As the prices of feed grains creep upward pork producers are searching for ways to reduce feed costs. In the area of feeding gestating sows, managers and herds people must understand the principles of why sows are fed the way they are. In a paper given at Centralia in 2006, Dr. Mike Tokach discussed the management of feeding levels. There are three main goals in sow feeding:
- Prepare sows to be in proper body condition at farrowing.
- Maximize farrowing rate and litter size.
- Meet the daily nutrient requirements at the lowest cost possible.
A major challenge includes getting sows to the point of having a backfat level between 15 and 24 mm. at farrowing. The major point of discussion is the best way to set feeding levels to make sure this happens. One of the suggestions presented is to use the rough and dirty process of dividing the feed usage per day by the number of gestating sows in the barn. (Farrowing crates assuming all are full). It is hoped that this figure would be in the range of 2.1 to 2.5 kg per sow per day. This works out to the equivalent of 7.2 to 7.8 m.cal ME per sow per day.
In discussions on the weight of sows, it is not possible to weigh sows regularly. What has worked reasonably well is a technique of grouping sows into weight classes. A flank measurement is taken in front of the back legs, over the back of the sow to the same point on the flank on the other side of the sow. This measurement is fairly easy to obtain in farrowing crates. This measurement can be co-related to actual body weights (weigh the sow) and a weight to measurement pattern can be established. Backfat measurements are typically taken with whatever machine is available on the farm, and used by a trained experienced operator.
Setting Feeding Levels
Sows are scanned once a week for backfat and weight class. The backfat is written on the sow card and the feeding level is adjusted using a table customized for the barn, based on the energy density of the feed. If levels are off target feed intake is increased by .5kg/day. These levels are maintained until 100 days gestation. At day 100 the feeding level is increased by 1 kg/day for the last two weeks before farrowing. Critical issues are:
- A well trained person to scan and estimate weight.
- A known energy level of the gestation diet.
- The feed quantity (kg) being fed to each sow per day.
The science involved in this study is clear that overfeeding is most detrimental for gilts in the period from day of breeding, to day two past breeding. The safest recommendation at the present time is to limit feed intake from breeding until day 12 after breeding. The body condition of the sow influences the response to high levels of feed intake after mating. Embryo mortality is increased when high levels of feed are provided to sows in good body condition. Embryo mortality is decreased by providing extra feed for the first thirty days after breeding to sows in poor body condition due to low lactation feed intake. Therefore feeding according to body condition during the first 30 days of gestation is critical for minimizing embryo mortality.
The other important time to manage feed intake carefully is day 75 to 90 of gestation. This period is critical for mammary development. Excessive energy intake during this period increases fat deposits, and reduces the number of secretary cells DNA and RNA in the mammary gland. The result is lower milk production during lactation.
In summary, from a practical perspective, feeding pattern is less important than providing a total energy level over the entire gestation period that prevents excessive fat gain or inadequate body reserves at farrowing. Feeding sows on a backfat and weight category at breeding is a method that can help producers reach this goal.
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