| | Many areas of Western Canada have come through a dry summer, and, in some areas of Alberta and Saskatchewan, weather conditions have reduced perennial and annual forage production by 75 per cent. This means that forage costs have increased dramatically from the previous year, and farmers are trying to optimize the use of their feed resources.
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"Mixing feeds is one way producers can stretch their feed supply," says Barry Yaremcio, beef and forage specialist, Alberta Agriculture and Rural Development. "To do this efficiently, feed testing each forage type and grain is required. With tight economic times in the cow calf sector, many producers have turned to the Near Infrared Red Spectroscopy (NIRS) system for analysis instead of wet chemistry. This change reduces costs by approximately $40 per forage sample submitted, and turn-around time is significantly reduced when NIRS is used."
In dry years, plants mature more rapidly than in a normal year. A lack of moisture restricts total plant growth and the amount of starch or sugar deposited. Dry conditions restricts the plants' ability to get calcium and other nutrients out of the soil, thus mineral content in plants is also reduced. Also, acid detergent fibre and neutral detergent fibre levels increase more rapidly in the plants than in a year with normal moisture, which further reduces overall energy content in the forage.
"When producers are dealing with production problems associated with dry conditions, feed testing is essential, which is what makes NIRS so attractive," says Yaremcio. "NIRS measures the nutrient content of forages and grains by the amount of light that is absorbed or reflected off the sample. Light energy absorbed by the hydrogen-containing bonds in the feed is measured by the machine and the scan results are related through statistical correlation and calibration equations, to predict the nutritional content of the feed."
To develop calibration curves for the NIRS system, reference samples are analyzed by wet chemistry. These reference samples are from a wide range of locations, different stages of plant maturity and environmental conditions. The accuracy of NIRS predictions depends on the calibration curves developed from the reference samples. NIRS results for protein, acid detergent fibre (ADF) and neutral detergent fibre (NDF) of forages are used widely in North America for ration-balancing purposes.
When testing feed, a note of caution must be acknowledged. Measuring mineral composition (calcium, phosphorus, magnesium, potassium, and sodium) by NIRS is less precise and more problematic than wet chemistry. These nutrients do not absorb light in the near infrared spectrum unless they are bound in a molecule which contains a hydrogen bond. Unlike CP and ADF, NIRS is not recognized as an official method for determining the mineral content in forages by the Association of Official Analytical Chemists (AOAC).
Test results for calcium, phosphorus and magnesium must be considered carefully before values are used for ration balancing purposes.
To illustrate methodology can impact test results, portions from the same sample of a barley greenfeed grown under drought conditions was analyzed by both NIRS and wet chemistry. Results are in the table below. Reported concentrations for calcium, phosphorus and magnesium were considerably different between wet chemistry and NIRS while the potassium and sodium results are identical (see chart below).
Reported concentrations differ between wet chemistry and NIRS
| Nutrient | Protein | ADF | NDF | Calcium | Phosphorus | Magnesium | Potassium | Sodium |
| NIRS | 13.80 | 28.38 | 50.88 | 0.45 | 0.38 | 0.23 | 0.98 | 0.02 |
| Wet Chemistry | 13.82 | 25.57 | 48.60 | 0.16 | 0.20 | 0.12 | 0.96 | 0.02 |
If a cow calf producer was to provide this barley greenfeed as the sole feed after calving using the NIRS results, a lactating cow would require 113 grams (4 ounces) of limestone per head per day to maintain a 2:1 calcium to phosphorus ratio. Phosphorus and magnesium levels appear to be sufficient when using Cowbytes to balance the ration.
When the wet chemistry results are used, feeding the same ration, on a per head per day basis, 50 grams (1.75 ounces) of a 2:1 mineral is needed to increase the phosphorus content in the ration, along with an additional 95 grams (3.3 ounces) of limestone to have a 2:1 calcium to phosphorus ratio. Magnesium is deficient and 23 grams (0.8 ounces) of magnesium oxide is required per head per day.
"Calcium and phosphorus are the two most important macro minerals in a beef ration," says Yaremcio. "If the amounts of calcium and phosphorus are not in the proper ratio with calcium being deficient; weight gains can be reduced in growing animals. For mature cows fed a calcium deficient ration you may experience the following conditions: milk fever or downer cows; reduced milk production; winter tetany; stillborn calves; and, retained placentas. Calcium can be mobilized from the cows' bones which can cause osteoporosis.
"If phosphorus is deficient in the ration, feed intake can be reduced resulting in lower milk yield in cows and growth rates in calves. Additional cow concerns are silent heats, longer times to start cycling and low conception rates in cows. A phosphorus deficiency related production problem will be noticed quicker than a calcium deficiency. To prevent tetany problems, 23 grams (0.8 ounces) of magnesium oxide is also required per head per day."
There can be large discrepancies in feed test results among the analytical systems. Depending on which results are being used, the supplementation program required can be considerably different and have impact on the long term performance of the cow herd. Consult with a nutritionist, or extension agent, to obtain a second opinion of what is required to provide a balanced supplementation program.
Contact:
Barry Yaremcio
310-FARM (3276) |
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