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Calf & Heifer Adviser Articles
Get a handle on heifer mastitis
Although it would be great if all first lactation heifers entered the milking string infection free, it cannot be assumed that this will ever be the case, says Neil Broadwater, University of Minnesota extension dairy educator.
Heifers can become susceptible to mastitis pathogens as soon as they begin to produce mammary secretions, as early as 6 to 8 months of age. Intra-mammary infections at any time thereafter can persist throughout pregnancy and into lactation.
First-lactation heifers represent the future milking herd, Broadwater notes. “Find out what is causing mastitis infections to show up within days of freshening. Then develop an action plan to reduce the level of somatic cell count (SCC) in future first-lactation heifers.”
Lower SCCs in first-lactation heifers could be a partial answer to a lower SCC for the whole herd.
He offers some reasonable SCC goals for first-lactation animals:
- Uninfected heifers should have a SCC of less than 75,000 per milliliter by one week after calving.
- The number of clinical mastitis flare-ups in fresh heifers within the first two weeks of lactation should be less than 10 percent per year.
Read more information on sources of mastitis infection and solutions
Source: University of Minnesota
A look at medicated milk replacer
New regulations for the use of medicated milk replacers containing neomycin sulfate (NEO) and oxytetracycline (OXY) have resulted in a need to explore the effects of amount and duration of antibiotic feeding on calf growth and health. “Previous work by our group showed removal of antibiotics from milk replacer at 14 days reduced growth compared with feeding antibiotics through 42 days,” says Noah Litherland, extension dairy scientist at the University of Minnesota.
In this study, researchers evaluated growth and health of calves fed milk replacer containing varying amounts of antibiotics for 0, 14, 28, or 42 days. Holstein heifer calves were assigned randomly to one of four milk replacer programs. All calves were fed 20 percent crude protein, 20 percent fat milk replacer at 1.3 pounds per day (as-fed powder weight) from day one to day 35 and 0.6 pounds per day from day 36 to day 42.
Four different antibiotic amounts and durations were included in the above milk replacer to yield four treatments; TRT 1 – 400 grams NEO/200 grams OXY per ton of milk replacer on day one to day 42; TRT 2 - 0 grams NEO/0 grams OXY per ton of milk replacer on day one to day 42; TRT 3 - 1600 grams NEO /1600 grams OXY per ton of milk replacer on day one to day 14; TRT 4 - 1600 grams NEO/1600 grams OXY per ton of milk replacer on day 1 to day 14 and day 16 to day 28.
Calves were fed milk replacer twice daily from day one to day 35, and once daily from day 36 to day 42. An 18 percent crude protein (as-fed) texturized calf starter was offered free-choice, along with water, throughout the study. Calves were housed in individual pens within a naturally ventilated barn.
Average daily gain and total body weight gain was lower for TRT 2 when compared with TRT 1 and TRT 4. Total starter intake and total dry matter intake was lower for TRT 2 compared with TRT 1 and TRT 4 through 42 days of age. Dry matter required for gain was higher for TRT 2 compared with all other treatments. TRT 3 increased average daily gain for days one through 14, but upon removal growth was similar to TRT 2.
Fecal scores were not different and averaged 1.3 across treatments. Severe scouring days (fecal score of four) were significantly higher for TRT 2 compared with TRT 4 through day 42. Calves fed increasing amounts and duration of NEO and OXY grew more efficiently, ate more starter, and had fewer days scouring than calves fed no antibiotics.
The future of antibiotic use in calf milk replacer is unclear. Non-medicated milk replacer additives that promote growth and health should be explored, notes Litherland. This research was presented at the American Dairy Science Association meeting this past July in Denver, Colo.
Brix refractometry and colostrum quality
Acquisition of high-quality colostrum is an important factor influencing neonatal calf health. Many methods have been used to assess the IgG concentration of colostrum; however, improved, validated evaluation tools are needed.
New research published in the August Journal of Dairy Science evaluated both optical and digital Brix refractometer instruments for the measurement of IgG concentration of colostrum as compared with the gold standard radial immunodiffusion assay laboratory assessment and to determine the correlation between IgG measurements taken from fresh and frozen colostrum samples for both Brix refractometer instruments.
This research was completed using 288 colostrum samples from three different farms. Researchers concluded that the optical and digital Brix refractometers were highly correlated for both fresh and frozen samples. Correlation between both refractometer instruments for fresh and frozen samples and the gold standard radial immunodiffusion assay were determined to be very similar, with a correlation coefficient between 0.71 and 0.74. Both instruments exhibited excellent test characteristics, indicating an appropriate cut-off point of 22 percent Brix score for the identification of good quality colostrum.
Source: Journal of Dairy Science
Fight the effects of dystocia
The immediate survival of a calf experiencing a dystocia birth is critical, but the effects of dystocia can put the calf at a higher risk of death or illness in the first four months of life. The USDA NAHMS Dairy 2007 report says that calves experiencing a dystocia have a higher risk of being stillborn. In dairy cattle, stillborn is usually defined as death at or within 24 to 48 hours of delivery. 2002 data from Meyer et al. showed the reported stillbirth rate for dairy calves based on 666,341 calving records was 7%, and a 2007 study by Lombard et al. of three Colorado dairies reported a stillbirth rate of 8.2%.
What dystocia does
Calves experiencing a prolonged dystocia are likely to have low levels of oxygen in their blood (hypoxia), and their blood pH is frequently acidic (acidosis) instead of neutral. These impairments lead to a cascade of events, such as decreased ability to nurse, decreased absorption of IgG, and poor temperature regulation.
Calf problems associated with dystocia are most profound in the time immediately after birth. Dystocia is the major cause of stillbirth and approximately half of the calf losses from birth to weaning occur in the first day of life. Read the full story from Bovine Veterinarian.
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