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Five beef cattle management regimens were evaluated for their effect on meat quality, fatty acid composition, and overall palatability of the longissimus dorsi (LD) muscle in Angus cross steers. A 98-d growing phase was conducted using grass silage with or without supplementation of growth promotants (Revalor G and Rumensin) or soybean meal. Dietary treatments in the finishing phase were developed with or without supplementation of growth promotants based on exclusive feeding of forages with no grain supplementation, or the feeding of grain:forage (70:30) diets. Growth promotants increased (P < 0.01) shear force and tended (P = 0.06) to increase toughness of the LD muscle due to limited postmortem proteolytic activity (lower myofibrillar fragmentation index value; P = 0.02). Grain feeding increased DM and intramuscular fat content (P = 0.03 and P = 0.05, respectively) in the LD but decreased the sensory panel tenderness score (P = 0.01). Growth promotants increased (P [less than or equal to] 0.05) the proportion of C18:0, C20:0, trans isomers of C18:1, and cis-9, trans-11 C18:2. Exclusive feeding of forages increased the proportion of cis-9, cis-12, cis-15 C18:3 as well as several other isomers of the n-3 family and decreased in the ratio of n-6 to n-3 fatty acids in the LD muscle as compared with supplementing grain (P < 0.05). In addition, the forage-based diet increased (P < 0.01) the concentration in the intramuscular fat of several intermediates (cis-9, trans-11, cis-15 C18:3; trans-11, cis-15 C18:2; trans-11 C18:1) of ruminal biohydrogenation. Forage feeding also increased the proportion of cis-9, trans-11 C18:2 (P < 0.01) and decreased the concentration of trans-10 C18:1 in the LD muscle (P = 0.03). It is concluded that quality demands of health-conscious consumers can be met through a forage-finishing and growth promotants-free beef production system. Key words: beef cattle, beef production system, beef quality, fatty acid, shear force, taste panel

The concentration of CLA in adipose tissue can be increased in ruminants by feeding pasture and extruded soybeans. The objective of this study was to evaluate maternal supplementation of raw (RS) or extruded (ES) soybeans on the concentrations of CLA in milk fat of cows and s.c. adipose tissue of suckling calves. Thirty-two spring-calving cows (BW 624 [+ or -] 76 kg; BCS 3.5 [+ or -] 0.4; mean [+ or -] SD) and calves (BW 127 [+ or -] 15 kg) were separated into 2 groups. Cows were distributed to have 8 calves of each sex in both groups. When animals were turned out to pasture, dams received 2 kg/d of either RS or ES. Dietary treatments had no effect on average milk intake (P = 0.22) and pasture forage intake (P = 0.13) for calves over the course of the grazing season. As a result, no effect of treatments was observed on ADG (P = 0.26). At weaning, milk fat content of CLA reached 15.4 and 24.2 mg/g of total fatty acids for cows fed RS and ES, respectively (P = 0.02). The CLA concentrations in adipose tissue were 16.9 and 25.0 mg/g of total fatty acids for calves suckling dams fed RS and ES, respectively (P < 0.001). Overall, results demonstrated supplementing grazing cows with ES increased CLA content in milk and adipose tissue of suckling calves. Key words: conjugated linoleic acid, extruded soybean, nursing beef cow, pasture, subcutaneous adipose tissue, suckling calf

Forty Angus-cross steers were used to evaluate 5 beef cattle management regimens for their effect on growth performance, carcass characteristics, and cost of production. A 98-d growing phase was incorporated using grass silage with or without growth promotants (trenbolone acetate + estradiol implants, and monensin in the feed) or soybean meal. Dietary treatments in the finishing phase were developed, with or without addition of the same growth promotants, based on exclusive feeding of forages with minimal supplementation or the feeding of barley-based diets. Overall, ADG for animals treated with growth promotants or fed supplemented diets (soybean meal and barley) was increased (P < 0.01) by 25 and 21%, respectively, compared with steers reared on grass silage alone and not treated with growth promotants. Except for HCW (P < 0.01), the use of growth promotants did not affect carcass measurements. Increasing the proportion of barley in the diet of steers finished on forage produced a heavier HCW (P < 0.01) and a greater (P < 0.01) quality grade. Because of their lower HCW and quality grade, cattle targeted to a forage-fed, nonimplanted beef market would need to garner a 16% premium to be economically competitive with cattle finished conventionally. Key words: beef production system, feedlot performance, forage finishing, production cost

Copyright of Canadian Journal of Animal Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Animal Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Forage brassicas, such as summer turnip (ST; Brassica rapa) and forage rape (FR; Brassica napus), are used as supplementary crops during summer. However, studies with lactating dairy cows fed these forages are limited and report inconsistent productive responses. The aim of this study was to determine dry matter intake, rumen fermentation and milk production responses of dairy cows in mid-lactation supplemented with and without summer ('ST' or 'FR') brassicas. Twelve multiparous lactating dairy cows were randomly allocated to three dietary treatments in a replicated 3 × 3 Latin square design balanced for residual effects over three 21-day periods. The control diet consisted of 16.2 kg DM of grass silage, 2.25 kg DM of commercial concentrate and 2.25 kg DM solvent-extracted soybean meal. For the other two dietary treatments, 25% of the amounts of silage and concentrates were replaced with FR or ST. The inclusion of forage brassicas had no effects on milk production (24.2 kg cow/day average) and composition (average milk fat and protein 43.2 and 33.6 g/l, respectively). Dry matter intake was 0.98 kg and 1.12 kg lower for cows supplemented with FR and ST, respectively, resulting in a greater feed conversion efficiency (1.35 kg milk/kg DM for ST and FR v. 1.27 kg milk/kg DM for the control diet). Intraruminal pH was lower for cows supplemented with ST compared to the control diet; however, it did not decrease below pH 5.8 at any time of the day. After feeding, the concentrations of total short-chain fatty acids (SCFAs) in rumen contents increased with ST supplementation compared to the control diet. Inclusion of FR in the diet increased the molar proportion of acetate (68.5 mmol/100 mmol) in total SCFA at the expense of propionate, measured 6 h after feeding of the forage. The molar proportion of butyric acid was greater with ST and FR supplementation (13.1 and 12 mmol/100 mmol, respectively) than in control cows. The estimated microbial nitrogen (N) flow was 89.1 g/day greater when supplementing FR compared to the control diet. Based on the haematological measures, the inclusion of summer brassica forages did not affect the health status of the animals. These results indicate that mid-lactation dairy cows fed brassicas are able to maintain production despite the reduced intake, probably due to improved rumen fermentation and therefore nutrient utilization. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Animal Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Microbial protein synthesis in the rumen would be optimized when dietary carbohydrates and proteins have synchronized rates and extent of degradation. The aim of this study was to evaluate the effect of varying ruminal degradation rate of energy and nitrogen sources on intake, nitrogen balance, microbial protein yield, and kinetics of nutrients in the rumen of growing kids. Eight Boer goats (38.2 ± 3.0 kg) were used. The treatments were arranged in a split-plot Latin square design with grain sources (barley or corn) forming the main plots (squares). Grain processing methods and levels of protein degradability formed the subplots in a 2 2 factorial arrangement for a total of 8 dietary treatments. The grain processing method was rolling for barley and cracking for corn. Levels of protein degradability were obtained by feeding untreated soybean meal (SBM) or heat-treated soybean meal (HSBM). Each experimental period lasted 21 d, consisting of a 10-d adaptation period, a 7-d digestibility determination period, and a 4-d rumen evacuation and sampling period. Kids fed with corn had higher purine derivatives (PD) excretion when coupled with SBM compared with HSBM and the opposite occurred with barley-fed kids (P = 0.01). Unprocessed grain offered with SBM led to higher PD excretion than with HSBM whereas protein degradability had no effect when processed grain was fed (P = 0.03). Results of the current experiment with high-concentrate diets showed that microbial N synthesis could be maximized in goat kids by combining slowly fermented grains (corn or unprocessed grains) with a highly degradable protein supplement (SBM). With barley, a more rapidly fermented grain, a greater microbial N synthesis was observed when supplementing a low-degradable protein (HSBM). [ABSTRACT FROM AUTHOR]

The ecology and management of boreal forest ecosystems are drawing greater attention worldwide as their importance is being increasingly recognized for carbon sequestration or for harbouring the world's largest remaining intact forests. Selection cuts have been introduced as a more socially acceptable silvicultural method to improve the maintenance of habitat structure and functions as they mimic aspects of boreal forest succession dynamics. Many studies have shown that selection cutting helps maintaining arthropod communities in mature forests, but few have examined the increased risks of damage by bark- and wood-boring insects in boreal forests of eastern North America. We used multidirectional flight-interception traps to quantify the response of these beetles to 25 and 40% selection cutting in a balsam fir-white birch forest of Québec, Canada. The abundance and species number of both cerambycid and scolytid beetles were 5-6 times larger in selectively cut stands than in controls the year following treatments. Analyses revealed that bark- and wood-boring beetles' response was mostly associated with increased canopy openness in selectively cut stands (and sun-exposed locations within them) and residual tree injuries caused by harvesting operations. These conditions attracted beetles such as Trypodendron lineatum (Scolytinae) and Rhagium inquisitor (Cerambycidae), two species known for their ability to attack weakened, dying and dead hosts. Most species were more abundant in selection cuts, except for Evodinus m. monticola (Cerambycidae) whose abundance was strongly reduced after treatment. Some beetles can have detrimental effects on residual trees and thus could reduce timber value, but most species found in treated stands do not represent a high risk for healthy trees. Thus, selection cuts do not seem favourable to the establishment of tree-killing beetles. However, as they were found more active/abundant after selection cutting, it would be wise to further study their population dynamics over mid- and long-term periods, along with the ecological and economic implications associated with this silvicultural treatment. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Animal Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Animal Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Animal Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Permanent pastures have been shown to produce similar herbage masses and nutrient contents to perennial ryegrass pastures. To the best of our knowledge, little research has been conducted on the ruminal fermentation of permanent pastures. Our objective was to evaluate the effect of botanical composition of four perennial pastures during a growing season in the south of Chile [winter, September 2010 'S1'; spring, November 2010 'S2'; and summer, January 2011 'S3']: on in vitro fermentation products using a batch culture system. The perennial pastures studied included: permanent (PP), permanent fertilised (PFP) and renovated pastures (Lolium perenne and Trifolium repens pasture 'RGWC'; Bromus valdivianus, Dactylis glomerata, Holcus lanatus, L. perenne and T. repens 'MIXED'). There were strong interactions between pasture type and regrowth period for true organic matter, nitrogen (N) and neutral detergent fibre digestibility; total gas and volatile fatty acid (VFA) production; ammonia and microbial N. In general, all pasture treatments showed a high true organic matter digestibility (>800 g/kg), and tended to decrease in S3. In vitro fermentation of PFP and RGWC produced the highest total VFA concentration during S1 and S2, and no differences among pastures were observed in summer. Propionate proportion of total VFA was affected by pasture type and regrowth period, being higher for RGWC and S1, respectively. In vitro microbial N was higher for MIXED in S1, and PFP in S2 and S3. No pasture and regrowth period effects were observed for methane production and its proportion of total gas production. These results indicate that the in vitro fermentation products of a permanent fertilised pasture reach similar levels to those obtained from a sown pasture, and thus may be considered as a sustainable alternative for grazing livestock systems. Perennial ryegrass is the most common species used for grazing dairy systems; however, well managed permanent fertilised pastures may represent a more economical and sustainable alternative. An in vitro trial was carried out in order to assess in vitro fermentation of permanent pastures. Nutrient digestibility, ruminal fermentation products and microbial protein synthesis of well managed permanent pastures were similar to perennial ryegrass. [ABSTRACT FROM AUTHOR]

Maceration and evening-cutting are 2 forage management techniques that have independently improved forage quality and nutrient utilization in ruminants, but have not been evaluated in combination. Using a dual-flow continuous culture fermenter system, this preliminary study was designed to evaluate the individual and combined effects of time of cutting and maceration on in vitro ruminai digestion, nutrient flows, and microbial protein synthesis. Forages were harvested as hay from a timothy (Phleum pratense L.)-birdsfoot trefoil (Lotus corniculatus L.) stand in the morning (AM) or evening (PM). Half of each morning- and evening-cut treatment was macerated (AM-M, PM-M). The chemical composition (DM, OM, CP, NDF, ADF), including nonstructural carbohydrates (NSC) and water-soluble carbohydrates (WSC), was detennined for each of the 4 treatments (AM, AM-M, PM, PM-M). Forages were ground to 2 mm and allocated to separate fermenters at 60 g of DM/d in a 4 x 4 Latin square design. Fermenters were operated over four 10-d periods with the first 7 d for adaptation followed by 3 d of sampling. Evening-cutting enhanced the apparent digestibility of NDF (P = 0.02) and ADF (P = 0.006), with a tendency (P < 0.10) for improved true DM digestibility and microbial protein synthesis. Molar proportions of individual VFA were not affected (P >0.10) by time of cutting, though evening-cutting increased (P = 0.02) total concentration of VTA. Maceration had no effect (P > 0.10) on true nutrient digestibility or microbial protein synthesis. An interaction of time of cutting and maceration (P < 0.05) was observed whereby maceration decreased trae DM and OM digestibilities in evening-cut treatments, but had no effect in morning-cut treatments. Similarly, maceration reduced total N supply (P < 0.001 ) and molar proportions of acetate (P = 0.04) and increased molar proportions of propionate (P = 0.01) in evening-cut treatments with no effect on morning-cut treatments. These results indicate that independent use of evening cutting increased fiber digestibility and total VFA concentration, and independent use of maceration shifted molar proportions of VFA toward glucogenic fennentation. The combined use of these management techniques afforded no improvement for in vitro digestibility or metabolism when applied to morning-cut hay, and decreased nutrient digestibility when applied to evening-cut hay. Due to inherent limitations of in vitro systems, the results of this study should be interpreted with caution. Further in vivo studies are needed to support our conclusions. [ABSTRACT FROM AUTHOR]

Two studies were conducted to determine the effects of dietary iodine and teat-dipping practices on iodine concentrations in milk. In the first study, 63 cows in mid lactation were assigned to a 3 x 3 factorial design in which the main effects were dietary iodine levels (0.3, 0.6, and 0.9 mg of dietary I/kg of dry matter) and 3 different postdip managements (chlorhexidine with dip cup, 1% iodine dip cup, and 1% iodine by manual spray). During the 13-d pre-experimental period and the 15-d experimental period, noniodized sanitizers were used in premilking management. During the pre-experimental period, the levels of milk iodine averaged 241.2 ± 5.8 µg/kg, and no relationship was found with lactation number, days in milk, or milk production. Milk iodine concentrations increased linearly with iodine intake. Although teat dipping with 1% iodine had no effect on milk iodine concentration, the same solution applied by spraying greatly increased milk iodine levels. The second study was conducted to determine the effects of udder preparation before milking on milk iodine concentrations. Thirty-two lactating cows were assigned to 4 treatments: no predip (Con); predip with a predip solution containing 0.5% iodine + complete cleaning (Comp); predip with a postdip solution containing 1% iodine + complete cleaning (Post); and predip with a predip solution containing 0.5% iodine + incomplete cleaning (Inc). During the 14-d pre-experimental period and the 19-d experimental period, cows were fed the same diet, and noniodized sanitizers were used for postmilking dipping. During the last week of treatment, milk iodine averaged 164, 189, 218, and 252 ± 9.8 µg/kg for Con, Comp, Post, and Inc, respectively. Preplanned orthogonal contrasts indicated that predipping with a 0.5% iodine predip solution completely wiped off (Comp) tended to increase milk iodine content above that of the control and that the iodine content of Post and Inc were higher than that of the Comp treatment. The results of the first experiment confirm that, to preserve milk safety, iodine should not be fed above requirements. Spraying iodine-based teat-dipping solutions results in large increases in milk iodine content and should be avoided. Predipping teats with an iodine-based sanitizer is an acceptable practice, but must be performed with the appropriate product and completely wiped off before milking. [ABSTRACT FROM AUTHOR]

Forages have a low fermentable energy content. To use the non-protein nitrogen in forages efficiently, microbes in the rumen need a readily available energy source. Increasing the energy content in forages has been the focus of our research. Our objectives were to 1) Develop crop management practices that promote energy accumulation in forages; 2) Assess the impact of high-sugar-content forage on the in vitro synthesis of microbial proteins, and on ingestion, nitrogen utilization efficiency, and dairy cow performance. The principal findings of this research are presented. We demonstrated that the choice of forage species and late-afternoon mowing into wide swaths are potential ways to increase the sugar content in forages. This increase in the sugar content of forages results in an increase in the synthesis of microbial protein measured in vitro and, in most cases, results in an increase in ruminal propionate. High sugar content in forage is also associated with an increase as high as 5% in feed intake and milk production when cows are fed mainly higher-sugar-content forages. [ABSTRACT FROM AUTHOR]

Abstract: Thirty-nine steers were distributed into a 2×2 factorial arrangement of treatments to determine the effect of corn grain particle size (cracked [CC] vs ground [GC] corn) and soybean meal treatment (solvent extracted soybean meal [SS] vs lignosulfonate treated soybean meal Soypass™ [SP]) on carcass and meat quality traits. When CC diet was supplemented with SS carcass quality grade score tended to decrease (P =0.09). GC had no effect on meat quality, while SP only increased the intramuscular fat content when added to CC (P =0.01). The CC diet supplemented with SP increased the proportion of saturated fatty acids (P =0.01). Despite the positive effects on carcass quality, the lack of improvement in meat quality and the more saturated fatty acid profile would not justify the use of processed corn or treated soybean meal in the finishing diet of steers. [Copyright &y& Elsevier]

The effect of the method of conservation of forage on endogenous N (EN) secretion was studied using a 15N isotope dilution technique in 4 lactating Holstein cows selected from a replicated 3 × 3 Latin square. Cows were equipped with ruminal, duodenal (n = 4), and ileal (n = 2) cannulas. Diets comprised 44% concentrate plus first-cut timothy conserved either as hay or as restrictively (formic) or extensively (inoc) fermented silage. Crude protein contents of hay, formic, and inoc averaged 10.4, 13.6, and 14.8%, respectively. Total EN flow and free EN at the duodenum were increased with hay compared with silages but were similar when expressed as proportion of duodenal N flow, with total EN flow averaging 25.8, 23.9, and 23.9% for hay, formic, and inoc, respectively, and free EN at the duodenum averaging 11.5, 9.8, and 9.7% for hay, formic, and inoc, respectively. Flow of bacterial N at the duodenum originating from an endogenous source tended to be higher with inoc compared with formic. Overall, the proportion of bacterial N derived from endogenous sources and urea was similar between treatments, averaging 23 and 15%, respectively. In the feces, flow of EN was similar across treatments and averaged 31% of total fecal N. More than 70% of fecal EN originated from undigested secretions into the forestomach. Absorption of N from the forestomach tended to increase for silages compared with hay. In conclusion, EN represented an important fraction of N flowing at the duodenum and in the feces. The free EN and the total EN at the duodenum were altered by the different methods of forage conservation studied. Estimation of true dietary N supply and requirements of the dairy cow should allow for endogenous N flows and losses. [ABSTRACT FROM AUTHOR]

A study was conducted to determine the iodine concentration in milk and the relationship between that concentration and milking and feeding management practices. Milk samples were collected from the bulk tanks of 501 farms in all provinces of Canada. With a view to obtaining further information about farm management, a questionnaire was completed at each of the selected farms. Total iodine concentration (organic and inorganic) in the milk was determined using inductively coupled plasma mass spectrometry. The farms were grouped for each of the variables and, based on significant differences in iodine concentrations, 15 variables were selected for further analysis. A general linear model was fitted, with milk iodine as the response variable to main and two-way interaction effects. The mean iodine concentration in Canadian milk was 304 ± 8.4 µg/kg, with concentrations ranging from 54 to 1,902 µg/kg. Analysis of the questionnaire data suggested that component feeding was associated with lower iodine levels in milk than the levels obtained with total mixed rations. Neither the use of mineral supplementation nor the form of supplementation affected iodine levels in milk. Washing and dipping the teats before milking affected iodine in milk. The method of application of the teat sanitizers appears to be important, given that spray applications (in-line or hand spraying) were associated with higher levels than those observed with the dip-cup procedure. In conclusion, Canadian milk iodine concentration varies considerably and appears to be influenced by feeding and milking practices. [ABSTRACT FROM AUTHOR]

This study aims at investigating syllabic processes in deaf readers (n=35) who were compared to readers of French as a second language (n=23) and to expert readers (n=40). Two experimental tasks varying in their degree of phonological awareness were created: one awareness– task and one awareness+ task. Results show that all participants have knowledge related to some syllabic structures of written French. However, that knowledge is more evident in the awareness– task than in the awareness+ task. The difference between results on both tasks is greater in the deaf group than in second-language readers or the expert readers. These results are discussed in terms of complementarity of syllabic processes in reading and in relation to the status of French for deaf readers. [ABSTRACT FROM AUTHOR]

Insufficient readily fermentable energy combined with extensive degradation of proteins in alfalfa (Medicago sativa L.) may result in poor forage N utilization by ruminants. Using the inherent genetic variability and differences between harvests, our objective was to compare the effect of contrasting concentrations of nonstructural carbohydrates (NSC) in alfalfa on rumen fermentation and microbial protein synthesis. Individual genotypes of the alfalfa cultivar AC Caribou grown near Québec City, Québec, Canada, were harvested at the vegetative and early flowering stages, dried at 55°C, ground, and analyzed for soluble carbohydrates (fructose + sucrose + glucose + pinitol) and starch. Approximately 20 genotypes having, respectively, the highest and lowest NSC concentrations were pooled to constitute 2 contrasted 1-kg forage samples. Samples of high- (17.9% DM) and low- (7.4% DM) NSC alfalfa were respectively allocated to separate dual-flow fermenters in a completely randomized design with 3 replications. Rumen inoculum was obtained from 4 ruminally fistulated cows in early lactation that were fed a TMR with a 50:50 forage to concentrate ratio. A 10-d incubation period was used, with the first 6 d serving as an adaptation period followed by 4 d of sampling with solid and liquid dilution rates in the fermenters set at approximately 2.0 and 4.3%/h, respectively. High versus low NSC concentration in alfalfa significantly enhanced the apparent digestibility of OM (59.1% for high-NSC alfalfa vs. 54.4% for low-NSC alfalfa) and DM (60.0 vs. 54.3%) and the true digestibility of DM (74.1 vs. 64.7%). Increasing NSC concentration in alfalfa (high vs. low) significantly decreased ruminal pH (6.85 vs. 7.08) and NH3-N concentration (26.0 vs. 33.6 mg/ dL) and increased total VFA concentration (94.9 vs. 83.0 mM). Molar proportions of acetate, isobutyrate, and isovalerate significantly decreased, whereas molar proportions of propionate and butyrate significantly increased with high-NSC alfalfa, resulting in a more glucogenic fermentation. More importantly, microbial N flow (263 vs. 230 mg/d) and bacterial N efficiency (41.1 vs. 29.6% of available N), measured using 15N as a microbial marker, both significantly increased with the high-NSC alfalfa. These results indicate that increasing the concentration of NSC in alfalfa promotes a glucogenic fermentation and enhances microbial N synthesis in the rumen. [ABSTRACT FROM AUTHOR]

We tested the hypothesis that host tree age may act as a selective factor and lead to local adaptation of the hemlock looper (Lambdina fiscellaria), a geometrid Lepidoptera that has a wide geographical distribution and has evolved in different eco-zones characterized by different levels of floristic composition, age structure and fragmentation level. Considering that hemlock looper outbreaks mainly occurred in old forests, we compared the biological performances of two populations. The first population was collected in the northern virgin boreal forest, which is dominated by mature and overmature coniferous stands that have not suffered from human disturbance. The other population was collected in the southern mixed-wood forest, which is more diversified and has been modified by forest harvesting. Larvae were reared under controlled conditions on foliage from three age classes of balsam fir trees: juvenile, mature and overmature. Although we measured significant variations of biological performances between the two populations, no significant effect of the age of the balsam fir trees could be detected for males from both populations or for females from the southern population. However, northern females were strongly affected by the age of balsam fir trees on which they fed, as their pupal weight was 12% higher and their fecundity increased by 27% on overmature trees compared with juvenile ones. These results indicate that under the same selective pressure, females adapt their strategy to maximize their fitness, and thus they appear as the driving force of evolution through the local adaptation concept. Furthermore, the two populations evolved in distinct habitats and their adaptation reflects selective pressures occurring inside their original environment. This is the first report on local adaptation of an herbivore that is mediated by host tree age. Changes in forest age structure may have a considerable impact on insect local adaptation and presumably on their population dynamics. [ABSTRACT FROM AUTHOR]

The effect of ruminally protected Met (RPM) on splanchnic metabolism was measured in 3 primiparous and 3 multiparous Holstein cows. Doses of RPM (0, 36, and 72 g/d) were tested in a replicated 3 x 3 Latin square design, over 3 consecutive 14-d experimental periods. A mixed ration was fed in 12 equal meals per d (average dry matter intake: 17.5 ± 0.08 kg/d). Indwelling catheters were surgically implanted in the mesenteric artery and the portal and hepatic veins for blood collection, as well as in 2 distal branches of the mesenteric vein for infusion of p-aminohippurate to determine blood flow. On d 14 of each period, a temporary catheter was inserted into a mammary vein and 6 hourly blood samples were collected to determine plasma concentrations of metabolites, hormones, and their respective fluxes across the splanchnic bed and mammary glands. Yields of milk (32.8, 32.0, and 32.9 ± 0.92 kg/d) and protein (1,028, 1,053, and 1,075 ± 28.7 g/d) were unaffected by level of RPM. However, the true protein content in milk from primiparous cows increased linearly (2.92, 3.09, and 3.34 ± 0.077%). The addition of RPM linearly increased the net flux of Met across the portal-drained viscera, which resulted in increased arterial Met concentrations (25, 29, and 40 ± 1.1 µM). Although it had no significant effect on net portal and hepatic fluxes of other essential amino acids, RPM resulted in a linear increase in the total splanchnic output of Ile, Leu, Phe, and Thr. These results suggest that feeding RPM triggered a homeostatic response resulting in less utilization of certain essential amino acids through the gastrointestinal tract and liver. Net mammary uptake of Met did not change with the addition of RPM. However, mammary extraction of Met decreased in a linear fashion in response to increased arterial inflow. [ABSTRACT FROM AUTHOR]

Four lactating Holstein cows equipped with ruminal, duodenal, and ileal cannulas were used in 2 studies to evaluate the disappearance of supplementary B-vitamins before and from the small intestine. The cows were fed a total mixed ration with chromic oxide in 12 daily meals. Each study consisted of a control (no vitamin supplementation) and a treatment period (with vitamin supplementation). Amounts of vitamins (mg/ d) supplemented in studies 1 and 2, respectively, were: thiamin: 300 and 10; riboflavin: 1600 and 2.0; niacin: 12,000 and 600; vitamin B6:800 and 34; biotin: 20 and 0.02; folic acid: 2600 and 111; vitamin B12:500 and 0.4. In study 1, vitamins were added to the feed 5 d before and during the 4-d collection period. In study 2, vitamins were infused postruminally 1 d before and during the 4-d collection period. Substantial disappearance before the duodenal cannula was noted in study 1 (67.8% thiamin, 99.3% riboflavin, 98.5% nicotinamide, 41.0% pyridoxine, 45.2% biotin, 97.0% folic acid, and 62.9% vitamin B12). Except for nicotinamide and folate, there was almost no disappearance of postruminally infused vitamins before the duodenal cannula (study 2), suggesting extensive ruminal destruction or use. Apparent intestinal absorption values differed greatly among vitamins, but the proportion of vitamins disappearing from the small intestine was not negatively influenced by supplementation. Except for riboflavin and niacin, absolute amounts disappearing from the small intestine were greater during the treatment than the control periods, suggesting that B-vitamin supply in dairy cows is increased by supplementation, although losses in the rumen are extensive. [ABSTRACT FROM AUTHOR]

A database reviewing the metabolism of nitrogen (N) compounds from absorption to milk has been compiled from 14 published and unpublished studies (33 treatments) that measured the net flux of N compounds across the splanchnic tissues in dairy cows. Apparent N digestibility averaged 0·65, with this then partitioned between 0·34 excreted in urine and 0·31 secreted as milk. Nitrogen metabolites are absorbed from the lumen of the gut into the portal vein, mainly as free amino acids (AA) and ammonia; these represented 0·58 and 0·57 of digested N, respectively. All of the ammonia absorbed was removed by the liver with, as a result, a net splanchnic flux of zero. Detoxification of ammonia by the liver and catabolism of AA results in production of urea as an end-product. Hepatic ureagenesis is a major cross-road in terms of whole body N exchange, being the equivalent of 0·81 of digested N. Therefore, salvage of a considerable part of this ureagenesis is needed to support milk protein synthesis. This salvage occurs via transfer of urea from the blood circulation into the lumen of the gut. On average, 0·47 of hepatic ureagenesis was returned to the gut via the portal-drained viscera (equivalent to 0·34 of digested N) with 0·56 of this then used for anabolic purposes e.g. as precursor N for microbial protein synthesis. On average, 0·65 of estimated digestible AA was recovered in the portal vein. This loss (0·35) is due to oxidation of certain AA across the gut wall and non-absorption of endogenous secretions. The magnitude of this loss is not uniform among AA and varies between less than 0·05 for histidine to more than 0·90 for some non-essential AA, such as glutamine. A second database (six studies, 14 treatments) was constructed to further examine the subsequent fate of absorbed essential AA. When all AA are aggregated, the liver removed, on average, 0·45 of portal absorpti... [ABSTRACT FROM AUTHOR]

Forty crossbred steers (456 ± 14 kg BW) were used in a study with a 2 × 2 factorial arrangement of treatments to determine the effect of corn particle size (cracked or ground) and soybean meal processing (solvent extracted 48% CP soybean meal or lignosulfonate treated soybean meal; Soypass™) on feed intake, weight gain and feed-to-gain ratio during the finishing phase. Corn silage (31.7, 8.4, and 47.6% of DM, CP, and NDF, respectively) was offered for ad libitum consumption, while corn and soybean meal were fed at 6.6 and 0.54 kg DM/d, respectively. Animals received the corn silage individually once a day and half of the supplement was added on the top of the silage in the morning and the reminder in the afternoon. Dry matter offered and orts were recorded daily. Animals were treated against internal parasites (Ivermectin) and received an ionophore (Bovatec®), and growth stimulant (Revalor S®). Steers were weighed on three consecutive day at the beginning and at the end of the experiment. Animals were slaughtered when ultrasound backfat thickness was between 4 - 10 mm (Canada grade A). Duration of the experiment was not affected (P > 0.10) by treatment and averaged 99 d (SEM = 4). Dry matter intake, ADG, and feed-to-gain ratio were not affected (P > 0.10) by treatment and averaged 11.1 ± 0.3 kg/d, 1.65 ± 0.08 kg/d, and 6.7 ± 0.3 kg DMI/kg gain, respectively. No interaction between soybean meal treatment and corn processing was observed. During a digestion trial run concomitantly, results indicated that reducing particle size of corn increased apparent total tract digestibility of starch (0.96 vs 0.91 ± 0.01; P < 0.01) while neutral detergent fiber digestibility tended to decrease (0.24 vs 0.37 ± 0.06; P < 0.07). In conclusion, although starch was more digestible, reducting corn particle size had no effect on performance of finishing steers fed a corn silage-based diet. This could be partly explained by reduction in fiber digestion. No effect soybean meal sources or interaction between supplements was observed when performance of finishing steers was compared. [ABSTRACT FROM AUTHOR]

In an attempt to develop a non-invasive, accurate technique to determine the effect of treatment of soybean meal (SBM) on lysine (Lys) availability, the increment in plasma Lys irreversible loss rate (ILR) was compared with the increment in Lys intestinal flow and apparent digestibility. Four multiparous Holstein cows (173 DIM) with ruminal and duodenal cannulas were used in a 4 x 4 Latin square with 14-d periods. They were fed either solvent extracted SBM (SE), expeller SBM (EP) or lignosulfonate treated SBM (LS) as 23% of the diet. The fourth treatment (SE20) consisted in a 20 mmol/h omasal infusion of Lys to cows fed the SE diet. On the last day of each period, a pulse dose of [2-15 N] Lys was given in the jugular vein and jugular plasma samples were collected at 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 13, 16, 19, 25 and 31 min after the injection. Chromic oxide was included as an indigestible marker to asses DM flow and 8 separated digesta samples were collected on d 13 and 14 and pooled by period. The decay curve of 15 N Lys enrichment was explained by a two exponential equation. The plasma Lys ILR was not different (P>0.10) between the different SBM (84, 89 and 80 ± 3.9 mmol/h for SE, EP and LS, respectively). However, the SE20 treatment increased (P<0.04) Lys ILR to 104 mmol/h, i.e. exactly 20 mmol/h above the SE treatment. No differences were observed on duodenal Lys flow (213, 203 and 213± 11.9 g/d) or apparent intestinal digestion (79, 75 and 77 ± 1.8 %) between the SBM diets. Plasma Lys ILR was an accurate technique to estimate the increment of Lys availability, as it responded quantitatively to Lys infusion. Although the treatment of SBM should have increased Lys availability (NRC 2001), differences were too small or too variable to be detected. Further studies should be performed to test the sensitivity of this method, increasing the power of detection with larger amount of animals. [ABSTRACT FROM AUTHOR]

The effect of the length of the daylight period before cutting (0, 2, 4, 8, or 12 hours) on water soluble carbohydrates, starch, and total non-structural carbohydrates (TNC) concentrations was assessed on alfalfa (Medicago sativa cv AC Caribou) grown under controlled conditions. We also determined the impact of the length of the daylight period on rumen fermentation assessed by in vitro gas production. Forage samples (n=4) at each sampling time were dried at 55°C immediately after harvest, ground to pass a 1 mm screen, and incubated for up to 142 h in an anaerobic medium inoculated with rumen fluid. Regular measurements of gas were taken to assess the rate of fermentation using the following gas production model (Y = A {1- e [-b (t-T) -c (√ t - √ T)]}). At the end of the incubation period, samples of the liquid phase were analysed for ammonia-N and volatile fatty acids. Gas production model parameters and measured effluent parameters were analyzed as a completely randomized design with 5 duration of daylight and 4 replicates per treatment. Starch and TNC concentrations in alfalfa increased (mean starch = 4.2, 5.6, 5.6, 4.5 and 10.4% DM; mean TNC = 11.9, 13.7, 14.0, 12.9 and 18.5% DM; P < 0.001) with the length of the daylight period. Rumen fermentation also increased (P < 0.01) with the length of the daylight period before cutting as shown by parameters (half-life; mean = 10.09, 10.61, 10.56, 10.24, 11.32 h and maximum values; mean = 231.5, 236.3, 236.9, 230.7, 248.9 ml) describing cumulated gas production curves. Propionate concentrations in the liquid phase increased linearly (mean = 11.8, 11.6, 12.8, 13.6, 14.6 mmol/L; P = 0.01) with a longer daylight period. Increasing the daylight period up to 12 h before cutting favoured the accumulation of starch and TNC in alfalfa and had a positive effect on rumen fermentation. [ABSTRACT FROM AUTHOR]

Six Holstein cows (BW=728 ± 59 kg; DIM=90 ± 30 d) were used in a replicated 3 x 3 Latin square design with 35-d periods to determine the effect of ionophore (IOP) supplementation on N metabolism. Cows were fed for ad libitum intake a legume silage-based TMR (17.5 % CP) without IOP (C) or either with lasalocid (L) or monensin (M) at a dose of 24 ppm on a DM basis. Orthogonal contrasts were used to compare IOP (L + M) vs. C, and L vs. M. Signiflcance was declared at P≤0.05. Milk production and DMI averaged 36.6 and 23.5 kg, respectively and were not affected by IOP supplementation. Milk fat and milk protein concentrations were similar among treatments and averaged 3.35 and 3.38 %, respectively. Compared to C, IOP supplementation tended (P=0.07) to reduce ruminal NH3-N concentration and signiflcantly increased N apparent digestibility, but with no difference between L and M. Urinary urea N excretion was not different between C and IOP supplementation, but was lower with L than with M (112 vs. 143 g/d). In parallel, plasma urea N concentration tended (P=0.06) to be lower and milk urea N concentration was lower with L compared to M (11.0 vs. 12.3 mg/dL). Data from this study demonstrate that ionophores have similar effects on N metabolism in the gastrointestinal tract but differences in urea excretion and concentrations indicate a possible decrease in amino acid catabolism with lasalocid. [ABSTRACT FROM AUTHOR]

High-moisture ear corn (HMEC) was treated with bacterial inoculants or ammonia to investigate their efficiency in maintaining silage quality after air exposure and their effects on finishing performance of steers. These treatments were compared 1) untreated HMEC (Control) 2) Lactobacillus plantarum and Enterococcus faecium(HOB: Homolactic bacteria; 0.91 x 105 cfu/g of fresh HMEC); 3)Lactobacillus buchneri(HEB: Heterolactic bacteria; 1.0 x 105 cfu/g of fresh HMEC); 4) aqueous solution of ammonia (AMMO; 16 g/kg of fresh HMEC). In the fermented material, HEB and AMMO exhibited the lowest counts of yeasts (4.2 and 4.6 log10 cfu/g of fresh weight; SEM=1.21 and SEM=1.29 respectively) and molds (2.8 and 2.3 log10 cfu/g of fresh weight; SEM=0.96 and SEM=0.54 respectively) and HEB presented the lowest aerobic instability index (15.3°C/day; SEM=7.4). A growth trial using 36 steers (BW 427 kg) grown over 142 d according to an incomplete block design and a digestion trial using 4 additional steers (BW 423 kg) according to a 4x4 Latin square design were conducted. In both trials, steers fed either treated or control HMEC had similar DM intake expressed in % of BW (1.98%; SEM=0.02). Treatments had no effect on BW gain, feed efficiency, hot carcass weight, carcass yield and quality grade (P > 0.10). In HOB compared to control, apparent digestibility of nitrogen and ADF was increased (74.0% and 42.2% respectively; (P < 0.05) and DE and ME tended to be higher (P < 0.10). Nitrogen retention was increased (P < 0.05) with HOB and AMMO (34.4% and 33.9% of N intake, respectively). This study supports previous observations that bacterial inoculants and ammonia are not detrimental to growth performance, but some may be more appropriate in maintaining silage quality and avoiding biodegradation of dry matter. [ABSTRACT FROM AUTHOR]

Abstract: A study was conducted to determine effects of water soluble carbohydrate (WSC) concentration on ensiling characteristics, chemical composition and in vitro digestibility of forage millet and forage sorghum. Two cultivars (regular and high WSC content) of each forage were harvested at late vegetative stage and ensiled in mini-silos for 0, 2, 4, 8, 16 and 48d. Ensiled forages went through a rapid fermentation as indicated by a sharp decline in pH during the first 2d of ensiling. Between day 0 and 8 post-ensiling, pH was higher (P<0.05) for ensiled millet than ensiled sorghum forages and was lower for high WSC than regular cultivars. Lactic acid concentration was higher (P<0.05) in high WSC than in regular cultivars and was not affected by forage type. Chemical composition of the 45-d silages showed that forage millet silages contain more (P<0.05) neutral (aNDF) and acid detergent fiber than forage sorghum silages. Fiber fractions were not affected by WSC content except for lignin(sa), which was higher (P<0.05) for regular versus high WSC cultivars. Soluble and non-protein N were higher (P<0.05) in forage millet than forage sorghum silages and were higher for high WSC versus normal cultivars. In vitro gas production, degradation rate and volatile fatty acid production were not affected by forage type but were higher (P<0.05) for high WSC versus normal cultivars. In vitro dry matter and aNDF digestibilities were higher for forage sorghum versus forage millet silages, and were higher for high WSC versus normal cultivars. High WSC content improved ensiling characteristics of both forages, but the effect was more pronounced for forage sorghum than for forage millet. Based on chemical composition and in vitro data, we conclude that the feeding value of forage sorghum silage is superior to that of forage millet silage when harvested at the same stage of physiological development. [Copyright &y& Elsevier]

The distribution of 15N in AA during [15N]Leu infusion and its impact on the estimation of endogenous nitrogen (EN) flows in dairy cows was evaluated in 4 lactating cows equipped with ruminal, duodenal (n = 4), and ileal (n = 2) cannulae fed a silage-based diet during a 35-d experimental period. To label EN, starting on d 27, an infusion of L-[15N]Leu (0.45 mmol/h) was performed for 200 h. Samples of feed, duodenal and ileal digesta, feces, blood, urine, and mucosa of the rumen and duodenum were taken at 0900, 1100, 1300, and 1500 h on d 34 and at 0800, 1000, 1200, and 1400 h on d 35. The enrichment and fluxes of total N and individual AA were determined and used to calculate the EN flows at the duodenum, ileum, and in the feces. Based on the concept that EN comprises desquamation and secretions, EN flows were estimated, using as representative of the enrichment of EN only the enrichment of the gut mucosa (upper limit) or the average of the mucosa and the export protein enrichment (assumed to have a similar enrichment to casein; lower limit). Estimations of duodenal and fecal EN flows using the isotope dilution of 15N-total and 15N-Leu were not different and EN was an important fraction of duodenal and fecal flows, representing 14 to 30% of the duodenal flow and 18 to 31% of the fecal flow, depending on the dilution method used. The total EN flow at the duodenum is present in approximately equal proportions as either free EN or EN incorporated into bacterial protein. Ileal EN flow was 18% greater than the fecal EN flow. Using the combination of the gut and export protein, the duodenal and fecal EN flows estimated with the isotopic dilution of Leu vs. other labeled AA were less different than when estimated using the enrichment of gut mucosa alone. The current approaches have highlighted that present prediction schemes probably underestimate EN flows at the duodenum and, in consequence, overestimate net protein and AA supply. Refinement of the procedures may allow direct and accurate estimation of metabolic fecal protein, an important component of the so-called maintenance requirement of dairy cows. [ABSTRACT FROM AUTHOR]

Four Holstein cows fitted with ruminal cannulas were used in a 4 x 4 Latin square design (28-d periods) with a 2 x 2 factorial arrangement of treatments to investigate the effects of addition of a specific mixture of essential oil compounds (MEO; 0 vs. 750 mg/d) and silage source [alfalfa silage (AS) vs. corn silage (CS)] on digestion, ruminal fermentation, rumen microbial populations, milk production, and milk composition. Total mixed rations containing either AS or CS as the sole forage source were balanced to be isocaloric and isonitrogenous. In general, no interactions between MEO addition and silage source were observed. Except for ruminal pH and milk lactose content, which were increased by MEO supplementation, no changes attributable to the administration of MEO were observed for feed intake, nutrient digestibility, end-products of ruminal fermentation, microbial counts, and milk performance. Dry matter intake and milk production were not affected by replacing AS with CS in the diet. However, cows fed CS-based diets produced milk with lower fat and higher protein and urea N concentrations than cows fed AS-based diets. Replacing AS with CS increased the concentration of NH3-N and reduced the acetate-to-propionate ratio in ruminal fluid. Total viable bacteria, cellulolytic bacteria, and protozoa were not influenced by MEO supplementation, but the total viable bacteria count was higher with CS- than with AS-based diets. The apparent digestibility of crude protein did not differ between the AS and CS treatments, but digestibilities of neutral detergent fiber and acid detergent fiber were lower when cows were fed CS-based diets than when they were fed AS-based diets. Duodenal bacterial N flow, estimated using urinary purine derivatives and the amount of N retained, increased in cows fed CS-based diets compared with those fed AS-based diets. Feeding cows AS increased the milk fat contents of cis-9, trans-11 18:2 (conjugated linoleic acid) and 18:3 (n-3 fatty acid) compared with feeding cows CS. Results from this study showed limited effects of MEO supplementation on nutrient utilization, ruminal fermentation, and milk performance when cows were fed diets containing either AS or CS as the sole forage source. [ABSTRACT FROM AUTHOR]

This study was undertaken to determine the relationship between measured net portal absorptions (NPA) and flows of digestible essential amino acids (EAA) predicted with the National Research Council model (NRC, 2001) or the Cornell Net Carbohydrate and Protein System model (CNCPS, version 5.0.34). Net portal absorption data were obtained from 33 measurements of portal-arterial plasma EAA concentration differences among 8 treatments in lactating dairy cows, with plasma flow estimated from downstream dilution of para amino-hippurate. The predicted digestible flows from NRC (2001) related better than CNCPS to NPA observed in our studies, as shown by the lower standard errors on the slopes for all EAA and lower root mean prediction errors for all EAA except Met and Phe. However, the partitioning of the prediction error indicated a systematic underprediction (mean bias) for the NRC model (2001), with the exception of Ile. It is important to note that a relationship of unity was not expected, as discussed in the paper, because of losses of EAA through portal-drained viscera metabolism. A revised set of predictive equations for digestible EAA was obtained using a subset of data from NRC (2001) limited to trials conducted with dairy cows. This increased the predicted flows of digestible EAA by only 2%. Flows of digestible EAA were also estimated using a factorial approach, assuming an AA composition for each fraction of the duodenal flow estimated by NRC (undegradable, microbial, and endogenous proteins). This resulted in a slight improvement in the slope of the regression between predicted flows and measured NPA, but still yielded predicted digestive flows that were too low to support observed NPA. Finally, on the basis of literature values, increment of the digestibility of the undegradable fraction of forages and of microbial protein is suggested to improve the relationship between predicted digestible flows and NPA. Overall, this study indirectly confirms, across EAA, smaller losses through gut metabolism for His, Met, and Lys, intermediate losses for the branched-chain AA with the higher losses for Thr. [ABSTRACT FROM AUTHOR]