I saved your two photos to my computer to check resolution. The day pic is only 173kb and the nighttime is 123kb compared to the 2 pics I posted at 923kb at night and 1.9 MB during the daytime. Higher resolution can make a difference. The IR illuminator can also be part of the grainy look. Not as strong as it could be because is hitting the cedar limb to the left. Might try trimming that limb out of the way completely and then move the camera up a bit higher. Then angle it downward a bit so it does not have to illuminate such far distance. Try to center it on the larger pig that after the sow with the little pigs behind her.
I'll definitely cut the limb tomorrow. The original file on my computer it 4.14MB for the night pic and 6.73 for the day pic. I think the THF cuts them down to save space, but the camera is definitely taking lower resolution pics at night. I think that anti-blur setting may be the biggest issue though after looking at the manual again.