Comparison between the international version, taken from the German DVD by Kinowelt and the uncut American DVD Re-Release (R-Rated) by Legend Films / Paramount (=US Blu-ray).
The interntional version has been released on DVD in the USA by Blax Film. It has also been released on DVD in the Netherlands, Poland, Sweden, Spain and several other countries. The uncut and uncensored version has been releaed in some countries too, but most time on VHS (e.g. in Italy, France and Greece).

If you compare the international Version and the American DVD Re-Release you will see that director Richard Fleischer shot several scenes in 2 different versions: one version includes sequences with naked actors and the other version shows the exact same scene with actors wearinc clothes. Additionally the American Re-Release version includes some more nude scenes as well as some more violent content.

Aspect ratio of the American version = 1.78:1
Aspect ratio of the German version = 1.85:1

Runtime of the PAL version (including credits) = 1 hour 57 minutes 50 seconds = 117 min. 50 sec.
(7 cuts, 6 alterations)
Runtime of the NTSC version (including opening and credits) = 2 hours 6 minutes 39 seconds = 126 min. 39 sec.

0:00.00
At the beginning of the US version you see the Paramount logo from the 70's.
12 sec.

0:03.22
During the scene where the slave trader takes a look at the slave with the "R" on his back, the censored version misses out on a dialogue where the slave trader checks for hemorrhoids (NOTE: both the English [uncut] and the Spanish soundtrack include this dialogue). However, you don't see the corresponding scene during this dialogue in the Spanish version. The slave trader asks the slave to pull his pants down and then to bend over. Maxwell comments that this is a waste of time because none of his slaves have hemorrhoids.

0:03.46
In the US version the slave trader checks the slave for hemorrhoids.
19 sec.

0:09.25
When the slave girl gets washed in the trug her breasts are covered in the German version.

0:10.24
In the US version, you do see her breasts.

0:17.01
Hammond puts his clothes off in front of the slave girl who is praying on her bed. In the German version, the camera zooms to Hammond's face and the slave girl covers her private parts.

0:18.02
The US version, however, shows Hammond from the front (he's completely naked) and you can also see the slave girl's private parts.

0:17.32
When the slave is being punished (they hung him on the roof upside down), his butt is covered by a wood lath in the German version.

0:18.55
In the US version you see close-up shots of both the butt and the bloody bat.

0:24.11
Cousin Charles throws the slave girl on the bed.

0:25.59
In the US version you can see her breasts before she lands on the bed.
2 sec.

0:29.30
At the slave market.

0:32.02
In the US version you see some more slaves that are for sale - most of them are topless.
4 sec.

0:30.29
The Swedish widow puts her hand in Mandingo's pocket.

0:32.33
In the US version she at first opens Mandingo's pants and then touches him.
5 sec.

0:39.51
The whore says goodbye to her freer in the bordel. In the German version, the whore is fully dressed.

0:42.26
In the US version you see the whore from the front - she's completely naked.

0:41.10
A whore tries to seduce Hammond. In the German version, the camera zooms to Hammond's and the whore's face.

0:43.44
In the US version you see teh whore touching Hammond's crotch with her left hand.

0:43.10
During the fight between Mede and the bordel's slave the whore on the balcony covers her breasts with a blanket.

0:46.26
In the US version you additionally see her dropping the blanket - her breasts bob up and down.
3 sec.

0:57.23
Hammond lies on the bed next to Ellen and talks to her. In the German version, both of them are fully dressed.

1:00.52
In the US version, the two of them are naked and Hammond touches Ellen's breast.

1:10.30
During the fight between Mede and Topas the German version misses out on a few details:

1:14.36
The US version shows additional close-up shots: Topas bites Mede's thigh. Then you see the bloody bite wound. After that you see Topas scratching Mede's back for a second time - blood runs out of his back. Additionally you see a few close-up shots of Topas' first bite wound at his neck. Just before Mede lunges at Topas' carotid again, someone jumps in between them and separates them for a short moment. In the background you can hear Topas screaming in pain.
25 sec.

1:36.08
Blanche falls on the bed with Mede. The German version then fades to the next scene.

1:42.12
In the US version you can see what Blanche and Mede are doing after falling on the bed.
97 sec.

2:06.27
At the end of the US version you see the Paramount logo from the 70's again.
12 sec.