Cow-Calf Corner: More cattle in and outside of feedlots; Heat stress can reduce pregnancy rates

July 24, 2017
More cattle in and outside of feedlots
by Derrell S. Peel, Oklahoma State University Extension livestock marketing specialist
Feedlots surprised the industry with sharply higher than expected June placements. Placements were up 16 percent, fully 10 percent higher than expected.  This pushed feedlot inventories for July 1 up 4.5 percent from last year despite continued strong June marketings.  Feeder cattle demand has been extremely strong based on very good feedlot profitability recently.  Placements were up across all regions suggesting that placements were driven by industry-wide factors rather than regional factors.  However, the Northern Plains drought likely contributed a bit to larger placements, especially the strong placements in South Dakota, up 67 percent year over year.  In total, I don’t believe that drought was the major reason for the large June placements.
Feedlot demand has dipped deeper into feeder supplies and feedlots have placed more lightweight cattle, beginning in May and especially in June where most of the increase in placements was in lightweight feeder cattle. This includes, for example, a 29.3 percent year over year increase in placements under 600 pounds.  Placements over 800 pounds were up only 1.5 percent in June.
This is important when anticipating the impacts of larger placements the past four months.  The lightweight placements in May and June will not be on top of earlier heavy placements.  Moreover, placements have clearly pulled cattle ahead, meaning that more cattle placed now imply fewer relative placements later. However, overall feeder supplies are larger and will continue to grow into 2018.
The July Cattle report indicates a 2017 calf crop of 36.3 million head, up 3.5 percent from 2016.  The estimated July 1 feeder supply outside feedlots is 37.0 million head.  No comparison to last year is possible as the report was canceled in 2016 (and 2013 as well).  The July 1 beef cow herd was 32.5 million head.  When compared to the January beef cow inventory, this inventory level suggests that herd expansion is continuing in 2017.  The ratio of the July beef cow inventory to the January level is the highest since 1993, during the last herd expansion.  The total inventory of all cattle and calves for July 1 is estimated at 102.6 million head.
At the same time, herd expansion may be slowing down in 2017.  The ratio of July beef replacement heifers to the January estimate is the lowest in the data series (though 2013 and 2016 are missing), perhaps suggesting that heifer retention is slowing.  The quarterly estimate of heifers on feed was up nearly 11 percent from last year, adding additional support to the idea that fewer heifers are being retained as replacements.  Heifer slaughter so far in 2017 is up nearly 11 percent and is likely to remain elevated for the balance of the year.
Taken together, this new data suggests that herd expansion is continuing in 2017, probably more modestly than the previous two years. Heifer retention appears to be slowing further and may suggest little or no herd growth in 2018.  A bigger 2017 calf crop implies larger feeder supplies into 2018 and increased beef production into 2019 at least.

Heat stress can reduce pregnancy rates
by Glenn Selk, Oklahoma State University Emeritus Extension Animal Scientist
The effects of heat stress on reproductive performance of  beef cows has been discussed by many animal scientists in a variety of ways.  After reviewing the scientific literature available up to 1979, one scientist (Christenson, R.K. 1980, J. Anim. Sci. 51: Suppl II: 53.) wrote that the most serious seasonal variation in reproductive performance was associated with high ambient temperatures and humidity.  He further pointed out that pregnancy rates and subsequent calving rates of 10 to 25 percent were common cows bred in July through September.
Typical Oklahoma summer weather can fit the description of potential heat stress, where many days in a row can exceed 95 degrees and night time lows are often close to 80 degrees.  Many hours of the day can be quite hot and cause the slightest rise in body temperature of cattle.  Research conducted several years ago at OSU illustrated the possible impact of heat stress of beef cows on their reproductive capability.  These cows were exposed to bulls as one group (while in a thermo-neutral environment) and one week later exposed to the environmental treatments listed below in Table 1.
Table 1. Effects of Imposed Heat Stress on Reproduction in Beef Cows (Biggers, 1986; OSU)

 
They found that heat stress of beef cows from day 8 through 16 affected the weights of the conceptus (embryo, fluids, and membranes) and the increased body temperature may have formed an unfavorable environment for embryo survival.  As noted in table 1, the percentage of pregnancies maintained throughout the week of severe heat stress was considerably reduced.
Florida scientists studying dairy cows reported that for high conception rates the temperature at insemination and the day after insemination was critical to success.  They stated that the optimal temperature range was between 50 degrees F. and 73 degrees F.  Declines in conception occurred when temperatures rose above this range.
Extremely hot days and warm nights in the Southern Plains will cause core body temperatures of range cows to elevate.  This data suggests that producers should make every effort to establish their breeding seasons when the temperatures are more in a thermal neutral range.  Also remember that bull fertility is affected by heat stress.  Heat stress causes a percentage decrease in pregnancy percentages. It is not an “all or nothing” situation.  Fall calving (with breeding seasons beginning in late November and ending in January) allow for fertilization and early embryonic survival when heat stress is not a factor.
Cow-Calf Corner is a weekly newsletter from the Oklahoma Cooperative Extension Agency.