2 results
Nonlinear analysis of heart rate variability for evaluating the growing pig stress response to an acute heat episode
- C. J. Byrd, J. S. Johnson, J. S. Radcliffe, B. A. Craig, S. D. Eicher, D. C. Lay, Jr.
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Heart rate variability (HRV) is a proxy measure of autonomic function and can be used as an indicator of swine stress. While traditional linear measures are used to distinguish between stressed and unstressed treatments, inclusion of nonlinear HRV measures that evaluate data structure and organization shows promise for improving HRV interpretation. The objective of this study was to evaluate the inclusion of nonlinear HRV measures in response to an acute heat episode. Twenty 12- to 14-week-old growing pigs were individually housed for 7 days and acclimated to thermoneutral conditions (20.35°C ± 0.01°C; 67.6% ± 0.2% RH) before undergoing one of the two treatments: (1) thermoneutral control (TN; n = 10 pigs) or (2) acute heat stress (HS; n = 10 pigs; 32.6°C ± 0.1°C; 26.2% ± 0.1% RH). In Phase 1 of the experimental procedure (P1; 60 min), pigs underwent a baseline HRV measurement period in thermoneutral conditions before treatment [Phase 2; P2; 60 min once gastrointestinal temperature (Tg) reached 40.6°C], where HS pigs were exposed to heated conditions and TN pigs remained in thermoneutral conditions. After P2, all pigs were moved back to thermoneutral conditions (Phase 3; P3; 60 min). During each phase, Tg data were collected every 5 min and behavioural data were collected to evaluate the amount of time each pig spent in an active posture. Additionally, linear (time and frequency domain) and nonlinear [sample entropy (SampEn), de-trended fluctuation analysis, percentage recurrence, percentage determinism (%DET), mean diagonal line length in a recurrence plot] HRV measures were quantified. Heat stressed pigs exhibited greater Tg (P = 0.002) and spent less time in an active posture compared to TN pigs during P2 (P = 0.0003). Additionally, low frequency to high frequency ratio was greater in HS pigs during P3 compared to TN pigs (P = 0.02). SampEn was reduced in HS pigs during P2 (P = 0.01) and P3 (P = 0.03) compared to TN pigs. Heat stressed pigs exhibited greater %DET during P3 (P = 0.03) and tended to have greater %DET (P = 0.09) during P2 than TN pigs. No differences between treatments were detected for the remaining HRV measures. In conclusion, linear HRV measures were largely unchanged during P2. However, changes to SampEn and %DET suggest increased heat stress as a result of the acute heat episode. Future work should continue to evaluate the benefits of including nonlinear HRV measures in HRV analysis of swine heat stress.
The Influence of Fluometuron and MSMA on Cotton Yield and Fruiting Characteristics
- Charles E. Snipes, J. D. Byrd, Jr.
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- Journal:
- Weed Science / Volume 42 / Issue 2 / June 1994
- Published online by Cambridge University Press:
- 12 June 2017, pp. 210-215
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Field experiments conducted from 1987 through 1991 at the Delta Branch Experiment Station, Stoneville, MS, determined the effect of postemergence topical applications of fluometuron and MSMA on cotton yield and fruiting. Herbicide treatments applied to cotton in the cotyledon to 1-leaf growth stage were 1.12 kg ai ha-1 fluometuron plus 0.25% by vol nonionic surfactant, 2.2 kg ai ha-1 MSMA, and a combination of 1.12 kg ha-1 fluometuron and 2.24 kg ha-1 MSMA. The commercial formulation of MSMA contained nonionic surfactant. Visual injury of cotton 14 d after treatment ranged from 14 to 28% for fluometuron, 9 to 26% for MSMA, and 22 to 34% for the combination. Seed cotton yield at the first harvest was reduced by all herbicide treatments except in 1987 and for DES 119 cotton in 1990. In 1990, yield of DES 119 cotton treated with MSMA and the combination was less than the untreated control for the second harvest interval. Cotton yield from herbicide treatments at later harvests was equal to or greater than the untreated control. Only in 1988 did all treatments reduce total seed cotton yield below the untreated control. Fiber quality was not adversely affected by the herbicides. Compared to the control, plant mapping indicated that the number of sympodial branches per plant was reduced by MSMA and by the combination for DPL 50 cotton in 1990. Averaged over 4 experiment years, herbicide treatments did not reduce total bolls per plant; percentage of bolls in first, second, or outer positions; highest sympodium with two bolls; or number of sympodium with bolls in the first or second position. However, MSMA and the combination increased node number of the first sympodia by one and 1.5 positions, respectively, when compared to the control, indicating delayed maturity.