Masters Theses

Todd M. Steen

Date of Award

12-1990

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

J.D. Quigley III

Committee Members

J.C. Waller, L.W. Vantassell

Abstract

Two experiments were conducted to examine effects of ionophores on body composition in replacement heifers. In experiment 1, 32 Holstein heifers (250 kg initial BW) were assigned randomly to a 2 x 2 factorial arrangement of low undegradable protein in concentrate (L, 30% of CP) vs high undegradable protein (H, 38% of CP) and lasalocid (0 or 200 mg/hd/d). Animals were housed in an open barn in 8 pens of 4 animals and fed 12.7 kg/pen/d of experimental concentrate once daily with medium quality fescue hay for ad libitum consumption. Body measurements were taken every 28 d while ultrasonic fat thickness (F) and muscle depth (M), urea space (US), body fat % (BF), body protein % (BP) and coccidia (C) were measured every 84 d. There were no significant differences (P <.05) in dry matter intake, feed efficiency, weight gain, height, length, hook width, forearm length, US, BF and C; however, heifers fed LO and H200 had decreased body circumference (BC), F, M and BP. Means for LO, L200,, HO and H200 were: BC (cm), 173.3, 174.6, 177.3, 171.6; F (mm), 7.4, 8.5, 8.7, 8.0; M (mm), 54.1, 57.3, 56.3, 53.9; BP, 17.9, 18.1, 18.2, 18.0.

Experiment 2 utilized 20 Holstein heifers assigned randomly to 1 of 2 experimental supplements containing 0 or 200 mg/hd/d lasalocid. Animals were placed on 9.7 ha of permanent fescue divided by portable electric fence and offered 13.6 kg of cracked corn and 5.9 kg of supplement/group/d once daily. Body measurements, F, M, US, BF, BP and C were measured as in experiment 1. There were no significant differences (P <.05) in body measurements, weight gain, F, US, BF, BP; however, heifers fed lasalocid had decreased (P < .05) coccidia and M. Means for 0 and 200 mg/hd/d lasalocid were: C (oocyst/g), 60.8, 36.6; M (mm), 52.5, 49.0. Data from both experiments suggest that lasalocid did not affect rate or composition of body gain in heifers weighing 250 to 430 kg.

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