Session: Late-Breaking Ruminant Nutrition

519 - Late-Breaking: Evaluation of the 7 & 7 Synch and Bee Synch II protocols for control of the estrous cycle among cows of varying percentage Bos indicus influence

Saturday, July 17, 2021

3:00 PM – 3:15 PM EST

Location: Kentucky International Convention Center (KICC), M101 & 102

Presenting Author(s)

CA

Carson M. Andersen, n/a

Graduate Student
University of Missouri
FALLON, Nevada

Author(s)

Matthew P. Holton, n/a

Graduate Student
University of Georgia
Athens, Georgia
Pedro Fontes, PhD

Assistant Professor
University of Georgia
Athens, Georgia
Jordan M. Thomas, Ph.D.

Assistant Professor
University of Missouri
Columbia, Missouri
LG

Lucas Goncalves

Federal University of Uberlandia
Uberlandia, Minas Gerais
SB

Samir Burato

Sao Paulo State University
Botucatu, Sao Paulo

The 7 & 7 Synch and Bee Synch II protocols for control of the estrous cycle were compared among cows with varying percentages of Bos indicus influence. Angus (n = 48), ⅛ - ¼ Brahman-influenced (n = 90), Brangus (n = 11), and ½ Brahman-influenced (n = 56) cows were blocked based on breed, age, and days postpartum and randomly assigned to treatment. Cows treated with 7 & 7 Synch (n = 104) received prostaglandin F₂_α (PG; 25 mg dinoprost tromethamine) and insertion of an intravaginal progesterone-releasing insert (CIDR; 1.38g progesterone) on Day -17, gonadotropin-releasing hormone (GnRH; 100 μg gonadorelin) on Day -10, and PG coincident with CIDR removal on Day -3. Cows treated with Bee Synch II (n = 101) received PG coincident with CIDR insertion on Day -8 and PG coincident with CIDR removal on Day -3. Fixed-time artificial insemination was performed on Day 0 at 66 h. Ovarian ultrasound was performed on Day -3 to assess presence of corpora lutea (CL) and diameter of the largest ovarian follicle (LFD), and color Doppler was used on Day 7 to assess CL blood perfusion. A greater proportion of 7 & 7 Synch cows (P < 0.0001) had CL on Day -3 (83%; 86/104) compared with Bee Synch II cows (48%; 48/101). On Day -3, LFD did not differ among Bos indicus-influenced cows treated with Bee Synch II (12.5±0.3 mm), Bos indicus-influenced cows treated with 7 & 7 Synch (12.2±0.3 mm), or Angus cows treated with 7 & 7 Synch (12.1±0.6 mm); however, greater LFD was observed among Angus cows treated with Bee Synch II (15.4±0.8 mm). Brangus cows had greater periphery signal percentages (P = 0.02) when treated with 7 & 7 Synch compared with Bee Synch II. In conclusion, across cow of varying percentage Bos indicus influence, 7 & 7 Synch resulted in a greater proportion of cows with CL on Day -3.