The camera embeds information about the settings that were used for a particular picture in the file. This information is then stripped by some software when exporting after post-processing, or even when posting on the web. You could either work out which of your software did the stripping, and post the image again, or you could just post the data manually from the original photo.
It would also help to know whether you take jpgs or raw images, and if any post-processing has been carried out for this image.
You can add some of the EXIF data by right clicking on your original photo and opening the details tab. This will show you information such as shutter speed, aperture, ISO, and focal length which could be helpful in assessing your photo.
The subject matter in your photo is good, but the photo is a bit grainy so I'm assuming you were using a high ISO. I use a Canon 650D (T4i) and I try to keep my ISO below 800, or up to 1600 if really necessary, but this will not result in a very good photo in dim light. Higher level professional cameras cope better with high ISO levels, but "entry-level" type DSLRs like you and I are using are best at lower ISOs. I also see that you are using a Tamron 70-300 lens, and under the conditions of the photo attached you might not be able to expect great results. These entry-level superzooms are made for flexibility and are not spectacular at long focal lengths, especially in dim light with a maximum aperture of only f/5.6 (which I assume is the case with your lens).
As for getting precise focussing, check your focus point on your camera. If you intend to focus on a single deer or other animal, I would recommend manually choosing your central focus point and placing that on the intended point of focus on the animal. This is generally the eye or head of the subject. Using your central focus point is very helpful in bird photography because the bird is genarally small in the frame and you are aiming for the bird, not it's surroundings. If you have already done this and the attached photo is unedited, your central focus point would have been on the trees and background behind the deer, which would result in poor focus.
I shoot with a Canon 400 f/5.6L lens, with the same max aperture as yours. That being said, it is critical to have good light in order to be able take very sharp photos. AF systems struggle in low light as you push your camera to detect contrast on dim surfaces. In bright light your camera can pick up areas of contrast better resulting in a sharper photo. While the 400 f/5.6 is known for being sharp wide open (that is, at f/5.6) entry-level zooms such as the Tamron 70-300 can benefit from being stopped down to f/6.3-f/8 for sharp results. Of course, this makes things a bit tricky when shooting in low light, and you may have to sacrifice image quality in able to take a properly exposed photo.