1997 Stanislaus Winter
Forage Variety Trial

This trial was planted on November 14, 1996, using a small experimental plot planter.  Plots were 4 ft wide by about 20 feet long and all were planted at a seeding rate of 1 million seeds per acre.

Heavy rains followed within two days of planting. Although preplant fertilizer had been applied, rains in November, December and January washed out most of the nitrogen, leaving the crop severely nitrogen deficient. Because the crop was too short for lagoon water and there was no rain for flying on additional nitrogen, the crop remained short of nitrogen until mid February, when lagoon water was applied.  Consequently, good growth did not occur until about that time. Additional lagoon water was applied in subsequent irrigations later in spring.  There was little rainfall the entire spring.  The dry conditions were not conducive to the development of any of the foliar diseases.  Almost none of the plot showed any disease, and, since the site was protected by a small bluff, there was little lodging in this trial.  Caution should be used in choosing varieties solely based on performance under these conditions because they could respond much differently in a more normal year.

Beginning in late March, plots were harvested when each variety was determined to be at optimal harvest stage for yield and quality. Most oats were harvested at flower stage or slightly before as noted. The exceptions are the big, late oats which are designed to be cut at the boot to late boot stage.  Most of these were cut twice, once at a boot or pre-boot stage, and again when the florets were just breaking boot. Triticale and wheat were cut at the same stages as the big late oats. Some oats flower while still in the boot stage.  These were cut at what was determined to be an optimal harvest time for yield and quality depending on how early or late maturing they were.  A variety name followed by a (1) indicates this was the early cut of a variety cut twice, while a (2) shows this was the later cutting date for this variety.

Yields shown are the average of three randomized replications, and are adjusted to 70% moisture.  When comparing two varieties, check to see if they are followed by the same letter in the LSD column.  If they are not, then there is a 95% probability that the difference in yield between them in this trial is the result of true varietal differences, and not due to soil type, fertility, or other variations normally found in a field.

Many of these entries were tested for fiber digestibility using an in vitro true dry matter disappearance (IVTDMD) technique.  Fiber is a necessary component of a dairy cow ration, however, since stomach capacity is limited, it is desirable to have that fiber be as digestible as possible.  One way of evaluating fiber digestibility is to expose samples of the feed materials to the bacteria which are found in the rumen.  This can be done either by putting nylon bags of material into the rumen of a fistulated cow, or by laboratory incubation of samples in a solution of rumen fluid and microbial nutrients.

The IVTDMD values given here are from the second method, followed with an NDF determination.  This gives an estimate of the amount of dry matter remaining after digestion.  The lower the amount of material remaining, the better the digestibility of the plant fiber.  For example, for the Dirkwin wheat in this trial, 22.5% of the total amount of dry matter remained after 48 hour rumen digestion compared to 32.3% of the late harvested Ogle oats.  Presumably, the cow would get more nutrition from being fed Dirkwin wheat than from the same amount of Ogle oats.

The relative IVTDMD values within a trial are very useful for comparing varieties within that trial, however, caution should be used when comparing digestibility values from different trials because the methods used may be different.  In vitro digestibility values on cereals are not well correlated with the ADF or NDF fiber determination procedures.

For reference, a column comparing each digestibility with that of Kanota oats cut in the heading to early flower stage is included.  Kanota oat digestibility is set at 0, and those forages which are more digestible are positive and negative if they are less digestible.  Of the top three yielding varieties in the trial, two, Ensiler oats cut in the late boot, and Longhorn wheat cut at 50% heading, have about the same digestibility as early flower Kanota oat.  The third, UC 126, an experimental University of California oat, had 18.6% better digestibility than Kanota.

The ranking number (in parenthesis) gives the ranking from most to least in digestibility of the forages tested.  Cayuse oat cut at a pre-boot stage was most digestible and Mortlock oat cut in the milk stage was least.

The laboratory method used to determine digestibility requires that the feed samples be finely ground before testing. This disguises differences which exist in the feedbunk due to chop length, stem size, or preservation method.  All of these can impact feed intake and animal performance. For this reason, IVTDMD can at best give only a prediction of how forages will perform when fed.  In the end, the cow is the best judge.

There were no significant differences in percent crude protein in this trial, probably because the late irrigations with lagoon water put differing amounts on nitrogen on different areas of the plot.  As expected, protein levels in later cuttings were lower than those of comparable early cuttings.

Montezuma, Swan and Kanota oats were harvested on the early side in last year's trial, contributing to the poor yields of these varieties.  Several of the varieties harvested in the late boot to very early heading stage made outstanding tonnage, especially considering the poor start to the season.  Most of these were equal to or better than early flower Kanota oat in digestibility, while making much higher tonnage.  Gene wheat did very poorly in this trial because the late planting and lack of fertilizer until late in the season prevented the early growth essential for this type of winter wheat.

November 5, 1999