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.
ARE ORGANIC FOODS NUTRITIONALLY BETTER?
A search of the scientific literature concerning organic food identified 12 relevant studies from out of almost 100,000. The authors found only one study indicating a possible benefit from an organic-source food. That study “suggested an association of reported consumption of strictly organic dairy products with a reduced risk of eczema in infants.” But “the majority of studies showed no evidence of differences in nutrition-related health outcomes that result from exposure to organic or conventionally produced food.” The authors stressed the need for additional well-designed research. (Amer. Jour. of Clin. Nutr. 10/12/2010)
HETEROSIS EFFECTS ON LIVE PERFORMANCE AND CARCASS MERIT
An analysis was conducted of results of crossbreeding studies published from 1976 to 1996. Depending on the trait, the number of studies analyzed ranged from 31 to 78. Effects of heterosis were analyzed for five types of crosses: British X British, British X Continental, Continental X Continental, British X Zebu, and Continental X Zebu. Both individual and maternal heterosis was analyzed for birth weight and weaning weight. Individual heterosis was analyzed for postweaning traits: average daily gain, carcass weight, ribeye area, fat thickness, and marbling score. Heterosis was calculated in units of the trait rather than as a percentage:
| Birth Weight, lb | Weaning Weight, lb | ADG, lb | Carc. Wt, lb | |||
| Individual | Maternal | Individual | Maternal | Individual | Individual | |
| Br X Br | 1.98 | 1.25 | 18.1 | 18.3 | 13.9 | 22.7 |
| Br X Con | 1.54 | 1.82 | 12.7 | 16.3 | 17.4 | 28.9 |
| Br X Zebu | 5.35 | 3.37 | 50.6 | 48.6 | 32.3 | 92.5 |
| Con X Con | 1.39 | 2.46 | 7.6 | 34.4 | 20.0 | 36.2 |
| Con X Zebu | 4.40 | 2.42 | 57.0 | 23.4 | 3.3 | 54.2 |
Heterosis effects tended to be notably higher in British X Zebu, with Continental X Zebu generally being slightly lower except for individual weaning weight. However, Con X Zebu heterosis for postweaning ADG was very low. Heterosis for carcass weight, the cumulative effect of overall growth to slaughter, was highest for British X Zebu, intermediate for Continental X Zebu, and lower for the three Bos taurus classifications. Over all, British X Zebu averaged heterosis over 2 ½ times higher and Continental X Zebu about 1 ½ times higher than Bos taurus.
There was little heterosis for fat thickness or marbling score. Heterosis for ribeye area tended to follow the same pattern as for carcass weight, which is not surprising since the two tend to vary in the same direction. This summary of existing research confirms that heterosis is significant for growth traits and is higher in crosses involving Zebu. In addition, significant heterosis has been found in other studies for reproduction and livability. (J. Animal Sci. 88:460; Univ. of Georgia, National Institute of Livestock Research-Uruguay)
DISTILLERS GRAINS: CORN VS SORGHUM
Corn-based and sorghum-based wet distillers grains (WDG) were compared to a non-distillers control fed to steers initially averaging 860 lb. Steam-flaked corn was the base for all rations. Levels of both 15% and 30% WDG were studied, with the two WDG levels consisting of either corn-based, sorghum-based, or a 50:50 mix of the two. Final weight was calculated in two ways: actual (live weight shrunk 4%) and adjusted (hot carcass weight ÷ average dressing percent.) Both actual and adjusted were used to evaluate ADG and gain:feed.
Actual and adjusted final weight and gain:feed was higher (P<.05) for 15% compared to 30% WDG. Dry matter intake was higher (P<.05) and actual gain:feed was lower (P<.10) for sorghum versus 50:50. Corn WDG had higher (P<.05) adjusted gain:feed than sorghum or 50:50 WDG. Compared to all WDG treatments, the control ration without WDG resulted in higher (P<.10) dry matter intake, higher (P<.05) actual and adjusted ADG and final weight, and higher (P<.10) adjusted gain:feed.
Carcass weight and ribeye area were higher (P<.05) for 15% versus 30% WDG. Corn WDG had higher (P<.05) dressing percent than sorghum or 50:50 WDG. The control ration resulted in higher (P<.05) carcass weight, fat thickness, and numerical Yield Grade (lower leanness) and higher (P<.10) dressing percent. There were no significant differences in marbling score, percent Choice/Prime, or abscessed livers. (J. Animal Sci. 88:2433; Texas Tech Univ.)
EFFECT OF HUMAN CHORIONIC GONADOTROPIN (hCG) IN AI FOR COWS
Over six locations, 506 cows received the same drug protocol prior to timed artificial insemination. At 7 days after insemination, half of the cows received 1000 IU of hCG and the other half received 1 ml of saline as a control group. The hCG treatment increased volume of luteal tissue and concentration of progesterone 7 days later and concentration of progesterone 26 days later. Treatment tended (P<.07) to increase early pregnancy by an average of 10.2 percentage points. However, by 68 days after insemination, overall pregnancy rates were similar. (J. Animal Sci. 88:2337; Univ. of Minnesota, Kansas State Univ., Univ. of Florida)
TEMPERAMENT VS. PERFORMANCE
A total of 3050 calves at 27 locations were evaluated for temperament scores and ADG. Breeds involved were German Angus (Angus X dual-purpose breeds), Charolais, Fleckvieh (German Simmental), Hereford, and Limousin. Temperament was evaluated subjectively for chute activity score and flight score from the chute, with higher scores of both indicating greater activity. Genetic correlations within breed between the two scores ranged from 0.57 to 0.98. Breed significantly affected (P<.001) both scores, with Charolais and Limousin scoring highest. Herefords had the lowest (P<.001) chute scores and German Angus and Hereford had the lowest (P<.001) flight scores. Females were lower (P<.01) than males on both scores. In most breeds, temperament scores were negatively correlated with ADG. This confirms, and expands to other continents and breeds, previous findings relating temperament and performance. [(J. Animal Sci. 88:1982; Georg August Univ. (Germany) and Justus Liebig Univ. (Germany)]
EFFECT OF MEAT-BASED NUTRIENTS ON CANCER RISK
A recent European study, coordinated by a researcher at the Imperial College of London, tracked 2670 people for incidence of cancer over a period of five years. All subjects were free of cancer at the start of the study. People with higher blood levels of Vitamin B6 and methionine had less than half the risk of developing lung cancer than those with lower levels. Meat and fish are good sources of both Vitamin B6 and methionine. (meatingplace.com, 6/22/10)
TEXAS A&M BEEF CATTLE SHORT COURSE
The 56th Annual Texas A&M Beef Cattle Short Course will be held August 2-4 on the Texas A&M campus in College Station. Topics concerning all aspects of the beef industry will be addressed. Full information and procedures for registration can be accessed at https://animalscience.tamu.edu/ansc/BCSC/index.html.