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Kansas State University

 

Beef Research News
Brought to you by Kansas State University College of Veterinary Medicine - Farm Animal Section
January 2007

 

 

 

Contents:
BCS and bST influences on reproductive function in cows
Corn production estimates impact feeder prices
Influence of early pregnancy diagnosis on fetal viability
Probability of Male Offspring after Artificial Insemination
Tritrichomonas infections in beef herds
Nasopharyngeal swabs as diagnostic method for respiratory infections





BCS and bST influences on estrous behavior and reproductive function in Brahman-influenced cows


A trial was designed using 99 multiparous Brahman-influenced cows managed to achieve low (BCS = 4.3) or moderate (BCS = 6.1) body condition to determine the influence of bovine somatotropin (bST) on estrous characteristics, reproductive performance, and concentrations of serum GH and plasma NEFA. Cows within each body condition category were randomly assigned to be treated or not with bST at 32 days post partum. Treated cows received bST on days -35, -21, and -7 before initiation of the breeding season. All cows (regardless of treatment) received CIDRs on d -7 with removal and administration of prostaglandin F2 on day 0 (initiation of breeding season). Radiotelemetry was used to monitor estrous behavior during the first 30 days of the breeding season and blood samples were collected from cows at dates of each bST treatment and d -28 and 0. A lower percentage of cows in the low body condition group (64%) were detected in estrus during the first 30 d of the breeding season relative to cows in the moderate BC group (82%, p = 0.05). Relative to non-bST treated cows, more (p < 0.05) cows treated with bST became pregnant during the first 3 d of the breeding season. Low body condition as well as bST reduced intensity of behavioral estrus in postpartum Brahman-influenced cows. However, bST increased first service conception during the first 30 d of breeding and pregnancy rates during the first 3 d of breeding in postpartum Brahman-influenced cows.
Flores, R., Looper, M.L., Rorie, R.W., Lamb, M.A., Reiter, S.T., Hallford, D.M., Kreider, D.L., and Rosenkrans, C.F. (2007) Influence of body condition and bovine somatotropin on estrous behavior, reproductive performance, and concentrations of serum somatotropin and plasma fatty acids in postpartum Brahman-influenced cows. J. Anim Sci. published online first on January 3, 2007, doi: 10.2527/jas.2006-606.




Corn production estimates impact feeder prices
USDA lowered its 2006-07 corn yield estimate by 210 million bu. To 10.535 billion bu., still the third-largest crop in history. Adding to demand was USDA's 50-million-bu. increase in its export estimate, while maintaining its projected 2.15-billion-bu. demand figure for ethanol production. With ending stocks dropping 183 million bu., to 752 million bu., it represents the tightest supply/demand balance since the 1995-96 marketing year, says University of Nebraska economist Darrell Mark.

Writing for the Livestock Marketing Information Center (www.lmic.info/), Mark says volatility in the corn market is playing havoc with cattle feeding breakevens. A 750-lb. feeder steer placed on feed in Nebraska in mid-January would have a breakeven selling price of $90.07/cwt in late June, assuming average feeding performance, using $3.75/bu. for corn and $85/ton for hay, plus other costs at market rates. This puts total cost of gain at $74.37/cwt.

"An increase in the corn price to $4/bu. increases the cost of gain to $76.93/cwt. and the breakeven selling price to $91.10/cwt. Thus, the 25c/bu. corn price increase raises the breakeven selling price for this yearling steer placement by about $1/cwt.," Mark says.

The result will likely be lower calf prices for cow-calf producers, he says. Since Sept. 1, 2006, the prices of 500- to 600-lb. and 700- to 800-lb feeder cattle in Nebraska have decreased $17.47/cwt. and $19.94/cwt, respectively, and Nebraska fed cattle prices have declined $3/cwt. During this same time, Omaha corn prices rallied $1.41/bu.

"Should corn prices continue their surge higher, look for feeder cattle prices to continue their downtrend," Mark says. "Regardless, the uncertainty in the corn market could result in cattle feeders bidding a 'risk premium' into the feeder cattle market (in the form of lower prices) to gain some additional protection or 'cushion', " Mark says.
-- Livestock Marketing Information Center





Influence of early pregnancy diagnosis on fetal viability
A controlled, randomized block-design experiment was conducted to determine the effect of palpation per rectum (for early pregnancy diagnosis) on embryo/fetal viability in dairy cattle. Pregnant dairy cows and heifers (n=523) with a viable embryo detected by transrectal ultrasonography between days 29 and 32 post AI were included. Animals were randomly allocated into two groups: palpation per rectum (PAL) and no palpation per rectum (NPAL). The PAL group were palpated using fetal membrane slip technique once between days 34 and 41 of pregnancy. Transrectal ultrasound was performed on both groups at days 45 and 60 of pregnancy to monitor embryo and fetal viability. Embryo or fetal death was determined by lack of heartbeat or absence of positive signs of pregnancy in an animal previously diagnosed pregnant. The overall rate of embryo/fetal death was 14.0% (73/520). Fetal death (4.5%) was lower than embryonic death (10%, p < 0.001). Overall embryonic/fetal mortality was higher in adult cows (16.4%) than in heifers (8.8%, p<0.025). Twin pregnancies (25%) resulted in higher embryo/fetal death loss than singleton pregnancies (12.9%, p < 0.025). Death loss dis not differ (p>0.05) between animals that were palpated (14.7%, 38/258) and animals not palpated (13.4%, 35/262). In this research, palpation per rectum using fetal membrane slip technique to determine pregnancy status between days 34 and 41 of gestation did not impact overall embryo/fetal viability.

Romano, J.E., Thompson, J.A., Kraemer, D.C., Westhusin, M.E., Forrest, D.W., and Tomaszweski, M.A. Early pregnancy diagnosis by palpation per rectum: Influence on embryo/fetal viability in dairy cattle. Theriogenology 2007; 67(3): 486-493




Probability of Male Offspring after Artificial Insemination
Data from 642,401 calving records from the Irish national database were used in an analysis to determine if natural mating affected secondary sex ratio. Multiple regression generalized estimating equation were used to determine the logit of the probability of a male calf being born. Sire of calf was included as a repeated effect. Month of the year at calving, sex of the previous calf born within dam, breed of service sire, parity of dam and type of mating (i.e. natural or artificial insemination ) significantly (p < 0.05) affected the likelihood of a male calf being born. Male calves were more likely to be born in warmer months, when the sex of the previous calf to the same dam was male, in older cows, and when the service sire was a beef breed. Following adjustment for confounding effects, artificial insemination caused an increased likelihood of male calf (Odds ratio 1.04 to 10.8, p < 0.01) when compared to natural service. This equates to a 1% unit increase in the probability of a male calf being born following artificial insemination.

Berry, D. and Cromie, A. Artificial insemination increases the probability of a male calf in dairy and beef cattle. Theriogenology 2007; 67(2): 346-352.





Tritrichomonas infections in beef herds
Tritrichomonas foetus causes early embryonic death, abortions, and infertility in beef herds. This disease has been diagnosed in Kansas herds in the past year. Definitive diagnosis requires culture and identification of the organism from an animal in the herd. In infected herds, ranchers may not notice any indications of a problem until the time of pregnancy examination when an increased number of open cows are detected. If the breeding season is long (more than 90 days) the astute rancher may notice an increased number of cows cycling at the end of the breeding season. The number of cows that calve can be reduced by 20% to 40% and the mean calving date will be later and the calving season will be spread out longer than in non-infected herds. Proper herd management techniques are necessary to limit losses due to the disease in future years.

For further information on diagnostic techniques and management recommendations, please visit:
http://www.vet.ksu.edu/depts/ClinicalSciences/agpract/articles/Trich_recommendations.pdf





Nasopharyngeal swabs as diagnostic method for respiratory infections
Research was performed to determine the validity of deep nasopharyngeal swabs as a diagnostic method in bovine respiratory disease. Thirty-seven beef calves, approximately four to six months of age, were group housed in France when a natural outbreak of BRD occurred. Animals were selected for study using typical BRD identification measures (temperature, clinical illness scores). Within the group, 20 animals met criteria and were enrolled in the study. Nasopharyngeal samples were collected from each animal using sterile equine uterine culture swabs and then each animal was euthanized and lungs were examined, lavaged and cultured. Overall, M haemolytica was recovered from 90% of lung samples and 85% of nasopharyngeal swab samples, and M bovis was recovered from 90% of lung samples and 70% of nasopharyngeal swab samples. Compared to lung lavage results, in this study, the positive predictive values for nasopharyngeal swabs were 100% for M haemolytica and 100% for M bovis. The negative predictive values for nasopharyngeal swabs were 67% for M haemolytica and 33% for M bovis. The MIC values for tulathromycin of isolates recovered from the lung or nasopharyngeal swab samples from the same calf were equivalent, that is equal or within two-fold dilution for all pathogens. The DNA fingerprints from each paired nasopharyngeal swabs and lung lavage isolates were compared for 10 calves for each pathogen and all samples tested appeared to have the same profile. In this study, deep nasopharyngeal swab was a quick, simple technique that accurately predicted the presence and antimicrobial susceptibility of specific pathogens M haemolytica and M bovis in the lower respiratory tract.

Godinho, KS., Sarasola, P, Renoult, E., Tilt, N., Keane, S., Windsor, G.D., Rowan, T.G., and Sunderland, S.J. Use of deep nasopharyngeal swabs as a predictive diagnostic method for natural respiratory infections in calves. Vet Rec. 2007; 160:22-25.



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Beef Production Medicine
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bwhite@vet.ksu.edu