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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 2007

 

 

 

Contents:

Antibiotic feeding & auction exposure effect on calves

Neosporosis in Bulls

Dam nutrition & reproductive performance of heifers

Bull exposure and conception rates

Flunixin meglumine and pregnancy establishment

 

Antibiotic feeding & auction exposure effect on calves

Research was performed to evaluate potential differences in response to different antibiotic therapies in populations of ranch-direct and auction sourced calves. The trial consisted of using 240 mixed breed steers (265.5 4.8 kg) divided into two equal groups: shipped directly from ranch to feedlot or shipped to an auction and subsequently to same feedlot. All calves were from single ranch located 400 km from feedlot. Calves in the auction group were held overnight at the auction without feed or water, co-mingled, sorted, run through the auction ring and transported to the feedlot. Calves were weighed on arrival and equipped with a radio frequency identification tag to monitor bunk attendance. Calves sourced directly from the ranch were heavier at arrival (273 vs. 258; P=0.01) than calves processed through the auction barn. For calves fed 6 g/head/d chlortetracycline from days 5 to 9, feeding an additional 350 mg head/d of chlortetracycline and sulfamethazine from days 1 to 28 improved gain/feed (P = 0.03), but only for the first 28 d of the 84-d trial. Frequency of bunk visits were altered by calf source and antibiotic treatment. In summary, for cattle receiving 6 g/head/d of chlortetracycline from days 5 to 9, feeding an additional 350 mg/head/d of chlortetracycline and sulfamethazine improved gain/feed, but this effect did not maintain past the period in which it was fed. Any performance effects of processing calves through an auction barn were small and disappeared after the first month in the feedlot. Differences in feeding behavior through the whole trial were small.

Gibb, D., K. Schwartzkopf-Genswein, T. McAllister, B. Genswein, M. Streeter Effect of Sub-therapeutic Antibiotics and Auction Exposure on Health, Performance, and Feeding Behavior of Weaning Calves Can J Anim Sci 2006 86(4) 457-460.



Neosporosis in Bulls

Eight seronegative bulls were intravenously infected with live Neospora caninum tachyzoites of NC-1 isolate to investigate the presence of N. caninum in semen and blood. The presence of N. caninum in semen and blood was assessed using a nested-PCR procedure. All eight experimentally infected bulls showed N. caninum DNA in their semen and/or blood samples at some time during the course of the study. A significant increase in mean serum specific IgM antibody response to N. caninum was detected between 10 and 28 days post-infection. Specific anti-N. caninum IgG were detected in seminal plasma from infected bulls and values obtained were different from seronegative controls after 25 days post-infection. The observations indicate an intermittent presence of N. caninum in low numbers in semen and associated with chronic stage of infection.

E. Serrano-Martnez, I. Ferre, A. Martnez, K. Osoro, A. Mateos-Sanz, I. del-Pozo, G. Aduriz, C. Tamargo, C.O. Hidalgo, L.M. Ortega-Mora Experimental neosporosis in bulls: Parasite detection in semen and blood and specific antibody and interferon-gamma responses Therio 2007 67(6): 1175-1184



Dam nutrition & reproductive performance of heifers

Research was performed over 3 years to evaluate the effects of late gestation (LG) or early lactation (EL) dam nutrition on subsequent heifer growth and reproduction. In LG, cows received 0.45 kg/d of 42% CP supplement (PS) or no supplement (NS) while grazing in dormant Sandhills range. During EL, cows from each LG treatment were feed cool-season grass hay or grazed sub-irrigated meadow. Performance of subsequent heifers (n=170) was evaluated. Heifer birth date and birth weight were not affected by dam nutrition. Heifers from PS dams had greater weight (P < 0.04) at prebreeding and pregnancy diagnosis, but these weights were unaffected by EL nutrition. There was no effect (P>0.10) of LG or EL dam nutrition on age at puberty or percentage of heifers cycling before breeding. Pregnancy rates were greater (P=0.05) for heifers from PS dams, and a greater proportion (P = 0.005) of heifers from PS dams calved in the first 21 d of the heifers’ first calving season. Nutrition of dams did not influence (P < 0.10) heifers’ average calving date, calving difficulty, and calf birth weight during the initial calving season. Heifers from PS dams had greater weight at the beginning of the second breeding season (P = 0.005). Heifers born to PS cows were heavier at weaning, prebreeding, first pregnancy diagnosis, and before their second breeding season. Heifers from cows that grazed meadows during EL were heavier at weaning but not post weaning. Despite similar ages at puberty and similar proportions of heifers cycling before the breeding season, a greater proportion of heifers from PS dams calved in the first 21 d of the heifers’ first calving season, and pregnancy rates were greater compared with heifers from NS dams. Collectively, these results provide evidence of a fetal programming effect on heifer post weaning BW and fertility.

J. L. Martin, K. A. Vonnahme, D. C. Adams, G. P. Lardy, and R. N. Funston Effects of dam nutrition on growth and reproductive performance of heifer calves
J. Anim Sci. 2007; 85:841-847.



Bull exposure and conception rates

Three experiments were performed to evaluate the impact of exposing primiparous, suckled beef cows to the biostimulatory effect of bulls on breeding performance in an estrus synchronization protocol that included GnRH followed 7 d later by PGF 2 and fixed time AI (TAI). Experiment 1 evaluated the effects of bull exposure at different days after calving, experiment 2 evaluated the biostimulatory effects of bull excretory products and in year three the biostimulatory effects of familiar and unfamiliar bulls on resumption of ovarian cycling activity was examined. In all studies, cows were exposed (biostimulated; n = 94) or not exposed (nonbiostimulated; n = 67) to bulls or excretory products of bulls for at least 60 d before the beginning of the estrus synchronization protocol. The percentages of cows that exhibited estrus after PGF2 and before TAI, the interval from PGF2 to estrus, and the percentages of cows inseminated 12 h after estrus or at TAI did not differ between biostimulated and nonbiostimulated cows. Conception rates for cows bred by AI 12 h after estrus did not differ between biostimulated and nonbiostimulated cows; however, the TAI conception rate was greater (P < 0.05) for biostimulated cows (57.6%) than for nonbiostimulated cows (35.6%). We conclude that TAI conception rates in an estrus synchronization protocol that includes GnRH followed 7 d later by PGF2 may be improved by the biostimulatory effect of bulls in postpartum, primiparous cows.

Berardinelli, J.G. P. S. Joshi, and S. A. Tauck. Conception rates to artificial insemination in primiparous, suckled cows exposed to the biostimulatory effect of bulls before and during a gonadotropin-releasing hormone-based estrus synchronization protocol J. Anim Sci. 2007; 85:848-852.


Flunixin meglumine and pregnancy establishment

Research was performed to determine the effects of flunixin meglumine (FM) administration on early embryonic mortality and circulating prostaglandin and cortisol concentration in transported and non-transported cows. The effects of transportation and FM at 14 d post AI was evaluated in 483 cows. Treatments were transport (n = 129), transport + FM (n = 128), no transport (n =130) and no transport + FM (n = 96). Flunixin meglumine (1.1 mg/kg BW; i.m.) was administered before separation and transportation groups were placed on semi-tractor trailers without calves fro 4 to 6 h. Blood samples were collected before and after treatment. Cows receiving transportation and FM tended (P = 0.07) to have greater AI pregnancy rates (74%) than those that did not received FM (66%) irrespective of transportation. Transportation increased cortisol concentration (P< 0.05) relative to non-transported cows. Pregnancy rates were increased (P < 0.05) in FM cows compared to non-FM cows (71 and 61% respectively). The authors concluded that transportation of cows approximately 14 d after AI increased serum cortisol concentrations but did not affect AI pregnancy rates. However, treatment of cows with FM increased AI pregnancy rates, irrespective of whether they were transported.

Merrill, M.L. R.P. Ansotegui, P.D. Burns, M.D. MacNeil, T.W. Geary. Effects of flunixin meglumine and transportation on pregnancy establishment in beef cows. J. Anim Sci. 2007; published online 3/19/07, doi: 10.2527.

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Beef Production Medicine
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bwhite@vet.ksu.edu