Aspects of geophagia amongst dairy cattle in a feedlot system

[摘要] English: Modern confinements imposed on animals limit their access to natural resources required for optimal nutrition. This lack of resources may lead to nutrient deficiencies and one of the hypotheses for the deliberate consumption of soil is to supplement mineral deficiencies. Counteraction of acidosis, detoxification, buffering of unpalatable plant compounds as well as the use of soil as anti-diarrhoeal agent are other suggested motivations for geophagy. By means of direct observation as well as camera traps, the behaviour of geophagy amongst dairy cows in a confined feedlot system was documented. In addition, soil analysis was done to determine the geochemistry of ingested as well as excreted soil. Geophagy amongst cows at Amperplaas constituted less than 2% of daily activity. The non-lactating individuals invested less time in this behaviour than lactating individuals and the frequency as well as time spent on this behaviour decreased as the lactation phases progressed. Recorded geophagy occurrences were most during winter and thereafter spring and peak soil ingestion occurred during mid-day. At Amperplaas, all but one of the mineral licks were situated on the undisturbed elevated areas underneath the fence wire or around the wooden and iron poles. The average size of a typical mineral lick was about 40 cm by 15 cm with a depth of 10 cm. The soil collected from the mineral licks was alkaline and classified as sandy clay loam. Quartz, Plagioclase and K-Feldspar were identified in all samples while Ilmenite was quantifiable in all but one of the control sites. Silica concentrations were supportive of quartz dominance in the soil collected from mineral licks as well as soil from the stomachs and faecal matter. The most recent mineral lick contained the lowest silica, arsenic, copper, lead, scandium, and zirconium content. But this site had elevated calcium, iron, potassium, magnesium, sodium and phosphorus as well as bromine, nickel, strontium and zinc levels. When offered soil combined with different minerals, the preference of most cows was sodium chloride mixture and thereafter calcium-phosphorus. When comparing the estimated amount of soil ingested per second with the excreted amount of soil, it appears that the daily excretion rate of soil is almost equal to the ingestion rate, therefore not posing any threat for sand impaction. Milk collected at Amperplaas had low levels of calcium as well as potassium and therefore, soil is possibly ingested to supplement this deficiency. Results of this study confirm the ability of some animals to detect deficiencies in the body and to attempt to correct these deficiencies from available resources. Results also support the theories that this nutritional wisdom is partly from cultural transmission as well as innate behaviour.

[发布机构] University of the Free State