Western Meeting of Poultry

 Clinicians and Pathologists 

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Sudden Egg Production Drop in Commercial Layers

W.R. Cox

Canadian Poultry Consultants Ltd.

A sudden drop in egg production was reported in a flock of approximately 9000 65-week-old Hyline hens. Egg numbers dropped from 6042 to 1740 over a period of 5 days. Coincidentally, mortality jumped to 47 birds on the first day of the production drop to 146 on the second day, followed 31,27, and 28 on the following 3 days.

The facility was a typical cage layer operation, with 3 to 4 birds per cage.

Over the 5-day period, water consumption had dropped from 400 to 200 gallons per day and feed consumption was apparently down, but could not be measured.

During this production drop, there was a period of extreme heat, with daytime highs exceeding 30^oC. There was one nipple per 6 to8 birds. There was a serious fly problem in the barn. Many dead birds were still present in the cages, of which 18 were seen on the inlet side of the barn and only 4 on the fan side.

Necropsies were performed on a sample of live and dead birds. The birds had no feed in the intestinal tracts and the gall bladders were enlarged. The livers were fatty in appearance. On the livers there were greenish, focal stellate areas on the serosal surface, thought to be bile staining. The ova in all birds were regressing.

There was a mild, heneralized hepatocellular lipid accumulation and sinusoidal congestion. Milk generalized periportal aggregation of lymphocytes and plasma cells were also seen in the livers.

A presumptive diagnosis of toxicosis and heat stress was made. Given the age of the birds, the flock was shipped rather than trying to bring production back up.

The second case occurred shortly after the first, in a 68-week-old Hyline flock of approximately 8500 hens. In this case, production dropped from 70 percent to 24 percent over a 5-day period. There was no increase in mortality in this instance. Feed and water consumption had both dropped significantly. The important connection between this and Case 1 was that just prior to this production drop, the feed from the barn on which Case 1 occurred was dumped into the bin of this barn.

Feed, light, air, and water were all normal in this barn. The weather had moderated, so heat was not a problem. The birds appeared to have paler than normal combs.

After 9 to 10 days after the drop in production, the flock was observed to being a molt.

Necropsy of a sample of birds revealed enlarged livers, with lesions grossly similar to those in Case 1, but not as dramatic. The ova were also regressed.

In this case, there was periportal and periacinar accumulations of mixed inflammatory cells. There were random areas of acute caseation necrosis also seen.

A presumptive diagnosis of feed-associated toxicity was made.

The feed was removed from the bin and the entire feed system and replaced with fresh feed. Samples of the feed from the system and feed from the bin were retained for further testing.

Assays performed on the feed were negative for common mycotoxins (including T2, aflatoxin, ochratoxin, zearalenone, vomitoxin, and fumonisin. The samples were also negative for drugs and chemicals, which were in stock at the feed mill at the time the feed was mixed.

Samples of feed from the feed system and from the bin were fed to 16, 22-week-old layers, just coming into production. Eight birds were fed feed from the system and 8 fed feed from the bin.

The following observations were made:

Egg Numbers

Average daily feed consumption: Bin Feed 92 grams

System Feed 60 grams

Bird weights: Bin Feed 1.3 to 1.5 Kg

System Feed 1.1 to 1.25 Kg

On necropsy, the Bin Feed birds had good body condition with no visible lesions. All were in good bodily condition. The System Feed birds had mild loss of condition with fully regressed ovaries.

Histologically, there was a mild to moderate generalized periportal accumulation of lymphocytes, plasma cells, and occasional heterophils in the System Feed birds. No lesions of significance were present in the Bin Feed birds.

The feeding trial confirmed the diagnosis of feed-related egg production drop, and supported the suspicion of a toxic etiology. The exact agent and source remain a mystery. No similar cases were reported in any other flocks on this or other farms, suggesting that a single batch was the concern. No drugs or chemicals that were present at the feed mill were detected in the suspect feed. A farm bin source of mold and subsequent toxin s also a possibility; the feed which was moved from the first to the second bin also included feed from the system of the first case.

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Last modified: 5/28/2009