1598
Ruminal in situ DM and starch digestion descriptive statistics of corn silage and high moisture corn
Starch comprises 20%-35% of dry matter (DM) in diets for lactating dairy cows. Ruminal starch digestibility is highly variable across and within feed types. Our objective was to determine ruminal in situ starch digestibility (StarchD) for corn silage (CS; n=52) and high moisture corn (HMSC; n=41) samples. Samples were dried at 50°C in a forced air oven for 48 h and ground to pass through a 1-mm Udy Mill screen for DM and starch analysis, or a 6-mm Wiley Mill screen for ruminal in situ analysis. Rumen in situ samples were weighed with 3g per bag in an Ankom 5x10cm bag (50µm pore size) in triplicate. Bags were soaked in warm water prior to incubation. One bag was placed in three different ruminally-cannulated lactating dairy cows consuming a 58% forage diet with a 50:50 ratio of corn silage to legume (DM basis). Samples were incubated for 3 and 7 h; all bags were removed simultaneously. Following incubation the bags were rinsed until effluent was clear. Bags were dried at 50°C for 24 h and weighed to determine the DM digestibility (DMD). Residue samples were composited and ground to pass a 1-mm Udy Mill screen. Starch content was then determined according to a modified M.B. Hall 2008 procedure using an YSI2700 (YSI Life Sciences On-Line Biochemistry Analyzer), to determine glucose after samples were enzymatically digested, instead of theglucose oxidase–peroxidase procedure. StarchD was calculated as the difference in grams of starch remaining in the residue, relative to the grams of starch in the sample. DMD and StarchD descriptive statistics were analyzed using SAS JMPv10 and are presented in Table 1. Ruminal in situ StarchD was highly variable for HMSC and CS.
Table 1. Rumen in situ 3 and 7h Descriptive statistics of DMD and StarchD
Type |
Hour |
Mean |
St.dev. |
Min. |
Max. |
C.V |
Dry Matter Digestion (%) |
||||||
HMSC |
3 |
40.3 |
16.6 |
19.0 |
82.5 |
41.2 |
HMSC |
7 |
50.6 |
12.8 |
28.8 |
86.6 |
25.3 |
CS |
3 |
41.6 |
10.2 |
15.5 |
57.5 |
24.5 |
CS |
7 |
48.4 |
8.4 |
22.3 |
66.9 |
17.4 |
Starch Digestion (%) |
||||||
HMSC |
3 |
47.1 |
15.0 |
26.0 |
91.2 |
31.8 |
HMSC |
7 |
58.2 |
12.9 |
36.6 |
91.3 |
22.2 |
CS |
3 |
64.7 |
18.6 |
0.9 |
88.2 |
28.7 |
CS |
7 |
77.0 |
14.5 |
16.8 |
93.8 |
18.8 |
Keywords: rumen, starch, digestion