Factors affecting fertility
From the February 2009 edition of Agriculture Today.
A recent analysis of historical data collected from beef cattle research herds over several decades has confirmed the importance of cow liveweight and body condition at mating on overall herd reproductive performance.
The project, co-funded by Meat and Livestock Australia, included the compilation of all historical performance data collected from NSW Department of Primary Industries (DPI) research herds at Trangie, Grafton, Glen Innes, Camden and Wagga Wagga since the early 1970s.
NSW DPI research leader, Dr Peter Parnell, said the resultant database of more than 50,000 animals was among the largest research databases in the world.
"Now that we have this information in an easily assessable database, we have the potential to explore the many factors affecting herd profitability over time," Dr Parnell said.
Wagga Wagga-based DPI beef scientist, Dr John Wilkins, oversaw the compilation of the database and was responsible for the latest analysis of factors affecting reproductive performance in these herds.
According to Dr Wilkins, the analyses so far have only just begun to mine the data, but provide the background for new studies into the factors affecting cattle reproductive performance.
For example, the data confirmed earlier reports that there was no detriment to reproductive performance as a result of selection for improved growth rate or muscularity in cattle.
The data also confirmed the presence of strong and consistent associations of fertility with liveweight and body condition at mating.
The findings reinforce the importance of nutritional management of the cow herd to ensure cows have adequate body status to ensure the success of mating.
Dr Wilkins said it had long being recognised that the status at calving would have a major affect on body status at the next mating, since the cow must cope with the high metabolic demands of lactation which impacts on her body stores and ability to resume ovarian activity before next mating.
"The overall energy balance from calving through lactation and leading up to the next mating determines her body status and consequent chance of successful mating," Dr Wilkins said.
The latest analysis conducted by Dr Wilkins also confirmed the importance of early conception during the breeding season.
The proportion of cows pregnant in the first weeks of joining was an important determinant of the spread of alving for the current season.
This not only affects the numbers and evenness of the weaner crop, but also the rate and pattern of pregnancy in the following year.
Contact Dr John Wilkins, Wagga Wagga, (02) 6938 1837, john.wilkins@dpi.nsw.gov.au
