Intracytoplasmic sperm injection improves in vitro embryo production from poor quality bovine oocytes

AbstractThe objective was to use subzonal sperm injection (SUZI) to understand sperm penetration patterns and to use intracytoplasmic sperm injection (ICSI) to improve production of bovine embryos using poor quality gametes. In experiment 1, poor versus good quality oocytes were fertilized with sperm from two bulls, A and B, with poor and good sperm vigor, respectively. The blastocyst rate was higher for good versus poor quality oocytes (23.3% vs. 11.1%, P < 0.05), regardless of the bull used. There was no significant difference in blastocyst rate for bull A (low vigor) regardless of oocyte quality, and for bull B (high vigor), blastocyst rate was better for good versus poor quality oocytes (25.7% vs. 9.2%, P < 0.05). In experiment 2, poor quality oocytes were subjected to SUZI. The oocyte penetration rate was lower for bull A than for bull B (29.6% vs. 53.8%, P < 0.05), when SUZI was performed within 1 hour after sperm processing. However, when SUZI was performed 2 to 3 hours after sperm processing, penetrating capacity was similar between bulls, but for bull B, penetrating capacity significantly decreased after 3 hours of sperm processing. In an attempt to overcome sperm penetrating disorders, poor and good quality oocytes were subjected to ICSI (experiment 3). Irrespective of the bull or of the oocyte quality grade, there were no differences in cleavage or blastocyst rates. Both bulls had distinct IVF embryo production rates, which we inferred were because of particular individual sperm characteristics. In conclusion, ICSI was an effective means to achieve in vitro production of bovine embryos with gametes of variable quality

Manejo do milheto em pastoreio rotativo para maximizar a taxa de ingestão por vacas leiteiras

Avaliaram-se os efeitos da estratégia de pastoreio rotacionado sobre a dinâmica do rebaixamento do milheto (Pennisetum glaucum (L.) R. Br.) pastejado por vacas leiteiras. Os tratamentos consistiram de um fatorial entre duas alturas pré-pastejo, 60 e 40cm, e duas pós-pastejo, 20 e 10cm, alocados em um delineamento em blocos ao acaso com quatro repetições. A estrutura do pasto foi avaliada durante o processo de pastejo a cada 10 minutos, por meio de medições de altura. A taxa de rebaixamento da altura do pasto no tratamento 40-20 apresentou-se relativamente constante ao longo de todo o rebaixamento. O tratamento 60-10 apresentou o maior declínio na taxa de rebaixamento. A taxa de rebaixamento no tratamento 40-10 diminuiu em ritmo mais lento em relação à dos tratamentos com 60cm de altura pré-pastejo. As maiores taxas de ingestão foram observadas nos tratamentos de altura pré-pastejo de 60cm, e considerou-se como a melhor estratégia de manejo a combinação 60-20cm de altura do pasto