Effect of an Improved Grazing Management System on Dairy Heifer Performance
Applied Research
Amanda Grev
Forage Extension Specialist
University of Maryland Extension
Keedysville
Abstract
The objectives of this study are to investigate the effects of improved grazing management on pregnant dairy heifer performance, along with its economic feasibility relative to a conventional management system. Holstein heifers at the University of Maryland Dairy were utilized for this study on a rolling basis, with heifers added following pregnancy confirmation and removed three weeks prior to calving. Heifers (n=166; 2021-2023) were blocked by due date and randomly assigned to one of two treatment groups which varied in size throughout the study period (15 to 22 per group) but were kept consistent between treatments. Heifers in the control (CON) group received a daily TMR and had access to one continuously managed 5-acre perennial pasture. Heifers in the grazing (ROT) group were rotationally grazed across 19 acres of both perennial and annual pastures subdivided into approximately 0.5-acre paddocks (1-2 d rotation); ROT heifers also received a daily corn/mineral mix (1 lb/head/d) to ensure dietary requirements were met. Both groups of heifers were measured [BW, BCS, hip height (HH)] and fecal samples were collected on a bi-weekly basis throughout the grazing season (April-December). Average daily gain (ADG) was calculated by linear regression and data were analyzed using a mixed model analysis with statistical significance set at P ≤ 0.05. Results are presented for the 2021 grazing season. Initial BW (1122 lb), BCS (3.7), and HH (145 cm) did not differ between ROT and CON heifers (P > 0.05). Final BW and HH did not differ, but final BCS was greater for CON heifers (3.7) compared to ROT heifers (3.5; P ≤ 0.05). For both groups, heifer ADG varied considerably across weigh periods, but ADG was greater for CON compared to ROT (1.66 vs. 1.38 lb/d; P ≤ 0.05). Fecal egg counts were very low for both groups but were lower for ROT heifers compared to CON heifers (9 vs. 16 eggs per gram; P < 0.01). Results indicate a slight growth disadvantage for heifers in the ROT system; however, heifer performance was still good and expenses for this system may be reduced compared to a conventionally managed system.
Poster has NOT been presented at any previous NACAA AM/PIC
This poster is being submitted for judging. It will be displayed at the AM/PIC if not selected as a State winner. The abstract will be published in the proceedings.
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Authors: Amanda Grev, Sarah Potts, Jeff Semler
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Grev, A. Forage Extension Specialist, University of Maryland Extension, Maryland, 21756
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Potts, S. Beef and Dairy Extension Specialist, University of Maryland Extension, Maryland, 21756
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Semler, J. Extension Agent, University of Maryland Extension, Maryland, 21713