Beef Cattle Browsing
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.
NEW TRICHOMONIASIS REGULATIONS
Trichomoniasis (Trich) is a venereal disease of cattle that causes infertility and abortion. Actual incidence of the disease in Texas is unclear, however, its economic impact on infected herds is significant, resulting in longer breeding periods, lowered calf crops, and reduced income. No effective vaccine or treatment exists for bulls. If infected, most cows will clear up with 4 to 5 months of sexual rest. There is a vaccine for cows that will help in shortening the recovery period and maintaining pregnancy in exposed cows but it has limited if any documented impact on preventing infection.
The Texas Animal Health Commission has announced new regulations aimed at controlling Trich. Beginning April 1, 2009, breeding bulls entering Texas must be: 1) 24 months of age or younger and certified by the breeder as virgin or; 2) tested negative within 30 days prior to entry, with costs paid for by the producer, and those testing positive will not be allowed to enter the state except for slaughter. All bulls must have an officially accepted form of individual identification, Trich test document, veterinary inspection certificate, and any other applicable health documents (such as tuberculosis or brucellosis, depending on the originating state). The regulations will not apply to bulls going to slaughter. Incidences of Trich must now be reported to animal health officials.
Beginning January 1, 2010, bulls “offered for sale, lease, exchange, or otherwise change possession for breeding within Texas” must be “certified as virgin bulls or be tested negative prior to selling, loaning, exchanging, giving, or otherwise changing the possession of a breeding bull”. Bulls will have to be identified with a USDA ear tag, RFID tag, or breed registry tattoo or brand. Complete information can be accessed at http://www.tahc.state.tx.us/. (Texas Animal Health Commission news release 2/27/09)
RESIDUAL FEED INTAKE INHERITANCE
Feed efficiency is receiving greater attention in genetic evaluation programs. Until recently, feed efficiency was usually expressed as feed required per pound of gain, also called feed conversion. This measure is usually closely related to level of feed consumed and rate of gain. Animals that eat more in relation to their size tend to be faster gaining animals and have better feed conversion. Another measure also is being used, residual feed intake (RFI). RFI measures feed consumption relative to what would be predicted based on an animal’s body size and rate of gain. So, low RFI animals are more efficient, i. e., they eat less than expected compared to their performance. And, unlike feed conversion, RFI has been shown to be unrelated to level of feed consumption or rate of gain.
Australia has been in the forefront of RFI study and implementation. In their bull tests, feed consumption is measured, RFI is calculated, and Estimated Breeding Values (EBV) are reported in breed association genetic evaluations. Kansas State University researchers artificially inseminated Angus-cross commercial cows to three low-RFI EBV and three high-RFI EBV Australian Angus bulls. Resulting heifer calves were fed, with consumption measured for each heifer. Average daily gain and feed conversion were similar for the two sire groups. However, heifers sired by low-RFI bulls tended also to be low in RFI, and heifers by high-RFI bulls tended to be high in RFI. RFI appears to offer promise in genetic selection to improve feed efficiency. However, just as with feed conversion, RFI requires measurement of individual feed consumption. (Kansas State University Beef Cattle Research Report – 2008, p. 55)
GROWING RATIONS VS. PERFORMANCE AND CARCASS
Texas A&M researchers studied the effects of four growing rations on feedlot performance and carcass characteristics. For the first 56 days on feed, individually fed steers initially weighing 651 lb were fed one of the following: 1) full-fed low-corn, 2) full-fed high-corn, 3) energy consumption equal to ration 1 by limit-feeding high-corn, 4) energy consumption halfway between rations 1 and 2. All steers were then fed ration 2 to 140 days on feed.
Based on ultrasound measurement, during the growing period rations 2 and 4 increased intramuscular fat and rations 1 and 3 decreased subcutaneous fat. But there were no significant differences in either of the ultrasound fat measurements during finishing or at the end of feeding. However, actual marbling scores were significantly higher and carcass fat cover tended to be higher for rations 2 and 4. So, higher energy consumption during the growing period increased both external and internal measures of carcass fat. (J. Animal Sci. 87:1540).
SYSTEMS FOR ARTIFICIAL INSEMINATION
The Beef Reproduction Task Force recommends protocols for use in artificial insemination. With separate considerations for heifers and cows, there are systems for insemination with heat detection alone, with heat detection followed by one timed-AI, or with one fixed-time AI only. For all three there are systems with and without administration of a progestin. The systems can be viewed at http://westcentral.unl.edu/beefrepro/resources.html.
EFFECTS OF COW WINTERING SYSTEMS
University of Nebraska researchers studied wintering of Red Angus-Simmental cows over three years. Cows grazed either winter range (WR) or corn residue (CR) either supplemented (SP) or non-supplemented (NS) with 2 lb/day of 28% crude protein cubes. Compared to NS, SP cows weighed more at calving and pre-breeding, Body Condition Score was higher pre-breeding, and calf birth weight tended to be heavier. Compared to WR, CR cows were heavier at pre-breeding and weaning, Body Condition Score was higher at calving and pre-breeding, and calf birth weight was heavier. Pregnancy rate was not affected. Calf weaning weight was lower out of NS cows on range compared to the other three groups.
All steer calves were fed after weaning for 222 days. There were no differences among the cow treatment groups in ADG, fat cover, ribeye area, or Yield Grade. Slaughter weights were heavier for calves out of SP WR than NS WR cows. Compared to NS, calves from SP cows had higher marbling scores and higher percent Choice but similar Yield Grades. Overall, supplementation of cows increased value of calves at both weaning and after slaughter on both range and residue. (J. Animal Sci.)
EFFECTS OF ENDOPHYTE-INFECTED FESCUE ON SPERM
University of Arkansas, New Mexico State University, and USDA researchers studied effects of endophyte-infected (EI) fescue in bulls of from 1/8 to 3/8 Brahman breeding grazing from mid-April to mid-August. Compared to non-EI, EI-grazed bulls had fewer motile sperm, poorer motility, and slower velocity. Scrotal circumference and percent live sperm did not differ. (J. Animal Sci. 87:1184)
BEEF IMPORTS VS. EXPORTS
In 2007 we imported almost 1 million tons of beef from the eight leading countries. This decreased 16% in 2008. Canada (34%), Australia (27%), and New Zealand (21%) made up the bulk of the 2008 imports. Combined, less than 20% came from Argentina, Brazil, Central America, Mexico, and Uruguay. On the other hand, our exports to the eight leading countries increased 28% over 2007, totaling almost 1 million metric tons in 2008. Mexico (40%) and Canada (16%) got the majority of our shipments with Egypt, Hong Kong, Japan, South Korea, Russia, and Taiwan getting the rest. (http://www.cattlenetwork.com)