Adrenal function, blood metabolites, hematological parameters, growth, and
carcass characteristics were compared in tropically-adapted (Brahman,) intermediate
(Bonsmara and Bonsmara X Angus crossbred,) and temperate (Angus; n=10 each) beef
steers. An adrenal gland challenge was conducted, entailing serial blood collection at
15-min intervals for a 12.5-h period, with administration of exogenous ACTH (0.1 IU/kg
BW) 2.5-h into the experiment. Steers were maintained on Coastal bermudagrass
pastures overseeded with ryegrass for five month; body weights and blood samples were
obtained every 21 days.
An anterior pituitary/adrenal gland challenge was conducted, entailing serial
blood collection at 120, 90, 60 and 30 min prior to, and 10, 20, 30, 60 and 120 min
following administration of exogenous CRH (0.1 ug/kg BW).
Physical and physiological signs of heat stress were assessed, and blood samples
were obtained for analysis. Exit velocity was measured. Carcass characteristics were
determined post-slaughter. Statistical analysis was conducted using ANOVA for repeated measures, using
least square means and PearsonâÂÂs and SpearmanâÂÂs correlation analyses. Bonsmara and
Bonsmara X Angus had lower basal cortisol (CS) than Angus and Brahman steers.
Angus steers had greater adrenal responsiveness to ACTH, and responded faster to CRH
than the other breedtypes. Bonsmara steers were slower in responding to CRH, and
returning to basal CS following ACTH or CRH administration.
Angus and Bonsmara X Angus grew faster during the finishing phase than
Brahman or Bonsmara steers. Angus had higher quality grades than other breedtypes;
rib-eye area and hot carcass weight were greater in Angus than Brahman steers, but
similar among Angus, Bonsmara X Angus and Bonsmara steers. Angus and Brahman
were less docile than Bonsmara and Bonsmara X Angus steers.
Angus steers had higher respiration rates and serum concentrations of sodium,
lower aldosterone during moderate heat exposure, and lesser serum concentrations of
glucose, urea and cholesterol than tropically-influenced breedtypes. Angus had rectal
and surface temperatures similar to those of Brahman, but greater than those of
Bonsmara X Angus or Bonsmara steers.
Intermediate breedtypes like the Bonsmara provide a compromise to producers,
allowing them to address the demands of consumers while raising cattle better suited to
survival in tropical climates.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4435 |
| Date | 30 October 2006 |
| Creators | Jacobs Hollenbeck, Regina |
| Contributors | H., Welsh Jr., Thomas |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 569362 bytes, electronic, application/pdf, born digital |
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