G. H. Crow

Molecular mapping of quantitative trait loci for yield and yield components in spring wheat (Triticum aestivum L.)

An F1 derived doubled haploid (DH) population of 402 lines from the adapted spring wheat cross Superb (high yielding)/BW278 (low yielding) was developed to identify quantitative trait loci (QTL) associated with yield and yield components. A subset of the population (186 lines) was evaluated in replicated field trials in 2001 and 2002 at six locations in Manitoba and Saskatchewan, Canada. Agronomic parameters, grain yield and yield components including 1,000 grain weight, harvest index, average seed weight spike−1, seed number spike−1 and spikes number m−2 were measured. A genetic map was constructed with 268 microsatellite marker loci and included two morphological genes, reduced plant height, Rht-B1b, and the presence/absence of awns, B1. Composite interval mapping was conducted to estimate the location and effect of QTL associated with the evaluated traits. A total of 53 QTL were identified on 12 chromosomes for the 9 evaluated traits with the coefficient of determination ranging from 0.03 to 0.21 of the total variation. The increase in yield and yield components ranged from 4.5 to 17.1% over the population mean. The five grain yield QTL were detected on chromosomes 1A, 2D, 3B, and 5A and showed a combined increase of 34.4%, over the population mean. The alleles from Superb were associated with increased yield for four of the five QTL. This study identified potential chromosome segments for use in marker-assisted selection to improve yield and yield components in spring wheat.

The nutritive value of barley, rye, wheat and corn for young chicks as affected by use of a Trichoderma reesei enzyme preparation

Two experiments were conducted to establish the effect on the performance of growing Leghorn chicks of different concentrations of a crude enzyme preparation when added to diets containing high amounts of barley, rye, wheat or corn. In the first experiment it was shown that the enzyme which had high xylanase and cellulase activities considerably improved (P 0.05). The wheat and barley-based diets that were supplemented with enzyme yielded weight gains that were the same as obtained with the corn diets. Enzyme supplementation also improved (P 0.05). Enzyme treatment reduced the water content of the colon in birds fed diets containing all of the different grains (P<0.05) with the effect being greatest for chicks fed barley (6%) and wheat (5%), intermediate for those fed rye (3%) and lowest for the corn-fed birds (1%). These results demonstrate that a low dietary inclusion rate of a crude enzyme preparation that has high activities of two enzymes (xylanase and cellulase) can considerably improve the nutritional value of barley and rye, probably that of wheat, but not that of corn.

Effects of diet type and enzyme addition on growth performance and gut health of broiler chickens during subclinical Clostridium perfringens challenge

The effects of diet type (corn- vs. wheat-based) and multicarbohydrase addition on growth performance, digesta pH and viscosity, intestinal populations of Clostridium perfringens and lactic acid bacteria, and gut lesion score (from 0 to 4, where 0 = no gross lesions, 4 = severe extensive necrosis) of broiler chickens during oral challenge with C. perfringens (none or 10(8) cfu/bird on d 13) were studied in a 39-d experiment. A total of 1,216 male Ross-308 chickens was assigned to 8 dietary treatments in a randomized complete block design providing 8 replicate pens per treatment. Diets were formulated to meet the NRC protein requirement but were suboptimal in energy level. When compared with birds fed corn-based diets, chickens fed wheat-based diets had inferior (P < 0.01) final BW (2.49 vs. 2.59 kg) and feed conversion ratio (FCR; 1.83 vs. 1.78). Pathogen challenge significantly (P < 0.05) impaired growth performance and increased C. perfringens numbers and average lesion score. Increased (P < 0.01) C. perfringens counts (2.4 vs. 1.5 log(10) cfu/g of digesta) and intestinal lesion score (0.9 vs. 0.4) were observed for challenged birds fed wheat-based diets. No difference in digesta pH and lactic acid bacteria numbers were found among the treatments. Enzyme addition to both the corn- and wheat-based diets increased bird final BW (2.57 vs. 2.51 kg; P < 0.01), decreased overall FCR (1.78 vs. 1.83; P < 0.01), and, in those consuming wheat-based diets, reduced digesta viscosity (from 4.1 to 2.7 mPa.s; P < 0.01). Enzyme supplementation assisted the challenged birds in maintaining their optimal growth performance by improving (P < 0.05) average daily gain (59.5 vs. 56.9 g) in those consuming corn-based diets and FCR (1.83 vs. 1.90) in those consuming wheat-based diets to values similar to those observed in control birds (59.7 g/d and 1.84, respectively). In conclusion, enzyme addition improved growth performance and mitigated the negative effects of C. perfringens challenge.

Estimating the Values of Cattle Characteristics Using an Ordered Probit Model

In this study we evaluate the preferences of cattle producers in Manitoba, Canada, for different cattle characteristics using the conjoint analysis methodology. Preferences are estimated for three different segments of the cattle production system: purebred breeders, commercial cow-calf producers, and cattle feeders. Data were collected for steers and bulls via a mail survey in 1993. Here we provide relative valuation for the different characteristics by segment of the cattle sector. Evidence is provided that different segments of the cattle sector do not value characteristics the same. For example, purebred breeders have higher preferences for reproduction traits, while feedlot operators give higher values to commercial attributes such as heavy slaughter weight and carcass yield. The different valuations of characteristics across segments of the cattle sector suggest that signals regarding preferences may be noisy. As a result, it might be difficult to design some breed improvement programs to be broadly acceptable, if they have differential benefits to the different segments of producers, when using standard profit-oriented selection indices. Copyright 1997, Oxford University Press.

Standardized ileal amino acid digestibility in wheat distillers dried grains with solubles for broilers

A study was conducted to estimate the ileal digestibility of amino acids (AA) in 5 different samples of wheat distillers dried grains with solubles (DDGS) fed to broilers. Two hundred sixteen male Ross broiler chicks were fed a commercial starter diet from d 1 to 15 of age followed by the test diets from d 15 to 21. The 5 test diets consisted of a DDGS sample or wheat as the sole source of AA, dextrose, minerals, and vitamins. Chromic oxide (0.3%) was included in all diets as a digestibility marker. Each test diet was randomly assigned to 6 replicate cages, each with 6 birds. On d 21, birds were killed to sample ileal digesta for determining the apparent (AID) and standardized (SID) ileal AA digestibilities. The SID values were calculated using ileal endogenous AA losses previously determined in our laboratory. Among the indispensable AA in wheat DDGS, the lowest and highest AID average values were observed for Lys (35.6%) and Phe (79.2%), respectively. The most variable AID estimates of wheat DDGS samples were observed for Lys (24.4 to 45.7%), Thr (48.2 to 60.9%), and His (57.4 to 69.1%) as indispensable and Asp (32.5 to 50.9%), Gly (49.6 to 63.1%), and Ala (53.6 to 66.8%) as dispensable AA, respectively. Apparent ileal digestibility estimates of the wheat sample for Lys, Thr, His, Gly, and Ala were 77.5, 74, 83.6, 79.3, and 78.9%, respectively. All AA digestibility estimates for both AID and SID determined in wheat were higher than in wheat DDGS samples (P < 0.05). Considering both AID and SID coefficients of wheat DDGS samples, Lys was the least digestible AA, averaging 35.6 and 40.0%, respectively. Using SID values in practical diet formulation can increase accuracy, prevent overformulation of diets, and reduce cost of safety margins.

The incidence and distribution of ochratoxin A in western Canadian swine

A survey of swine destined for slaughter in Manitoba was conducted to examine the incidence of ochratoxin A (OA) in swine herds from different regions of Manitoba throughout the year 1989-90. Thirty-six percent of the serum samples which were collected from 1600 pigs contained detectable levels of OA. The identity of this toxin was confirmed using liquid chromatography-mass spectrometry and enzymatic hydrolysis. There was a significant effect of the region from which the herds originated, as well as the season in which the samples were collected on both the incidence (p < 0.001) and concentration of OA (p < 0.001). In July, 65% of the samples contained detectable levels of OA, compared with 38, 21 and 17%, in April, October and January respectively. Furthermore, 24% of the samples collected in July contained greater than 15 ng/ml of OA, while only 2, 9, and 1% of the samples collected in April, October and January respectively, contained greater than 15 ng/ml of OA. Based on the six samples collected from each herd, it appears that the presence and concentration of OA within a herd may be estimated from a limited number of animals per herd.

The effect of microbial-nutrient interaction on the immune system of young chicks after early probiotic and organic acid administration

The combined effects of probiotics (Lactobacillus acidophilus, Lactobacillus casei, Streptococcus faecium, and Saccharomyces cerevisiae) and organic acids (sorbic and citric acid) on intestinal morphology and expression of immune-related genes were investigated. One-day-old chicks were randomly assigned to 1 of 3 groups: birds not receiving probiotic or organic acids (control; T1), or birds receiving an oral combination (1 g/L in water) of 10(8) CFU/g of each of the aforementioned probiotics and organic acids (1% sorbic acid and 0.2% citric acid) for 7 (T2) or 14 d (T3). Each group was divided into 5 replicate pens of 20 birds each, and 5 birds from each group (1 from each pen) were killed on d 11 and 22. Intestinal sections were collected for histological assessment, and reverse transcriptase-PCR analysis was used to assess defensin and cathelicidins expression. Quantitative real-time PCR was used to assess toll-like receptors (TLR) and cytokine expression. Duodenal villus height was greater in T2 and T3 at d 11 (P ≤ 0.036) and 22 (P ≤ 0.015) compared with T1. At d 11, duodenal goblet cell/unit area was less in T3, whereas it was greater in T2 compared with T1 in the jejunum (P = 0.009). Ileal goblet cell/unit area was greater in T3 at d 22 compared with T1 (P < 0.001). Avian beta-defensin-3 was expressed in all tissues except the bursa of T3 birds at d 11, and TLR-2 was down regulated in the cecal tonsil of birds in T2 and T3 at d 11 compared with T1 (P = 0.020 and 0.003, respectively). Expression of IL-12p35 in the ileum at d 11 was down regulated in T2 and T3 compared with T1 (P = 0.030 and 0.012, respectively). Reduced expression of INF-γ was observed in the ileum in T3 compared with T1 at d 11 (P = 0.047). Ileal IL-6 and IL-10 and cecal tonsil interferon-gamma (INF-γ) expressions were greater T2 at d 22 (P ≤ 0.047) than T1. In conclusion, supplementation of combined probiotics and organic acids resulted in inconsistent gut morphology associated responses, and avian beta-defensins and cathelicidins expression were not associated with combined probiotics and organic acids supplementation. Birds supplemented with combined probiotics and organic acids for 7 d showing similar responses in TLR-2, IL-12p35, and IFN-γ compared with those supplemented for 14 d indicates that shorter periods of supplementation might be enough to elicit beneficial responses.

Feed intake, growth and carcass parameters of swine consuming diets containing low levels of deoxynivalenol from naturally contaminated barley

The ubiquitous nature of deoxynivalenol (DON) in the eastern prairie region of Canada necessitates the development of strategies to enhance the utilization of affected grains by swine producers. To this end, an experiment was designed to determined the impact of low levels of DON on feed intake and growth of swine. 144 Cotswold pigs (initial weight = 23.4 kg ± 0.3 SE) were assigned to receive diets containing either 0, 1 or 2 ppm DON in the final feed (four pens, each containing six barrows and six gilts, per treatment). The final DON contents of the diets were derived by diluting DON-contaminated barley (DON = 4.9 ppm) with DON-free barley. Diets were formulated to provide a minimum of 13.4 MJ kg-1 digestible energy (DE) and 0.81% total lysine, and the same diets were used throughout the grow-finish period. Feed intake (per pen basis; kg d-1), body weight gains (kg d-1) and feed conversion were measured on a weekly basis. Pigs were slaughtered at approximately 110 kg and indices of carcass merit collecte...

Developing rainfall- and temperature-based models to describe infection of canola under field conditions caused by pycnidiospores of Leptosphaeria maculans.

Blackleg, also known as Phoma stem canker, caused by Leptosphaeria maculans (Phoma lingam), is one of the most serious diseases of canola worldwide. In this study, the mean disease severity (Ds) and incidence (Di) of canola cv. Westar plants infected at the cotyledon, three-leaf, and six-leaf stages by pycnidiospores of L. maculans were monitored in the greenhouse after infection of the plants under field conditions in two successive years and associated with meteorological data during infection time. Pearsons correlation coefficient showed that total rainfall per week (R) was significantly correlated to Ds on plants infected at the cotyledon, three-leaf, and six-leaf stages, and average maximum temperature per week (Tmax) only showed significant correlation with plants infected at the cotyledon and six-leaf stages. These results also indicated that there is correlation between Di and R for plants infected at all three growth stages. A nonlinear model was developed to evaluate the combined effects of R and Tmax on Ds. The best model comprised monomolecular function and beta probability density function for plants infected at the above three growth stages. Parameters, including maximum potential for Ds at a given rainfall (d(max)), rate of changes with respect to rainfall (k), constant of integration (B), maximum potential for Ds with respect to Tmax (e), rate of increase with increasing Tmax to optimum (n), and rate of decrease as Tmax increased and passed the optimum Tmax (p), were estimated for plants infected at the above three growth stages. The effect of plant growth stage was characterized by differences in the upper limit parameter a. This parameter was greater for the plants infected at the cotyledon stage than for plants infected at the other two stages. The estimate of parameter k was the same for the plants infected at the cotyledon and three-leaf stages. This parameter was much lower for the plants infected at the six-leaf stage compared with two other stages. The logistic model could describe the disease incidence with respect to R slightly better than the other two models in the plants infected at all three growth stages. Based on the model, upper-limit estimate (d(max)) was approximately 100, 94.4, and 88.8% in the plants infected at cotyledon, three-leaf, and six-leaf stages, respectively. Di increased until rainfall reached approximately 18, 10, and 13 mm/week and became constant in the plants at cotyledon, three-leaf, and six-leaf stages, respectively. Effects of plant growth stage on the rate of change with respect to R (parameter k) were lower in the plants infected at cotyledon than at the other two stages. The accuracy of the nonlinear models suggests that they could be used to develop a comprehensive model to evaluate epidemics of blackleg based on pycnidiospores as sources of inoculum. However, additional years of data collection should improve model fit and evaluation of introduced models and contribute to the development of a more robust predictive model.

Comparison of disease severity and incidence at different growth stages of naturally infected canola plants under field conditions by pycnidiospores of Phoma lingam as a main source of inoculum

Abstract Phoma stem canker, caused by Leptosphaeria maculans, is the most destructive disease of canola (Brassica napus) in the world. A study was conducted to compare mean disease severity and incidence at three different growth stages on naturally infected canola plants under field conditions. To determine the main source of inoculum over two consecutive years in Manitoba, three different approaches were employed: inspection of infested stubble pieces for the presence of pseudothecia and/or pycnidia, detection of ascospores using Burkard and rotorod spore samplers, and lastly, utilizing trap plants to study subsequent disease development. The results showed that the mean disease severity was significantly higher (P < 0.001) on plants infected at 1, 0 (cotyledon) than at 1, 3 (3-leaf) but no significant difference in disease incidence was observed between these two stages. However, these plants showed significantly (P < 0.01) higher disease severity and incidence than plants infected at 1, 6 (6-leaf) stage. A high density of pycnidia and low density of pseudothecia on stubble pieces, absence of ascospores in most weeks and high levels of disease incidence and disease severity on infected plants suggested that pycnidiospores can be considered as a main source of inoculum during these two years in Western Canada. These findings can be used to better understand the relationship between pycnidiospore inoculum and subsequent disease development on canola under field conditions.