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Here’s How Wet Weather Affects Feed Quality

Last year, Alberta beef and forage specialist Barry Yaremcio was fielding all sorts of drought-related questions about balancing rations when utilizing various alternative feeds and supplements. Come spring, producers who hadn’t balanced rations were dealing with impaction problems, thin cows, downer cows, and weak calves with poor immunity.

It’s the reverse this year. Most regions across the Prairies have received above-average precipitation and forage quantity is ample. “Quality will be the big concern. Either the hay was cut early and rained on at least a couple of times; or, it was left standing during the bad weather and cut two to four weeks later than normal, making it over mature,” he says.

Yaremcio cites numerous studies showing that high moisture conditions at the time of baling and during storage reduce the quality of forages. The losses are due to physical damage, chemical reactions within the bales and nutrient leaching.

A New Zealand study showed losses of 30 to 40 per cent of the original dry matter in the bales stored uncovered for five months and 14 inches of rain. In Kentucky, dry matter losses equated to nine per cent of total bale weight when the bales were stored unprotected for five months.

Digestibility of hay is also reduced in bales exposed to wet weather. Results from a study looking at this question indicate digestibility decreases by one-half per cent for every one per cent increase above 20 per cent moisture content in the bale. This held true whether the bale was stored in a shelter or outside.

When bales get wet, the soluble carbohydrate and protein leach out of the forage, lowering the energy and protein content while increasing the total fibre content and reducing the digestibility of the hay, he explains.

It’s the opposite scenario when heating occurs. The soluble protein becomes indigestible when it attaches to the neutral detergent fibre. This happens as a result of a chemical reaction that occurs when the temperature in the bales or silage begins to rise above 35 C. The sugars become solublized as well, giving the hay a sweet taste that cattle love. The caramelized hay won’t hurt the animals, Yaremcio says, it’s just that there won’t be as much available protein and energy in the forage as you may have expected.

A study at the Agriculture and Agri-Food Research Station in Swift Current, Sask. showed that there was 23 per cent more spoilage in hard-core round bales than in soft-core bales. The soft-core bales allowed for moisture and air movement and were less likely to heat in the centre.

Most of the physical damage occurs in the outside five inches of the bale. That may not seem like a lot until you consider that the outer five inches of a five-foot-diameter round bale account for 30 per cent of the total bale weight. The cows may refuse to eat this weathered, mouldy feed.

Yaremcio’s message for producers is to be aware of declining nutritive value in weathered bales when you are working with a feed consultant this year. Consider when the feed tests were taken and how the bales have been stored. A second feed test later on in the winter may be timely, especially if the rainy weather persists this fall.

THREE WAYS TO PROTECT YOUR BALES 1. Stacking in a row

The best way to store round bales to minimize spoilage is to place them on their round sides in a single row with six to 10 inches of space between the flat ends of the bales. The mushroom stack, with the bottom bale on its flat end and the top bale on its round side, creates problems because moisture drips from the top bale right into the flat end of the bale beneath. Pyramid stacks are the most prone to damage because the moisture from the top bale wicks around to the bales in the middle row, and from there to the bales in the bottom row.

Compared with bales stored under cover, consumption was 34 per cent lower when cows were given hay free-choice from bales that had been mushroom stacked, and 37.5 per cent lower for hay from bales that had been stacked in a pyramid formation.

“If hay spoilage caused cows to reduce their consumption by only four pounds a day, it could mean pregnant cows losing a half-pound a day during cold weather rather than gaining two-tenths of a pound per day,” Yaremcio adds.

You’ll notice the effect of weather-damaged hay on the condition of your bred heifers before it shows on the mature cows. Bred heifers are typically around 85 per cent of their mature weight. Their rumens are that much smaller than a cow’s rumen as well. Therefore, they aren’t physically capable of eating as much as a cow to help compensate for the reduction in the nutrient density of weathered forages and still maintain their growth and that of the fetus.

2. Keep them off wet ground

“Another issue this year will be storing bales on wet ground,” Yaremcio adds. In 1991, at the Agriculture Canada research farm near Melfort, Sask., Stan Beacom showed that placing bales on a bed of three-quarters of an inch of crushed rock helped to prevent moisture from wicking up from the wet ground into the bales. Gravel with sand or clay content doesn’t work as well as crushed rock because it holds moisture against the bale. Under normal conditions when bales were stored on a dry, four-inch gravel base, there was only one per cent spoilage from the bottom after six inches of rain and 12 inches of snowfall through the winter.

3. Cover them

Hay will lose protein and digestibility when stored outside under normal conditions even when it has been put up in good condition. The digestibility was reduced from about 56 per cent to 36 per cent due to the loss of soluble protein and carbohydrates after bales were left unprotected for 120 days.

Bales can be protected from the elements by covering the rows or stacks with a tarp or plastic. But don’t pull the covering tight against the bales because moisture will condense on the inside surface and “rain” down on the covered bales, Yaremcio explains. Producers have found that it works well to line up the bales in the same direction as prevailing winds, then place some 2x4s between the bales and covering down the length of the stack to allow air to flow through and remove the condensation. Alternatively, lifting the cover during warm, dry weather will allow moisture to escape.

If you can’t afford to store all of your bales under cover, consider protecting the bales for your first-calf heifers and the cows after calving.

FEED TESTING

A typical feed test will measure calcium, phosphorus, magnesium potassium and sodium. In years with unusual growing conditions, it is well worth requesting a test for the important trace minerals — copper, manganese and zinc. Selenium is important as well, however, it is deficient in the soil across the Prairies; therefore, we know without testing that it is deficient in all hay and must be provided as a supplement.

In wet years with big hay volumes, the trace mineral and mineral content of forages tends to be diluted. Yaremcio likens it to sugar in a cookie. If you add the amount given in the recipe, the cookie will have a nice sweetness; the concentration of sugar won’t be as high if you add the proper amount of sugar, but double the rest of the ingredients.

Minerals must be in water solution to be absorbed by plants, he explains. The ability of plants to absorb nutrients from the soil is restricted if drought occurs. When soil moisture conditions are adequate, phosphorus is absorbed early in the growing season and excess phosphorus is stored in the plant to be transported from older plant material to younger material as plant growth progresses.

Calcium is a different story. It isn’t stockpiled in plant tissues and has to be absorbed throughout the growing season. If dry conditions prevail, it’s not uncommon for calcium levels to be 50 to 75 per cent lower in greenfeed and hay than in a normal year.

A continuing lack of moisture restricts normal plant growth and results in early maturity. Acid detergent fibre and neutral detergent fibre levels increase more rapidly and less sugar or starch is deposited in the plant than in a year with normal moisture, reducing overall energy content in the forage.

NIRS VERSUS WET CHEMISTRY TESTS

Many producers have been using near infrared spectroscopy (NIRS) instead of wet chemistry for feed analysis because of the cost difference of about $40 per forage sample and the quick turnaround time for NIRS results.

NIRS measures the nutrient content of forages and grains by the amount of light that is absorbed or reflected off of the sample, Yaremcio explains. Light energy is absorbed by the hydrogen bonds in the molecules of the feed. The light energy is measured by the machine and calibration equations are used to predict the nutritional content of the feed.

The accuracy of NIRS predictions depends on the calibration curves developed from reference samples analyzed by the wet chemistry method. The reference samples are from a wide range of locations, different stages of plant maturity and various environmental conditions. If the range of samples used to develop the curves is too narrow, the NIRS machine may incorrectly report the nutritional value of the test sample. NIRS may not recognize samples with unusual composition, such as those grown under extreme weather conditions, and classify the sample as an “outlier.”

NIRS results for crude protein, acid detergent fibre (ADF) and neutral detergent fibre (NDF) of forages are officially recognized by the Association of Official Analytical Chemists, as a method for determining protein and fibre content of forages. The association doesn’t recognize NRIS as an accurate method to determine mineral content in forages.

Measuring mineral composition (calcium, phosphorus, magnesium, potassium, and sodium) by NIRS is more difficult because they don’t absorb light in the near infrared spectrum unless they are bonded with hydrogen in a molecule.

To illustrate how weather conditions and calibration curves can impact test results, Yaremcio submitted portions from a sample of barley greenfeed grown under drought conditions last year for analyses by both NIRS and wet chemistry. Reported concentrations for calcium, phosphorus and magnesium differed considerably, while the potassium and sodium results were identical as seen below.

The NIRS phosphorus test result for this barley greenfeed sample was 0.38 per cent. That’s 73 per cent higher than the 10-year Alberta average value of 0.22 per cent for phosphorus in greenfeed samples derived by the wet chemistry method.

The NIRS calcium test result was 0.45 per cent, which is very similar to the 10-year Alberta average of 0.46 per cent as analyzed using the wet chemistry method. Yaremcio says you also have to consider that the NIRS value of 0.45 per cent is considerably higher than the 0.16 per cent value reported by wet chemistry. This confirms that calcium absorption is likely to be greatly reduced during a drought year.

The NIRS result for magnesium at 0.23 per cent is very similar to 10-year Alberta average values for six-row barley greenfeed, but is much higher than the average 0.16 per cent value for two-row barley greenfeed.

NIRS test results for calcium, phosphorus and magnesium must be carefully evaluated before the values are used for ration-balancing purposes, he stresses.

ANIMAL PERFORMANCE CAN BE IMPAIRED

Yaremcio works through an example using the 2009 test results to illustrate how the difference reported from the two test methods will influence the supplementation program.

Using barley greenfeed as the sole feed after calving and the NIRS results, a lactating cow would require 113 grams (four ounces) of limestone per head per day to maintain the recommended ratio of two parts calcium to one part phosphorus. Phosphorus and magnesium levels were sufficient when using the Cowbytes software program to balance the ration.

When the wet chemistry results are used to balance the barley greenfeed diet after calving, 50 grams (1.75 ounces) of a 2 to 1 mineral are needed on a per-head-per-day basis to increase the phosphorus content in the ration, along with an additional 95 grams (3.3 ounces) of limestone to reach the 2 to 1 calcium-to-phosphorus ratio. Magnesium is also deficient in the ration. To prevent tetany problems, 23 grams (0.8 ounces) of magnesium oxide per head per day is also required.

A production problem related to phosphorus deficiency will be noticeable sooner than a calcium deficiency. If phosphorus is deficient, feed intake may be reduced, resulting in a reduction of milk in cows and the growth rate in calves. Additional cow concerns are silent heats, extended times to recycle, and low conception rates.

A calcium deficiency can manifest itself as a reduction of weight gain in growing animals. In cows, you may notice milk fever, downer cows, reduced milk production, winter tetany, stillborn calves, and/or retained placentas. Calcium can be mobilized from the bones which can cause osteoporosis.

Due to the wide discrepancies between NIRS and wet chemistry results, Yaremcio advises producers to consult with a nutritionist or extension personnel to obtain a second opinion about requirements for supplements to balance rations.

———

TABLE

Nutrient

NIRS

Wet

chemistry Protein

13.80

13.82

ADF

28.38

25.57

NDF

50.88

48.60

Calcium

0.45

0.16

Phosphorus

0.38

0.20

Magnesium

0.23

0.12

Potassium

0.98

0.96

Sodium

0.02

0.02

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