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Superintendent
David Davis
21262 Genoa Road
Linneus, MO 64653
Phone: 660 895-5121
FAX: 660 895=5122
Email: DavisDK@missouri.edu

Forage Systems Update
Vol 15, No. 1

Objectives: To increase the rate of gain and weaning weight of nursing beef calves in Missouri.

Procedure: Several large tall fescue (K31, endophyte infected) pastures were selected at the Forage Systems Research Center near Linneus in March, 2005. Pasture selection was based on low to moderately low soil Bray I phosphorus analysis (Table 1). Pastures were also selected and organized into treatments groups that would be located close together for convenient pasture rotation. Treatments were 0 or 50 lbs P/acre, 100 lbs N/acre/yr and K was added as recommended by the soil test results. All cattle were supplied with free choice salt blocks containing only NaCl. At least four replicated pastures were selected for each treatment and pastures size averaged about 15 acres. In the original proposal, I stated that each pasture will be supplied with at least six beef cow/calf pairs (crossbred cows with Red Angus calves). But we decided that it would be easier and cost much less for fencing and management to use most of the FSRC spring-herd in this study, consequently, we used 150 cow/calf pairs. Therefore, each replicate treatment had 25 cow/calf pairs and at least four different pastures. Calving of this herd began around February 1 and ended around March 15. About 90% of the calves were siblings from the same (AI) Red Angus bull. Cows were preconditioned on similar tall fescue pastures for at least four weeks prior to the beginning of this experiment. On April 14, 2005, cows and calves were weighed and placed in the appropriate test pastures. Stocking rates were adjusted to produce similar grazing pressures on the various pastures. The amount of forage available was determined by using 50 measurements with an Elinbank Rising Plate meter. The forage meter readings were calibrated with monthly forage harvests taken with a flail-type forage harvester. Using the forage harvester, we harvested, weighed and sub-sampled forage from ten 32" x 15' cuts from one pre-grazed pasture and one post-grazed pasture in each replicate set of pastures. Sub-samples grabbed from each of the 10 harvested samples were pooled, dried, and stored for determination of quality components and mineral elements. Cows and calves were to be weighed monthly for six months, or at least that was the plan. The study was terminated after four months because of drought conditions. Even though we had included extra pastures in the study, the severe dry weather resulted in almost no available forage for grazing by August. Therefore we had to terminate the study after four months, instead of the proposed six months.

Results: The Forage Systems Research Center is an excellent site for this type of research. We were able to locate adequate number of low P pastures on the Center to accommodate this large scale study. This Center has a great cow herd and the genetics of the calves is top-notch, plus the facilities are readily available for weighing the cows and calves frequently. Also, agronomists and animal scientists are available for helping collect forage samples, for rotating cattle through pastures, and for weighing and caring for the cattle. One difference between this study and a preliminary study that we had conducted at the SW Center near Mt. Vernon, was the cows in the current study calved earlier, therefore calves went into the P study when they were over one month of age. At the SW Center calves were actually born around the day the experiment began. The major problem with the study this year was the lack of rainfall. The lack of precipitation may have nullified the usefulness of the P fertilization, and by July, had lowered the soil test K levels in many of the pastures (Table 2). There were no P treatment differences in rate of gain or final weight of the calves or cows this year (Tables 3 & 4). We are currently analyzing the most recent soil test data to re-evaluate each pasture in the study to make sure that pastures in the low P treatments are really low enough for the study. We are also calculating total NPK needs for each pasture for the second year. Another 50 lbs of P will be added to the high P pastures, but we are trying to determine how much K to add to pastures in order to make them equivalent in K levels.

Table 1. March 27, 2005 soil test data from pastures used in the phosphorus cow/calf study at the Forage Systems Research Center. Each value is the mean of data from all of the pastures within a particular treatment group, usually at least four different pastures.

Table 2. July 27, 2005 soil test data from the pastures used in the phosphorus cow/calf study at the Forage Systems Research Center. Note that soil K levels are markedly lower in most of the pastures as a result of the drought. Each value is the mean of data from all of the pastures within a particle treatment group, usually at least four different pastures.

Table 3. The 2005 calf performance on high and low phosphorus pastures at the Forage Systems Research Center. Start weight was on April 14, Period 1 weight was on May 12, Period 2 was on June 9, Period 3 was on July 5 and Period 4 weights were taken on August 9 and again on August 10. At the end of the experiment, the calves and cows were weighed on two consecutive days. Values are means of weight from 75 calves in the treatment.

Table 4. The 2005 cow performance on high and low phosphorus pastures at the Forage Systems Research Center. Periods 1, 2, 3 and 4 are the same as those described in the legend of Figure 3. Values are means of weight from 75 cows in the treatment.