Twenty-four multiparous Holstein cows, 4 of which were ruminally fistulated, were assigned to one of four diets containing full-fat soybeans, either raw or extruded at 120, 130, or 140 degrees C. Our hypothesis was that the extrusion of full-fat soybeans, as well as the extrusion temperature, would affect the bypass of fatty acids in the rumen and, thus, would modify the fatty acid profile of milk fat. Total mixed diets containing 23.7% soybeans (percentage of DM) were fed for 8 wk. Milk yield was lower, and the proportion of milk CP was higher, for cows fed raw soybeans than for cows fed extruded soybeans. Compared with raw soybeans, extruded soybeans increased the concentration of delta-11-trans-C18:1 from 2.72 to 11.41% in milk fat but had no effect on yield or percentage of milk fat. Polyunsaturated fatty acids of raw soybeans disappeared more rapidly than did those of extruded soybeans from bags incubated in the rumen of fistulated cows. However, more delta-11-trans-C18:1 and C18:0 appeared in bags containing extruded soybeans than in bags containing raw soybeans. Extrusion of full-fat soybeans influenced the metabolism of fatty acids in the rumen and the fatty acid profile of milk fat, but the temperature of extrusion had only minor effects on these parameters.

. 2004. Distribution of intramuscular fat content and marbling within the longissimus muscle of pigs. Can. J. Anim. Sci. 84: 57-61. A better knowledge of intramuscular fat (IMF) content distribution would allow the identification of a predictive site on the longissimus muscle to assess the total IMF content. For this purpose, 50 commercial crossbred pigs of both genders were selected live with ultrasound equipment at the 3rd/4th last rib in order to provide backfat differences varying from 10 to 34.7 mm. Left longissimus muscles were deboned and sliced every 2 cm from the posterior (3rd last lumbar vertebra) to the anterior (5th thoracic rib) end. In all, 14 locations on the longissimus muscle were established and labeled as T5-T14 (thoracic region) and L1-L4 (lumbar region). The slices were used for subjective marbling evaluation and for intramuscular fat content (IMF) measurement. The results showed that total IMF content and marbling scores were correlated (r = 0.86) and followed a similar pattern, with highest values being obtained in the middle section of the thoracic region and in the middle-caudal section of the lumbar area. In addition, both IMF content and marbling scores were anatomical location dependant. Gender did not affect IMF content, but influenced marbling score, castrates being more marbled (score: 2.77 vs. 2.35) than females. The IMF content (R 2 : 0.94-0.95) and marbling score (R 2 : 0.73-0.81) were the best predictors of mean IMF when measured at or near the grading site (3rd/4th last rib).Key words: Pork, intramuscular fat, marbling score, longissimus muscle, within muscle variation Faucitano, L., Rivest, J., Daigle, J. P., Lévesque, J. et Gariepy, C. 2004. Variation de la teneur en gras intramusculaire et du persillage dans le muscle longissimus dorsi de porc. Can. J. Anim. Sci. 84: 57-61. Une meilleure connaissance de la distribution du gras intramusculaire permettrait de déterminer une zone précise sur le muscle longissimus à partir de laquelle on pourrait évaluer la teneur totale en gras intramusculaire. Pour vérifier cette hypothèse, nous avons choisi 50 porcs commerciaux croisés, des deux sexes, avant l'abattage dont nous avons mesuré l'épaisseur de gras dorsal au niveau de la 3 e /4 e côte à l'aide d'un appareil à ultrasons. Les animaux retenus présentaient des différences d'épaisseur de gras dorsal variant de 10 à 34.7 mm. Après l'abattage, le muscle longissimus du côté gauche des carcasses a été désossé et coupé en tranches de 2 cm, à partir de l'extrémité postérieure (3 e dernière vertèbre lombaire) jusqu'à l'extrémité antérieure (5 e côte thoracique). En tout, 14 zones du longissimus ont été déterminées et numérotées comme suit : T5 à T14 (région thoracique) et L1 à L4 (région lombaire). Nous avons utilisé les tranches pour évaluer le persillage et mesurer la teneur en gras intramusculaire. Les résultats ont révélé une correspondance entre la teneur totale en gras intramusculaire et la cote de persillage (r = 0,86). Nous avons également constaté que ces paramètres suivent des pr...

No abstract

Amino acid requirements of two biotypes (C and J) of the pea aphid, Acyrthosiphon pisum (Harris), were studied by deleting single amino acids from a chemically defined liquid diet. Amino acids found to be essential for growth and (or) reproduction of biotype C were arginine, histidine, leucine, lysine, methionine, threonine, and tryptophan, and for biotype J, histidine, methionine, phenylalanine, threonine, and valine. Two generations were needed on deficient diets to demonstrate the essentiality of some of the amino acids. This appears to be a rare example of two insect populations within one species differing in their amino acid requirements. It is suggested that intracellular symbiotes play a major role in supplying the aphids with missing amino acids.

Sub-acute ruminal acidosis (SARA) is sometimes observed along with reduced milk fat synthesis. Inconsistent responses may be explained by dietary fat levels. Twelve ruminally cannulated cows were used in a Latin square design investigating the timing of metabolic and milk fat changes during Induction and Recovery from SARA by altering starch levels in low-fat diets. Treatments were (1) SARA Induction, (2) Recovery and (3) Control. Sub-acute ruminal acidosis was induced by feeding a diet containing 29.4% starch, 24.0% NDF and 2.8% fatty acids (FAs), whereas the Recovery and Control diets contained 19.9% starch, 31.0% NDF and 2.6% FA. Relative to Control, DM intake (DMI) and milk yield were higher in SARA from days 14 to 21 and from days 10 to 21, respectively (P < 0.05). Milk fat content was reduced from days 3 to 14 in SARA (P < 0.05) compared with Control, while greater protein and lactose contents were observed from days 14 to 21 and 3 to 21, respectively (P < 0.05). Milk fat yield was reduced by SARA on day 3 (P < 0.05), whereas both protein and lactose yields were higher on days 14 and 21 (P < 0.05). The ruminal acetate-to-propionate ratio was lower, and the concentrations of propionate and lactate were higher in the SARA treatment compared with Control on day 21 (P < 0.05). Plasma insulin increased during SARA, whereas plasma non-esterified fatty acids and milk β-hydroxybutyrate decreased (P < 0.05). Similarly to fat yield, the yield of milk preformed FA (>16C) was lower on day 3 (P < 0.05) and tended to be lower on day 7 in SARA cows (P < 0.10), whereas yield of de novo FA (<16C) was higher on day 21 (P < 0.01) in the SARA group relative to Control. The t10- to t11-18:1 ratio increased during the SARA Induction period (P < 0.05), but the concentration of t10-18:1 remained below 0.5% of milk fat, and t10,c12 conjugated linoleic acid remained below detection levels. Odd-chain FA increased, whereas branched-chain FA was reduced during SARA Induction from days 3 to 21 (P < 0.05). Sub-acute ruminal acidosis reduced milk fat synthesis transiently. Such reduction was not associated with ruminal biohydrogenation intermediates but rather with a transient reduction in supply of preformed FA. Subsequent rescue of milk fat synthesis may be associated with higher availability of substrates due to increased DMI during SARA.