How many breeding females do I breed this batch?

• The aim of efficient pig farming is to maximize the pounds output of pig meat from the farm to provide safe, high quality and consistent pig meat for consumption. In order to efficiently farm both the pig and any health issues, all-in/all-out farming has to be practiced. However, many pig farmers claim to do 'all-in/all-out', but when their operation is examined in any detail they are found to only give all-in/all-out lip service at best.
• A major reason for lack of all-in/all-out in the grow/finish herd is variable weaner input which causes stress on the farm. This is particularly evident in farrow to finish family units.
• Examination of the breeding records reveals the underlying cause of the problem- breeding targets are not being met, or even has not been set.

Table 1
Sixteen weeks worth of breeding records with results

• On many of these farms, when the stockpeople are asked "how many breeding females did you breed this week?"
  • The answer is: "depends on how many were in heat!"
• In itself this statement is true but shows no concept of the farm's actual requirement.
• To manage pig health effectively it is necessary to decide what the end points of production are and then plan the farm backward to achieve this output target. There are eight production questions to ask before an effective pig flow model can be designed. To demonstrate the concept an example farm will be utilized.

Example farm:

1. What is the batch unit of time?
   • The batch unit is the basic time interval by which the all-in/all-out will be governed, for instance, weaning occurs on this farm every Thursday, therefore this produces a weekly (7 day) batch size.
2. How much space is available in the finishing unit?
   • Measurement of the pens reveal there are 12764 sq feet of unobstructed floor space for the pigs.
     Note: this does not include feeder space or the passageways. The passageway is an area of intense debate on many farms, as utilization may be necessary to comply with current swine care stocking rate suggestions.
3. What is the growth rate of pigs from 66lbs to 250lbs?
   • The farm generally has a good growth rate. The average 66lbs pig is 10 weeks old and the average 250 lbs pig is 26 weeks old. Giving a difference of 16 weeks. If we allow one additional week for tail enders to grow on and a day for cleaning, 17 weeks are required to take each weekly batch of 66lbs pigs to 250lbs.
4. What is the space requirement for a 250 lbs pig?
   • European Union Directive 91/630 EEC lays down minimum standards for the protection of pigs, an average pig greater than 85 kg (187 lbs) but less than or equal to 110 kg (242 lbs) must be provided with 0.65 m2 (7 sq feet) of unobstructed floor space. There is no equivalent legislation in the US. However, the Swine Care Guide (NPB 2001) suggests 8 sq feet for a finished pig. Therefore, when 12784 sq feet finishing space is divided into 17 weeks of batches, this results in 752 sq feet per weekly batch. Because the farm adopts strict all-in/all-out and each pig requires 8 sq feet this provides sufficient space for 1598 grow/finish pigs (66 to 250lbs).
      
   Table 2
   Stocking rate regulations:
    

   EU Legislation 91/630		Swine Care Manual  (NPB 2001)
   Average Weight of pig kg	Minimum Space requirement m2	Weight of pig lbs	Suggested floor space sq feet
   ≤ 10 kg	0.15	12-30	1.7-2.5
   ≤ 20 kg	0.20	30-60	3-4
   ≤ 30 kg	0.30	60-100	5
   ≤ 50 kg	0.40	100-150	6
   ≤ 85 kg	0.55	150-Market	8
   ≤ 110 kg	0.65
   > 110  kg	1.00
   1 kg  = 2.2 lbs	1 m2 = 10.76sq feet	1lb = 0.454 kg	1 sq foot  = 0.0929m2

    

5. How many pigs are sold each batch?
   • With 752 sq feet unobstructed floor space per finishing room, this provides enough room for 94 pigs a week is be sold.
     If 94 finished pigs are sold each week at 250 lbs live-weight, which on this farm, equates to 180 lbs dead weight, a true production target can be achieved.
     The major production target for this family unit should be to produce:
     16,920 lbs of bacon each week, 52 weeks of the year, 879,840 lbs of bacon annually.
6. What is the post-weaning mortality?
   • This unit has over the last year experienced a 7% post-weaning mortality.
     Therefore, 94 pigs finished divided by 7% post-weaning mortality equates to 100 pigs a week weaned.
7. How many piglets are weaned per crate per week?
   • Currently the farm is producing approximately 10 piglets weaned per sow, Table 1. However, this is not quite the same as number weaned per crate but is a good starting point.
     Therefore 100 weaned piglets are required each weekly batch with 10 piglets per crate, indicating 10 crates per week is required to be filled.
8. How many breeding females do I breed each week to achieve 10 to farrow?
   • This depends on the current farrowing rate. The analysis of the 16 weeks of production indicates an 83% farrowing rate, therefore 10 divided by 0.83 indicates the farm needs to breed a minimum of 12 breeding females.
      
   Table 3
   Number of breeding females required to be bred to
   achieve 10 per batch to farrow.
    

   Current farrowing rate %	Number to breed
   100	10
   91	11
   83	12
   77	13

   The pig flow calculator using these 8 questions

How do I obtain 12 breeding females per week?
 

• 10 may come from the farrowing house (depending on culling policy)
• 1 or 2 from the gilt pool
• 1 is likely to come from an 18-28 day repeat.

• This represents 10/12 (83%) of the potential breeding females. It is imperative that as many of these sows are re-bred. Sow culling policy may need to be re-considered in terms of the farm's output rather than the sow's individual attributes.
• For example a particular sow has produced 6 piglets born alive and is a parity 7 sow. On a number of farms she is destined to be culled. So on the day of weaning she is moved into the culling pen and is not re-bred. If this means that the other 9 sow's cycle, together with one return and one gilt, 11 breeding animals have been bred: - you are planning for a 90% farrowing rate from this group.
• The sow intended for culling invariably cycles on the Tuesday, but is not bred.
• The normal events occur and out of the 11 sows bred, 9 farrow. This has just cost the unit 10 piglets weaned, a total potential loss of 2500 lbs live weight (about 1800 lbs dead-weight). This is a real loss because the crate will be empty for 5 weeks assuming the farm is true to all-in/all-out and if properly budgeted has no extra sows anyway.
• If the sow intended for culling had been bred and farrowed with only 6 piglets again, we have only lost 4 weaners, but at least have 6 spare teats to suckle any extra piglets and are more likely to wean 100 piglets from the 10 crates, than if only 9 sows farrowed.
• It is a more real to consider that for every empty farrowing crate 10 potential piglets weaned are lost. For each empty crate add 10 to the pre-weaning mortality and calculate your real financial pre-weaning mortality rather than farming to keep the computer happy.
• Therefore, wherever possible breed all sows which are weaned (common-sense must prevail). If the sow is slightly lame breed her by AI only (a boar must never breed a lame sow/gilt) and then place her on bedding. It is surprising how many mildly lame sows self-cure. If you are concerned ask for your veterinary surgeon?s advice.
• However, you must still have a culling policy. Because the farm's aims have shifted to have 10 sows to farrow each week, culling has only been delayed. There are two major options:
  
  1) Cull at the end of the breeding week:  If 2 gilts cycle and thus 13 breeding females cycle and are bred during the service week, cull any excess sow at the end of the breeding week.

  2) Cull once pregnancy has been determined in at least 10 sows:  An alternative is to delay culling until pregnancy checking (around 28 or even 35 days). This insures the farm until most of the returns have been detected. This method is more accurate, but does rely on accurate pregnancy detection. A real time scanner can take these loss days down to 21 days and still have better accuracy than a Doppler machine.
   

• Estimation of additional costs:
  • Feed and housing cost $0.50 per day/sow 35 days = $17.50 (28+7 days)
  • Breeding costs at about $5 per service @ 2 services/sow = $10
  • Total costs = $27.50 per additional sow
• Potential loss:
  • If we assume an income of 46c per lbs and 10 pigs sold at 180 lbs dead weight this would equate to $828 loss of income. However, the income from pigs fluctuates wildly. The cost of pig production varies less. If a cost of production of 40c per lb is assumed the farm has not covered $720 of costs. However, a major cost involved in producing pigs is feed at 60 %, and if these pigs were not born the $432 of feed costs would not have been incurred. The other costs, on the other hand, are likely to be incurred whether these pigs exist or not and this equated to a loss of $288 per farrowing crate empty. This is 10x the cost of keeping an insurance breeding female for 28 days.
  • However, a sow culled at 28 days post-breeding is likely to be in a better body condition than she was at the point of weaning and a pregnant sow is a better converter of feed than a non pregnant sow, so some of your $27.50 costs will be returned as an increase in the sow's body-weight. Also consider that on many farms sows are rarely culled immediately after weaning, their actual exit date will be determined by size of cull group/ market forces/ vehicle availability, and all the time she is eating feed.
  • In practice there is a genuine welfare benefit of keeping sows wherever possible for 28 days post weaning to allow for any shoulder sores to heal, stiffness of resolve and any poor body condition to be corrected. Any old time farmer will tell you that a pregnant sow is a better feed converter than a non-pregnant sow. Therefore, delay culling and breed all intended to be culled sows. At 35 days post weaning (28-30 days post breeding) review the intended to cull sows, assuming the batches pregnancy targets have been met, then the animals intended to be culled can be culled, if the batches pregnancy target has not been met, a management decision has to be taken, compare the value of the cull animal over the production loss from an empty farrowing crate.

• Several questions have to be asked regarding gilt pool management:
  - How often are gilts ordered?
  - Were any calculations made to determine this batch's actual gilt requirements?
  - Is a minimum number of gilts ordered?
  - Are gilt requirements discussed regularly enough with your local breed company representative?
• Gilt pool management in the example farm requires at least one gilt a week to cycle.
• This particular farm practices a 6 week gilt introduction program and gilts are bred at their second heat, 9-10 weeks post arrival.
• If gilts are ordered as a monthly order (as is standard practice) how many gilts do I order a month?
• The number should be determined by the requirement in 10 weeks time. This is possible to estimate with accuracy using the breeding Csum as shown on the next page.
• Any reduction in the number of breeding females is represented in bold and ideally a different color. When the remaining number of pregnant animals fall below the target change color again to emphasize to all staff the importance of the event. A basic form of Csum is available on many pig computer programs, but generally do not go far enough, i.e. do not go through lactation to the next breeding date.
• The current week is week 27, i.e. so far no breeding animals have been bred.
• View Breeding Csum to assist pig flow and predict gilt purchases graph

• In week 1, an ideal week, one sow returned, none of the sows have any noticeable problems at 10 - 14 weeks of gestation (i.e. age, legs, and teats); at least one gilt is required.
• In week 2, two sows returned and at week 10 one sow was noticed with chronic mastitis and would be destined to be culled, if possible, at least two gilts required.
• In week 3, while 12 sows are bred, 12 sows are pregnant at 28 days of gestation; one sow is selected for culling. At least one gilt is required.
• In week 4, only 10 breeding females are bred, so even in week 1 it is known that extra gilts will be required. Two additional sows return and only 8 breeding females are found in-pig at 28 days. In-order to ensure that sufficient breeding animals are presented in the required breeding week at least 3 gilts are required to be ordered. Note the color changes again the record a week when production is below required.
• In week 5, while 11 sows are recorded pregnant at 28 days, two abort in week 10. While budget farming cannot provide sufficient leeway for all eventualities, the effect of the abortions on the farm's budget only need to last one production cycle. Additional gilts are ordered to stabilize production. At least 2 gilts are required.
• Weeks 6 onward indicate the progression of the Csum over the weeks, clearly indicating the number of breeding females bred, the time of their loss and sows/gilts expected to farrow.
• Culling at 28 days post-breeding may affect the farrowing rate and so adjustments after 28 days must be made. On many computer programs, there is a category ?sold for breeding? which will then recalculate the farrowing rate based on bred expected to farrow.
• If the close attention to details described here, is not practical, as few sows drop out after week 10 it may be better to maintain a larger gilt pool of at least 12-14 gilts to allow for anoestrus and breeding company availability, to safeguard your breeding target.
• If the farm suffers from seasonal infertility/abortion problems, plan these problems into the gilt management program. In July/August/September order and breed extra gilts to compensate for the inevitable 10% reduction in farrowing rate.
• Gilts need to be regulated as well. For buying 10 gilts in one batch, and they all synchronize and cycle in the same week is not what is required. However, this is one of the commonest reasons for excessive numbers of breeding females being presented to the farrowing house. Purchase gilts in small enough groups, but watch that
• Transportation costs do not become prohibitive. Alternatively purchase gilts of different weights, for instance at 190 and 210 lbs to encourage a two week spread. Some farms even purchase at three weights, 165, 190 and 210 lbs when purchasing every 6 weeks.
• As a last resort, if gilts are not available, select you own from the finishing herd and cull later when replacements are found.

• The re-breeding of repeat animals has to be approached with caution, however, on many farms 10% of all bred animals will repeat and on this farm this would equate to approximately one sow per week. Generally it is uneconomic to re-breed 2nd repeat breeders. Likewise animals with a 14-21 day post-service vulval discharge should be culled and not re-bred.
• Because the farm output is determined by the 10 farrowing crates, producing 100 weaners; sow's which have poor weaning numbers or damaged teats are more likely to be culled than animals for age or even sub-optimal litter size born.

How many pregnant animals do I cull at 28 days?

• Each farm needs to review its circumstances, for example gestation accommodation. Farms adopting budget farming commonly used 110% farrowing crate capacity as the number of pregnant animals to present for farrowing. In the example farm sows should be culled back to 11 pregnant females per week. It is always possible to move 10 sows into the farrowing accommodation with 1 sow remaining in the breeding barn. When a couple of sows have farrowed, wean one sow; distribute her piglets to the other sucking sows. Move the weaned sow back into the breeding barn and the expectant sow into the vacant crate. This is acceptable because the farrowing output requirement is 100 pigs, 10 per crate, not 10 per sow.

Implications of this pig flow farming system:

1. Better health management as overstocking and understocking is reduced
   • A farm planning to wean 100 pigs a week will needs 300 sq feet of hot nursery a week, if pig flow is from weaning to 66lbs, each 66 lbs pig requires 3 sq feet and 98 pigs move out of the accommodation (2% nursery mortality ? strictly only 294 sq feet required). As a 66 lbs pig is reached at 10 weeks of age seven nursery rooms are required.
   • The implication of this is that if table 1 (breeding results) is a reflection of production, 4 weeks out of the 16 the farm over-produced weaners and since weaner accommodation is static, these weaners would be overstocked, contra to stocking rate suggestions. Likewise 9 out of 16 weeks the weaners were under-stocked, making ventilation management more difficult.
   • The reduction in disease has been worth a reduction in days from birth to finish of 15 to 20 days.
   • The improvements associated with good pig flow and disease management are:
     • Increased pig feed intake ? as there is less anti-nutritional stress factors
     • Increased average daily gain ? as there is less disease to fight
     • Improved feed efficiency ? which is a function of the last two improvements
     • Reduced mortality in the nursery, growing and finishing phase
     • Reduces the number of run off pigs as there is less disease challenge
     • Because of higher health status there is a reduction in the number of treatments and medication which helps to cut the animal health and labor effort/cost
     • Improved bacon quality by lowering the risk of antibiotic residues and abscesses
     • If disease occurs, management of the problem is easier as the farm is more predictable.
2. Organized farm building/plan
   • With 21 day weaning and 10 sows a week to wean, weaning once a week on a Thursday, equates to a 4 week turn around (28 days). Therefore, 40 crates are required in 4 groups of 10. On small farms which have grown with time, this might mean two rooms in a weeks batch, one with 6 and another with 4 farrowing crates.
   • The farm layout is demonstrated in figure 2.
   • The budget farming of each area of the farm obviously has implications if disease, poor growth and seasonal variations occur. Some of these can be built into the system by providing additional accommodation, but the cost of these implications has to be assessed first.
3. Maximizes output without contravening current swine care standards
4. Allows easier cost analysis
   • The farm performance and costs can be assessed, based on the farm's optimum/maximum output from the finishing floor. Therefore, the cost of output will determine profitability, and the cost of production can be assessed by factors which affect output. For example:
     • Increase in farrowing rate - fewer breeding females are needed on the farm
     • Increase in numbers weaned per crate - fewer breeding females are needed on the farm
     • Improvement in growth rate - reduction in finishing space required or an increase in killing weight
     • Decrease in post-weaning mortality - fewer breeding females are needed on the farm
5.  A change in producers attitudes towards recognized targets is required
   • A change in producer?s attitudes is required, to move away from non-output targets. For instance targets which are less important to budget farming when compared to current farming systems:
     • Monthly figures (a month is a variable time interval and unsuitable as a batch unit of time)
     • Pigs produced per breeding female per year (gives no indication if batch sale targets are being reached)
     • Quarterly farrowing rate (fails to allow adequate attention of reproduction management)
     • Pre-weaning mortality (numbers weaned more important)
     • Herd size (the herd size should vary to accommodate seasonal breeding requirements)
     • Non-productive sow days (a good cost implication, but only important once output target has been achieved. Producers too concerned with NPD may miss output targets or fail to batch adequately).
6. Allows for batching and all-in/all-out around any unit of time.
   • The are farms practicing weaning every day of the working week. On other farms they practice batch farrowing, every 2 or 3 weeks with sows being bred, farrowed, weaned and ultimately finished over 2 or 3 weeks to ensure all-in/all-out by finishing air space and to increase the size of the groups.

• The basis of pig flow farming can be summarized as:

  Plan your Farm
  
  and then
  
  Farm your Plan
   

   

Pig Flow models

Basic pig flow