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Kansas State University

 

Beef Research News
Brought to you by Kansas State University College of Veterinary Medicine - Farm Animal Section
March 2009

 

 

 

Contents:

Effects of dietary zilpaterol hydrochloride on feedlot performance and carcass characteristics

Toxic endophyte-infected fescue influence on sperm characteristics

Effect of number of cows in confinement on estrus behavior

Vaccination of seronegative bulls with MLV BVDV vaccine

On arrival versus delayed vaccination for clostridial and MLV viral vaccines

 



Effects of dietary zilpaterol hydrochloride on feedlot performance and carcass characteristics

A feedlot experiment was conducted under commercial conditions in the Texas Panhandle using 3,757 feedlot steers (average of 94 steers/pen) to evaluate the effects of feeding zilpaterol hydrochloride with or without monensin and tylosin on feedlot performance and carcass characteristics. The experiment was conducted using a randomized complete block design. Treatments were arranged as a 2 (no zilpaterol vs. zilpaterol) x 2 (monensin and tylosin withdrawn vs. monensin and tylosin fed during the final 35 d on feed) factorial. Steers were fed for a total of 161 to 167 d, and treatments were administered during the final 35 d that cattle were on feed. When included in the diet, zilpaterol, monensin, and tylosin were supplemented at 8.3, 33.1, and 12.2 mg/kg (DM basis), respectively. Zilpaterol was included in the diet for 30 d at the end of the finishing period and withdrawn from the diet for the last 5 or 6 d cattle were on feed. Cattle were harvested and carcass data collected. There were no zilpaterol x monensin/tylosin interactions (P >0.12) for ADG or G:F. Feeding zilpaterol increased ADG (P < 0.001) by 0.20 kg and G:F (P < 0.001) by 0.029 kg/kg during the last 35 d on feed. Likewise, when feedlot variables were measured throughout the entire 161- to 167-d feeding trial, ADG (3.4%; P < 0.001) and G:F (3.9%; P < 0.001) were increased. Feeding zilpaterol increased (P < 0.001) dressing percent and HCW and decreased (P < 0.001) total liver abscess rate compared with controls. In addition, zilpaterol increased (P < 0.001) LM area by an average of 8.0 cm2. There was a zilpaterol x monensin/tylosin interaction (P = 0.03) for marbling score. Zilpaterol decreased (P < 0.001) marbling score regardless of monensin and tylosin treatment, although withdrawal of monensin and tylosin for 35 d decreased marbling to a greater extent (31 vs. 17 degrees). Zilpaterol decreased (i.e., improved; P < 0.001) calculated yield grade regardless of monensin and tylosin treatment, but feeding zilpaterol in combination with the withdrawal of monensin and tylosin for 35 d decreased calculated yield grade to a greater extent (0.49 vs. 0.29) compared with the zilpaterol, monensin, and tylosin combination treatment (zilpaterol x monensin/tylosin interaction, P = 0.03). Results suggest that monensin and tylosin can be withdrawn from the diet during the zilpaterol feeding period (final 35 d on feed) with minimal effect on animal performance, although feeding zilpaterol in combination with monensin and tylosin seemed to moderate effects on carcass quality.

J. L. Montgomery, C. R. Krehbiel, J. J. Cranston, D. A. Yates, J. P. Hutcheson, W. T. Nichols, M. N. Streeter, R. S. Swingle and T. H. Montgomery.   Effects of dietary zilpaterol hydrochloride on feedlot performance and carcass characteristics of beef steers fed with and without monensin and tylosin. J. Anim Sci. 2009. 87:1013-1023. doi:10.2527/jas.2008-1169

 

Toxic endophyte-infected fescue influence on sperm characteristics

Sixteen (mean age = 1.1 ± 0.1 yr; mean BW = 478 ± 34 kg) Brahman-influenced bulls were used to determine the influence of fescue type on sperm characteristics and serum concentrations of prolactin, cortisol, and testosterone. Bulls were blocked by BW, scrotal circumference (SC), and pregrazing sperm characteristics and randomly assigned to graze toxic endophyte-infected (EI; 4 bulls/pasture; 2 pastures) or novel endophyte-infected (NE; 4 bulls/pasture; 2 pastures) tall fescue for 121 d. Semen was collected by electroejaculation, and SC was measured and blood samples collected monthly. Sperm were evaluated for motility and morphology with an integrated visual optical system. Overall mean concentration of prolactin was decreased more (P < 0.01) in EI bulls than NE bulls from May to August. Scrotal circumference was not affected by fescue type (P = 0.58); overall SC averaged 36.7 ± 2.3 cm. Percentage of live sperm was not different (P = 0.24) between NE bulls (80%) than EI bulls (67%) in July and August. Bulls grazing NE fescue had more (P < 0.06) motile sperm than EI bulls in July and August. Percentages of progressive (57 vs. 38%, NE and EI, respectively; P < 0.06) and rapid (67 vs. 46%, NE and EI, respectively; P = 0.04) sperm were greater from bulls grazing NE than EI bulls in July and August. Average velocity of the smoothed sperm path and progressive velocity in a straight line from the beginning to the end of the sperm track were slower (P < 0.09) in EI bulls than NE bulls and were slower (P = 0.04) in August compared with July. Mean width of head oscillation as the sperm swims was less (P < 0.06) in August than July. Concentrations of cortisol and testosterone were not (P > 0.10) influenced by fescue type. Semen from bulls grazing EI had reduced motility and morphology than bulls grazing NE. Detrimental effects of toxic fescue may not be mediated by cortisol, testosterone, or both. Semen quality of bulls grazing toxic EI tall fescue was decreased with increased maximum ambient temperatures.

M. L. Looper, R. W. Rorie, C. N. Person, T. D. Lester, D. M. Hallford, G. E. Aiken, C. A. Roberts, G. E. Rottinghaus and C. F. Rosenkrans, Jr. Influence of toxic endophyte-infected fescue on sperm characteristics and endocrine factors of yearling Brahman-influenced bulls  2009. J. Anim Sci. 2009. 87:1184-1191. doi:10.2527/jas.2008-1258

 

Effect of number of cows in confinement on estrus behavior.

Mature Angus and Angus x Hereford cows were used to determine the effects of confinement area and number of cows in estrus on estrous behavior. During each of two replicates, 32 nonpregnant, nonlactating cows were maintained either in a drylot (60 x 100 m) or a pasture (12 ha). Estrous cycles were synchronized with two injections of PGF2 10 to 14 d apart at the initiation of the experiment. Thereafter, PGF2 was administered between d 6 and 18 of the estrous cycle so that 1, 2 to 3, 4 to 6, or  7 cows were estrus at the same time. Concentrations of progesterone were quantified in plasma at treatment to ensure cows had a normal response to PGF2 . Duration of estrus and the number of mounts received during estrus were recorded by HeatWatch. If any part of estrus for a cow occurred at the same time as estrus for another cow, the cow was considered to have concurrent estrus with the other cow. Cows in the drylot had a shorter (P < 0.02; 61.8 ± 3.1 h) interval to estrus after PGF2 compared with cows on pasture (72.8 ± 3.3 h). The interval to estrus was longer (P < 0.07) when cows were treated with PGF2 on d 10 to 13 (76.7 ± 3.3 h) of the estrous cycle than when treated on d 6 to 9 (62.3 ± 4.7 h) or d 14 to 18 (62.9 ± 3.6 h). Increasing the number of cows concurrently in estrus increased the number of mounts each cow received per estrus (P < 0.001) and the duration of estrus (P < 0.01). When only 1 cow was estrus, she received 11.0 ± 6.2 mounts during 11.6 ± 1.5 h. When  7 cows were in estrus at the same time, each cow received 50.4 ± 3.2 mounts during 17.3 ± 0.8 h. Cows in drylot were estrus longer (P < 0.04; 16.4 ± 0.8 h) than cows on pasture (14.2 ± 0.7 h). Duration of the longest interval between mounts received decreased (P < 0.002) as the number of cows in estrus at one time increased (5.3 ± 0.7 h for 1 estrous cow; 2.6 ± 0.3 h when  7 cows were estrus). We conclude that increasing the number of beef cows in estrus at the same time will increase the number of times a cow is mounted and the duration of estrus. The increase in estrous behavior associated with more cows in estrus could increase the number of estrous cows detected with infrequent visual observation.

L. N. Floyd, C. A. Lents, F. J. White and R. P. Wettemann . Effect of number of cows in estrus and confinement area on estrous behavior of beef cows.  Published online first on February 27, 2009 J. Anim Sci. 1910. doi:10.2527/jas.2008-1380

 

Vaccination of seronegative bulls with MLV BVDV vaccine.

The objectives were to vaccinate peri-pubertal bulls with a modified-live vaccine consisting of cytopathic BVDV strains Singer and 296 and evaluate the resulting: (a) transient shed of modified-live, cytopathic BVDV in semen; (b) risk of prolonged testicular infection; and (c) protection against subsequent testicular infection due to viral challenge. Seronegative, peri-pubertal bulls were vaccinated subcutaneously with a standard dose of vaccine (n=11) or were maintained as unvaccinated controls (n=11). Forty-nine days after vaccination, all bulls were intranasally inoculated with a noncytopathic field strain of BVDV. Semen and testicular biopsies collected after vaccination and challenge were assayed for BVDV using virus isolation, reverse transcription-nested PCR, or immunohistochemistry, and the identity of viral strains was determined by nucleotide sequencing of PCR products. Vaccination of peri-pubertal bulls with this vaccine caused a short-term, transient shed of only the type 1a strain of modified-live, cytopathic BVDV in semen for up to 10d after vaccination. The vaccine did not cause prolonged testicular infection. Vaccination with this product prevented development of prolonged testicular infections after subsequent exposure to a field strain of BVDV.

M.D. Givens, K.P. Riddella, Y. Zhanga, P. Galika, P.H. Walza, B.W. Brodersenb, J.W. Johnsona, T. Passlera, P. Widelc, R. Tremblayd. Safety and efficacy of vaccination of seronegative bulls with modified-live, cytopathic bovine viral diarrhea viruses. Theriogenology Volume 71, Issue 6, Pages 975-983 (1 April 2009)

 

On arrival versus delayed vaccination for clostridial and MLV viral vaccines.

Stress, commonly associated with weaning, marketing, and shipment of feeder cattle can compromise immune function, and vaccine administration during immunosuppression may reduce vaccine efficacy and calf growth. Four treatments were compared in a 2 x 2 factorial arrangement to evaluate the effect of on-arrival (d 0) vs. delayed (d 14) administration of clostridial (CLOS) and respiratory (RESP) vaccines on health, performance, bovine viral diarrhea virus (BVDV) antibody titers, and physiological immune measurements of high-risk, newly received calves. Crossbred bull and steer calves (n = 263) were weighed (239 ± 1.2 kg), stratified by gender, and randomly assigned to vaccination treatment: 1) arrival CLOS, arrival RESP (ACAR); 2) arrival CLOS, delayed RESP (ACDR); 3) delayed CLOS, arrival RESP (DCAR); and 4) delayed CLOS, delayed RESP (DCDR). Body weight and blood samples were collected on d 0, 14, 28, 42, and 56. Average daily gain did not differ (P  0.34) averaging 0.98, 0.93, 0.95, and 0.91 kg/d for ACAR, ACDR, DCAR and DCDR, respectively, for the entire 56 d trial. Vaccination timing did not affect morbidity (P  0.23); however, there tended to be a CLOS timing effect (P = 0.07) and RESP timing effect (P = 0.09) on days to initial bovine respiratory disease (BRD) treatment. Average days to initial BRD treatment were less for ACAR (6 ± 0.8 d) compared to DCDR (8 ± 0.8 d; P = 0.01). Greater white blood cell (WBC) counts were observed for DCDR than ACDR (P = 0.01), with ACAR and DCAR being intermediate. Serum cortisol concentrations were greater on d 0 than d 14 (P < 0.01) or d 28 (P = 0.01) but no treatment x day interaction (P = 0.21) was observed. Timing of RESP administration affected (P = 0.001) serum BVDV type I titer levels, with greater (P < 0.01) levels in calves receiving RESP vaccine on arrival. Delaying CLOS or RESP vaccination did not affect gain or morbidity in high risk, newly received stocker calves. Calves administered RESP vaccine on d 0 developed antibody titers to BVDV type I earlier than delayed RESP treatments. Total WBC count was greatest when RESP and CLOS vaccination were delayed (DCDR).

J. T. Richeson, E. B. Kegley, M. S. Gadberry, P. A. Beck, J. G. Powell and C. A. Jones. Effects of on-arrival versus delayed clostridial or modified live respiratory vaccinations on health, performance, bovine viral diarrhea virus type I titers, and stress and immune measures of newly received beef calves. Published online first on March 13, 2009 J. Anim Sci. 1910. doi:10.2527/jas.2008-1484


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Brad White
Beef Production Medicine
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bwhite@vet.k-state.edu