Gone are the days of using low-dose antibiotics for growth promotion in livestock. But are there non-antibiotic options that could produce the same effect?
A study recently published in the Journal of Dairy Science highlights the research of a group of animal scientists at Gansu Agricultural University in China. They explored whether adding essential oils to pelleted calf starter would impact the growth, development and health status of Holstein calves in their first weeks of life.
In the study, 40 Holstein calves were divided into two groups. One group was fed a pelleted calf starter containing 44.1 ppm of an essential oil prebiotic containing carvacrol, caryophyllene p-cymete, cineole, terpinine, thymol, arabinogalactans and cobalt lactate. The other (control) group received an identical pelleted starter without the essential oil additive. Colostrum, liquid nutrition and housing were identical across all 40 animals.
Calves were enrolled in the trial starting on Day 3 of life, concluding at Day 70 of life. Weaning occurred at 42 days of age. The researchers found advantages for the group receiving essential oils for virtually every parameter evaluated, including:
- Body weight – By the end of the study, calves in the treatment group weighed an average of 13.59 lb. more than the untreated controls, for an 11% higher body weight.
- Average daily gain (ADG) – The treated group gained 1.92 lb. per day, versus 1.72 lb. for the control group.
- Dry matter intake (DMI) – Calves fed the additive had a DMI of 3.84 lb./day, versus 3.59 lb./day for the control group.
- Feed conversion ratio – Feed conversion ratio was 1.43 lb. of gain/lb. of dry matter for the treated group, compared to 1.37 lb. gain/lb. of dry matter for the control group.
- Frame score – Body frame measurements for withers height, body length, heart girth, abdominal girth and cannon bone length were assessed 6 times throughout the study. By the end of the study on Day 70, all 5 assessments for frame growth were shown to be significantly higher for the treatment group.
- Scours incidence – Assessment of daily fecal scores showed that a score of 4 (mild diarrhea) was 3.5 incidences lower in the treated group versus controls. A fecal score of 5 (severe diarrhea) was 0.5 incidences lower in the treated vs. control calves.
- Blood immunoglobulins – The treated group showed significantly higher concentrations of blood IgG and IgM on Day 14; IgA on Day 28; and total serum protein on Day 42.
- Blood volatile fatty acids (VFAs) – Blood VFA concentrations were greater at the end of the study for the treated group, signaling more advanced rumen development.
- Nutrient digestibility – Total tract digestibility of dry matter, crude protein, acid detergent fiber, starch and several minerals was increased for the treated calves.
The researchers suggested the positive influence of the essential oil additive may be attributed to potential antimicrobial properties. In previous studies, essential oils have been shown to inhibit gram-negative bacteria, gram-positive bacteria, and some parasites.
They recommended further studies to more directly evaluate the impact of essential oils on rumen development, and to experiment with adding them to milk replacer in addition to calf starter.
Still, they concluded that including an essential oil and prebiotic combination to calf starter early in life “can be a plausible alternative to feeding subtherapeutic antibiotics for improving calf health, performance and immunity.”