Effects of the overshadow availability at pasture on the reproductive characteristics in Nelore Bulls / Efeitos da disponibilidade de sombra na pastagem sobre as características reprodutivas de touros da raça Nelore

AUTOR(ES)

Octavio Fabián Bao Tarragó

DATA DE PUBLICAÇÃO

2009

RESUMO

It is known that heat stress is the main cause that affects bulls reproductive performance, consequently leaded to testicular degeneration. This pathologic alteration can also occur in Bos Indicus cattle. The objective of this experiment was verify the shadow availability effect at pasture on reproductive characteristics in Nelore, a Bos Indicus bull. For this work, 10 bulls with ages of 20 ± 10 months were used. A month before the experiment started, semen samples were collected each 15 days for physical and morphological sperm evaluation. After this, animals were classified with a score according to the sperm characteristics values sum and then distributed in two groups: with Overshadow (CS) and without Overshadow (SS). In the group CS, 5 animals were kept in a picket (2 ha), with a 10 m2 shaded area per animal, consisted in a polyethylene filter with 90% solar light retention. In the group SS, the others 5 animals were placed in another picket (2 ha) with no access to shaded area. Semen collection, scrotal perimeter and testicular consistence measures ocurred every 15 days, for a 4 months period After collection, semen samples were submitted to following analysis: volume, sperm concentration, sperm motility by computer system (CASA - Computer Assisted Semen Analysis), morphological defects using differential interference contrast (DIC), plasmatic acrossomal membrane integrity and mitochondrial function by epifluorescence microscopy. Data obtained from experimental proceedings were analyzed by Statistical Analysis System program (SAS Institute Inc., 2004). It wasn´t find any statistical differences (P>0,05) in reproductive characteristics, when Nelore bulls were kept under envirormental conditions with or without overshadow.

ASSUNTO(S)

ambiência environment overshadow seminal quality sperm touros sombreado qualidade seminal bulls sêmen

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