Data extracted from reports on cross-breeding of Bos taurus and Bos indicus cattle for milk production were used to compare the merits of various Bos taurus breeds for this purpose. The study was restricted to projects in which two or more taurus breeds had been used simultaneously, and to records on F1 crosses. The only taurus breeds represented were Friesian, Brown Swiss and Jersey.Brown Swiss crosses were the oldest and Jersey crosses the youngest at first calving; both differed significantly from Friesian crosses. In milk yield Friesian crosses were the highest and Jersey crosses the lowest, and again all differences were significant. Jersey crosses had significantly shorter calving intervals than the other crosses.The ranking of the crosses was very consistent across projects. The difference in milk yield between Friesian and Jersey crosses increased proportionately with level of production. 相似文献
Data extracted from reports on Bos taurus × Bos indicus crossbreeding were used to estimate the amount of heterosis in these crosses. Traits studied were age at first calving, milk yield, lactation length, and calving interval. The estimates obtained were (percent of midparent means in parentheses):
Complex systems, such as landscapes, are composed of different critical levels of organization where interactions are stronger within levels than among levels, and where each level operates at relatively distinct time and spatial scales. To detect significant features occurring at specific levels of organization in a landscape, two steps are required. First, a multiscale dataset must be generated from which these features can emerge. Second, a procedure must be developed to delineate individual image-objects and identify them as they change through scale. In this paper, we introduce a framework for the automatic definition of multiscale landscape features using object-specific techniques and marker-controlled watershed segmentation. By applying this framework to a high-resolution satellite scene, image-objects of varying size and shape can be delineated and studied individually at their characteristic scale of expression. This framework involves three main steps: 1) multiscale dataset generation using an object-specific analysis and upscaling technique, 2) marker-controlled watershed transformation to automatically delineate individual image-objects as they evolve through scale, and 3) landscape feature identification to assess the significance of these image-objects in terms of meaningful landscape features. This study was conducted on an agro-forested region in southwest Quebec, Canada, using IKONOS satellite data. Results show that image-objects tend to persist within one or two scale domains, and then suddenly disappear at the next, while new image-objects emerge at coarser scale domains. We suggest that these patterns are associated to sudden shifts in the entire image structure at certain scale domains, which may correspond to critical landscape thresholds.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
Techniques for the production of raspberry long canes with high yield potential were studied on a research station and in two commercial nurseries in South Norway. Potted ‘Glen Ample’ plants were grown in the open and in polyethylene greenhouses during two seasons in order to optimize cultural practices. Dates of propagation and transfer to the production sites were varied. Following cold storage from December to early June, the canes were tipped (cut) at 160 cm height and grown in open plastic tunnels in the fruiting season for the evaluation of growth and yield performance. Remarkable berry yields of 1.5–3.8 kg per plant (cane) were regularly achieved. When grown in the open, later starts than June 1 (June 15 and July 1) successively reduced yields. On the other hand, an earlier start involves risks of growth cessation due to low spring temperature. When grown in greenhouses, high yields were still possible when plants were transferred from propagation conditions as late as July 1, although optimal yields of nearly 4 kg per plant were obtained with transfer on June 15. In a year with unusually high summer temperatures, the yields of canes produced in the open and in greenhouses did not vary significantly, whereas in the second year with normal summer temperatures, canes produced in greenhouses consistently out-yielded those produced in the open by about 1 kg per cane. Regression analyses revealed that high yields were associated with fruiting cane architecture traits such as cane height, number and length of laterals, and a low proportion of dormant buds. The single most important component was lateral length which alone accounted for 82% of the yield variation. Since lateral lengths increased from the shoot tip towards the base, cane heights in excess of 2 m are required for the attainment of top yields as the uppermost nodes with short and low-yielding laterals then can be eliminated by tipping. 相似文献
Records on approximately one million calvings were examined for presence of a gene with major effect on the frequency of multiple births. The records were summarized by parity of the cow and registration number of the cow's sire, and an overall age-corrected frequency of multiple births computed for daughters of each sire.The distribution of 876 progeny groups with more than 100 calvings showed no sign of discontinuity, and the same was true for 120 progeny groups with more than 1000 calvings. The daughters of one particular bull had 9.95% multiple births in about 6000 calvings. This bull left more than 80 sons which were used for artificial insemination. The sons ranged from less than one to more than 10% multiple births among their daughters, but no segregation was observed.Heritability estimates (on the binomial scale) ranged from 0.006 in parity 1 to about 0.04 in parities 3–5.Genetic correlations between incidence of multiple births in first and subsequent parities were estimated at 0.52–0.64, while those among parities 2–5 were from 0.70 to 0.84. 相似文献
Hypersaline water derived from agricultural practices primarily in arid landscapes can impact fisheries in streams receiving run-off from fields. Previous studies have indicated significant elevation in the toxicity of thio-ether pesticides by hypersaline water in certain species of euryhaline fish due to enhanced formation of sulfoxide metabolites which may be more toxic than the parent compounds. The objectives of this study were to evaluate the effects of salinity on the toxicity of the thio-ether organophosphate pesticide, fenthion in three species of euryhaline fish: rainbow trout (Oncorhynchus mykiss), striped bass (Morone saxatilis X Morone chrysops), tilapia (Oreochromis mossambicus) and determine whether a relationship was observed between toxicity and enantioselective sulfoxidation. Stereochemical formation and total sulfoxide formation did not mirror acute toxicity in the three species exposed in fresh or hypersaline conditions. Mortality of striped bass and rainbow trout due to fenthion exposure was enhanced by hypersaline treatments and a trend towards increased toxicity was observed in tilapia. In liver microsomes of rainbow trout, inhibition of cytochrome P450 (CYP) caused a respective 7- and 3-fold increase in sulfoxide formation in liver microsomes fresh and saltwater fish, and a significant increase in the formation of the (+)R-sulfoxide. CYP inhibition also caused a significant elevation of the (+)R-sulfoxide in freshwater striped bass, but not in hypersaline-treated bass. The results indicated contribution by CYP in the sulfoxidation of fenthion as well as the formation of other metabolites in all three species. In summary, hypersaline conditions impacted fenthion toxicity under conditions that appeared to be independent of fenthion sulfoxide formation indicating a much more complex mechanism of action for compounds with phosphorothioate and thio-ether structural features potentially involving multiple oxidative pathways. 相似文献
Somatic cell counts of 2570 milk samples from 765 cows collected bimonthly from November 1975 to May 1976 were transformed to logarithmic values and analysed statistically. Components of variance were estimated as follows: Herds 0.033 (13 %), age groups 0.021 (8%), cows (within herds and age groups) 0.080 (31%), months 0.014 (6%), residual 0.107 (42%). Correction of actual cell counts for the influence of milk yield on the day of sampling led to only small changes in the magnitude of the various components. The coefficient of correlation between samples from the same cow was computed as 0.60 when the samples were from the same lactation, and 0.37 for samples from consecutive lactations.The proportionately small variation among herds as compared to the variation among cows of the same herd throws doubt on the efficiency of cell counting in samples of herd milk as a way of identifying cows with high cell counts. 相似文献
The habitat requirements and effects of forest management on insects belonging to higher trophic levels are relatively unknown in forest ecosystems. We tested the effect of forest successional stage and dead wood characteristics on the saproxylic parasitoid (Hymenoptera, Ichneumonoidea) assemblage in boreal spruce-dominated forests in northern Sweden. Within each of nine areas, we selected three sites with different management histories: (1) a clear-cut (2) a mature managed forest and (3) an old-growth forest. Parasitoids were collected in 2003 using eclector traps mounted on fresh logs, which were either untreated (control), burned, inoculated with fungi, or naturally shaded, and on artificially-created snags.Both forest type and dead wood characteristics had a significant effect on parasitoid assemblages. Grouped idiobionts and some species, such as Bracon obscurator and Ontsira antica, preferred clear-cuts, while others, such as Cosmophorus regius (Hym., Braconidae) and other koinobionts, were associated with older successional forest stages. No single dead wood substrate was sufficient to support the entire community of parasitoids in any forest type, even when the regular host was present. In particular, snags hosted a different assemblage of species from other types of dead wood, with parasitoids of Tetropium spp. such as Rhimphoctona spp. (Hym., Ichneumonidae) and Helconidea dentator (Hym., Braconidae) being abundant. These results indicate that a diversity of dead wood habitats is necessary to support complete assemblages of beetle-associated parasitoids from early successional stages of dead wood and that parasitoids may be more sensitive to habitat change than their hosts. 相似文献
The inhibitory effect of peptide-precipitating lignosulphonic acids on the proteolytic activity of pepsin in vitro has been studied. When an unfractionated lignosulphonic acid preparation was used, total inhibition of the activity of 5 µg crystalline pepsin was obtained by addition of about 15 mg of lignosulphonic acids.The greatest inhibitory effect was seen with the high-molecular weight lignosulphonic acids, but an effect was also seen with middle-and low-molecular weight lignosulphonic acids.A reduction in the inhibitory effect was seen when the experiments were performed in the presence of arginine. The inhibition mechanism is discussed in relation to the peptide-precipitating ability of the lignosulphonic acids.No obvious protection against the appearance of stomach ulcers in four pigs receiving an ulcerogenic diet was seen. 相似文献
Summary Mpwapwa cattle are a synthetic dual-purpose breed developed in the Livestock Production Research Institute at Mpwapwa in Tanzania. The breed has received about 60% of its inheritance from improved dairy breeds originating in the Indian subcontinent (Red Sindhi and Sahiwal), about 30% from African zebu breeds (Boran and Tanzania Shorthorn zebu) and the remaining 10% from European breeds (mainly Ayrshire). The breed comprises only about 1,000 animals in two major herds and is threatened by extinction.The following production parameters have been reported for the herd at the Livestock Production Research Institute, Mpwapwa: age at first calving 45.4 months; calving interval 447 days; lactation milk yield (short lactations deleted) 1,447 to 1,628 kg; daily gain 259g; carcass weight of steers (four years) 229 kg.
Ganado Mpwapwa—Una Sintesis Indo-Euro-Africana
Resumen El ganado mpwapwa es una raza del doble propósito sintética, desarrollada en el Instituto de Investigación y Producción Ganadera en Mpwapwa, Tanzania. La raza ha recibido cerca del 60% de su herencia de razas lecheras majoradas originarias del subcontinente Indú (Red Sindhi y Sahiwal), cerca del 30% de razas cebú (Boran y Shorthorn Cebú de Tanzania), y el 10% restante de razas europeas (predominantemente Ayrshire). La raza está representada por mil animales divididos en dos hatos y se está extinguiendo.En el Instituto de Investigación y Producción Ganadera se informan los siguientes parámetros productivos: edad a la primera parición, 45, 4 meses; intervalo entre partos, 447 días; producción lechera por lactación, 1447 1628 kg; aumento de peso diario, 259 g; peso de la canal en novillos (cuatro años), 229 kg.
Les Bovins Mpwapwa—Une Synthèse Indo-Euro-Africaine
Résumé La Mpwapwa est une race de synthèse à deux fins, créée à l'Institut de recherche pour la production animale de Mpwapwa en Tanzanie. Elle détient environ 60 p. 100 de son patrimoine héréditaire de races laitières originaires du sous-continent indien (Red Sindhi et Sahiwal), environ 30 p. 100 de races de zébus africains (Boran et Tanzanian Shorthorn), les 10 p. 100 restants étant d'origine européenne, principalement Ayrshire. La troupeaux principaux, est menacée d'extinction. Les paramètres de production suivants ont été enregistrés pour le troupeau de l'Institut de recherche pour la production animale à Mpwapwa: âge au ler vêlage: 45, 4 mois; intervalle entre 2 vêlages: 447 jours; rendement laitier par lactation: 1447 à 1628 kg, les lactations courtes ayant été négligées; gain de poids quotidien: 259 g; poids de carcasse des bouvillons à quatre ans: 229 kg.
