Duck acting off, possible obstruction

[Jenbirdee]

You might also want to consider a dewormer. Worms can cause blockage in crop in gizzard and intestines . Like Valbazen or safeguard . I chose Valbazen last time I dealt with a blockage because it kills capillary worms and they can live in the gizzard +

 

[coach723]

Like others, I have chickens rather than ducks. Molasses flush I have used is recommended for toxins:
1 cup molasses mixed in 2 1/2 gallons of drinking water. Give for a maximum of 8 hours and then replace that mixture with electrolite water. If he's not drinking on his own you can give that mixture at intervals, like he would drink during the day.

For impactions I have used epsom salt flush:
1/2 tsp of epsom salt mixed in 1/8 cup water. Give entire amount orally (if via syringe go slow as to not cause aspiration, tubing is faster). Repeat after a few hours if no improvement.

They can be dehydrating, so keeping them hydrated is important.
I would stick with one, if you double up then severe upset or dehydration could result.

Worming is another option. Since he appears to be passing something, it may be better to worm. See if that gives any improvement. For heavy loads of worms I've had it take almost a week in some cases for them to start really looking better. It can vary, some perk up quickly. If they are really poorly, I worm, and give fluids several times a day, if they are going through their systems and not sitting in the crop.

If it is impaction, and in the gizzard, that is hard to treat and hard to know. Trying to get it to pass is pretty much all you can do, it's not reachable for surgery, like it would be if it were in the crop.