One of the older strategies for getting the keyword noticed was to use the same word multiple times on a page, the problem with this approach is that it isn’t easy for the reader to follow.

However search engines are more sophisticated now, they recognise related keywords so a post about Older Horses could also use words such as elderly equine, older mare, retired ponies.

Using alternative phrases for your keyword tells the search engines two things;

1 - your topic is definitely about this subject (older horses)

2 - You know the language and alternative phrases so you must be an authority on the topic

In addition alternative phrases allow you to capture a broader search query, so all of the following could be ranked for;

How do I manage my elderly equine?

What do I need to do for my older horse?

How do I look after my elderly pony?

Finally your aim is readability and being recognised as an authority. Therefore you need to convince your readers that you know your subject matter and are familiar with the main phrases associated with this particular niche area.

By writing for the reader you actually increase your authority and SEO value.