The cost-benefit of genomic testing of heifers and using sexed semen in pasture-based dairy herds

Abstract

Recent improvements in dairy cow fertility and female reproductive technologies offer an opportunity to apply greater selection pressure to females. This means there may be greater incentive to obtain genomic breeding values for females. We modeled the impact of changes to key parameters on the net benefit from genomic testing of heifer calves with and without usage of sexed semen. This paper builds on earlier cost-benefit studies but uses parameters relevant to pasture-based systems. A deterministic model was used to evaluate the effect on net benefit due to changes in (1) reproduction rate, (2) genomic test costs, (3) availability of parent-derived breeding values (EBV), and (4) replacement rate. When the use of sexed semen was included, we also considered (1) the proportion of heifers and cows mated to sexed semen, (2) decreases in conception rate in inseminations with sexed semen, and (3) the marginal return for surplus heifers. Scenarios with lower replacement rates and no availability of EBV had the largest net benefits. Under current Australian parameters, the net benefit of genomic testing realized over the lifetime of genotyped heifers is expected to range from A$204 to A$1,124 per 100 cows for a herd with median reproductive performance. The cost of a genomic test, a perceived barrier to many farmers, had only a small effect on net benefit. Genomic testing alone was always more profitable than using sexed semen and genomic testing together if the only benefit considered was increased genetic gain in heifer replacements. When other benefits (i.e., the higher sale price of a surplus heifer compared with a male calf) were considered, there were combinations of parameters where net benefit from using sexed semen and genomic testing was higher than the equivalent scenario with genomic testing only. Using sexed semen alongside genomic testing is most likely to be profitable when (1) used in heifers, (2) the marginal return for selling surplus heifers (sale price minus rearing costs) is greater than A$400, and (3) conception rates of no more than 10 percentage points lower than those achieved using conventional semen can be realized. Net benefit was highly dependent on the marginal return. Demonstrating that the initial investment in genomic testing can be recouped within the lifetime of the heifers tested may assist in the development of extension messages to explain the value of genomic testing females at the herd level.

Demonstrating the value of herd improvement in the Australian dairy industry

“…Although still measured in years, a much shorter timeframe can be considered. Adopting similar reasoning to Calus et al (2015) but modelling Australian dairy farms, Newton et al (2018) showed that the net benefit of genotyping to guide heifer-replacement decisions on an 'average' farm with surplus heifer-replacement candidates is likely to be positive. They found that when the selection decisions were based on parent average-derived EBVs, the net benefit of genotyping was AU$204 in a 100-cow herd in a scenario where all female progeny are tested.…”

“…Ultimately, the financial returns from genotyping to support replacement decisions are greatly influenced by individual farm parameters such as replacement rate, reproductive performance and current selection practices. However, being able to show that investments in herd improvement tools can be recouped within a short timeframe may support uptake of commercial genomic testing of heifers (Newton et al 2018).…”

“…However, selection of herd replacements has been the most frequently modelled because of its ease of measurement. In practice, the availability of EBVg is likely to result in other changes on farm such as usage of sexed dairy semen, or beef semen or both sexed dairy semen and beef semen as modelled by McCullock et al (2013), Newton et al (2018) and Bérodier et al (2019). The availability of accurate EBVs on young animals also presents opportunities on farm, including changes to calf rearing strategies, changes to cow culling strategies, new markets due to validated pedigrees or EBVg or both, optimised mating programs or managing inbreeding.…”

Genome to Phenome: Improving Animal Health, Production, and Well-Being – A New USDA Blueprint for Animal Genome Research 2018–2027

“…This is similar in concept to precision therapeutic treatments in humans, which is beginning to be used in the treatment of certain cancers by genotyping the cancer cells and adjusting the treatments accordingly (Leão and Ahmed, 2019). An example of this approach in livestock has already been implemented in dairy cattle, where separate genetic merits for cheese making (Francesco Tiezzi, 2018) and pasture-managed dairy cattle (Newton and Hayes, 2018) have been developed. Aside from this example, precision management based on genotype is still in its infancy.…”

Transfer of a single embryo versus drainage of subordinate follicles to prevent twin pregnancies in dairy cows. Why not both?

“…The use of sexed semen has been traditionally recommended only for heifers [18,19], as pregnancy rates are reduced in cows [20,21]. Although its usage is low (< 5%) within the AI market [22], it generates herd replacements and additional heifers [23].…”