PSIII-7 - Effect of time of estrus on conception rate for a sexed semen artificial insemination protocol in multiparous beef cows

Tuesday, July 18, 2023

9:45 AM – 11:00 AM MT

Location: 140 Aztec/110 Galisteo

Presenting Author(s)

Emily E. Efird

Graduate Research Assistant
West Texas A&M University
Canyon, Texas, United States

Author(s)

Ty E. Lawrence, PhD

Professor of Animal Science and Director of the Beef Carcass Research Center
West Texas A&M University
Canyon, Texas, United States
JR

John T. Richeson, PhD

Associate Professor of Animal Science
West Texas A&M University
Canyon, Texas, United States
WW

Wyatt E. Weber

Graduate Student
University of Arkansas
Fayetteville, Arkansas, United States
CL

Charles R. Looney

University of Arkansas
Hope, Arkansas, United States
Tommy L. Perkins, PhD

Associate Professor of Animal Science
West Texas A&M University
Canyon, Texas, United States

Abstract: Abstract: Sexed semen artificial insemination is a breeding technique that allows producers to shorten breeding seasons, optimize genetics through use of superior semen, create calves based on sex preference, and increase profitability. Sexed semen is a technology that sorts semen by differences in DNA content between X (female) and Y (male) bearing sperm. However, sexed semen practices have yet to be widely used in beef cows due to reduced sperm numbers, low conception rates, and increased costs. The objective of this study was to determine the effect of time of estrus upon fixed-time artificial insemination (FTAI) of sex-sorted semen on conception rate using two different estrous synchronization protocols. Multiparous commercial beef cows (n = 73) were randomized by age, body condition score (BCS), and days post-partum at the University of Arkansas Livestock and Forestry Research Station in Batesville. Both synchronization treatments (TRT) used a controlled internal drug releasing device (Eazi-breed CIDR; 1.38g progesterone) inserted intravaginally on d -14 of the protocol simultaneous to administration of prostaglandin F2α (PGF; 500µg cloprostenol sodium; Estrumate). In the first treatment (TRT 1; 7&7 Synch), gonadotropin-releasing hormone (GnRH; 86µg gonadorelin; Fertagyl) was administered on d -7. In the second treatment (TRT 2; 8&6 Synch), GnRH was administered on d -6. Both treatments were then administered PGF simultaneous to CIDR removal on d 0, 66±2h prior to FTAI and administration of GnRH. Standing heat (estrus) was visually detected every 3h for 30m intervals between CIDR removal and FTAI. Heat detection patches were used in conjunction with visual detection of estrus. Time of estrus was signified as time of standing immobile when mounted in combination with presenting a patch score of 4 ( >75% color removed). Time of estrus (TD) was deviated from time of FTAI and categorized into three equal time groups (Grp 1 = 0 to 11.0 h; Grp 2 = 11.01 to 22.0 h; and Grp 3 = 22.01 to 33.0 h). Conception rate (CR) was determined via ultrasound 37±2d after FTAI. Data was analyzed using the GLIMMIX procedure of SAS 9.4. CR did not differ by age of dam (P = 0.58), BCS (P = 0.48), or TRT (P = 0.83). However, TD had a highly significant effect on CR (P = 0.002); and resulted in CR of 45% (Grp 1), 87% (Grp 2), and 42% (Grp 3). In conclusion, these results indicate artificially inseminating cows with sexed semen between 11.01 and 22.0h after time of standing estrus will increase pregnancy rates for multiparous commercial beef cattle.