RESUMEN
Clinical signs of photosensitivity in cattle can occur sporadically and unpredictably. It is believed that cases of photosensitivity may be underreported, causing inaccurate and inflated reports of mortality. Additionally, because secondary photosensitization in grazing cattle occurs with liver damage or dysfunction, photosensitivity can have many potential or associated causes. This case links a previous occurrence of coccidiosis to an outbreak of photosensitivity in grazing Holstein steers. Grazing management staff first observed clinical signs of photosensitivity 17 days after an outbreak of coccidiosis and subsequent turnout to spring pastures. Clinical signs were observed in 25% of the population. The severity of photosensitivity was variable and ranged from blistered skin on the muzzle to sloughing of unpigmented epidermis and thinly haired regions. Severely affected cattle were removed from pasture, housed under shade, monitored for infection, and recovered without treatment. Mild cases remained on pasture and recovered without treatment. Photosensitivity did not reoccur in the cattle that remained on pasture or in mildly affected cattle returned to pasture. Photosensitivity did not appear to be associated with pasture weeds, a specific forage species, or variable or extreme weather conditions that could have resulted in mycotoxin production. The occurrence appears to have been a result of a previous and concurrent coccidiosis outbreak that caused secondary photosensitization through hepatic lipidosis caused by anorexia and dehydration associated with the severe coccidiosis. Although clinical signs appeared suddenly, cattle recovered quickly and without treatment.
RESUMEN
Symptoms of clover rot caused by Sclerotinia trifoliorum or S. sclerotiorum are identical, making differentiation and identification of the causal species difficult and time consuming. Polymerase chain reaction (PCR) amplification and nucleotide sequencing were used to examine 40 isolates of S. trifoliorum (29 from Poland, 11 from the United States) and 55 isolates of S. sclerotiorum (26 from Poland, 29 from the United States). We determined that amplification of the ß-tubulin and calmodulin genes with TU1/TU2/TU3 and SscadF1/SscadR1 PCR primers and the presence of introns and single-nucleotide polymorphisms (SNP) within the ribosomal DNA (rDNA) as detected with NS1/NS8 and internal transcribed spacer (ITS)1/ITS4 PCR primers are effective for rapidly and accurately differentiating between the two species of Sclerotinia. In addition, our research revealed a lack of intraspecies variation within S. sclerotiorum isolates from the United States and Poland using these same molecular markers. We detected a relatively high degree of intraspecies variability among isolates of S. trifoliorum from the United States and Poland using the presence of introns and SNP within the rDNA. SNP and nuclear small-subunit rDNA analyses revealed distinct groups of S. trifoliorum among the isolates used in this study. The results of this study provide useful information for clover breeders and pathologists looking to develop clover varieties with durable resistance.
RESUMEN
Runoff from sloping landscapes cropped with established alfalfa (Medicago sativa L.) may contain bioavailable P (BAP) which accelerates eutrophication of surface water bodies. Such BAP exists as either dissolved reactive P (DRP) or bioavailable reactive particulate P (BPP). We hypothesized that before and after harvest, sod-forming smooth bromegrass (Bromus inermis Leyss.) or alfalfa-smooth bromegrass mixtures would have less BAP, DRP, and BPP runoff losses than taprooted alfalfa. Swards established in 1992 near Lancaster, WI were subjected to a 72 mm simulated rainfall applied for 1 h in 1993 and 1994 to forage regrowth at 4 and 6 wk after first harvest and immediately (0 wk) after second harvest. Hourly BAP losses for all sward types were 82% less when 1.5 Mg ha(-1) of forage dry matter was present. High DRP losses (>0.050 kg ha(-1)) were associated with high DRP concentrations (>7.1 micromol L(-1)) and high surface soil P concentrations (>59 mg kg(-1)) resulting from broadcast maintenance P fertilizer. High BPP losses (>0.035 kg ha(-1)) were associated with high runoff volumes (>24 mm) and sediment concentrations (>2 g L(-1)). Summed over all 6 rainfall simulations, total BAP loss was only 0.07 kg ha(-1) at the 6 wk stage of regrowth compared with 0.35 at 4 wk, and 0.41 at 0 wk. Moreover, there was no significant difference between sward types for DRP concentration, DRP loss, or BAP loss. We conclude that avoiding excessive defoliation was more effective at reducing BAP losses than specific forage species selection.