SYMPOSIUM PAPER: Health Management Programs: Integrating Biological and Management Principles in Analysis, Design, and Implementation of Programs for Two-Year-Old Beef Cows1

Professional Animal Scientist, Jun 2005 by Stokka, G L, Lardy, G P

Abstract

Designing a health program for cow-calf operations requires a scientific approach and knowledge of ranch resources, environment, genetics, nutrition, management, and a biosecurity program. These areas are interrelated and must be considered to assess and manage the risk of disease. A comprehensive health program should 1) identify potential risks related to production and disease; 2) determine and understand appropriate benchmarks for production, disease, and production costs; 3) diagnose the problem when benchmarks are not achieved; and 4) use appropriate records to verify results. The 2-yr-old cow is at the greatest risk of failing to meet financial and production benchmarks because of her additional nutritional requirements. This group may also have reduced herd immunity and generally produce lower quantity and quality of colostrum, resulting in greater risk of disease and potentially reduced production in their offspring. As a result, this group may require more inputs in all aspects of the health program. Risk assessment includes the specific risks to biosecurity, such as raising or purchasing females that are persistently infected with bovine viral diarrhea virus (BVDV) or Mycobacterium paratuberculosis. Risk assessment of exposure to common infectious reproductive disease pathogens, such as infectious bovine rhinotracheitis (IBR), leptospirosis, trichomoniasis, vibriosis, and neopsora should be conducted and vaccination protocols implemented as needed. Finally, an understanding of the concept of herd immunity is important when defining realistic expectations regarding immunizations. With proper implementation, health programs can significantly reduce the risk of disease and economic loss.

(Key Words: Beef Cattle, Disease, Health, Two-Year-Old Cow, Vaccination.)

Introduction

The goal of a health program is to decrease health risk and improve the opportunity for profit. Input costs to health programs are a minor component of annual cow costs. On average, veterinary costs, which typically include vaccinations, deworming, pregnancy diagnosis, consultation, and other services, will range from $7.70 to $13.00/100 kg ($3.50 to $6.00 per cwt) of weaned calf (Dunn, 2000a). Discussion of health programs is often confined to vaccination protocols. Vaccination protocols are, in many instances, based primarily on convenience and price instead of science and logic. Proper analysis of health programs must begin with an assessment of risks to profitability. This step will usually result in an analysis of production outputs, but needs to include production costs as well. In addition, an assessment of health and its contribution to production is necessary to define a health program that is manageable and based on risk assessment and effective prevention strategies. The purpose of this manuscript is to review health and management programs that impact productivity and profitability of 2-yr-old beef cows.

Establishing the Benchmark

Production numbers or benchmark numbers that veterinarians and producers can use as standards of comparison are useful. A 1997 NAHMS study provides some comparison numbers (NAHMS, 1997). This study reported approximately 5.5% of all beef calves are lost from birth to weaning. Of this number, 2.1% were born dead, 1.1% died within 24 h, an additional 1.1% died prior to 3 wk of age, and 1.2% were lost between 3 wk of age and the time at which they were weaned. The actual etiologies for these losses were not discussed, but based on our knowledge of calves this age, certainly scours, respiratory disease, gastric ulcers, congenital defects, and weak calves all likely contributed to this number. Contributing factors were identified as weather, infectious disease, and calving problems. The addition of females that experience abortions and those that were not pregnant at the time of pregnancy diagnosis results in a quantification of production that can be very meaningful when assessing profitability. The percentage of pregnancy losses will range from 1 to >2%, and the percentage of females that failed to breed will range from 5 to 10% (NAHMS, 1999; SPA, 2002, 2003). In the younger female group, this number is usually higher than in the adult population (Geary, 2003). The addition of these numbers results in a weaned calf crop of 5.5 1 10 = 16.5% loss or an 83.5% calf crop. Is this number in line with our expectations or should changes be made to the health program to improve upon these numbers? Each category needs to be dissected as each one might have several causes. For example, the percentage of open cows by age group can usually be reduced by increasing the body condition score (BCS) of the age group in question if the group has a combined BCS

Multi-Factorial Nature of Disease. When assessing losses to disease, it is important to understand that the actual cause of disease is most often multi-factorial. Infection with a pathogen does not usually result in disease in the absence of other contributing factors. For example, scours in neonatal calves is almost always a result of several other events and factors that resulted in clinical disease (Ferez, 1990). An acceptable way to quantify the causative factors with this clinical disease would be to construct a regression equation that includes all of the causative factors and how much they contribute to the disease. A regression equation Y = b^sub 0^ b^sub 1^X^sub 1^ b^sub 2^X^sub 2^ ... b^sub k^X^sub k^, for scours may look like this: Y = 0.2 0.2(X^sub 1^) 0.1(X^sub 2^) 0.1(X^sub 3^) 0.15(X^sub 4^). . ., where X^sub 1^ = degree of failure of passive transfer, X^sub 2^ = nutritional status of the cow and newborn calf, X^sub 3^ = environmental influences such as rain or snow and cold temperatures, and X^sub 4^ = exposure to pathogens. Although this approach helps to provide an understanding of the risk factors and explain the cause of the disease, the diagnostic ability to identify or even influence some of these factors is not always that apparent. Thus, producers become frustrated with control programs that only focus on one or two factors.