Bull brown semen

Brown semen from a bull

Looking for advice on a case(s) I was presented with this week.

First Case: On Tuesday I was referred by a DVM (also original owner of bull) a yearling bull that passed a satisfactory BSE in January (for sale) and then was recollected by the buyers DVM 2 weeks ago and the DVM noticed “blood in the ejaculate and told the buyer to take it back to the seller (DVM) and of course without any information of the BSE. The seller sent it my direction for a second evaluation. Everything physically with the bull was adequate. The ejaculate was brown in color (see attached images). Testicles and all accessory sex glands were ultrasounded with normal findings. Any idea what this would be caused by? I have seen frank blood in ejaculates but nothing like this. I assume this is just metabolized blood (hemoglobin) giving me this color since on the motility I was not seeing any small cells resembling RBCs. I also assume that this is coming from an accessory sex gland (even though palpation and ultrasound did not reveal any changes)and not the urinary tract since sperm cells were 80% progressively motile (see video attached) with 84% normal morphology, and not dead from urine contaminants. Also, is anyone else seeing ejaculates like this? I ask because the following day, I was doing 8 bulls from a different farm unrelated to the previous bull and one of the bulls gave me identical sample with similar exam findings. Interestingly enough this second bull would give me what looked like a normal ejaculate (white) and then would discharge brown colored fluid. We repeated both bulls with same results.

Any suggestions on how to figure out where the brown ejaculate comes from? Which tests? Chemistry profile (and is there a good reference of what is normal)?

Nutritionally, the first bull is getting fed a TMR with silage/hay and corn, other is on grass for the past 3 weeks. Is there a potential of a toxin or nutritional component?

My thoughts: coming from accessory sex gland (seminal vesicles) since we see yellow/orange tinge coloring from yearlings and others that concentrate riboflavin-niacin complex, early onset vesiculitis (even though no WBCs noted on microscopic evaluation)?.

I put both bulls on meloxicam (for possible unknown inflammation) for now and told owners I would investigate my lack of knowledge. 

Any insight or help would be much appreciated. Been racking my brain to try and figure this out since I saw 2 in less than 24 hours and have no good explanation.

Thanks in advance,