Effects of Mixed Cropping on a Soil Nematode Community in Honduras

Nematode-resistant tropical legumes are effective in reducing populations of plant-parasitic nematodes when used in rotation systems. Mixed cropping is a common practice of many small farmers in Central America, but little is known about the effects of tropical legumes on nematode communities under these systems. To examine the effects of intercropping on the nematode fauna associated with squash (Cucurbita pepo) and cucumber (Cucumis sativa) in Honduras, two field experiments were conducted to compare nematode density and diversity in soil under cucurbits grown as a monocrop with that in soil under cucurbits intercropped with alfalfa (Medicago sativa) or hairy indigo (Indigofera hirsuta). A parallel series of field tests compared soil nematode communities associated with a cucurbit monocrop and a cucurbit intercropped with marigold (Tagetes patula), which may decrease nematode populations through the production of toxic root exudates. Among all four tests, over a period of 90 days, there were no consistent differences in densities of various nematode genera or trophic groups in intercropped versus monocropped plants, nor were there consistent differences in community diversities among treatments.     

A genome map of divergent artificial selection between Bos taurus dairy cattle and Bos taurus beef cattle

A number of cattle breeds have become highly specialized for milk or beef production, following strong artificial selection for these traits. In this paper, we compare allele frequencies from 9323 single nucleotide polymorphism (SNP) markers genotyped in dairy and beef cattle breeds averaged in sliding windows across the genome, with the aim of identifying divergently selected regions of the genome between the production types. The value of the method for identifying selection signatures was validated by four sources of evidence. First, differences in allele frequencies between dairy and beef cattle at individual SNPs were correlated with the effects of those SNPs on production traits. Secondly, large differences in allele frequencies generally occurred in the same location for two independent data sets (correlation 0.45) between sliding window averages. Thirdly, the largest differences in sliding window average difference in allele frequencies were found on chromosome 20 in the region of the growth hormone receptor gene, which carries a mutation known to have an effect on milk production traits in a number of dairy populations. Finally, for the chromosome tested, the location of selection signatures between dairy and beef cattle was correlated with the location of selection signatures within dairy cattle.     

Genotype by environment interaction in Nelore cattle from five Brazilian states

Records from 75,941 Nelore cattle were used to determine the importance of genotype by environment interaction (GEI) in five Brazilian states. (Co)variance components were estimated by single-trait analysis (with yearling weight, W450, considered to be the same trait in all states) and multiple-trait analysis (with the record from each state considered to be a different trait). The direct heritability estimates for yearling weight were 0.51, 0.39, 0.44, 0.37 and 0.41 in the states of Goiás, Mato Grosso, São Paulo, Mato Grosso do Sul and Minas Gerais, respectively. The across-state genetic correlation estimates between Goiás and Mato Grosso, Goiás and Minas Gerais, São Paulo and Minas Gerais, and Mato Grosso do Sul and Minas Gerais ranged from 0.67 to 0.75. These estimates indicate that GEIs are biologically important. No interactions were observed between Goiás and São Paulo, Goiás and Mato Grosso do Sul, Mato Grosso and São Paulo, Mato Grosso and Mato Grosso do Sul, Mato Grosso and Minas Gerais, or São Paulo and Mato Grosso do Sul (0.82 to 0.97). Comparison of single and multiple-trait analyses showed that selection based on the former was less efficient in the presence of GEI, with substantial losses (up to 10%) during selection.     

Meiotic abnormalities in backcross lines of hybrid Haemonchus

Le Jambre L. F. and Royal W. M. 1979. Meiotic abnormalities in backcross lines of hybrid Haemonchus. International Journal for Parasitology10: 281–286. Hybrid worms from the reciprocal matings between Haemonchus contortus and H. placei were backcrossed to the parent species. Six of the possible eight backcrosses produced fertile eggs. The six backcross lines were passaged through sheep for four generations. The adults of this generation had various levels of meiotic abnormality as evidenced by abnormal variations in chromosome structure and aneuploidy. The eggs from backcross lines with a degree of meiotic abnormality had the lowest percentage hatch. Four of the six backcross lines required a higher temperature for larval development than did H. contortus. The size of the third-stage larvae varied from one with larvae larger than H. placei to one line with larvae smaller than H. contortus.     

Untersuchungen zum Einfluß der Lagerungsdauer auf den Futterwert von Strohpellets

Während der Tränkperiode (ca. 55. Lebenstag) und 2 Wochen nach dem vollständigen Tränkmilchentzug (ca. 80. Lebenstag) wurde an Kälbern, welche mit Duodenalbrückenfisteln ausgerüstet waren, der Einfluß eines Heuanteiles in der Ration in Höhe von 6, 10, 14 bzw. 18 % in der Tränkperiode und von 16,23, 31 bzw. 37% (auf TS‐Basis) in der Periode nach dem Milchentzug auf den ruminalen N‐Umsatz geprüft.

Mit der Steigerung des Heuanteiles in der Ration für ruminerende Kälber reduzierte sich in der Tendenz die duodenale NAN‐Passage, deren Bakterien‐N‐Anteil, die postruminale NAN‐Verdaulichkeit sowie, durch eine schlechtere Verwertung des für die Bakterien‐N‐Synthese verfūgbaren N bedingt, die Bakterien‐N‐Syntheserate. Die scheinbare Fermentation der organischen Substanz war in der Tendenz mit wachsendem Heuanteil in der Ration gesteigert worden.     

Genome-wide linkage disequilibrium in two Japanese beef cattle breeds

There is little knowledge about the degree of linkage disequilibrium (LD) in beef cattle. This study aims to perform a genome-wide search for LD in Japanese Black and Japanese Brown beef cattle and to compare the level of LD between these two breeds. Parameter D' (the LD coefficient) was used as a measure of LD, and LD was tested for significance of allelic associations between syntenic and between non-syntenic marker pairs. Effects of breed, chromosome, genetic map distance and their interactions with D' were tested based on least squares analyses. Both breeds showed high levels of LD, which ranged over several tens of cM and declined as the marker distance increased for syntenic marker pairs. A rapid decline of the D' value was observed between markers that were spaced 5 and 20 cM apart. LD was significant in most cases for marker pairs <40 cM apart but was not significant between non-syntenic loci. The pattern of LD found in these two breeds was similar to that previously published for dairy cattle. The D' value between breeds was not significantly different (P > 0.05), but the interaction between breed and chromosome was highly significant (P < 0.001). Genetic selection seems to have caused the heterogeneity of the D' values among chromosomes within breed. These results indicate that LD mapping is a useful tool for fine-mapping quantitative trait loci of economically important traits in Japanese beef cattle.