What question did this study set out to answer?

The research aims to investigate the effects of tryptophan supplementation during late gestation on aggressive behavior and growth performance in group-housed sows.

May 9, 2026

Supplementing Tryptophan in Late Gestation Diets to Group-housed Sows Under Commercial Conditions: Effects on Aggressive Interactions and Sow and Litter Performance

Key Points

The research aims to investigate the effects of tryptophan supplementation during late gestation on aggressive behavior and growth performance in group-housed sows.
948 sows were randomly assigned to a control or tryptophan-supplemented diet.
Sows were observed for aggressive interactions and key performance metrics were measured pre- and post-treatment.
Data on litter characteristics and return to estrus interval were also collected.
No differences were found in aggressive interactions with an average of 22.6 interactions/h across treatments (P > 0.10).
Litter performance metrics such as total born, live born, and weaning weights were also similar between groups (P > 0.10).
Aggressive interactions were greater on day 3 compared to day 5 post-treatment (25.1 vs 20.2 interactions/h, P < 0.01).

Abstract

Abstract Group-housing sows during gestation has become more prevalent in the swine industry. However, this housing strategy has the potential to result in increased aggressive interactions between sows, greater risk of injury, and poorer farrowing performance. Therefore, the study’s objective was to determine the effects of tryptophan supplementation (0.24% increase in SID Trp) during late gestation d 103.1 ± 1.7 to d 111.4 ± 1.1 on aggressive interactions, sow and litter growth performance, litter characteristics, and the return to estrus interval in group housed sows under commercial production conditions. We hypothesized that supplemental Trp would reduce aggressive interactions, improve growth performance, and result in more viable litters. In total, 948 gestating nulliparous and multiparous sows (parity = 2.7 ± 1.2) were randomly assigned based upon parity and breed date to either a control corn-soybean meal-DDGS-based diet containing 0.11% SID Trp (n = 9 pens/treatment with 52.3 ± 1.6 sows/pen) or the control diet supplemented with an additional 0.24% SID Trp (n = 9 pens/treatment with 53.6 ± 1.5 sows/pen). Body weights were collected 1 d prior to treatment administration and on the day, sows moved into farrowing. Sow feed intake was assessed daily. Sow mortality during late gestation and removals during lactation were assessed continuously throughout the trial. All sows were video recorded for a total of 12 h (0100 to 0300 h, 0500 to 0700 h, 0900 to 1100 h, 1300 to 1500 h, 1700 to 1900 h, 2100 to 2300 h) on d 3 and 5 post-treatment administration, respectively, to assess aggressive interaction counts per h within each pen. Litter characteristics including total born, live born, mummies, stillborn, number weaned, and weaning weights were recorded for all litters. The return to estrus interval was assessed for each sow. Pen was considered the experimental unit for all measures. No treatment differences (P 0.10) in sow body weight (254.6 ± 5.6 kg), sow mortality in gestation (0.5± 0.3%), lactation removals (3.6 ± 1.0%), sow feed intake (2.4 ± 0.1 kg), aggressive interactions (22.6 ± 1.4 interactions/h), total born (17.2 ± 0.2 piglets), live born (15.3 ± 0.2 piglets), stillborn (1.5 ± 0.1 piglets), mummies (0.5 ± 0.1 piglets), number weaned (13.1 ± 0.2 piglets), or litter weaning weight (5.6 ± 0.5 kg/piglet) were observed. Aggressive interactions were greater overall (P 0.01) on d 3 (25.1 ± 1.2 aggressive interactions/h) versus d 5 (20.2 ± 1.2 aggressive interactions/h), regardless of treatment. Taken together, a 0.24% increase in SID Trp in late gestation diets did not appear to reduce aggressive interactions or improve measures of sow and litter performance under commercial production conditions.

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