Beef Cattle Browsing
Editor: Dr. Stephen Hammack, Professor & Extension Beef Cattle Specialist Emeritus
August 2006
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.
DOES SORTING CATTLE PAY?
Not according to research done in Nebraska. In a study over two years, 166 British-cross steers were weaned (mean weight 537 lb) in the fall, backgrounded on corn residue followed by ammoniated wheat straw until mid-April, grazed on native pasture, and then placed on feed. Unless indicated otherwise, cattle were marketed as a group when averaging 0.45 in ribeye fat cover, estimated ultrasonically. One group (G) was sorted at the start of grazing into a heavy half, which went on feed in early July, and a light half, which went on feed in late August. Another group (F) was sorted when placed on feed in late August into a heavy half and a light half. The heavy half was marketed when averaging 0.4 in fat cover (to reduce possibility of price discount for excessive carcass weight) and the light half at 0.50 fat cover (to increase carcass weight, but not excessively). A third group (I) was marketed individually when animals reached either 0.45 fat cover or 1500 lb (4% shrunk weight), whichever came first. And a fourth group (U) was unsorted throughout. (In the following discussion, any difference is at the P<.05 level.)The G groups had lower weight variation when placed on feed, consumed less feed and gained slower than the other groups. Feed efficiency and slaughter weight did not differ, nor did carcass weight, fat thickness, ribeye area, or percent overweight carcasses. Also, Yield Grade (calculated from actual carcass measures) did not differ. However, when assigned by official USDA graders using the industry standard process of subjective eye-balling, F and I had more desirable (numerically lower) Yield Grades than G and U. G had higher marbling scores. Finally, even though there were some differences in some of the production and economic components, there was no difference in total costs or profit, whether marketing would have been live or on a carcass grid. Some other research has shown benefit from sorting, especially on differences in fatness at the start of feeding. (Prof. Anim. Sci. 22:225)
GENETICS OF CONCEPTION & PREGNANCY RATES
Iowa, Kansas, and Nebraska researchers studied records from 3144 Angus heifers from 6 herds in 5 states. Overall pregnancy rate was 93%. Heritability of overall pregnancy rate was 0.13 and of first-service conception rate was 0.03. Also, genetic correlations were low between pregnancy rate and body weight, either at birth, weaning, or yearling. In general, most studies have found that heavier heifers conceive at higher rates. It may be that rate of development in these herds was sufficient so that weight at breeding was not a limiting factor on reproduction. The low heritabilities agree with most published research. As the authors stated, “genetic improvement in heifer pregnancy rate would be expected to be slow”, and, “producers must rely on environmental factors rather than genetics to make improvements in first-service conception to AI.” (J. Animal Sci. 84:2022)
FACTORS AFFECTING PRICE OF STOCKER/FEEDER CATTLE
Arkansas researchers studied over 100,000 cattle sold in over 50,000 lots at 15 auctions during 2005. Variation in sale weight was accounted for in analyses. All factors that were evaluated significantly (P<.001) affected price. There was little difference among those classified as very thin, thin, or average in body condition. However, compared to the average price for those three groups, fleshy individuals brought $5.88/cwt less and fat brought $16.18/cwt less. Compared to steers, bulls brought $6.27/cwt less and heifers $11.39/cwt less. Horned brought $3.70/cwt less than polled/dehorned. Full cattle brought $8.82/cwt less and tanked $26.07/cwt less than the average of lighter-filled. Compared to individuals evaluated as healthy, the following per/cwt discounts were found: dead hair, $12.66; bad eye(s), $13.82; stale, $18.20; lame, $33.47; and sick, $37.99. Compared to single-head lots, groups of 2 to 5 head brought $2.86/cwt more and larger groups $5.35/cwt more. Cattle classified as calves brought $1.84 more than yearlings (again, weight was removed as a factor in these analyses). Cattle announced as preconditioned brought significantly more, but the dollar difference was not reported. (J. Animal Sci. 84:12 Supple.1)
DEWORMING: SINGLE OR MULTIPLE COMPOUNDS?
Multiple, at least in feedyard heifers, according to work by Kansas researchers. In one study (using 1106 heifers) they compared ivermectin (Ivomec) pour-on alone (I) to ivermectin plus fenbendazole (Safeguard) drench (I+F). I+F heifers had fewer (P<.02) treatment repulls, consumed more feed (P<.04), gained faster (P<.01), and weighed more (P<.01) at slaughter. I+F tended (P<.06 to .12) to have lower fecal egg counts and less sickness. There also was a trend (P<.22) to higher feed efficiency for I+F. There were no significant (P<.05 or lower) differences in carcass traits, although I+F tended (P<.13) to have higher marbling and I tended (P<.10) to have more desirable Yield Grade. In the second study (using 756 heifers) there was again an invermectin plus fenbendazole group (I+F) and a doramectin (Dectomax) group. I+F had lower (P<.01) fecal egg counts 35 days after treatment, greater feed intake (P<.01), and higher ADG (P<.06). It appears that combination deworming treatment may have benefits over single compounds in fed cattle, but the benefits should be weighed against treatment costs. (J. Animal Sci. 84:2243)
FASTER IS BETTER?
Not when it comes to leaving the chute. Missouri researchers used 111 weaned Angus-cross steers (mean weight of 534 lb) of known pedigree to study two measures of disposition: subjective evaluation (PS) in a pen (where 1 = gentle and 5 = aggressive) and objectively-measured exit velocity (EV) when leaving a working chute. Faster EV significantly (P<.05) reduced weight gain in a 55-day period. Higher PS also was correlated with lower gain, but that subjective measure was not as accurate as objective EV in explaining temperament effects. (J. Animal Sci. 84:55 Supple. 1)