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.
FETAL PROGRAMMING OF MUSCLE AND FAT DEVELOPMENT
The concept of fetal programming arose in human studies linking poor maternal nutrition and low birth weight to higher levels in adults of hypertension, heart disease, stroke, and diabetes. In a recent symposium, “Fetal Programming in Animal Agriculture”, the effect in ruminants of fetal programming on development of muscle and fat was addressed. A review of over 80 papers was presented. It has been well established that there is no net increase in muscle fibers after birth. So, any decrease of or failure to develop muscle fibers during fetal growth permanently reduces muscle mass. In addition, the period of fetal development is a major stage of generation of intramuscular fat cells, so fetal programming influences subsequent levels of marbling. The authors concluded that a better understanding of the relationship between these mechanisms and maternal nutrition would prove beneficial in improving growth, muscling, and palatability of beef. [J. Animal Sci. 2010. 88(E Suppl.):E51-E60; Univ. of Wyoming, South Dakota St. Univ. Univ. of Texas Health Sci. Ctr.]
PREDICTION OF FED CATTLE TRAITS USING GENOMIC TECHNIQUES
Genomic prediction techniques called genetic profiles are currently available from three commercial companies. Profiles from one of the companies, Merial LTD/Igenity, were used to evaluate prediction of actual ADG, marbling or % Choice, tenderness, ribeye area, fat thickness, and Yield Grade. A total of 764 feeder steers and heifers were obtained from 11 Oklahoma and Texas commercial producers who usually retain ownership for finishing. Calves were out of cows of mixed beef-type breeding and sire-breed percentages were: 37% by Limousin, 36% by Charolais, 14% by Angus, 4% by Red Angus, and 9% by other or unknown breeds.
Cattle were fed in the same commercial feedyard under standard industry management. Initial weights averaged 676 lb (467 lb to 867 lb) for steers and 646 lb (478 lb to 883 lb) for heifers. Time of slaughter was determined using a commercially available software program that predicts for individual animals the day that incremental cost of gain exceeds incremental value of gain. This resulted in average days on feed of 175 days, varying from 135 to 257 days.
ADG averaged 3.3 lb/day (1.5 to 4.8) for steers and 2.9 lb/day (1.3 to 4.2) for heifers. Feed:gain averaged 5.6 (4.4 to 9.6) for steers and 6.1 (4.4 to 9.7) for heifers. Slaughter weights averaged 1270 lb (1000 lb to 1535 lb) for steers and 1154 lb (884 lb to 1375 lb) for heifers. Quality Grade averaged mid-Select for both steers and heifers, ranging from Standard to Prime, and Yield Grade averaged 2.4 for both steers and heifers, ranging from 1 to 5.
Phenotypic correlations between profile scores and corresponding actual values were statistically significant in some cases but the magnitude of all correlations was small, averaging 0.13. The highest correlation was 0.25 between panel scores for marbling/percent Choice and Quality Grade in Angus/Red Angus-sired cattle. However, genetic correlations tended to be considerably higher, indicating the prediction profiles should be useful in genetic selection of breeding stock. Relationships were calculated between the various profiles and net dollar return. The only significant relationship was that a 1 unit increase in marbling profile score increased net return by $7.53 per head. Based on these results, this profile may be more effective in selecting breeding stock than in predicting actual feedyard/carcass performance. (J. Animal Sci. Papers in Press, 1/28/11, downloaded 4/13/11; Oklahoma St. Univ.)
MORTALITY OF BEEF CALVES AND CATTLE IN THE US
Mortality was one of the 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 herds with 88% of the nation’s cows. Across all sizes of operations, 2.9 % of calves were born dead and 3.5% died between birth and weaning, leaving 93.6% of calves born surviving to weaning. These data varied little across herd size. The biggest causes of death up to 3 weeks of age were birth-related problems and weather-related causes followed by digestive problems and unknown causes. After 3 weeks of age the primary causes of death were respiratory problems and digestive problems with unknown causes ranking third. Across all operations the average death loss of breeding cattle beyond weaning age was 1.5%, and again there was little difference due to herd size. Calving-related problems and weather-related causes ranked third and fourth as causes of death, with unknown causes and other known causes ranking first and second.
(Downloaded 4/12/11 from http://nahms.aphis.usda.gov)
DDGS FOR SUPPLEMENTING BEEF HEIFERS
Ethanol co-products, such as dried distillers grains with solubles (DDGS), are being used in increasing amounts in finishing cattle. This study evaluated the effects of DDGS supplementation on forage intake and digestibility. Rumen-cannulated British crossbred heifers initially weighing 832 lb were grazed on small-grain pasture for two weeks and supplemented with DDGS at 0, 0.2%, 0.4%, or 0.6% of body weight. Supplementation did not affect forage intake, regardless of supplement level. Forage digestibility increased as level of supplement increased. These results indicate that DDGS can be effectively used for supplementing developing beef heifers. Where DDGS can be obtained at a price advantage, it should be considered for this purpose. (J. Animal Sci. 89:1229; New Mexico St. Univ.)
USE OF RUMEN TEMPERATURE BOLUSES TO DETECT DISEASE
In this publication last month, a report was summarized on the use of rumen temperature boluses to detect parturition and estrus. In this current study, the technique was evaluated for possible relationship to disease. Angus crossbred steers (n=24) were divided into four groups:
- challenged by exposure for 3 days to 2 steers persistently infected with bovine viral diarrhea virus (BVDV),
- bacterial challenged with Mannheimia haemolytica (MH, once called pasteurella),
- viral challenged as above plus bacterial challenged as above (BVDV + MH),
- control (no challenge)
Remotely-monitored temperature boluses were inserted into rumens before any challenge. With this technique, temperatures were recorded 3 days before BVDV exposure through 14 days after MH challenge. In addition, rectal temperatures were measured at 0, 2, 4, 6, 12, 18, 24, 36, 48, 72, and 96 hours after MH challenge.
Compared to controls, maximum rumen temperature was 1.4, 2.2, and 2.3 degrees F. higher for BVDV, MH, and BVDV + MH steers, respectively. Rumen temperatures averaged 0.23 degrees F. lower than rectal temperatures and the two measures were correlated at 0.89. The authors concluded that rumen temperature boluses could be used to detect temperature changes associated with disease. (J. Animal Sci. 89:1123; Oklahoma St. Univ.)
FERTILIZE OR SUPPLEMENT ?
Over three years, 135 crossbred steers initially averaging 726 lb were used to compare effects of fertilization, supplementation, or a combination of both during a 160-day grazing season. Treatments were:
- (CON) non-fertilized smooth bromegrass pasture stocked 6.8 animal units per month,
- (FERT) fertilized (80 lb N/ac) smooth bromegrass pasture stocked 9.9 AUM,
- (SUPP) non-fertilized smooth bromegrass pasture, supplementation of 5 lb/hd/day of dried distillers grains plus solubles, stocked 9.9 AUM.
Forage intake was lower for SUPP than for FERT and CON. Total N intake was highest for SUPP, FERT was intermediate, and CON was lowest. N retention was highest for SUPP. N excretion was highest for SUPP, intermediate for FERT, and lowest for CON. Efficiency of N use by individual animal did not differ. However, over the complete system, SUPP resulted in 144% higher efficiency of N use over FERT. The authors concluded that DDGS can be used as a substitute for forage and N fertilization by improving performance and efficiency of N use. (J. Animal Sci. 89:1146; Univ. of Nebraska)
SODIUM CONSUMPTION IN THE US
Conventional wisdom holds that people in the US consume too much sodium and that this is increasing over time. Consumption of cured meat products such as frankfurters is sometimes implicated in this regard. An analysis was done of 38 research studies conducted from 1957 to 2003. Urinary excretion levels were used as a measure of sodium intake; there was no significant increase over time. Also, there was no difference among males, females, whites, and blacks. However, even though sodium intake does not appear to be increasing, the average level of intake is well above current dietary guidelines. (Am. J. Clin. Nutr. 92:1172; Harvard School of Public Health)