Integration of soil, crop and weed management in low-external-input farming systems

Greater adoption and refinement of low-external-input (LEI) farming systems have been proposed as ways to ameliorate economic, environmental and health problems associated with conventional farming systems. Organic soil amendments and crop diversification are basic components of LEI systems. Weed scientists can improve the use of these practices for weed management by improving knowledge of four relevant ecological mechanisms. First, multispecies crop rotations, intercrops and cover crops may reduce opportunities for weed growth and regeneration through resource competition and niche disruption. Secondly, weed species appear to be more susceptible to phytotoxic effects of crop residues and other organic soil amendments than crop species, possibly because of differences in seed mass. Thirdly, delayed patterns of N availability in LEI systems may favour large-seeded crops over small-seeded weeds. Finally, additions of organic materials can change the incidence and severity of soil-borne diseases affecting weeds and crops. Our research on LEI sweetcorn and potato production systems in central and northern Maine (USA) suggests that these mechanisms can reduce weed density and growth while maintaining crop yields. Low-external-input farming systems will advance most quickly through the application of interdisciplinary research focused on these and other ecological mechanisms.     

不同非洲猪瘟病毒株j5R基因及其编码蛋白的比较

根据非洲猪瘟病毒ＭａｌａｗｉＬＩＬ２０／１株ｊ５Ｒ阅读框Ｃ端抗原决定簇序列制备的合成肽能被不同毒株感染康复猪的免疫血清识别。多聚酶链反应研究表明,９个不同毒株的ｊ５Ｒ基因长度略有差异;蛋白转印杂交试验证明,这种基因长度的差异导致相应蛋白多肽的长度多样性。这些结果进一步证明,长度多样性是非洲猪瘟病毒基因及其编码蛋白较为普遍的特点。     

Associations of polymorphisms in the Pit-1 gene with growth and carcass traits in Angus beef cattle

The Pit-1 gene was studied as a candidate for genetic markers of growth and carcass traits. Angus beef cattle that were divergently selected for high- or low-blood serum IGF-I concentration were used in this study. The single-strand conformation polymorphism method was used to identify polymorphism in the Pit-1 gene including regions from intron 2 to exon 6. Two polymorphisms, Pit1I3H (HinfI) and Pit1I3NL (NlaIII), were detected in intron 3 of the Pit-1 gene. One polymorphism, Pit1I4N (BstNI), was found in intron 4, and a single nucleotide polymorphism, Pit1I5, was found in intron 5. The previously reported polymorphism in exon 6, Pit1E6H (HinfI), was also studied in 416 Angus beef cattle. Associations of the polymorphisms with growth traits, carcass traits, and IGF-I concentration were analyzed using a general linear model procedure. No significant associations were observed between these polymorphisms and growth and carcass traits.     

Environmental factors influencing heat stress in feedlot cattle

Data from 3 summer feedlot studies were utilized to determine the environmental factors that influence heat stress in cattle and also to determine wind speed (WSPD; m.s(-1)) and solar radiation (RAD; W.m(-2)) adjustments to the temperature-humidity index (THI). Visual assessments of heat stress, based on panting scores (0 = no panting to 4 = severe panting), were collected from 1400 to 1700. Mean daily WSPD, black globe temperature at 1500, and minimums for nighttime WSPD, nighttime black globe THI, and daily relative humidity were found to have the greatest influence on panting score from 1400 to 1700 (R2 = 0.61). From hourly values for THI, WSPD, and RAD, panting score was determined to equal -7.563 + (0.121 x THI) - (0.241 x WSPD) + (0.00082 x RAD) (R2 = 0.49). Using the ratio of WSPD to THI and RAD to THI (- 1.992 and 0.0068 for WSPD and RAD, respectively), adjustments to the THI were derived for WSPD and RAD. On the basis of these ratios and the average hourly data for 1400 to 1700, the THI, adjusted for WSPD and RAD, equals [4.51 + THI - (1.992 x WSPD) + (0.0068 x RAD)]. Four separate cattle studies, comparable in size, type of cattle, and number of observations to the 3 original studies, were utilized to evaluate the accuracy of the THI equation adjusted for WSPD and RAD, and the relationship between the adjusted THI and panting score. Mean panting score derived from individual observations of black-hided cattle in these 4 studies were 1.22, 0.94, 1.32, and 2.00 vs. the predicted panting scores of 1.15, 1.17, 1.30, and 1.96, respectively. Correlations between THI and panting score in these studies ranged from r = 0.47 to 0.87. Correlations between the adjusted THI and mean panting score ranged from r = 0.64 to 0.80. These adjustments would be most appropriate to use, within a day, to predict THI during the afternoon hours using hourly data or current conditions. In addition to afternoon conditions, nighttime conditions, including minimum WSPD, minimum black globe THI, and minimum THI, were also found to influence heat stress experienced by cattle. Although knowledge of THI alone is beneficial in determining the potential for heat stress, WSPD and RAD adjustments to the THI more accurately assess animal discomfort.     

Use of Porcine Meal in Plant‐based Practical Diets for Pacific White Shrimp,Litopenaeus vannamei

Two growth trials were conducted to evaluate and confirm the efficacy of a porcine meal (PM) with high protein content (>90%) as an alternative feed ingredient in commercial‐type feed formulation for Pacific white shrimp, Litopenaeus vannamei. Six experimental diets were formulated for the two growth trials. The first five diets contained increasing levels (0, 1, 2, 4, and 6%) of PM as a replacement for soybean meal in a plant‐based diet with low inclusion level (6%) of fish meal (FM). The last experimental diet was produced utilizing 4.2% PM to completely replace FM. In Trial 1, shrimp (1.5 g initial mean weight, 20 shrimp/tank, n = 4) were offered test diets for 6 wk in a semirecirculation system. At the end of Trial 1, shrimp fed with the diet containing 6% PM exhibited significantly enhanced weight gain (WG), feed conversion ratio (FCR), and survival compared to those fed with the diet devoid of FM. As survival was poor across all treatments and different densities could mask growth results the trial was repeated. In Trial 2, shrimp (0.85 g, 15 shrimp/tank, n = 4) were offered diets for 6 wk. Dietary supplementation of PM at 6% significantly improved WG, FCR, and apparent net protein retention in contrast with the treatment devoid of FM, confirming the same trends in Trial 1. No significant difference was detected in protein, lipid, moisture, and mineral profiles of whole‐body shrimp as well as survival across all the treatments. Results of this study indicate that PM is a good high protein source in shrimp feeds, which can be included up to 6% in the low FM‐based diet without compromising the growth of shrimp.     

Clinical,pathologic, and toxicologic characterization of Salvia reflexa (lance-leaf sage) poisoning in cattle fed contaminated hay

Salvia reflexa (lance-leaf sage)-contaminated alfalfa hay was fed to ~500 mixed-breed beef cattle. Within hours of exposure, nearly half of the cattle developed lethargy, anorexia, depression, and recumbency, followed by bellowing, colic, and death. Even though the uneaten contaminated hay was removed the first day, nearly 100 animals died within the first 48 h. Three of these cattle were examined postmortem, and tissues and hay samples were collected for microscopic and chemical analysis. Several days later, a smaller number of the clinically poisoned cattle developed neurologic disease with aberrant behavior, aggression, icterus, blindness, exhaustion, and death. A total of 165 cattle were fatally poisoned. Poisoned cattle had swollen, dark, mottled livers that had a prominent nutmeg-like lobular pattern on cut section. Histologically, there was severe centrilobular-to-panlobular hepatic necrosis with marked hepatocellular swelling, degeneration, and necrosis. The surviving cattle developed liver disease characterized by altered serum biochemical analyses and microscopic hepatocellular degeneration and necrosis. In subsequent biopsies and analysis, these lesions resolved within 6–7 mo. After confirming toxicity of the hay in cattle, goats, and mice, followed by a mouse bioassay–guided chemical fractionation process, Salvia reflexa was identified as the contaminant in the hay responsible for the hepatotoxicity. S. reflexa has not been reported previously to cause fatal hepatotoxicity in livestock in North America, to our knowledge.