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Keywords

Beef cattle, nutrition, phosphorus supplementation

Abstract

Phosphorus is an important component of bodily functions and is critical for adequate growth and development. This experiment evaluated the effect of maternal phosphorus intake on the growth and health of the calves. Treatments were 1) a free-choice mineral containing no supplemental P or 2) a free-choice mineral with 4% supplemental phosphorus. Primiparous, or pregnant for the first time, crossbred Angus beef cows (n = 36) were stratified by body weight and pregnancy status (bred by artificial insemination or natural service) then assigned to pasture groups (4 groups, 2/treatment, 9 heifers/group). These bred heifers had been receiving these same dietary treatments from 30 days after weaning until confirmation of pregnancy. Eighteen bred heifers from each treatment were selected randomly to continue into this experiment. At calving, colostrum and blood samples were collected from a subset of 12 heifers/treatment (6/group). Body weights were obtained for all cattle. Data were analyzed using the MIXED procedure of SAS. Cows grazed mixed grass pastures; monthly forage samples ranged from 0.28% to 0.36% P. There were no differences (P > 0.10) for cow body weight during gestation, calf birth weight, or calf weight at an average age of 21 days. There were also no differences (P > 0.10) in colostrum components (fat, protein, lactose, and IgG) or in the serum IgG or plasma mineral concentrations for both cows and calves 48 hours after birth. All calves were sampled at approximately 21 days of age, and there were no treatment differences (P > 0.10) in serum IgG concentrations. There were no benefits to supplementing gestating heifers with phosphorus when they grazed pasture with a history of fertilization with livestock manure.

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