Managing sows during lactation is an ongoing challenge for pork producers. The objective of this research project was to determine the impact of deviations from predicted feed intake on sow performance.

Daily lactation feed intake (LFI) values were recorded on 10,716 litters farrowed by purebred Yorkshire and Landrace sows and Yorkshire x Landrace F1 sows. Average lactation length was 18.5 days. Daily LFI values were predicted for each litter based on the breed and parity of the sow, season the litter was farrowed, litter size after crossfostering and the day of lactation. A deviation from predicted daily LFI values was estimated as the difference of the observed daily LFI from the predicted daily LFI value.

Feed intake was considered inadequate when the daily LFI value was at least 4.2 lb. less than the predicted LFI value. Five percent of daily LFI records were inadequate and characterized as a negative deviation from the predicted LFI value. Sixty percent of sows had adequate feed intake and did not have a negative deviation from predicted daily LFI values. Thirty-four percent of negative deviations occurred during the summer months (June, July, August), which was more frequent than during the spring (26%), fall (23%) and winter (17%) months.

Total negative deviations from predicted LFI values ranged from zero occurrences up to 14 negative deviations. However, the occurrence of more than five deviations was rare and reproductive performance was not affected statistically by additional negative deviations. Reproductive performance and average daily LFI were reduced as the number of negative deviations increased (Table 1).

Litter weaning weight decreased with each negative deviation until at least four negative deviations occurred.

Wean-to-service interval remained constant when 0, 1 or 2 negative deviations occurred. But when the number of negative deviations during lactation reached at least three, wean-to-service interval began to increase.

During lactation, feed intake and body reserves are the only sources of nutrients available for body maintenance and milk production, with one directly affecting the other. Initially, the reduction in LFI resulted in lighter litters at weaning, though after several negative deviations occurred, it was likely that a sow’s body reserves were mobilized to compensate for the inadequate nutrients available from the sow’s diet for milk production and maintenance. As body reserves were mobilized, litter weaning weights remained constant while wean-to-service interval increased. When LFI was adequate, the sow could provide enough nutrients to her litter as well as maintain body reserves.

Limiting the number of negative deviations allows sows to maximize reproductive performance. It is highly likely that a sow that had a negative deviation of daily LFI would have another deviation the following day. Therefore, avoiding one negative deviation is important for future feed intake.

Purebred sows that had a negative deviation were 8.7 times more likely to have a negative deviation on the following day compared to sows that had adequate intake the previous day. In F1 sows, a negative deviation was 39.5 times more likely to occur in sows that had a negative deviation the previous day. As occurrences of negative deviations increased, performance decreased, and it was more likely that multiple negative deviations would occur during lactation.

Generally, it is ideal to maximize a sow’s feed intake during lactation. However, there are concerns that overeating may drastically reduce intake in subsequent days of lactation. In this study, observed LFI values that were at least 4.2 lb. higher than the predicted LFI values were considered positive deviations. The day following a positive deviation, purebred and F1 sows were 2.4 and 3.0 times less likely, respectively, to have a negative deviation from predicted LFI occur.

Daily feed intake greater than the predicted LFI the day after a positive deviation occurred was 4.4 times more likely in purebred sows and 9.2 times more likely in F1 sows. Sows with the capacity to eat significantly more than their predicted values did not have a drastic decrease in intake during subsequent days of lactation and were more likely to continue eating more than predicted.

Lactation feed intake plays a significant role in litter performance and the sow’s ability to remain in the breeding herd. Management of sows during lactation, especially feeding methods and feed intake, affect performance.  Managing sows during lactation continues to be an essential component of a sow’s success. Feeding sows with the intent of meeting predicted lactation feed intake levels should reduce the occurrence of negative deviations during lactation and, thus, maximize reproductive performance. 

Researchers: Chad Yoder and Tom Baas, Iowa State University. Contact Yoder by phone (515) 294-6728 or e-mail