How do you look at non-productive days?

March 9, 2015

7 Min Read
How do you look at non-productive days?

We decided to look at how non-productive days are used in record keeping and what effects it has on production numbers. To get the column started we need to understand the definition of a non-productive day.

  • Biological definition: Any day a sow or gilt of breeding age is present in the herd and is not either gestating or lactating.

  • Formula for calculating NPD: NPD = 365 – [(litters/female/year) x (gestation days + lactation days)]

NPD can be broken down into replacement gilt days, weaning-to-event days and returns detected open days.

  • Replacement gilt days: Entry to first service, entry to culling and entry to death

  • Weaning-to-event says: Normal wean to first service, prolonged wean to first service which includes delayed wean to first service and anestrus

  • Returns to detected open days: Detected open and reservice, detected open to death and detected open to culling

For the farms used in the charts and tables below they had to be at 24-plus pigs weaned per mated female per year for the last 52 weeks, and have a mature herd with Parity 0 to Parity 7+ females. That eliminated new start-up farms, repopulations and farms that bring in bred females or open weaned sows. There are 310 farms that meet selection requirements with a mated female population of 624,789 used in the charts and tables.

We know there is a lot of difference farm-to-farm in NPD which is pointed out in Chart 1 (Non-productive Days by Parity) and Table 1 (Non-productive Days). The farms were sorted by pigs weaned per mated female per year so Y-axis in Table 1 is broken down from >=24 pigs by one pigs increment to >=31 pigs with X-axis broken out by parity from P0 to P7+. Chart 1 has the same X-axis of parity with Y-axis broken out by non-productive days starting at 15 to 175 days.

There is one area that jumps out and this is why are NPD for the top farms at >=31 pigs at an average of 162.5 days for P0 females? The range for the farms at >= 24 to 30 pigs for P0 is 70.3 to 100.7 days. We thought the average day for P0 would be lower since a lot of farms enter gilts into the farm when they are bred. Many farms do this to save some money on the cost of their record-keeping program. We feel that there is a lot of valuable information about gilts retention and development lost on farms that do not enter gilts when they arrive on the farm or when the gilt’s development process starts at the farm. Back to those 10 farms at 31+ pigs, what do they know or do in gilt development that gilts are being tracked an extra 60+ days over the average. I know of some of these farms and gilts’ development starts at feeder pig size and this is a high priority area of the operations. Most have built facilities and have dedicated labor involved with developing quality gilts for the sow farm.

In looking at the data from Chart 1 and Table 1, they show a lot of variation in non-productive days between farms. How can you compare farms? The biggest reason the large amount of variation is when replacement gilts are entered. At Swine Management Services to be able to compare farms for NPD we have created a line on the SMS Farm Benchmarking report called Mated Female Non-productive Days. This calculation corresponds to farms that enter gilts into the records at first service. If you look at Chart 2 (Mated Female Non-productive Days by Parity) and Table 2 (Mated Female Non-productive Days), you will see a big drop in average NPD days to 33.3 versus from Table 1 non-productive days of 46.7 days.

For P0 females the drop is from 97.9 to 41.8 days. We like to use this calculation because the manager and the crew are responsible for controlling mated female NPDs versus the NPD calculation which is influenced by when the entry date of replacement gilts is entered. If these gilts are offsite the management of the unit is not responsible.

Chart 3 (Farrow to Farrow Interval by Parity) and Table 3 (Farrow to Farrow Interval): Chart 3 is again set up by parity on X-axis and number of days farrow to farrow, and by pigs weaned per mated female per year on the Y-axis. The average days for the 310 farms were 143.7 days for all parities with range of 141.9 to 145.2 days. The higher average was as expected for P2 females at 146.5 days. From the Top 10 farms at >=31 pigs had P2 average at 142.5 days versus the bottom 45 farms at >=24 pigs at 148.8 days. Those top farms have figured out how to get P1 females to cycle sooner after weaning, have fewer weaned P1 females that do not cycle, do a better job in breeding to get a higher farrowing rate and probably have lower death loss of these younger females. It all starts with gilt development.

The last production area we looked at that effects NPDs is weaning to first service interval. If you look at Chart 4 (Wean to 1st Service Interval by Parity) and Table 4 (Wean to 1st Serve Interval), they show a lot of variation with farms >=31 pigs with average days to cycle for all parities at 4.67 days with P1 females at a low 5.14 days versus P1 average at 7.87 days with the farms >=24 days at 8.67 days. This is a difference of 3.53 days to cycle for P1 females from the >=24 pigs to the top 10 farms >=31 pigs.

Again what are the top farms doing different? Probably feeding sows more feed in farrowing, extra feed from weaning to breeding and, again back to those farms that have made gilt development a priority at the farm, making sure gilts have some skip heat(s) before breeding, crate exposure and weigh at least 300+ pounds before breeding.

In conclusion every farm has NPDs, and the variation farm-to-farm is mostly affected by when replacement gilts are added to the farm sow records. We feel that farms should be entering gilts when they arrive at the farm or when the farm is starting the gilt development process. The data show some of the top farms in the data set at 31+ pigs know that gilt development is a priority at the farm and have invested money and people to developing gilts. If you want to look at comparing farms for NPDs you need to take out the development days for gilts and look at mated female NPDs.

SMS Production Index
Table 5 provides the 52-week rolling averages for 11 production numbers represented in the SMS Production Index. The numbers are separated by 90-100%, the 70-90%, the 50-70%, the 30-50% and the 0-30% groups. We also included the 13-week, 26-week and 12-quarter averages. These numbers represent what we feel are the key production numbers to look at to evaluate the farm’s performance.

At SMS, our mission statement is to provide “Information solutions for the swine industry.” We feel with the creation of the new Farm Benchmarking database we now have more detailed information to share with the swine industry. If your farm would like to be part of the Farm Benchmarking database, or if you have suggestions on production areas to write columns about, please contact us at [email protected] or [email protected].

We enjoy being a part of the National Hog Farmer “Weekly Preview” team.

Previous “Production Preview” columns can be found at

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