OklahomaHorses Magazine September 2020

September/October 2020 • OklahomaHorses 19 But do horses really make foraging choices based on their actual nutrient needs? In a study where horses were given choices between different grass heights that all met protein requirements, the horses selected the grasses which would provide overall greater intake. Essentially, one bite of taller grass resulted in more ingested feed and could allow for faster ingestion of energy. However, if the quality of the vegetation differed, horses began to make rather interesting choices. When protein quality lowered, so that it was only at or below their requirements, horses shifted to foraging choices that would supply their protein requirement but lowered their overall energy intake. As maturity increased in the taller swards, this preference for shorter swards of higher nutrient content, but less overall available forage, increased. It appeared that horses were able to forage selectively to meet specific needs. If we think about this physiologically, it makes sense. Horses can mobilize fat stores to supply energy needs but need to ingest specific amino acids in order to synthesize body proteins. Thus, protein intake may be a higher priority than overall energy intake. Not only do horses make grazing choices according to feed selection, but also to avoid grazing near feces. Horses confined to pastures typically exhibit what is known as latrine behavior, or repeatedly using the same areas for defecation. The vegetation in these areas grows quite tall as the horse refuses to use these areas for foraging. This behavior may confer the advantage of prevention of parasite infestation as most infective worm larvae are found within 1 meter of fecal piles. This combined avoidance of both tall grass and grazing near feces is what creates the roughs, which may represent almost 50% of a pasture. Unfortunately, an owner cannot choose a part of the pasture to create a latrine area. The initial selection of a latrine area does not appear to be due to any difference in vegetative species or palatability; it is simply due to avoidance of grazing near fecal material. In comparison, free ranging horses and ponies simply defecate where they happen to be grazing, then merely continue walking forward. Presumably, this is because there is enough grazing area available to avoid grazing near feces. In the study mentioned above, there was also low animal density, between about 6.5 acres to 19 acres per animal. These animals were also grazing in rather poor nutritive value areas, so their feeding decisions may have had more to do with nutritive decisions or pressures rather than grazing near eliminative areas. Therefore, if you are fortunate enough to have extremely large pastures or ranges, latrine behavior may not be a concern for you. Alternatively, when horses are presented with small paddocks with uniform grass height, they also do not show any specific latrine behavior, but rather defecate throughout the area rather homogenously. This allows a much more uniform distribution of foraging. As we continue to learn more about the foraging patterns and the choices horses make while grazing, we can make better choices for pasture management. To maximize production of our pastures, we need to understand the choices horses make and how we can manipulate those choices to our advantage. LET THE Jim Van Sickle 918.645.1188 YOUR PROPERTY