Urolithiasis in growing pullets can be caused by a metabolic disorder related to kidney dysfunction and during the early laying period. This problem often is associated with elevated calcium levels in pre-lay feed, along with an associated imbalance of dietary electrolytes (sodium, chlorine and potassium).
Under certain growing systems, pre-lay feed is rich in calcium beyond the immediate needs of pullets. This is done to increase calcium reserves in anticipation to high early egg production. If this calcium-rich feed is fed too early, and there is more sodium and potassium than chloride in feed, then uroliths can form. Urolithiasis can reduce life egg production in affected birds and in some cases increase mortality.
To control urolithiasis in pullets, try the following six tips:
1. Calcium in pre-lay diets
It is best to limit the use of high-calcium pre-lay diets during the final growing period and only after comb development. In practice, feeding pre-lay diets for two weeks before the onset of egg production has been shown to be effective in preventing urolithiasis. In addition, it often is recommended to avoid using coarse calcium carbonate in pre-layer diets to prevent pullets picking them up in preference, which increases their total calcium intake.
2. Electrolyte balance
The correct electrolyte balance should be maintained throughout the pullet growing and laying period, which may include adding specific salts. The contribution of dietary electrolytes should be taken into account, as well as sodium levels in drinking water. It's been shows that some birds given saline water are more prone to urolithiasis.
3. Urine pH
Alkaline urine is a predisposing factor of urolithiasis. Adding ammonium chloride in pre-lay and early layer diets can potentially decrease urolithiasis, but this compound is negatively impacting eggshell quality. As a result, other means of urine acidification, which do not cause metabolic acidosis, are required. These often are products based on phosphorus.
4. Dietary protein
High crude protein levels increase plasma uric acid, and in association with elevated dietary sodium and potassium may lead to uroliths, which can be formed from calcium, urate and sodium. Keeping crude protein levels to a minimum standard is recommended to control urolithiasis. Dietary protein specifications should not be reduced by more than 2-4 percent and only after consultation with an experienced nutritionist to avoid any reduction in egg production.
5. Water intake
Uroliths often are formed when birds have limited access to water (supply shortage), or when birds are moved and exposed to a novel water drinking system. Assuring birds have free access to non-saline water from a properly maintained and functioning water system should be a priority at any farm, but it also is a management goal against urolithiasis.
6. Nephrotoxic compounds
Certain antibiotics, disinfectants, pesticides, vitamins and minerals can cause kidney damage in pullets when used outside recommended levels. In these cases, it is most likely due to human error during feed manufacturing. In addition, certain mycotoxins also can cause severe kidney damage and increase the chances of urolithiasis.
