Abstract #W110

Section: Reproduction (posters)
Session: Reproduction 1
Format: Poster
Day/Time: Wednesday 7:30 AM–9:30 AM
Location: Exhibit Hall A

# W110
Effects of parity, season and region on fertility of lactating dairy cows submitted to a Double-Ovsynch protocol for first timed-AI.
R. Mur-Novales^*1, P. M. Fricke², V. E. Cabrera², J. O. Giordano³, M. C. Wiltbank², J. P. N. Martins⁴, ¹Independent Dairy Data Analyst, Huesca, HU, Spain, ²Department of Dairy Science, University of Wisconsin-Madison, Madison, WI, ³Department of Animal Science, Cornell University, Ithaca, NY, ⁴School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI.

Our objective was to determine the effects of parity, US region and season on pregnancy per AI (P/AI) in lactating dairy cows submitted to Double-Ovsynch (DO) for first timed AI (TAI). Records for first TAI events (60 to 97 DIM; n = 19,298) of cows submitted to DO TAI were collected from on-farm computer records from farms in CA (n = 3), NY (n = 2), and WI (n = 5) between May 2016 and April 2017. Average herd size was 2,355 lactating cows (range: 892 to 3,632 cows). The average submission risk to DO for first AI in the studied farms was 90.9% (n = 21,210). Overall, P/AI was 44.5% and ranged from 37.5% to 54.2% among farms. Logistic regression was used to test the effect of parity (1, 2, and ≥3), region, season of TAI, and region × season of TAI interaction within parity. Primiparous cows (48.4%) had more P/AI (P < 0.01) than cows in parity 2 (42.5%) and parity ≥3 (40.8%). Cows in CA (40.8%) had a fewer P/AI (P < 0.01) than cows in NY (45.6%), and WI (46.8%). Primiparous cows from CA farms had fewer P/AI when TAI occurred during the summer than other seasons; however, season did not affect P/AI in primiparous cows from NY and WI dairies (Table 1). Regardless of region, parity-2 cows receiving TAI during summer had fewer (P < 0.01) P/AI than cows receiving TAI during winter and spring. Cows of parity ≥3 in CA had fewer P/AI during all TAI seasons than cows of parity ≥3 in NY and WI except during the summer when cows of parity ≥3 in NY and WI had fewer P/AI than in other TAI seasons. In conclusion, cows submitted to first TAI after DO had overall high P/AI across a wide variety of parities, regions and TAI seasons. Moreover, TAI season did not affect P/AI of primiparous cows submitted to DO for first TAI in the Midwest and Northeast US. Table 1 (Abstr. W110). Effects of region and season within parity on P/AI

Parity	State	P/AI, %
Winter	Spring	Summer	Autumn
1	CA	47.1^a	40.5^b	33.1^c	45.6^b
	NY	48.8^a	49.0^a	44.7^ab	47.6^ab
	WI	53.8^a	51.6^a	52.2^a	52.2^a
2	CA	43.7^ab	41.1^b	34.5^c	39.3^b
	NY	46.7^a	41.6^b	38.8^b	46.6^a
	WI	46.1^a	48.9^a	37.2^bc	45.9^a
≥3	CA	39.8^b	33.7^c	38.6^b	36.0^b
	NY	42.5^b	44.0^ab	38.8^b	51.6^a
	WI	48.0^a	45.9^a	35.6^b	41.4^ab

^a–cMeans within parity with different superscripts differ (P < 0.05).

Key Words: double-Ovsynch, fertility, timed AI