Total Born and Stillborn by Parity and Gestation Length

Total Born and Stillborn by Parity and Gestation Length

We decided to look one more time at the effect of gestation length on two more production areas: total born and stillborns. In the past, gestation length data was altered by many farms that were inducing sows to farrow. Inducing started as low as day 113 and has risen to 115+ days. The 18 farms we used for the data set do no or minimal inducing. The selected farms for the last three years were at 24-plus pigs weaned per mated female and had farrowing rate at 85+%. There were 303,980 farrowing from these farms over a three-year period that was used. There were multiple genetic companies represented by the 18 farms.

Taking a look at total born per female farrowed, first you need to refer to Chart 1 and Table 1. Remember that total born equals pigs born live plus stillborns plus mummies. Chart 1 is laid out with gestation length on the X-axis with a range of <=110 days to >=122 days in length. The Y-axis has total born per female farrowed starting at eight up to 16 pigs. The data on the chart is broken out by parity with parity 1-7 and 8+. In looking at the data you can see that total born is affected by both short and long gestation lengths, with most parities with the highest total born has gestation lengths of 112 to 114 days. There was a drop in total born as days of gestation increased from 114 days. We were surprised to see the peak for total born at 114 days of gestation.

As we thought through it we realized that sows farrowing larger litters usually farrow earlier due to the larger amount of hormone produced by more pigs that start the farrowing process. In Table 2 for those of you who like to review lines of data you will see the average Total Born per Females Farrowed at 14.30 pigs with range by parity with P1 at 13.60, P4 at 14.80 and dropping to 14.23 pigs for P8+. When you look at gestation length the average is 14.30 total born with the few sows farrowing before day <=110 at 13.17 pigs, day 113 at 14.99 pigs with a drop to 11.06 pigs for the limited number of sows farrowing day 121 of gestation.

The second production number we looked at was Stillborns per Female Farrowed. We always wonder if stillborn pigs and pigs that are recorded as preweaning mortality are recorded correctly. We consider a stillborn pig as a pig that has not taken a breath after the birth process. If your farm is dealing with higher stillborn than you would expect it may be time to review what a true stillborn is for the crew doing the record keeping in farrowing. For a demonstration of a true stillborn all you have to do is open up a dead pig and cut off a small piece of lung tissue. When the lung tissue is placed in a cup of water it should sink to the bottom. If it floats the pigs has taken at least one breath to inflate the lungs. That is not a stillborn anymore.

In Chart 2, Stillborns/Females Farrowed, you see the effect of stillborns by parity and gestation length. Chart 2 is laid out with stillborns on Y-axis at 0 to 3.5 per litter and gestation length on X-axis from <=110 days up to >=122 days. The trend line by parity is higher for females with shorter gestation lengths and extremely long gestation days. The lowest number of stillborns is lower for sows with gestation of 113 to 117 days even though stillborns are higher for older parity females. As you see the data in Table 2 shows for the limited number of sows farrowing with gestation length at <=110 to 111 days with very high stillborns by parity with an average of 1.87 and 1.77 pigs. The range for females with a gestation length of <=110 days for P1 at 1.61 pigs to P8+ at 3.48 pigs. Table 2 shows lowest stillborns per litter by parity is for females with gestation length of 114 to 115 days which account for 39.4% of all the females farrowing. We figured that a lot of these sows farrowing early may have had some health issue causing them to farrowing early with an increased number of stillborns pigs or did they farrow in gestation and dead pigs were recorded as stillborns. Also if a sows farrows at <111 days is that information recorded at an abort?

Table 3 shows the percentage of the total stillborns for that gestation length and parity. Less than 2.0% of the stillborns happen on sows with <=112 gestation length. 38.7% of the stillborns for 113-115 gestation length, 56.3% of the stillborns for gestation length 116-118 and 3.3% of the stillborns for gestation length over day 118.

In summary as total born for the industry has improved the last few years and that average gestation length for some of the genetic companies has gone up with the total born being the higher for sows that gestate 112-114 days. If you are going to be doing any inducing of sows you need to know the range in gestation length as well as the average at your farm in order to know the best time to induce sows at your farm.

SMS Production Index

Table 4 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 articles about, please email or call us. We enjoy being a part of the National Hog Farmer Weekly Preview team.

Previous Production Preview columns can be found at

If you have questions or comments about these columns, or if you have a specific performance measurement that you would like us to write about, please contact: [email protected] or [email protected].

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