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Growth and Estrous Activity of Rats Fed Adequate and Deficient Levels of Phosphorus^{1, 2,}

Department of Animal Science, Texas A. & M. University and Texas Agricultural Experiment Station, College Station, TX 77840

Female Sprague-Dawley rats were fed two levels of phosphorus ad libitum and in a paired feeding arrangement to yield the following three treatments: 1) adequate phosphorus (0.40%) ad libitum intake, 2) low phosphorus (0.04%) ad libitum intake and 3) adequate phosphorus pair-fed with the low phosphorus group. Feed intake, growth rate and feed conversion in rats fed 0.04% phosphorus ad libitum and in pair-fed control rats were lower (P < 0.01) than in rats fed 0.40% phosphorus ad libitum. Seventy-five percent of the rats exhibited normal estrous cycles, as indicated by vaginal smears, throughout the 105-d period regardless of dietary phosphorus level. Breeding efficiency and number of pups per litter were not altered by dietary treatment. However, compared to either phosphorus-adequate group, dams fed 0.04% phosphorus weaned fewer (P < 0.05) pups and pup survival to 45 d of age was lower (P < 0.05). Average daily gain postweaning was 67% lower for pups in the phosphorus-deficient group than for those in either phosphorus-adequate group. Phosphorus deficiency in rats does not alter estrous cycles but reduces pup survivability postnatally.

KEY WORDS: • phosphorus deficiency • estrous cycle • phosphorus balance • feed utilization

¹ Journal paper TA 19912. Texas Agricultural Experiment Station.

² Supported in part by a grant from Houston Livestock Show and Rodeo.

Manuscript received 21 September 1984. Revision accepted 19 February 1985.