University of Illinois researchers used 64 Simmental x Angus heifer calves to evaluate the effects of weaning age and creep-feed protein levels on performance, reproduction and milk production of replacement heifers.
Weaning ages were either 89 or 232 days. Creep diets were either 12% or 17% crude protein (CP). All calves were provided free access to the 12% CP diet until their dietary treatments started, which was 57 days after early weaning (146 days). Calves remained on their respective diets until one month after normal weaning (262 days).
Early-weaned (EW) heifers fed the 17% diet gained faster (2.78 vs. 2.60 lbs./day) and weighed more at normal weaning (NW) age than those receiving the 12% diet. Feeding the 17% diet to NW heifers decreased their performance from 3.02 to 2.69 lbs./day.
The EW heifers were lighter than NW heifers from puberty through breeding. Nevertheless, more EW heifers than NW heifers were pubertal at 8 months of age (81.3% vs. 59.4%), but there was no difference at either 10 or 12 months of age, and pregnancy rates were higher for EW than NW heifers (90.0% vs. 74.2%).
There were no significant differences between the 12% and 17% diets in body weight at puberty, percent of heifers pubertal by 8, 10 or 12 months of age, or reproductive rate. Neither weaning age nor creep protein level influenced heifer milk production or performance of their calves.
These results indicate early weaning improved heifer reproduction without affecting milk production. Also, it appears that providing additional protein in the diet of EW heifers can improve post-weaning weight gain.
In a companion paper, the Illinois workers reported results of another study in which 136 NW heifers were fed creep diets of either 12% or 17% CP. The results differed from the previous study in that milk production was depressed in heifers fed the 17% diet (10.8 vs. 12.3 lbs./day). It would appear that nothing is to be gained, and milk production could be reduced, by feeding a 17% CP creep diet to NW heifer calves destined to become herd replacements (Sexten et al. Midwestern ASAS, Abstracts 283 and 284).
Michigan State University Beef Cattle Research Update, Summer issue
Grant Lastiwka, pasture specialist at the Lacombe Research Centre in Lacombe, Alberta, Canada, recently presented an interesting review of non-conventional feeding systems for cow-calf producers in Western Canada. In this locale, the winter-feeding period may last for 160 to 200 days, similar to U.S. northern regions.
Annual feed cost per cow is about ⅔ of her total annual costs, with about ⅔ of feed cost tied to the winter feeding period. Normal grazing accounts for the other third of feed cost.
Lacombe research showed a 47% savings with swath grazing vs. a conventional winter hay-feeding system. Over a 200-day winter, the savings were $118 (CAN)/cow or a drop in cost of production of 24¢/lb. for a 500-lb. calf.
The Lacombe work also showed bale grazing can save $21/cow over a 200-day winter, reducing cost of production by 4¢/lb. for a 500-lb. calf.
Lastiwka cautions there are times and places where these alternative systems may cost more than conventional winter-feeding systems; for example, when alternative feedstuffs are cheap and grazing land ownership or rental costs are high. Consequently, there is still a place for conventional winter-feeding systems, he says.
Nevertheless, producers should continually examine and challenge traditional systems as a means of lowering costs and enhancing profitability. The grazing of banked or stockpiled forage offers an opportunity for extending the grazing season and accomplishing these goals (Lastiwka. 2004. Lacombe Research Centre. Newsletter, Vol. 8, Issue 4).
Michigan State University Beef Cattle Research Update, summer 2004
More than 20 USDA-certified programs use beef phenotype as the principle selection tool. Animal scientists at Texas Tech University conducted a study to determine whether beef cattle phenotypes selected by an individual packer and their alliance partner can be used to identify carcasses for a guaranteed tender beef program.
Research suggests that 10-25% of beef steaks sold at retail are tough, and tenderness accounts for 50% of consumers' overall acceptability of steaks. Moreover, researchers have found that consumers are willing to pay more for beef cuts that are more tender. Certified programs have been developed to provide consumers with a more satisfactory beef product.
For the study, cattle were visually selected from four feedyards to represent six phenotypes — English (EN), ¾ English-¼ Brahman (ENB), ½ English-½ Exotic (ENEX), ½ Engish-¼ Exotic-¼ Brahman (ENEXB), ¾ Exotic-¼ Brahman (EXB) and ½ Exotic-¼ English-¼ Brahman (EXENB).
The carcasses were processed at a commercial beef packing facility and strip loins were collected after chilling for 48 hours. They were aged for 14 days at 2° C and then frozen at -20° C for 3 to 5 days before 2.5-cm steaks were cut for Warner-Bratzler shear force (WBSF).
EN phenotypes had the highest adjusted fat thickness and highest yield grade carcasses, while EXB measured lower adjusted fat thickness and yield grades numbers than all phenotypes except EXENB. Researchers found that no differences were detected among phenotypes for WBSF values or sensory panel ratings for tenderness, juiciness or beef flavor intensity.
The scientists concluded that results from this study indicate all phenotypes represented here could be managed to produce tender beef cuts (Hilton et al., 2004 J. Anim. Sci. 82:1190-1194).
USDA Agricultural Research Service (ARS) scientists are targeting where E. coli O157:H7 is found in calves, looking to develop a vaccine to prevent infection. Evelyn Dean-Nystrom and William Stoffregen at the National Animal Disease Center in Ames, IA, studied major organs in calves to determine where E. coli infections are most prevalent.
The intestines are the most common places to find E. coli but Nystrom and Stoffregen also found signs of bacterial infection in the gall bladders of 12 of 13 calves in their study. The calves' gall bladders became inflamed 14 days after they were inoculated with the bacteria, and many were found to also have lesions and E. coli present.
Stoffregen says, “This discovery identifies the gall bladder as a possible niche for E. coli O157:H7 infection in cattle and as a potential source of Shiga toxin-producing E. coli contamination of beef products.”
He adds that including gall bladders in the samples cultured for E. coli may help identify the infected cattle at harvest.
Nystrom also participated in a study with scientists at the Uniformed Services University of the Health Sciences in Bethesda, MD, to develop and test an oral vaccine to eliminate E. coli from cattle. The vaccine contains intimin, a protein found on the outer membrane of E. coli which is used to attach the bacteria to the intestinal walls. The vaccine tests have shown to provide antibodies against E. coli. Tests have also revealed that the antibodies interfere with E. coli colonization.
Nystrom says the vaccine won't affect the colonization of beneficial, non-disease causing E. coli because they don't produce intimin. (August 2004 Agricultural Research magazine, pages 14-15).