Linear Additivity of Multiple Concurrent Environmental Stressors' Effects on Chick Performance, Physiology, Histopathology, and Behavior

Whether concurrent stressors synergize in affecting chicks was studied. Results suggest stressors affected chicks in similar fashion when acting singly or together; i.e., effects were additive. Experiment I. New Hampshire x Columbian chicks were studied via 2$\sp{4}$-factorial of aerial ammonia (A, O or 125 ppm), beak-trimming (B, sham or trimmed trial d 1), coccidiosis (C, O or 4 $\times$ 10$\sp{5}$ sporulated E. acervulina oocysts d 1), and heat (H, air 30.4 or 36.5 C). Five 7-d trials had 15 6-chick replicates of 16 treatments. All stressors decreased chick weight gain (G), feed intake (F), and G/F, except B for G/F; A x C for G was only interaction. A, C, and H increased s$\sp{2}$/x for G among chicks in treatment groups (CV-G). As stressor number (order) rose from 0 to 4, G, F, and G/F fell, and CV-G rose, linearly. D-7 heterophil %/lymphocyte % (h/l) rose due to all stressors and linearly with order. Only C affected blood total-cell fraction. Experiment II. Hubbard chicks were studied via 2$\sp{6}$-factorial of A and B (as Exp. I), C (0 or 6 $\times$ 10$\sp{5}$ oocysts as Exp. I), random electric shock (E, O or 3-10 mA), H (air 30.4 or 34.8 C), and continuous white noise (N, 80 or 95 dB). Four 7-d trials had 6 3-chick replicates of 64 treatments. All stressors but N decreased G, F, and G/F and increased CV-G; few interactions were found. As order rose from 0 to 6, G, F, and G/F fell linearly. No treatment affected d-7 plasma corticosterone. C increased carcass-water content and decreased chloroform/methanol-extract, A increased crude-protein, and C decreased carcass-energy; few interactions were found. Order did not affect composition. C increased standing and eating, H decreased drinking, times; few interactions were found. C damaged kidneys and duodenal mucosa; H mitigated the lesions. N caused, and synergized positively with C for, duodenal lesions. A caused, but H mitigated, hepatic lesions. Order affected no lesion score.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Animal Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Mcfarlane, James Michael

• Agriculture, Animal Culture and Nutrition

Identifier

(UMI)AAI8721710

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/70051