Calf management to consumer acceptance, Part 1

The following research highlights are provided by Harlan Ritchie, Steven Rust and Daniel Buskirk, all of whom are beef cattle specialists at Michigan State University, East Lansing, as part of their Winter 2004 Beef Cattle Research Update. The following are reviews of research projects recently reported at scientific meetings or in scientific publications.

Growth factor may enhance beef cattle efficiency
Alberta, Canada, researchers recently isolated and cloned a DNA sequence that encodes a 53-amino acid protein, bovine epidermal growth factor (EPG). Previous research in rodents and rabbits demonstrated EPG has the ability to stimulate proliferation of a number of cell types, including the epithelial cells that line the intestine. This work also indicated EPG can improve the absorption of nutrients across intestinal membranes. Furthermore, oral administration of EPG reduced the incidence of intestinal infections and prevented weight gain reduction that results from infection.
Future research by Alberta scientists will focus on the biological effect of bovine EPG in cattle. The objective will be to determine if EPG has the ability to enhance the efficiency of nutrient absorption and reduce intestinal disease in beef cattle. The authors stated that because of the positive effects of EPG on intestinal function, it may have great potential as a feed additive in cattle diets.
(Bilodeau-Goeseels et al. 2003. Agriculture and Agri-Food Canada, Lethbridge Research Centre)

Leptin gene polymorphism associated with increased marbling
Canadian scientists recently reported a polymorphism in the leptin gene of cattle that is associated with a change in body composition, most notably an increase in marbling. In this South Dakota State University (SDSU) study, genotypes for the polymorphism were determined on 492 crossbred calves. Individual animals were genotyped as CC (homozygous for the polymorphism), CR (heterozygous) or RR. Of the 492 calves, 118 were CC, 276 were CR and 98 were RR.
After weaning, the calves were finished in a commercial feedyard. Carcass traits were evaluated at a packing facility at an average age of 433 days. Carcass data were adjusted to three different end points — a carcass weight of 723 pounds (lb.), a fat thickness of 0.45 inches (in.), and an age of 433 days — in three separate analyses.
Genotype was not significantly associated with carcass weight or ribeye area in any of the three analyses. Associations of genotype with fat thickness; kidney, pelvic and heart (KPH) fat; and cutability were small and generally not statistically significant.
However, associations of genotype with marbling score were statistically significant in the age- and fat-adjusted analyses and approached significance in the weight-adjusted analysis. Individuals with two copies of the C allele had marbling scores about 20 units higher than those with zero copies (approximately 407 vs. 386). Those with one copy were somewhere in between.
The authors concluded that the magnitude of difference observed in this study may be sufficient to justify genotyping of herds or populations in which most market animals have marbling scores near a quality grade or price threshold.
(Bierman et al. 2003. South Dakota Beef Report)

Effect of scours on calf weaning weight
Montana State University (MSU) researchers evaluated health and performance records of 3,637 calves from inbred and outbred populations during a 14-year period. The inbred cattle were linebred Herefords. The outbred cattle consisted of four genotypes: 1) Hereford, 2) Angus x Hereford, 3) Simmental x Hereford and 4) Tarentaise x Hereford.
During the 14-year period, the average incidence of scours was 35%; the range was 13% to 64%. The incidence of scours was significantly higher for inbred than outbred calves (41% vs. 28%). The incidence of scours was significantly higher in calves born to 2-year-old dams, and it decreased with increasing age of dam.
Scours significantly affected calf weaning weight. Throughout all years, scouring calves weighed 458 lb. at weaning while calves not affected by scours weighed 478 lb. Outbred calves were significantly heavier than inbred calves (483 lb. vs. 452 lb.).
The authors concluded that the economic benefit of managing to reduce the incidence of scours should exceed the expense to reduce the economic loss that can occur when calves are afflicted with scours.
(Anderson et al. 2003. Prof. Anim. Sci. 19:399)

Economically optimum rate of nitrogen fertilization
Cool-season grasses are an important component of forage systems in various regions of the United States and Canada. Production of these grasses is largely dependent on the availability of nitrogen (N) in the soil. Knowing the economically optimum N application rate (cost of N vs. increased yield) for these grasses at levels that do not adversely affect the environment is critical.
The objective of the Pennsylvania State University (Penn State) trial was to determine the N application rate for three cool-season grass species that would optimize economic return while minimizing the amount of N remaining in the soil. Four N rates were applied to established stands of orchard grass, tall fescue and timothy grass for three years. They were harvested three to four times per year.
Results showed the economically optimum N rates were 203 lb., 263 lb. and 204 lb. of N per acre, or 54 lb., 62 lb. and 62 lb. of N per ton of forage, harvested for orchard grass, tall fescue and timothy, respectively. Apparent N recovery ranged from 34% to 80% and was greatest at or near the economically optimum N rate. Soil N concentration was generally not elevated above background levels at the economically optimum N rate.
The authors concluded that the economically optimum N rate for these three grasses is greater, at approximately 11-15 lb. of N per ton of forage, than current recommendations for the northeastern quadrant of the United States, and soil N is not adversely elevated at this level of N application.
(Hall et al. 2003. Proc. American Forage and Grassland Council Conference)

Characterizing beef cow enterprises in eight Northern Great Plains states
SDSU researchers summarized data collected from 185 cooperating cow herds from 1991 to 1999 in eight Northern Plains states (North and South Dakota, Montana, Wyoming, Minnesota, Iowa, Nebraska, and Kansas). Data were collected and analyzed by Standardized Performance Analysis (SPA) guidelines.
Compared to industry averages, these operations were large, averaging 508 breeding females. In addition to production data, 148 of the cooperators provided financial information. Although the results reported here (see Table 1) are not necessarily applicable to other regions, they provide benchmark data regarding practices, production levels and financial performance of enterprises in a major cow-calf producing area of the United States. Table 1 provides an abbreviated summary of results.
(Dunn et al. 2003. South Dakota Beef Report)

Table 1: Characteristics of cow herds in eight Northern Plains states

Acres per exposed female	21.3
Pregnancy percentage, %	93.0
Calving percentage, %	91.4
Weaning percentage, %	86.7
Female replacement rate, %	19.7
Avg. age at weaning, days	199.0
Avg. weaning weight per calf, lb.	519.0
Pounds of calf weaned per female exposed	451.0
Total assets per beginning-year female,	$2,087
Total expenses per beginning-year female,	$397
Total revenue per beginning-year female,	$430
Net income	33
Return on assets, %	3.1