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Sow Management and Maximising Longevity

by 5m Editor
18 May 2011, at 12:00am

It is critical for commercial pork producers to identify methods that will result in improved sow productive lifetime of females in the breeding herd, according to Dr K. Stalder, Locke Karriker, DVM, and Dr A. Johnson of Iowa State University in their presentation at the Manitoba Swine Seminar 2010.


Introduction

Profits for pork producers have been limited at best for the past 24 months and there is just beginning to be a glimmer for better returns in the coming months. The profit margins continually cycle from profit to loss periods over time worldwide. Pork producers need to continually identify areas of their operation where improved efficiency can occur in order to remain competitive with other sources of protein in the global market place.

In the past two to three decades, consumer demand for lean pork products has resulted in the buying systems that place financial rewards for improved carcass leanness and muscling or improved lean percentage. During this time period, the methods in which sows are managed and housed have moved towards a more intensive system so that sows can more easily be managed individually. However, recent legislation and marketing decision are changing the way sows will be managed in the future from the current individual sow housing system to one where group housing is utilised. At a minimum, increasing sow leanness, muscling and the utilisation of these different sow housing systems have contributed to reduced sow longevity or sow productive lifetime in commercial pork production systems. A sow remaining in the breeding herd for fewer parities is likely to produce fewer pigs in her lifetime, compared to a sow that remains in the breeding herd for a longer period of time. This reduces the opportunity of a sow to be sufficiently productive (pigs weaned and sold per lifetime) to achieve a return on the replacement gilt investment cost.

It is critical for commercial pork producers to identify methods that will result in improved sow productive lifetime of females in the breeding herd. One area where there is opportunity for improving sow longevity is in gilt selection on the basis of both genotype and phenotype. In order to be able to select for feet and leg soundness, reproductive soundness and other criteria, producers must have a sufficient number of replacements so selection can be practised. This is especially important when producers are using an internal multiplication system to produce their replacement gilts. All too often, producers try to size their gilt multiplication system such that nearly all of the replacement candidates produced is needed to maintain production flow through the system. Thus, sows and replacement gilts having one or more defects or having less than desirable performance values have to be retained as breeding herd females and results in excessive culling / replacement and mortality rates experienced by commercial sow herds throughout the world.

Economic Aspects

Poor longevity or poor sow productive lifetime will have economic consequences for commercial pork producers. Research in 2000 and 2003 by the authors has reported that sows need to remain in the breeding herd for three to four parities before the sow ‘pays for her self’.1,2

At that time, the average producer could receive financial rewards if their herds were productive and they managed input costs and price received for their animals. Since that time, feed costs have risen dramatically and price received for market animals, either finished hogs or weaner pigs, has not kept up with increasing costs resulting in tremendous economic strain and loss of operation equity for most commercial pork producers. To remain profitable, commercial pork producers need to remain highly productive and receive a substantial increase in the price received for the animals they market (Tables 1, 2, 3, 4 and 5). Because the production and economic situations can dramatically differ between different commercial pork production operations, pork producers should calculate when sows in their operation ‘pay for themselves’ using free software from Iowa State University (spreadsheet can be found by clicking here).


Table 1. Assumptions used to determine the parity when a sow reaches positive net present value under current market conditions.


Table 2. Operation fixed and variable financial assumptions used to determine the parity where a positive net present value is attained.


Table 3. Assumptions used to determine the parity when a sow reaches positive net present value under current feed cost.

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Table 4. Net present value by parity when the price received per hundred weight varies from the original 44.00 assumed value.

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Table 5. Net present value by parity when feed price varies from the original 76.00 per market animal varies.

High replacement rates result in the need for larger replacement gilt pools, regardless of whether a pork production system raises or purchases these gilts. Furthermore, producers incur additional expenses associated with developing and acclimating replacement gilts and when all gilts entering the gilt development unit (GDU) do not end up in the breeding herd which results in additional costs to the system. In some cases, poorer maternal production from younger sows, while not a direct out-of-pocket expense, will reduce the gross income of a swine operation when compared to the production of more mature sows.3 Additionally, there is a disease risk whenever animals are introduced in the breeding herd. Reducing the number and frequency of animal introductions can reduce this risk of introducing diseases not currently present in the breeding herd. Finally, the offspring from gilts have greater mortality and reduced performance during the nursery and the grow-finish periods.

Reasons for Culling and Mortality

Reasons for culling can differ based on which parity of female is evaluated.4 These results have been confirmed with more recent popular press data5 in addition to a review of production data from the past 12 months. These more recent data still point to the importance of a number of factors that consistently impact culling decisions for breeding herd females in commercial pork production operations.

Reproductive failure remains the leading reported cause for sow removal from the breeding herd in commercial swine herds. The difficulty with reproductive failure is that it encompasses numerous traits including failure to cycle, failure to cycle in a timely manner, failure to conceive, abortions, and not in pig at the time a sow is placed into the farrowing crate. All reproductive failures are costly for commercial pork operations. Feeding a sow for the entire gestation period and then finding her not in pig at this production stage results in the accumulation of a large number of non-productive days and a very large feed bill. As corn and other feed ingredients increase in cost, these breeding management mistakes become more costly.

Reproductive failure remains the leading reported cause for sow removal from the breeding herd in commercial swine herds. The difficulty with reproductive failure is that it encompasses numerous traits including failure to cycle, failure to cycle in a timely manner, failure to conceive, abortions, and not in pig at the time a sow is placed into the farrowing crate. All reproductive failures are costly for commercial pork operations. Feeding a sow for the entire gestation period and then finding her not in pig at this production stage results in the accumulation of a large number of non-productive days and a very large feed bill. As corn and other feed ingredients increase in cost, these breeding management mistakes become more costly.

The challenge with reproductive failure as a culling or removal reason is that the majority of the studies examining culling reasons have been done by a prospective analysis of existing record keeping systems. In the analysis of prospective data, it is often difficult to ascertain whether a recorded culling reason is the actual reason for a sow being culled from the breeding herd or is the reason indicated because it is the last in a cascade of events that resulted in a sow being culled from the breeding herd. Furthermore, a recent published study6 evaluated the accuracy of culling codes on commercial sow herds. In that study, over 25 per cent of recorded reasons for culling were determined to be inaccurate. Given the relatively large error rate in determining actual causes for culling, it is difficult for scientists, practitioners, farm management and barn workers to identify potential causes and most importantly identify potential mitigation strategies that will improve culling / replacement rates to more acceptable levels.

The second most common reason for culling is for feet and leg soundness or lameness issues. Feet and leg soundness, locomotion problems and claw disorders can be major contributors to poor sow longevity. A more detailed discussion of feet and leg structural soundness is provided in the Pork Industry Handbook factsheet PIH-101.7 Leg weakness accounts for a great deal of culling and replacement in first litter sows.8 Soundness or leg weakness has been shown to be under at least some genetic control. The heritability for various leg soundness scores range from 0.01 to 0.47, with some values greater than 0.15. This indicates that structural soundness can be improved through proper genetic selection. 9,10

Improving Sow Productive Lifetime

Leg soundness has been shown to influence sow longevity. Sows with poorer leg soundness scores have been shown to exit the breeding herd earlier when compared to sows with better soundness scores.11 This work demonstrated that sows having soundness scores lower than 3 (1 to 5 scale with 1 being the poorest and 5 being superior soundness score) appear to have a relatively higher risk of being culled when compared with sows with superior soundness scores (Figure 2).

The difference in risk of being culled between soundness scores 3 and 4 was clearly smaller in the present study. It is clear that leg soundness contributes to sows exiting the breeding herd earlier than desirable. This is particularly evident when examining culling reasons by parity.

The two main reasons that young sows leave the breeding herd are 1, reproductive failure and 2, lameness or leg soundness problems.4,5

Our earlier work12 and work at other institutions13 support the findings that several leg traits impact sow longevity. Leg traits that have been demonstrated to adversely impact sow longevity include buck kneed front legs, up-right rear pasterns (animals appear to be post-legged) and swaying hind quarters. Whereas several traits negatively impact sow longevity, it has been shown that soft or weak pasterns on the front legs is associated with sows that remain in the breeding herd for a longer period of time than sows having other structural conformation types on the front and rear legs.

Being able to identify replacement gilts and make the correct selection decision is critical to improving the overall sows’ leg conformation in producers’ breeding herds. Further, an extensive evaluation of cull sows at harvest revealed that sows having at least one foot or leg with some sort of lesion is greater than 80 per cent.14 It is unclear whether all of these leg and foot defects are the result of a sow’s poor leg conformation. It is likely that the abrasions observed contributed at least at some level to a portion of the sows leaving the breeding herd earlier than what is desirable.

It should be noted that virtually all of the studies have identified large farm/year environmental effects. This is indicative of management factors that occur on the farm and environmental factors that have a large impact on the longevity of sows in individual herds or produced during specific time periods within and/or across herds.10 The sow’s parity of origin tended to impact the sow’s length of productive life in the breeding herd. Sows that are born to females in their third, fourth and fifth parities tended to remain in the breeding herd longer when compared to sows that were born to females in their first, second, and sixth parities.15 In that same study, the age at first farrowing and the litter size in which the sow was born was investigated to determine if these traits impact the sows’ length of productive life. Age at first farrowing impact on the risk of being culled in the present study was highly significant (P<0.001).12 The greater the age at first farrowing, the greater the risk of a sow being culled.

In addition to phenotypic or genetic traits that are evaluated on the replacement gilt, molecular traits are becoming more and more important in improving many economically important swine production traits. Studies conducted at Iowa State University have identified several markers that potentially could be useful in improving feet and leg soundness, lifetime productivity and other traits related to improving sow productive lifetime.

Selection programmes employed by most breeding organisations have ignored structural soundness in recent years, while more emphasis has been placed on other economically important production traits. Ignoring structural soundness has resulted in an increased number of animals having one or more structural problems. Research work has demonstrated that selection for leanness or lean gain will result in a deterioration of leg soundness in pigs. Whether you are purchasing gilts or raising your own replacement females in an internal multiplication programme, all replacement females should be visually evaluated. A series of posters and a pocket guide have been developed through cooperation with the National Pork Board and the National Hog Farmer magazine that should help producers identify gilts with structural problems and those that are more ideal.17, 18, 19, 20 Phenotypic evaluation becomes particularly important as replacement rates and mortality among breeding herd females are at levels where improvement is needed.

Producing Replacement Gilts

The ability to perform selection for phenotypic traits as well as selection that results in genetic improvement of economically important traits requires a gilt pool that is sufficiently large enough to allow strict selection practices. This is particularly true when a producer is producing their own replacement gilts through an internal multiplication programme.

It is critical that this multiplication programme be appropriately sized so that selection can occur. The current replacement rate determines the proportion of production devoted to producing replacement gilts. The multiplication system should be sized for the period of greatest replacement demand; typically the summer time is when the largest numbers of gilts are needed. During the rest of the year, a producer can place even greater selection pressure or be choosier with the replacement gilts produced and hopefully enhance the productivity and longevity of their herd.

In addition to the replacement rate, sizing the multiplication portion of the herd is dependent on the number or proportion of selectable gilts produced from each maternal litter.

Further, the replacement rate of the grandparent females is also an important component for appropriately sizing the gilt multiplication portion of the herd. Based on these criteria, the proportion of the herd devoted to producing replacement parent females can varying substantially. The genetic supplier should be capable of assisting producers with sizing multiplication programmes. However, producers should error on the side of slightly over-sizing the multiplication programme to be sure that sufficient gilts are produced so that selection can occur for the various important traits. If insufficient replacement gilts are produced, then little if any selection for feet and leg soundness or any other trait can occur. If this happens, it is unlikely that the replacement/culling rate can improve in a herd where these values are of concern. If gilt numbers are sufficiently small, then producers often begin selecting younger and younger gilts to enter the GDU or what some term the internal multiplication ‘death spiral’.

Human Influence

As is the case with a variety of production systems, the influence that the stockperson has on sow productive lifetime should not be ignored. Many of the traits contributing to culling or improving culling, mortality and replacement rates depend on the skills of barn workers or stock people. Since we are relying on a work force that has less livestock experience than we may have had in the past, it is critical that stockpersons have three essential skills to be successful (Jones, personal communication). These include:

  1. The eyes that see or good observation skills to identify problems in the production system. This skill is necessary to identify the sick animal or when feed or water delivery system may not be functioning correctly or some other problem.
  2. The knowledge to know what to do once a problem has been identified. This can be as simple as reporting a problem to the manager or knowing where to find the correct fix for a given problem, and
  3. An action attitude or what I call ‘the get after it’ attitude. If a stock person has the observation skills and possesses the knowledge to fix or address a particular problem accurately and they do not have the action attitude, the system will still fail.

These three critical skills are necessary for a successful stock person.

It has been demonstrated that replacement rates may increase as herd size increases.21 While there may be numerous reasons for this, one plausible reason is that as herds become larger, stockpersons have less time to observe individual animals to identify potential problems. This problem could become even more exacerbated as we move from gestation stalls, where animals can be easily observed on an individual basis, to group sow housing where individual observation will likely be more difficult. Great caution should be exercised in the group sow housing setting where observation deteriorates to the point where only severely injured or sick sows are identified. Developing stock person routines that allow for individual animal observation and early detection of sick and/or injured animals will be necessary and a requirement of many animal welfare programmes.

Summary

Sow productive lifetime is influenced by many factors that are influenced by genetics and the environment. Many important factors such as body condition could not be covered in this paper because of time.

A focus on three areas that can contribute to reduced sow productive lifetime but are often overlooked are discussed. The focus areas included in this paper include feet and leg soundness, producing sufficient number of replacement gilts, and the influence of stockperson skills and their influence on sow productive lifetime.

It has been demonstrated that selection can be effective in improving feet and leg soundness in order to improve sow productive lifetime. Many traits are genetically correlated with sow productive lifetime and can be improved through selection. Molecular genetics could supplement traditional selection in order to improve traits such as sow productive lifetime and related traits like feet and leg soundness for faster improvement than by selection alone.

All candidate replacement gilts should be systematically evaluated for reproductive and structural soundness as well as have acceptable growth, backfat, and loin muscle area values. Additionally, replacement gilt production should be adequately sized so that real selection for the various important traits can occur whether gilts are purchased or produced in an internal multiplication programme.

Finally, the effects that people have on any production process including pork production cannot be ignored. Stockpersons must have the skills and the education they need to be successful in producing pork profitably.

References

  1. Stalder, K.J., R.C. Lacy, T.L. Cross and G.E. Conatser. 2003. Financial impact of average parity of culled females in a breed-to-wean swine operation using replacement gilt net present value analysis. J. Swine Health Prod. 11:69-74.
  2. Stalder, K.J., R.C. Lacy, T.L. Cross, G.E. Conatser and C.S. Darroch. 2000. Net present value analysis of sow longevity and the economic sensitivity of net present value to changes in production, market price, feed cost, and replacement gilt costs in a farrow-to-finish operation. Prof. Anim. Sci. 16:33-40.
  3. Lucia, T., G.D. Dial and W.E. Marsh. 1999. Estimation of lifetime productivity of female swine. J. Amer. Vet. Med. Assoc. 214:1056-1059.
  4. Dagorn, J. and Aumaître, A. 1979. Sow culling: Reasons for and effect on productivity. Livestock Prod. Sci. 6:167-177.
  5. Miller, D.P. 2002. Data Pinpoints Sow Dropouts. National Hog Farmer Magazine. Penton Media, Inc. Minneapolis, MN 55425 Accessed 19 November 2007.
  6. Knauer, M,L.A. Karriker, T.J. Baas, C.J. and K.J. Stalder. 2007. Accuracy of sow culling classification reported by lay personnel on commercial swine farms. J. Amer. Vet. Med. Assoc. 231:433-436.
  7. Wood, C.M. and M.F. Rothschild. 2001. Feet and Leg Soundness in Swine, In: Pork Industry Handbook, Purdue University, West Lafayette, IN, Factsheet PIH-101.
  8. Douglas, R.G.A. and J.D. Mackinnon. 1993. Leg weakness in weaned first litter sows. Pig Vet. J. 30:77-80.
  9. Serenius, T. and K.J. Stalder. 2006. Review: Selection for sow longevity. J. Anim. Sci. 84(E. Suppl.):E166-E171.
  10. Stalder, K.J., M. Knauer, T.J. Baas, M.F. Rothschild and J.W. Mabry. 2004. Sow Longevity. Pig News and Information. 25:53N-74N.
  11. Serenius, T., and K.J. Stalder. 2007. Length of productive life of crossbred sows is affected by farm management, leg conformation, sow’s own prolificacy and sow’s origin parity and genetics. Animal. 1:745-750.
  12. Serenius T., K.J. Stalder and R.L. Fernando R.L. 2006a. Genetic associations of length of productive life with age at first farrowing and leg soundness score in Finnish Landrace population. Proceedings of the eighth world congress on genetics applied to livestock production. Belo Horizonte, Brazil, CD-ROM communication 06-08.
  13. Jorgensen, B. 1996. The influence of leg weakness in gilts on their longevity as sows, assessed by survival analysis. In: Proceedings of the Nordiska Jordbruksforskares Forening Seminar 265-Longevity of Sows. Ed. V. Danielsen, Denmark: Research Centre Foulum, pp. 95-100.
  14. Knauer, M, L.A. Karriker, T.J. Baas, C. Johnson and K. J. Stalder. 2007. Accuracy of sow culling classification reported by lay personnel on commercial swine farms. J. Amer. Vet. Med. Assoc. 231:433-436.
  15. Mote, B.E., K.J. Koehler, J.W. Mabry, K.J. Stalder and M.F. Rothschild. 2009. Identification of genetic markers for productive life in commercial sows. J. Anim. Sci. 87:2187-2195.
  16. Fan, B., S.K. Onteru, M.T. Nikkilä, K.J. Stalder and M.F. Rothschild. 2009. Identification of genetic markers associated with fatness and leg weakness traits in the pig. Anim. Gent. 40:967-970.
  17. Stalder, K.J., D.P. Miller, C. Johnson, T.J. Baas, N. Berry, D. West and A.E. Christian. 2005. Reproductive trait selection guidelines poster. National Pork Board, Des Moines, IA.
  18. Stalder, K.J., D.P. Miller, C. Johnson, T.J. Baas, N. Berry, D. West and A.E. Christian. 2005. Feet and leg disorders poster. National Pork Board, Des Moines, IA.
  19. Stalder, K.J., D.P. Miller, C. Johnson, T.J. Baas, N. Berry, D. West and A.E. Christian. 2005. Conformation, structural soundness guidelines poster. National Pork Board, Des Moines, IA.
  20. Stalder, K.J., C. Johnson, D.P. Miller, T.J. Baas, A.E. Christian, N. Berry, and T.V. Serenius. 2005. Pocket guide to structural, feet and leg, and reproductive soundness. National Pork Board, Des Moines, IA.
  21. D’Allaire, S., Morris, R.S., Martin, F.B., Robinson, R.A. and Leman, A.D. (1989) Management and environmental factors associated with annual sow culling rate: A path analysis. Prev. Vet. Med. 7:255-265.

Further Reading

- You can view other papers presented at the Manitoba Swine Seminar 2010 by clicking here.


May 2011