I can't give you a more exact date unfortunately, but from what I can tell it should be somewhere between 1948 and 1967. The current structure of the bird house is already present, which was completed in 1948. But the jubilee complex, opened in 1968, is not yet present while the old predator house (of which only the lion statues and some columns remain) still is. The fact the bird house is still mentioned as new, and that in the bottom right corner (the bottom side on this map borders on Antwerp Central station) there is an area still mentioned as destroyed in the war makes me think this map is from the earlier portion of that period, so possibly early 1950's.
To make the dating somewhat more precise, I think this map is from somewhere between 1953 and 1957. The hippo house (no. 27), which was severely damaged during the war, only re-opened in 1952, and I believe that the temporary hoofstock enclosures on the site of the bombed antelope house (no. 43) were only constructed around these period too. The caprid enclosures that the map still marks as "damaged during the war" (no. 39-40) were reconstructed in 1957, and the absence of the great ape house, which opened in 1958, is also an clear indication of the timeframe.
@OkapiJohn Manatees (or rather a manatee, as Antwerp never had more than one individual at once) were housed in a small pavilion at the north end of the pig house and pheasant aviaries (numbers 19 and 30 on the map). The green space on the left side of said buildings is where it should be indicated, but it's interesting to see that they apparently forgot to put 20a on the map.
Antwerp did start keeping African manatees in the likely time frame of this image (first individual in 1953 which soon died, second in 1954 that lived until 1970) and later (1970s - 1980s) also kept West Indian manatees.
There used to be a building near the Egyptian temple (number 20), the pig house (number 19) and the lama house (number 18) with a very small and shallow pool for a manatee. Just to the right of where the striped lines split on the map. There is a photo of this building in the gallery, which I have listed below.
I don't know exactly when this building was constructed or how long it existed, but given the 20a I think they are referring to that structure, although 20a isn't actually on the map as far as I could see.
@KevinB The manatee pavilion was constructed at the end of the 1940's with the purpose of housing a West African manatee that arrived in 1948 (and lived until 1952). It was in use for manatees until the early 1980's, but was renovated afterwards into a souvenir shop which existed until the early 2010's.
