- Title
- Seasonal variation in bull semen quality demonstrates there are heat-sensitive and heat-tolerant bulls
- Creator
- Netherton, Jacob K.; Robinson, Benjamin R.; Ogle, Rachel A.; Gunn, Allan; Villaverde, Ana Izabel S. Balbin; Colyvas, Kim; Wise, Ced; Russo, Tylah; Dowdell, Amiee; Baker, Mark A.
- Relation
- Scientific Reports Vol. 12, no. 15322
- Publisher Link
- http://dx.doi.org/10.1038/s41598-022-17708-9
- Publisher
- Nature Publishing Group
- Resource Type
- journal article
- Date
- 2022
- Description
- Using semen data from 1271 ejaculates (79 different bulls, 11 different breeds) we have investigated the variability of semen quality in cattle living in sub-tropical conditions. Modelling shows definitive evidence of seasonal variation. Semen quality from the same bulls had a 90% “pass rate” for cryopreservation purposes in winter, dropping to less than 50% in summer. Notably, individual bulls could be classified as either “heat-tolerant” (produce good quality spermatozoa all year regardless of temperature) or “heat-sensitive” (only produce good quality sperm in summer). Nominal logistic regression demonstrated when temperatures reach 30.5 °C, 40% of heat-sensitive bulls fail a semen analysis 17 days later. At 34 °C, the proportion of bulls failing reached 63%. Ratifying this, the purposeful heating of bulls to 40 °C for 12 h showed that individual animals had different degrees of heat-sensitivity. Using historical temperature data, we then modelled how many days/decade bulls would be subject to heat-events. Beginning from 1939 to 1949, on average, the area in which bulls were kept recorded 19, 7 and 1 day over 38 °C, 39 °C and 40 °C respectively. This number steadily increases and of last decade (2010–2010), the numbers of days per decade over 38 °C, 39 °C and 40 °C jumped to a staggering 75, 39 and 15 respectively. These data show the urgent need to identify heat-tolerant bulls as future sires. Such variation likely explains why the veterinary bull breeding test often fails to accurately predict bull breeding potential.
- Subject
- cattle; climate; hot temperature; seasons; semen; semen analysis
- Identifier
- http://hdl.handle.net/1959.13/1486900
- Identifier
- uon:51988
- Identifier
- ISSN:2045-2322
- Language
- eng
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