Fourteen mature, nonpregnant, nonlactating Angus cows (498 kg) were individually fed through two consecutive phases (maintenance [M], 80 d and ad libitum [A], 70 to 79 d) to estimate within-herd variation in individual cow ME requirements for maintenance (MEm) and to identify factors contributing to this variation. Body composition was determined at initiation of phase M, at termination of phase M (also initiation of phase A) and at the end of phase A by a two-pool D2O dilution technique. Daily MEm averaged 156.7 kcal/kg BW.75 (SD = 18.4 kcal/kg BW.75) and efficiency of ME use for tissue gain or loss averaged 76% (SD = 30%). Estimates of ME intake to maintain 1 kg of protein or 1 kg of fat were 192.9 (SE = 24.8) or 20.7 (SE = 21.5) kcal. These data indicate that among cows of similar fat masses, those with larger protein masses had higher energy requirements for maintenance. Daily MEm was positively correlated (P less than .16) with liver weight (r = .40) and relative proportions of liver (r = .44; P less than .16) and heart (r = .48; P less than .10) in the empty body. Also, daily MEm was correlated negatively (P less than .05) with weight (r = -.71) and relative proportion of omental and mesenteric fat (r = -.78). Estimates of ME required for deposition of 1 kcal of protein or fat were 5.56 (SE = 1.01) or 1.26 (SE = .09) kcal. Weight of liver and the sum of liver, spleen, kidney and heart weights increased 1.58 (R2 = .47) and 1.95 kg (R2 = .52) per kilogram of daily weight gain during phase A. These results indicate that increased performance caused increased organ mass (liver).

Methods of disease management used in annual grain crops, especially cultural practices designed to disrupt the disease cycle of a particular pathogen, will not necessarily be applicable to perennial grain crops. Resistance to multiple pathogens, therefore, will clearly be important in disease management. The objective of this research was to evaluate disease resistance in 10 perennial grain accessions (one to two accessions of each: perennial wheat (Thinopyrum sp. × Triticum aestivum), intermediate wheatgrass (Thinopyrum intermedium), perennial rye (Secale montanum), hexaploid triticale (Triticum turgidum × S. montanum), octoploid triticale (Triticum aestivum × S. montanum), tetraploid perennial rye (Secale cereale × S. montanum), and tall wheat-grass (Thinopyrum ponticum)) to tan spot (caused by Pyrenophora tritici-repentis), take-all (caused by Gaeumannomyces graminis var. tritici), wheat streak mosaic, and barley yellow dwarf, four important diseases of the Great Plains. Several of the grasses were resistant to tan spot, barley yellow dwarf, and wheat streak mosaic. Indeed, the wild grasses and perennial donors T. intermedium (including BFPMC1), T. ponticum, and S. montanum, in addition to Permontra, a tetraploid perennial rye, were highly resistant to all three diseases. Additionally, the remaining grasses tested were also more resistant to tan spot than the susceptible wheat control. However, none of the 10 grass accessions appeared highly resistant to take-all, and substantial losses in biomass were observed, although such effects may be moderated under field conditions due to the potential for take-all decline in perennial plantings.

A risk analysis of the economics of alternative wheat supplies to a small ethanol-beef feedlot facility was conducted, based on historical data from an 18-year period (1978-96). Alternatives simulated were Black, Dark Brown and Brown soil zone locations in Alberta growing either Hard Red Spring (HRS) wheat, Canadian Prairie Spring (CPS) wheat or irrigated Soft White (SWW) wheat to supply a 10 ML per year ethanol plant. The plant would use the coproduct of wet distillers grains in the finishing of approximately 14,000 steer calves per year. Three valuation scenarios were considered: selling ethanol at its market price, inclusion of current Alberta tax incentive levels for ethanol sale, and sale of wheat to the Canadian Wheat Board as opposed to sale to an ethanol plant. Ethanol facility and total net revenues were highest for the CPS-Dark Brown soil scenario due to its relatively high ethanol yields per tonne of feedstock, and high grain yields per hectare. An integrated feedstock-ethanol-livestock operation selling ethanol at current subsidy (tax incentives) levels will lose money approximately half to two-thirds of the time over the long run. Without subsidies, an integrated facility would lose money two-thirds to three-quarters of the time.Nous avons réalisé, à partir de données recueillies durant une période de 18 ans (1978 à 1996), une analyse de risque des aspects économiques de diverses provenances de blé pour une petite exploitation éthanol-parc d'engraissement. Les options simulées consistaient en emplacements situés dans les zones de sols noirs, brun foncé et bruns de l'Alberta, produisant soit du blé roux vitreux de printemps (BRVP), du blé de printemps des Prairies canadiennes (BPPC) ou du blé blanc tendre (BBT) sous irrigation pour alimenter un atelier d'éthanol d'un volume de fabrication de 10 millions de litres par année. L'atelier hypothétique utiliserait le co-produit des drêches de distillerie humides pour engraisser quelque 14 000 jeunes bouvillons par année. Trois scénarios de valorisation étaient envisagés : vente de l'éthanol au prix de marché, inclusion des incitatifs fiscaux actuels de l'Alberta pour la vente de l'éthanol et vente du blé à la Commission canadienne du blé par opposition à la vente à un atelier de production d'éthanol. Les revenus nets tirés de l'atelier et les revenus nets totaux les plus élevés de l'exploitation étaient obtenus dans le scénario BPPC-sol brun foncé en raison des rendements d'éthanol relativement élevés par tonne de blé et des bons rendements grainiers par hectare obtenus dans cette combinaison. Selon les résultats obtenus, un atelier intégré blé-éthanol-parc d'engraissement écoulant son éthanol au niveau de subvention actuel (incitatifs fiscaux), perdrait de l'argen d'environ la moitié aux deux tiers du temps. Sans ces subventions, il ne rentrerait dans ses dépenses qu'une fois sur trois ou une fois sur quatre seulement.

High doses of nitrogen (N) fertiliser input on permanent pastures are crucial in terms of N surplus and N losses. Quantitative analyses of the response of plant functional traits (PFT) driving crop growth rate (CGR) under low N input are lacking in frequently defoliated pastures. This study aimed to understand the significance of PFTs for productivity and N uptake in permanent grasslands by measuring dynamics in tiller density (TD), tiller weight (TW), leaf weight ratio (LWR), leaf area index (LAI), specific leaf area (SLA), as well as leaf N content per unit mass (LNCm) and per unit area (LNCa) in perennial ryegrass (Lolium perenne)-dominated pastures, in a simulated rotational grazing approach over two consecutive growing seasons. Annual N application rates were 0, 140 and 280 kg N ha−1. The phenological development of perennial ryegrass was the main driver of CGR, N uptake and most PFTs. The effect of N application rate on PFTs varied during the season. N application rate showed the greatest effect on TD, LAI and, to a lesser extent, on SLA and LNCm. The results of this study highlight the importance of TD and its role in driving CGR and N uptake in frequently defoliated permanent pastures.

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