 19.2 g/d. The pig is only able to meet its lean gain potential if sufficient energy is available. Thus, if energy intake is limited, lean gain is compromised and consequently amino acid requirements would be lower. The recommendations as a percent in the diet can be calculated by using expected feed intakes (Tables 5A-5C for various weight ranges and lean gain potential). If feed intake predictions are different from those provided here, requirements can be calculated from the daily recommendations in Table 4. For example, pigs of high lean gain genotype (0.85 lbs per day of lean gain) fed a diet from 90 to 135 lbs of body weight (phase 2) require 17.7 grams of standardized ileal digestible lysine per day. If pigs are estimated to consume 4.1 lbs of feed per day during this growth phase, the dietary SID lysine would be: 100*17.7/(454*4.1) = 0.95%. The value of 100 is used to calculate the percentage and the value of 454 is the number of grams in each lb.

 

Energy Density: Pigs tend to eat to meet their requirement for energy. If the diet is high in energy, for example by adding fat, pigs typically decrease their intake. On the other hand, if the energy density of the diet is diluted by feeding fibrous feedstuffs, pigs will consume more feed (until gut capacity limits intake). Understanding this relationship is important when calculating nutrient recommendations, because nutrient concentrations required in the diet are energy dependent. A high energy diet will cause intake to decrease and, therefore, nutrient concentrations should be increased to maintain a constant daily intake. A diet low in energy should contain a lower concentration of nutrients because feed intake will be increased. By changing nutrient concentrations relative to expected feed intake, a constant nutrient to energy ratio will be maintained. As a rule of thumb, the addition of fat to the diet will improve Feed:Gain by approximately 0.04 points for every 1% fat added.

 

Ractopamine: Ractopamine is a ß-adrenergic agonist that is approved for inclusion in finisher diets. It increases fat-free lean by approximately 25-35%, depending on level of inclusion, and reduces fat deposition. Ractopamine is typically fed at 4.5 to 9.0 g/ton of complete swine finishing feed containing at least 16% crude protein for the last 45 to 90 lbs of gain. Ractopamine (trade name is Paylean) is approved for use at levels of up to 9 g/ton in the US. Because of the increased protein deposition, amino acid concentrations to support the improvement in lean gain need to be increased. Amino acid requirements for two finisher weight ranges when fed ractopamine are listed in Tables 5A-5C.

 

Calcium and Phosphorus: Phosphorus (P) is the third most expensive nutrient to provide in diet formulations for pigs after energy and amino acids. Further, P has been a focus area as it relates to concerns with its excretion into the environment. Thus, nutritional means to reduce P excretion have been evaluated, including selection of feed ingredients with high P digestibility, the use of phytase enzymes to improve P digestibility, and more closely matching P content of the diet to the actual needs of the pig throughout the growth cycle. Approximately 75% of P is located in bone, with the remainder being located in soft tissue. Almost all of the Ca in the body of pigs (99%) is located in bone. Thus, both Ca and P play an important role in bone mineralization. In addition, P is involved in essentially all metabolic processes in the body. The requirements for P can be estimated from P that is lost from the body due to normal metabolic processes (endogenous losses) and P that accumulates in the body as the pig grows. Alternatively, P requirements can be estimated based on feeding studies using various levels of P in the diet and determining the optimal response. Calcium is usually expressed as a ratio to P. Typically, this Ca:total P ratio should be between 1.0 and 1.5 and a ratio of 1:1 was applied to establish Ca requirements listed in this factsheet. The ratio of Ca to available P is usually held between 2.1 and 3.1. Maintaining the proper Ca:P ratio is important because a wide ratio will decrease absorption of P, especially at marginal dietary P concentrations.

 

The digestibility of P needs to be accounted for in the formulation of pig diets. Traditionally, the digestibility of P was expressed relative to a standard P source (usually sodium phosphate) to account for variation between studies and is referred to as available P. However, the use of digestible P values is becoming the norm. Recommendations for Ca, total P, available P, and digestible P when expressed on a daily basis are shown in Table 4 and when expressed as a percent of the diet are shown in Table 5A-5C. Available P recommendations are largely based on NRC [8], while using an appropriate margin of safety. Digestible P recommendations are based on a factorial approach, in which P requirements are calculated based on maintenance requirements and requirements for body P accretion. Because approximately 25% of the P in the body is present in soft tissue (primarily muscle), requirement estimates change depending on lean gain potential of the pig, with high lean pigs requiring more P than low lean pigs. For more information regarding Ca and P recommendations, please refer to PIG Factsheet # 07-02-03 (Understanding Swine Nutrient Recommendations).

 

Other minerals and vitamins: Other macro-minerals that need to be supplemented to swine diets, besides Ca and P, are sodium and chloride. This is usually accomplished by supplying salt. Micro-minerals are commonly supplemented as a separate mineral premix or a vitamin-mineral premix and include iron, zinc, copper, manganese, selenium and iodine. Vitamins are also supplemented as a premix, either separate or in combination with minerals. Ranges for recommended additions of sodium, chloride, micro-minerals and vitamins to growing-finishing swine feed are shown in Table 6. The ranges presented for trace minerals and vitamin additions offer feed manufacturers and producers greater flexibility in preparing and utilizing products based on our recommendations. This approach affords more flexibility and convenience and often reduces costs associated with handling and storing multiple products. In addition, the ranges acknowledge that information gaps exist in trace mineral and vitamin nutrition of pigs, making it difficult to establish firm recommendations. Except for salt, the minimum values generally represent the total amount required in the diet according to the NRC [8]. Upper values do not represent safe or tolerance levels, but instead a reference point above which further additions will not likely improve performance. Formulators should avoid the minimum and the highest nutrient concentrations in Table 6 in favor of intermediate values.

 

Specific recommendations for trace mineral and vitamin additions to growing-finishing swine feed are shown in Table 7. The values represent our best estimate of trace mineral and vitamin needs of finishing swine housed in practical situations. These values are based on NRC requirements to which a safety margin has been added. These levels disregard the trace mineral and vitamin levels that natural feedstuffs provide. For additional information on manufacturing base mixes and premixes for swine diets please refer to PIG Factsheet # 07-02-06 (Trace Minerals and Vitamins for Swine Diets).

 

Table 4. Recommended daily levels (grams per day) of lysine, calcium, and phosphorus for different lean gain lines of swine (as-fed basis)^a

^aHigh lean, medium lean gain and low lean gain were defined as >0.80 lbs, 0.65 to 0.80 lbs, and <0.65 lbs of fat-free lean/day from 45 to 270 lb. ^bRactopamine hydrochloride (Paylean®).

 

Table 5A. Amino acid, calcium and phosphorus recommendations for HIGH^a lean gain lines of swine (as-fed basis)^b

 

Table 5B. Amino acid, calcium and phosphorus recommendations for MEDIUM^a lean gain lines of swine (as-fed basis)^b

 

Table 5C. Amino acid, calcium and phosphorus recommendations for LOW^a lean gain lines of swine (as-fed basis)^b

For Tables 5a-c: ^a>0.80 lb of fat-free lean/day from 45-270 lb. ^bAll diets are full fed under thermoneutral conditions. ^cRactopamine hydrochloride (Paylean®). dB=barrows and G=gilts. ^eTotal phosphorus recommendations should be used as a guideline only; those recommendations may not be obtained when formulating practical diets on an available or digestible phosphorus basis which is recommended. Also, total phosphorus recommendations will not be achieved when phytase is included in the diet. ^fRecommended amount relative to dietary metabolizable energy (ME) density; energy values of ingredients from PIG factsheet #07-07-09 (Composition and Usage Rate of Feed Ingredients for Swine Diets) were used in the calculations.

 

Table 6. Ranges for recommended dietary additions of salt, trace minerals and vitamins from concentrates, base mixes or premixes for growing-finishing pigs (for specific dietary additions, see Table 7)^a

^aAll diets are full fed under thermoneutral conditions. ^bRactopamine hydrochloride (Paylean®). ^cMinimum values generally represent the quantity recommended by the NRC (1998). Upper values do not represent safe or tolerance levels, but instead a reference point above which further additions will not likely improve performance. ^d— indicates no data available. ^eMaximum legal addition is 0.3 ppm. ^fMenadione activity. ^gNRC requirement is 136 mg/lb total in the complete diet for phases 1 to 5, and this amount is met by traditional feed- stuffs so none is supplemented. ^hNRC requirement is 0.023 mg/lb total in the complete diet for phases 1 to 5, and this amount is met by traditional feed- stuffs so none is supplemented. ⁱNRC requirement is 0.136 mg/lb total in the complete diet for phases 1 to 5, and this amount is met by traditional feed- stuffs so none is supplemented. ^jNRC requirement is 0.45 mg/lb in the complete diet for phases 1 to 5 and this amount is met by traditional feedstuffs so none is supplemented.
 

Table 7. Specific recommended dietary additions of trace minerals and vitamins from concentrates, base mixes or premixes for growing-finishing pigs

^aRactopamine hydrochloride (Paylean®). ^bSalt is usually added at the rate of 6-7 lb/ton in grower-finisher diets to help provide a significant portion of the total dietary sodium and chloride recommendations. ^cRecommendations for sodium and chloride represent total dietary amounts, not additions. ^dMaximum legal addition is 0.3 ppm. ^eMenadione activity.

 

Nutrient Recommendations: We believe the nutrient recommendations provided in Tables 4, 5A-C, 6, and 7 will result in a “best cost” feeding strategy for most producers most of the time. However, certain conditions (i.e., specific genetic populations, economic, nutrient availability, nutrient profile, and nutrient interactions) may exist that require significant deviations from the recommendations presented. Also, the current debate surrounding the environmental consequences of nitrogen and phosphorus excretion was considered in the development of amino acid and phosphorus recommendations.

 

Although crude protein values still appear on feed labels and in some feeding recommendations, we did not list dietary protein recommendations because pigs do not require protein in their diet. Instead they require amino acids, which are found in protein. The recommended levels for the most critical amino acids are provided in Tables 5A-C. Lysine is the first limiting amino acid in grain-soybean meal based diets. Lysine recommendations are provided on a total basis and a standardized ileal digestible (SID) basis. Formulating diets on a SID basis allows one to account for differences in the useable amino acids present in the diet and more closely meets the pig’s amino acids needs while minimizing excess nitrogen excretion. The recommendations for threonine, methionine, methionine+cystine, tryptophan, isoleucine, valine, arginine, histidine, leucine, phenylalanine, and phenylalanine + tyrosine are also expressed on an SID basis. These recommendations were derived from an optimal pattern or ratio among amino acids that we established (Table 3).

 

Recommendations for amino acids, calcium and phosphorus are presented for barrows and gilts at different levels of lean gain (Tables 5A-C). They are also presented relative to the energy density of the diet, such that proper adjustments can be made depending on the choice of ingredients in the diet and subsequently its energy content. Competition among livestock feeders, human consumers, and biofuel producers may force swine producers to use non-traditional ingredients that are lower in energy density and higher in fiber. Consequently, nutrient recommendations have been presented on an energy basis. Regardless of dietary energy concentration, the recommended daily intake of nutrients is constant.

 

For trace-mineral and vitamin recommendations, we presented ranges to allow flexibility and to recognize that there is a lack of information in trace mineral and vitamin nutrition of pigs (Table 6). However, we also provided specific recommendations (Table 7) for trace mineral and vitamin additions to growing-finishing swine feed, which represent our best estimate of cost effective trace mineral and vitamin supplementation needs of finishing swine housed in practical situations.

 

Practical Feeding Considerations

 

Matching Nutrient Requirements: Nutrient requirements decrease as the animals grow heavier due to changes in the maintenance requirement and the composition of growth (less lean and more fat). In addition, feed consumption increases as animals grow heavier; therefore the nutrient composition of the diet can be decreased with increasing body weight. For example, according to NRC [8], a 140 lb pig requires 19.7 grams of total lysine compared to a 220 lb pig requiring 18.5 grams of lysine. Assuming a feed intake of 5.7 lbs/d and 6.8 lbs/d for the 140 and 220 lb pig, respectively, the lysine requirements would be 0.76% (100% x 19.7 g/(5.7 lbs x 454 g/lb)) for the 140 lb pig and 0.60% for the 220 lb pig.

 

Phase Feeding: The concept of phase feeding matches diets with specific nutrient compositions to the growth stage of the pig. It minimizes instances of overfeeding (wasting costly nutrients) and underfeeding (not meeting the nutrient requirements, causing suboptimal growth). Phase feeding will reduce the overall diet cost per pig and is a cost effective method of reducing nutrient excretion. The greatest benefit of phase feeding is obtained when going from a single to a two phase feeding program. Each additional phase will still improve profitability and reduce nutrient excretion, but the impact on profitability decreases with increasing number of phases. From a practical perspective, it may not be feasible to change the feed often, e.g., weekly, unless feeding equipment is available that is designed for this purpose. However, in practice, six dietary feeding phases throughout the grower-finisher period are common. The example of phase feeding in Figure 2 shows that the lysine requirement of the pig is matched more closely by using a 6-phase feeding program (red line) than a 2-phase feeding program (blue line). Feeding of excesses (when the blue or red lines are above the green line) or not feeding enough (when the blue and red lines are below the green line) can be minimized.

 

 

Split-sex Feeding: Similar to phase feeding, separate sex feeding will more closely match nutrient concentrations in the diet to the requirement of the pig and is expected to result in a reduction in nutrient excretion and savings in diet costs. Barrows typically have a higher feed intake capacity (from approximately 80 lbs of body weight) without a larger potential for lean gain, and thus diets should be fed that are somewhat lower in amino acid concentrations. Tables 5A-5C show a summary of nutrient requirements for gilts and barrows at different lean gain potentials, different body weight stages and estimated feed intakes. Rather than formulating separate diets for gilts and barrows, split sex feeding can be managed by feed budgeting by simply feeding gilts an earlier phase diet than barrows at the same body weight. Thus, gilts can be fed a more nutrient dense diet for the first phase in the finisher, followed by the diet that barrows consumed as their first diet. At the end of the finisher, gilts can be fed the last phase diet and an additional barrow diet can be formulated with lower nutrient density for the final phase.

 

Use of Feed Budgets: From a practical standpoint, feed budgets can be used to practically manage the amount of each feed that is supplied to the pigs for each phase. This method eliminates the need for estimating pig weights to determine when to switch feeds. They are based on cumulative feed consumption estimates over the entire weight range in finishing. An example feed budget is shown in Table 8. From this Table, it can be seen that a pig starting at 50 lbs of body weight and ending at 80 lbs of body weight will consume 63 lbs of feed. During the next phase, from 80 lbs to 120 lbs, the pig will consume 97 lbs of feed (160 – 63; feed intake shown is cumulative, thus the pig in this example had already consumed 63 lbs out of the 160 lbs to reach 80 lbs of body weight). Feed intake per pig can be calculated for any feeding phase and multiplied by the number of pigs in the barn. Once that amount of feed has been consumed, it is time to start feeding the next phase.

 

Table 8. Feed budget for finishing pigs with an estimated feed efficiency of 2.8.

 

Feeder Management: Proper feeder management may be an easy way to reduce feed wastage and therefore improve efficiency of feed utilization. First of all, the type of feeder that is being used can affect feed wastage. For example, Taylor and Curtis (1989) [9] studied 11 self-feeders for pigs in the 50 to 125 lb weight range. They measured feed wastage by determining how much feed fell on and through the floor and found a range of feed wastage from 2.1 to 7.7%. Researchers in several countries have estimated feed wastage and have quoted values of 4% in the U.S. (with a range from 2 to 12%), 6% in Great Britain (with a range of 1.5 to 20%), and 3 to 5% in Denmark. A reduction in feed wastage of 1% can be calculated to save $0.71 per pig marketed (assuming a feed efficiency of 2.8 and a feed cost of $0.12/lb). In addition, a 2% reduction in feed wastage can reduce the N and P in manure by approximately 3% (based on a N and P retention of 35%). For proper feeder adjustment, the rule of thumb is that about 50% of the bottom of the trough needs to be covered with feed and 50% of the trough bottom needs to be visible.

 

Out-of-feed events: Proper management of feed, including delivery of the correct feed to the assigned bin and keeping fresh feed in front of the pigs at all times is essential to maximize production efficiency. Failure to order feed in time, properly manage feed and feeders to avoid bridging, or maintain equipment for proper functioning can be costly. Brumm and coworkers [10] demonstrated that pigs exposed to out-of-feed events on a weekly basis gained less weight than pigs that always had feed available, resulting in an reduction of 8 lbs in final body weight. The impact of out-of-feed events was more pronounced in younger pigs than older pigs. In fact, older pigs were able to compensate for the restriction in feed by increasing their subsequent intake. In addition, out of feed events can increase the incidence of gastric ulcers [11]. Checking feed bins and feeders routinely will help alleviate instances of out-of-feed events. Use of technologies, such as use of load cells on feed bins, can also aid in managing feed inventory and feed ordering. In addition, placing the heaviest pigs (consume the most feed) close to the auger switch will allow for a quick and easy indicator of feed availability for the entire barn.

 

Diet and Carcass Quality. Swine breeding and nutrition programs have focused on producing a lean, high quality pork product. Thus, efforts have focused on eliminating Pale Soft and Exudative pork and soft carcass fat. Soft fat is a problem in the further processing of pork, particularly bacon slicing. The dietary source of fat has a great impact on the softness of fat in the pig carcass. High levels of unsaturated fatty acids in the diet result in soft fat in the carcass. This problem has become more pronounced recently with high inclusion levels of dried distillers grains with solubles (a byproduct of ethanol production from grains with high levels of unsaturated fat) in swine diets. Additional information on the effects of diet on pork quality can be found in PIG Factsheet # 12-02-02 (Nutritional Effects on Pork Quality in Swine Production).

 

Feed Quality. Once nutrient requirements for the proper stage of growth have been determined, proper feeds need to be formulated and manufactured to meet these requirements. Ingredients of a consistent and known quality should be chosen for inclusion in the diet. Analysis of feed ingredients for nutrient content and potential contamination with mycotoxins should be conducted. In addition, the manufactured feeds should be analyzed on a regular basis to ensure that the nutrient composition of the diet matches the calculated composition. Detailed information on feed quality control and feed manufacturing can be found in PIG Factsheets #07-04-02 (Swine Feed and Ingredient Sampling and Analysis) and #07-04-03 (Swine Feed Processing & Manufacturing).

 

Record keeping. To estimate nutrient requirements, the performance level (growth rate and carcass lean) and feed intake of the herd need to be known. These measures can be obtained on the farm and should be evaluated routinely. Not only are these records important to set nutrient recommendations (and avoid under- or overfeeding), but they are also important to evaluate performance of pigs on a site with expected performance targets (Table 9). Obtaining performance data for a production system can be accomplished in one of two ways:

1.  Keep records on the dates, number, and weight of the pigs entering the finishing barn. Record dates, number, and weight of pigs when they are marketed. This will allow the calculation of average daily gain for the barn. Also, keep records of feed deliveries, including diet type or phase, total amount delivered, delivery dates, and costs. This will allow for the calculation of daily feed disappearance (represents feed consumed plus feed wastage), feed cost per pig, and feed cost per lb of pig produced. Including packing plant data for the group of pigs will allow for the calculation of lean gain as outlined previously (Determining Lean Gain section).
2. Pig performance data can also be obtained by selecting a representative sample of pens within the barn (about 10% of the pens in the building) and tracking pig growth rate and feed disappearance in these pens. Using this method, pig weights at multiple times throughout the grow-finish period need to be taken. In addition, feed disappearance for each time period can be calculated by totaling the amount of feed offered for each time period and subtracting the amount of feed left in the feeder at the end of each time period. This can be done for mixed sex pens, or separately for gilts and barrows. Although this is more labor intensive then the first method, it provides information throughout the entire growth stage of the pigs.

 

Table 9. Pig performance benchmarks in finishing for pigs with a starting body weight of 50 lbs and a market weight of 260 lbs.

 

Summary

 

Feed represents 65 to 75% of the total cost of producing pork, with feed cost for growing-finishing pigs representing approximately 75% of this cost. Close consideration of nutrient recommendations and practical feeding guidelines is essential to allow for optimal production efficiency. This factsheet outlines nutrient requirements of growing-finishing pigs and how there are impacted by the pigs lean gain potential and the environment. Estimated amino acids, macro-minerals, micro-minerals, and vitamin recommendations for pigs of different lean gain potential are provided in combination with practical feed and management recommendations for optimal productivity.

 

References

1. Johnson, R. K., E. P. Berg, R. Goodwin, J. W. Mabry, R. K. Miller, O. W. Robison, H. Sellers, and M. D. Tokach. 2004. Evaluation of procedures to predict fat-free lean in swine carcasses. J. Anim. Sci. 82:2428-2441.
 
2. Brannaman, J. L., L. L. Christian, M. F. Rothschild and E. A. Kline. 1984. Prediction equations for estimating lean quantity in 15- to 50-kg Pigs. J. Anim Sci. 59:991-996.
 
3. Ellis, M. and N. Augspurger. 2001. Feed intake in growing-finishing pigs. P. 447-467, Swine Nutrition (Lewis, A. J. and L.L. Southern, Eds.). CRC Press, Boca Raton, LA.
 
4. Verstegen, M. W. A., K. H. de Greef, and W. J. J. Gerrits. 1995. Thermal requirements in pigs and modeling of the effects of coldness. In: P. 123-135, Modeling growth in the pig, EAAP Publication No. 78. Wageningen Pers, Wageningen, The Netherlands.
 
5. Noblet, J., J. Le Dividich, and J. van Milgen. 2001. Thermal environment and swine nutrition. In: P. 519-544, Swine Nutrition (Lewis, A. J. and L.L. Southern, Eds.). CRC Press, Boca Raton, LA.
 
6. Gonyou, H.W., M.C. Brumm, E. Bush, J. Deen, S.A. Edwards, T. Fangman, J.J. McGlone, M. Meunier-Salaun, R.B. Morrison, H. Spoolder, P.L. Sundberg, and A.K. Johnson. 2006. Application of broken-line analysis to assess floor space requirements of nursery and grower-finisher pigs expressed on an allometric basis. J. Anim. Sci. 84:229-235.
 
7. Williams, N. H., T. S. Stahly, and D. R. Zimmerman. 1997. Effect of level of chronic immune system activation on the growth and dietary lysine needs of pigs fed from 6 to 112 kg. J. Anim. Sci. 75:2481-2496.
 
8. NRC. 1998. Nutrient Requirements of Swine. 10th Ed. National Academy Press, Washington, DC.
 
9. Taylor, I.A. and Curtis, S.E. 1989. Grower Feeders: 11 Designs Reviewed. National Hog Farmer, December 1989.
 
10. Brumm, M.C., S.L. Colgan, and K.J. Bruns. 2008. Effect of out-of-feed events and diet particle size on pig performance and welfare. J. Swine Health Prod. 16(2):72-80.
 
11. Lawrence, B.V., Anderson, D.B., Adeola, O, and Cline, T.R. 1998. Changes in pars esophageal tissue appearance of the porcine stomach in response to transportation, feed deprivation, and diet composition. J. Anim. Sci. 76:788-795.

 

Frequently asked questions:

 

What is the impact of fat on finishing pig performance?
Inclusion of fat into diets for finishing pigs will improve feed efficiency by approximately 2% for each 1% of fat added to the diet. During hot temperatures in the summer, the advantage of feeding fat will be greater because fat is utilized very efficiently, limiting the amount of heat the animal expends in metabolizing fat. Fat in the carcass may increase, especially when levels of fat added to the diet are high and exceed the energy requirements of the pig. Younger pigs with a high level of lean growth may not be able to eat enough to meet the energy requirements for lean growth. In this case, increasing the energy density of the diet by adding fat will be advantageous. Care should be taken in supplying sufficient levels of amino acids in the diet relative to dietary energy content. For example, when increasing the dietary energy content from 1,500 kcal/lb to 1,575 kcal/lb (increase of 5%), then the amino acid concentrations in the diet need to be increased by 5% as well to maintain a constant amino acid:calorie ratio. The type of fat used is important. Unsaturated fats (oils) fed during the finishing phase will cause soft fat in the carcass, which can cause problems in further processing of the carcass, especially bacon slicing. Fat can be added to pig diets to reduce levels of dust in the barn, which improves air quality in the barn.

 

What is the value of separate sex feeding?
Separate sex feeding will more closely match nutrient concentrations in the diet to the requirement of the pig and is expected to result in a reduction in nutrient excretion and savings in diet costs. Feed intake of gilts is approximately 7% lower during the finishing phase compared to barrows, but their daily rate of lean growth is similar or greater. Therefore, amino acid concentrations in the diets for gilts should be greater than those for barrows. This can be accomplished by designing separate feeding programs for barrows and gilts. Alternatively, split sex feeding can be managed by feed budgeting by simply feeding gilts an earlier phase diet than barrows at the same body weight. Thus, gilts can be fed a more nutrient dense diet for the first phase in the finisher, followed by the diet that barrows consumed as their first diet. At the end of the finisher, gilts can be fed the last phase diet and an additional barrow diet can be formulated with lower nutrient density for the final phase.

 

How many diet phases should I feed throughout the finisher period?
Phase feeding applies several different diets throughout the finishing phase to match the diet to the nutrient needs of the pig. It minimizes instances of overfeeding (wasting costly nutrients) and underfeeding (not meeting the nutrient requirements, causing suboptimal growth). The number of phases to feed depends on each specific situation. The greatest benefit of phase feeding is obtained when going from a single to a two phase feeding program. Each additional phase will still improve profitability and reduce nutrient excretion, but the impact on profitability decreases with increasing number of phases.