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Nutritional Evaluation of Forage Ephedra (Ephedra nevadensis) As an Alternative Forage Using a Dual-Flow Continuous Culture System
Nutritional Evaluation of Forage Ephedra (Ephedra nevadensis) As an Alternative Forage Using a Dual-Flow Continuous Culture System
Wednesday, July 12, 2017
Exhibit Hall (Baltimore Convention Center)
Forage ephedra (Ephedra nevadensis; ephedra) is well adapted and grazed by sheep and cattle in the Western US; however, its nutritional value has not been well established. The objective of this study was to determine ruminal digestibility, ruminal microbial fermentation, and bacterial N synthesis of ephedra as compared to cheatgrass (Bromus tectorum; CG) and orchardgrass hay (Dactylis glomerata L.; OGH). Diets were randomly assigned to 6 fermenters in a dual-flow continuous culture system in a 3 × 3 Latin square design with three 10-d experimental periods consisted of 7 d for diet adaptation and 3 d for sample collection. Fermenters were fed a total of 72 g of dry matter/d equally divided in 2 portions per day. Diets were: 1) 100% air-dried ephedra, 2) 100% air-dried CG and 3) 100% air-dried OGH. Liquid and solid dilution rates were adjusted daily to 10% and 5%/hour, respectively. A 500 mL sample was taken on 8, 9, and 10 d and analyzed for nutrient digestibility and microbial growth. Two 10 mL subsamples were filtered through two layers of cheesecloth and preserved with 0.2 mL of 50% sulfuric acid and 2 mL of metaphosforic acid for subsequent ruminal NH3–N and VFA analyses, respectively. Statistical analysis was performed using the PROC Glimmix procedure of SAS. Partial data are presented in Table 1. The NH3-N concentration was greater for CG followed by ephedra and lowest for OGH (P < 0.01). Ruminal pH was greater for ephedra (P < 0.01), while total VFA was the lowest (P < 0.01). Ephedra had greater acetate molar proportion, which resulted in the greatest acetate: propionate ratio (P < 0.01). Ephedra also had the lowest propionate molar proportion. Results from this study indicate that ephedra should not be used as the main forage in cattle diets due to its poor fermentation as evidenced by the lowest total VFA and propionate molar proportion.
Table 1.
|
Treatments |
|
|
||
Item |
Ephedra |
CG |
OGH |
SEM |
P-value |
pH |
7.73a |
6.78b |
6.83b |
0.16 |
< 0.01 |
NH3-N mg/dL |
8.59b |
18.09a |
3.47c |
0.93 |
< 0.01 |
VFA, mmol |
37.77c |
86.87a |
77.54b |
3.18 |
< 0.01 |
Acetate, % |
74.33a |
69.70b |
58.94b |
1. 50 |
< 0.01 |
Propionate, % |
17.10b |
20.82b |
24.54a |
1.31 |
< 0.01 |
Butyrate, % |
7.42b |
8.37b |
13.26a |
1.28 |
< 0.01 |
Valerate, % |
0.28 |
0.72 |
0.62 |
0.19 |
0.47 |
Acetate: propionate |
4.77a |
3.48ab |
2.25b |
0.42 |
< 0.01 |