No abstract

No abstract

This study aimed to assess the degree of contamination of bulk tank milk (BTM) by Staphylococcus spp. and coliform bacteria and to identify major milking practices that help perpetuate them in dairy cattle herds in São Miguel Island. In July 2014, BTM was sampled and a survey concerning local milking practices was conducted on 100 herds. Semi quantitative multiplex polymerase chain reaction detected coagulase-negative staphylococci, Escherichia coli, Staphylococcus aureus, and other coliform bacteria (Klebsiella oxytoca, Klebsiella pneumoniae, and Serratia marcescens) in 100, 75, 59, and 35 % of BTM, respectively. According to multivariable univariate models, on herds not using hot water for cleaning the milking machine and teat liners, there was at least 3.4 more odds (P < 0.01) to have S. aureus or coliform bacteria contamination in BTM. The likelihood of finding S. aureus in BTM was higher (P < 0.001) on herds without high hygiene during milking, when milking mastitic cows at the end, on abrupt cessation of milking at dry-off, and official milk control implementation. The glove use also favored (odds ratio (OR) 5.8; P < 0.01) the detection of coliform bacteria in BTM. Poor milking practices identified in this study should be avoided in order to decrease S. aureus and coliform bacteria contamination of BTM. Other factors associated with milk quality in São Miguel Island also should be further investigated.

No abstract

a b s t r a c tSuccessful production of high quality blastocysts depends on the use of a culture system that ensures the acquisition of developmental competence by the maturing oocyte followed by an efficient in vitro fertilization. In the present work the effect of FSH and pyruvate in an EGF containing medium for ovine oocyte maturation prior to insemination with fresh (F) or frozen-thawed (FT) semen on embryo developmental competence and cryosurvival was determined. Sheep oocytes were matured in two culture media (M1 and M2, respectively; M1 = CM + EGF, n = 836 and M2 = CM + EGF + pyruvate + FSH, n = 850) for 22 h and then fertilized using FT or F spermatozoa (M1 × FT = 371, M2 × FT = 359, M1 × F = 353 and M2 × F = 372, 9 replicates) from Merino rams (n = 3). After embryo culture and evaluation, good quality blastocysts (grade 1) were vitrified in OPS. Post-thawed embryo integrity, re-expansion and number of total and viable cells were assessed. Oocyte maturation rates presented no differences (P > 0.05) between treatments (M1 = 87.0 ± 4.1 and M2 = 86.7 ± 3.9%) as well as embryo developmental rates either for maturation media or semen status. However, fresh semen improved blastocyst quality (grade 1 embryos F = 52.5 ± 4.8% and FT = 39.0 ± 4.4%, P = 0.01). Grade 1 blastocysts presented similar post-thawed integrity and re-expansion rates. After 3 h of culture, expansion rates were higher (P = 0.05) for M2 × F warmed embryos (80.0 ± 8.3%) than for M1 × F (54.3 ± 10.4%). Results seem to confirm the existence of a synergistic effect between FSH, EGF and pyruvate upon cytoplasmic maturation of ovine oocytes. Moreover, in vitro fertilization by fresh semen clearly improves ovine embryo developmental competence by enhancing morphological blastocyst quality. The beneficial effect of M2 on cryosurvival was only observed in embryos derived from fresh semen. Therefore these combined strategies enhance embryo cryosurvival.

The lower results in cryopreservation of in vitro-produced (IVP) sheep embryos, when compared to the in vivo derived, limits its use. Four groups of blastocyst (BL) were evaluated: fresh IVP (n = 3), fresh in vivo derived (n = 3), warmed IVP cryopreserved in open pulled straws (OPS, n = 3) and warmed in vivo derived cryopreserved in OPS (n = 3). Ultrastructural observation of processed fresh embryos showed a reduced number of microvilli and mitochondria in the IVP ones, as well as a lower number of mature mitochondria, that can be associated with deficient metabolism in IVP embryos, possibly involved in the lower resistance to cryopreservation. Both in vivo-derived and IVP embryos had a large number of vesicles, with light and dense content. In embryos vitrified by OPS, major changes were observed mainly in IVP embryos with small changes in grade 2 (fair) and high changes in grade 3 (bad) semithin scoring. The main changes associated with cryopreservation included disruption of cellular membranes and poor intracellular preservation, with loss of microvilli and the presence of cellular debris. In conclusion, ultrastructural evaluation of IVP blastocysts cryopreserved in OPS was herein described for the first time, reporting more severe cellular damage in these embryos when compared to those produced in vivo. This is probably associated with a lower cryotolerance that can be related to their lipid content and metabolism.

No abstract

Global warming has negatively influenced animal production performance, in addition to animal well-being and welfare, consequently impairing the economic sustainability of the livestock industry. Heat stress impact on male fertility is complex and multifactorial, with the fertilizing ability of spermatozoa affected by several pathways. Among the most significative changes are the increase in and accumulation of reactive oxygen species (ROS) causing lipid peroxidation and motility impairment. The exposure of DNA during the cell division of spermatogenesis makes it vulnerable to both ROS and apoptotic enzymes, while the subsequent post-meiotic DNA condensation makes restoration impossible, harming later embryonic development. Mitochondria are also susceptible to the loss of membrane potential and electron leakage during oxidative phosphorylation, lowering their energy production capacity under heat stress. Although cells are equipped with defense mechanisms against heat stress, heat insults that are too intense lead to cell death. Heat shock proteins (HSP) belong to a thermostable and stress-induced protein family, which eliminate protein clusters and are essential to proteostasis under heat stress. This review focuses on effects of heat stress on sperm quality and on the mechanisms leading to defective sperm under heat stress.