Fluorine toxicity and laying hen performance

Two hundred eighty-eight Single Comb White Leghorn (SCWL) hens were treated for 252 days with sodium fluoride added to a practical wheat-soybean meal-type basal diet to supply 0, 100, 400, 700, 1,000, and 1,300 ppm fluoride (F). On Day 252, hens fed the two highest levels of F were switched to the control diet and the experiment continued for another 168 days. The two highest levels of fluoride resulted in significant (P less than .05) depression of feed intake, body weight gain, hen-day production, feed efficiency, and egg quality. Fluoride (700 ppm) tended to reduce performance but generally was not significantly different from the control and lower F diets. Long-term feeding of high levels of F (NaF) did not result in permanent production impairment. Birds fully recovered during the 168-day recovery period. In the second experiment 288 SCWL pullets were treated for 49 days with seven dietary regimens: 0 ppm F fed ad libitum (1), 1,300 ppm F fed ad libitum (2), 0 ppm F control pair-fed to 1,300 ppm F (5), an NaCl diet formulated to supply as much Cl- as F- in diet 3 (4), an NaCl diet formulated to supply as much Na as supplied by NaF in Diet 3, (5), 1,300 ppm F plus 1,040 ppm Al diet fed ad libitum (6), and the same diet pair-fed to the 1,300 ppm F diet (7). All groups were fed the control diet for a 7-day recovery period at the end of the experiment. High F intake significantly (P less than .01) decreased feed intake, hen-day production, feed efficiency, and shell quality. However, these depressions were not as severe when Al was present in the diet. The depression in performance due to F feeding was not simply due to the depressed feed intake but rather was a result of a metabolic function of F. Pair feeding the control and F/Al diets resulted in much smaller depression. Egg shell quality was more responsive to the addition of Na to the diet than the F. Although feed consumption recovered within the 7-day recovery period, this time was inadequate for complete recovery in egg production.