Source: UNIVERSITY OF FLORIDA submitted to
RAISING THE CALF CROP IN FLORIDA BEEF CATTLE
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0185634
Grant No.
(N/A)
Project No.
FLA-VME-03878
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Jul 1, 2000
Project End Date
Jun 30, 2006
Grant Year
(N/A)
Project Director
Rae, D. O.
Recipient Organization
UNIVERSITY OF FLORIDA
G022 MCCARTY HALL
GAINESVILLE,FL 32611
Performing Department
COLLEGE OF VETERINARY MEDICINE
Non Technical Summary
Florida, despite enjoying a subtropical climate and nearly year-round grazing, has one of the lowest average calf crops in the continental U.S.; being approximately 76% which is more than 10% below the national average. Contributing factors include the stress of a hot, humid environment and the presence of large numbers of Bos indicus derived cattle. This project aims to identify and characterize a number of female-related factors which contribute to reproductive efficiency in beef cattle.
Animal Health Component
100%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
3013310102050%
3113310110025%
3113310110325%
Goals / Objectives
Objectives: To evaluate methods of assessing reproductive performance in beef cattle in Florida, focusing on factors such as age, phenotype, nutrition, production measures and environmental stressors. To ascertain the best combination(s) of production traits for optimal female selection and management in Florida. To identify biostimulatory effects on female reproduction traits (such as age at puberty and postpartum return to estrus) in Florida beef cattle. To identify and quantify the effects of infectious disease processes on Florida calf crop, commencing with the development of an epidemiological model for Ureaplasmosis and Trichomonosis.
Project Methods
Assessing Reproductive Performance. Examination of the relationships between pregnancy rate, calving interval, body condition score prebreeding, body condition score at pregnancy examination, change in body condition score (spring to fall) and lactational state in four beef breeds in a subtropical environment will be assessed, focusing on the primiparous cow. Data was collected over 5 years from approximately 450 beef cows per year. Data will be analyzed. The statistical model will include: pregnancy rate, calving interval, breed, body condition-spring and fall, change in body condition score and lactational state. Ascertain traits optimal for female selection and management in Florida. Heifer reproductive traits will be obtained at cooperating sites. Data will include age, frame score, body condition score and weight at breeding, and pregnancy rate per cycle. Additional data will include reproductive tract scores, blood progesterone values at breeding, pelvic measures, calf weight and vigor. Bull reproductive data will include breeding soundness parameters and performance traits. Data will be analyzed for age and weight variations. Identify biostimulatory effects on female reproduction traits. Biostimulation is the stimulatory effect generated by the presence of the male on the sexual status of the female. The objective of this study is to assess the effect of biostimulation on reproductive efficiency in beef cows. The study will be conducted prior to and during the breeding season. Within a week of parturition, cows will be allocated to 3 groups and placed on separate pastures. Cows in Group A (n=30) will be placed with an epidydectomized bull (teaser); cows in Group B (n=30) will be placed with another teaser bull; and, cows in Group C (n=30) will serve as controls (no bull). The effect of biostimulation on uterine involution will be assessed by palpation of the uterus per rectum and ultrasonography. The effect of biostimulation on resumption of ovarian activity and cyclicity will be assessed by ovarian ultrasonography, blood progesterone and estradiol concentrations. Pregnancy will be diagnosed using blood progesterone, ultrasonography, and rectal palpation. The effect, of biostimulation on pregnancy will be calculated. Epidemiological Models of Infectious Disease Effects. Infectious disease processes can have dramatic effects on the beef cattle production. Assessment of the effects of disease, and its economic impact, requires the development of a suitable epidemiological models to describe observations in the field. Few models are available or suitable for modeling the extensively managed beef herds in areas such as Florida. Thus, this component of the study will attempt to develop such a model, using Tritrichomonas fetus as the infectious agent. The finding of high prevalence of infection on a major Florida beef ranch and several herd outbreaks in the past several years has provided data and the catalyst to commence the epidemiological model of this disease.

Progress 07/01/00 to 06/30/06

Outputs
Chlortetracycline in an ad libitum trace mineral salt mix prior to bull exposure was found to be associated with an increased proportion of females pregnant and a reduced time to conception. Other factors which were found to be associated with proportion pregnant were change in body condition score, average daily gain and reproductive tract score. Prevalence of and factors associated with Tritrichomonas fetus in bull populations in the state of Florida was reported. Tritrichomonas fetus infection continues to be prevalent within the natural service beef herds of Florida. The likelihood of disease is greatest in larger herds in more extensive management settings, such as South Florida. T. fetus infection in natural service beef herds in Florida was associated with bull (age, breed), herd and herd management practices. Sero-prevalence of Mycobacterium paratuberculosis (MAP) in Florida beef and dairy cattle was reported to have a true prevalence estimate of 11.2%. Although prevalence was lower than previously reported, cattle sero-prevalence appears to be wide spread. As many as 168,000 cattle in the State of Florida may be infected. In a subsequent study, Dam and calf genetic and environmental factors were evaluated for their association with enzyme-linked immunosorbent assay (ELISA) s/p ratio scores for paratuberculosis in a multibreed beef cattle population. Dams with high ELISA s/p ratio scores produced smaller calves, gained less weight (or lost more weight) during preweaning, and produced less milk, which in turn may have been the cause of calves with smaller preweaning gains. Factors identified here as associated with ELISA s/p ratio scores could help cattle producers with culling decisions related to paratuberculosis control and eradication efforts in beef cattle. In other studies, we have evaluated beef cattle postpartum management (i.e., effect of biostimulation on uterine involution, early ovarian activity and first postparum estrous cycle) and estrus synchronization protocols (i.e., synchronization of Bos indicus x Bos taurus cows for timed AI using GnRH plus PGF2a in combination with melengestrol acetate) to improve reproductive efficiency.

Impacts
Effect of Chlortetracycline. There was an improved pregnancy percentage in groups treated with CTC trace mineral 30-d prior to breeding, and a possible positive effect from feeding during the second 30-d period. Prevalence of T. fetus. Evaluation of herd and bull population prevalence indicated a significant level of trichomonosis in Florida beef bulls. Large herds of breeding-age females were at significant risk of disease, especially in South Florida. Prevalence of Mycobacterium avium subspecies paratuberculosis (MAP). We found MAP prevalent in Florida beef and dairy cattle populations. We found that a high MAP ELISA s/p ratio scores are associated with lower cow weights (and perhaps lower milk production); these were evidenced by lower calf birth weights and lower preweaning gains. Thus, although ELISA tests have low sensitivity, there is evidence of a negative impact of a positive test (i.e., a higher likelihood of subclinical paratuberculosis) on production traits of dams and calves. Factors identified as associated with ELISA s/p ratio scores could help cattle producers with culling decisions related to paratuberculosis control and eradication efforts in beef cattle.

Publications

  • No publications reported this period


Progress 10/01/04 to 09/30/05

Outputs
Johne's disease investigation: Dam and calf genetic and environmental factors were evaluated for their association with enzyme-linked immunosorbent assay (ELISA) s/p ratio scores for paratuberculosis in a multibreed beef cattle population. The linear mixed model analysis used 359 ELISA s/p ratio scores from 340 dams: Angus (A), Brahman (B), 3/4 A 1/4 B, 1/2 A 1/2 B, 1/4 A 3/4 B, and Brangus (5/8 A 3/8 B). Important dam regression effects were: 1) B - A effect was positive indicating an upward trend of ELISA scores towards 100% B dams, and 2) weight change from before calving to the date of the blood sample in May indicating a negative association between weight maintenance and ELISA scores. Relevant calf regression effects were: 1) birth weight, 2) calf gain from birth to the date of the dam blood sample, and 3) calf age on the date of the dam blood sample. Dams with high ELISA s/p ratio scores produced smaller calves, gained less weight (or lost weight) during the preweaning season, and produced less milk, which in turn may have caused calves to have smaller preweaning gains. The objective of our prior study was to estimate the prevalence of Mycobacterium avium subsp. paratuberculosis (MAP) infection among beef and dairy cattle in the State of Florida. This was a retrospective seroprevalence study on serum samples from 32,011 cattle originating from 75 herds. Selection was limited to whole herds being tested for diagnostic purposes by owners considering participation in the voluntary Johne's Control program. Data were obtained from the Florida State Veterinary Diagnostic Laboratory and USDA APHIS statewide submission of specimens for Johne's testing from 1999 to 2001. Specimens were evaluated using a commercial ELISA kits. Overall prevalence in the sample population of Florida cattle was 6.5%. Prevalence in beef and dairy cattle was found to be 7.4% and 6.3%, respectively. Eighty-three percent of herds included in the study had one or more positive cows in the herd. Larger herds (>100 head) had a statistically significant higher herd prevalence than herds with less than 100 head of cattle. The true prevalence estimate was calculated to be 11.2%. Although within herd prevalence was lower than previously reported in Florida, seroprevalence appears to be widely distributed among Florida cattle.

Impacts
Factors identified as associated with Mycobacterium ELISA s/p ratio scores could help cattle producers with culling decisions related to paratuberculosis control and eradication efforts in beef cattle. The study found high ELISA s/p ratio scores to be associated with lower cow weights (and perhaps lower milk production); these were evidenced in lower calf birth weight and lower preweaning gains. Based on these results, there appears to be a significant negative impact of subclinical paratuberculosis on production traits of dams and calves. We have previously evaluated the prevalence of Johne's disease in the Florida beef and dairy cattle population. We have assessed the level of risk for this disease in the population and potential risk factors for this disease in Florida cattle populations. We have also continued to look for methods of improved reproductive efficiency in Florida beef cows.

Publications

  • Elzo MA, Rae DO, Lanhart S, Wasdin J, Dixon P, Jones J. Factors associated with ELISA sample/positive ratio scores for Paratuberculosis in an Angus-Brahman multi breed herd of beef cattle. Proceedings 38th Annual Conv AABP 38:213 2005, abstract.
  • Elzo MA, Rae DO, Lanhart SE, Wasdin JG, Dixon WP, Jones JL. Factors associated with ELISA likelihood s/p ratio scores for paratuberculosis in an Angus-Brahman multibreed herd of beef cattle. J Anim Sci xx:xxx-xxx, 200x.
  • Landaeta-Hernandez AJ, Melendez P, Bartolome J, Rae DO, Archbald LF. Effect of biostimulation on the expression of estrus in postpartum Angus cows. Theriogenology xx:xxx-xxx, 200x.


Progress 10/01/03 to 09/30/04

Outputs
Johne's disease investigation: The objective of this study was to estimate the prevalence of Mycobacterium avium subsp. paratuberculosis (MAP) infection among beef and dairy cattle in the State of Florida. This was a retrospective seroprevalence study of samples from 32,011 cattle from 75 herds. Selection was limited to whole herds tested for diagnostic purposes by owners considering participation in the voluntary Johne's Control program. Data were obtained from the Florida State Veterinary Diagnostic Laboratory and USDA APHIS statewide submission of specimens for Johne's testing from 1999 to 2001. Specimens were evaluated using a ELISA kits. Overall prevalence in the sample population of Florida cattle was 6.5%. Prevalence in beef and dairy cattle was found to be 7.4% and 6.3%, respectively. Eighty-three percent of herds included in the study had one or more positive cows in the herd. Larger herds (>100 head) had a statistically significant higher herd prevalence than herds with less than 100 head of cattle. The true prevalence estimate was calculated to be 11.2%. Although within herd prevalence was lower than previously reported in Florida, seroprevalence appears to be widely distributed among Florida cattle. Tritrichomonas foetus disease investigation: The objectives of this study were to estimate the prevalence of herd and individual bull infection with Tritrichomonas foetus in a survey of beef bulls in the state of Florida and to perform an epidemiological investigation of risk factors for the disease. Bulls were tested for T. foetus colonization by a single preputial scraping and culture. Bull infection prevalence within herds was calculated and relationships with bull, herd factors, and production measurements were determined. The survey included 1,984 beef bulls in 59 herds throughout Florida; nine bulls in three small herds (<100 cows) were excluded from the models. An overall prevalence for T. foetus infected bulls was 6.0% (within-herd prevalence ranged from 0 to 27%). The herd prevalence was 30.4% (i.e., at least one infected bull); infected bulls were found in 11.1 and 39.5% of herds sampled in North and South Florida, respectively. The likelihood of disease was greatest in larger herds in more extensive management settings (>500 cows, 53.9% prevalence, medium-sized herds of 100 - 499 cows, 10.0% prevalence). Tritrichomonas foetus infection was associated with several bull factors- age, breed, herd and herd management practices (bull to cow ratio, bulls per breeding group). Tritrichomonas foetus infection continues to be prevalent in beef herds in Florida that use natural service. In other studies, we have evaluated beef cattle postpartum management (i.e., effect of biostimulation on uterine involution, early ovarian activity and first postparum estrous cycle), estrus synchronization protocols (i.e., synchronization of Bos indicus x Bos taurus cows for timed artificial insemination using gonadotropin-releasing hormone plus prostaglandin F2a in combination with melengestrol acetate) to improve reproductive efficiency and evaluated preweaning traits of Brahman calves especially as it relates to their growth and survival.

Impacts
We have evaluated the prevalence of Johne's disease in the Florida beef and dairy cattle population, and evaluated the prevalence of Trichomonosis in a population of Florida beef bulls. In this we have assessed the level of risk for these diseases in the population and potential risk factors for these disease in Florida cattle populations. We have also continued to look for methods of improved reproductive efficiency in Florida beef cows.

Publications

  • Keller L, Harrell CD, Loerzel SM, Rae DO. Johnes disease: Seroprevalence of Mycobacterium avium subsp. paratuberculosis in Florida beef and dairy cattle. 2004. Bovine Practitioner 38:135-141.
  • Rae DO, Crews JE, Greiner EC, Donovan GA. Epidemiology of Tritrichomonas feotus in beef bull populations in Florida. 2004. Theriogenology 61:605-618.
  • Landaeta-Hernandez AJ, Giangreco MA, Melendez P, Bartolome J, Rae DO, Bennett F, Hernandez J, Archbald LF. Effect of biostimulation on uterine involution, early ovarian activity and first postparum estrous cycle in beef cows. 2004. Theriogenology 61:1521-1532.
  • Landaeta-Hernandez AJ, Rae DO, Olson TA, Ferrer JM, Barboza M, Archbald AF. Preweaning traits of Brahman calves under dual-purpose management system in the tropics. 2004. Revista Cientifica 14:344-353.


Progress 10/01/02 to 10/01/03

Outputs
Johne's disease investigation (3): The objective of the first study (1) was to estimate the prevalence of Mycobacterium avium subsp. paratuberculosis (MAP) infection among beef and dairy cattle in the State of Florida. This was a retrospective seroprevalence study on serum samples from 32,011 cattle originating from 75 herds. Selection was limited to whole herds being tested for diagnostic purposes by owners considering participation in the voluntary Johne's Control program. Data were obtained from the Florida State Veterinary Diagnostic Laboratory and USDA APHIS statewide submission of specimens for Johne's testing from 1999 to 2001. Specimens were evaluated using a commercial ELISA kits. Overall prevalence in the sample population of Florida cattle was 6.5%. Prevalence in beef and dairy cattle was found to be 7.4% and 6.3%, respectively. Eighty-three percent of herds included in the study had one or more positive cows in the herd. Larger herds (>100 head) had a statistically significant higher herd prevalence than herds with less than 100 head of cattle. The true prevalence estimate was calculated to be 11.2%. Although within herd prevalence was lower than previously reported in Florida, seroprevalence appears to be widely distributed among Florida cattle. The objective of the second study (2) was to evaluate the level of agreement between ELISA and AGID assays for antibodies to MAP, taking into consideration the test cutoff points for the ELISA as a factor in their agreement or disagreement. A total of 1080 bovine serum samples from beef herds at University of Florida beef herds were screened. The ELISA method 1 had 8.5% agreement and the method 2 had 4.2% agreement with AGID. Two beef cow-calf herds were studied (3) to determine the association between infection with MAP and various individual and maternal animal factors. Cows older than two years of age were tested for serum antibodies against MAP using an ELISA assay. Serum samples and individual animal data for 444 cows and complete dam data for 155 of these cows was collected and analyzed. The apparent prevalence rates were calculated to be 2.7% and 17.7%. Five factors were found to be significant: herd, breed, age, pregnancy, and dam's breed. Brahman cows (when compared to Angus), cows older than four years of age, open cows (not pregnant) had a higher likelihood of testing positive. In other studies, we have evaluated beef cattle postpartum management (i.e., effect of biostimulation on uterine involution, early ovarian activity and first postparum estrous cycle) and estrus synchronization protocols (i.e., synchronization of Bos indicus x Bos taurus cows for timed artificial insemination using gonadotropin-releasing hormone plus prostaglandin F2a in combination with melengestrol acetate) to improve reproductive efficiency.

Impacts
We have evaluated the prevalence of Johne's disease in the Florida beef and dairy cattle population, evaluated some potential risk factors for the disease in beef cattle. We have also evaluated some disease test procedures. We continue to look for methods of improved reproductive efficiency in Florida beef cows.

Publications

  • Hiers EA, Barthle CR, V Dahms MK, Portillo GE, Bridges GA, Rae DO, Thatcher WW, Yelich JV. Synchronization of Bos indicus x Bos taurus cows for timed artificial insemination using gonadotropin-releasing hormone plus prostaglandin F2a in combination with melengestrol acetate. 2003. J Anim Sci 81:830-835.
  • Landaeta-Hernandez AJ, Giangreco MA, Melendez P, Bartolome J, Rae DO, Bennett F, Hernandez J, Archbald LF. Effect of biostimulation on uterine involution, early ovarian activity and first postparum estrous cycle in beef cows. 200x. Accepted Theriogenology.


Progress 10/01/01 to 10/01/02

Outputs
Epidemiology of Tritrichomonas fetus in beef bull populations in Florida. The objectives of this study were to estimate the prevalence of herd and individual bull infection with Tritrichomonas fetus in a survey of the beef bull population in the state of Florida and to perform a descriptive and analytical epidemiological investigation of risk factors for the disease. The survey included 1,994 beef bulls in 54 herds from throughout Florida. Bulls were tested for T. fetus colonization by a single preputial scraping and culture. Bull infection prevalence within herds was calculated and correlated to bull, herd / management factors, and production measurements. An overall survey prevalence for T. fetus infected bulls was 6.0% (within herd prevalence ranged from 0 to 27%). The herd prevalence was 30.4%; 11.1% of herds sampled in North Florida had infected bulls and 39.5% of herds sampled in South Florida had infected bulls. A difference by herd size was noted between medium sized herds (100 - 499 cows, 10.0% prevalence) and larger herds (500+ cows, 53.9% prevalence). Trichomonas fetus infection was associated with bull factors, including, age, breed, herd and herd management practices (bull to cow ratio, bulls per breeding group). Tritrichomonas fetus infection continues to be prevalent within the natural service beef herds of Florida. The likelihood of disease is greatest in larger herds in more extensive management settings, such as South Florida. Infection was associated with bull age, breed and herd management practices. Johne's disease: Seroprevalence of Mycobacterium paratuberculosis in Florida beef and dairy cattle. The objective of the study was to estimate the prevalence of Mycobacterium paratuberculosis infection among beef and dairy cattle in the State of Florida. Serum samples from 32,011 cattle from 75 herds were included in the study. Selection was limited to whole herds being tested for diagnostic purposes by owners considering participation in the voluntary Johne's Control Program or the voluntary Florida Johne's Disease Herd Status Program. Data was obtained from the Florida State Veterinary Diagnostic Laboratory and USDA APHIS statewide submission of specimens for Johne's testing from 1999 to 2001. Specimens were evaluated using a commercial ELISA kit with a sensitivity of 50% and specificity of 99%. Results were analyzed statistically. Overall prevalence in the sample population of Florida cattle was 6.5%. Prevalence in beef and dairy cattle was found to be 7.4% and 6.3%, respectively. 82.7% of herds included in the study had one or more positive cows in the herd. Larger herds (>100 head) had a statistically significant higher herd prevalence than herds with less than 100 head of cattle. The true prevalence estimate was calculated to be 11.2%. Although prevalence was lower than previously reported, seroprevalence appears to be widely distributed and pervasive among Florida cattle. As many as 168,000 cattle in the State of Florida may be infected. There is a need for increased awareness of the disease and implementation of control methods appropriate for each individual herd.

Impacts
Prevalence of T. fetus and M. avium paratuberculosis. Evaluation of herds and bull population prevalences indicate a significant level of these diseases in Florida cattle. Florida cattle herds are at significant risk of disease, especially in South Florida.

Publications

  • Rae DO, Ramsay KH, Morrison RL. Effect of chlortetracycline in a trace mineral salt mix on fertility traits in beef cattle females in Florida. J Anim Sci 80:880-885, 2002.
  • Landaeta-Hernandez AJ, Yelich JV, Tran T, Fields MJ, Chase CC, Lemaster JW, Rae DO, Chenoweth PJ. Environmental, genetic and social factors affecting the expression of estrus in beef cows, Theriogenology xxxx:1-14, 2002.
  • Landaeta AJ, Rae DO, Olson TA, Ferrer, JM, Barboza M Archbald L. 2002 (Aug 19-23). Pre-weaning growth and neonatal weakness in Brahman calves under tropical conditions. Proceedings of the 7th World Congress on Genetics Applied to Livestock Production, pp 717-720.
  • Landaeta-Hernandez A, Giangreco M, Melendez P, Bartolome J, Rae D, Hernanadez J, Archbald L. 2002. Effect of biostimulation on resumption of reproductive cyclicity and expression of oestrus in postpartum beef cows. Proceedings, XXII World Buiatrics Congress, p 114 (359-319).
  • Rae DO, Crews JE, Greiner EC, Donovan GA. 200x. Epidemiology of Tritrichomonas feotus in beef bull populations in Florida. pending publication.
  • Keller L, Harrell CD, Loerzel SM, Rae DO.200x. Johnes disease in Florida cattle: Seroprevalence of M. avium subsp. paratuberculosis in Florida beef and dairy cattle. pending publication.
  • Rae DO, Crews JE, Greiner EC, Donovan GA. 2002. Prevalence of and factors associated with Tritrichomonas fetus (Trichomonosis) in Florida bulls. 2003 Florida Beef Report, pp 23-29, Dept. of Animal Sci., Univ. of Florida, Gainesville. Available at: http://www.animal.ufl.edu/extension/beef/pubs.htm.
  • Landaeta-Hernandez AJ, Rae DO, Archbald LF. 2002. In: Avances en ganaderia de doble-proposito. Capitulo VIII,Aspectos geneticos de la debilidad al nacer en becerros Brahman. pp. 119-132.


Progress 10/01/00 to 10/01/01

Outputs
Effect of chlortetracycline in a trace mineral salt mix on fertility traits in beef cattle females in Florida The study objective was to determine the effect of chlortetracycline (CTC) in an ad libitum trace mineral salt mix given to heifers before and (or) during bull exposure on the proportion pregnant and time-to-conception in a fixed breeding period. Heifers (n = 768), 13 to 15 mo of age, were examined (body condition score, vaginal lesion score, BW), and randomly allocated within 2X2 factorial blocks of treatments where trace mineral salt with and without CTC medication was provided in similar but non-adjacent pastures either before and (or)during bull exposure, about 30 d for each. In the 2 d immediately before bull exposure, heifers were examined (BCS, vaginal lesion score, reproductive tract evaluation) and reallocated to treatment pastures. Pregnancy was determined by per rectum palpation at 45 d following bull removal. Mineral intake was below that expected for heifer groups and, as a result, CTC intake was estimated at less than one-third of that targeted. Many heifers were not cycling reproductively at the onset of bull exposure (n = 456, 60.3%). Despite these limitations, heifers receiving CTC treatment before breeding had a pregnancy percentage of 65% (CTC before and during breeding 67% and CTC before breeding 61.8%) compared to those receiving no treatment before breeding (53%, P < 0.03; no CTC before or during breeding 60.4% and CTC during breeding 47.4%). Heifers receiving CTC treatment before breeding were 57% more likely to become pregnant than those not treated before breeding. Prevalence of and factors associated with Tritrichomonas fetus in bull populations in the state of Florida. The objective of these studies were to report the prevalence of infection with Tritrichomonas fetus in bull populations studied in the state of Florida; to assess influence of bull related factors (i.e. age, breed, and grouping); and, to assess effects of trichomonosis on measures of cow performance. In the case review: the mean prevalence for T. fetus infected bulls was 11.9% for all bulls (within herd prevalence 0 to 36% ). A significant difference was detected between mean age of infected bulls and non infected bulls. Cow performance measurements (weaning percentage, mean weaning weight and adjusted mean weaning weight per exposed cow)for cows exposed by breeding to bull groups with the highest prevalence of infection (36%) were significantly different than mean values for the entire study population. In the Florida survey: an overall prevalence for T. fetus infected bulls was 6.0% (within herd prevalence range 0 to 27%). The overall herd prevalence was 30.4%, where 11.1% of herds sampled in North Florida had infected bulls and 39.5% of herds sampled in South Florida had infected bulls. A distinction between herd size was noted, where among medium size herds (100-499 cows) there was a 10.0% herd revalence, while among large size herds (500+ cows) there was a 53.9% herd prevalence. T. fetus infection in natural service beef herds in Florida was associated with bull (age, breed), herd and herd management practices.

Impacts
Effect of Chlortetracycline. There was an improved pregnancy percentage in groups treated with CTC trace mineral prior to breeding. Prevalence of T. fetus. Evaluation of herd and bull population prevalence indicated a significant level of trichomonosis in Florida beef bulls. Large herds of breeding-age females were at significant risk of disease, especially in South Florida.

Publications

  • Landaeta-Hernandez, AJ, Yelich JV, Tran, T, Fields, MJ, Chase, CC, Lemaster JW, Rae DO, Chenoweth, PJ. 2002. Factors affecting the behavioral expression of estrus in beef cows. accepted for publication in Therio.
  • Rae DO, Ramsay KH, Morrison RL. 2002. Effect of chlortetracycline in a trace mineral salt mix on fertility traits in beef females in Florida, accepted for publication in J. Anim. Sci..
  • Rae, DO, Chenoweth, PJ, Genho, PC, McIntosh, AD, Crosby, CE, Moore, SA (a case review) and, Crews JE, Rae, DO, Donovan, GA, Greiner, E (a Florida State survey). 2000. Prevalence of and factors associated with Tritrichomonas fetus in bull populations in the state of Florida (USA). Proceedings CD-Rom, XXI World Buiatrics Congress, 781-794.
  • Rae, DO, Chenoweth, PJ, Genho, PC, McIntosh, AD, Crosby, CE, Moore, SA (a case review) and, Crews JE, Rae, DO, Donovan, GA, Greiner, E (a Florida State survey). 2000. Prevalence of and factors associated with Tritrichomonas fetus in bull populations in the state of Florida (USA). Proceedings, XXI World Buiatrics Congress, 7(Abstract #718).
  • Rae, DO. 2001. Trichomonosis in Florida beef bulls. The Florida Cattleman, May, 44-49.


Progress 10/01/99 to 09/30/00

Outputs
Effect of Chlortetracycline in a Trace Mineral Salt Mix On Fertility in Florida Beef Females. The study objective was to determine the effect of Chlortetracycline (CTC) in an ad libitum trace mineral salt mix given to heifers prior to and/or during bull exposure on the proportion pregnant and time-to-conception in a breeding period. Heifers (N=768)were identified, immunized, examined (body condition score [BCS], vaginal lesion score [VLS], body weight [WT]), and randomly allocated to one of four treatment groups (2 treatment [Tx], 2 non-treatment [NoTx]). Trace mineral salt with/without CTC medication was provided(Tx group 1, 3 and NoTx group 2, 4) for 30-d prior to bull exposure. Immediately prior to bull exposure, heifers were examined and reallocated to treatments (Tx 1,2 and NoTx 3,4)for 30-d of bull exposure. Pregnancy was determined at 45-d following bull removal. Treatment prior to the breeding period was associated with an increased proportion pregnant (Tx=0.646, NoTx=0.525, P<0.001) and reduced mean time to conception (Tx=61.9-d, NoTx 70.1-d, P<0.01), while the later treatment was not significantly different (P>0.10). Other factors associated with proportion pregnant were change in BCS, change in VLS, average daily gain and RTS. ****** Prevalence of Tritrichomonas fetus in bulls in Florida. The objective of these studies were to report the prevalence of Tritrichomonas fetus in bull populations studied in the State; to assess influence of bull related factors (age, breed, and grouping); and, to assess effects of trichomonosis on measures of cow performance. The studies were conducted, as an epidemiologic study and, as a population survey. The sample population of the case study was 1383 bulls and records for cows bred by these bulls in the immediate past breeding season; and, in the Florida survey, 1994 bulls in 54 herds throughout the State. In both, bulls were tested for T. fetus colonization. Prevalence was calculated and correlated to bull, herd, management factors and production measures. Case review: the mean prevalence for T. fetus infected bulls was 11.9% (within herd prevalence 0 to 36%). A significant difference was detected between mean age of infected and non infected bulls. A difference in prevalence among breeds was found, though other factors may have influenced this. Cow performance measures (weaning %, mean weaning wt and adjusted mean weaning wt per exposed cow) for cows exposed to bull groups with the highest prevalence (36%) were significantly different than mean values for other populations. In the Florida survey: prevalence for T. fetus infected bulls was 6.0% (within herd prevalence range 0 to 27%). The herd prevalence was 30.4%, (11.1% North Florida, 39.5% South Florida). A distinction between herd size was noted, where among medium size herds (100-499 cows) there was a 10.0% herd prevalence, and among large herds (500+) there was a 53.9% herd prevalence. T. fetus infection in natural service beef herds in Florida was associated with bull (age, breed), herd and herd management practices.

Impacts
Effect of Chlortetracycline. There was an improved pregnancy percentage in groups treated with CTC trace mineral 30-d prior to breeding, and a possible positive effect from feeding during the second 30-d period. Prevalence of T. fetus. Evaluation of herd and bull population prevalence indicated a significant level of trichomonosis in Florida beef bulls. Herds with 500 or more breeding-age females were at significant risk of disease, especially in South Florida.

Publications

  • Rae DO, Ramsay KH, Morrison RL. Effect of chlortetracycline in a trace mineral salt mix on fertility traits in beef females in Florida, pending publication, 2000.
  • Rae DO, Chenoweth PJ, Genho PC, McIntosh AD, Crosby CE, Moore SA. Prevalence of and factors associated with Tritrichomonas fetus in bull populations in the state of Florida (USA): A case review, and, Crews JE, Rae DO, Donovan GA, Greiner E. Prevalence of and factors associated with Tritrichomonas fetus in bull populations in the state of Florida (USA): A Florida State survey. Proceedings XXI World Buiatics Congress, in publication, 2000.
  • Rae DO, Chenoweth PJ, Genho PC, McIntosh AD, Crosby CE, Moore SA. Prevalence of Tritrichomonas fetus in a bull population and effect on production in a large cow-calf enterprise. JAVMA 214:1051-1055, 1999.
  • Rae DO, Chenoweth PJ, Giangreco MA, Dixon PW, Bennett FL. Assessment of estrus detection by visual observation and electronic detection methods and characterization of factors associated with estrus and preganancy in beef heifers. Theriogenology 51:1121-1132, 1999.