What makes a host profitable? Parasites balance host nutritive resources against immunity

Numerous host qualities can modulate parasite fitness, and among these, host nutritive resources and immunity are of prime importance. Indeed, parasite fitness increases with the amount of nutritive resources extracted from the host body and decreases with host immune response. To maximize fitness, parasites have therefore to balance these two host components. Yet, because host nutritive resources and immunity both increase with host body condition, it is unclear whether parasites perform better on hosts in prime, intermediate, or poor condition. We investigated blood meal size and survival of the ectoparasitic louse fly Crataerina melbae in relation to body condition and cutaneous immune response of their Alpine swift (Apus melba) nestling hosts. Louse flies took a smaller blood meal and lived a shorter period of time when feeding on nestlings that were experimentally food deprived or had their cutaneous immune response boosted with methionine. Consistent with these results, louse fly survival was the highest when feeding on nonexperimental nestlings in intermediate body condition. Our findings emphasize that although hosts in poor condition had a reduced immunocompetence, parasites may have avoided them because individuals in poor condition did not provide adequate resources. These findings highlight the fact that giving host immunocompetence primary consideration can result in a biased appraisal of host-parasite interactions

Registration of ‘Bonanza’ Big Bluestem

‘Bonanza’ big bluestem (Andropogon gerardii Vitman.) (Reg. no. CV-13, PI 641701) was released in May 2004 by the USDA-ARS and the Agricultural Research Division, Institute of Agriculture and Natural Resources, University of Nebraska. It is a broadly adapted perennial warm-season grass cultivar that produces forage with high in vitro dry matter digestibility (IVDMD) and improved animal gains in comparison to its parent cultivar when utilized by beef cattle in well-managed grazing systems. Bonanza was tested as Pawnee C3

Registration of ‘Goldmine’ Big Bluestem

‘Goldmine’ big bluestem [Andropogon gerardii Vitman.] (Reg. no. CV-14, PI 641702) was released in May 2004 by the USDA-ARS and the Agricultural ResearchDivision, Institute of Agriculture and Natural Resources, University of Nebraska. Goldmine is a perennial warm-season grass cultivar that produces forage with moderately improved in vitro dry matter digestibility (IVDMD), protein concentration, and improved forage yields in some hay management systems. Animal gains from Goldmine were greater than its parent cultivar when utilized by beef cattle in well-managed grazing systems. Goldmine was tested as Kaw C3

Optimizing the use of fibrous residues in beef and dairy diets

Increased corn prices over the past decade have altered land use away from traditional forage in favor of corn. Accordingly, beef and dairy producers have had to adopt non-traditional forage resources into their production systems, many of which have become available as a result of increased corn production. Byproducts of the wet and dry milling industries have been used to replace both corn and forage in beef and dairy diets. Byproducts containing corn bran have large amounts of readily digestible hemicellulose. The use of byproducts may increase milk production, ADG, and G:F in dairy, beef growing, and beef finishing diets, respectively. In beef finishing diets, byproducts allow for use of low quality forages or partial replacement of traditional forages with minimal losses in ADG or G:F by formulating for equal NDF concentrations. Corn residues have become more available due to increases in corn acres and yield. The individual plant components (i.e., husk, leaf, stem) vary in fiber digestibility (NDF digestibility estimates = 40.5%, 31.4%, and 0.6% ± 0.8 for husk, leaf, and stalk, respectively). Selectivity for husks and leaves by grazing cattle likely improves their performance. New technologies that allow for selective harvesting of husk and leaf may result in a higher value feed product. Alkaline treatment is another technology that may improve the feeding value of residues. Concentrations of up to 20% harvested corn residue treated with calcium oxide may be included in finishing diets with an average of 2.3% reduction in G:F when diets contain 40% wet or modified distillers grains. Conversely, when untreated corn residues are included in similar finishing diets, G:F may be reduced by 20%. Calcium oxide treated residues included in beef growing diets increases DMI and ADG without significant improvements in G:F. Calcium oxide treatment of corn residues has been evaluated in dairy diets by replacing corn or corn silage with variable results. Harvesting corn silage rather than separate harvest of corn grain and residue may allow for greater total net energy per acre to be captured. The use of wet and modified corn milling byproducts enhances the use of corn silage in finishing diets. While G:F may be reduced, feeding greater concentrations of corn silage may be economical. Efficient use of non-traditional fiber sources, like corn milling by products and corn residue, are critical to the future viability of ruminant animal production

Grazing Evaluation of Big Bluestems Bred for Improved Forage Yield and Digestibility

Two big bluestem (Andropogon gerardii Vitman) strains (Pawnee C3 and Kaw C3) developed by three breeding cycles for increased forage yield and in vitro dry matter digestibility (IVDMD) were compared with the base populations of \u27Pawnee\u27 and \u27Kaw\u27 in a 3-yr grazing trial. Pastures were seeded in May 1998 near Mead, NE. Experimental units were three 0.4-ha pastures of each strain or cultivar in a randomized complete block design. Pastures were burned and fertilized with ammonium nitrate at 112 kg N ha-1 in the spring of 2000, 2001, and 2002 before grazing. Each pasture was continuously stocked with three crossbred yearling steers (Bos taurus) (380 +/- 38 kg) in mid-June 2000, 2001, and 2002 to provide a stock density of 7.5 steers ha-1. Pawnee C3 and Kaw C3 produced 16 and 7% more average daily gain (ADG), respectively, than the base populations during the 3-yr study. Additionally, Pawnee C3 and Kaw C3 produced 14 and 5% more total body weight (BW) gain ha-1, respectively, than the base populations. Pawnee C3 ADG was 1.30 kg hd-1 and produced greater than 455 kg total BW gain ha-1 during a drought period in eastern Nebraska. Pawnee C3 pastures produced more available forage with higher IVDMD, cell soluble, cell wall digestibility, and lower lignin concentration than forages from Pawnee pastures. Kaw C3 pastures differed from Kaw pastures by producing forage with greater crude protein concentration. These results demonstrate the productivity of big bluestem pastures in the eastern Great Plains and document the positive livestock response to moderate increases in forage IVDMD. The strains bred for increased yield and IVDMD provided as much as 26% more total BW gain ha-1 at no additional cost. Pawnee C3 was released as the cultivar Bonanza and Kaw C3 was released as \u27Goldmine\u27

Evaluation of Four Intermediate Wheatgrass Populations under Grazing

The grazing season in the central and northern Great Plains could be extended by use of adapted cool-season grass pastures for spring and fall grazing to augment the native warm-season range. A grazing trial was conducted to evaluate the forage quality of four intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey] populations for use in forage-livestock systems. The cultivars Slate and Oahe and two populations selected for improved IVDMD, ‘Manska’ and NE TI 1, were evaluated. Each population was seeded in the fall of 1987 in three replicated 0.4-ha pastures arranged in a randomized complete block design. Pastures were stocked with three beef yearlings for 28 d in spring 1989 and 42 d in spring 1990 to provide a stocking rate of 7.5 steers ha-’. Duration of grazing was shorter in 1989 because of inadequate soil moisture. Average daily gain (ADG) and gain per hectare were higher (P 5 0.10) in 1989 than 1990, despite the lower (P 5 0.10) forage availability and lesser number of grazing days in 1989. Steers grazing Manska in 1989 gained 1.59 kg d-’, compared with 1.42,1.27, and 1.43 for Oahe, Slate, and NE TI 1, respectively. There were no differences (P \u3e 0.10) in ADG or gain per hectare among populations in 1990. The improvement in ADG resulted in 30 to 65 kg more gain per hectare from Manska compared with the other populations in l989. These results demonstrate the excellent quality of intermediate wheatgrass for grazing livestock and the impact that modest improvements in forage quality can have on animal performance

Grazing Evaluation of Big Bluestems Bred for Improved Forage Yield and Digestibility

Two big bluestem (Andropogon gerardii Vitman) strains (Pawnee C3 and Kaw C3) developed by three breeding cycles for increased forage yield and in vitro dry matter digestibility (IVDMD) were compared with the base populations of \u27Pawnee\u27 and \u27Kaw\u27 in a 3-yr grazing trial. Pastures were seeded in May 1998 near Mead, NE. Experimental units were three 0.4-ha pastures of each strain or cultivar in a randomized complete block design. Pastures were burned and fertilized with ammonium nitrate at 112 kg N ha-1 in the spring of 2000, 2001, and 2002 before grazing. Each pasture was continuously stocked with three crossbred yearling steers (Bos taurus) (380 +/- 38 kg) in mid-June 2000, 2001, and 2002 to provide a stock density of 7.5 steers ha-1. Pawnee C3 and Kaw C3 produced 16 and 7% more average daily gain (ADG), respectively, than the base populations during the 3-yr study. Additionally, Pawnee C3 and Kaw C3 produced 14 and 5% more total body weight (BW) gain ha-1, respectively, than the base populations. Pawnee C3 ADG was 1.30 kg hd-1 and produced greater than 455 kg total BW gain ha-1 during a drought period in eastern Nebraska. Pawnee C3 pastures produced more available forage with higher IVDMD, cell soluble, cell wall digestibility, and lower lignin concentration than forages from Pawnee pastures. Kaw C3 pastures differed from Kaw pastures by producing forage with greater crude protein concentration. These results demonstrate the productivity of big bluestem pastures in the eastern Great Plains and document the positive livestock response to moderate increases in forage IVDMD. The strains bred for increased yield and IVDMD provided as much as 26% more total BW gain ha-1 at no additional cost. Pawnee C3 was released as the cultivar Bonanza and Kaw C3 was released as \u27Goldmine\u27

Evaluation of Four Intermediate Wheatgrass Populations under Grazing

The grazing season in the central and northern Great Plains could be extended by use of adapted cool-season grass pastures for spring and fall grazing to augment the native warm-season range. A grazing trial was conducted to evaluate the forage quality of four intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey] populations for use in forage-livestock systems. The cultivars Slate and Oahe and two populations selected for improved IVDMD, ‘Manska’ and NE TI 1, were evaluated. Each population was seeded in the fall of 1987 in three replicated 0.4-ha pastures arranged in a randomized complete block design. Pastures were stocked with three beef yearlings for 28 d in spring 1989 and 42 d in spring 1990 to provide a stocking rate of 7.5 steers ha-’. Duration of grazing was shorter in 1989 because of inadequate soil moisture. Average daily gain (ADG) and gain per hectare were higher (P 5 0.10) in 1989 than 1990, despite the lower (P 5 0.10) forage availability and lesser number of grazing days in 1989. Steers grazing Manska in 1989 gained 1.59 kg d-’, compared with 1.42,1.27, and 1.43 for Oahe, Slate, and NE TI 1, respectively. There were no differences (P \u3e 0.10) in ADG or gain per hectare among populations in 1990. The improvement in ADG resulted in 30 to 65 kg more gain per hectare from Manska compared with the other populations in l989. These results demonstrate the excellent quality of intermediate wheatgrass for grazing livestock and the impact that modest improvements in forage quality can have on animal performance

Carcass Traits and M. Longissimus Lumborum Palatability Attributes of Calf- and Yearling-Finished Steers

A 2-yr experiment was conducted to compare carcass characteristics and meat palatability attributes of steers (³⁄₄ British, ¹⁄₄ Continental) finished postweaning as calves or yearlings. Calves and yearlings of the same contemporary group were designated to a finishing system at weaning. Calves (n = 73) were finished in the feedlot (191 d) on a high-concentrate diet. Yearlings (n = 84) grazed crop residues after weaning, followed by spring and summer pasture grazing, and concluded with a short finishing period (91 d) in the feedlot. All steers were fed to a constant, fat thickness endpoint of 1 cm. The M. longissimus lumborum steaks from each production system were aged for 7, 14, or 21 d for Warner-Bratzler shear force determination and for 7 or 14 d for in-house sensory panel evaluation. Insoluble, percent soluble, and total collagen were determined. Yearlings produced heavier (P \u3c 0.001) carcasses with larger (P \u3c 0.001) LM areas and lower (P \u3c 0.001) marbling scores and quality grades. Calves possessed greater amounts of total collagen (P \u3c 0.001), with a significantly greater percentage of soluble collagen compared with yearlings (39.72 vs. 24.38%). Calves produced steaks with lower (P \u3c 0.001) shear force values and greater (P \u3c 0.001) sensory ratings for flavor. The USDA Choice steaks from the calves were more (P \u3c 0.001) tender and more (P \u3c 0.050) palatable than Choice steaks from yearlings, and USDA Select steaks from calves were rated more tender (P \u3c 0.001), juicy (P = 0.012), and desirable (P \u3c 0.001) than Select steaks from yearlings. As expected, increasing aging time from 7- to 14- to 21-d produced steaks with lower (P \u3c 0.001) shear force values, regardless of the production system. Risk probabilities showed 1.24% of the steaks from calf finished steers and 21.22% of steaks from yearling-finished steers to be tough. Sensory rating probabilities showed the steaks from the calves were most likely to be desirable for tenderness, whereas steaks from the yearlings were most likely to be undesirable for tenderness, juiciness, flavor, and overall acceptability. Thus, calf-finished steers produce carcasses superior in quality and palatability compared with those from yearling finished steers. However, yearling-finished steers can produce tender beef with extended aging