Feed degradability,rumen fermentation and blood metabolites in response to essential oil addition to fistulated non‐lactating dairy cow diets

The effects of essential oils (EOs) on ruminal nutrient disappearance, rumen fermentation and blood metabolites in fistulated non‐lactating dairy cows were studied. Four fistulated non‐lactaing dairy cows were used in a 4 × 4 Latin square design; the experiment consisted of four periods of 21 days in each period, with the first 14 days for adaptation followed by 7 days of measurement period. Animals were fed 3 kg/day of 21% crude protein (CP) concentrate and ad libitum corn silage. Treatments were: (i) control; (ii) 2 mL Allicin/cow/day; (iii) 2 mL zingiberene/cow/day; and (iv) 2 mL citral/cow/day. The results demonstrated that EOs increased dry matter and neutral detergent fiber degradabilities at 48 and 72 h, but had no effect on acid detergent fiber and CP degradabilities. EOs did not change ruminal pH, ammonia nitrogen, protozoa, volatile fatty acid concentrations and blood glucose but reduced blood urea nitrogen at 4 h.     

Use of fibrolytic enzymes additives to enhance in vitro ruminal fermentation of corn silage

Two experiments were conducted to evaluate the effect of four enzyme additives on ruminal fermentation of corn silage using a 48 h batch culture in vitro assay with buffer and ruminal fluid. Experiment 1 (Exp. 1) and Experiment 2 (Exp. 2) were conducted as completely randomized designs each with two runs and four replicates. The enzyme additives (E1, E2, E3, and E4) were commercial products that provided a range in endoglucanase, exoglucanase, and xylanase activities. For both xylanase (birch wood and oat spelt substrate) and endoglucanase (carboxymethylcellulose substrate), the enzyme products (per ml) were ranked E4>E1>E2>E3. In Exp. 1, the four enzymes were added at 0, 2, 4, and 8 μl/g of corn silage dry matter (DM), whereas in Exp. 2 enzymes were added at 0, 0.5, 1, 2, and 4 μl/g DM. Gas production (GP) was measured at 3, 6, 12, 18, 24, and 48 h after incubation. Disappearance of DM (DMD), neutral detergent fiber (NDFD), and acid detergent fiber (ADFD), and volatile fatty acid concentrations (VFA; total and individual molar proportions) were determined after 24 and 48 h. In Exp. 1, E1 and E2 had higher NDFD and ADFD at 24 and 48 h of incubation (P<0.001) compared with E3 and E4. Increasing dose rate increased NDFD and ADFD for all enzymes (except ADFD for E4 at 48 h), with the optimum dose rate dependant on the enzyme additive (dose×enzyme; P<0.01). There were some treatment effects on DMD and total GP at 24 and 48 h, but these responses were not consistent with responses in NDFD and ADFD. Experiment 2 was conducted to confirm the effects and optimum dose rate of each enzyme additive. In Exp. 2, DMD was not affected by enzyme after 24 and 48 h incubation. There were no enzyme×dose interactions for DMD, NDFD, or ADFD after 24 or 48 h of incubation (except for ADFD at 48 h). After 24 h, DMD, NDFD, and ADFD increased linearly with increasing dose (P<0.05); after 48 h DMD increased linearly, whereas NDFD increased quadratically with increasing enzyme dose (P<0.05). The ADFD increased linearly after 48 h for E3 and E4, but after 48 h ADFD increased quadratically for E1 and E2. Total GP was consistently lowest for E4 at both incubation times (P<0.05). There were no enzyme×dose interactions (P>0.05) for any of the fermentation variables at either 24 or 48 h of incubation in Exp. 2. There were differences amongst the additives for total VFA at 24 and 48 h (P≤0.05); increasing enzyme dose decreased total VFA after 24 h but increased total VFA at 48 h, such that all doses were higher than the control (P<0.001). Overall, the enzyme additives increased NDFD and ADFD of corn silage in vitro; however, E1 and E2 were more effective than E3 or E4. Responses to increasing dose of enzyme were generally linear or curvilinear, and the optimum dose rate differed amongst the products evaluated. Evaluation of the enzymes at 24 and 48 h generally led to the same ranking of the additives, and the degradation of NDF and ADF was more useful in differentiating the enzymes compared with DM and total GP.     

Effect of linseed oil supplementation on performance and milk fatty acid composition in dairy cows

Thirty‐six Holstein‐Friesian crossbred lactating dairy cows were used to determine the effects of linseed oil supplementation on performance and milk fatty acid (FA) profile. Three treatments were as follows: basal diet (56:44 Roughage:concentrate [R:C] ratio, dry matter basis) supplemented with 500 g of palm oil as control (PO), 500 g mixture (1:1, w/w) of palm oil and linseed oil (POLSO) and 500 g of linseed oil (LSO). The LSO supplementation had no effects on total dry matter intake (DMI), milk yield and milk composition. Compared to control cows, cows supplemented with LSO increased milk concentrations of cis‐9,trans‐11 conjugated linoleic acid (CLA) and n‐3 FA (P < 0.05), particularly C18:3n‐3, C20:5n‐3 and C22:6n‐3. Feeding LSO reduced concentrations of milk short‐ and medium‐chain saturated fatty acids (P < 0.05) while it increased concentration of milk unsaturated fatty acids (P < 0.05). Milk proportions of n‐3 FA increased, whereas n‐6/n‐3 ratio decreased in the LSO as compared with the control (P < 0.05). In conclusion, supplementing dairy cows' diet based on corn silage with LSO at 500 g/day could improve the nutritional value of milk with potential health‐beneficial FA without detrimental effect on milk composition or cow's performance.     

Goat cathelicidin‐2 is secreted by blood leukocytes regardless of lipopolysaccharide stimulation

It has been reported that goat cathelicidin‐2, an antimicrobial peptide, localizes in leukocytes and is present in milk. Here, we examined whether cathelicidin‐2 is secreted by leukocytes. Different concentrations (10⁵–10⁸ cells/mL) of blood leukocytes were cultured for 0–48 h with or without lipopolysaccharide (LPS). After culture, the concentrations of cathelicidin‐2 in the conditioned media were measured. Blood was collected from male goats 0–24 h after the intravenous injection of Escherichia coli O111:B4 LPS. The plasma cathelicidin‐2 concentrations were determined and the blood leukocytes immunostained with anti‐cathelicidin‐2 antibody to calculate the proportion of cathelicidin‐2‐positive cells in the total leukocytes. When higher concentrations of leukocytes were cultured, the cathelicidin‐2 concentrations in the media increased significantly, whereas the addition of LPS to the media caused no further increase. The plasma cathelicidin‐2 concentrations did not increase with time after LPS infusion. The proportion of cathelicidin‐2‐positive cells in the total leukocytes was significantly reduced 1 h after LPS injection compared with that at 0 h, but increased again at 6 h and thereafter. These results suggest that cathlicidin‐2 is secreted by leukocytes even without LPS stimulation, whereas LPS may be required for cathelicidin‐2‐containing leukocytes to be recruited from the blood to tissues showing inflammation.