The efficiency and accuracy of estrus detection using HeatWatch (DDx Inc., Denver, CO) or visual observation were compared in an autumn-calving Friesian herd (n = 48 per group) and a spring-calving Jersey herd (n = 50 per group) grazing on pasture. Cows in the group monitored by the HeatWatch system were fitted with a pressure-sensitive transmitter that signaled mounting activities associated with estrus. Visual observation was carried out for about 20 min before the morning and afternoon milkings and was aided by a strip of paint applied over the tailhead. Ovarian cyclicity was monitored with progesterone concentrations in milk samples collected twice a week. The efficiency and accuracy of estrus detection were, respectively, 98.4 and 97.6% for visual observation and 91.7 and 100% for HeatWatch detection. Autumn-calving herds differed from spring-calving herds in duration of estrus (9.7 vs. 7.3 h), number of mounts (13.6 vs. 8.5), total duration of mounts (36.8 vs. 19.9 s), and mean duration of a mount (2.6 vs. 2.3 s). There was no significant variation in the distribution of the time of onset of estrus or mounting activities at different hours of the day. Conception rate was similar for AI after estrus detection with HeatWatch (65.8%) or after visual observation (65.0%). The highest conception rate was obtained when AI was carried out between 12 and 18 h after the first mount. Both the HeatWatch system and visual observation plus tail painting can be used for estrus detection of dairy cows on pasture.
Sperm were incubated for up to 9 days in the presence or absence of exogenous
hydrogen peroxide, phenylalanine, catalase and aurintricarboxylic acid to
assess the influence of reactive oxygen species and inhibition of
deoxyribonucleases on sperm chromatin stability. The assessment of sperm DNA
susceptibility to in situ acid denaturation by the sperm
chromatin structure assay did not detect any difference in chromatin stability
between sperm incubated for 9 days under aerobic and anaerobic conditions in a
diluent called 14G. Exposure to exogenous hydrogen peroxide under both aerobic
and anaerobic conditions and to phenylalanine under aerobic conditions (which
produces hydrogen peroxide by a reaction catalysed by the aromatic amino acid
oxidase present in sperm) was detrimental to sperm chromatin stability,
increasing its DNA susceptibility to in situ acid
denaturation over the incubation time. This effect was eliminated if catalase
was present in the diluent. Inclusion of the general deoxyribonuclease
inhibitor aurintricarboxylic acid in the diluent severely decreased sperm
chromatin stability under both aerobic and anaerobic conditions.
Aurintricarboxylic acid was mildly cytotoxic, as revealed by viability
assessment, under aerobic, but not under anaerobic, incubation conditions.
Exogenous hydrogen peroxide, either directly added to the diluent or generated
through the enzymatic oxidation of phenylalanine, was detrimental to sperm
motility and the integrity of the plasma membrane.
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