Economic and Risk Effects of Rotation Based on a 14-Year Irrigated Potato Production Study in Manitoba     

Mohammad Khakbazan  Ramona M. Mohr  Jianzhong Huang  Erik Campbell  Karl M. Volkmar  Dale J. Tomasiewicz  Alan P. Moulin  Doug A. Derksen  Byron R. Irvine  Debra L. McLaren  Alison Nelson 《American Journal of Potato Research》2018,95(3):258-271

Crop rotations can be used to optimize economic return by preserving or enhancing soil quality and reducing pest pressure. A field experiment consisting of six rotations of potato with canola (P-C), wheat (P-W), canola-wheat (P-C-W), oat-wheat (P-O-W), wheat-canola-wheat (P-W-C-W), and canola underseeded to alfalfa-alfalfa-alfalfa (P-C(A)-A-A) organized in a Randomized Complete Block Design was established on a clay loam soil in Manitoba, Canada and monitored for fourteen years to assess the relative economic performance of potato in each rotation. A stochastic budget based on returns and risk of returns trade-offs was used to determine each rotation’s profitability. While differences in average annual net income of all crops between rotations were not significant, the P-C-W rotation was the most stable. Despite the economic advantage of P-C in the first two cycles, longer P-C-W or P-C(A)-A-A rotations are recommended, as two-year rotations increase plant disease and decrease economic viability in the long run.  相似文献   

Influence of pretransit feeding regimen and posttransit B-vitamin supplementation on stressed feeder steers   总被引：4，自引：0，他引：4  

N A Cole  J B McLaren  M R Irwin 《Journal of animal science》1979,49(2):310-317

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Faecal carriage of verocytotoxin-producing Escherichia coli O157 in cattle and sheep at slaughter in Great Britain     

Paiba GA  Gibbens JC  Pascoe SJ  Wilesmith JW  Kidd SA  Byrne C  Ryan JB  Smith RP  McLaren M  Futter RJ  Kay AC  Jones YE  Chappell SA  Willshaw GA  Cheasty T 《The Veterinary record》2002,150(19):593-598

A 12-month abattoir survey was conducted between January 1999 and January 2000, to determine the prevalence of faecal carriage of verocytotoxin-producing Escherichia coli O157 (VTEC O157) in cattle and sheep slaughtered for human consumption in Great Britain. Samples of rectum containing faeces were collected from 3939 cattle and 4171 sheep at 118 abattoirs, in numbers proportional to the throughput of the premises. The annual prevalence of faecal carriage of VTEC O157 was 4.7 per cent (95 per cent confidence interval 4.1 to 5.4) for cattle and 1.7 per cent (1.3 to 2.1) for sheep, values which were statistically significantly different from each other (P < 0.001). The organisms were recovered from both cattle and sheep slaughtered throughout the year and at abattoirs in all regions of the country, but the highest prevalence was in the summer. The most frequency recovered VTEC O157 isolates were phage types 2, 8 and 21/28 in cattle and 4 and 32 in sheep, the five most frequently isolated phage types associated with illness in people in Great Britain during the same period.  相似文献   

Effects of weather variables on grain mould of sorghum in South Africa     

G. Tarekegn ‡  N. W. McLaren ‡  W. J. Swart 《Plant pathology》2006,55(2):238-245

Effects of weather variables of mould development on sorghum grain were studied over three consecutive seasons in South Africa. Five sorghum hybrids planted at different dates ensured developing seeds were exposed to different weather conditions. Incidence of grain mould fungi was determined at harvest by incubating seeds on 2% malt extract agar. Averages of different weather variables (maximum and minimum temperatures, maximum relative humidity, total precipitation and frequency of precipitation) were determined for all permutations of weekly time intervals for a 2-month postflowering period to identify when these variables and pathogen incidence were significantly correlated. Significant correlations were used to develop models to quantify relationships between variables. Significant positive correlations were observed between the incidence of mould fungi and weather 4–6 weeks after flowering in the shorter season hybrid cv. Buster, and 5–8 weeks after flowering in the remaining hybrids. In most hybrids, correlations between the incidence of grain mould pathogens, including Alternaria alternata , Curvularia spp. ( C. lunata and C. clavata ), Fusarium spp. ( F. proliferatum and F. graminearum ), and Drechslera sorghicola , and average minimum temperature, total rainfall and frequency of rainfall were significant ( P =  0·05). In four hybrids, models showing a linear relationship between the logarithm of pathogen incidence and minimum temperature, and in one hybrid, between pathogen incidence and rainfall frequency, were developed. Depending on the hybrid, models that used minimum temperature as predictor described 60–82% of variation in the incidence of pathogens. Frequency of rainfall explained 93% of the variation in pathogen incidence in one sorghum hybrid genotype. Evaluation of the models using an independent data set yielded average prediction errors near zero, indicating that the models were acceptable.  相似文献   

Detection of linkage between genetic markers and genes that affect growth and carcass traits in pigs.   总被引：2，自引：0，他引：2  

P A Clamp  J E Beever  R L Fernando  D G McLaren  L B Schook 《Journal of animal science》1992,70(9):2695-2706

Segregation of paternal marker alleles in the progeny of a single boar was used to estimate linkage between the marker genes and associations of these genes with quantitative trait loci (QTL). The sire was heterozygous at four polymorphic marker loci, haptoglobin (HP), glucosephosphate isomerase (GPI), phosphogluconate dehydrogenase (PGD), and esterase D (ESD), and sired 30 litters during an 8-mo period. Glucosephosphate isomerase and PGD were linked (theta = .09; P less than .005). The phase of these two loci in the sire was determined to be GPI A-PGD B, GPI B - PGD A. NO other linkages were detected. Growth (135 less than or equal to n less than or equal to 172) and carcass data (70 less than or equal to n less than or equal to 80) were analyzed assuming a fixed linear model. Least squares means were compared for differences in growth and carcass traits between pigs that inherited alternative paternal marker alleles. Pigs that inherited the GPI A allele from the sire had a 22-g higher daily live weight gain postweaning and reached 103 kg live weight in 2.6 fewer days than did pigs that inherited the GPI B allele (P less than .05), indicative of the presence of gene(s) that affect rate of gain linked to the GPI locus. Pigs that inherited the PGD B allele had a .14 unit higher score for muscle firmness (score ranged from 1 to 3 units) than pigs that inherited the PGD A allele (P less than .05). Pigs that inherited the HP 3 allele had a .06-kg higher weaning weight and a .11 lower ham muscle mass score than did pigs that inherited the HP 2 allele from the sire (P less than .05). No associations with quantitative traits were detected for ESD.  相似文献   

Genetic analyses of growth, real-time ultrasound, carcass, and pork quality traits in Duroc and Landrace pigs: I. Breed effects.     

L L Lo  D G McLaren  F K McKeith  R L Fernando  J Novakofski 《Journal of animal science》1992,70(8):2373-2386

Knowledge of breed effects on carcass and pork quality traits is required to develop commercial crossbreeding programs that emphasize product quality. A 2 x 2 diallel mating system involving Landrace and Duroc pigs was used to estimate individual heterosis, direct breed effects and reciprocal cross differences for post-weaning growth, real-time ultrasound, carcass, and pork quality traits. Data from 5,649 pigs and 960 carcasses representing 65 and 49 sires, respectively, were analyzed assuming animal models. Duroc-sired pigs had 2.1 cm shorter carcasses with 7.3 mm less 10th rib backfat (BF), 4.4 cm2 larger longissimus muscle area (LMA), yielded 2.1 kg more estimated fat standardized lean (FSL), gained 16.5 g more estimated lean per day of age (LDOA), and had 1.0% less water (PWAT) and 1.9% more intramuscular fat (IMF) in the longissimus muscle than did Landrace-sired pigs (P less than .01), adjusted to an off-farm live weight of 111 kg. Reciprocal cross differences were detected for BF, LMA, FSL, LDOA and for subjective marbling, firmness, and muscling scores (P less than .01). Durocsired F1 barrows had 6.3 mm less BF and 5.9 cm2 larger LMA, yielded 3.2 kg more FSL, gained 22.3 g more LDOA, and had less marbling in the longissimus muscle and heavier ham muscling than reciprocal cross barrows. Heterosis estimates (P less than .05) were 27.6 g/d (3.2%) for ADG, -5.8 d (-3.6%) for off-test age, 2.7 cm (3.4%) for carcass length, 1.5 kg (7.2%) for FSL, 14.7 g (5.7%) for LDOA, -.07 (-3.6%) for muscle color, -.5% (-13.2%) for IMF, and .3% (.3%) for PWAT. Breed effects were not detected (P greater than .10) for muscle pH, cooking loss, shear value, and water-holding capacity or for eating quality traits. Reciprocal cross differences suggest an advantage in using the Duroc as a terminal sire, but improved carcass composition and higher intramuscular fat did not seem to affect eating quality traits.  相似文献   

Absence of Mycoplasma bovis in unprocessed frozen bull semen from Canadian artificial insemination centres     

M M Garcia  R B Truscott  J McLaren  R B Stewart  B Kingscote  J Burchak 《The Veterinary record》1986,119(1):11-12

From 1979 to 1984 approximately 2950 unprocessed frozen semen samples from nine Canadian artificial insemination centres were cultured for Mycoplasma bovis. M bovis was not detected in any of them.  相似文献   

In vitro selection of salt-tolerant cell lines in kallar grass [Diplachne fusca (L.) Beauv.]     

MALEE NANAKORN  WALAIKARN JIAMJETJAROON  SRISOM SUWANAWONG  CHALERMCHAI WONGWATTANA  IE SUNG SHIM 《Weed Biology and Management》2003,3(1):49-52

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Plasmodium infection in a Leadbeater's possum (Gymnobelideus leadbeateri)          下载免费PDF全文

TF Scheelings  PJ McLaren  L Tatarczuch  RF Slocombe 《Australian veterinary journal》2016,94(8):299-303

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An extended outbreak of congenital chondrodysplasia in calves in South East Australia     

Cave JG  McLaren PJ  Whittaker SJ  Rast L  Stephens A  Parker EM 《Australian veterinary journal》2008,86(4):130-135

OBJECTIVE: To report an outbreak of congenital chondrodystrophy in calves in South East Australia. METHODS: District veterinarians investigated reported cases of calf deformities. Owners of affected herds were interviewed using a standard questionnaire to identify potential risk factors. Dams of several affected calves were serologically tested for Akabane virus, Aino virus, pestivirus and bluetongue, and affected calves were tested for pestivirus antigen and serum immunoglobulin concentrations. Gross and histopathological examinations of numerous calves were performed, concentrating on the musculoskeletal system. RESULTS: A case definition of distinctive skeletal deformities was established, and 89 property owners reported calves with chondrodystrophy in Spring 2003, 2004 or 2005. Some 14 property owners reported affected calves in more than one year. Prevalence and severity of deformity varied greatly between and within properties. None of breed, sex, age of dam, lineage, pasture type, supplementary feeding, fertiliser use or toxic plants was consistently associated with the disease. All dams experienced hot, dry conditions during the first trimester of pregnancy and were exposed to adverse conditions thereafter. Consistently dams were reported to have been grazing undulating to hilly terrain during early pregnancy. All serological tests were negative for Akabane virus, Aino virus, pestivirus and bluetongue. Histopathology of affected skeletal samples showed chondrodysplasia. CONCLUSION: The outbreak had similarities with previous outbreaks reported in the region. No specific aetiology could be determined. There is some evidence that the cause of the deformities could be a manganese deficiency during foetal development. Ongoing work to test this hypothesis is therefore warranted.  相似文献