Physiological reproductive status and progesterone concentration affect the results of tests to measure temperament traits in female beef cattle

Abstract

Two studies were performed to determine (1) the role of endogenous progesterone (P4) concentration during the follicular, luteal and mid gestation phases of zebu type cattle (B. indicus) in the response to the exit velocity (EV) and flight distance (FD) tests and (2) the response of non-cyclic female beef heifers (B. taurus) to the same tests during treatments with P4 and immediately after P4 withdrawal. In Study 1, 31 Brahman cows; 17 pregnant and 14 cycling were used. Previous to the study, all cycling animals were treated with 2 PGF2α injections, 11 days apart. Exit velocity and FD were performed in cycling cows, at days 11 and 21 of their natural cycle after the induced oestrous (day 0), and at day 125.9 ± 1.8 days (range: 117 to 139)] in the pregnant cows. The EV was slower and the FD was shorter in pregnant cows than in the cows in their luteal phase (EV: 0.83 ± 0.07 m.s−1 vs. 0.55 ± 0.06 m.s−1: P = 0.007; FD: 3.8 ± 0.4 m vs. 2.6 ± 0.5 m: P = 0.05 for cows in their luteal phase and gestating cows respectively). In Study 2, 24, 9-m old Hereford-Aberdeen Angus cross heifers were used. Twelve heifers were treated with P4 intravaginal releasing devices (CIDR, 1.38 g of P4, Pfizer, Auckland, NZ) for 5 days (P4G), and other 12 heifers remained as untreated controls (CG). The EV and FD were assessed in both groups before inserting the CIDR, 1 and 5 days after the treatment began, and 16 h after devices removal. Before placing the CIDRs there were no differences in the EV or FD. One day after CIDRs were inserted, FD was shorter in P4G than in CG heifers (5.0 ± 0.8 m vs. 7.0 ± 0.6 m, P = 0.04). Sixteen h after CIDRs removal the EV was greater in P4G than in CG heifers (2.2 ± 0.5 m.s−1 vs 1.2 ± 0.1 m.s−1, P = 0.05), and FD tended to be greater in P4G than in CG heifers (4.1 ± 0.5 m vs. 3.2 ± 0.4 m, P = 0.09). In conclusion, female zebu type cattle (B. indicus) reacted less during mid-gestation than during their mid-luteal phase when they were subjected to two tests to measure temperament traits. Additionally, female beef calves (B. taurus) also responded less to those tests when they were treated with P4, and they responded more immediately after P4 withdrawal.