title: Bull Fertility and Its Relation with Density Gradient Selected Sperm.
abstract: BACKGROUND
  Sperm selection method is usually used to collect these cells forin vitro-assisted reproduction. Few studies reported the relationship ofin vivofertility and semen parameters after sperm selection; hence, the present study attempted to assess different semen parameters after post-thaw or sperm selection, using density gradient separation BoviPure®, to predictin vivofertility.
  
  
  METHODS
  In this experimental study, frozen semen quality of four Montbeliarde bulls were assessed after post-thaw (PT) or after sperm selection (SSp), using density gradient separation BoviPure®, to predict the fertility rate in vivo. In addition to PT or SSp, semen was examined for concentration, motility, morphology abnormalities, viability, acrosome and plasma membrane integrities. Fertility was measured as non-return rates within 56 days after the first insemination (NRR) or as corrected NRR, expressed as CNRR, to the factors influencing fertility using linear mixed model. Non-parametric Kruskal-Wallis test was performed to compare semen parameter variables. Fertility rates were compared using Chi-square test. Pearson correlation analysis was used to test the relationship between CNRR and semen parameters. Data was analysed using SPSS package program, version 21.0.
  
  
  RESULTS
  Most of the examined bulls exhibited a high fertility rate (3/4 bulls, 62.1- 81.8% for NRR or 67.2-98.5% for CNRR). Fertility rate, expressed as CNRR, was significantly related to semen parameters after SSp, but not after PT. Thus, CNRR was increased with decrease of total motility, progressive spermatozoa and abaxial implantation frequencies after SSp (r=-0.999, P=0.001; r=-0.990, P=0.010; r=-0.988, P= 0.012, respectively); while, CNRR was decreased with decrease of SSp immotile spermatozoa (r=+0.995, P=0.005), underlying that maximal limit of determined immotile spermatozoa is 47%.
  
  
  CONCLUSIONS
  High frequencies of total and progressive motility spermatozoa, and abaxial implantation in gradient selected sperm appear to be not favorable for fertilityin vivo.
authors.affiliation: Department of Biology and Animal Physiology, Faculty of Nature and Life Sciences, Ferhat Abbas Setif 1 University, Setif, Algeria.
authors.forename: Lynda
authors.initials: L
authors.lastname: Allouche
authors.affiliation: Department of Agronomy, Faculty of Nature and Life Sciences, Ferhat Abbas Setif 1 University, Setif, Algeria.
authors.forename: Toufik
authors.initials: T
authors.lastname: Madani
authors.affiliation: National Center for Artificial Insemination and Genetic Improvement, Algiers, Algeria.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Mechmeche
authors.affiliation: National Laboratory for Health Control in Breeding stock (LNCR), Allice, Maison Alfort, France.
authors.forename: Laetitia
authors.initials: L
authors.lastname: Clement
authors.affiliation: National Center for Artificial Insemination and Genetic Improvement, Algiers, Algeria.
authors.forename: Allaoua
authors.initials: A
authors.lastname: Bouchemal
keywords: Bull; Fertility; Frozen Semen