CattleSense: Research round-up

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I know I’m not alone in my ongoing struggle to balance a limited amount of time with short-term tasks, long-term projects, continuing education, networking, and just finding time to think!  But a recent road trip at least gave me opportunity to catch up on my overgrown reading pile, which turned out to contain several research articles I would like to share here.

Stocker Options

Oklahoma State researchers compared four distinct wintering options for fall-weaned stocker steers: dormant winter range with 2 ¼ lb/day of a 40%-protein supplement, winter range with a corn-cottonseed meal based supplement (24% protein) fed daily at 1% body weight (roughly 2 lb of CSM and 4 lb of corn), wheat pasture grazed at a heavy stocking rate, and wheat pasture grazed at a low stocking rate.  The dormant range was very low quality forage, running no more than 5% protein and about 80% NDF.   Wheat pasture steers then went straight to a finishing program, while range treatments remained on spring/summer grass prior to going to the feedlot. Treatments were repeated for two years.

Steers from the first year were finished to a similar age, while those from the second year were kept on feed until their treatment group was determined to have reached a set weight.  Both intermediate and final carcass measurements were taken, as well as weight gains.

Grazing gains followed expected patterns: dormant grass and protein, about ½ lb per day the first year, and 1 lb the second; dormant grass plus corn and CSM, 1.1 to 1.3 lb/day; heavily stocked wheat pasture, 1.4 to 1.8 lb/day; low-stocked and rotated wheat pasture 3 lb.

When these calves were fed to a common age, the high density wheat pasture calves actually had the most backfat and smallest loin muscle area, while all others were similar.  When fed to a common weight, the steers that had grazed dormant pasture plus protein had lower backfat thickness and tended to have greater marbling scores.   

This data would suggest that—depending on management goals, selling point, and marketing strategy—each of these practices may be a valid option for stocker producers.

Heifer Development

I read two recent papers dealing with heifer development.  They build on other work that has been done, much of it through the University of Nebraska, that has taken a hard look at the generally accepted target of having heifers weigh at least 65% of their mature weight by the start of their first breeding season.  The relevant question is whether feeding these young females for a slower rate of gain (with the affiliated lower feed costs) can still result in acceptable reproductive performance.

In a 3-year study at the USDA Meat Animal Research Center (MARC) in Clay Center, NE, researchers aimed to bring growing heifers to either 55 or 65% of expected mature weight by feeding them for 1 or 1 ¾ lb of ADG from 8 to 15 months of age (including the first 21 days of the breeding season).  During a 47-day exposure to bulls, multiple hormonal and physiologic measurements were taken, as well as determination of pregnancy.

There were no significant differences between groups regarding ovarian development or the number of follicles.  And both treatments resulted in similar overall pregnancy rates.  However…a greater proportion (over 30% more) of the heavier heifers conceived within the first 21 days.

It is easy to understand the value of early breeding, especially for heifers.  Older calves simply have more time to grow before weaning, resulting in heavier weaning weights.  Females that calve early are more apt to breed early for their subsequent calving, having had more time to recover from giving birth.  On the flip side, late-calving cows have been shown to be more likely to completely fail to rebreed.

However, in order to compare the costs of different feeding programs against the value of getting heifers bred early, we need data to back this up.  A collaborative project, using data on nearly 19,000 heifers, evaluated the influence of calving date on longevity and weaning weights.  One data set was from MARC, the other from the South Dakota Integrated Resource Management participants.

When heifers had their first calf within the first 21 days of the calving season:

»  They stayed in the herd significantly longer than those calving later; and,

»  They had heavier weaning weights for their first SIX calves.

It is obvious that the payback from raising replacement heifers to heavier weights – or raising enough ‘extra’ heifers to allow keeping only those that settle in the first period of the breeding season— goes well beyond that first calf.

Forage-free Diets

While most of the country has adequate forage resources for the coming feed season, memories of the recent droughts and hay shortages are still fresh.  This makes some research reported from a Spanish university of special interest.

These workers compared a high-grain (1/3 each corn and barley) control diet containing 10% barley straw to test diets containing similar levels of grain but with three different non-forage fiber sources: 17% soy hulls, 17% beet pulp, or 16% whole cottonseed.  Each was designed to provide the same amount of protein, energy, and NDF in a TMR ration.  Intake, fermentation parameters and feeding behaviors were recorded and analyzed. 

Intakes were highest with the cottonseed, ruminal pH was lowest for the soyhulls (5.9), and chewing time was greater with straw and cottonseed meal than with hulls or pulp.  But the main take-home message was that all these forage-free diets could be viable options in the absence of traditional roughage sources.


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