Effect of short-term high tryptophan diet fed to sows on their subsequent piglet behavior

Authors: Lay Jr, Donald; Enneking, Stacey; CHAPEL, NICHOLE - Purdue University; RICHERT, BRIAN - Purdue University; SAPKOTA, AVI - Purdue University

Submitted to: Translational Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/14/2021
Publication Date: 8/18/2021
Citation: Lay Jr, D.C., Enneking, S.A., Chapel, N.M., Richert, B.T., Sapkota, A. 2021. Effect of short-term high tryptophan diet fed to sows on their subsequent piglet behavior. Translational Animal Science. https://doi.org/10.1093/tas/txab127.
DOI: https://doi.org/10.1093/tas/txab127

Interpretive Summary: Housing sows in groups creates the challenge of decreasing fighting amongst sows. One proposed method is to feed a high tryptophan diet at the time of mixing of pregnant sows. However, the effect of high tryptophan on the developing fetus is unknown. To investigate this, 66 sows were fed 1 of 3 diets: Control (0.14% SID tryptophan), Medium (0.28% SID tryptophan), or High (0.42% SID tryptophan), from d 28 to 35 of gestation. Sows gestated in standard gestation stalls. Blood samples were taken prior to and after tryptophan supplementation. Day of birth was considered d 0. On d 1 and 2, 3 nursing bouts were observed to record disputes and displacements from teat competition. The piglets’ activity and fighting were recorded on d 3, 7, and 11 from 0700 h to 1700 h. On d 12, 4 piglets per litter were blood sampled. On d 14, 2 piglets per litter were subjected to a 10-min Isolation Test and 5-min Human Approach Test. On d 15, 2 piglets from different litters were subjected to a 10-min Social Challenge test and then immediately blood sampled. On d 18 ± 1.5 piglets were weaned. Data were analyzed using a mixed model analysis of variance. Sows had progressively greater tryptophan concentrations according to treatments (P < 0.0001). Sow serotonin concentrations did not differ among treatments (P > 0.10). Piglet cortisol and serotonin did not differ among treatments (P > 0.10). There were no differences (P > 0.10) for number born (12.7 ± 0.4), born alive (11.7 ± 0.4), or mortality (1.1 ± 0.2). Medium piglets tended to have fewer nursing disputes than the others (P < 0.8). Medium piglets had fewer nursing displacements than High piglets (P < 0.05). Nursing bout lengths were similar among treatments (198.8 ± 4.8 s, P > 0.10). No differences were detected for any of the variables for Isolation or the Human Approach Tests (P > 0.10). During the Social Challenge test, High piglets had more contacts approaching the head of the companion piglet than did either Medium or Control piglets (14.3 ± 1.1, 10.7 ± 1.1, and 9.69 ± 0.8 respectively, P < 0.007). Total number of aggressive interactions during the test tended to be greater for Medium piglets compared to High piglets (9.3 ± 1.5 vs 5.1 ± 0.9, P < 0.06). Time budget data of the litter indicate that piglets from all 3 treatments spent equal amounts of time active and inactive (P > 0.10). Aggression was low with .3 ± .04 % of the observation periods recording aggression. Feeding high concentrations of tryptophan for a short duration early in gestation does not have a negative impact on sows’ subsequent offspring.

Technical Abstract: Housing sows in groups creates the challenge of decreasing fighting amongst sows. One proposed method is to feed a high tryptophan diet at the time of mixing of pregnant sows. However, the effect of high tryptophan on the developing fetus is unknown. To investigate this, 66 sows were fed 1 of 3 diets: Control (0.14% SID tryptophan), Medium (0.28% SID tryptophan), or High (0.42% SID tryptophan), from d 28 to 35 of gestation. Sows gestated in standard gestation stalls. Blood samples were taken prior to and after tryptophan supplementation. Day of birth was considered d 0. On d 1 and 2, 3 nursing bouts were observed to record disputes and displacements from teat competition. The piglets’ activity and fighting were recorded on d 3, 7, and 11 from 0700 h to 1700 h. On d 12, 4 piglets per litter were blood sampled. On d 14, 2 piglets per litter were subjected to a 10-min Isolation Test and 5-min Human Approach Test. On d 15, 2 piglets from different litters were subjected to a 10-min Social Challenge Test and then immediately blood sampled. On d 18 ± 1.5 piglets were weaned. Data were analyzed using a mixed model analysis of variance. Sows had progressively greater tryptophan concentrations according to treatments (P < 0.0001). Sow serotonin concentrations did not differ among treatments (P > 0.10). Piglet cortisol and serotonin did not differ among treatments (P > 0.10). There were no differences (P > 0.10) for number born (12.7 ± 0.4), born alive (11.7 ± 0.4), or mortality (1.1 ± 0.2). Behavior during nursing bouts was similar, with no treatment differences in number of disputes or displacements and similar bout lengths among treatments (198.8 ± 4.8 s, P > 0.10). No differences were detected for any of the variables for Isolation or the Human Approach Tests (P > 0.10). During the Social Challenge Test, High piglets had more contacts approaching the head of the companion piglet than did either Medium or Control piglets (14.3 ± 1.1, 10.7 ± 1.1, and 9.69 ± 0.8 respectively, P < 0.02). Total number of aggressive interactions during the test tended to be greater for Medium piglets compared to High piglets (9.3 ± 1.5 vs 5.1 ± 0.9, P < 0.07). Time budget data of the litter indicate that piglets from all 3 treatments spent equal amounts of time active and inactive (P > 0.10). Aggression was low with .3 ± .04 % of piglets displaying aggressive behavior when observed. Feeding high concentrations of tryptophan for a short duration early in gestation does not have a negative impact on sows’ subsequent offspring.