Abstract #M279

Section: Ruminant Nutrition
Session: Ruminant Nutrition I
Format: Poster
Day/Time: Monday 7:30 AM–9:30 AM
Location: Exhibit Hall B

# M279
Nutritive value of common feedstuffs fed to dairy cows measured using the in vitro gas production technique.
K. Mjoun^*1, L. Shearer¹, B. Kubat¹, ¹Alltech, Brookings, Sd.

The fermentation parameters of feedstuffs commonly fed to dairy cows were evaluated using the in vitro gas production technique. Feeds were grouped into different categories; corn silage (n = 15), small grains silages (n = 15), alfalfa hay (n = 11), alfalfa haylage (n = 4), byproducts (n = 20); protein meals (n = 7), energy feeds (n = 17), and lactation TMR (n = 12). Incubations (48h) were completed using rumen fluid from a lactating cow fed a 50:50 forage to concentrate diet. The fermentation kinetics were estimated using a logistic model separating gas production per 1 g of DM truly digested into fast pool (FP), slow pool (SP) and their respective rates of fermentation (FR) and (SR) (Table 1). Grain silages produced the most gas (GP) mainly from the SP. Protein meals had the highest FP:SP and haylage had the highest fermentation rates. The partitioning of digested DM into gases, VFA, and microbial protein (MPS) suggests that the fermentation efficiency (Y_ATP) is highest for protein feeds, alfalfa forages and TMR, intermediate for energy feeds, byproducts and small grains silages, and lowest for corn silages.

	Corn silage	Small grains silage	Alfalfa haylage	Alfalfa hay	By-products	Protein meals	Energy feeds	Lactation TMR	SEM
FP, mL	78.4^c	115.2^a	79.9^c	85.2^c	100.8^b	104.3^ab	73.5^c	74.5^c	8.13
FR, %/h	23.6^a	18.5^c	27.4^a	18.7^bc	18.1^c	17.4^c	14.9^c	22.8^ab	2.65
SP, mL	236.7^a	230.9^a	158.4^bc	151.1^c	169.2^bc	109.4^d	174.0^b	176.5^b	10.9
SR, %/h	4.65^bc	4.17^d	5.51^a	4.87^b	4.54^bc	4.41^cd	3.45^e	5.30^a	0.24
GP, mL	251.6^ab	260.5^a	209.1^de	202.8^e	239.2^bc	203.1e	232.4^cd	214.5^de	11.6
FP:SP	0.34^c	0.51^c	0.51^c	0.57^b	0.62^b	0.95^a	0.43^c	0.43^c	0.06
TDMD, %	73.4^d	63.7^e	81.9^bc	78.0^c	82.5^b	90.8^a	91.5^a	79.4^bc	2.67
VFA, mM	26.1^bc	21.4^d	25.8^bc	24.7^c	28.3^b	29.1^ab	31.2^a	24.1^cd	1.79
Acetate, %	38.6^d	48.4^b	56.6^a	55.7^a	45.4^b	43.9^bc	28.4^e	40.2^cd	2.80
Propionate, %	32.7^cd	30.6^d	23.0^e	25.3^e	33.3^bc	31.3^cd	41.1^a	35.5^b	1.64
Butyrate, %	23.1^a	15.1^cd	9.9^e	11.3^e	16.1^c	13.7^d	22.5^a	18.1^b	1.11
MPS, mg	138^d	162^d	273^abc	275^ab	212^c	320^a	249^bc	270^abc	31.30
Y_ATP	9.6^d	15.2^bc	20.4^ab	22.9^a	14.1^c	23.0^a	22.5^a	18.1^b	2.73
CH4, mL/g DM	41.1^ab	42.6^a	47.5^a	43.6^a	36.2^bc	37.1^abc	26.8^d	31.5^cd	4.21

^a–cValues with different superscripts within the same row differ at P < 0.05.

Key Words: in vitro, rumen, feedstuffs