Gestating Swine Nutrient Recommendations and Feeding Management
Feeding management during gestation focuses on minimizing embryo and fetal losses and on preparing the sow for farrowing and lactation. In the very early stages of gestation immediately after conception, the first objective is to provide conditions that will ensure maximal survival of embryos and favor a large litter size at the subsequent farrowing. Growth of the developing fetuses in conjunction with increasing nutrient stores in the sows body through continued growth of young sows or replenishment of nutrient stores lost during the previous lactation for older sows are the main objectives during mid-gestation (day 30 to 75). In late gestation, fetal growth continues at a very rapid rate and mammary development occurs in preparation for the upcoming lactation. Proper feeding programs will satisfy these nutritional needs and ensure continued reproductive performance of sows at a reasonable cost.
The desired outcomes of a successful gestation feeding program are:
- A large, vigorous litter of pigs at farrowing;
- A healthy sow equipped to produce large quantities of milk for the suckling litter.
The easiest approach to feeding pregnant sows is to determine an “average” feed intake desired throughout gestation and feed that amount of feed each day from mating to farrowing. While this is simple, it does not reflect the changing nutrient needs of sows as pregnancy advances. Modern productive sows will likely become catabolic (use body stores of nutrients) during the late phases of gestation because nutrient supply from feed intake will not satisfy daily nutrient needs. To avoid this disparity in nutrient supply and demand, most producers use a phase feeding program for gestating sows. With this approach, sows are fed maintenance levels of feed in the early portion of gestation (day 0 to 30) because nutrient needs of the developing litter are extremely small. In addition, high level feeding in this very early phase can have detrimental effects on embryo survival before implantation . During mid-gestation (days 30 to 75), feed intake is generally kept near maintenance levels but can be altered to permit: 1) modest body weight gains for sows in thin body condition; or 2) modest body weight reduction if sows are in greater than ideal body condition.
Fetal growth rate after day 75 of pregnancy increases dramatically compared with early and mid-gestation . To satisfy the associated increase in nutrient demand, feed intake should be increased during the last 3 to 4 weeks of gestation. An important portion of the weight gain in the products of conception (fetuses, placenta, mammary gland) is attributable to water gain. Consequently, the energy and amino acid needs of the developing litter can be satisfied by an additional 1.5 to 2.0 pounds of a typical corn-soybean meal gestation diet . Increasing feed intake more than 2.0 pounds/day in late gestation is not justified based on nutrient needs of the developing litter. One must be cautious of large increases in feed intake in late gestation and the potentially negative effects on mammary development, and excessive sow weight gains that may depress feed intake during the subsequent lactation.
Overfeeding throughout gestation leads to fat sows and several important problems with subsequent sow performance. High energy intakes can lead to compromised mammary development with potentially reduced milk production in the subsequent lactation . Gestational gains in body weight and fatness are related inversely to voluntary feed intake of sows during lactation [5, 6] and sow longevity . Therefore, excessive feed intake in gestation depresses lactation feed intake of sows. Finally, fat sows are more likely to tire during parturition leading to increased stillbirths and fat sows are more clumsy leading to more piglets being laid on compared with sows in desirable body condition. Furthermore, longevity in the commercial herd is reduced when sows are fat.
Establishing nutrient requirements and feed allowances
Variations in body size and condition, productivity, stage of gestation, health status, and environmental circumstances dictate different daily amounts of nutrients be fed to satisfy the sow’s requirements. Nutrient requirements for gestating sows can be broken down into three basic components: maintenance, fetal growth, and maternal weight gain. Each of these components can be estimated individually and the components then summed to establish the sow’s total daily nutrient requirement.
Maintenance. Nutrient requirements for maintenance are influenced primarily by body weight of the sow and the environment in which the female is housed. Older, heavier sows have increased nutrient needs and will require more feed to maintain their body than younger, lighter sows. Maintenance energy requirements account for 75-85% of the sow’s total energy requirement. In general, for every 50-lb increase in sow body weight daily metabolizable energy needs increase about 470 kcal which requires about 0.33 pounds of additional feed (assumes a corn-soybean meal based diet). In addition to body weight, maintenance energy requirements are influenced by the effective ambient temperature experienced by the sow. The effective ambient temperature is not necessarily the thermometer reading but is the temperature that the sow experiences. Use of bedding provides insulation so reduced temperatures do not feel as cold to the sow. Conversely, wet conditions make the sow feel colder than the thermometer reading due to evaporative heat loss. Under commercial conditions, we are most concerned about temperatures that fall below the sow’s thermoneutral, or comfort, zone. These cooler temperatures require increased energy and hence feed intake to maintain the sow’s core body temperature without the need for the sow to mobilize her own body tissues. Generally speaking, for every 10oF drop below 65oF individually-housed sows should receive an additional 0.8 pounds of a corn-soybean meal diet to satisfy their maintenance energy requirement. Group housing and use of bedding material can help the sow conserve body heat so increased feeding levels need not be implemented until temperatures fall below 50 to 55°F.
Fetal growth. Growth of the products of conception and the associated nutrient needs for that growth are fairly resistant to nutritional manipulations at feed intakes typical of production settings. Under conditions of adequate energy intakes ranging from 6 to 10 Mcal ME daily, changes in weight of fetuses are relatively small . Similarly, feeding level has little influence on body composition of fetuses. However, when survival rate of piglets is less than 80%, feeding sows at least 2.5 pounds of supplemental fat over the last 2 to 3 weeks of gestation can improve energy stores in the piglet’s body and increase piglet survival rates 5 to 6 percentage units . Feeding a lactation diet containing 3% added fat at 6 lb/head/day for 14 days before farrowing will achieve the desired fat intake.
Extreme reductions (50 to 60%) in nutrient intake of pregnant sows will reduce birth weight of pigs and decrease muscle fiber numbers at birth. These low birth weight pigs can have decreased growth performance to market, decreased lean content of carcasses at harvest and compromised meat quality compared to pigs with normal birth weight . If severe restrictions in nutrient intake will compromise performance of the offspring, will elevated nutrient intake of pregnant sows during specific periods of gestation improve performance of pigs? In general, increased nutrient intake of sows does not seem to improve performance of offspring to slaughter weight. The elevated plane of nutrition for pregnant sows may benefit low weight fetuses present in the uterus but this theory has not been proven.
Maternal weight gain. Conceptually, maternal weight gain is supported by “extra” nutrients available after needs for maintenance and fetal growth are satisfied. Maternal weight gain accounts for about 15 to 25% of the sow’s total energy needs. The composition of this weight gain is determined primarily by parity of the sow and diet composition . Similarly, the amount of maternal weight gain desired will depend on age of the sow (Table 1). Young sows (parity 0 and 1) are still growing so more weight gain should be allowed compared with older sows that have reached their mature body weight. Gains in maternal body weight provide a reservoir of nutrients for the upcoming lactation should the demands of milk production exceed nutrient intake from feed. However, excessive weight gains can predispose the sow to poor performance during lactation as mentioned previously.
Table 1. Performance levels of sows by parity
|Parity 0 and 1||Parity 2 or Greater|
|Litter size, total born||10.5||12.5||12||14|
|Assumed total gestation weight gain, lb||115||125||80||90|
Practical considerations in feeding pregnant sows
Feed delivery. There are many approaches to supplying feed to gestating sows. Regardless of the method employed, accuracy of feed delivery is important. Systems must be calibrated regularly to determine if the proper daily allotment of feed is being delivered. This is especially important for systems that use volumetric measures of daily feed allowances. Changes in bulk density of feed can significantly alter the weight of feed the sow receives. In addition, design of the feed drop hopper and method of installation can have important influences on amount of feed delivered to sows. Some hopper designs consistently supply more feed than intended to sows. Changing the angle of installation can also influence the quantity of feed delivered . Remember that sows eat pounds of feed not quarts or gallons of feed!
Sows are limit-fed throughout gestation which means that sows would naturally consume more feed (and nutrients) if allowed. Limit-feeding creates competition among sows at feeding time. Currently, a large portion of sows are housed individually in stalls, ensuring each sow receives her daily allotment of feed. Societal pressures and concerns for welfare of individually housed sows will likely make group housing of sows more prevalent in the foreseeable future. Group housing presents special challenges in providing a complete feed allotment to submissive sows and preventing dominant sows from consuming more than their share of feed. Electronic sow feeders (ESF) are useful tools to achieve this objective. These feeders allow sows to consume feed individually in a stall with computer-controlled access but still be housed in groups. Individual feed allotments are also controlled by the computer. Feeding stalls may also be used to feed sows individually and minimize competition. Sows are restricted to the stalls for a short time period during feeding, and are allowed to exit after eating. This system is less expensive and does not require the technical expertise of maintaining an ESF, but also requires considerably more labor and space. If an ESF or individual feeding stalls are not used, daily feed allotment for sows in group housing will likely need to be increased slightly (5 to 10%) to account for increased wastage and to ensure submissive sows receive adequate feed.
Some management systems implement interval feeding of group-housed gestating sows as a way to reduce labor requirements of feeding. Interval feeding programs are designed to provide feed to sows every second or third day rather than daily. The total amount of feed offered over a three-day period is the same in either an interval or daily feeding program. Under an interval feeding program, sows are fed every third day but gilts are fed every other day. Animal caretakers must make a concerted effort to monitor daily the health and well-being of each sow even though they are not feeding sows every day.
Limit-fed sows likely experience hunger and may develop behavioral vices called stereotypic behaviors. Stereotypic behaviors are defined as those motions that are repeated regularly, serve no obvious function, and are apparently useless to the animal. Stereotypic behaviors can include, but are not limited to: bar biting, sham chewing (chewing motions which are not associated with feeding), vacuum chewing, and nosing or licking the floor or feeder when feed is not present. Stereotypic behaviors have been used to indicate compromised welfare of sows. The most effective way to substantially reduce stereotypic behaviors is to increase feeding levels. However, this approach results in excessive body weight gains and compromised sow performance. Some researchers have increased feeding frequency from once daily to twice daily  or 6 times daily  with no demonstrable improvement in behavior. European researchers have used high levels (> 50%) of sugar beet pulp to effectively reduce stereotypic behaviors. However, it seems that these diets are not practical for most U.S. feed delivery systems .
Dietary fiber. The gestating sow seems to be the most capable class of swine in modern production systems to effectively utilize dietary fiber. The need to limit energy intake for the control of gestation weight gain makes the gestating sow a logic choice to consume fibrous feedstuffs as part of the diet. Fiber can serve as a laxative agent and may improve comfort of sows fed limited quantities of feed. Dietary fiber decreases the energy and bulk density of the diet which limits energy intake and thus controls body weight gain without severely restricting total feed intake. Allowing sows to consume a larger quantity of feed decreases expression of stereotypic behaviors, increases level of satiety in the sow, and presumably improves well being of the sow. Feeding relatively large quantities of a bulky diet throughout gestation can enhance voluntary feed intake of sows during the subsequent lactation . Dietary fiber offered during gestation can increase litter size at the subsequent farrowing but the response can be variable . Litter size weaned may be improved about 0.5 pigs/litter when fiber is added to the sow diet during gestation. Some nutritionists  have suggested sows consume 350 to 400 g/d of neutral detergent fiber (NDF) to maximize the chance of an improvement in sow reproductive performance. Diets containing 45% wheat midds, 20% soybean hulls, 25% alfalfa meal, 30% sugar beet pulp, or 40% oats provide sows about 350 g/d of NDF when fed at 6 Mcal ME daily. However, others have reported no improvement in litter size farrowed or weaned when sows consumed high fiber diets during gestation [17, 19]. Fiber characteristics differ among fibrous feedstuffs. It appears that most of the beneficial effects of dietary fiber are realized when ingredients high in soluble fiber, such as sugar beet pulp, are included in the diet.
Fibrous feedstuffs have been investigated for use in self-feeding programs for gestating sows. The bulky characteristics and low energy density of fibrous feedstuffs make them a logical choice in feeding programs designed to save labor and capital expense by allowing sows continuous access to feed. Theoretically, including very high levels of fibrous ingredients should limit the daily energy intake of pregnant sows thus controlling their gestational gains in body weight. Unfortunately, this theory does not work effectively in practice for most feed ingredients . With the exception of sugar beet pulp, sows consume excess energy and gain excessive body weight when allowed free access to most high-fiber diets (Table 2).
Table 2. Voluntary feed intake and body condition changes of gestating sows provided ad libitum access to high-fiber diets for three weeks 
|Trait||Beet pulp (65%)a||Barley straw (36%)||Oat hulls (37%)||Malt culms (45%)||Rice bran (61%)||Wheat bran (67%)|
|Feed intake, lb/d||5.1||14.1||17.0||15.0||16.8||15.6|
|DE intake, Mcal/d||5.9||13.6||18.9||16.7||16.9||17.4|
|BW change, lb||4.8||92.1||105.1||103.0||90.0||86.4|
|Backfat change, in||-0.14||0.02||0.05||0.04||0.11||0.12|
aProportion of the final diet.
Dietary fibers may create some problems in certain pork production systems. The lower digestibility of fibrous feedstuffs compared to typical energy and protein sources combined with increased daily allotment of feed results in larger quantities of fecal material being generated. In some cases, increases of 60 to 90% in fecal matter excretion have been reported [21, 22]. This increases time and expense of manure removal from confinement production systems. In addition, the bulky nature of fecal material can slow the transfer of manure through perforated floors into storage units. This may create dirty housing conditions for sows. Increased daily feed allowance often will increase cost of feeding sows.
Determining feed allowance
Determining the proper feed allowance is crucial to the success of a gestation feeding program. The proper feed allowance will ensure large healthy litters and allow adequate body tissue reserves for the upcoming lactation. To achieve this objective, gilts (Parity 0) should gain 120 to 130 pounds in their first gestation and first parity sows should gain 110 to 120 pounds from mating to farrowing. Parity 2-5 sows should gain 80 to 90 pounds and mature sows (parity 6+) should gain about 65 pounds from mating to farrowing. Target backfat thickness at the 10th rib should be 0.7 to 0.8 inches at farrowing. While there is debate over what the ideal backfat depth should be on a sow at farrowing, this range generally indicates a sow in ideal body condition. However, some very lean, heavy milking genotypes may have difficulty achieving this level of backfat thickness at farrowing.
Condition scores. Some producers establish a base feeding level and then adjust it up or down according to the sow’s body condition score (Figure 1). Sows are scored visually on a scale of 1 (thin) to 5 (fat), and are fed to achieve a condition score of 3 at farrowing. Sows should be condition scored periodically to determine if feeding level needs to change to achieve the target condition score at farrowing. While this system is easy to implement, it is not very accurate. Sows with the same condition score can have drastically different backfat levels. Reasons for this variance are many but are most likely due to the differences among observers, and differences in the degree of muscling present in sows. It is important to note that body condition scores should include an assessment of backfat depth and muscling because both tissues serve as nutrient reservoirs during the subsequent lactation.
Measuring backfat thickness. A more accurate method of determining backfat thickness is to measure it directly with an ultrasonic probe. While these probes have differing degrees of accuracy and must have a trained operator, they are more accurate than a visual condition score. A direct measurement of backfat thickness does not account for body weight gain nor body protein gain.
Measuring body weight. Since sow body weight determines the majority of nutrient requirements of a gestating sow, it is very important to accurately determine body weight of sows. The best way to do this is to weigh sows with a livestock scale. The only true replacement for a livestock scale is another livestock scale! Visual assessments of body weight are not accurate. On many farms, installing a scale in a common hallway between gestation quarters and farrowing rooms allows workers to weigh sows as they enter the farrowing room and when they leave at weaning. All the sows do not have to be weighed to paint a useful picture of sow weight changes in the operation. Weighing ten to twenty sows from each parity group (Parity 0, 1, 2, 3-5, and 6+) and each season (summer, spring/fall, and winter) will suffice if labor and time constraints prevent weighing all sows. This information is extremely important to allow evaluation of both the gestation and lactation feeding programs and to aid in fine-tuning the feeding program.
In the absence of a livestock scale, producers can estimate sow weight with a flank-to-flank measurement . To record this measurement, a cloth tape measure is stretched from one rear flank over the sow’s back to the opposite rear flank (Figure 2). This flank-to-flank measurement is used in the following equation to estimate sow weight:
Sow weight, lb = 26.85 x (Flank measurement, in.) – 628
This approach properly assigns sows into 75-lb body weight categories about 70% of the time. While not as accurate as a scale but certainly more accurate than “eyeballing” sow weight, this method can be of some use and help producers determine sow weight and ultimately the proper feed allowance for sows.
Using sow weight and backfat to determine feeding strategy. Researchers at Kansas State University have developed a matrix based on sow weight (measured or estimated) and backfat depth at mating to establish feeding levels for individual sows . Obviously, this approach will work only for individuallyfed sows. This method reduced the occurrence of over-conditioned sows and reduced overall gestation feed costs due to more precise feed allocations when compared with a feeding system based on visual condition scoring. However, sow performance during lactation was unaffected. Implementation of such a feeding program requires attention to details because the required feed intake of sows will vary based on body weight and backfat thickness.
Target feeding levels. Using the levels of performance indicated in Table 1 and body weight of sows or estimated body weight of sows, one can develop suggested target feeding levels for gestating sows of differing parities (Table 3). These target feeding levels assume sows are housed in thermoneutral conditions and are in desirable body condition at weaning. If sows are thin, additional feed will be required to improve condition of sows. Feeding levels in Table 3 allow for additional weight gain of younger sows compared with older sows. The feeding allowances in Table 3 should be viewed as a logical starting point from which adjustments must be made to accommodate conditions within specific farms.
Table 3. Suggested feeding level for sows of various parities and body weights
|Body weight, lb||Flank-to-flank, inches1||Daily feed allowance, lb2,3|
|250 – 350||32.7 – 36.4||4.5|
|350 – 450||36.4 – 40.1||5.2|
|350 – 450||32.7 – 36.4||4.8|
|450 – 550||40.1 – 43.8||5.5|
|550 – 650||43.8 – 47.6||6.1|
|350 – 450||32.7 – 36.4||4.0|
|450 – 550||40.1 – 43.8||4.6|
|550 – 650||43.8 – 47.6||5.2|
1See text for relationship between body weight and flank to flank measurement . 2Assumes 1.5 Mcal ME/lb of diet. 3For sows in desirable body condition (0.7 to 0.8 inches backfat depth), thin sows should receive 0.5 to 0.75 addition- al feed daily to improve body condition. 4Suggested feed intakes based on the following assumptions: Parity 0 – 11 pigs/litter and 125 lb gestation gain; Parity 1-12 pigs/litter and 115 lb gestation gain; Parity 2+ – 13 pigs/litter and 85 lb gestation gain.
The nutrient recommendations in Tables 4, 5, 6, and 7 will result in a “best cost” feeding strategy for most producers the majority 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, the constituents that make up protein. The recommended levels for the most critical amino acids are provided in Tables 4 and 5. 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 amino acid needs of pigs while minimizing excess nitrogen excretion.
The recommendations for threonine, methionine, methionine+cysteine, 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 are presented in PIG Factsheet #07-02-03 (Understanding Swine Nutrient Recommendations).
Recommendations for amino acids, calcium and phosphorus are presented for sows consuming higher and lower energy diets (1.51 and 1.35 Mcal of metabolizable energy/lb, respectively). Competition among livestock feeders, human consumers, and biofuels 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 for diets of differing energy density. Regardless of dietary energy concentration, the recommended daily intake of nutrients is constant.
Ranges are presented for recommended additions of salt, trace minerals and vitamins to gestation diets (Table 6) to 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 (1998). Upper values do not represent safety or tolerance levels, but instead a reference point above which further additions are unlikely to 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 sow gestation feed are shown in Table 7. The values represent our best estimate of trace mineral and vitamin needs of gestation sows in practical situations. These values are based on NRC requirements to which a safety margin has been added. These levels assume that natural feedstuffs provide none of the nutrient of interest. Those seeking nutritional information for manufacturing basemixes and premixes for swine diets may learn more in PIG Factsheet #07-02-06 (Trace Minerals and Vitamins for Swine Diets).
The recommendations reflect differences in nutrient requirements for sows according to their parity, litter size born and weight gain. We assumed sows are housed under thermoneutral conditions. Deviations from the conditions described in the above recommendations will require adjustment in nutrient levels of the final diet.
Table 4. Amino acid, calcium and phosphorus recommendations for gestating swine fed higher energy diets (as-fed basis)a
|Parity 0 and 1b||Parity 2 or greaterc|
|Litter size, total born (Assumed feed intake, lb/dayd)||10.5 (4.6)||12.5 (4.7)||12 (4.1)||14 (4.2)|
|Assumed total weight gain, lb (Dietary metabolizable energy, Mcal/lb)||115 (1.5)||125 (1.5)||80 (1.5)||90 (1.5)|
|% of diet|
|Standardized ileal digestible|
|Methionine + cysteine||0.41||0.42||0.35||0.37|
|Phenylalanine + tyrosine||0.58||0.60||0.50||0.52|
|Standardized ileal digestible|
|Methionine + cysteine||1.23||1.27||1.06||1.10|
|Phenylalanine + tyrosine||1.76||1.82||1.51||1.57|
|Calculated daily intake, g|
|Metabolizable energy, Mcal||6.90||7.05||6.15||6.30|
|Standardized ileal digestible|
aAll diets are limit-fed under thermoneutral conditions. These diets would typically be based on corn and soybean meal fortified with vitamins and minerals. Very low additions (2%) of
supplemental fat may also be included to achieve the indicated energy density. bParity 0 = first gestation period (female has not farrowed a litter); parity 1 = second gestation period (female has farrowed one litter previously). cParity 2 = third gestation period (female has farrowed two litters previously). dAdjust to achieve a desired body condition or weight gain. 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.
a All diets are limit-fed under thermoneutral conditions. These diets would typically be based on corn and soybean meal fortified with vitamins and minerals. Very low additions (2%) of supplemental fat may also be included to achieve the indicated energy density. bParity 0 = first gestation period (female has not farrowed a litter); parity 1 = second gestation period (female has farrowed one litter previously). c Parity 2 = third gestation period (female has farrowed two litters previously). dAdjust to achieve a desired body condition or weight gain. e Total 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. f Recommended 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 5. Amino acid, calcium and phosphorus recommendations for gestating swine fed lower energy diets (as-fed basis)a
|Parity 0 and 1b||Parity 2 or greaterc|
|Litter size, total born (Assumed feed intake, lb/dayd)||10.5 (5.1)||12.5 (5.2)||12 (4.6)||14 (4.7)|
|Assumed total weight gain, lb (Dietary metabolizable energy, Mcal/lb)||115 (1.35)||125 (1.35)||80 (1.35)||90 (1.35)|
|% of diet|
|Standardized ileal digestible|
|Methionine + cysteine||0.37||0.38||0.31||0.32|
|Phenylalanine + tyrosine||0.53||0.54||0.44||0.46|
|Standardized ileal digestible|
|Methionine + cysteine||1.25||1.27||1.04||1.08|
|Phenylalanine + tyrosine||1.78||1.81||1.48||1.55|
|Calculated daily intake, g|
|Metabolizable energy, Mcal||6.88||7.02||6.21||6.34|
|Standardized ileal digestible|
aAll diets are limit-fed under thermoneutral conditions. These diets would typically be based on corn and soybean meal fortified with vitamins and minerals. Very low additions
(2%) of supplemental fat may also be included to achieve the indicated energy density. bParity 0 = first gestation period (female has not farrowed a litter); parity 1 = second gestation period (female has farrowed one litter previously). cParity 2 = third gestation period (female has farrowed two litters previously). dAdjust to achieve a desired body condition or weight gain. 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 gestating swinea
|Salt, %||0.4 to 0.6|
|Sodium, %||0.15 to 0.25|
|Chloride, %||0.12 to 0.30|
|Copper, ppm||5 to 20|
|Iodine, ppm||0.15 to 0.50|
|Iron, ppm||80 to 200|
|Manganese, ppm||20 to 45|
|Selenium, ppmc||0.15 to 0.3|
|Zinc, ppm||50 to 200|
|Vitamin A, IU/lb||1800 to 7000|
|Vitamin D3, IU/lb||90 to 700|
|Vitamin E, IU/lb||20 to 40|
|Vitamin K, mg/lbd||0.25 to 3|
|Riboflavin, mg/lb||2 to 8|
|Niacin, mg/lb||5 to 35|
|Pantothenic acid, mg/lb||5 to 20|
|Choline, mg/lb||250 to 500|
|Biotin, mg/lb||0.1 to 0.3|
|Vitamin B12, mg/lb||0.007 to 0.020|
|Folic acid, mg/lb||0.6 to 1.8|
|Vitamin B6, mg/lb||0 to 2.25|
aAll diets are limit-fed under thermoneutral conditions. bMinimum 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. cMaximum legal addition is 0.3 ppm. dMenadione activity.
Table 7. Specific recommended dietary additions of trace minerals and vitamins from concentrates, base mixes or premixes for gestating swinea
|Vitamin A, IU/lb||4000|
|Vitamin D3, IU/lb||300|
|Vitamin E, IU/lb||30|
|Vitamin K, mg/lbe||2|
|Pantothenic acid, mg/lb||10|
|Vitamin B12, mg/lb||0.01|
|Folic acid, mg/lb||0.75|
|Vitamin B6, mg/lb||0|
aAll diets are limit-fed under thermoneutral conditions. bSalt is usually added at the rate of 10 lb/ton in sow 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.
The desired outcomes of a successful gestation feeding program are to develop a large, vigorous litter of pigs at farrowing and properly prepare the sow for the upcoming lactation. To achieve these outcomes, pork producers must establish nutrient needs of sows based on body weight and condition of the sow, expected litter size at farrowing, projected gestational body weight gains, and the environmental circumstances in which the sows are housed. Once nutrient needs of the sows are established, the animal caretakers must ensure that feeding management practices and feeding equipment will deliver the proper amount of feed to every sow.
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3. Noblet, J, Close, WH, Heavens, RP, and Brown D. Studies on the energy metabolism of the pregnant sow: 1. Uterus and mammary tissue development. Br. J. Nutr. 1985; 53:251-265.
4. Weldon, WC, Thulin, AJ, MacDougald, OA, Johnston, LJ, Miller, ER, and Tucker, HA. Effects of increased dietary energy and protein during late gestation on mammary development in gilts. J. Anim. Sci. 1991; 69:194-200.
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Frequently Asked Questions
How can I control weight gain of sows during gestation?
The most common approach is to control the amount of feed offered to sows. This is the most economical approach assuming that a suitable feeding system is in place. However, limit-feeding can cause the development of stereotypic behaviors in sows. An alternative approach is to reduce the nutrient density of the diet so that a larger quantity of feed can be offered. High-fiber ingredients such as wheat bran, soybean hulls, and sugar beet pulp are good choices to dilute diets.
What are the consequences if sows get too fat during gestation?
Fat sows at the end of gestation tend to consume less feed during the subsequent lactation compared to sows in ideal body condition. In addition, fat sows are more subject to heat stress, tire more quickly while farrowing, and are more clumsy in the farrowing accommodations which increases piglet mortality due to crushing. The productive life of fat sows is usually shorter than that of sows in more ideal condition.
When should I increase feed intake for gestating sows?
The largest nutrient demands during gestation occur after day 75 of pregnancy when fetal growth is most rapid. Increasing feed intake during the last 3 to 4 weeks of gestation will support this rapid growth and prevent the sow from breaking down maternal tissues to support this rapid fetal growth. Generally, 1.5 – 2.0 pounds of a typical corn-soybean meal diet will supply the necessary nutrients for fetal growth. Late gestation feed intake increases greater than 2 pounds are not justified.
What are the primary factors influencing nutrient requirements of gestating sows?
Nutrient requirements of pregnant sows can be divided into three components: nutrients to maintain sow body weight, nutrients for the products of conception, and nutrients to support maternal growth. Maintenance of sow body weight is the largest component of the sow’s nutrient needs representing about 75 to 85%. The best way to determine these needs is to weigh sows on a livestock scale. Products of conception (fetuses, placenta, mammary tissues) represent about 15 to 25% of the total requirement. Needs for maternal body growth are the last primary factor influencing nutrient requirements. These needs are greatest for young sows (Parity 0, 1, and 2) as they strive to achieve their mature body weight. Other factors such as housing system, use of bedding material, environmental temperature, and health status can be important factors that either increase or decrease nutrient needs of the sow.
How can I accurately determine body weight of sows?
The best way to determine body weight of sows is to weigh them on a livestock scale. In many operations, there is a common hallway from the gestation area to the farrowing rooms. This is an ideal location to install a scale. With this arrangement, producers can weigh sows as they enter and leave farrowing rooms. These weights provide data to evaluate both the gestation and lactation feeding programs. In the absence of a livestock scale, producers can record a flank-to-flank measurement of sows with a cloth tape measure and use this measurement in an equation to predict sow weight. While not as accurate as a scale, the flank-to-flank measurement is more accurate than visually guessing sow weight.
Can I use synthetic lysine in diets for gestating sows?
Old data generated in meal-fed growing pigs suggested that the efficiency of utilization for crystalline lysine was reduced significantly compared with pigs allowed continuous access to feed. These findings have been extrapolated to meal-fed gestating sows with the interpretation that one should not use synthetic lysine in diets for gestating sows. However, recent data from the University of Missouri indicates that nitrogen balance of sows fed diets containing up to 0.2% synthetic lysine was not different than sows fed control diets with no synthetic lysine. Similarly, nitrogen balance of sows fed diets containing synthetic lysine was not different if they were fed once or twice daily. Nitrogen balance is a research method used to assess the balance between protein deposition and protein mobilization in live pigs. These new data need confirmation with other studies but it appears that one should not automatically dismiss the use of synthetic lysine in diets for gestating sows.
What are the effects of chromium addition to sow diets?
Chromium can be added legally to sow diets up to 200 ppb in the form of chromium tripicolinate, or chromium propionate. Recent data suggests optimal responses up to 600 ppb additions of chromium. Chromium aids in glucose metabolism and seems to potentiate the actions of insulin. Supplemental chromium can increase live born litter size, improve farrowing rates, decrease postweaning interval to estrus, and may decrease sow mortality. Typically, chromium needs to be fed about 6 months before beneficial effects can be documented. The magnitude of response varies across studies and commercial conditions. Consequently, a cost-benefit analysis should be conducted under specific commercial conditions to determine value of chromium additions.
Should gestating sows be fed differently according to parity?
Feeding sows according to parity seems logical. Young sows (Parity 0 and 1) are still growing toward their mature body size and are increasing lean, as well as fat, mass. These young sows are at increased risk of compromised reproductive performance and culling because of their high genetic potential for litter size and milk production and their relatively low voluntary feed intake during lactation. An important goal in feeding young sows is to maintain normal growth in body protein mass by ensuring adequate amino acid intake. In contrast, older sows (Parity 2+) are nearing or have achieved their mature body size. An important goal with these older sows is to control body weight gain by restricting feed intake. This restricted feed intake may not support adequate intake of vitamins and trace minerals. Older sows may require increased concentration of VTM premix in their diets and/or use of more readily available forms of vitamins and trace minerals in their diets to optimize reproductive performance and enhance length of productive life. While these concepts seem intuitive, there is limited data currently available to substantiate this concept. We have provided a range of vitamin and trace mineral recommendations in Table 5. Producers seeking to implement parity-based feeding programs in gestation should consider using the higher end of the ranges provided to supplement diets for older sows.
Can addition of carnitine to gestating sow diets improve performance?
L-carnitine plays an important role in the metabolism of fat in body cells. This role in energy metabolism likely explains the improved gestation weight gain and piglet birth weights observed with feeding L-carnitine to pregnant sows. L-carnitine can also increase litter weaning weights as a result of increased milk production of L-carnitine-fed sows. Some studies have demonstrated increased litter size at birth due to L-carnitine supplementation of gestating sow diets. L-carnitine does not always elicit positive responses in reproductive performance so producers need to weigh the potential economic benefit against the cost of L-carnitine supplementation.
Should I supplement diets for gestating sows with pyridoxine?
The gestating sow’s requirement for pyridoxine is about 1 ppm or 1 mg/day according to the National Research Council. Most diets based on cereal grains and soybean meal contain pyridoxine levels well in excess of this requirement so supplementation of diets based on these ingredients is not necessary. Excessive heating of feed ingredients can destroy vitamin activity. Consequently, if diets contain a high concentration of ingredients that may have been heated excessively (e.g. DDGS and other ethanol coproducts), pyridoxine supplementation may be warranted. Many commercial vitamin premixes will contain pyridoxine as a safety factor to ensure pyridoxine requirements are satisfied.
How many times per day should gestating sows be fed?
Traditionally, gestating sows receive their entire daily allotment of feed in one meal in many confinement operations. Feeding sows in one meal is more convenient for the producer and conserves labor resources. However, the widespread use of drop feeding systems that can easily be automated makes feeding sows multiple times per day possible without significant increases in labor requirements. So, are there advantages to feeding sows more than once daily? From a nutritional perspective, there may be some improvements in efficiency of diet utilization by the sow if she receives multiple small meals compared to one larger meal each day. However, the magnitude of improvement will be rather small since sows are already being limit-fed. Multiple meals per day should create a more constant level of metabolic hormones circulating in the sow’s blood which may translate into improved reproductive performance. However, this concept is yet to be proven in controlled experiments. Limit-fed sows many times develop stereotypic behaviors such as bar-biting, sham chewing, vacuum chewing and nosing the floor or feeder when no feed is present. Some researchers have proposed feeding gestating sows more than once daily so that sows are occupied for more of the day and are less likely to express stereotypic behaviors. However, recent research suggests that feeding twice compared to once daily actually increases time spent in stereotypic behaviors. Other research investigated feeding sows six times daily in group pens compared with twice daily and found no advantages or disadvantages for the more frequent feeding schedule. While anecdotal evidence suggests multiple meals daily are beneficial for gestating sows, there is no data collected under controlled conditions to justify the practice.