No abstract

Totals of 960 and 286 certified potato seed lots from locations across North America were planted in trials in Washington and Oregon, respectively, in 2001 to 2003 and tested for strains of Potato virus Y (PVY). The incidence of PVYO-infected lots averaged 16.4 and 25.9% in the Washington and Oregon trials, respectively. There was a general trend of increasing incidence of the PVYO, PVYN:O, and PVYN strains during this period, as evidenced by more infected cultivars, sites of seed origin, and number of seed growers providing infected seed lots. In particular, there was a dramatic increase in seed lots with the PVYN:O strain from 2002 to 2003. PVYN:O, in contrast to PVYO, which only causes yield reduction, also causes internal and external damage to tubers, making them unmarketable. In 2003, PVYN:O occurred in seed lots originating in eight states and three Canadian provinces. The increased incidence of PVYN:O was likely due to the difficulty in differentiating this strain from PVYO. The prevalence of PVY in potato seed lots documented herein poses a threat to potato production in the United States and suggests that current measures to reduce the incidence of this virus are inadequate.

Sixty crossbred cull cows were used to determine the combined effects of a trenbolone acetate-estradiol implant and feeding zilpaterol hydrochloride on performance, carcass characteristics, and subprimal yields of mature cows fed for 70 d. Cows were assigned to 1 of 5 treatments: 1) grazing native grass pasture (G); 2) concentrate-fed (C) a grain sorghum-sorghum silage diet; 3) concentrate-fed and implanted (CI) with Revalor-200 (trenbolone acetate-estradiol); 4) concentrate-fed and fed Zilmax (zilpaterol hydrochloride) beginning on d 38 of the feeding period (CZ); and 5) concentrate-fed, implanted, and fed Zilmax beginning on d 38 (CIZ). The concentrate diet consisted primarily of ground grain sorghum and sorghum silage. During the last 34 d of the feeding trial, concentrate-fed (C, CI, CZ, and CIZ) cows had greater (P < 0.05) gains than G cows. Hot carcass weights and dressing percentages were greater (P < 0.05) for the concentrate-fed cows than for G cows. Longissimus muscle area was largest (P < 0.05) for CIZ cows, whereas subprimal weights from the chuck were heavier (P < 0.05) from CIZ cows than C and G cows, and carcasses from CI and CZ cows had heavier (P < 0.05) chuck subprimal weights than G cows. Rib and round subprimal weights were heavier (P < 0.05) for concentrate-fed cows compared with G cows. In addition, carcasses from CIZ cows had heavier (P < 0.05) total subprimal weights, and total subprimals were a greater percentage of their initial BW than C cows. Rib cut-out and total soft tissue weights from the 9-10-11th rib were less (P < 0.05) for G cows than concentrate-fed cows. Feeding cull cows a concentrate diet increased carcass weight, dressing percentage, and subprimal yields compared with feeding cows a grass-based pasture diet, and the combination of a trenbolone acetate-estradiol implant and feeding zilpaterol hydrochloride can maximize trimmed beef yields from cull cows fed a high-concentrate diet.

The objective of this experiment was to determine if 2 doses of prostaglandin F(2α) (PGF) administered concurrently at controlled intravaginal drug release (CIDR) removal was an efficacious method for delivery of PGF in the 5-d CO-Synch + CIDR protocol. Postpartum beef cows (n = 2,465) from 13 herds in 8 states were enrolled in the 5-d CO-Synch + CIDR protocol and assigned to receive 2 doses of PGF (25 mg/dose) 8 h apart with the initial injection given at CIDR insert removal (8h-PGF), 2 doses (25 mg/dose) of PGF delivered in 2 injection sites, both administered at CIDR insert removal (Co-PGF), or a single 25-mg dose of PGF at CIDR insert removal (1x-PGF). Cows were fixed timed-artificially inseminated (FTAI) 72 h after CIDR removal concurrent with GnRH administration. Estrus-cycling status (54% cyclic) was determined by evaluation of progesterone in 2 blood samples collected before CIDR insertion. Determination of pregnancy was performed by transrectal ultrasonography 39 ± 0.1 d after FTAI and at least 35 d after the conclusion of the breeding season. Fixed timed-AI pregnancy rates were greater (P < 0.05) for the 8h-PGF (55%) than the 1x-PGF (48%) treatment, with the Co-PGF (51%) treatment intermediate and not different (P > 0.10) from the other treatments. Contrast analysis demonstrated that cows receiving 50 mg of PGF (8h-PGF and Co-PGF) had greater (P < 0.05) FTAI pregnancy rates than those receiving 25 mg (1x-PGF). Pregnancy rates to FTAI were greater (P < 0.05) in cyclic (55%) than noncyclic (47%) and greater (P < 0.05) in multiparous (≥3 yr of age; 54%; n = 1,940) than primiparous cows (40%; n = 525). Luteolysis after PGF treatment was assessed in a subset of cows (n = 277) and treatment tended (P = 0.09) to affect the proportion of cows having luteolysis. The percentage of cows that had luteolysis was least in the 1x-PGF treatment (89%) and greatest in the 8h-PGF treatment (97%), with the Co-PGF treatment (94%) being intermediate. Breeding season pregnancy rate (88%) did not differ (P > 0.10) among treatments but was greater (P < 0.01) in multiparous (90%) than primiparous (78%) cows. In summary, 50 mg of PGF was required in the 5-d CO-Synch + CIDR protocol to maximize pregnancy rates; however, pregnancy rate did not differ when 50 mg of PGF was administered simultaneously with CIDR removal or split with 25 mg administered at 0 and 8 h after CIDR removal.

The effectiveness of two estrus-detection methods (visual observation and radiotelemetric, pressure-sensitive, rump-mounted devices) was compared in peripubertal, crossbred yearling beef heifers. Heifers (n = 50) were fitted with a pressure-sensitive device affixed to their rumps to which a battery-operated radio transmitter was connected. Activation of the sensor sent a radiotelemetric signal to a microcomputer via a fixed radio antenna. Heifer identification, date, time, and duration of standing events were recorded. Estrus was synchronized by feeding melengestrol acetate (MGA) for 14 d and then injecting PGF2 alpha 17 d after the last daily dose of MGA. Following the injection of PGF2 alpha, heifers were observed visually for signs of estrus at 0730 and 1630 (45 min each). Estrus was detected in 41 of 49 heifers (one lost the device) by visual observation and(or) the radiotelemetric device. Number of standing events during estrus, determined by the radiotelemetric device, averaged 50.1 +/- 6.4 per heifer, with the duration of estrus ranging from 2.6 to 26.2 h (average = 14 +/- .8 h). Visual observation failed to detect 11 of 41 heifers (37%) that were detected by the radiotelemetric device. Heifers with fewer standing events (19.3 vs 60.5; P < .001) and estrus of shorter duration (8.4 vs 15.6 h; P < .001) were those not identified by visual observation. Based on intervals between the first detected standing event of estrus and time of insemination, a wide window of fertility seems to exist in some heifers. Radiotelemetric devices were useful in identifying a greater (P < .05) proportion (100%) of heifers in estrus (increased efficiency) compared with visual observation (73%). However, accuracy of both methods was similar.

Three experiments were conducted to evaluate influences of supplemental alfalfa quality on intake and use of low-quality meadow grass roughages (MG) by beef cattle. In Exp. 1, 15 steers (250 kg) were assigned to three treatments: 1) MG (5.2% CP), no supplement; 2) MG plus high-quality alfalfa (18.8% CP); and 3) MG plus low-quality alfalfa (15.2% CP). High- and low-quality alfalfa supplements were fed at .45 and .55% BW, respectively. Total DMI was greater (P < .01) for alfalfa-supplemented steers than for MG. Likewise, intake of digestible DM, DM digestibility (DMD), and ruminal ammonia level were greater (P < .01) for supplemented steers. In Exp. 2, 96 pregnant Hereford x Simmental cows (537 kg; body condition [BC] score 4.86) were assigned to the same treatments as in Exp. 1. For d 0 to 42, cows grazed on 19.1 ha of stockpiled MG (4,539 kg/ha; 6.8% CP), whereas, on d 43 to 84, cows received MG hay (5.2% CP). Supplemented cows gained more BW (P < .01), BC score (P < .01), and had heavier calf birth weight (P < .01) than nonsupplemented cows. However, there were no treatment effects (P > .10) on cow cyclicity, pregnancy rate, or calving interval. In Exp. 3, 90 pregnant Angus x Hereford cows (475 kg; BC score 4.59) were assigned to three treatments: 16.1%, 17.8% or 20.0% CP alfalfa supplement, with levels of .63, .55, and .50% of BW, respectively. Weight gain and BC score for the 84-d study displayed a quadratic response (P < .10), yet represented only 7 kg BW and .2 units of BC score. In conclusion, alfalfa hay supplementation was effective in increasing DMI and digestibility. However, alfalfa hay quality did not dramatically affect BW, BC score, and(or) calf birth weight, when fed on an isonitrogenous basis.

The effects of mineral-supplement delivery system on patterns of supplement use by grazing beef cows were measured in 2 studies. Study 1 was conducted on 4 pastures grazed by pregnant, mature beef cows (BW = 562 ± 38 kg) from February to May. Study 2 was conducted on 4 pastures grazed by lactating beef cows (BW = 579 ± 54 kg) and their calves from May to September. Treatments were mineral delivered in salt-based, granular form (salty) or mineral provided in a low-protein, cooked, molasses-based block (sweet); both were fed ad libitum. The salty supplement was supplied to cattle via a covered mineral feeder; the sweet supplement was supplied via an open-topped barrel. Both salty and sweet supplements were deployed in each pasture. No additional salt was supplied to cattle. Forage use in the vicinity of each supplement-deployment site and the frequency and duration of herd visits to each supplement-deployment site were measured during four 14-d periods during study 1 and seven 14-d periods during study 2. Supplements were moved to new locations within pastures at the beginning of each period. Consumption of the sweet supplement was greater than salty during each data-collection period in study 1; however, relative differences in consumption diminished over time (treatment × time, P = 0.03). In study 2, sweet consumption was greater than salty in periods 1, 6, and 7 but was not different from salty during periods 2, 3, 4, and 5 (treatment × time, P < 0.01). Increased consumption of the sweet supplement in study 1 translated to greater frequency of herd visits to supplement-deployment sites compared with the salty sites (2.82 vs. 2.47 herd visits/d; P = 0.02) and longer herd visits to supplement-deployment sites compared with the salty sites (125.7 vs. 54.9 min/herd visit; P < 0.01). The frequency of herd visits to mineral feeding sites in study 2 was similar (P > 0.10) between treatments for periods 1 through 6; however, herds visited the sweet sites more often than salty during period 7 (P < 0.01). Herd visits to the sweet sites were longer than those to the salty sites in study 2 (83.8 vs. 51.4 min/herd visit; P < 0.01). Forage disappearance within 100 m of supplement-deployment sites was not influenced (P ≥ 0.54) by treatment in either study. Results were interpreted to suggest that the sweet supplement influenced the location of grazing cattle more strongly than the salty supplement and may be more effective for luring cattle into specific areas of pasture during the winter, spring, and early fall but not during summer.

A study was designed to evaluate estrus response and fertility after treatment with melengestrol acetate (MGA) and prostaglandin F2 alpha (PGF2 alpha) in yearling beef heifers. Three hundred four heifers at three locations were allotted to one of two treatments: Treatment 1 served as a nonsynchronized control (CON); and heifers in Treatment 2 received .5 mg of MGA.animal-1.d-1 for 14 d and 25 mg of prostaglandin F2 alpha (PGF2 alpha) 17 d after MGA (MGA-PGF). Heifers in CON and MGA-PGF groups were artificially inseminated 12 h after observed estrus for 21 and 6 d after PGF2 alpha, respectively. Blood samples were collected from each heifer 10 d before and on the day MGA feeding began and 10 d before and on the day PGF2 alpha was administered. Heifers with concentrations of serum progesterone greater than 1 ng/mL on either date before administration of MGA or PGF2 alpha were considered pubertal. More (P = .02) prepubertal heifers that received MGA attained puberty by initiation of breeding than did CON heifers (72 vs 45%, respectively). The proportion of heifers that displayed estrus within 6 d after PGF2 alpha was greater (P less than .001) for MGA-PGF than for CON heifers (77 vs 25%, respectively) but was also influenced by location (P = .03). Conception rate at first service for MGA-PGF heifers that attained puberty during MGA feeding and before PGF2 alpha was not different (P = .50) from that of CON that attained puberty during the same period.(ABSTRACT TRUNCATED AT 250 WORDS)