Feeding During Gestation

Determining the proper feed allowance is crucial to the success of a gestational feeding program. The proper feed allowance will ensure large, healthy litters and allow adequate body tissue reserves.

To achieve this objective, gilts (Parity 0) should gain 80 to 100 lb. of weight during their first gestation. Parity 1-4 sows should gain 60-80 lb. Mature sows (Parity 5+) should gain about 55 lb. from conception to farrowing.

Target backfat thickness at the 10th rib should be 0.7-0.8 in. at farrowing. Some very lean genotypes will have difficulty achieving this level of backfat thickness.

Young sows (gilts through mating for the third litter) deserve special attention during gestation and lactation. These young sows are still growing and require different quantities of nutrients than older sows.

Generally speaking, if young sows remain in the herd through farrowing their third litter, there is a pretty good chance they'll be around for a fifth or sixth parity. Producers serious about meeting the needs of young sows will feed them at different levels than older sows, and they will install a second feed bin to allow feeding a diet tailored to the needs of the young, gestating sows in the herd.

There are several ways to monitor sow body condition and effectiveness of the gestational feeding program. Subjective condition scoring is often used, but is not considered very accurate because sows with the same condition score can have drastically different backfat levels. A direct measure of backfat thickness with an ultrasonic probe is more accurate than condition scoring, but does not account for changes in body weight.

Weighing Gestating Sows

Since sow body weight determines the majority of nutrient requirements of a gestating sow, it is very important to accurately determine body weight of sows. The best way to do this is to weigh sows with a livestock scale. The only true replacement for a livestock scale is another livestock scale! Visual assessments of body weight are not accurate.

On many farms, installing a scale in a common hallway between gestation and farrowing rooms allows workers to weigh sows as they enter the farrowing room and again when they leave at weaning. Weighing requires extra labor, but this information is extremely important for evaluating the gestation and lactation feeding programs, as well as an aid in fine-tuning sow feeding programs.

Every sow does not have to be weighed. Farms can select smaller groups of sows, maybe one week's production during each season of the year, to monitor weight changes. Weighing sows after a change in the feeding program will also help evaluate the effectiveness of the change.

In the absence of a livestock scale, producers can estimate sow weight with a flank-to-flank tape measurement. To record this measurement, a cloth tape measure is stretched from one rear flank over the sow's back to the opposite rear flank. This flank-to-flank measurement is used in the following equation, developed by workers at Kansas State University, to estimate sow weight:

Sow weight, lb. = 26.85 × (flank measurement, in.) — 628.

This approach properly assigned sows into 75-lb. body weight categories about 70% of the time. While not as accurate as a scale, it certainly is more accurate than “eyeballing” sow weight. Using this method can help producers determine sow weight and ultimately the proper feed allowance for sows.

The consequences of incorrect feed allocations and body condition can be significant. If sows receive too much feed and become overweight, they will have depressed feed intake during the subsequent lactation period (Figure 1), and may have reduced sow longevity. In addition, high feeding levels may cause sows to get too big to fit comfortably into individual gestation stalls and farrowing crates.

In contrast, underfed sows won't maintain adequate tissue reserves to support a normal lactation, especially if management or environmental factors limit voluntary feed intake. This will lead to an increased wean-to-estrus interval and reduced prolificacy.

Continue Reading on next page: Feeding During Lactation