CATTLE NUMBERS INCREASE
According to the USDA, total cattle numbers in the U. S. on January 1, were 92 million head, up 3% from a year ago. As the graph below shows, cattle numbers increased over 100 years, reaching a peak of 132 million head in 1975. Over that period, numbers increased and then declined in about a 10-year cycle. Also, peak numbers in a cycle were always higher than the previous high, and low numbers were never as low as the previous low. That changed in 1975. Since then, peak numbers in a cycle have not reached the previous high and low numbers have been less than the previous low. Beef cow numbers were 30.3 million, up 4% from last year. Experts predict numbers will increase for several years. How much, for how long, and with what effect remain to be seen.
CAN AN ANTI-INFLAMMATORY DRUG AFFECT REPRODUCTION ?
In an effort to improve reproductive success, temporary (48-hour) calf weaning (TCW) has sometimes been advocated in estrus synchronization for artificial insemination. TCW causes stress-related changes in temperament and physiology of calves and cows. Among other physiological effects, associated inflammation may impair reproduction. Researchers wondered if this impairment might be countered by treatment with meloxicam, a nonsteroidal inflammatory drug.
A group of 943 lactating, open Nelore cows which had calved at least twice were synchronized for estrus before being artificially inseminated. Cows were divided into three groups: 1) calves not weaned for 48-hours before AI; 2) calves weaned before AI; 3) calves weaned and cows treated with meloxicam at weaning. There were no statistically significant differences in pregnancy rates among the three groups. The authors noted “meloxicam failed to benefit pregnancy rates to timed AI”. NOTE: In addition, unlike some studies, in this study temporary calf weaning also did not improve pregnancy rate.
(J. Animal Sci. 94: 406: Oregon St. Univ., Universidade Estadual Paulista, Brazil; Centro Universitario Catolico Salesiano Auxilium, Brazil)
GENETIC CORRELATIONS AND ANTAGONISMS
Many production traits are genetically correlated with other traits. That is, when implementing genetic selection to change one trait there is change in other traits. Some of these relationships are positive, when selection for one increases another, and some are negative, when selection for one decreases another. Some correlations are beneficial for both traits, regardless of the direction of the correlation. But some correlations are not beneficial, so they are antagonistic. Some examples of correlations (with direction of correlation in parentheses) and their implication are:
- milk production and total energy consumption (+), so higher milk means cows must be provided more energy;
- fat thickness and numerical yield grade (+), so as cattle get fatter their yield grade number increases, i. e., leanness decreases;
- body weight at one stage of life and weight at other stages (+), so selecting for heavier weaning or yearling weight also tends to increase birth weight;
- milk production and calving interval (+), so selecting for higher milk tends to increase length of time from one calving to the next;
- age at puberty and carcass fat trim (–), so leaner types of cattle tend to reach puberty later;
- direct calving ease and maternal calving ease (–), so bulls whose calves are easier to deliver tend to sire daughters which have relatively more problems delivering;
- ADG and feed:gain ratio (-), so faster gaining cattle tend to require less feed in order to gain weight.
NOTE: These are just examples of genetic correlations that can be important in selection of breeding stock. It should be noted that antagonistic correlations may be at least partially overcome by simultaneous selection for the traits involved. For example, consider the positive correlation between birth weight and weaning/yearling weight. When most U. S. beef breeds began intense selection to increase weaning/yearling weight then birth weight also increased. Recognizing the association between heavier birth weight and higher calving difficulty, breeders began selecting for moderation in birth weight while still increasing later weights. Breedwide genetic trends document this simultaneous selection has been effective. In short, breeders should recognize major genetic correlations and implement selection programs accordingly.
RELATIONSHIP BETWEEN COW WEIGHT/ EFFICIENCY AND DROUGHT
Larger (heavier) cows require more nutrition. Researchers wondered if the relative efficiency of different size cows stays the same when precipitation differs, resulting in variation in available forage. A study was conducted on high-desert rangeland from 2011 to 2014. Relative to the 50-year average of 13.5 inches at the study location, precipitation was: 2011 (94%), 2012 (58%), 2013 (108%), 2014 (124%). A group of 80 Angus X Gelbvieh cows, all of which had been in the herd for four consecutive years, was evaluated. Based on May, 2013 weight, cows were categorized into five groups: 1000 lb (Sm), 1100 lb (Sm-Med), 1200 lb (Med), 1300 lb (Med-Lg) , and 1400 lb (Lg). Cow efficiency was calculated as weaning weight ÷ cow weight. Nine AI sires were used across all groups.
Efficiency of Sm was significantly higher than Med-Lg and Lg in all years, and was significantly higher than Sm-Med and Med in wetter years. Over all, Sm were most efficient, Sm-Med and Med were intermediate, and Med-Lg and Lg least efficient. Efficiency of Sm over the years ranged from 0.41 in 2012 (the driest year) to 0.58 in 2014 (the wettest year); Lg ranged only from 0.35 in the first two years to 0.39 in 2013. The authors concluded, “This is an indication of the ability of smaller cows to lower maintenance requirements in response to changes in the production environment but with optimal upside potential when conditions are favorable”.
NOTE: Since the same sires were used across all groups, small cows had some inherent efficiency advantage due to “terminal sire effect”, i. e., mating relatively smaller, lower-maintenance cows to relatively larger, higher-growth sires. Also, in spite of this and numerous similar research findings, the industry in general continues to increase size (body weight) of cows.
(J. Animal Sci. 93:5829; Univ. of Wyoming)
DOES ZILMAX® ACTUALLY STRESS CATTLE ?
In 2013, some field observations indicated the growth stimulant Zilmax® (zilpaterol hydrochloride, ZH) might cause various undesirable physical and physiological symptoms in finished cattle, especially after transport to slaughter. Some major packing plants started refusing cattle fed ZH. Since then, some research has been conducted on this matter. A group of 480 Continental-British steers (22% black-hided, 78% red-hided) was studied to evaluate effects of shade and ZH feeding for 21 days before slaughter on feedlot performance, carcass quality, heat stress, mobility, and body temperature. Steers were fed from late January (when implanted with Revalor®-XS) to mid-June or mid-July (depending on body weight) a ration of 87% concentrate.
No differences were observed due to ZH for feed consumption, ADG, or feed efficiency; cattle fed in open pens tended to have a greater ADG than in shaded pens. As had been found in numerous research trials and by industry experience, cattle fed ZH had heavier carcasses, higher dressing percent, larger ribeyes, lower numerical Yield Grade (leaner carcasses), and tended to have less fat cover and lower marbling score.
Respiration rates for ZH were greater, with no differences due to shade. Time of observation affected mobility scores, with observations on the morning of slaughter at the processing plant being the worst for all groups of cattle. In both shaded and open pens, cattle fed ZH had lower body temperature than control. However, reduction in body temperature due to ZH was greater in open than shaded lots. From these results, the authors concluded that “ZH improved carcass weight with little impact on heat stress or mobility, suggesting that animal welfare was not affected by feeding ZH for 21 days at the end of the feeding period”. NOTE: In spite of this and some other similar research results, ZH is still off the market.
(J. Animal Sci. 93:5801; Univ. of Nebraska, USDA-ARS Meat Animal Res. Ctr. at Clay Center, NE)
EFFECTS OF STOCKING RATE, FORAGE MANGEMENT, AND GRAZING MANAGEMENT ON PERFORMANCE AND ECONOMICS OF BEEF COWS
Mature, spring-calving cows averaging 1203 lb were divided into three study groups:
- continuous grazing bermudagrass pasture at 2 ac/cow (CG);
- grazing bermudagrass pasture at 2 ac/cow plus limited grazing on stockpiled forage and winter pasture, (moderate intensity, MI);
- grazing bermudagrass pasture at 1 ac/cow plus limited grazing on stockpiled forage and winter pasture, (high intensity, HI).
Stockpiling was accomplished by fertilizing bermudagrass with 75 lb/ac ammonium nitrate in early August and deferred grazing until November, to provide 0.5 ac/cow. Production of winter pasture involved interseeding wheat and annual ryegrass by no-till drill in the fall, to provide 0.5 ac/cow.
Primary results were:
- days of hay feeding significantly decreased from CG (106 days) to MI (37 days) to HI (15 days);
- percent pregnant tended to be significantly higher for HI (88%) over MI (80%) and CG (78%);
- weaning weight was significantly heavier for CG (524 lb) over HI (484 lb) and tended to be significantly heavier for CG over MI (502 lb);
- excess forage harvested for hay returned $21.42/ac for HI and $6.28/ac for MI;
- net return/ac was significantly higher for HI ($494/ac) over MI ($260/ac) and CG ($217/ac).
The authors concluded “using rotational grazing, stockpiled bermudagrass, and complementary cool-season annual grasses can drastically reduce winter feed requirements and simultaneously increase carrying capacity and net return”.
(2016 So. Sec. Am. Soc. Anim. Sci. Meeting, Abst. 052: Univ. of Arkansas)
BQA (BEEF QUALITY ASSURANCE) TIP-OF-THE-MONTH
Give all intramuscular (IM) injections in the neck and give subcutaneous (SubQ) in either the neck, dewlap, or elbow pocket, as shown below. This will eliminate injection-site lesions in more valuable carcass cuts while still effectively utilizing animal health products.