ANTIBIOTIC RESISTANCE IN MEAT: HOW AND WHEN DID IT DEVELOP?
A new study by the US Department of Agriculture found similar levels of antimicrobial resistance (AMR) in ground beef raised with and without antibiotics. Their report was published in the Journal of Food Protection. The authors noted the data, along with that from previous research in conventionally raised cattle and cattle “raised without antibiotics” (RWA), show that antimicrobial use in US cattle production has “minimal to no impact on AMR in the resident bacteria.”
(Center for Infectious Disease Research and Policy Univ. of Minnesota 11/28/2018)
Another study analyzed DNA from 30,000-year-old permafrost sediments and found genes resistant to several antibiotics, including tetracycline. The authors stated, “These results show conclusively that antibiotic resistance is a natural phenomenon that predates the modern selective pressure of clinical antibiotic use.
(Nature 477:457; McMaster Univ., Canada)
EFFECTS OF FEED EFFICIENCY ON GROWTH AND CARCASS
For many years, feed efficiency in growing/finishing cattle was measured as ratio of feed consumed to weight gain (called feed conversion) or, less commonly, the reverse of weight gain:feed consumed (called feed efficiency). Negative values of feed conversion are desirable, as are positive values for feed efficiency. About 40 years ago a different measure was developed, called residual feed intake (RFI), which is currently receiving increasing interest in evaluating efficiency. RFI, sometimes called net feed efficiency, is the difference between an animal’s actual feed intake and its predicted feed requirements for body maintenance and gain. So, negative RFI value equals higher efficiency.
A recent study examined relationships between feed conversion and RFI with performance and carcass traits. Individual animal feed consumption and weight gain was measured on Angus steers. Feed intake was highly genetically correlated with weight at 200-, 400, and 600-days of age. Genetic correlations were weak between RFI and weight gain, as has been reported in other research. Genetic correlations were low between RFI and ribeye area and fat thickness and were moderate for RFI with intramuscular fat (estimate of marbling) and carcass weight. Based on these relationships, the authors stated “this implies that selection for RFI would have slight negative effects on growth and reduce carcass quality.” So, if RFI is used to select breeding stock they cautioned that some attention should also be devoted to growth and meat quality traits.
(J. Animal Sci. 96:4521; Univ. of New England, Australia)
DIFFERENCES BETWEEN PROFIT OF COW-CALF PRODUCERS
A report analyzed profit of cow-calf operations since 1975. The most recent data is through 2016. Over that 42-year period returns over variable costs averaged $75 per cow, with a high of $577 in 2014 and a low of a $76 loss in 2009. Returns were positive in 30 years (71%). Negative returns rarely occurred in more than two consecutive years, except for a five-year period covering 1981-85.
However, the picture changes when including fixed costs of depreciation, real estate taxes, unpaid operator labor, and interest charge on assets. Including such items, along with variable costs, to calculate total costs resulted in an average loss of $96 per cow over the 42 years. In only five years was there a positive return over total cost, with two exceptional years; return over total costs was $226 in 2014 and $165 in 1977. Greatest loss was $320 in 2016, along with $310 loss in 2015.
Five-year averages are calculated and updated every year to compare net returns of high one-third, mid one-third, and low one-third operations. Over the last five-year period that was available (2012-2016), the high one-third returned an average of $366 over variable costs and $35 over total costs: corresponding returns for mid-level were $204 and minus $134 and for low level were $44 and minus $299. Compared to low level producers, high level weaned calves that were 10% heavier, but number of calves/cow and calf price/lb differed little. Total cost for high level was 16% lower and variable cost 18% lower than low level. As has been shown in other such studies, including Texas A&M AgriLife Extension Standarized Performance Analysis, the largest determinant of economic returns in beef cow/calf operations is cost.
(AgManager.info, Kansas State Univ.)
WHAT ARE THE TOP SELLING BEEF CUTS?
Over 140 beef cuts are sold at retail. For the first half of 2018, the top selling cut, in total dollars and total pounds, was ribeye steak. Second in both measures was strip steak. T-bone steak was a distant third in dollars sold, followed by stew meat, chuck center roast, tenderloin steak, top sirloin steak, top round steak, blade chuck roast, and cubed steak. Below ribeye and strip, the ranking on pounds sold was chuck center roast, stew meat, T-bone steak, top round steak, top sirloin steak, blade chuck roast, cubed steak, and tenderloin steak.
Two factors affect both total pounds and total dollars. A carcass yields more of some retail cuts than others. And retail price varies depending on the cut. In this report, tenderloin steak was valued at $17.44/lb while top round steak was $4.17/lb.
Note there is only one of these products that is always sold bone-in, the T-bone steak. Others are typically boneless in the retail case. In restaurants, especially upscale steak houses, some may be bone-in these days, especially ribeye steak. Years ago, most retail steaks and roasts were bone-in, and not pretrimmed of fat cover.
USING DATA FOR GENETIC CHANGE IN COMMERCIAL HERDS
In a commercial herd where calves are retained through feeding and marketing on a carcass value grid, researchers evaluated use of pedigree information, animal performance, and genotypic data for genetic selection. Effects of those variables on 30-year net present value were measured. (NPV, a common measure in financial analysis, is the difference between the present value of cash inflows and the present value of cash outflows over time).
Four combinations of pedigree, performance, and genotype were evaluated. Use of all four combinations resulted in genetic and economic gain after 30 years. However, it took from 15 to 29 years before breakeven, i. e., when dollar returns offset costs of the data. Shortest breakevens involved data on sires only; longest breakevens involved additional data on replacement females.
The authors concluded “additional cost of that data significantly delays the economic return to the enterprise” and cited similar results from earlier studies showing “the cost of genotyping commercial animals is greater than the economic return to that sector”. More evidence that most of the genetic improvement in a herd comes from selection of sires.
(J. Animal Sci. 96:4076; Univ. of California-Davis, Delta G Miles City, MT, J. R. Simplot Land and Livestock, ID)
EFFECT OF TRACE MINERAL INJECTIONS IN BEEF HEIFERS
Effects of trace minerals were evaluated in commercial Angus heifers initially averaging 221 days of age and 438 lb. One-half of heifers were injected with a mineral containing 60 mg/ml zinc, 15 mg/ml copper, 10 mg/ml manganese, and 5 mg/ml selenium at 221, 319, 401, and 521 average days of age; the remaining heifers received injections of saline solution at the same ages. During the study period, all heifers grazed fescue-red clover pastures supplemented with 6 lb/day of corn distillers grains and given free choice access to an inorganic mineral-vitamin mix.
At average age of 421 days, all heifers were estrous synchronized and artificially inseminated at 430 days followed by cleanup bulls. At this point, body weight and Body Condition Score did not significantly differ, averaging approximately 650 lb and 4.8 BCS (nor did weight and BCS differ significantly at any point in the 10 months of the study). These relatively low values are probably reflected in only approximately 30% of heifers cycling at breeding.
Injecting trace minerals had some effect on elevating copper and selenium status at breeding. However, there were no significant differences in reproductive tract score, AI heat patch score, AI pregnancy rate (30-37%), or overall pregnancy rate (74-75%). NOTE: though there was no intent in this study to evaluate rate of heifer development, it provided additional evidence that inadequate body weight and body condition at breeding can result in poor conception percentages to AI and overall.
Animal Sci. 96:3943; Univ. of Illinois, Iowa St. Univ.)
BQA TIP-OF-THE-MONTH: COLD STRESS
Cold stress in cattle can reduce weight gain, pregnancy rates, and calf survival. Hay intake will increase during cold weather; providing extra hay can help reduce cold stress. Heat is produced from the digestion of hay that will help keep cows warmer. More heat is produced from the digestion of hay than the digestion of concentrate feeds. Never suddenly increase the amount of rapidly fermentable feeds in the diet (e.g. corn, soybean hull pellets, cubes, etc.) because this can lead to subacute acidosis and other problems.
(From Jason Banta, Ph. D., email@example.com , Texas A&M AgriLife Extension Beef Quality Assurance Coordinator)