Seven ruminally cannulated lactating Holstein dairy cows were used in an incomplete Latin rectangle design to assess the effects of 2 commercial essential oil (EO) products on rumen fermentation, milk production, and feeding behavior. Cows were fed a total mixed ration with a 42:58 forage:concentrate ratio (DM basis). Treatments included addition of 0.5 g/d of CE Lo (85 mg of cinnamaldehyde and 140 mg of eugenol), 10 g/d of CE Hi (1,700 mg of cinnamaldehyde and 2,800 mg of eugenol), 0.25 g/d of CAP (50mg of capsicum), or no oil (CON). Cows were fed ad libitum twice daily for 21 d per period. Dry matter intake, number of meals/d, h eating/d, mean meal length, rumination events/d, h ruminating/d, and mean rumination length were not affected by EO. However, length of the first meal after feeding decreased with addition of CE Hi (47.2 min) and CAP (49.4 min) compared with CON (65.4 min). Total volatile fatty acids, individual volatile fatty acids, acetate:propionate ratio, and ammonia concentration were not affected by EO. Mean rumen pH as well as bouts, total h, mean bout length, total area, and mean bout area under pH 5.6 did not differ among treatments. Total tract digestibility of organic matter, dry matter, neutral detergent fiber, acid detergent fiber, crude protein, and starch were not affected by EO. Milk yield and composition did not change with EO. In situ dry matter disappearance of ground soybean hulls was not affected by EO. However, organic matter disappearance of soybean hulls with CE Hi tended to decrease compared with CON. Compared with CON, neutral detergent fiber disappearance (41.5 vs. 37.6%) and acid detergent fiber disappearance (44.5 vs. 38.8%) decreased with addition of CE Hi. The CE Lo had no effect on rumen fermentation, milk production, or feeding behavior but CAP shortened the length of the first meal without changing rumen fermentation or production, making it a possible additive for altering feeding behavior. The CE Hi negatively affected rumen fermentation and shortened the length of the first meal, suggesting that a dose of 10 g/d is not beneficial to lactating dairy cows.

Elevated rates of steroid clearance may lead to lower reproductive success in several mammalian species. Cytochrome P450 (EC 1.14.14.1) and aldo-keto reductases (AKR; EC 1.1.1.145-151) are involved in the first phase of steroid inactivation, before second phase conjugation and excretion of the steroid metabolite. The current objectives were to determine liver blood flow (LBF), hepatic enzyme activity, and metabolic clearance rate (MCR) of progesterone (P 4 ) in dairy cows consuming isoenergetic and isonitrogenous diets formulated to cause divergent insulin secretion. Insulin concentrations increased by 22% in cows fed the high cornstarch diet, and both cytochrome P450 2C and cytochrome P450 3A activities were decreased (P!0 . 05) by w50%, while AKR1C tended (P!0 . 10) to be lower in cows fed the high cornstarch diet. LBF was similar between the two diets (1891G91 l/h). MCR of P 4 tended (P!0 . 10) to be lower in cows fed the high cornstarch diet ). The half-life of P 4 was increased (P!0 . 05) in cows fed the high cornstarch diet (73G10 min) versus the high fiber diet (24G10 min). In summary, cows with elevated insulin concentrations and lower enzyme activity showed a decrease in P 4 clearance without any changes in LBF. This dietary relationship with hepatic enzyme activity may explain some of the observed alterations in steroid profiles during the estrous cycle or gestation of the high producing dairy cow.

In the cow, inadequate concentrations of progesterone during gestation may lead to an abrupt termination of pregnancy. The primary organ involved in progesterone catabolism is the liver, which contains an abundance of cytochrome P450 isozymes (EC 1.14.14.1; mixed-function monooxygenases). The objectives of the current experiment were to determine the effect of feeding 2 isoenergetic and isonitrogenous diets, formulated to cause divergent insulin secretion, on hepatic cytochrome P450 2C (CYP2C) and 3A (CYP3A) activity as well as the resulting biological half-life of progesterone. Twenty-two Holstein cows averaging 80+/-7 d in milk were randomly assigned to either a high cornstarch diet or a high fiber diet in a crossover experimental design consisting of two 14-d periods. Dry matter intake, milk yield, milk lactose yield, and milk lactose percentage were similar between the 2 diets. Milk fat yield and milk fat percentage were higher in cows fed the high fiber diet, whereas milk protein yield tended to be higher and milk protein percentage was higher in cows fed the high cornstarch diet. Energy balance tended to be improved by 57% in cows consuming the high cornstarch diet. Insulin concentrations at the time of liver biopsy (3.16+/-0.04h post-feeding) were increased by 44% in cows consuming the high cornstarch diet compared with cows consuming the high fiber diet. Cytochrome P450 2C activity was decreased by 45%, whereas CYP3A activity tended to be lowered by 34% in cows consuming the high cornstarch diet. Cytochrome P450 2C mRNA expression tended to be decreased by 21% in cows fed the high cornstarch diet, whereas CYP3A mRNA expression was not different between the dietary treatments. The fractional rate constant of progesterone decay was not different between the 2 diets; however, the half-life of progesterone tended to be longer in cows fed the high cornstarch diet compared with cows fed the high fiber diet (85 vs. 64min, respectively). In summary, cows consuming the high cornstarch diet had increased insulin concentrations and lower hepatic CYP2C and CYP3A activity and tended to have a longer progesterone half-life compared with cows consuming the high fiber diet. Feeding diets that stimulate insulin secretion could alter progesterone clearance during lactation, when dairy cows have increased rates of progesterone inactivation because of high energy demands and increased DMI.

capsicum on fermentation of a corn-based dairy ration in continuous culture. Can. J. Anim. Sci. 90: 413Á420. A 12-unit continuous culture system was used in a complete randomized design to study the effects of no oil (CON), cinnamaldehyde oil (CIN), eugenol oil (EUG), and capsicum oil (CAP) (500 mg L(1 d (1 ) with a 45:55 forage:concentrate ratio (dry matter basis) ration on rumen fermentation. Dry matter digestibility did not differ among treatments. Organic matter digestibility tended to decrease with CIN. Digestibility of neutral detergent and acid detergent fiber tended to be highest with CAP. Crude protein digestibility and bacterial nitrogen flow was depressed with CIN and EUG. CIN tended to decrease microbial protein synthesis and increase effluent ammonia nitrogen. Total volatile fatty acid production did not differ among treatments; however, isovalerate production tended to be highest with CAP. CIN and EUG had higher mean pH, spent fewer hours per day and had smaller area under the curve at pHB5.6 and 5.8. CAP had smaller area under the curve at pH B5.6. Supplementation with these oils at the current dose had limited effects on rumen fermentation, with the majority of effects observed being mainly attributable to the very high dosage of oil used. [500 mg par litre et par jour] sur la fermentation dans le rumen d'une ration compose´e a`45:55 de fourrages et de concentre( selon la matie`re se`che). La digestibilite´de la matie`re se`che e´tait la meˆme pour les diffe´rents traitements. Celle de la matie`re organique a tendance a`diminuer avec CIN. La digestibilite´des fibres au de´tergent neutre et des fibres au de´tergent acide tend a`augmenter avec CAP. La digestibilite´des prote´ines brutes et le flux d'azote bacte´rien diminuent avec CIN et EUG. CIN a tendance a`favoriser la synthe`se de prote´ines par la microflore et a`augmenter la quantite´d'azote ammoniacal dans les effluents. La production totale d'acides gras volatils est la meˆme pour les divers traitements; ne´anmoins, la production d'isovale´rate a tendance a`atteindre un maximum avec CAP. CIN et EUG entraıˆnent un pH moyen plus e´leve´, persistent moins d'heures par jour et pre´sentent une plus petite superficie sous la courbe quand le pH est infe´rieur a`5,6 ou est de 5,8. CAP se caracte´rise par une plus petite superficie sous la courbe quand le pH ne de´passe pas 5,6. À la dose actuelle, un supple´ment de ces huiles aurait peu d'incidence sur la fermentation du rumen, car la majorite´des effets observe´s re´sultaient principalement de la tre`s forte concentration employe´e. Mots clé s:Vache laitie`re, huiles essentielles, culture continue, fermentation du rumen, pH du rumen Manipulation of rumen fermentation to improve feed efficiency in the livestock industry is often achieved through the use of antibiotics, such as the ionophore monensin. However, concern has increased recently over the use of antibiotics in the livestock industry due to the possible rise of antibiotic-resistant bacteria, which would be of great risk to human health (Be...

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