Maternal Immunity and Calf Health

Glenn M. Rogers, DVM, MS, DABVP
Beef Veterinary Operations
Pfizer Animal Health

Calf health programs typically focus on products administered directly to calves, such as vaccination for clostridial and respiratory disease. However, the most important component of a comprehensive calf health management program may be the health management program of the cow herd of origin. Heifer and cow health management, including sound nutrition, immunization and practical ranch biosecurity, are an integral component of calf health. Perino stated that acquisition of maternal immunity is the “single most important factor influencing the risk of infectious morbidity and mortality prior to weaning.”1 Further work and a growing body of evidence suggest maternal health and immune status is crucial for longer term calf health and performance.

While compliance and documentation of recommended herd health practices for calves has historically been difficult, especially with regards to a free flow of accurate information from previous production phases, capturing the specific health management program of the cow herd of origin has been even more challenging. Advances in data capture capabilities and emphasis on vertical coordination could accelerate the recognized importance and application of this information. Research focused on the impact of colostrum management and fetal programming, coupled with an increased understanding of BVD control at the ranch level, accentuates the need to begin looking beyond direct calf health inputs to the potentially long-term impacts of maternal nutrition, health and immune status on calf growth, health and reproductive performance.
           
Colostrum Management
Wittum, et al. demonstrated that beef calves experiencing inadequate passive immune transfer (from colostrum) are nine times more likely to become sick preweaning, five time more likely to die preweaning and three times more likely to experience feedlot morbidity.2 A dairy study with Brown Swiss heifers fed two levels (2 liters or 4 liters) of high quality colostrum within the first hour of birth resulted in a doubling of veterinary costs for the heifers fed the lower colostrum quantity. Heifers fed the higher colostrum volume also gained more weight (2.27 pounds versus 1.94 pounds per day; P<0.001). Overall, feeding the greater volume of colostrum and then treating animals identically in terms of herd management translated into an advantage of > 1200 lbs of actual milk produced per cow over the first two lactations. The direct economic return to the producer was approximately $160 per cow in additional milk produced over two lactations.3

From a practical beef cow/calf perspective, the most important method to increase colostral immunity is to increase understanding of  the risk factors associated with inadequate passive transfer and modify the factors that can reasonably be corrected. Managing dystocia, rigorous culling of cows with bad udders, maintaining adequate body condition at calving, providing adequate trace mineral nutrition and a sound cowherd immunization program are some of the methods to positively modify factors contributing to inadequate transfer of colostral antibodies.4

Maternal Nutrition and Fetal programming
Maintaining adequate body condition, especially at the critical times of calving and breeding (~ 5 for cows and ~ 6 for heifers) has been shown in numerous studies to positively impact reproductive performance. Heifers and cows calving in poor body condition may give birth to calves with reduced vigor and reduced colostral absorption. Ultimately, calving in poor body condition can result in a long term reduction in calf health and growth performance.

Fetal programming is the idea that a maternal stimulus or insult at a sensitive period in fetal development could have long term effects on an individual. The concept of fetal programming has become a deeply rooted concept in human medical science largely due to the pioneering epidemiological studies conducted by Dr. David Barker. Between September 1944 and May 1945, the occupying German forces virtually starved the population of western Holland. Although pregnant women received adequate diets when they were liberated, and their infants were born a normal weight, they developed health problems at a much higher rate than the control population in the same country. Specifically, increased numbers of babies who were subjected to under nutrition during the first half of gestation experienced an increased incidence of lifelong health effects including obesity, type II Diabetes, hypertension and cardiovascular disease in later life.5

Fetal programming data is limited in livestock; however, a small number of studies in sheep, pigs and cattle offer some exciting insight and opportunities in understanding the critical role of maternal nutritional and health management and the relationship to fetal development and subsequent long term performance. A recent Nebraska study evaluated the affects of supplementing cows with protein during late gestation (1 lb/head/day of a 42% crude protein supplement). Supplementation did not affect birth weight of calves. However, supplementation impacted heifer calf weight and reproductive performance. Heifers from protein-supplemented cows were heavier at weaning and maintained this advantage through the beginning of the breeding season. Heifers from protein-supplemented cows tended to have higher pregnancy rates (94% vs. 73%), calved earlier, and had a higher proportion of unassisted births (69% vs. 38%).6 This study contributes to the growing evidence that health and nutritional management of the cowherd may have long term affects on calf health and performance.

BVD Control at the Ranch
BVD is an immunosuppressive virus and an important cause of reproductive and respiratory losses. Technologic and management tools are currently available to eradicate BVD from individual ranches and prevent the virus from moving off the ranch to wreak havoc at the next phase of production. Fetal protection against BVD (Types I and II) is best achieved by administration of a vaccine with proven fetal protection.7 Complete fetal protection to avoid calf losses must be a combination of a sound prebreeding vaccination program, biosecurity, strategic diagnostic practices and timely identification and removal of persistently infected animals. When choosing vaccines for fetal protection, appropriately labeled products with research proven performance should be selected.

While an effective BVD vaccination program should be standard practice, whole herd testing to identify BVD-PI animals should be based on risk analysis and health monitoring practices. For example, herds with good records and excellent reproductive performance may not receive a positive cost: benefit from whole herd testing. In this scenario, maintaining sound BVD vaccination practices and focusing on herd biosecurity and BVD-PI testing of all new arrivals may be the most prudent plan.  All cow/calf operations should have a carefully crafted plan to manage and prevent BVD. When risk analysis results warrant, selective or complete herd testing may be indicated. Marketing opportunities exist for providing BVD-PI test negative animals. Development of maternal immunity against BVD through timely vaccination, biosecurity and strategic testing is the only effective method of controlling this disease.
           
Maternal Vaccination
In addition to BVD immunization, heifer and annual cow vaccination for IBR, Campylobacter (Vibrio) and Leptospirosis (including hardjo-bovis) should be a routine herd practice. Administration of reproductive vaccines prior to breeding makes good immunologic sense. This approach allows for a peak in immunologic responses in correlation with breeding season exposure. Failure to vaccinate at the correct time may result in decreased health performance, even when the best products available are used.

The developing heifer prebreeding vaccination program is the foundation for maintenance of lifetime cowherd immunity. Substantial carry-over effect in herd immunity occurs when a sound health management program for heifers is implemented. Even in herds that have extended breeding seasons or choose not to implement prebreeding vaccination in the mature cowherd, improvements in heifer prebreeding management can usually be successfully implemented.

Neonatal calf diarrhea (scours) is a leading cause of calf death. Multiple factors, including colostral deficiency and pathogen exposure, are typically implicated in calf scours outbreaks. A planned approach to reduction of pathogen exposure, such as the Sandhills Calving System8, is the most effective method of scours control. E. coli, rotavirus and coronavirus are the most frequently diagnosed infectious causes of calf scours. Precalving cow vaccination to enhance concentrations of antibodies in colostrum received by calves has shown benefits in reducing the incidence and severity of disease.

The timing of maternal vaccinations is critical to maximizing the protective effects of passively acquired colostral antibodies in calves.

Summary
Effective calf health management programs should extend beyond direct calf health inputs and focus on the health management program of the cowherd. Improving calf health through maternal immunity requires a focused effort to improve colostrum management, herd nutrition, biosecurity and maternal immunization. Consult your veterinarian for development of a comprehensive health program for your unique operation.

 

References