Thursday, July 24, 2014

Good Pasture Quality

During the parasite-challenge phase of the test, three pooled fecal samples were collected and submitted to the Grazingland Animal Nutrition (GAN) Lab in Temple, Texas.

The GAN Lab uses near infrared spectroscopy (NIRS) to evaluate the forage component of an animal's diet and predict the quality of the forage the animals were consuming for the past 36 to 48 hours.

These results show that the goats were grazing good quality pasture during the parasite-phase of the test. The only limiting factor would have been intake.

An explanation of the data
Crude protein (CP) analysis measures grams of crude protein per gram of dry matter in the manure and reflects the crude protein percentage in the diet that the goats were consuming. Digestible organic matter (DOM) measures grams of digestible organic matter per gram of dry matter in the manure. It is a measure of digestible energy. The DOM/CP ratio is an indicator of rumen efficiency. For cattle, the acceptable range for this ratio is 4 to 7 with 4 being optimal.

Fecal nitrogen (FN) is a direct measurement of the amount of nitrogen in the manure and is not necessarily correlated to dietary nitrogen. FN can be used to roughly quantify the amount of nitrogen going back onto the pasture where the animals are grazing.

Fecal phosphorus (FP) analysis  measures the percent of phosphorus (P) in the manure itself and can be used to roughly gauge if dietary P is adequate. A FP value greater than 0.3 generally indictes that dietary phosphorus intake is adequate.  A value between 0.3 and 0.2 is borderline and may need attention.A value less than 0.1 indicates a potential deficiency.

Source:  NIRS Report, Grazingland Animal Nutrition Lab, 7.23.14

Goats are not Cattle

According to Dr. Stephen Prince, Director of the GAN Lab, more than 95 percent of the samples processed in his lab are from cattle. Because the lab's equations and calibrations are for cattle, there may be some differences in the data for goats and other livestock species.

This was the third rotation in the parasite-challenge phase.

In a phone conversation, Dr. Prince indicated that the cattle equations may underestimate DOM for goats, which would help to explain the lower DOM and DOM/CP ratios. While the report stated that the ratios for the test samples would be "outside the range for positive rumen efficiency," this is not necessarily the case with goats, he said. Goats are not cattle!  However, the way to improve the DOM/CP ratio would be to supplement the pasture diet with a source of energy. This is exactly what we are doing with the soy hulls.

Collecting additional samples
Additional pooled fecal samples will be collected from the goats during the growth-phase of the test, while they are grazing the warm season annual grasses and legumes. The samples will be submitted to the GAN Lab for NIRS analysis.