It appears that this is a result of a change in the pig_saddle.png format. At some point in the past, it was changed to include the entire pig. Since the older texture displays that same area to be transparent, the game instead renders a black texture.
To fix this on your end, please update your texture/ resourcepacks.
I've found that this bug occurs with the Texture Update Pack from the Marketplace, but does not occur with vanilla Global Resources. AFAIK these textures should be identical, but evidently the change Doubletoad74 mentions above was made at some point.
Never happened to me post 1.16.40. I play on PS4 and it used to happen, until it was fixed with the Nether Update. On what platforms does it still happen?
Not fixed in 1.11.0.7 (I mean effects 1.11.0.7)