The objective of this study was to evaluate the effects of feeding essential oils from garlic (GAR) and juniper berry (JUN), or monensin (MO) on feed intake, ruminal fermentation, the site and extent of digestion, microbial protein synthesis, milk production, and immune status in dairy cows. Four midlactating Holstein cows fitted with ruminal and duodenal cannulas were used in a 4 x 4 Latin square design with 21-d periods and 4 treatments: control (no additive), MO (330 mg/cow per d), GAR (5 g/cow per d), and JUN (2 g/cow per d). Cows were fed ad libitum a TMR consisting of 40% forage and 60% barley-based concentrate. Dry matter intake averaged 20.4 kg/d and was not affected by dietary additives. Total tract digestibilities of dry matter, organic matter, fiber, and starch were not affected by experimental treatments. However, ruminal digestibilities of dry matter and organic matter were higher (+13%) for GAR and JUN than for the control diet, mainly because of increased crude protein digestion in the rumen. Feeding GAR and JUN increased ruminal digestion of dietary protein by 11% as compared with the control. In contrast, ruminal digestion of dietary protein was reduced by 11% with MO as compared with the control. Milk fat content was lower for MO (2.68%) than for the GAR (3.46%), JUN (3.40%), and control (3.14%) diets. No effects of GAR, JUN, or MO were observed on milk production, ruminal microbial protein synthesis, ruminal pH, and ruminal concentrations of volatile fatty acids and ammonia N. The total and differential numbers of white blood cells as well as serum amyloid A and haptoglobin were not affected by the treatments, suggesting that additives had no effect on the immune status of cows. Results of this study indicate that supplementing dairy cows with GAR (5 g/d) and JUN (2 g/d) essential oils improved feed digestibility in the rumen, but possibly at the expense of a reduction in the flow of bypass protein to the small intestine. Feeding monensin could be beneficial in terms of increasing bypass protein from the rumen but did not improve feed digestion or milk production under the current experimental conditions.

Cinnamaldehyde (CIN), a natural chemical compound found in the bark of cinnamon trees, can alter rumen fermentation by inhibiting selected ruminal microbes, and consequently, may improve growth performance and feed efficiency of animals. The objective of this study was to evaluate the effects of supplementing the diet of feedlot cattle with CIN on intake, growth performance, carcass characteristics, and blood metabolites. Seventy yearling steers (BW = 390 +/- 25.2 kg) were assigned to a randomized complete block design with 5 treatments: control (no additive), monensin (MO; 330 mg*steer(-1)*d(-1)), and 400, 800, or 1,600 mg of CIN*steer(-1)*d(-1). At the start of the experiment, steers were blocked according to BW and assigned to 14 blocks of 5 cattle, with cattle within block assigned to treatments. The diets consisted of 9% barley silage, 86% dry-rolled barley grain, and 5% supplement (DM basis). Dry matter intake responded quadratically (P = 0.03) to CIN supplementation with 13% more feed consumed for steers fed CIN (mean of 3 CIN levels) compared with those fed control during the first 28 d of the experiment, and with a tendency of 4% increase over the entire experiment. The ADG (kg/d) tended to respond quadratically (P = 0.08) to CIN supplementation during the first 28 d, but was not affected over the entire experiment (112 d). Feed efficiency (G:F) linearly declined (P = 0.03) during the first 28 d with CIN supplementation and was quadratically affected between d 29 to 56 and d 85 to 112 by CIN dose. Supplementation of MO did not affect (P > 0.15) DMI or growth performance at any time during the experiment. Serum NEFA concentrations were reduced (P = 0.05) by 35, 29, 30, and 22%, respectively, on d 56, 84, 112, and overall with CIN supplementation. Concentrations of serum amyloid A were reduced on d 28 by 56, 60, or 56% for 800 mg of CIN, 1,600 mg of CIN, and MO, respectively, compared with control. Plasma concentrations of lipopolysaccharide binding protein were linearly decreased (P = 0.05) with increasing CIN supplementation on d 28. Results indicate that supplementing a feedlot finishing diet with a small dose of CIN ameliorated feed intake during the initial month but had minimal effects on ADG, feed efficiency, and carcass traits over the entire experiment. Including CIN in the diet of feedlot cattle, particularly early in the feeding period, may help promote intake and reduce the effects of stress.

The effect of feeding increasing levels of oleic and linoleic acid both independently and together, with or without monensin, on milk fat depression was evaluated. Fifty-six Holstein cows were blocked by parity and then were divided by milk production into 2 groups (high or low) of 14 cows each within each parity block. A cow pair of 1 high and 1 low production cow within each parity block was fed in a single electronic feeding gate. Gates (n = 28) were considered the experimental unit and were assigned to monensin (17.5 g/t of dry matter) or control as the main plot (n = 14 each). The 7 cow pairs in each of the fixed effect groups were further assigned to a sequence of fat blend diets as split plot. Seven fat blend treatments in the split plot 7 × 7 Latin square were no added fat (no fat) and diets with increasing levels of oleic or linoleic acid: low C18:1 + low C18:2 (LOLL); low C18:1 + medium C18:2 (LOML); low C18:1 + high C18:2 (LOHL); medium C18:1 + low C18:2 (MOLL); medium C18:1+medium C18:2 (MOML); and high C18:1+low C18:2 (HOLL). Monensin feeding did not affect milk yield or concentration and yield of milk fat. Feeding monensin decreased the proportion of C <16, increased the proportion of total C18, increased the proportion and yield of trans-10 C18:1, and increased the proportion of trans-10,cis-12 conjugated linoleic acid in milk fatty acids (FA). As dietary C18:1 or C18:2 increased beyond the concentration present in LOLL, milk fat concentration, milk fat yield, and proportion and yield of milk C <16 all decreased, and the proportion and yield of milk trans-10 C18:1 increased. A quadratic effect on milk fat concentration and yield was noticed for C18:2 feeding, but not for C18:1 feeding. When dietary contents of total FA and FA other than C18:1 and C18:2 were similar, C18:2-rich diets decreased milk fat concentration and yield compared with C18:1-rich diets (LOML vs. MOLL, and LOHL vs. HOLL), indicating that C18:2 is more potent than C18:1 for depressing milk fat. Increasing dietary FA content from no fat to LOLL, which increased primarily C18:1 and C18:2 with small increases in C18:0 and C16:0, decreased the secretion of C <16 but increased total C18 secretion in milk. This suggests that biohydrogenation intermediates act to decrease mammary FA synthesis at low levels of added C18:1 and C18:2. No significant monensin × fat interactions were detected for the milk composition parameters analyzed; however, a monensin × fat interaction was found for milk fat trans-10 C18:1 proportion.

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)] on proteolytic, deaminative and methanogenic activities of mixed ruminal bacteria. Concentrations of total VFA were similar (P0.05) among treatments. With the exception of cinnamon and garlic oils, which reduced (PB0.05) the proportion of propionate, the other EO and EOC had no effect on the proportions of individual VFA, compared with the control. Proteolytic activity of ruminal bacteria was unaffected (P0.05) by treatments; however, bacterial deaminative activity and NH 3 concentration were increased (PB0.05) by the addition of EO (except for cinnamon leaf oil and garlic oil at 250 mg L(1 ) and EOC. Except for anethol, methanogenic activity of ruminal bacteria was reduced (PB0.05) by EO and EOC, which was reflected by a marked decrease in methane concentration. This study shows that at the concentrations evaluated, anethol, garlic oil (100 mg L(1 ), juniper berry oil, and p-cymene may not be beneficial to improve efficiency of N utilization in ruminants because they enhance deaminative activity, while cinnamon and garlic oil (250 mg L(1 ) could be good alternatives to antibiotics because they reduce methanogenic activity of ruminal bacteria.