DONOR OUTPUT INDEX:
STgenetics® Index to improve donor performance
The expansive use of reproductive biotechnologies such as in-vitro fertilization (IVF) and Multiple Ovulation Embryo Transfer (MOET) is of growing importance in the dairy industry. The adoption of these technologies by dairy producers can accelerate genetic gain by reducing generation interval, increasing the intensity of selection, and rapidly propagating the genetics of elite females. Selecting ideal donor females that have both superior genetics for performance traits and the capability to produce a significant number of offspring will optimize the advantages of reproductive biotechnologies like IVF.
WHY IS IT IMPORTANT TO SELECT DONOR FEMALES IN AN IVF PROGRAM WITH SUPERIOR REPRODUCTIVE CAPABILITIES?
Currently, dairy producers can use genomic evaluations for productive, reproductive, health, sustainability, and type traits to help them identify females in their herd with the best genetics to use in a donor program; however, evaluations that help producers identify the best donor females in their herd based on the number of embryos they are likely to produce do not exist. The reproductive traits included in genomic evaluations such as Daughter Pregnancy Rate (DPR), Expected First Calving (EFC), Cow Conception Rate (CCR), and Heifer Conception Rate (HCR) are lowly heritable (Figure 1) and are not highly correlated with embryo production. Accurate estimates of donors’ genetic potential can have a significant impact on the number of viable embryos that can be produced for each cow. This is why it is imperative that producers with IVF/MOET programs are able to access reproductive genomic evaluations specifically identifying genetic potential for favorable donor traits.
*https://www.ars.usda.gov/ARSUserFiles/80420530/Publications/ARR/nmcalc-2021_ARR-NM8.pdf
WHAT GENOMIC EVALUATIONS HAS STgenetics® DEVELOPED FOR SELECTING THE BEST DONOR FEMALES FOR AN IVF/MOET PROGRAM?
STgenetics® has a premier donor program for IVF to create our world class sire and dam lineup. For this study, we used data from over 2,800 Holstein female donors and about 15,000 super ovulation events and we observed that some donors make significantly more oocytes than other donor females in a single super ovulation event. Surprisingly, total number of oocytes produced per cow was found to be highly heritable at 35%. The average number of oocyctes produced per aspiration in our population was 13.59 with a standard deviation of 9.21 eggs. By combining the observations of number of oocytes produced by a female per ovulation event as well as the genomic data for the same females, we were able to create a genomic evaluation to predict the genetic potential for cows to produce oocytes per aspiration. We call this trait Total Oocytes (OOC) because it will predict the number of oocytes a female can be expected to produce in a single super ovulation event. This means that if a female has an OOC evaluation of 18, she is expected to produce 18 oocytes per super ovulation event. The Total Oocyte trait is now available for all Holstein females tested with GeneticVisions-ST™. The high heritability of OOC, means a higher reliability of genomic breeding values and a possibility of faster genetic progress by selecting females with superior OOC evaluations.
STgenetics® has also been recording the number and viability of embryos produced in-vitro after oocyte aspiration (VEI) and the number of embryos flushed 7-days after artificial insemination or in-vivo (VEA) at our state-of-the-art IVF facilities. The average and standard deviation of VEI and VEA in our population were 4.01 (s.d. = 4.53) and 4.52 (s.d. = 4.67), respectively. Combining phenotypes, genotypes and pedigree information for counts of viable embryos (VEI and VEA) allowed STgenetics® to create a genomic evaluation that indicates a female’s genetic ability to produce viable embryos. Genomic evaluations for VEI and VEA are now available for Holstein females tested at GeneticVisions-ST™. When assessing a female’s VEI or VEA evaluation of 18, you can expect her to produce 18 viable embryos per in-vitro fertilization or flush event. The heritabilities for these traits are 11% for VEI and 13% for VEA which means that although they have a lower heritability than OOC, they are still important traits to consider in an IVF/MOET program to improve donor performance (Figure 2).
HOW CAN PRODUCERS UTILIZE THE NEW DONOR PERFORMANCE TRAITS EVALUATED BY STgenetics®?
To help producers utilize the three new traits we have evaluated to improve donor performance, STgenetics® is introducing the Donor Output Index (DOI), which allows for the simultaneous selection of the top-performing females considering all three evaluated traits. The DOI is now available for females tested with GeneticVisions-ST™ which will allow producers to select donors based on their ability to produce oocytes and viable embryos as well as all the other important economic traits available through genomic testing. The weights for the different traits in the DOI are based on the relative heritability contribution of each trait to each other. The index is then calculated using the equation shown in (Figure 3).
By including the three traits into an index, producers who use female reproductive technologies can identify the potential donors that will produce not only more offspring which is directly related to the number of total oocytes produced after superovulation, but also a higher number of viable embryos (Figure 4). This innovative index is an important tool to help producers choose which of their top genetic females to use as donors in their IVF programs. A successful IVF/MOET program will allow producers to rapidly accelerate genetic gain in their herd as well as potentially sell high value embryos for a profit.
