Management of the calving season is critical to optimize the weaned calf crop. Research indicates that 57% of mortality is seen in the first 24 hr and 75% within 7 days of birth. In addition, there are significant risk factors for increased calf morbidity at the time of calving that can lead to increased mortality and decreased calf performance. Factors to consider in calving management include dystocia management (of primary concern in first-calf heifers), calving environment (including ambient temperature), passive transfer, and cow-calf pair management. (See Management of Reproduction: Cattle Management of Reproduction: Cattle read more .) A visit to the farm or ranch ~4 wk before the onset of the calving season provides the opportunity to evaluate the preparations made by the producer and to recommend any changes.
Keeping records on calving ease and morbidity and mortality incidence allows for analysis of risks and risk groups and detection of any increased incidence of disease. At least one additional visit should be made to the farm 2–3 wk after calving has begun to assess the management and environment. Morbidity and mortality incidence levels may be established; if these are exceeded, the herd health veterinarian should be called and an investigation begun.
The most common cause of calf morbidity in the neonatal period is diarrhea (see Diarrhea in Neonatal Ruminants Diarrhea in Neonatal Ruminants Neonatal diarrhea in ruminants remains the most important cause of death in calves under one month of age. Various bacterial, viral, and protozoal agents are recognized as causative agents,... read more ). It is sometimes not possible and many times not important to differentiate diarrheas associated with different etiologic agents, especially when diarrhea occurs in the 7- to 14-day range. Control for pathogenic agents of neonatal diarrhea involves segregation of sick animals from the healthy nursery to decrease environmental contamination and transmission. In addition, Escherichia coli and Salmonella control involves biosecurity rules to prevent the purchase and introduction of new calves or cows during the calving season. Sick calves should be isolated quickly to prevent further environmental contamination. Once the environment is contaminated, moist, cool conditions allow survival of infectious agents for an extended period. Cryptosporidia are especially suited to survival in the environment, and prevention of contamination in the healthy nursery is critical. Commercial vaccines for rotavirus, coronavirus, E coli, and Clostridium perfringens types B and C may be given to cows and heifers before calving to increase levels of specific immunoglobulins in colostrum. An initial vaccination and booster followed by a yearly booster is generally required. If a booster vaccination is needed, it should be given at least 2 wk and not more than 6 wk before calving. Clinical trial data are not consistent; some trials report no effect, whereas others report significant decreases in morbidity. Vaccination may be a useful adjunct to proper management in controlling neonatal diarrhea, but the key is environmental control.
An excellent environmental control program is the “Sandhills calving system” developed at the University of Nebraska. In this system, pregnant cows are wintered in an area separate from the calving area. When the first cow calves or is about to calve, the entire herd is moved to the first calving pasture. Cows stay here for 2 wk; after this time, all cows with calves stay on pasture 1 while all cows yet to calve move to pasture 2. After 1 wk on pasture 2, all cows with calves stay and all pregnant cows move to pasture 3. This continues for the next 6 wk. Cow-calf pairs can be combined when the youngest calf in the group is 4 wk old and at low risk of diarrhea. This system assures that each calf is born into a clean environment, so disease transmission is minimal to nonexistent. Herds that had severe morbidity and mortality from scours before using the system may have almost no health concerns after its adoption.
In this and in all calving systems, heifers should be wintered and calved separately from adult cows, because heifers have lower immunity to pathogens than cows.
Castration and Dehorning:
Castration of male calves in early life (before 3 mo of age) is less stressful to calves than castration performed later, when testicular size is dramatically increased. A number of methods may be used, including the open surgical technique, the use of rubber rings, and the Burdizzo method. Calves castrated surgically initially exhibit more agitation than calves castrated with rubber rings, but both groups resume normal behavior soon after the operation. Dehorning early in life is also less stressful than when performed later, when horns have increased in size. Horns are mostly a problem for the feeding period (ie, horned calves require more bunk space), and they may cause bruising in penmates. Such problems are best managed by polled breeding or early dehorning.
Individual identification of cows and calves allows for selection based on performance as well as for tracing the animal to its herd of origin to track or contain disease. Plastic ear tags are the most commonly used method of individual identification. Branding as a method of herd identification is coming under increasing scrutiny for product quality and animal welfare reasons. Commercial products are currently on the market that allow individual electronic identification. Such initiatives may eventually replace current identification systems.
Vaccines are available for viral and bacterial respiratory pathogens. Residual passive immunity in young calves may limit the detectable antibody response to vaccination at an early age, but use of MLV infectious bovine rhinotracheitis and bovine viral diarrhea vaccines stimulates a significant cell-mediated immune response in calves with residual passive immunity to these diseases. Specific age recommendations for initial vaccination are made by vaccine manufacturers. Calves vaccinated at branding time or pasture turn-out may be sensitized to the antigens and respond with an anamnestic response when given another vaccine at arrival in the feedlot. Recommended vaccination programs include clostridial and viral respiratory vaccination at the time of branding. A number of “value-added” calf programs have been initiated, some of which require a vaccination program at branding time. Pneumonia incidence is typically low during the summer grazing periods, making clinical effectiveness of a vaccination program against respiratory disease difficult to demonstrate. Primary sensitization to increase subsequent vaccination response before weaning may be the major benefit of such a vaccination program. A repeat vaccination against viral respiratory agents is often administered to calves before weaning. Vaccination for Mannheimia has been recommended for inclusion in some preweaning or weaning vaccination programs as well.
Infectious keratoconjunctivitis (see Infectious Keratoconjunctivitis Infectious Keratoconjunctivitis read more ) can be a significant problem in suckling calves, and control can be difficult. Vaccination has shown variable results. Challenge with a homologous strain after vaccination may provide some level of control, but challenge with a heterologous strain creates little protection.
Use of hormonal implants as a management practice for suckling calves may increase weaning weights by 3%–5%. Optimal response is seen in healthy calves with adequate nutrition. Heifers kept for breeding should not be implanted if <45 days old, and bulls should never be implanted. (See Growth Promotants and Production Enhancers Growth Promotants and Production Enhancers read more .)
Egg burdens of calves are typically low at spring branding but may rise significantly by midsummer. Deworming of cows in late spring may lead to increased weaning weights in calves. Studies examining the effects of deworming calves only at branding have been few, and results were inconsistent—some showed positive effects, whereas others found no effect. Deworming of calves in addition to cows in late spring appears to confer minimal additional benefit. External parasites of cattle are estimated to be an important cause of economic loss as well. Studies have generally shown a weight gain of 10–20 lb in suckling calves when fly control is provided. The most common method of fly control is the use of insecticide-impregnated ear tags. With the widespread use of pyrethroid insecticides in ear tags, emerging resistance has become a problem, so rotating to organophosphate or endosulfan tags can be helpful. Insecticide sprays and back rubbers can also be effective (and less expensive), but cattle must be forced to use them.
Suckling beef calves are generally not supplemented during the summer grazing period, when milk and an increasing intake of forage provide their diet. Deficiency of trace minerals may be a concern in some areas. Proper nutrition of the herd before calving should provide the calf with adequate reserves at birth. Subsequent supplementation is difficult, however, because trace mineral mix intake in calves is sporadic at best. Creep feeding may increase the reliability of intake, but it is an expensive substitute for available forage, and the response is highly variable. Creep feeding for 3–4 wk before weaning may be an effective way to reduce stress and disease at weaning. (Also see Nutrition: Beef Cattle Nutrition: Beef Cattle read more .)
Weaning is stressful because the calf is removed from its dam and has to adjust to a different diet and environment; population density is increased, leading to potential for increased disease exposure and transmission. Management procedures should aim to minimize stress to calves while ensuring they are in sound condition nutritionally and immunologically. Castration and dehorning should be performed well before weaning. Completion of vaccination, deworming, and implant procedures before weaning allows calves to be weaned without handling.
Early weaning of beef calves at 90–150 days of age may create more efficient use of feed resources by directly supplementing calves to maintain weight gain rather than supplementing cows to produce milk. Weaning times as early as 30–60 days can increase reproductive performance of cows and heifers. Cows and heifers cycle and rebreed earlier in the calving season, and pregnancy rates are higher in a limited breeding season after early weaning. Nutritional needs of the weaned calves must be met carefully to ensure acceptable health and performance. Weaning this early should be done only in an emergency situation to salvage the reproductive future of cows in extremely thin (BCS <4) condition at calving. The goal is to prevent this situation through strategies that improve precalving BCS (see Breeding Soundness Evaluation: Breeding Soundness Evaluation: In most regions of the world, there is an optimal period for females to calve, suckle, and rebreed. This period is mostly related to nutritional opportunity, although other environmental factors... read more ). Weaning at 150–170 days of age decreases lactational stress on cows when forage resources are limited and improves cow condition. Reproductive performance in the breeding season is not affected by weaning at this time. When forage resources are limited, weaning calves to decrease the nutritional requirements of the cows allows them to regain condition before winter with less or no supplementation. It is more efficient to wean the calves and feed them directly than to feed the cows more to increase milk production late in lactation.