NAHMS Data Reveals Calf Health and Survival Trends

A compilation of data collected by the USDA shows that female dairy calves nationwide have a mortality rate of about 5% and morbidity (illness) rate of about 34%. ( Maureen Hanson )

The importance of colostrum delivery and adequate nutrient supply for preweaned dairy calves recently was reinforced by a study conducted by the USDA’s National Animal Health Monitoring System (NAHMS).

The NAHMS Dairy 2014 study surveyed heifer calf management practices and data from 104 different U.S. dairy farms in 13 states. Conducted from March 2014 through September 2015, the data included 2,545 mostly Holstein heifer calves. The resulting information was parsed in a series of articles in the Journal of Dairy Science throughout 2018. Renowned calf and heifer researcher Jim Quigley with Provimi North America summarized the high points of the findings in a recent issue of his Calf Notes publication.

Among Quigley’s observations were:

  • “Stillbirths” were defined as calves that died before 24 hours of age. These animals were not included in the data sets for mortality.
  • Illness in some form occurred at least once in about one-third (33.8%) of heifer calves, with 6% having more than one bout of sickness.
  • Digestive disease (scours) was the primary cause of illness in young dairy heifer calves, with more than half (56%) of all illnesses attributed to the condition.
  • Higher birth weight was associated with lower incidence of illness and death prior to weaning. Based on the data collected, the study’s authors calculated that a 35-kg. (77-pound) birth weight calf had a 40% chance of becoming sick, and 4.7% chance of dying. Comparatively, a calf weighing 45 kg. at birth was predicted to have 31.2% chance of illness, and a 2.3% risk of mortality. The authors noted that calves experiencing in-utero heat stress and/or born prematurely were born smaller and experienced higher levels of illness and death.
  • Colostrum delivery and resultant serum IgG levels had tremendous bearing on health and survival. Calves with 8 g/L serum IgG (indicative of failure of passive transfer of immunity) had a 40.3% chance of becoming ill and 5.2% risk of mortality. Calves with excellent passive immunity, indicated by serum IgG levels of 30 g/L or higher, had just a 29.3% risk of illness and 2.0% risk of death.
  • More nutrients impacted calf health and survival, to a point. Calf mortality was significantly higher in calves fed ≤0.15 kg/day of fat in the liquid diet. However, survival rates did not vary significantly between calves fed moderate (0.16-0.21 kg/day) and high (≥0.22 kg/day) levels of fat in the liquid diet. Quigley summarized that the greatest risk to health and survival is when too little energy is available to support maintenance, immunity and weight gain.
  • Ambient temperature had related bearing on disease risk. At a temperature-humidity index (THI) of 20 -- which is below a preweaned calf’s thermoneutral zone – calves were at 39.5% risk of becoming ill. Calves at a THI of 70 had a predicted illness risk of 29.1%. “This is consistent with the idea that calves are more susceptible to disease when their nutrient needs (especially energy) are not being met completely,” said Quigley. “It reinforces the need to ensure that calves are being fed sufficient calories in cold weather.”
  • Ventilation also had significant impact on illness rates. The researchers found that calves raised in mechanically ventilated facilities were 2.218 times more likely to become sick compared to calves raised in naturally ventilated systems, including hutches.

Among all of the findings, Quigley most emphatically emphasized the importance of effective colostrum delivery. “For most producers, establishing and implementing the correct procedures to feed sufficient amounts of clean colostrum at an early age will pay dividends both in terms of improved health and survival, but also future milk production,” he said. “It’s a good New Year’s resolution to develop or review your colostrum program. Your calves will thank you!”