Calf Research Update from the 2007 ADSA Meeting
Posted: August 25, 2007
Penn State researchers (Elizondo Salazar et al.) reported that pasteurizing colostrum effectively reduced bacterial populations. Colostrum was pasteurized in 10 mL batches at 145°F for 30 minutes. Several different bacterial counts were measured, but standard plate count, which is a good indicator of total bacteria, was reduced from over 16,000 to 21 cfu/mL after pasteurization. Also of interest, pasteurization reduced IgG by 14 percent in this study, falling to 76.7 mg/mL from 89.1 mg/mL before heating. While this drop in IgG was significant, it was lower than the 25 percent decrease reported in previous research. If IgG losses are consistently 14 percent, then colostrum must contain only 58 mg/mL before pasteurization to retain 50 mg/mL in the pasteurized milk.
Another report (Stabel) demonstrated that feeding pasteurized colostrum and milk replacer to calves reduced the exposure to Mycobacterium avium subsp. paratuberculosis (MAP) compared to feeding the dam's colostrum and milk. Calves were separated from their dams at birth and fed pasteurized or raw colostrum, then fed either milk replacer or whole milk for 3 weeks. From weaning through 12 months of age calves were managed similarly. At 12 months of age calves were slaughtered and 25 tissue sites were sampled for the presence of MAP. Of these, 16 different tissue sites tested positive. In the calves fed dam's colostrum, 14 tissue tests (87.5 percent) were positive (of the 16 tissue types). Only 9 sites tested positive in calves fed pasteurized colostrum (56.25 percent). In addition, blood samples from calves fed their dam's colostrum contained more antibodies against MAP than blood from calves fed pasteurized colostrum. The author concluded that clean colostrum can be used to limit calf exposure to MAP. However, an interesting observation in the study was that feeding pasteurized colostrum did not eliminate MAP infection in calves. Preventative measures should begin at birth (for example not feeding colostrum from infected dams), but also should continue throughout the growing phase.
Penn State research (Heinrichs et al.) showed that plastic hydrometers were just as accurate as glass instruments in estimating colostrum IgG content. Plastic hydrometers calibrated with a colostrum IgG scale, when available, may potentially help increase colostrometer use in the future due to their improved durability.
Enhanced Feeding Systems
British researchers (Aikman et al.) looked at first lactation performance of cows that were fed milk replacer free choice or at one gallon per day through 6 weeks of age. After weaning calves were managed similarly. The calves restricted to one gallon per day tended to weigh less at 12 months of age, but there were no differences between treatments in age at first breeding (13.8 months), age at first calving (23.6 months), daily milk production (60.8 lb), total first lactation milk yield (20,163 lb), or calving interval between the first and second calf (12.8 months). Research from the University of Illinois (Drackley et al.) also reported comparisons of first lactation performance for calves fed control or intensified diets. Control calves received 22 percent protein, 20 percent fat milk replacer at 1.25 percent of birth weight and were weaned at 5 weeks of age. Intensive calves were fed 28 percent protein and 20 percent fat milk replacer at 1.25 percent of birth weight then increased to 2.5 percent of birth weight. Calves on this treatment were weaned at 6 weeks of age. Both groups had free access to starter grain. Calves were managed in groups by treatment until 12 weeks, and then managed similarly to calving. Two trials were conducted with similar treatments.
Data from the two trials were combined to evaluate lactation performance. There was no difference between treatments in age or body weight at first calving. Intensive calves tended to have a longer lactation and produced more total milk than control calves. Milk production to 305 days was greater for the intensive calves in Trial 1 but not in Trial 2.
Researchers from Akey Inc. (Hill et al.) conducted a series of trials to evaluate the effect of feeding rate of a milk replacer with 26 percent protein and 17 percent fat on average daily gain, starter intake, and feed efficiency. In the three trials, 42 calves were fed milk replacer at 1.5, 1.75, 2.0, or 2.5 lb powder per day and weaned at 42 days. Growth measurements were continued through 56 days. In each of the trials, calves fed 1.5 lb/d of milk replacer had the lowest daily gains during the pre-weaning period, but after weaning these calves ate the most starter and had the highest gains. Over the entire 56-day study, daily gains and starter intake were greatest for the calves fed 1.5 lb/d. In other words, there was no advantage to feeding more than 1.5 lb/d of 26/17 milk replacer.
Nonnecke et al. at the USDA National Animal Disease Center reported the results of a trial where calves were fed for no growth, low growth (1.2 lb/d), or high growth (2.6 lb/d) over the first 8 weeks of life. All calves were fed a 30 percent protein, 20 percent fat milk replacer at different rates to accomplish these growth goals. Vitamins were supplemented to the no growth and low growth groups to compensate for their lower milk replacer feeding rates. Vitamins and minerals that are key contributors to the immune system were measured over time in the calves' blood. No differences were found in vitamins A and D or in zinc. Vitamin E was lower at 8 weeks for the high growth treatment. Copper was higher in high growth calves from week 4 to 7. Despite finding these few differences, vitamin and mineral levels for all treatments were within normal ranges for young calves. The researchers concluded that increasing the feeding rate and growth rate of calves did not improve levels of vitamins and minerals important to the function of the immune system.
Impact of Short Dry Periods on Calves
Researchers at USDA (Kuhn et al.) analyzed data from the Animal Improvement Programs Laboratory to see how short dry periods affect calves. They found that calving ease scores were lower (easier births) for cows with dry periods 0 to 45 days compared to cows with 46 to 65 days dry. They suggested that one explanation is calves are smaller when cows have a shorter dry period. Another finding showed that stillbirth rates were lowest for cows with 55- to 60-day dry periods. Stillbirths happened more often in cows with 0 to 30 days or more than 90 days dry. The calving ease and stillbirth data could be related. For example, smaller calves are easier to deliver but may also be weaker and more susceptible to early death. Larger calves would be harder to deliver, causing a stressed calf that is also more likely to die early. Another factor in stillbirth rates for long dry periods is excess body condition, which can increase calving difficulty and the risk of metabolic problems that prolong calving and stress calves. The study also considered whether a heifer survived and generated a first lactation record by 3 years of age. Compared to cows with 51 to 55 days dry, 5 percent fewer heifer calves survived to their first lactation when their dam had a dry period of 0 to 30 days. The authors concluded that a dry period of at least 40, but not more than 65 days would minimize negative impacts on calves.
Cold Stress and Calf Growth
Another USDA research project (Nonnecke et al.) considered the effects of cold stress on calf growth. Twenty-nine calves (3 to 10 days of age) were housed in controlled environments at either cold (35°F) or warm (59°F) temperatures for 7 weeks. In the cold housing both calves and the environment were frequently wetted in an attempt to maximize the impact of the cold temperatures. The humidity in the warm environment was not manipulated. Relative humidity was about 10 percent higher in the cold environment than the warm. Calves were fed one pound of a 20 percent protein, 20 percent fat milk replacer and offered free-choice starter. Cold environment calves experienced greater incidence of respiratory illness than warm environment calves. However, because humidity differed, this cannot be attributed to cold alone. Growth rates were not affected by the housing temperature, but cold environment calves did eat more starter during weeks 5 to 7. Lower blood glucose and higher NEFA levels suggested that cold calves experienced mild negative energy balance. These results indicate that calves can tolerate considerable periods of cold before experiencing enough stress to adversely affect growth. Some of the keys to helping calves survive cold weather are providing fresh, free-choice starter and clean, unfrozen water, keeping them dry, and avoiding exposure to drafts.
Weaning Age and Future Production
Penn State research (Elizondo Salazar et al.) investigated the effect of weaning calves at 3, 4, 5, or 6 weeks of age on first lactation performance. Calves were managed similarly from weaning through their first calving. Age at first calving was not affected by weaning age. Milk, fat, and protein production were the same for all treatments as well. These results should provide reassurance to those who are reluctant to wean calves before 8 weeks of age. Calves can be weaned successfully at 4 to 6 weeks of age without hurting their future performance, and early weaning will cut the costs of feeding calves.
Vaccination Age Matters
Patlola and Smith at the University of Vermont evaluated calves' response to vaccination at 2 or 6 weeks of age. Responses were measured 3 weeks after vaccination. They found that calves vaccinated at 6 weeks of age had a stronger response to the vaccine with more white blood cells and more cells displaying IgG specific to the vaccine compared to calves vaccinated at 2 weeks of age. This is a good reminder that vaccinations must be timed to match when calves are most likely to respond. Early in life calves rely on passive immunity from their dams; their own immune systems are not fully functional and are rarely capable of responding effectively to a challenge, whether it is a real infection or a vaccine.
Coleen Jones, Research Associate, and Jud Heinrichs, Professor
Dairy and Animal Science Extension