Editor: Dr. Stephen Hammack, Professor & Extension Beef Cattle Specialist Emeritus
This newsletter is published by Texas AgriLife Extension – Animal Science. Media, feel free to use this information as needed and cite Texas A&M University Beef Cattle Browsing Newsletter, Dr. Steve Hammack.
DROUGHT AND VITAMIN A
Most of Texas is currently under drought conditions, much of them severe. And this condition has persisted for a long time in some areas. One thing that comes into play during drought that is usually not a problem is Vitamin A deficiency. Cattle can store from two to four months supply of vitamin A in the liver on diets exceeding Vitamin A requirements, basically a little something green. That supply can be exhausted in a drought. How do you supply supplemental vitamin A? My colleague Dr. Ted McCollum, Extension Beef Cattle Specialist at the Texas AgriLife Center in Amarillo, recently summarized supplementation of vitamin A:
- most fortified range/breeder cubes fed at 1-1 1/2 lb/day for dry cows or 1 1/2 – 2 lb/day for lactating cows should provide adequate levels of vitamin A;
- mineral supplements, if fortified with 200,000 units vitamin A/lb, would provide adequate levels when consumed at rates of 2-4 oz/day;
- stability of vitamin A in supplements can be affected by composition of the supplement, source of vitamin A, and length and conditions of storage;
- injectable vitamin A can be used to provide from about 1-3 months reserve, depending on the cow’s stage of production and the concentration and dose of the product.
Supplementation of vitamin A is relatively inexpensive and should be an integral part of drought management.
PREDICTING BREED FROM DNA ANALYSIS
DNA samples from semen from 2235 bulls of 16 breeds were analyzed. The bulls were chosen by respective breed associations as representative of the breed. Breeds included those most numerous in the US as follows:
- British: Angus, Hereford, Red Angus, Shorthorn;
- Continental: Braunvieh, Chianina, Charolais, Gelbvieh, Limousin, Maine-Anjou, Salers, Simmental;
- US derived: Beefmaster, Brahman, Brangus, Santa Gertrudis.
Results were used to determine accuracy of predicting breed content of known 2-, 3-, and 4-breed cross cattle. Predictions were 88% to 92% accurate, except for Angus (80%) and Red Angus (77%). Combining these two resulted in accuracy of 88%. Genetic relationships among breeds were similar to what might be expected from the geographical background of the breeds except the relationship between Hereford and the other British breeds was not as close as might be thought. The authors concluded that “ breed frequencies predicted from a high-density SNP panel can be used to predict breed composition of crossbred animals.” (J. Animal Sci. 89:1742; U. S. Meat Animal Res. Ctr.)
RELATIONSHIPS BETWEEN EFFICIENCY AND HEIFER BODY COMPOSITION AND FERTILITY
RFI (Residual Feed Intake) is a measure of efficiency. High RFI animals eat more feed than predicted from their body size and low RFI animals eat less. RFI has been found to be unrelated to ADG, so low RFI animals are more efficient. In a study over two years, 137 mostly Angus and Angus-cross spring-born heifers were weaned, grazed or fed hay until February, at which time they were fed a silage-based ration until June and individual feed intake was measured.
At the beginning of the study, heifers averaged 387 days old, 741 lb, and Frame Score of 5.5. ADG averaged 2.51 and final weight 932 lb. High RFI heifers ate significantly more and were 13 days younger at puberty; ADG did not differ. High RFI values were positively correlated with ultrasonic back and rump fat. There were no significant differences in estrus detection rate, conception rate, or pregnancy rate, though high RFI tended to be higher in those traits. The authors concluded that less efficient (high RFI) heifers stored excess energy consumed as body fat, which may have hastened maturity and initiated puberty earlier. However, they indicated that selection for greater efficiency (low RFI) should not adversely affect reproduction. (J. Animal Sci. 89:1028; Univ. of West Virginia)
HEALTH AND CULLING PRACTICES OF U.S. COW HERDS
Health and culling practices were factors surveyed in 2007-08 by the USDA National Animal Health Monitoring System. The survey reached operations in the 24 states comprising 80% of US beef cow operations with 88% of the nation’s cows. Some of the findings were as follows:
- about 70% of operations vaccinated calves or cows,
- vaccination was practiced more in Central and Western regions than in the Southeast,
- about 60% did not vaccinate calves for respiratory disease before they were sold,
- only 6% used fecal testing to evaluate internal parasite levels,
- about 2/3 used some form of antibiotic treatment,
- about 90% dewormed calves or cows at least occasionally,
- about 1/2 sold calves immediately at weaning,
- about 1/3 of cows sold was due to pregnancy status and 1/3 due to age or bad teeth.
The entire report is available at http://www.aphis.usda.gov/animal_health/nahms/beefcowcalf/index.shtml#beef0708.
EFFECT OF WHEAT PASTURE DURING BREEDING ON HEIFER REPRODUCTION
In each of two years, 40 Angus heifers were grazed on wheat pasture from December to March and then divided into two groups during estrus synchronization and fixed-time AI (FAI). One group (WP) remained on wheat pasture and the other (DL) was placed in drylot. Ten days after FAI all heifers were exposed to bulls for 45 days. At FAI, DL were 31 lb heavier. There were no differences in conception rate or pregnancy rate. Even though blood urea levels were five times as high in WP, the authors concluded that grazing wheat pasture during synchronization and AI did not affect reproductive performance. These were spring-calving heifers. Results might be different with fall-calving heifers on wheat pasture when breeding would usually occur on more lush forage. (Prof. Anim. Sci. 27:9; Oklahoma St. Univ.)
ECONOMICS OF PRECONDITIONING CALVES BEFORE SALE
The effect on price of some degree of preconditioning calves before sale was summarized across 11 studies conducted in numerous states. Premiums of the averages of the studies varied from $1.68/cwt to $7.02/cwt; the average was $3.79. In a separate summary of the averages of 13 studies, net profit/calf varied from a loss of $76.65 to a gain of $40.46; the average was a gain of $7.66 per calf. Other work has generally found that the biggest factor affecting economic returns from preconditioning is nutritional cost. Also, the authors pointed out that maximum benefit comes from establishing “a reputation that the preconditioned calves are as advertised” and that smaller producers should consider special commingled preconditioned sales to realize full benefit. (Prof. Anim. Sci. 27:73; Univ. of Kentucky and Univ. of Florida)
EFFECT OF RESTRICTED NUTRITION ON LONG-TERM COW PERFORMANCE
In a 7-year study using a composite genetic line (½ Red Angus, ¼ Charolais, ¼ Tarentaise), half of a group of cows was wintered (December to March) on what was calculated to be adequate (ADQ) levels of nutrition. The other half received marginal (MRG) levels. For 140 days after weaning, half of the heifers out of both the ADQ and MRG cows were fed ad lib (CON) and heifers out of the other half of both cow groups were restricted to 80% intake (RST). When not in these treatment groups, all animals were grazed together and were culled for failure to reproduce or wean a calf. The following results were reported:
- RST heifers ate 22% less feed at a savings of $24/head;
- MRG cows ate 200-300 lb less winter supplement at a savings of $9-12/year;
- RST heifers weighed less throughout life but heifers out of MRG cows weighed more;
- during the first three years of production, more MRG cows were culled;
- during later years, retention rates became similar, except being slightly lower in RST heifers out of ADQ cows;
- MRG cows out of MRG dams had lighter calves at birth and weaning;
- cows out of MRG dams had higher body condition, possibly indicating greater drought resistance and improved longevity in limited nutrient environments;
- MRG cows out of MRG dams may be a better match of genetics and environment.
(2009 Proc. West. Sect. Am. Soc. Anim. Sci. and Research Monograph; USDA-ARS, Miles City, MT)
HAS BEEF PRODUCTION BECOME MORE EFFICIENT?
CAUTION: the following is not based on peer-reviewed research.
Beef production per cow is often put forth as a measure of efficiency. There is no question that we are producing more pounds of end product for every cow in the US. But does this mean we’re more efficient? I recently looked at USDA data on beef production and cattle numbers. The most recent data I could find were from 2009. I decided to compare these to 1959, a 50-year time span. Note: “beef” as used below is pounds from cattle and calves:
- in 1959, we produced 477 lb beef/head slaughtered;
- in 2009, we produced 757 lb beef/head slaughtered, or 59% more per head;
- in 1959, 26% of slaughter was calves but in 2009 it was only 2%;
- using average cattle and calf weights and assuming all calves would be fed to cattle stage in both years reduced the difference in lb/head to 28%, not 59%;
- average cattle slaughter weight was 1008 lb in 1959 and 1293 lb in 2009 (28% higher.)
So, if all calves had been fed in both years, the increase in lb beef/head slaughtered would have exactly equaled the increase in average slaughter weight of cattle. We are producing more beef/cow because we’re now feeding practically every head not kept for breeding and cattle are larger. Are we more efficient now? Maybe we are. But pounds of beef per cow is not a good way to measure efficiency. We need to know what caused the pounds, not to mention what it cost to produce them. (Source: USDA data and personal calculations.)
TEXAS A&M BEEF CATTLE SHORT COURSE
The 57th Annual Beef Cattle Short Course will be held on the campus of Texas A&M University on August 1-3, 2011. For information on the schedule, registration, etc. go to https://animalscience.tamu.edu/ansc/BCSC/index.html.