Phosphorus Intake of Beef Heifers
The effects of phosphorus intake from grazing on beef heifers.
Nashville, Ark. – Howard County is one of the top poultry-producing counties in Arkansas. With all those chickens comes a lot of litter. Litter has historically been applied to meet the nitrogen requirements for forages or crops. However, this approach applied two to four times more phosphorus than was needed by the plant. Repeated application with this approach results in the accumulation of phosphorus in the soil. Phosphorus can be an expensive ingredient in the cost of mineral supplementation of beef cattle. A study was conducted in Northwest Arkansas examining the effects of phosphorus intake from grazing on beef heifer growth performance and conception rates.
For the study, seventy-two crossbred Angus heifers were arranged by body weight and distributed into 8 groups approximately 30 days after weaning. The groups were randomly assigned to either a free-choice-mineral mix with no supplemental phosphorus or a free-choice-mineral mix with 4 percent supplemental phosphorus and identical concentrations of other supplemental minerals for all the animals. The heifers grazed approximately 6-acre mixed grass pastures with a history of livestock and poultry manure application resulting in soil test phosphorus levels of more than 130 parts per million.
The total mineral intake throughout the study did not differ between treatments. On days 84 and 112 after weaning, 58 heifers over 600 pounds had an ultrasound evaluation of their reproductive tract. The reproductive tract score did not differ between the treatments. Body weights at day 264 were not significantly different with 901 pounds plus or minus 13 pounds for animals with no supplemental phosphorus and 908 pounds plus or minus 13 pounds for animals that received 4 percent supplemental phosphorus. Blood samples were taken from heifers to determine pregnancy status. Researchers found final pregnancy rates of 89 percent for the control group and 78 percent for the groups receiving supplemental phosphorus. Results show phosphorus supplementation of developing beef heifers for approximately 300 days following weaning and through the breeding season did not improve growth or reproduction when the heifers were grazing pastures with a history of livestock or poultry litter applied.
Saving money is an important goal for everybody. If you regularly get litter applied to your fields, you may consider bringing in a soil sample to see where you stand on soil nutrients. This may help you cut back on mineral costs.
For more information, call the Howard County Extension Office at 870-845-7517 or view our animal and forage resources.
By Dawson Bailey
County Extension Agent - Agriculture
The Cooperative Extension Service
U of A System Division of Agriculture
Media Contact: Dawson Bailey
County Extension Agent - Agriculture
U of A Division of Agriculture
Cooperative Extension Service
421 N. Main Nashville AR 71852
(870) 845-7517
dbailey@uada.edu
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