Selection for or against cow mature size is effective for changing size, but can't be expected to result in much change in carcass composition and meat quality traits such as percent retail product, marbling and tenderness.

However, given the weight discounts currently used in pricing carcass beef, genetic correlations between hot carcass weight and mature cow size may be too large to ignore, say researchers from the U.S. Meat Animal Research Center (MARC).

MARC researchers used data from 1,800 mature cows and their paternal half-sib steers to examine genetic relationships between measures of mature cow size and condition and carcass characteristics. They found that:

  • Heritability estimates for most carcass traits were moderate to high (0.26 to 0.65), suggesting that selection for these traits would be effective.

  • Heritabilities for cow mature weight and height were high (0.52 and 0.71, respectively) but relatively low for body condition score (0.16).

  • Genetic correlations between cow mature size and steer carcass composition and meat quality traits were relatively low (-0.05 to 0.25).

  • Genetic correlations between mature weight and height and hot carcass weight were very high (0.81 and 0.69, respectively). (Nephawe. 2004. J. Anim. Sci. 82:647).
    Michigan State University Spring Cattle Research Update

Though cattle add some nitrogen to pastures via feces and urine, it isn't enough to warrant removing them from a pasture.

That's true, says Lloyd Owens of the Agricultural Research Service (ARS), even if the pasture is above groundwater contaminated by high levels of nitrate-nitrogen.

His study shows it doesn't make any difference in groundwater nitrate levels whether cattle are on the pasture or not. But, pastures with high nitrate levels can't be fertilized for at least a few years, until the levels drop sufficiently.

U.S. Environmental Protection Agency guidelines for drinking water stipulate 10 parts per million (ppm) nitrate-nitrogen as the maximum allowable safe level for drinking water.

Owens studied problem pastures with groundwater nitrate-nitrogen levels of 13-26 ppm, caused by heavy experimental fertilization for 11 years before the study. He stopped fertilizing for a seven-year study to see if that would bring nitrate levels down to safe levels. For comparison, he let cattle graze on two pastures, and fenced them out and made hay from two other pastures.

In the groundwater underneath three pastures, the nitrate-nitrogen levels dropped below 10 ppm within three years; after five years, the levels below all four pastures fell to 2 to 4 ppm.

The finding is good news for ranchers because it indicates cattle don't have to be removed from these problem fields, as long as they stop fertilizing for a while. Letting cattle graze saves the time and labor of baling hay for feed.

The withholding of fertilizer caused only a slight decrease in grass growth, so it doesn't seem to be a serious disadvantage to farmers, especially compared to the environmental benefit.
June 2004 Agricultural Research magazine, Agricultural Research Service

Colorado and Nebraska researchers collaborated on a study using data from a large Nebraska Sandhills cow-calf operation to determine the most profitable strategies for replacement of females.

Three strategies were investigated:

  • maximizing 10-year net income by altering sale and retention of replacements depending on cyclical price changes;

  • maximizing 5-year net present value by adjusting number of females marketed; and

  • maximizing the 5-year difference between net present value and net market value.

The first strategy consistently returned the highest average net income. With that strategy, more weaned heifers were sold in lower-price years (resulting in older average cow age during those years) and more bred yearlings were sold in higher-price years (resulting in a younger herd).

The authors stressed that many factors influence optimal replacement strategy, particularly calf crop percentage, relative price of different classes of cattle, and variations in the cattle cycle. The latter is particularly noteworthy, in view of the current cattle cycle of unprecedented length. (Prof. Ani. Scientist 20:87)
May 2004 Texas A&M University Beef Cattle Browsing Newsletter

Field peas are suitable ingredients for beef cattle consuming medium-concentrate diets, according to North Dakota State University (NDSU) researchers.

Field pea acreage has increased dramatically in North Dakota. That's partially because peas are a legume and fix nitrogen in the soil, and they have the potential to be used as livestock feed.

The NDSU study didn't define the optimum quantity of field peas in the diet, and digestion characteristics of cattle consuming medium-concentrate diets including field peas are still poorly quantified. However, researchers hypothesized that field peas could be included with little or no adverse effects on digestion.

Researchers found that up to 45% pea in by-products-based, medium-concentrate growing diets decreased dry matter intake (DMI), increased dietary undegradable intake protein (UIP) and did not alter organic matter (OM), neutral detergent fiber (NDF) or acid detergent fiber (ADF) digestibility.

The researchers found that field peas can be used as protein and energy sources in the high-concentrate diets because they contain 24% crude protein and 48% starch. DMI wasn't affected when field peas replaced cereal grains in growing diets. And, improved feed efficiency was reported when field peas replaced barley and soybean meal in growing diets.
J. Anim Sci. 2004 82: 1855-1862.

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