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An application of the Ruminant Farm System Model (RuFaS): The use of a combination of sexed and beef semen on dairy herds.

M. Li




An application of the Ruminant Farm System Model (RuFaS): The use of a combination of sexed and beef semen on dairy herds.
M. Li*1, V. E. Cabrera1, K. F. Reed2. 1Department of Dairy Science, University of Wisconsin-Madison Madison, WI, 2Department of Animal Science, Cornell University Ithaca, NY.

A whole-farm integrated simulation model, the Ruminant Farm System model (RuFaS), is being collaboratively developed by multiple institutions to study dairy farm sustainability and profitability comprehensively. RuFaS is coded in Python and has a modularized framework of key farm components like animal, manure, soil and crop, and feed storage. In the animal module, a Monte Carlo stochastic model of the animal simulates individual animals and the overall herd. One application of the animal life cycle model was to evaluate the economic impact of a recent trend in reproductive management: breeding cows with a combination of sexed and beef semen. Our objective is to compare 2 reproductive management scenarios using the RuFaS animal life cycle model: (1) using conventional semen for all cows, (2) using 40%, and 15% sexed semen in the 1st and 2nd lactation cows, and beef semen in all other cows. A 1,000-cow herd following a Double-Ovsynch protocol was simulated, herd size was maintained with the heifers kept on-farm for both scenarios, and extra calves are sold as Holstein or beef calves. We set the conception rate (CR) for the first insemination of 1st lactation cows to 55% for beef and conventional semen. Then, we decreased the CR by 5% and 10% for 2nd and later lactations. Each additional insemination after the first had a 2.6% lower CR. We assigned sexed semen to be 80% CR of beef semen. Estimates of yearly net return (NR) included income from milk, sold calves value, slaughter value and costs from the feed, farm operations, and reproduction management, which included semen, AI, pregnancy checks. Results showed an NR of $2,237/cow per year for sexed and beef semen scenario, higher than the NR of $2,097/cow per year for conventional semen scenario. Once the animal life cycle model is fully connected to nutrition and farm management models in the animal and/or other modules, it will be able to provide complete farm profit analyses and multiple possibilities for scenario testing.

Keywords: whole-farm simulation, beef semen, RuFaS.