Feeding the High Producing Sow

Transcription

1 Feeding the High Producing Sow ESTIMATING ENERGY AND PROTEIN REQUIREMENTS OF THE HIGH PRODUCING SOW John F. Patience INTRODUCTION Much more is expected of the sow today than was the case even a decade ago. We must therefore adjust our sow feeding programs to reflect this fact. One way to do this is to employ the factorial approach, that is to say we define sow nutrient intake on the basis of the factors that influence her requirements: maintenance, maternal growth, litter growth and milk production with fine tuning to reflect additional factors such as housing conditions and parity. This approach offers many advantages. It is less expensive than running a myriad of experiments to assess all possibilities that might occur on individual farms. It provides insight into the individuality of sows and how requirements vary by 20%, 30% or even more on a single farm. It avoids unnecessary over formulation, allowing producers to minimize feed costs while maintaining a high level of productivity. Finally, it allows for further change in the future, as further improvements in performance accrue. ENERGY REQUIREMENTS Energy is required for maintenance, growth to maturity, pregnancy and lactation; growth, however, will not be constant, as the tissue losses that often occur during lactation must be replaced during the subsequent gestation period. Maintenance The maintenance energy requirement is equal to about 110 kcal DE/kg BW 0.75 per day where BW is the sow s body weight. The following table converts actual body weight (BW) to metabolic body weight (BW 0.75 ). A calculator that has the xy key can be also be used (refer to Appendix 1). Thus, a sow weighing 175 kg will have a maintenance energy requirement of 5,293 kcal of DE (digestible energy). Body weight, Metabolic Maintenance kgbody wt. energy requirement BW BW 0.75 Kcal/day , , , , , , ,425 Growth of Maternal and Reproductive tissue Sows in their first through at least their 5th parity are still growing and have not yet reached mature body weight. Thus, energy must be provided to drive this growth. If total weight gain, including sow bodyweight and litter gain is 45 kg, about 1930 kcal DE will be required per day. This will vary from 1430 kcal in early gestation to 2625 kcal in later gestation. This includes 1180 kcal per day for sow weight gain, 550 kcal per day for conceptus growth and 200 kcal per day for mammary tissue growth. During early gestation, only 100 kcal will be required per day for conceptus growth, but this will balloon to 1070 kcal as the farrowing date approaches. The requirement for mammary tissue growth will vary from 150 kcal in the first trimester to 375 on the final day of gestation. The following table illustrates how energy requirements can change significantly depending on body weight and barn temperature. Sow A Sow B Assumptions - Body Weight, kg Housing system Stalls Stalls - Temperature 20 C 15 C Energy Requirement, kcal/d - Maintenance 4,234 5,293 - Temperature 0 1,083 - Body Growth 1,930 1,930 TOTAL REQUIREMENT, kcal/d 6,164 8,306 DAILY FEED REQUIREMENT, kg

2 Cold Stress Assuming no drafts and dry conditions, the lower critical temperature (LCT) for dry sows is 16 C for group housed sows and 20 C for sows housed individually. If barn temperatures fall below these levels, or if drafts or wet floors are present, energy must be provided to allow the sow to keep warm. For every C below LCT, the maintenance energy allowance should be increased by about 4-5%. Behaviour Activity above the basic level will also increase the energy requirements. Things like bar biting can increase energy requirements by up to 20%. Lactation Piglet gain (g/d) X No. piglets/litter X 8 = kcal digestible energy/day This equation assumes that it takes about 4 g of milk to produce 1 g of piglet weight gain and that each gram of milk produced uses 2 kcal of DE from the sow s diet. Individual producers can estimate daily piglet weight gain with only weaning weights to work from. 1. Assume a birthweight of 1200 g per piglet. 2. Subtract this estimated birthweight from the weaning weight. 3. Assume that piglet gain occurs as follows on average: 4-week weaning: week 1: 18%; week 2: 24%; week 3: 30%; week 4: 28%. 3-week weaning: week 1: 25%; week 2: 33%; week 3: 42% The energy requirement for lactation is related directly to milk output. Thus, the energy required for milk production can be estimated according to the following equation: The following table provides examples of piglet gain and lactation energy requirement. WEEK 3 WEEK WEANING 4 WEEK WEANING 9.5 pigs/litter 10.5 pigs/litter 9.5 pigs/litter 10.5 pigs/litter (wean wt.=6.5 kg) (wean wt.=6.2 kg) (wean wt.=7.5 kg) (wean wt.=7.2 kg) Piglet D.E. Piglet D.E. Piglet D.E. Piglet D.E. gain 1 (Feed) 2 gain (Feed) gain (Feed) gain (Feed) , , , ,253 (6.0) (6.2) (5.3) (5.5) , , , ,573 (7.4) (7.6) (6.6) (6.8) , , , ,893 (8.9) (9.2) (7.8) (8.2) , ,453 (7.4) (7.7) AVE: , , , ,293 (7.4) (7.7) (6.8) (7.1) 1 Average piglet gain expressed in grams per day. 2 Digestible energy requirement, expressed in kcal/day, followed by feed intake required, expressed in kg per sow per day, assuming dietary energy concentration of 3,300 kcal DE/kg and a maintenance energy requirement of 5,293 kcal, based on a sow body weight of 175 kg. Estimates assume thermoneutral barn temperatures and no creep feed intake. If dietary D.E. content is 3,100, increase feed allowances by 6.5%. 66

3 While the above example suggests that piglet growth rate declines during the fourth week of lactation, this is not always the case and does vary greatly among sows. This example also indicates that sows producing large, fast growing litters may, depending on feed intake, be in energy deficit, leading to body weight loss. There is very little research to demonstrate how much maternal weight loss is acceptable; estimates range from 180 g/day to 600 g/day. One can estimate that every 100 g of body fat lost provides about 800 kcal, enough to produce 0.6 kg of milk. In summary, energy requirements depend on maintenance requirements, body weight gain and litter gain during pregnancy and on lactation performance during the nursing period. While maximizing feed and thus nutrient intake is essential, in many circumstances, the high producing sow will be in an energy deficit, requiring the mobilization of body reserves in support of milk synthesis. The composition of body weight loss is extremely variable, depending on the relative deficits of energy and protein, resulting in the mobilization of proportionate amounts of fat and lean tissue. PROTEIN AND AMINO ACID REQUIREMENTS Protein is used for maintenance, growth, pregnancy and lactation, with the latter being by far the greatest quantitatively. There is limited information available to accurately model protein and amino acid requirements for the pregnant gilt and sow. Where information is available, it is provided below Maintenance During pregnancy, the maintenance requirement for protein can be estimated as 2.38 g digestible protein per kg BW 0.75 per day. On this basis, maintenance protein requirements will vary from 90 to 150 g of digestible protein, equivalent to about 110 to 190 g total protein per day Pregnancy The protein requirements for pregnancy consist of that for the gravid uterus plus the progressive development of mammary tissue. These two components can be calculated from the following equations: Uterine protein requirements - Protein (g/d) = 3.606e 0.026t Mammary protein requirements - Protein (g/d) = 0.038e 0.059t where t is the stage of gestation expressed in days. It can thus be seen that protein requirements increase towards the end of gestation, just as they do for energy. For example, at day 30 of gestation, the daily protein requirement for pregnancy, including both uterine and mammary tissue, will be 8.0 g while on day 100, the requirement will be 62.4 g. Averaged over the total gestation period, the protein requirement for pregnancy will be about 35 g/d Maternal growth In addition to protein required for maintenance and for tissues related to pregnancy, there will be the requirement for maternal growth. It is very difficult to estimate protein requirements for maternal weight gain, since the ideal gain has not yet been determined and because the rate of lean tissue gain for different genotypes is not broadly known. The following table shows how much dietary protein is required for each function in the pregnant sow and how this can vary with parity. Notice how while the protein requirement for body weight gain declines with parity, there is a reciprocal increase due to the cost of maintaining a larger body mass. The result is that the protein requirement changes very little from gilts to mature sows and is close to 12% crude protein, assuming 2.3 kg daily feed intake. 67

4 Parity Maturity Body protein mass, kg Maintenance, g/d Growth, g/d Uterine/mammary, g/d Total - ideal Total - dietary Lactation Protein requirements for lactation are not well defined, but have been estimated at 100 g total dietary crude protein per kg of milk. Thus, a 180 kg sow nursing a litter of 10 piglets gaining 300 g/d will be producing 12 kg of milk per day and will therefore require 1346 g of well-balanced dietary protein per day. If she is eating 8.0 kg of feed per day, the diet must contain 16.8% crude protein. The following table summarizes the protein requirement of sows of differing body weights producing differing levels of milk. Litter size Sow bodyweight, kg Milk production, kg Week 1 1 Week Assuming piglets gain 185 g/d in week 1 and 310 g/d in week 3. Amino Acids The available lysine requirement for maintenance has been estimated at 49 g/kg BW 0.75 and for lean tissue growth at 70 g/kg. Thus, the available lysine requirement will vary from more than 11 g/d in the young, growing gilt, to as little as 7 g/d in the mature sow. This corresponds to dietary available lysine levels of 0.43 to Assuming 75% availability, total dietary lysine should be 0.60% to ensure the requirement for body growth in younger gilts is being met. The daily lysine requirement during lactation has been estimated at 26 g lysine per kg of littergain. The young gilt, nursing a litter of 10 piglets gaining 200 g/d, will have a total lysine requirement of 54 g/d. If one assumes no maternal body weight loss, then the gilt will require a diet containing more than 0.80% total dietary lysine. If one factors in the contribution of body weight loss, the requirement declines to about 50 g/d, equivalent to a diet containing 0.77% total lysine. Various studies of sows fed different levels of protein conclude that maximizing sow body lean mass 68

5 requires considerably more lysine than merely maximizing litter gain. This exemplified the ability of the sow to feed off her back but begs the question of what our target should be - maximum litter performance or minimum sow weight loss. THE FUTURE The factorial approach to defining nutrient requirements in the sow offers many advantages. However, further research is required to confirm some of the estimates. Most critically, there is a significant need to define the ideal feeding program that maximizes lifecycle productivity in the sow. ACKNOWLEDGEMENTS The equations employed in this article have been extracted from many publications from the United States, Europe and Australia. The author gratefully acknowledges the contributions of these authors. The complete list of references is available by contacting Prairie Swine Centre Inc. APPENDIX I To convert actual body weight (BW) to metabolic body weight (BW 0.75 ). Example Determine the metabolic body weight for a sow that weighs 135 kg type 135; then touch the x y button; then type 0.75; then type =. The answer, 39.61, will appear. Herdsperson Karen Wurtz supervises heat detection of newly weaned sows. 69