Final answer:
One sign that too many horses are kept at a boarding stable is overcrowding, which can manifest as stress, disease, and sanitary issues among the horses, and environmental degradation of the stable grounds.
Step-by-step explanation:
One indication that too many horses are being kept at a boarding stable is the evidence of overcrowding, such as insufficient space for each horse, poor sanitary conditions, or signs of stress and disease in the animals. Overcrowding can lead to increased competition for resources, which may result in inadequate access to food, water, and shelter for some horses. Moreover, cramped conditions can also lead to the rapid spread of disease, as noted in epidemiological studies indicating that high-density animal populations can disrupt host-parasite relationships and facilitate the proliferation of parasites and pathogenic microbes.
Environmental stress factors, like too much manure due to a large number of horses, can lead to the deterioration of the stable grounds, reflecting poor living conditions. This is akin to what William Forster Lloyd described in the 1800s when he observed the overgrazed public commons and the resulting unhealthy livestock. Therefore, stable managers and horse owners must be attentive to any signs of such distress or environmental degradation to avoid the negative effects of overpopulation on equine health and well-being.