Sow reproductive performance following artificial insemination with semen doses processed using Single Layer Centrifugation without antibiotics in the tropics

Single Layer Centrifugation (SLC) through a low density colloid offers an alternative solution to antibiotic use in boar semen extenders, with lower costs compared to high density colloids. The aim of this study was to explore the reproductive performance of sows when using SLC-prepared semen doses without antibiotics, employing low density Porcicoll to prepare semen doses for artificial insemination in a commercial swine herd in Thailand. Ejaculates were divided into two equal parts to create insemination doses, with each dose containing 3000 x 10 6 sperm/80 ml for intra-uterine insemination in individual sows. The sows were inseminated twice, with the interval between the two inseminations ranging from 8 to 16 h. The CONTROL group consisted of 206 semen doses treated with antibiotics, prepared for insemination in 103 sows, while the SLC group comprised 194 SLCprepared semen doses without antibiotics for inseminating 97 sows. Fertility and fecundity traits, including non -return rate, conception rate, farrowing rate, and litter traits (i.e., the total number of piglets born per litter, number of piglets born alive per litter, number of stillborn piglets, and number of mummified fetuses), were compared between groups. Furthermore, data on piglet characteristics, including live-born and stillborn piglets (i.e., the prevalence of stillbirth (yes, no), birth weight, crown-rump length, body mass index (BMI), and ponderal index (PI)), were determined. No significant differences in non -return rate (75.7 % vs. 77.3 %), conception rate (73.8 % vs. 73.2 %), and farrowing rate (71.8 % vs. 73.2 %) were observed between the CONTROL and SLC groups, respectively ( P > 0.05). Nevertheless, the total number of piglets born per litter in the SLC group was higher than in the CONTROL group (14.6 +/- 0.9 vs. 12.3 +/- 0.6, respectively, P = 0.049). Interestingly, the prevalence of stillbirth in the SLC group was lower than in the CONTROL group (6.2 % vs. 11.6 %, respectively, P < 0.001). Moreover, the newborn piglets in the SLC group exhibited higher birth weight and BMI compared to those in the CONTROL group (1.36 +/- 0.03 vs. 1.26 +/- 0.02 kg, P = 0.005, and 18.3 +/- 0.3 vs. 17.3 +/- 0.2 kg/m( 2) , P = 0.003). In conclusion, employing sperm doses after SLC through a low density colloid in artificial insemination within a commercial breeding operation did not have a detrimental impact on either fertility or fecundity traits but showed potential benefits in increasing the total number of piglets born per litter. Moreover, improvements were observed in the birth weight and body indexes of piglets, and the percentage of stillbirths was reduced. Our findings introduce new possibilities for antibiotic alternatives in semen extenders to reduce the risk of antimicrobial resistance in the swine industry. Additionally, they provide compelling reproductive outcomes supporting the integration of SLC-prepared semen doses into artificial insemination practices.