Linda Benedict, Blouin, David C., Franke, Donald E., Derouen, Sidney M., Wyatt, Wayne E. | 3/6/2014 11:15:08 PM
Wayne E. Wyatt, David C. Blouin, Sidney M. DeRouen and Donald E. Franke
The effect of ill temperament on heifer growth and development would be important to assess as early in the animal’s life as possible for making decisions regarding female herd replacements. It is unknown whether assessing temperament as a newly weaned heifer at approximately 7 months of age (weanling) or at approximately 14 months of age (yearling) is best in terms of postweaning growth and conception as yearlings. The chute temperament score test and the exit velocity are easy methods for classifying animal temperament in on-farm situations. The objective of this study was to determine the effect of temperament measure types (chute score or exit velocity) and times of assessment (weaning or yearling) on heifer weaning body weight, postweaning growth, postbreeding body weight and pregnancy status.
Spring-born heifers (n = 432) reared at the Central, Hill Farm and Iberia research stations were weaned in the fall of their respective birth year (2003-2007) and retained as replacement females. On data collection days, the weanling and yearling heifers were allowed to enter the squeeze chute and were constrained, but not squeezed. Heifers were immediately scored for chute temperament behavior using a 5-point subjective scoring system: 1 = calm, stands still, no movement; 2 = slightly restless; 3 = restless, shaking the chute; 4 = vigorously shaking the chute or resolutely lying in the bottom of the chute; and 5 = extremely frenetic and severely shaking the chute.
Based on the chute score, cattle scoring 1 and 2 were classified as calm; cattle scoring 3 were classified as intermediate; and cattle scoring 4 and 5 were classified as ill-tempered. The front gate was subsequently opened, allowing the heifer to exit. Heifers exited straight ahead into a fenced lane, which led to a loafing pen. Infrared sensors were used to remotely trigger the start and stop of a timing apparatus, and an exit velocity was calculated. Based on exit velocity taken as weanlings and yearlings, heifers were classified as slow (average velocities of 5.5 and 5.0 feet per second), moderate (average velocities of 8.6 and 8.7 feet per second) or fast (average velocities of 12.3 and 16.1 feet per second).
Heifer body weight was similar across chute score for both the weanling and yearling assessments (Figure 1). Heifer body weight at weaning was significantly affected by both the weanling and yearling assessment of exit velocity. In the weanling assessment, weaning weights were similar for “slow” and “moderate” heifers but were less for the “fast” heifers than for the “moderate” heifers. In the yearling assessment, “slow” heifers were heavier at weaning than “moderate” heifers, but weaning weights were similar between “moderate” and “fast” heifers.
While the weanling assessment of chute score resulted in similar postweaning weight gains across chute score classes, “calm” heifers gained at a faster rate than did “intermediate” heifers in the yearling assessment (Figure 2). Exit velocity taken as weanlings significantly affected heifer postweaning growth. Although “slow” and “moderate” heifers had similar growth rates, there was a tendency for “moderate” heifers to gain at a faster rate than “fast” heifers. There was a tendency for exit velocity, assessed as yearlings, to affect heifer postweaning growth rate, with “slow” heifers tending to gain at a faster rate than “moderate” heifers, whereas “moderate” and “fast” heifers had similar postweaning growth rates.
Postbreeding (approximately 16-18 months of age) body weights of heifers were similar among the “calm,” “intermediate” and “ill-tempered” chute scores assessed as weanlings, but “calm” heifers were heavier than “intermediate” heifers assessed as yearlings (Figure 3). Exit velocity significantly affected heifer postbreeding body weight in both the weanling and yearling assessments; “slow” heifers were heavier than “moderate” heifers, and “moderate” heifers were heavier than “fast” heifers.
Pregnancy rates were similar across chute score and exit velocity classes assessed as either weanlings or yearlings (Figure 4). The only factor affecting differences in pregnancy rate was associated with a tendency for “intermediate plus ill-tempered” heifers to have greater pregnancy rates than their “calm” counterparts, which was unexpected and inexplicable.
The importance of enhanced pre- and postbreeding body weights and postweaning growth rates on heifer development and subsequent pregnancy rates is well-documented. In this study, it was apparent that the exit velocity measures taken at calf weaning were sufficient in eliciting differences in weaning and postbreeding heifer body weights and in postweaning growth rates. This means that producers can evaluate heifers at weaning time and cull “fast” heifers as herd replacements based upon exit velocity. The equipment necessary for measuring exit velocity is relatively inexpensive and easily assessed by producers interested in retaining heifers from their own herd as replacement females.
Wayne E. Wyatt is a professor at the Iberia Research Station, Jeanerette, La. David C. Blouin is a professor in Department of Experimental Statistics. Sidney M. DeRouen is a professor, now retired, at the Dean Lee Research and Extension Center, Alexandria, La. Donald E. Franke is a professor emeritus in the School of Animal Sciences.
(This article was published in the 2014 winter issue of Louisiana Agriculture magazine.)