Date of Graduation

5-2020

Document Type

Thesis

Degree Name

Bachelor of Science in Agricultural, Food and Life Sciences

Degree Level

Undergraduate

Department

Animal Science

Advisor/Mentor

Kegley, Elizabeth

Committee Member/Reader

Powell, Jeremy G.

Committee Member/Second Reader

Rorie, Rick

Abstract

This study aims to examine the effects of phosphorus intake on beef heifer growth performance and conception rates. In Northwest Arkansas, there has been an increase in phosphorus concentrations in soil where livestock manures have been repeatedly applied. Consequently, forages grown on soils high in phosphorus tend to contain high amounts of the mineral itself. This has led many to question whether it is necessary to supplement phosphorus in areas where concentrations may be higher. In this study, crossbred Angus heifers (n = 72), approximately 30 days after weaning, were stratified by body weight (average initial weight 251 ± 3.9 kg) and allocated randomly into 8 groups. Groups were assigned randomly to 1 of 2 treatments. Treatments were delivered through either 1) a free-choice-mineral mix that contained no supplemental phosphorus (CON), or 2) a free-choice-mineral mix with 4% supplemental phosphorus and identical concentrations of other supplemental minerals (4PMIN). Heifers grazed 2.42 ha mixed grass pastures with a history of livestock manure application and were supplemented with soy hulls (0.5% of body weight) daily. Data were analyzed using the mixed procedures of SAS with group as the experimental unit. Total mineral intake through day 112 did not differ (P = 0.55) between treatments. On days 84 and 112, any heifers > 273 kg body weight (n = 58) had an ultrasound evaluation of their reproductive tract. Reproductive tract score (1, infantile to 5, corpus luteum present) did not differ (P = 0.65) due to treatment. Body weights were not different (P ≥ 0.59) through day 264, 409 ± 6.0 kg and 412 ± 6.0 kg for CON and 4PMIN, respectively. When grazing pastures with a history of livestock manure application, heifers did not need supplemental phosphorus through breeding season.

Keywords

phosphorus; heifers; conception; reproduction

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