ANTIBIOTIC RESISTANCE IN ANIMAL PRODUCTION?
A recent publication by the Food and Agriculture Organization of the United Nations addresses effects of antibiotic resistance due to use in livestock production. The opening sentence of the Executive Summary of the paper states, “It is now accepted that increased antimicrobial resistance (AMR) in bacteria affecting humans and animals in recent decades is primarily influenced by an increase in usage of antimicrobials for a variety of purposes, including therapeutic and non-therapeutic uses in animal production”. However, later in the paper are found statements such as
- Food is likely to be the most important pathway from livestock to humans, although direct evidence linking AMR emergence in humans to food consumption is lacking.
- A high prevalence of multidrug-resistant Campylobacter strains has been detected in organic pig farms in the U. S. even in the absence of antimicrobial use.
- Evidence is lacking regarding AMR transmission pathways between food animals and humans.
- There remains little doubt that the most significant factor in AMR emergence in humans is antimicrobial use for human treatment and prevention.
However, notwithstanding the last statement, there also appears to be little if any doubt that use of antimicrobials in food animal production that are important in human medicine will come under increased scrutiny and regulation, especially for non-therapeutic uses.
RELATIONSHIP BETWEEN HEIFER RESIDUAL FEED INTAKE AND COW EFFICIENCY
Residual feed intake (RFI) is the difference between actual feed intake and what would be predicted as needed for a given level of production. Animals with positive RFI values eat more than predicted, and so are less efficient, and those with negative values eat less than predicted and so are more efficient. Residual gain (RG) is the difference between actual weight gain and gain predicted from feed intake, body weight maintenance, and fat cover; animals with positive values for RG are more efficient.
Individual feed consumption on females was measured over 28-day periods from 240 days of age until 3 calves were weaned or females reached 5 years of age. RFI and RG were calculated from 240 days of age to first calving. As has been found in numerous studies, RFI was independent of ADG. RFI and feed intake were highly correlated; RG was highly correlated with ADG but not with feed intake. Heifers that ate less and were lighter in body weight were subsequently more efficient as cows. There was no significant relationship between RFI and age at puberty, age at calving, or milk production. The authors concluded, “results do not indicate any serious antagonisms of postweaning heifer RFI with subsequent cow and progeny performance traits or with cow efficiency”.
(J. Animal Sci. 94:4860; Ohio St. Univ., Missouri St. Univ., Univ. of Wisconsin, U. S. Meat Anim. Res. Ctr.)
EFFECT OF BRAND AND LEAN/FAT LABELS ON CONSUMER SATISFACTION OF GROUND BEEF
Ground beef represents about 2/3 of pounds of beef sold by the food service industry and over 1/3 of the revenue from beef sold by food service and retail industries.
Ground beef patties weighing 1/3 lb included six label-identified groups (with actual analyzed fat % content):
- 90% lean/10% fat Certified Angus Beef® (CAB) ground sirloin (8.7%);
- 90/10 generic ground beef (10.1%);
- 80/20 CAB ground chuck (17.2%);
- 80/20 generic ground beef (16.9%);
- 80/20 generic ground chuck (17.0%);
- 73/27 CAB ground beef (25.2%).
Patties were cooked to internal temperature of 165 deg. F. and divided into four portions for evaluation by a group of 112 non-trained consumers. The group consisted of a broad variety of genders, household size, marital status, age group, ethnic origin, annual household income, highest level of formal education, weekly beef consumption, individually-declared most important beef palatability trait, and meat product most preferred for flavor (58% preferred beef, 15% preferred chicken, and less than 10% each favored pork, lamb, shellfish, turkey, venison, and fish, in decreasing order of preference). In the first (blind) evaluation, consumers were provided no information as to source of patty. In the second (informed) evaluation, consumers were provided with product type and brand (CAB), if any, before evaluation.
With blind evaluation, there were no significant differences between products in flavor liking, texture liking, or overall liking. There were no differences for tenderness, except that 90/10 ground beef was rated less tender. For juiciness, the two 90/10 products were rated less juicy than all 80/20 and the 73/27 which did not differ.
With informed evaluation, 90/10 CAB was rated significantly highest for tenderness, flavor liking, texture liking, and overall liking but not for juiciness (90/10 CAB was rated higher for juiciness than the generic 90/10, even though actual % fat was only 1.4 % points different). However, among the higher fat content products (20% or 27%) CAB products did not differ from generic products in any palatability factor.
In addition to consumer evaluation, product was evaluated by objective methods for hardness, cohesiveness, springiness, gumminess, and chewiness. Compared to the fatter products, both 90/10 products were significantly harder, more cohesive, gummier, and more chewy, but not springier.
The authors concluded “when sampling ground beef without brand or product information, few consumers find differences in eating quality; but when consumers are aware of brand and fat level before sampling, these factors have a large impact on eating satisfaction”. NOTE: Lower fat products are commonly thought by many consumers to be “more desirable” or “higher quality”. Based on these results, since the CAB product was rated higher only at the lower fat content, consumers may be affected less by brand names for “less desirable” or “lower quality” products. Also, these evaluations were with cooked product. Buying preferences for uncooked packaged product in a retail meat case may, or may not, differ from these results.
(J. Anim. Sci. 94:4943: Kansas St. Univ.)
PREGNANCY DETERMINATION: METHODS, PLUSES, AND MINUSES
There has long been interest in diagnosing pregnancy. Some 4000 years ago, reference is found in Egyptian records to determining pregnancy in women based on changes in skin color and moistness (there were no experimental results reported on accuracy of the method). In beef cattle, the most common method for some time has been rectal palpation of the reproductive tract. My colleague, Dr. Bruce Carpenter, presented information at the Texas A&M Beef Cattle Short Course comparing three methods for determining pregnancy. A summary of his presentation follows:
- Rectal palpation – is a very quick process requiring little equipment. It does require some training and experience, especially for evaluation in early stages of pregnancy though, in practice, many cattlemen test cows when weaning calves, culling open cows at that time. Cows can be sorted, based on pregnancy determination, right out of the working chute. Direct cost is low, from about $4-10/head. Indirect cost comes from misdiagnosis. An open cow called pregnant can cost up to 8 months of a cow’s cost without return. A pregnant cow called open, if culled, incurs unnecessary costs included in replacing with a new female.
- Blood test – are highly accurate (≥95%). There are two types. In one (BioPryn® from BioTracking, Inc.), blood samples are sent to a lab for analysis, with a cost of $2. 50-3.00 per sample plus shipping. Results are available within 24 hours of when the laboratory receives them, so cows must be held for that period before management decisions are made to keep or cull at that time. In the other test (Bovine Pregnancy Test from Idexx), available through veterinarians, samples can be analyzed in groups as collected, so cows can be evaluated and management decisions made the same day. Some practitioners prefer to analyze samples in their clinic; cost is usually $4-5 per sample with no shipping required. There are other private laboratories around the country that perform the blood analysis service as well. Cows must be individually identified, with ear tags, etc. Both of these are essentially yes/no tests, so stage of pregnancy is not determined.
- Testing can be done as early as 28 days post breeding (i.e, in first-calf heifers). Lactating cows should not be tested until at least 75 days after calving because the protein being measured stays in the system from the previous pregnancy for about 75 days. This is not a problem in herds with controlled breeding/calving seasons of 90 days or less because all cows will have calved and be 75+ days after calving by the end of the breeding season. So, as Dr. Carpenter indicated, just wait the recommended 28 days (or more) from when bulls are removed to bleed and test.
- Ultrasound – is also highly accurate but does require expensive equipment and training and skill. Besides merely determining pregnancy, ultrasound can be used for such things as determining fetal gender and number and viability of fetuses.
Open cows cost. There are effective and feasible ways to determine pregnancy.
(Dr. Bruce Carpenter, Texas A&M AgriLife Extension Center at Fort Stockton, TX; BCarpent@ag.tamu.edu )
AMOUNT AND PARTICLE SIZE OF ROUGHAGE FOR FINISHING RATIONS
Cattle evolved over centuries, under pastoral conditions, consuming relatively high-fiber materials, especially grasses. In relatively recent times came the advent of full-feeding young cattle to “finish” them for production of beef. Grains such as corn are energy dense compared to roughages containing higher fiber (hays, silages, seed hulls, stalks, straws, etc.) Since dietary energy can generally be provided more economically from high-energy grains, most cattle finishing operations like to use as much grain and as little roughage as possible. But there are limits in trying to essentially turn ruminants, including cattle, into non-ruminants. Some level of roughage is needed to promote ruminal health and minimize digestive upset. Means of improving utility of low-roughage rations would benefit the finishing process.
Steers initially averaging 847 lb were individually fed for 155 days. As sources of roughage, corn stalks were passed through a tub grinder with a 3-inch screen either 1) once to produce coarser, larger-particle material (long grind, LG) or 2) ground twice to produce a finer, smaller-particle material (short grind, SG). Using steam-flaked corn as the base of rations, three treatment groups were designed with content (dry matter basis) as follows:
- 5% SG stalks, 30% wet corn gluten feed (WCGF);
- 5% LG stalks, 30% WCGF;
- 10% SG stalks, 25% WCGF.
Some results were:
- at the 5% level, LG contained significantly higher physically-effective Neutral Detergent Fiber (peNDF) than SG and the 10% SG level had higher peNDF than either of the 5% rations;
- rumination time was longest for 10%SG, intermediate for 5%LG, and shortest for 5% SG;
- feed consumption was highest for 5%LG, intermediate for 5%SG, and lowest for 10%SG
- dressing percent was lowest for 10%SG compared to both 5% LG treatments;
- calculated on a live basis, ADG did not differ among the three groups, but on a carcass adjusted basis 10%SG ADG was lower than both 5% groups;
- on a live basis, feed efficiency was higher for 5%SG than 5%LG or 10% SG, but on a carcass-adjusted basis efficiency was not different between the two 5% levels and was lowest for 10%SG.
The authors concluded that “increasing particle size of roughage may be a means to decrease roughage inclusion rate while maintaining rumination and performance”. As has been seen in numerous research trials and countless field observations, in general a lower level of roughage resulted in better feeding performance.
(J. Animal Sci. 94:4759; Texas A&M AgriLife Center at Amarillo, USDA-ARS Lab. at Bushland, TX)
EFFECTS OF TRANSPORTATION OF CATTLE
In today’s beef industry, most stocker calves and feeder cattle may be transported multiple times from weaning to slaughter. In addition, cull breeding stock destined for slaughter may be transported several times. Most of this transportation is by tractor-trailer trucks. A Cattle Transportation Symposium was held to assess current research and field experience on the effects of transportation. Some conclusions from the conference, funded by the Beef Checkoff :
- Loading density – Space required is generally said to be about 1.3 sq ft/cwt body weight, from slightly more to slightly less as weight increases. This paper reported variation in space allowed in practice varied depending on location in modern semi-trailers. Belly and deck compartments tended to be loaded slightly more densely; the nose and back tended to be loaded markedly less dense. Trucks with more axles increases weight that can be carried and therefore density; this tends to result in overloading light calves and underloading heavy finished or mature cattle. The authors stressed the backs of cattle should not touch the roof or top of a compartment. Bruising increased with both over and under loading.
- Duration and distance – Distance is more import than duration, which includes any time waiting after loading, both driving and stationary periods, and waiting to unload. After a maximum of 28 hours on a truck, USDA regulations provide that livestock must be unloaded, fed and watered, and rested for at least 5 hours. One study reported cattle transported to commercial feedlots traveled an average of 317 miles, or about 7 hours at an average speed of 62 mph; the study concluded most transporters adhere to regulations. Weight shrink increases fastest with longer transportation duration at higher temperature.
- Feed and water withdrawal – Research has shown cattle fasted without feed and water lose body weight depending on length of time fasting as follows: 12 hours (6%), 24 hours (8%), 48 hours (12%), 96 hours (14%). Initial loss is mostly water but is more from body tissue as time increases. (One study showed with average transport of 636 miles about half of weight loss was from muscle tissue). Regaining weight loss may require up to 5 days.
- Weather and trailer environment – Cattle trailers are not climate controlled. Ventilation comes from perforations in walls and roof openings. Variations, especially rapid, in temperature and humidity impact cattle comfort and stress. Effects are larger during stationary periods. Temperature-humidity index (THI) is lower in belly and back compartments, due to less solar radiation; highest THI tends to be in the nose, due to lower airflow immediately behind the tractor. One study showed highest death loss at ambient temperature of <5 deg. F; some lack of ability to walk was observed at temperatures >86 deg. F. Bedding during extremely cold temperatures provides some comfort and insulation; a survey found that bedding was less likely when hauling cull animals to slaughter, suggesting economic value and future performance had some influence on whether to bed.
- Animal handling and driver experience – Loading and unloading stresses cattle more than transport itself. Stresses are lower when animals are handled slowly, gently, and quietly which, contrary to some common thought, often requires less time to load and unload, not more time. Drivers should be trained in effective handling methods, and should recognize anticipated conditions to be encountered on a haul. Shrink at unloading tends to be lower with drivers having >6 years experience. The report emphasized that more and better driver training is needed.
- Animal factors – Cattle age, condition, temperament, and previous handling/loading/transporting experience determines how well they may accommodate hauling. Younger calves generally experience more stress and have more subsequent health problems; heavier calves have fewer problems than lighter calves. Cull cows are more affected by long hauls than finished cattle. Inherently calmer cattle have fewer hauling problems than nervous, aggressive animals.
- Transportation, handling, and carcass value – The National Market Cow and Bull Beef Quality Audit reported 63% of market cow carcasses and 54% of finished cattle had bruises associated with hauling and handling. Other research showed bruising occurred most frequently on the round in cows and in the high-value rib-loin area in finished animals.
- Fitness for transport – Two industry segments were identified as the largest source of transportation-related problems, those being livestock auctions and cull dairy cows. Auctions have identified barriers to improvement of low influence over consigners, inadequate help, and insufficient time. Often cull dairy cows are less fit to be hauled than most other animals. Problems are reduced among all cattle if they are fit. Recommendations in this summary included:
- feeding within 24 hours before loading if to be hauled >4 hours;
- feeding and watering within 5 hours of loading if to be hauled >12 hours;
- animals should be in good health and fit for hauling;
- animals should be handled as little and as gently as possible;
- animals should be rested at least 5 hours after 48 hours or more of hauling.
(Prof. Anim. Sci. 32:707; Agriculture and Agri-Food Canada, Colorado St. Univ., Texas A&M Univ., National Cattlemen’s Beef Assoc.)
BQA TIP OF THE MONTH – NEEDLE SELECTION
Proper needle selection is important to reduce risk of broken needles and ease the process of giving injections. Both needle length and gauge (thickness) should be considered. Shorter needles (i.e., 5/8 and 3/4 inch) make it easier to properly give subcutaneous injections. For intramuscular injections, a 1-inch needle is sufficient even on mature bulls and cows; longer needles increase risk of bending and breaking. For thicker products, a 16-gauge needle works well. Either a 16- or 18-gauge needle is fine for thinner products. Needles smaller than 18-gauge should be avoided for giving injections to cattle.
(Jason Banta, Ph. D., firstname.lastname@example.org , Texas A&M AgriLife Extension Beef Quality Assurance Coordinator)