All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If those feces are continuous in a way that during the time of the prayer you do not find enough time for ablution and the prayer, to perform the prayer with a valid purity, then your ruling is the same as that of someone who is affected with incontinence.
Hence, you have to perform ablution after the beginning of the time of the prayer, and pray whatever you wish of obligatory and supererogatory prayers until the time of that prayer expires.
But if you find a known time that is enough to perform the prayer with a correct and certain purity, you have to wait until that time comes and you perform Istinjaa’, ablution and prayer.
The Maaliki jurists are not of the view that it is an obligation to perform Istinjaa’ from those excrements in this case, and you can act according to this view if the time of the prayer is very narrow, and you can combine the two prayers that can be combined for a need, such as Thuhr and ‘Asr or Maghrib and ‘Isha. Therefore, if you find it hard to clean (purify) yourself at the time of Thuhr prayer, for example, you can wait until the time of ‘Asr prayer comes and combine the prayers according to the view of many scholars. Then, if you see these feces, you attribute them to the nearest probable time. So, if it is probable that you have these feces either before the prayer or after the prayer, then you attribute it to after the prayer because it is the nearest time.
For more benefit, please refer to Fataawa 25225.
Allah knows best.