In vitro performance and in vivo fertility of antibiotic-free preserved boar semen stored at 5 °C

Abstract

Background Hypothermic preservation of boar semen is considered a potential method for omitting antibiotics from insemination doses, thereby contributing to the global antibiotic resistance defence strategy. The main challenges are chilling injury to spermatozoa and bacterial growth during semen storage leading to reduced fertility. Objectives To examine chilling injury and the number and type of bacteria in boar semen stored at 5 °C in the absence of antibiotics, and to assess the applicability of hypothermic semen storage under field conditions. Material and methods Boar ejaculates were extended with AndroStar® Premium, stored at 17 °C with and at 5 °C without antibiotics and tested for functional sperm parameters by flow cytometry. Raw semen and extended samples were investigated bacteriologically. Fertility was evaluated after once-daily inseminations of 194 sows in a field study. Results Lethal sperm damage assessed by motility and membrane integrity was low throughout storage in both experimental groups. Sublethal chilling effects based on the decrease of viable spermatozoa with low membrane fluidity were higher (P < 0.05) up until 72 h in sperm stored at 5 °C compared to 17 °C but did not differ after 144 h. After 72 h, incubation in capacitating medium for 60 min induced a similar decrease in viable sperm with high mitochondria membrane potential and low cytosolic calcium in both groups. In semen stored at 5 °C, bacteria counts were below 103 CFU/mL and the bacteria spectrum was similar to that of raw semen. In 88% of 34 boars, cooled semen fulfilled the requirements for insemination. Fertility was high and did not differ (P > 0.05) between sow groups inseminated with semen stored antibiotic-free at 5 °C and semen stored at 17 °C with antibiotics. Conclusion Despite subtle chilling effects and low bacterial numbers, antibiotic-free hypothermic storage of boar semen offers the possibility to reduce the use of antibiotics in pig insemination. However, strict sanitary guidelines must be maintained and further evidence of efficiency under field conditions is considered desirable.

Antimicrobially Active Semen Extenders Allow the Reduction of Antibiotic Use in Pig Insemination

“…One could suggest that so-called long-term extenders designed to maintain sperm longevity for up to seven days would not only better preserve sperm viability but also favour bacterial survival and growth. Interestingly, we observed just the opposite: the Androstar Premium extender, providing long-term preservability and cold shock protection for sperm [ 16 , 17 ], displayed a higher antimicrobial capacity compared to the BTS semen extender in the absence of antibiotics. This was visualised by a 2 to 3.5 log level lower presence of the four bacterial test strains after 144 h in semen-free Androstar Premium samples, three of them ( E. coli , Ps.…”

“…However, until now, none of the concepts have been feasible for AI practice because they lack antimicrobial efficiency, are sperm-damaging or impracticable and costly. The recently proposed antibiotic-free semen storage at 5 °C to achieve bacteriostasis was successfully tested in field insemination trials [ 16 , 17 ] but awaits further proof of concept in AI practice. Therefore, fast realisable alternatives which at least reduce the use of antibiotics would mitigate the current situation until other options become available.…”

The Efficiency of Selected Extenders against Bacterial Contamination of Boar Semen in a Swine Breeding Facility in Western Slovakia

“…The evolution of contemporary swine industry is closely associated with the implementation of modern reproductive technologies which have significantly contributed to a remarkable rise in the production of high-quality protein foodstuffs [ 1 ]. In particular, artificial insemination (AI) has become a popular choice for an intensive pig production, since approximately 90% of sows are being fertilized artificially in the leading pork producing countries [ 1 , 2 ]. In comparison to natural mating, AI is a more effective tool to accelerate the genetic progress of breeding, while minimizing the risks of horizontal or vertical transmission of venereal diseases [ 1 , 3 ].…”

“…Amongst numerous endogenous and exogenous factors that may contribute to a decreased fertility in animal breeding, bacterial contamination of semen may be also responsible for a reduced shelf life of extended semen, conception rates and litter size [ 2 , 4 , 5 , 6 ]. Bacteriospermia in boars may originate from the urogenital system or preputial fluids as well as hair, skin, respiratory secretions, or feces.…”

Hydroxytyrosol effectively improves the quality of pig sperm at 17 °C

“…Pig sperm is extremely sensitive to temperature changes especially low temperature [15,32]. The cold shock caused by low temperature has a serious impact on sperm quality and the fertilization potential of sperm [13,25,31]. Besides, high level of technology and equipment are required for cryopreservation of pig sperm.…”