High or low feed intake at key points during gestation can cause negative effects or lead to specific advantages. How sows are fed may be just as important as what they are fed.
Figure 1 is a feeding pattern I recommend for each gestation stage.
Day 0 to 30 Researchers report high intake before day 30 of gestation decreases embryo survival.
Further research indicates the first 48 to 72 hours after mating may be a critical window to prevent embryo mortality. The safest recommendation is to limit feed intake to around 4-5 lb./day (to both sows with good and poor body condition) from breeding until 72 hours after breeding. Then start giving thin sows the extra feed to get them back into condition.
More embryos are lost when sows in good body condition are fed too much. But, when sows were in poor body condition (due to low feed intake during the previous lactation) embryo survival improved by providing extra feed for days 2-30 after breeding. Therefore, feeding according to body condition during days 2-30 of gestation is critical for minimizing embryo mortality.
Recent unpublished data from Australia also credits high feeding during early gestation with increasing farrowing rate during the summer months when seasonal infertility is a problem.
Feeding level from day 2 to 30 is shown as a shaded area in Figure 1. Shading indicates feeding level should match sow body condition. Try to have the sow at the body condition desired for farrowing by day 30 of gestation.
In order to reduce the possibility that the higher feed intake will increase embryo mortality, feeding level from day 0 to 2 of gestation is shown at the baseline value (approximately 4 lb. of a diet containing 3.2 Mcal metabolizeable energy (ME)).
Day 30 to 75 Current understanding of this period during gestation is poor. As shown in the figure, we generally recommend feeding a constant level sufficient to meet the sow's energy requirements and maintain body condition. However, recent research indicates this is a critical period for muscle differentiation i n developing fetuses.
Recent research from the United Kingdom shows doubling feed intake (5.5 vs. 11 lb./day) from day 25 to 80 of gestation increased secondary muscle fibers and improved growth rate and feed efficiency of the offspring during their growing period (day 7 to 130 of age).
A recent Kansas State University pilot study evaluated fetal development when feeding gestating sows either 4 lb./day or 12 lb./day from gestation day 29 to 45.
Preliminary results suggest a negative correlation between number of fetuses and fetal weight in sows fed 4 lb./day. As potential litter size increased, the weight of the fetuses on day 50 of gestation decreased. This is similar to the trend when the number of pigs born increases, average pig birth weight decreases.
However, there was no correlation between number and weight of fetuses in sows fed 12 lb. during this period. We speculate the extra feed removed the maternal limit of fetal growth. Current research is ongoing to see if pig birth weight reflects this response, and if it will influence growth rate or carcass characteristics.
It is important to emphasize these are preliminary results that need further verification. However, as future research identifies the specific nutrient(s) and time period needed for optimal response, gestation stage feeding for fetal muscle development may be possible.
Day 75 to 100 This period is critical for mammary development. Excessive energy intake here increases mammary gland fat deposits. The fat deposits replace secretory cells. Lower milk production results. Excess feed intake should be avoided during this time.
Day 100 to 112 Increase feed intake by 2 to 4 lb. from day 100 to 112 of gestation to prevent sows from losing weight and backfat during this period of rapid fetal growth.
Failure to increase feed intake during this period results in sows being deficient in energy. The sow begins breaking down her own body fat stores when her energy needs aren't met. She tries to replenish the lost energy quickly after farrowing. This often leads to gorging, and "going off feed" during lactation.
Day 112 to 114 Feeding pattern during the last few days of gestation is controversial. We prefer to feed 4 lb. or more from day 112 to 114.
Field experience indicates extremely low intake of 2 lb. or less during this period limits the producer's ability to rapidly increase lactation feed intake. Extended low intake around farrowing may cause ulcers in extreme cases.
Sows often overeat if provided free access to feed after the long period without feed. The sows will go off feed or have a noticeable dip in feed intake.
Many people prescribe limit feeding as a cure for sows going off feed, instead of correcting the cause of the problem, which is little or no feed intake prior to and immediately after farrowing.