Beef Cattle Browsing – October 2005

Beef Cattle Browsing

Editor: Dr. Stephen Hammack, Professor & Extension Beef Cattle Specialist Emeritus

October 2005

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.

Research has shown that flavor is the biggest reason people eat beef but lack of tenderness is the main factor affecting acceptability. However, marbling is the primary factor used to predict eating quality. Researchers at Texas A&M, Kansas State, and Cornell collaborated on a study including over 7000 animals from 14 breeds to examine genetic aspects of beef quality factors. (The protocol of the study did not allow comparisons among breeds.) Heritability was found to be high for marbling, tenderness, and juiciness but not for flavor. More than 20% of steaks evaluated were classed as unacceptably tough and variability was high for tenderness scores, but not for flavor. Tenderness was significantly correlated with marbling, juiciness, and flavor but the numerical values of the correlations were low, as was true for correlations between marbling and either flavor or juiciness. The authors concluded that tenderness, juiciness, and marbling could be effectively changed by genetic selection but selection for marbling would have little effect on tenderness. Since flavor was low in heritability and varied little, it could not be improved much by genetic selection. On the other hand, it would be hard to mess it up. (J. Animal Sci. 83:2461)

Serving capacity in bulls has often been measured by using restrained females. But there has been some indication that this technique may not accurately reflect sexual behavior in pasture mating. In previous work, Kentucky researchers used unrestrained females, with exposure either to a single estrual female or to four females in sequence. In the latest Kentucky study, bulls were evaluated by exposure to four estrual females in sequence for 30 minutes per female or exposure to four estrual females as a group for 2 hours. In short, it was found that “a group of unrestrained, sexually receptive females induces greater sexual responsiveness in bulls than sequentially pairing them with individual females”. The authors concluded that tests using restrained females may not be valid and that group exposure to unrestrained females appears to be the most reliable method of evaluation. (J. Animal Sci. 83:1801)

Researchers in southwest Arkansas studied stocking rates of 1.5, 2.5, 3.5, or 4.5 hd/ac on dallisgrass-common bermudagrass pastures fertilized at rates of 100, 200, or 300 lb N/ac. The cattle evaluated were Bos taurus X Bos indicus steers initially weighing 508 lb. Individual ADG was highest at 1.5 hd-300 lb N and lowest at 4.5 hd-200 lb N. Gain per acre was highest at 3.5 hd-300 lb N and lowest at 1.5 hd-200 lb N. Cost of production was lowest at 1.5 hd-100 lb N and highest at 4.5 hd-300 lb N. Using equations developed from the data, highest net return (gross dollars return minus total dollars cost) from the three fertilization rates was obtained at different stocking rates. For 100 lb N, highest return ($111.53/Ac) was at 2.3 hd/ac; for 200 lb N, highest return ($110.62/ac) was at 2.6 hd/ac: and for 300 lb N, highest return ($143.98/ac) was at 2.9 hd/ac. The authors noted that other research on native range showed highest net return when stocked at 55 to 60% of the stocking rate that produced highest gain/ac. However, in this study, on intensive pasture, highest net return was at a stocking rate approximately 80% of that producing highest gain/ac. (J. Animal Sci. 83:2235)


Most genetic change is accomplished through selection of sires. So, genetic change in females is more effective if important production traits in females are closely related to traits in males. Nebraska and USDA Meat Animal Research Center researchers used data from six sire breeds and three dam breeds to determine genetic relationships among reproductive traits of males and females. Traits studied in males were yearling weight, height, and scrotal circumference, age at puberty, testis length, testis volume, 15-month weight, and 15-month height. Traits in females were age at puberty (AP) and 18-month pregnancy rate (PR). In agreement with numerous other studies, heritability of PR was very low (0.10), but PR was significantly related to numerous male traits that are relatively high in heritability. So, indirect selection for PR (by selecting for male traits) should be more effective than direct selection. However, no male trait was found to be effective for improving AP in females. (Scrotal circumference was the trait most closely related to AP.) Heritability in this study for female AP was high (0.52), indicating significant progress could be made when selecting directly for that trait, but the authors noted the difficulty in measuring AP in females. (Prof. Anim. Sci. 21:195)

Water sprinkling is often used in High Plains feedlots to alleviate the effects of heat stress and dust. Texas A&M, Texas Tech, and USDA researchers wanted to know if sprinkling also might reduce incidence of common pathogens, especially Salmonella species and E. Coli. Crossbred feeder heifers with white and red hair coats were fed from June 25 to October 2. Treatment lots were sprinkled for two minutes every hour from 11 am to 5 pm on days when temperature exceeded 86 degrees F., which occurred on 64 days of the 98-day study. Fecal samples, hide swipes, and body weights were taken about once every month. Sprinkling had no effect on feed consumption, weight gain, or feed conversion, nor on any carcass traits. Sprinkling also had no statistically significant effect on incidence of pathogens. There were trends, on day of slaughter, for fecal Salmonella to be higher and for E. coli on hides to be lower. (J. Animal Sci. 83:1959)

This question often arises, especially among those not engaged in commercial production such as youth with livestock projects. Dr. Floron (Buddy) Faries, Extension veterinarian at Texas A&M, points out that it can be a matter of intent. In his publication “Drug Residue Avoidance Program Guidelines for Junior Livestock Shows”, Faries points out that “any substance administered to an animal with the intent to prevent or treat conditions or to make changes in body functions is classified by FDA and/or USDA as a drug or chemical”. So, whether or not it’s a drug depends not only on what it contains but what you’re trying to do.

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