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from Operation-management factors associated with early-postnatal mortality of US foals, Losinger WC, Traub-Dargatz JL, Sampath RK, Morley PS, Preventive Veterinary Medicine, 47 (2000) 157-175, November 2000. Persistent BVD infection in US beef herds In 1996, testing for BVD persistent infection was carried out on 18,931 spring born calves in 128 beef herds. Of these herds, 76 were randomly selected (referred to as “random herds” and 52 were selected based on the herd veterinarian’s suspicion of BVD (suspicious herds). Serum was collected from calves prior to summer turnout (i.e. calves <4 mos. of age), and BVD–PI testing was performed using a microtiter format. Cooperating herds resided in one of 5 states – Alabama, Nebraska, Nevada, North Dakota, or Ohio. Of the 18,931 calves, 56 calves (.3%) from 13 herds (10%) tested positive. Of the random herds, 3% had BVD-PI calves, while 17.9% of the suspicious herds contained PI calves. Therefore, if we know nothing about a herd and are asked to estimate the probability of BVD PI calves in the herd, the best estimate would be 3% (or 1 in 33). Herds with BVD PI calves tended to have multiple calves affected. Prevalence of BVD PI in positive herds ranged from 7% – 50% of calves. All herds were followed until the fall. Of the 56 calves initially positive for BVD, 11 died or were sold as nonperforming calves before weaning, and 2 were lost to follow-up. Of the 43 calves available for follow-up, a blood sample obtained at weaning confirmed BVD PI infection in 33 animals (77%). Blood samples obtained from 45 dams of the 56 calves initially positive for BVD revealed that 6.7% of dams were also PI. Therefore, it appeared that most BVD PI calves were a result of acute BVD infection of the dam during pregnancy. Some think that BVD PI calves rarely survive to weaning. But, if we consider that the 11 nonperforming/dead calves were BVD-PI, and BVD infection was confirmed in 33 calves, then 33/44 (75%) of BVD PI calves alive at turnout survived to weaning. These calves would have functioned as a viral source for cows during the breeding season. Herds that had PI calves had similar vaccination practices, compared to herds that were negative for BVD PI calves. Overall, about 90% of herds used BVD vaccine. There were no clear herd management practices associated with BVD PI herds, compared to negative herds. As discussed in this study, BVD-PI calves may be more common in larger herds. Herds with BVD-PI calves had a 5% reduction in pregnancy percentage the previous fall, compared to negative herds. Otherwise, 1996 calve mortality, 1995 heifer pregnancy rate, and calf weaning weight were similar between herds. Take home points include 1) The observation that BVD-PI calves that survive to turnout can and do survive to weaning 2) Herd vaccination practices were not different between BVD positive and negative herds. This does not indicate that BVD vaccination should not be used, since vaccination may have decreased the clinical effects of BVD. However, it does emphasize that vaccination does not represent the total solution to prevention of BVD in a herd. 3) Prevalence of BVD-PI in calves in affected herds was reasonably high (7-50%). Depending on herd management, these calves could serve as viral sources to naïve cows or heifers during the breeding season. Abstract from Persistent bovine viral diarrhoea virus infection in US beef herds, Wittum TE, et al., Preventive Veterinary Medicine 49 (2001) 83-94 (April 2001).from Persistent bovine viral diarrhoea virus infection in US beef herds, Wittum TE, et al., Preventive Veterinary Medicine 49 (2001) 83-94 (April 2001). Influence of Eqvalan® (Ivermectin) on stallion semen A study was done to evaluate the effect of Eqvalan® on Freiberger stallion semen quality and freezability. Following a 4-week pretrial period, Eqvalan® was administered per os at .2 mg/kg once, and semen was collected and evaluated once weekly for 14 weeks. Parasite loads were considered light, and stallions were 4-22 years old. The authors reported that Eqvalan® did not negatively influence quality or freezability of stallion semen. In fact, Eqvalan® administration appeared to be associated with improved (p<0.0001) sperm concentration in fresh semen and improved motility in frozen semen. Additionally, it appeared that stallions treated with Eqvalan® had improved sperm morphology, compared to control stallions. Abstract from Influence of Eqvalan® (Ivermectin) on quality and freezability of stallion semen, Jannett, F, et al., Theriogenology, 55:785-792, 2001.from Influence of Eqvalan® (Ivermectin) on quality and freezability of stallion semen, Jannett, F, et al., Theriogenology, 55:785-792, 2001. Editor’s Note: This study should be regarded as preliminary. Its limited size and scope preclude definitive conclusions. The authors clearly defined and employed extensive semen evaluation techniques, but the data analysis was not clearly defined and may be considered weak.