Subacute ruminal acidosis (SARA) was induced in 3 rumen fistulated Jersey steers by offering them different combinations of wheat-barley pellets and chopped alfalfa hay. Steers were offered 4, 5, and 6 kg/d of pelleted concentrate and 6, 5, and 4 kg/d of chopped alfalfa hay for diets 1, 2, and 3, respectively, during 5-d treatment periods and were fed chopped alfalfa hay between treatment periods. Inducing SARA increased blood concentrations of haptoglobin and serum amyloid-A. Dry matter intake of concentrate and hay decreased from d 1 to 5 in each period. Subacute ruminal acidosis was induced in all steers during d 4 and 5 when concentrate was fed, with ruminal pH remaining below 5.6 for an average of 187 and 174 min/d on these days. Lipopolysaccharide concentration increased significantly during periods of grain feeding compared with times when only hay was fed. Inducing SARA by feeding wheat-barley pellets activated a systemic inflammatory response in the steers.

No abstract

. Impact of pasture type on methane production by lactating beef cows. Can. J. Anim. Sci. 79: 221-226. In order to determine the quantity of methane (CH 4 ) produced by lactating beef cows on pasture, 16 Hereford-Simmental first-calf heifers with a mean weight of 511.2 ± 5.8 kg were randomly selected from a larger group of cows (n = 60) on a grazing management experiment and used to evaluate the effects of pasture type on ruminal CH 4 production using the sulfur hexafluoride (SF 6 ) tracer-gas technique. Pasture treatments consisted of two pasture types, alfalfa-grass [78% alfalfa (Medicago sativa L.) -22% meadow bromegrass (Bromus biebersteinii Roem and Schult.)] or 100% meadow bromegrass at each of two fertility levels (either unfertilized or soil test recommended fertilizer levels) with two replications of each pasture treatment (8 pastures). Cows were managed using a "put and take" stocking system to leave equal residual herbage mass on all treatments following the grazing period in each paddock. During the 69-d grazing season, two cows from each pasture were sampled to determine daily forage intake and CH 4 production on four occasions. The chemical composition of diets differed between pasture types and sampling periods. Dry matter intake was greater for cows grazing alfalfa-grass pastures than for cows grazing grass-only pastures (11.4 vs. 9.7 kg DM d -1 ; P < 0.018). However, methane production was greater for cows grazing alfalfa-grass pastures than for cows grazing grass-only pastures (373.8 vs. 411.0 L CH 4 d -1 ; P < 0.008). Consequently, energy lost through eructation of CH 4 was less for cows grazing alfalfa-grass pastures than it was for cows grazing grass-only pastures (7.1 vs. 9.5% of GEI; P < 0.001). Hereford-Simmental primipares en lactation, pesant en moyenne 511,2 ± 5,8 kg, ont été prises au hasard dans une plus grande population de vaches (n = 60) pour participer à une expérience de conduite du pâturage. L'objet était d'évaluer les effets de la composition du pâturage sur la production ruminale de CH 4 au moyen de la technique au gaz traceur hexafluorure de soufre (FS6). Deux types de pâturage étaient comparés, 1 peuplement pur de brome des prés (Bromus biebersteinii Roem & Schult.) et un mélange à 78 % luzerne (Medicago sativa L.) et 22 % brome des prés, chacun à deux niveaux de fertilité, sans fumure et fumure recommandée selon l'analyse du sol. Chaque traitement comportait 2 répétitions. Le chargement animal adopté était du type variable, de façon à laisser une même masse herbagère résiduelle dans tous les traitements au terme de la période de pâturage. Durant cette période de 79 jours, deux vaches de chaque enclos étaient utilisées à 4 reprises pour déterminer l'ingestion quotidienne d'herbe et la production de CH 4 . La composition chimique du fourrage différait selon la nature du pâturage et selon la date des prélèvements. L'ingéré de m.s. était plus abondant chez les vaches pâturant l'association luzerne-graminée que chez celles broutant le peuplement pur de graminée (11,4 contre 9,7...

Fatty acid profiles with emphasis on linoleic, linolenic, oleic, and conjugated linoleic acid (CLA) were compared in milk from dairy cows fed diets containing 3.25% supplemental fat and a control diet containing no supplemented fat. The fat was supplied by either whole ground solin, flax, or canola oilseed. Solin (linola) is a new cultivar of flax that contains 28% linoleic acid in the seed, Twelve multiparous Holstein cows were assigned to one of four dietary treatments. The experimental design was a 4 x 4 Latin square with each period consisting of 16 d for adjustment to the diet followed by a 5-d sampling period. Feed intake, milk yield, milk fat yield, and milk fat percentage were not affected by treatment. Adding solin, flax, or canola oilseed to lactation diets produced the highest proportions of linoleic (C18:2), linolenic (C18:3), and oleic (C18:1) acids, respectively, in the lipid fraction of the milk of the cows consuming these diets. The proportions of C6:0 to C16:1 were depressed in the milk fat of cows fed the oilseed diets, compared with the control diet. Increasing the lactation diet levels of C18:2, by using different oilseeds, increased CLA to 1.5% of milk fatty acids. The content of CLA in milk fatty acids, however, did not increase with the solin-supplemented diet compared with the canola-supplemented diet even though the C18:2 level was higher in the former diet.

to determine the quantity of methane (CH 4 ) produced by steers on pasture, 16 steers with a mean weight of 356 ± 25 kg were randomly selected from a larger group of cattle (n = 48) to evaluate the effects of grazing management and monensin controlled release capsule (CRC) administration on ruminal CH 4 production using the sulphur hexafluoride (SF 6 ) tracer-gas technique. Pasture management treatments consisted of two grazing systems (continuous stocking or 10-paddock rotational stocking) at each of two stocking rates (low, 1.1 steer ha -1 or high, 2.2 steers ha -1 ) with two replications of each pasture treatment. Half of the animals on each pasture treatment were administered a monensin CRC delivering 270 mg d -1 , and untreated animals served as controls. During the 140-d grazing season, one steer from each treatment-replicate combination was sampled to determine daily intake and CH 4 production on four occasions. The chemical composition of diets differed between grazing management treatments and sampling periods. Voluntary intake and CH 4 production, adjusted for differences in body weight, were unaffected by grazing management, sampling period or by monensin CRC administration and averaged 0.69 ± 0.1 L kg BW -1 d -1 across all grazing management treatments. The energy lost through eructation of CH 4 averaged 4.5 ± 1.4% of gross energy intake.