Prevalence of Cryptosporidium sp in equids in Louisiana

In 1985, 22 pony foals reared in a helminth-free environment were tested daily for oocysts of Cryptosporidium sp by use of fecal flotation. Oocysts were found in all foals. Oocysts were first observed in feces collected from foals 9 to 28 days after birth. The mean period of oocyst shedding was 10 days and ranged from 2 to 18 days in individual foals. Diarrhea was observed in 14 of 22 (64%) foals and began before the period of oocyst shedding. Fecal samples also were examined for other infective agents. Salmonella poona was isolated from 1 foal that did not have diarrhea, and coronavirus particles were observed in the feces of 2 foals with diarrhea. Cryptosporidium sp oocysts also were observed in feces of 2 of 17 Thoroughbred foals, 3 of 14 Quarter Horse foals, and 3 of 26 pony foals reared on pastures with their dams. Samples from pasture-reared foals were collected at irregular intervals. Of the 11 Cryptosporidium-positive fecal samples collected from pastured foals, 2 were from foals with diarrhea. A similar survey was conducted during the 1986 foaling season, using the same procedures. Examination of 300 samples from 58 Quarter Horse, Arabian, and pony foals did not detect oocysts. Daily examination of feces from 10 pony foals reared under helminth-free conditions for 30 days also failed to detect Cryptosporidium oocysts.     

An economically based evaluation index for perennial and short‐term ryegrasses in New Zealand dairy farm systems

Grazed pastures based on ryegrass species provide most of the feed for dairy cattle in New Zealand. There are many cultivars of perennial (Lolium perenne), annual and Italian (L. multiflorum), and hybrid (L. boucheanum) ryegrasses available for dairy farmers to use in pasture renewal. This study describes an index which ranks ryegrass cultivars relative to a genetic base according to the estimated economic value (EV) of seasonal dry matter (DM) traits. A farm system model was used to derive EVs (Grazed pastures based on ryegrass species provide most of the feed for dairy cattle in New Zealand. There are many cultivars of perennial (Lolium perenne), annual and Italian (L. multiflorum), and hybrid (L. boucheanum) ryegrasses available for dairy farmers to use in pasture renewal. This study describes an index which ranks ryegrass cultivars relative to a genetic base according to the estimated economic value (EV) of seasonal dry matter (DM) traits. A farm system model was used to derive EVs ($ ha^?1 calculated as change in operating profit divided by unit change of the trait) for additional DM produced in different seasons of the year in four regions. The EV of early spring DM was consistently high across all regions, whereas EV for late spring DM was moderate to low. Genotype × environment analysis revealed significant reranking of DM yield among ryegrass cultivars across regions. Hence, separate performance values (PVs) were calculated for two mega‐environments and then combined with the corresponding season and region EV to calculate the overall EV for twenty‐three perennial ryegrass and fifteen short‐term ryegrass cultivars. The difference in operating profit between the highest ranked and lowest ranked perennial ryegrass cultivar ranged from $556 ha^?1 to $863 ha^?1 year^?1 depending on region. For short‐term ryegrasses used for winter feed, the corresponding range was $394 to $478 ha^?1 year^?1. Using PV for DM yield, it was estimated that plant improvement in perennial ryegrass has added $12–$18 ha^?1 year^?1 (depending on region) operating profit on dairy farms since the mid‐1960s.     

Use of standard toxicity tests with Typhlodromus pyri and Aphidius rhopalosiphi to establish a dose-response relationship

The existing standardised test systems for assessing the toxicity of crop protection products to the non-target arthropods Typhlodromus pyri (Acari: Phytoseiidae) and Aphidius rhopalosiphi (Hymenoptera: Aphidiidae) are limit tests designed to compare a single-use rate of the product with a water control. The suitability of these test systems for generating dose-response data as required for refined ecotoxicological risk assessment was evaluated. Data on dose-response toxicity of crop protection products to T. pyri and A. rhopalosiphi were generated under worst-case laboratory and to T. pyri under extended laboratory conditions and analysed using the standard Probit method, a logistic regression, a generalised Probit analysis, and the moving average-angle method in order to calculate the LR₅₀-values (application rate killing 50% of the exposed organisms). The fit of the models, the precision of the resulting LR₅₀ values, and the required minimum number of replicates were compared. In 85% of the studies, at least one of the statistical methods led to satisfactory results. The moving average-angle method was the most widely applicable method. The results show that the existing guidelines can be used to perform dose-response tests. Implications for risk assessment are discussed.