Discussion of findings from a PhD Thesis by Nicole Cuthbert Schilling,
Universidad Mayor Veterinary Sciences, Santiago, Chile, 2010

Essential oil based feed additives are used in commercial livestock agriculture as proven effective methods to promote animal health. Scientific research and development combined with the strategic application of essential oil additives in the feed industry create highly efficient animal production systems. To date, most research has been conducted in pigs, chickens and aquaculture; however it has been proved that bovine animals are also able to benefit from the antibacterial, anti-parasitic and gut modifying properties of essential oils. These essential oil compounds indeed have a complimentary effect on the fermentative and digestion processes of multi-stomached ruminant animals for increased optimisation of animal performance.

Essential oils & ruminant nutrition

In-vitro and in-vivo experiments on oregano based dairy feed supplements have demonstrated that methane emissions in mature dairy cows were reduced by 40%. Milk production was improved by the use of oregano based feed supplements (Hristov A, 2010). Energy losses from cattle have been estimated to range from 2-12% of total feed intake (Johnson & Johnson 1995). A reduction in methane emmisions results in a reduced loss of carbon and consequently more efficient utilisation of nutritional energy sources from lignocellulosic based dairy grasses and feeds. Hristov’s study measured the composition of intestinal gaseous emmissions and the results suggest that oregano based feed supplements modified bacterial populations for improved digestion of feed. Protozoa also constitute between 40-50% of the total microbial biomass in the rumen. The symbiotic interaction of ciliate protozoa and methanogenic bacteria affects the ability to convert dietary and microbial proteins, nitrogen and energy utilisation. The efficiency of biosynthetic transfer of nitrogen from feed into the milk has been determined at 25% with the remainding majority lost in the faeces and urine. Researchers are now active into a full assessment of the usage of essential oil based feed additives to remediate the health of the intestine, promote growth & development and stabilise microbial populations in ruminant animals.

Coccidiosis in dairy calves

Coccidiosis is one of the contributing factors to diarrhoea causing diseases in dairy calves. The enterocyctes of the intestinal lining become infected from a range of intracelllular protozoan parasite species. Coccidiosis reduces feed adsorption, increases prevalence of secondary bacterial infections and causes either subclinical or full onset diarrhoea. Faecal shedding of coccidial oocysts is usually accompanied by diarrhoea episodes, and during this stage infection is able to spread to other animals via the faecal oral route of infection.

The trial

Experiments were conducted on two separate farms in the central metropolitan region of Chile and calves were born between March and June 2010. Twenty dairy calves on each farm were analysed with both control and experimental groups of 10 calves at each site. Laboratory examinations analysed coccidian counts using Sheather’s solution and microscopy. Farm measurements of weight gain in individual calves were taken.

Each farm used divisioned pens for the raising of calves away from the main herd, however one farm had wooden slatted floor and overhead infra-red heating whilst the other had a concrete floor and metal fences without supplementary heating. Calves were fed with 4 litres of milk per day or supplementary milk with starter feed. In the experimental group Orego-Stim liquid was included into milk at an inclusion level of 4ml per calf per day for a two month period. All results were analysed statistically.

Results

Dairy calves which consumed Orego-Stim had lower probabilities of faecal coccidia oocysts compared to the control. Figure 1 shows the distribution of weight gain intervals in dairy calves over the experimental period and the polynomial distribution.

Figure 1. Distribution of weight gain in calves

Combined data from both sites with an analysis of the median gives a better measure of the distribution of central tendencies, by eliminating outlying obscure data points. This approach of data analysis using the median resulted in a 6kg difference between the control and Orego-Stim groups, rather than a 3.5kg difference using the mean average. A polynomial distribution of weight gain in both the experimental and control groups shows the difference in distribution patterns over all of the calves analysed. The shape of the curve demonstrates that there is improved uniformity of weight gain in the Orego-Stim group with an increased peak distribution of weight gain at approximately 10kg above the control group

Figure 2 shows the average daily weight gain (mean) of each group. The difference between the median weight gain intervals of the Orego-Stim and control group was 24kg and 18kg respectively.

Figure 2. Average (Mean) daily weight gain (g)

Discussion

This trial was evaluated by statistical software, however unfortunately differences between farms, equipment, farm management procedures, breeds, calf weights at birth and a relatively low sample size was not conducive to the most optimal experimental evaluation.

The first few months of life of dairy calves is noted for being the most vulnerable with diarrhoea being a possible predisposing event prior to mortality. The particular unusually cold weather conditions of the austral autumn and winter in 2010, coupled with infrastructural deficiencies on one of the farms, led to unusually high mortality from pneumonia and respiratory infection within the herd. Sub-clinical coccidiosis of dairy calves can be classified as less than 5000 oocysts per ml of faeces. This study confirms that the majority of calves had oocyst counts within this range, and that Orego-Stim reduced the oocyst counts significantly (p<0.05).

Measurements of calf weight were taken by suspending the calves under scales by a weighing belt. This method of weighing was only accurate to the nearest few kilograms. Therefore, the data from both sites was combined and the median was analysed, as shown in Figure 2. This approach of data analysis using the median resulted in improved uniformity of weight gain in the Orego-Stim group with an increased peak distribution of weight gain at approximately 10kg above the control group.

From the perspective of farm management, this uniformity of increased weight gain is a desirable characteristic required from farmers because calves can be serviced at shorter and pre-determined intervals following their weaning period.

Conclusions

This study has revealed the benefits of using Orego-Stim in dairy calves during the first two months of their lives.

 1)      Improved uniformity of weight gain approximately 10kg above the control group.

2)      Orego-Stim reduced the oocyst counts significantly (p<0.05).

 Similar research carried out by Meriden Animal Health in Colombia confirms that Orego-Stim actually reduces the 1^st heat to service interval period by a significant margin. During this study, it was noticed that four of the calves showed signs of being ready for service five months after the study period. Therefore if a combination of Orego-Stim was used in the mother’s gestation period and followed up with Orego-Stim during the calves diet would give even more superior benefits for productivity.

Orego-Stim improves the function of the gut in mature and breeding animals which leads to better immunity, elevated antibodies in colostrum, improved birth weight and growth of young.

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