Conducted by: Marsha Campbell Mathews, UCCE Farm Advisor, Stanislaus County and Peter Robinson, UCCE Dairy Nutrition Specialist, UCD
Grower: John Regusci, Modesto CA
Planting date: May 19, 1997
Soil type: Hanford sandy loam
Growing conditions: Excellent management with good fertility and irrigation
Trial Design: Randomized complete block with 3 replications harvested. Four 10' rows per plot, seven consecutive plants from the central portion of the best of one of the two middle rows were cut 4 inches from the ground. All 7 corn plants were chopped in a chipper-shredder and a subsample was taken for oven drying to determine moisture content. The remaining plant material was dried in the hot sun. Once dried, all the plant material from each plot was ground in a hammer mill, thoroughly mixed, and a sample taken for further grinding and analysis.
Variety |
Harvest Date |
Milk |
% |
% |
% |
% |
% |
IVTDMD |
Cargill F757 |
9/4 |
42% |
69.7 |
46.63 |
20.63 |
53.05 |
78.17 |
A |
DK 595 TC |
9/3 |
64% |
61.0 |
39.48 |
20.48 |
37.24 |
75.25 |
AB |
N7931 |
9/3 |
50% |
61.2 |
45.56 |
19.53 |
45.42 |
75.11 |
AB |
NC+ 6260 |
9/4 |
42% |
69.0 |
47.72 |
22.01 |
46.86 |
74.73 |
ABC |
FV 23018 |
9/3 |
47% |
65.3 |
47.00 |
21.21 |
45.52 |
74.36 |
BC |
Germains 4333 |
9/4 |
41% |
70.8 |
51.06 |
21.96 |
49.01 |
73.95 |
BC |
FV 2328 |
9/4 |
47% |
70.3 |
47.85 |
21.28 |
45.00 |
73.67 |
BC |
Pioneer 3245 |
9/4 |
33% |
65.4 |
46.31 |
23.16 |
45.16 |
73.20 |
BC |
Pioneer 3211 |
9/4 |
36% |
68.3 |
50.33 |
22.03 |
46.52 |
73.11 |
BC |
Gutwein 2656 |
9/4 |
53% |
70.8 |
51.88 |
22.12 |
47.85 |
72.97 |
BCD |
ST 7525 |
9/4 |
31% |
69.0 |
50.53 |
22.63 |
46.33 |
72.96 |
BCD |
Gutwein 2675 |
9/3 |
43% |
69.4 |
51.01 |
23.12 |
46.33 |
72.79 |
BCD |
Germains 4138 |
9/4 |
37% |
70.4 |
51.24 |
24.03 |
46.80 |
72.74 |
BCD |
N8214 |
9/4 |
44% |
70.3 |
48.53 |
22.15 |
43.34 |
72.59 |
BCD |
RX 938 |
9/5 |
32% |
71.1 |
54.20 |
23.89 |
48.77 |
72.23 |
BCD |
Ciba 4693 |
9/5 |
34% |
69.9 |
54.34 |
22.79 |
48.84 |
72.21 |
BCD |
RX 897 |
9/4 |
47% |
71.0 |
51.95 |
24.56 |
45.48 |
71.67 |
BCD |
DK7205 |
9/5 |
30% |
70.5 |
51.04 |
23.64 |
44.26 |
71.59 |
BCD |
C8511 FQ |
9/4 |
44% |
72.3 |
51.84 |
23.51 |
45.08 |
71.56 |
BCD |
ST 7624 |
9/4 |
38% |
71.8 |
49.99 |
23.84 |
42.37 |
71.21 |
CD |
NC+ 7665 |
9/5 |
39% |
68.9 |
52.30 |
25.01 |
44.68 |
71.12 |
CD |
Demand 118 |
9/5 |
27% |
72.2 |
52.07 |
25.11 |
41.25 |
69.41 |
D |
Coeff. Variation |
16.5% |
2.12% |
4.32% |
6.32% |
10.57% |
3.07% |
||
Probability |
0.0000 |
0.0000 |
0.000 |
0.0007 |
0.2075 |
0.0301 |
||
LSD @ 5% |
0.111 |
2.413 |
3.54 |
2.37 |
N.S. |
3.70 |
Explanation of Terms
Harvest Date: The corn plants were harvested on three consecutive days. The driest corns were harvested first. It was not possible to wait longer for immature varieties to mature further due to the need to harvest the field.
% Milk Line: Starch in a corn kernel is deposited first in the outer edge of the kernel beginning at the dent stage. As the corn matures, more and more starch is laid down. The progress of starch deposition, and corresponding kernel maturity, can be followed by looking at the boundary between the hard starch at the outer end and the softer part of the kernel towards the tip. This boundary is referred to as the milk line. In some hybrids the milk line is very distinct while in others it can be quite difficult to determine. Milk line was determined by breaking and evaluating a minimum of 5 ears in each plot at harvest. One third milk line is expressed here as 33%.
In this study, % milk line was poorly related to the percent moisture of the entire plant. While milk line may be a useful indicator of whole plant moisture within the same variety, hybrids may differ in drydown rate, staygreen characteristics, grain fill pattern, and response to growing conditions. This makes milk line a poor predictor of total plant moisture across varieties.
% Moisture: Whole plant moisture content at harvest. All quality analysis are reported on a 100% dry matter basis.
% NDF: The Neutral Detergent Fiber fraction of the plant is an estimate of the total structural fiber of the plant. The process of boiling a sample of the plant in neutral detergent removes starch, sugars, pectins, fats, most proteins and most minerals to leave only the NDF. The NDF is make up of hemicellulose, cellulose, lignin and cutin. It represents the slowly digestible portion of the plant. This procedure does not indicate the digestibility of the fiber, however, it is a valuable predictor of potential intake of the forage by dairy or beef cattle.
% ADF: Acid Detergent Fiber is the structural fiber that remains after a sample of the plant is boiled in and acidic detergent. The ADF is made up of only cellulose, lignin and cutin (i.e., a sub-fraction of NDF, without hemicellulose). The ADF proportion of a forage has long been considered to be the best estimate of potential digestibility by the animal.
The exact ADF values in this trial are a useful comparison between varieties in the trial but should not be compared to ADF values from other fields and/or trials.
% IVTDMD: In Vitro True Dry Matter Digestibility measures the digestibility of the entire corn plant by incubating samples of the plant in rumen fluid taken from a cow, then boiling the incubated samples in neutral detergent to ensure that all non-fiber portions of the sample are removed. This procedure estimates how much of the total dry matter in a silage corn is actually digestible by the cow. Since this process includes the digestibility of both the grain and the stover, increasing grain content with advancing maturity may mask decreases in stover digestibility as the crop matures.
% IVNDFD: The In Vitro Neutral Detergent Fiber Digestibility is calculated as the percent of the NDF that was digested in the In Vitro rumen fluid process. Hybrids which have high dry matter digestibilities due to higher percent grain because they were harvested more mature can be differentiated from those which have inherently better fiber quality by comparing the % IVNDFD. In this trial, % IVNDFD differences were not statistically significant among hybrids, but are still interesting.
LSD: Least Significant Difference is a way of determining if differences between hybrids are real or just a reflection of random variation within a field or analytical process. For example, if two hybrids in the IVTDMD column do not have any letters in common, you can be 95% sure that the difference between them in % IVTDMD are real differences in this trial. For the other columns in the table, look at the LSD value provided on the last line. If the two hybrids you are comparing differ by more than this amount, the difference between them is significant.
Conclusions
In this trial, most of the standard hybrids fell within the same broad range of total digestibility by all methods of measurement. Cargill F757 is a brown midrib hybrid, and had the best IVTDMD in the trial. The next two hybrids (DK 595 TC and N 7931) were also drier than the other hybrids, as reflected in the significantly lower moisture contents. One of these hybrids was significantly more mature that the other, and also had a lower NDF, indicating that a higher grain content probably accounted for the high IVTDMD.
November 5, 1999