title: Evaluation of 2 sources of Angus cattle under South Florida subtropical conditions.
abstract: The objective of this study was to compare performance and aspects of adaptability attributes of cattle from a Florida Angus bloodline (local source from a mostly closed herd for over 50 yr) to cattle that are representative of modern Angus bloodlines (outside source) in US subtropical conditions. Embryos from both sources were transferred to Brahman-crossbred cows in South Florida, and calves (n=82) were born in 3 yr. Before weaning, summer tympanic temperatures were recorded hourly for 3 d in each year. Heifers were placed with fertile bulls until diagnosed pregnant. Traits relative to sexual maturation of bulls were recorded at 1- or 2-mo intervals until approximately 17 mo of age. Calves from outside sources had greater hip height at weaning than calves from the local source (P<0.001; 108.8 ± 0.62 and 104.7 ± 0.68 cm, respectively). Local-source calves (n=37) had greater (P=0.03) exit velocity (2.7 ± 0.3 m/s) than outside-source (n=45) calves (2.0 ± 0.29 m/s), which may be indicative of more nervous or temperamental disposition. However, no source differences were detected for other assessments of disposition (chute or pen score, P>0.8). Few source differences for minimum, maximum, or range of daily tympanic (inner ear) temperatures were detected. At 17 mo of age, outside-source heifers were heavier (P = 0.05) and had greater (P<0.001) hip height than Angus heifers from the local source. Heifers from the outside source were younger (P<0.001) at the time of their first conception (454 ± 17.5 d) than heifers from the local source (550 ± 16.9 d). Outside-source heifers also had greater (P<0.02) pregnancy and calving rates (0.7 ± 0.119 and 0.62 ± 0.125, respectively) from exposure to bulls within a year from weaning than the heifers from the local source (0.29 ± 0.089 and 0.19 ± 0.077, respectively). Bulls from the outside source were heavier (P=0.05) at 320 d of age than local-source bulls. From 14 through 17 mo of age, outside-source bulls had greater (P≤0.05) scrotal circumference and tended (P≤0.15) to be heavier than local-source bulls. There appeared to be no performance or adaptation advantages for the local-source Angus through 17 mo of age. The large source difference for age at first conception in heifers merits additional attention and comparison with cow lifetime production performance for the 2 sources.
authors.affiliation: Subtropical Agricultural Research Station, USDA, ARS, Brooksville, FL 34601, USA. d-riley8@tamu.edu
authors.forename: D G
authors.initials: DG
authors.lastname: Riley
authors.forename: J D
authors.initials: JD
authors.lastname: Arthington
authors.forename: C C
authors.initials: CC
authors.lastname: Chase
authors.forename: S W
authors.initials: SW
authors.lastname: Coleman
authors.forename: J L
authors.initials: JL
authors.lastname: Griffin
authors.forename: D O
authors.initials: DO
authors.lastname: Rae
authors.forename: T L
authors.initials: TL
authors.lastname: Mader
authors.forename: T A
authors.initials: TA
authors.lastname: Olson
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D002417:Cattle; D004777:Environment; D005260:Female; D005431:Florida; D006813:Humidity; D008297:Male; D011247:Pregnancy; D012098:Reproduction / Q000235:genetics / Q000502:physiology; D012741:Sexual Maturation / Q000235:genetics* / Q000502:physiology; D013997:Time Factors