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Seasonal Infertility Affects Total Born, Piglet Survival

In last week’s article (Weekly Preview, June, 3, 2011), we took a closer look at the effect of seasonal infertility on farrowing rate, repeat services, wean-to-first service interval and female death loss. We used the same data set – fall of 2009 to fall of 2010 – for this article. Again, only farms with a 12.5-total born/litter average or better for the past two years were used for this article.

Geographically, the 49 qualifying farms were located as follows: nine farms in southern states, 24 farms in northern states, and 16 farms in Canada. The division for north and south farms was determined by the Mason-Dixon Line.

Chart 1, Total Born/Female (by breeding data), shows adjusted data to reflect the total born/litter based on breeding date to see if there were any seasonal effects. For the 12 months in the dataset, the average of total pigs born/litter in Canadian herds was13.42 pigs, in northern states was 13.66 pigs, and in southern states was 12.59 pigs.

Focusing on Canada (blue line), you will see very little change in total born by month, especially in the summer months, starting in June with 13.28 pigs, July at 13.24 pigs, August at 13.59 pigs, September at 13.59, and October at 13.48 pigs/litter. Farrowing rate for sows bred in those months only dropped 2-3% during July, August and September breeding.

Looking at the data from farms in the north (red line), you will see total born/litter of sows bred in June at 13.75 pigs, dropping to 13.50 pigs in July, then 13.28 total born in August, then back up to 13.83 in September, and a nice jump to 14.0 pigs in October. That’s a difference of 0.75 pigs/litter, worst-to-best. In last week’s article, these same farms had the largest drop in farrowing rate from summer breedings.

The data for the farms in the southern states (green line) started off the lowest at 12.59 pigs/litter. In July, total born dropped to 12.01 pigs, August was 12.24 pigs, September at 12.90 pigs, and then back up to 13.14 pigs/litter in October. These farms showed the biggest improvement – over a pig/litter improvement during that stretch. The southern farms did not drop as much in farrowing rate as farms in the north, nor did the drop last as long.

As the data suggests, a drop in farrowing rate does affect total pigs born for the next litter. Therefore, not only do you have fewer litters, you also have fewer pigs to send to the finisher or to be sold as Isowean pigs.

Piglet survival (Chart 2) is a calculation where we subtract stillborn % and preweaning death loss % from 100% to provide a survival number. We are not concerned about which bucket the dead pigs are placed in. What is important is there is potential to save more pigs.

During the 12-month period, Canada (blue line) averaged 81.1% piglet survival rate, the north (red line) averaged 77.8%, and the south (green line) averaged 83.6%. Farms in the south did the best job of saving pigs, but there is also a lot of month-to-month variation in piglet survival, ranging from 78 to 87% over the last 12 months. There was a drop in late December, the second half of March and April, then in late July showed steady improvement.

Canadian farms showed less month-to-month variation, the best months being March through July. There was a small dip in early September when survival percent dropped to 78%.

For the northern farms, which had the lowest 12 months average at 77.8%, the line was very flat with the least amount of month-to-month variation, even though they had the highest total pigs born.

Looking at each region’s piglet survival performance separately, Chart 3 (Canada), Chart 4 (North) and Chart 5 (South), reinforce the large variation from farm-to-farm. There is probably some seasonal effect on piglet survival, but it is minimal as compared to the effects of people, sows, facilities, etc.

Next, we broke piglet survival into two components – Preweaning Death Loss (Chart 6) and Stillborns (Chart 7), which allowed us to see the trend lines by region.

For preweaning death loss, the 12-month average for Canada (blue line) was at 12.8%, for the north (red line) was 14.5%, and in the southern states (green line) averaged 11.1%. The farms for Canada and the northern states showed less month-to-month variation , while farms in the south had some spikes (sows farrowed in late December, late-March and April), and in the summer months, with a range of 8-12% in preweaning death loss.

Tracking stillborns, the 12-month average for Canada was 6.1%, in northern states was 7.7%, and in the south was 5.3%. All three regions showed some increase in stillborn pigs in early June and started declining in late August. The farms in the south had a big increase in stillborns in late-July, early-August, during the hottest weeks of the summer.

As you can see from the data, there is some effect on total born by the summer breeding season, with the most effect on farms in the south. As far as piglet survival, preweaning death loss, and stillborn pigs, we see a large variation from farm-to-farm, with some increase in stillborns during the summer months. However, there were other periods of the year, especially in the southern states, where preweaning death loss increased.

Here are a few suggestions to help improve the summer infertility period as it is related to farrowing and saving more pigs:

• Increase weekly breeding target by 5-10%, so more sows farrow and more pigs are born per group.

• Review semen management. Check temperature at delivery and monitor temperature in semen storage coolers. There should be no more than a 2-3° F. change during a 24-hour period.

• Provide supplemental cooling for all sows in gestation and lactation with cool cells, drippers, and/or fans.

• Sows in gestation will drink 2-4 gal./day and in lactation will drink 6-10 gal./day, which could increase 50% during extremely hot days. Make sure nipple waters in lactation flow at least 2 quarts/minute.

• Maximize feed intake in lactation by feeding sows several times per day. Have someone return to the farm in the evening to feed sows when it is cooler. Lactating sows should have ad-lib access to feed starting the day after farrowing. Make every effort to get younger females to eat as much as they can.

• Piglet survival can be improved by having someone attend more of the farrowings during the day and, if possible, into the evening. As the number of pigs born/litter increases, sows take longer to farrow and may need extra assistance, particularly in hot weather.

• If you can dry pigs at birth, fewer pigs will lie next to the sow in an attempt to keep warm, increasing their chances of getting laid on; you will also need fewer heat lamps.

• Start breeding sows earlier in the morning when they and the heat-check boars are less stressed. Use heat-check boars only 1-2 hours before rotating them to keep them fresh and aggressive. Make sure that you heat check into the flow of the cool cells to reduce sows getting early pheromone exposure and going into standing reflex before you are ready to breed them.

• Be sure to carry the semen in a cooler with cool packs to reduce the effect of heat on the semen before insemination.

The summer heat does appear to affect total pigs born for the next litter with less affect on stillborns and preweaning death loss. Again, as with most data, there is a lot of variation from farm-to-farm and region-to-region. With advanced planning and improved management techniques, a farm can overcome some of the effects of seasonal infertility and their impact on pig survival.

Key Performance Indicators
Tables 1 and 2 (below) provide 52-week and 13-week rolling averages for key performance indicators (KPI) of breeding herd performance. These tables reflect the most current quarterly data available and are presented with each column. The KPI’s can be used as general guidelines to measure the productivity of your herd compared to the top 10% and top 25% of farms, the average performance for all farms, and the bottom 25% of farms in the SMS database.

If you have questions or comments about these columns, or if you have a specific performance measurement that you would like to see benchmarked in our database, please address them to: or

Click to view graphs.

Mark Rix and Ron Ketchem
Swine Management Services LLC