Abstract #107
Section: Reproduction (orals)
Session: Reproduction 1
Format: Oral
Day/Time: Monday 10:15 AM–10:30 AM
Location: Room 207/208![](/2019/images/btn-find-it.png)
Session: Reproduction 1
Format: Oral
Day/Time: Monday 10:15 AM–10:30 AM
Location: Room 207/208
![](/2019/images/btn-find-it.png)
# 107
Investigating reproductive traits in cows with high and low genetic merit for fertility in a seasonal, pasture-based system.
S. Meier*1, B. Kuhn-Sherlock1, P. R. Amer2, J. Bryant1,3, J. R. Roche1,4, C. R. Burke1, 1DairyNZ Limited, Hamilton, New Zealand, 2AbacusBio Limited, Dunedin, New Zealand, 3AgResearch, Hamilton, New Zealand, 4Ministry of Primary Industries, Wellington, New Zealand.
Key Words: puberty, reproduction, genetic fertility
Investigating reproductive traits in cows with high and low genetic merit for fertility in a seasonal, pasture-based system.
S. Meier*1, B. Kuhn-Sherlock1, P. R. Amer2, J. Bryant1,3, J. R. Roche1,4, C. R. Burke1, 1DairyNZ Limited, Hamilton, New Zealand, 2AbacusBio Limited, Dunedin, New Zealand, 3AgResearch, Hamilton, New Zealand, 4Ministry of Primary Industries, Wellington, New Zealand.
We investigated novel, early reproductive phenotypes to accelerate the rate of genetic gain for fertility by examining reproductive phenotypes in dairy cows with divergent genetic merit for fertility in a seasonal, pasture-based dairy system. Two groups of heifers (n = 550) with high (+5.0%) or low (−5.1%) fertility breeding values (FertBV) via custom mating. The FertBV were based on parent averages for submission rates in lactations 1 to 3, calving rate in lactations 2 to 4, with body condition and milk production in lactation 1 as correlated traits. The high and low FertBV groups were managed together from 9 d old and were balanced for live weight and milk production trait breeding values, and % North American ancestry. We report heifer reproductive traits to seasonal breeding, and submission and pregnancy rates during lactations 1 and 2. Heifers with high FertBV attained puberty at an earlier age (358 d vs 379 d old, SED 6.0 d; P < 0.01) and a lighter live weight (271 kg vs. 296 kg, SED 4.3 kg; P < 0.01), and had a 9% greater 6-wk pregnancy rate, compared with low FertBV heifers (90% vs. 81%, SED 3.1%, P < 0.02). Lactation 1 had 257 high and 224 low FertBV cows and lactation 2 had 203 high and 121 low FertBV cows. During lactation 1, we mated more high FertBV cows during the first 3-wk of breeding compared with low FertBV cows (87% vs 48%; SEM 3.7%; P < 0.01). The 6-wk pregnancy rate was 67% for the high and 33% for the low FertBV cows (SEM 3.3%; P < 0.01), respectively. In lactation 2, the average calving date for the low FertBV cows was10 d later than the high FertBV cows, reflecting their poorer reproductive performance in lactation 1. The 3-wk submission (88% vs 63%; SEM 5.4%; P < 0.01) and 6-wk pregnancy rates (74% vs 44%; SEM 5.1%; P = 0.13) were greater in the high compared with low FertBV cows, respectively. In the absence of reproductive interventions, the differencesin reproductive performance between groups in their first and second lactation were greater than predicted from their difference in Fert BV. The difference in reproductive performance between the FertBV groups validates the relevance of the FertBV and indicates puberty attainment is a candidate trait for genetic selection.
Key Words: puberty, reproduction, genetic fertility