Abstract #T369

Section: Ruminant Nutrition
Session: Ruminant Nutrition: Beef II
Format: Poster
Day/Time: Tuesday 7:30 AM–9:30 AM
Location: Gatlin Ballroom

# T369
Effects of energy and nitrogen supplementation of cheatgrass on ruminal fermentation using a dual-flow continuous culture system.
Lorrayny Galoro da Silva^*1, Farnaz Malekjahani^1,4, Pedro Del Bianco Benedeti^1,2, Eduardo Marostegan de Paula¹, Teshome Shenkoru¹, Paloma de Melo Amaral^1,2, Lays Mariz^1,2, Hugo Monteiro^1,3, Antonio Faciola¹, ¹University of Nevada, Reno, NV, ²Federal University of Viçosa, Viçosa, MG, Brazil, ³Maringa State University, Maringa, PR, Brazil, ⁴Ferdowsi University, Mashhad, Iran.

Cheatgrass (CG; Bromus tectorum), an annual grass that is one of the main components of sagebrush community in Western US contributes to the fuel-load for wild fires. One fuel-reduction strategy is livestock grazing. The objective of this study was to determine the effects of molasses and urea supplementation on a CG-based diet on ruminal digestibility, rumen microbial fermentation and bacterial N synthesis. Diets were randomly assigned to 8 dual-flow continuous culture fermenters in a 2 × 2 factorial arrangement of treatments (urea and molasses) in a 4 × 4 Latin square design with four 10-d experimental periods consisted of 7 d for diet adaptation and 3 d for sample collection. Fermenters were fed 72 g/d of DM divided in 4 portions of 1 of 4 diets: CG, CG plus urea (CGU), CG plus molasses (CGM), and CG plus urea and molasses (CGUM). Liquid and solid flow rates were adjusted to 10 and 5%/h; respectively. A 500-mL sample was taken on d 8, 9, and 10 and analyzed for rumen traits, nutrient digestibility, and microbial growth. Data were analyzed in SAS. Partial data are presented in the table. The NH₃-N concentration was higher in the diets containing urea, indicating a higher N availability for microbial growth. Total VFA concentration was not increased by molasses; however, it was lower when urea alone was added. Acetate molar proportion decreased when molasses alone was added. However, propionate molar proportion was increased when molasses was added. Results from this experiment indicate that CG utilization is improved by a combination of N and energy supplementation, which may reduce CG fuel-load in areas where CG is widely spread. Table 1.

Item	Treatment				SEM	P-value
CG	CGU	CGM	CGUM
NH₃-N, mg/dL	3.19^c	21.49^a	0.82^c	13.75^b	0.94	<0.01
Total VFA, mmol	60.34^a	38.85^b	67.05^a	68.59^a	3.31	<0.01
Acetate, %	72.36^a	73.73^a	66.16^b	65.95^b	1.56	<0.01
Propionate, %	19.17^b	19.66^b	24.40^a	25.38^a	1.49	<0.01
Butyrate, %	8.12^a	6.03^b	9.12^a	8.10^a	0.64	0.02
Isobutyrate, %	0.05^b	0.38^a	0.06^b	0.03^b	0.07	<0.01
Valerate, %	0.04	0.02	0.16	0.04	0.05	0.23
Isovalerate, %	0.04^ab	0.02^b	0.21^a	0.04^b	0.05	0.07
Acetate:Propionate	3.26^ab	3.98^a	2.83^b	2.66^b	0.28	0.02
Total BCVFA, %	0.05	0.14	0.17	0.04	0.04	0.13

Key Words: cheatgrass, continuous culture, molasses