No abstract

The effects of pretreating wheat straw with alkali on the efficacy of exogenous fibrolytic enzymes for improving straw digestibility were studied in vitro, in situ, and in vivo. In Exp. 1, untreated straw (US); alkali-treated (5% NaOH, wt/wt) straw (AS); and autoclaved, alkali-treated straw (AAS) were sprayed with 0 or 1.5 mg/g DM of enzyme mix (xylanase, beta-glucanase, carboxymethylcellulase, and amylase) and incubated for 30 h in buffered ruminal fluid (3 x 2 factorial arrangement). Enzymes increased (P < 0.001) gas production and the incorporation of 15N into microbial N at 4 h, more so with AS or AAS than with US (P < 0.001 for gas; P < 0.05 for 15N). In Exp. 2, US and AS were sprayed with enzymes at 0, 0.15, or 1.5 mg/g DM (2 x 3 factorial) and incubated ruminally in nylon bags for up to 80 h to determine the in situ DM disappearance (ISDMD). Interactive effects (P < 0.05) of pretreatment and enzymes were observed on all ruminal degradation parameters. Alkali increased the rate (P < 0.01) and extent (P < 0.001) of ISDMD irrespective of enzymes. Enzymes applied to US did not affect the extent of ISDMD, but they increased (P < 0.01) the extent of ISDMD when applied to AS. Substrates from Exp. 1 and 2 were incubated in acetate buffer for 24 h to measure the hydrolytic loss of DM and release of reducing sugars and phenolic compounds. Alkali pretreatment and enzymes each increased (P < 0.001) DM loss and the release of reducing sugars and, in combination, exerted synergistic effects (P < 0.001). Enzymes did not affect the release of phenolic compounds from the straw. In Exp. 3, total-tract digestibility of untreated and enzyme-treated (100 mL/kg DM) ammoniated straw was assessed using 32 beef cows in eight pens. Wrapped straw bales were injected with NH3 (3% [wt/wt], DM basis) 4 mo before the study; enzymes were applied immediately before feeding. Applying enzyme to ammoniated straw increased (P < 0.05) digestibilities of DM, OM, and total N but did not affect the intake of DM or digestibility of ADF. Pretreatment of straw with alkali enhanced the efficacy of exogenous enzymes, presumably by breaking esterified bonds and releasing phenolic compounds and/or by swelling the crystalline cellulose and enhancing enzyme penetration. Including enzymes that mimic alkali hydrolysis (e.g., esterases) in commercial feed additives could substantially improve the value of these products for ruminants.

Extending grazing into the winter, as opposed to feeding of harvested forages, can increase the sustainability of ranching in the western US. This study was conducted to determine the economic value of grazing stockpiled forage kochia (Kochia prostrata [L.] Scrad.) and crested wheatgrass (Agropyron desertorum [Fisch. Ex Link] Schultes) during the fall and winter. Changes in cow body weight, body condition score, and ultrasound backfat were compared for late-gestation cows grazing forage kochiacrested wheatgrass pastures vs. those fed alfalfa (Medicago sativa L.) hay in drylot. The study was conducted from early November to late January for 2 consecutive years near Promontory, Utah. Forage availability and nutritional quality were monitored throughout the experiment. Cows grazing stockpiled forages did not receive any protein or energy supplements. Forage kochia comprised approximately 70% of available forage, with November crude protein content of 116 and 76 g kg À1 in years 1 and 2, respectively. Nutritional quality declined throughout the season, presumably mostly because of removal of higher-quality forage by preferential grazing as opposed to weathering. Averaged over years, cows grazing forage kochia-grass gained body weight (19 kg), increased in body condition (0.3 points), and maintained backfat thickness, finishing well within the range considered optimum for onset of calving and return to estrus. Pasture-vs. drylot-fed cows did not differ with regard to changes in body weight or body condition score. Both treatments increased backfat in year 1, when initial backfat was less than 0.5 cm, but both treatments resulted in loss of backfat in year 2, when initial backfat was greater than 1.0 cm. Grazing was more economical, costing $0.24 cow À1 d À1 less than feeding alfalfa hay in drylot. Forage kochia can be used on western rangelands to extend grazing into the fall and winter, thereby improving the profitability of beef production. ResumenExtender el apacentamiento hasta el invierno, como estrategia opuesta a la alimentació n con forrajes cultivados, puede incrementar la sostenibilidad de las operaciones ganaderas del oeste de Estados Unidos. Este estudio se condujo para determinar el valor econó mico de apacentar forraje acumulado en pie de ''Kochia'' (Kochia prostrata [L.] Scrad.) y ''crested wheatgrass'' (Agropyron desertorum [Fisch. Ex Link] Schultes) durante el otoñ o e invierno. Cambios en el peso corporal, la condició n corporal y grasa del lomo medida con ultrasonido fueron comparados entre vacas en estado final de gestació n apacentando praderas de ''Kochia''-''Crested wheatgrass'' versus vacas alimentadas en corral con heno de ''Alfalfa'' (Medicago sativa L.). El estudio se llevo a cabo cerca de Promontory, Utah de inicios de Noviembre a fines de Enero durante dos añ os consecutivos. La disponibilidad de forraje y la calidad nutricional fueron monitoreadas a lo largo del experimento. Las vacas apacentando los forrajes acumulados en pie no recibieron ningú n suplemento ni proteico ni energ...

. 1999. Sorting feeder cattle with a system that integrates ultrasound backfat and marbling estimates with a model that maximizes feedlot profitability in value-based marketing. Can. J. Anim. Sci. 79: 327-334. Studies were conducted to evaluate a feeder cattle sorting system for tracking future carcass merit. The Kansas State University (KSU) sorting system combines initial body weight, ultrasound backfat thickness and marbling score with economic data to project the number of days on feed that will maximize profitability. The KSU sorting system was applied, 3 to 4 mo before slaughter, on 4101 yearling steers at two large feedlots located in southern Alberta. In Feedlot 1, steers averaging 408.7 kg (SD = 45.2 kg) were randomly assigned to two treatment groups: sorted by weight (control; n = 856) and sorted by the KSU sorting system (n = 849). In Feedlot 2, steers averaging 494.4 kg (SD = 42.3 kg) were randomly assigned to two treatment groups: not sorted (control; n = 798) and sorted by the KSU sorting system (n = 1598). Whole pens were marketed when the majority of steers in the pen approached the carcass weight and grade characteristics required for optimal return. The KSU sorted steers gained 0.12 kg d -1 faster at Feedlot 1 (P = 0.043) and 0.05 kg d -1 faster at Feedlot 2 (P = 0.036) than control steers. Feed intake, feed efficiency, death loss, warm carcass weight, backfat thickness, l. dorsi area, marbling score and lean meat yield were similar between sorting systems regardless of feedlot. The KSU sorting system reduced dark cutting (B4) carcasses to zero (0.0% KSU vs. 1.3% Control; P = 0.005) and increased AAA quality grade carcasses by 40.8% (31.4% KSU vs. 22.3% Control; P = 0.001) in Feedlot 1. In Feedlot 2, the KSU sorting system reduced over-fat carcasses (Y3) by 47.4% (10.2% KSU vs. 19.4% Control; P = 0.001) and increased AA carcasses by 14.7% (52.3% KSU vs. 45.6% Control; P = 0.003). These changes resulted in the KSU sorted steers being more profitable than control steers by $27.67 head -1 in Feedlot 1 and $15.22 head -1 in Feedlot 2. The increased net return was primarily due to improved weight gains and a more desirable distribution of carcass yield and quality grades. Nous avons évalué un système de triage des bovins d'engrais quant à son aptitude à prédire la qualité des carcasses. Le système de tri mis au point à l'Université de l'État du Kansas (KSU) allie le poids corporel initial, le poids corporel de départ, l'épaisseur du gras dorsal mesurée par ultrasons et l'indice de persillé aux données économiques, pour prédire le nombre de jours d'engraissement qui maximisera la rentabilité. Le système KSU a été appliqué, 3 à 4 mois avant l'abattage, à 4101 bouvillons d'un an répartis sur deux grands parcs d'engraissement situés dans le sud de l'Alberta. Au parc 1, des bouvillons, d'un poids corporel moyen de 408,7 kg (ET=45,2 kg), étaient répartis au hasard entre deux traitements de triage, l'un au poids (témoin, n = 856), l'autre par le système de tri KSU (n=849). Au parc 2, les bouvillons de 494,...

Well‐managed irrigated pasture production can be optimized without nitrogen (N) fertilizer. The objective was to determine mixture and planting ratios of tall fescue (Schedonorus arundinacea Schreb.) (TF), meadow brome (Bromus riparius Rehm.) (MB), orchardgrass (Dactylis glomerata L.) (OG), timothy (Phleum pratense L.) (TIM), and perennial ryegrass (Lolium perenne L.) (PRG) with alfalfa (Medicago sativa L.) (ALF), birdsfoot trefoil (Lotus corniculatus L.) (BFTF), or cicer milkvetch (Astragalus cicer L.) (CMV) that maximize productivity. Planting ratios were 0:100 (grass:legume), 25:75, 50:50, 75:25, and three 100:0 grass monocultures fertilized at 0, 67, and 134 kg N ha−1. Seasonal production of TF–ALF was 12.69 Mg ha−1, equal to TF fertilized at 134 kg N ha−1. ALF mixtures with MB, OG, TIM, and PRG produced 12.57, 10.97, 11.77, and 10.74 Mg ha−1, respectively, and 8 to 40% more than grasses receiving 134 kg N ha−1. Production of BFTF mixtures with TF, MB, and OG were 11.69, 11.45, and 9.95 Mg ha−1, respectively, equal to their respective grass monoculture receiving 134 kg N ha−1. The BFTF–TIM and BFTF–PRG mixtures averaged 12% more forage than grass monocultures receiving 134 kg N ha−1. Production of CMV‐grass was similar to that of grasses receiving 67 kg N ha−1. Seasonal forage distribution was more uniform in ALF– and BFTF–grass mixtures, averaging 30% more at the second and third harvests than fertilized grasses. The TF and MB legume mixtures averaged 7% more production in the 50:50 planting ratios than the other two grass–legume mixtures, while the 50:50 and 25:75 ratios of OG and TIM–legume mixtures averaged 12% more than the 75:25 and the 25:75 PRG–legume planting ratio averaged 9% more than the 50:50 and 75:25. Forage production of grass–legume mixtures can equal or exceed fertilized grass monocultures and with more uniform distribution over the growing season.