Sustainable animal production on pasture planted on rehabilitated mine land will only be possible if
the optimal stocking rate for animal and pasture production is determined. A grazing trial was
conducted on tall fescue, established on rehabilitated mine land and irrigated with mine waste
water. The aims of this study were to quantify: a) animal performance and nutritive value at
different levels of nitrogen (N) fertilization during pasture establishment, and b) intake, animal
performance (defined as average daily gain; ADG) and nutritive value when different stocking rates
were applied. This study was done during two seasons: season one in winter (6 June -16 July
2008) and season two in spring (28 Aug – 6 Nov 2008). In terms of post mining land use this study
supplied valuable information on potential livestock production.
The higher level of N fertilization applied during the winter of 2007 at pasture establishment
resulted in a significantly (P < 0.05) higher crude protein (CP) concentration a year later compared
to the lower levels of N fertilization. During the winter grazing season the pasture contained an
average of 83.4 g CP kg-1 dry matter (DM), 601.9 g NDF kg-1 DM, 6.2 g Ca kg-1 DM and 1.7 g P kg-1
DM, the average in vitro organic matter digestibility (IVOMD) was 642.2 g kg-1 OM and the average
leaf: stem ratio was 88:12. The ADG of crossbred weaner calves grazing the low N fertilization
(LN), low stocking rate (LS) paddock (229.1 g day-1) was significantly (P < 0.05) lower than the
ADG of weaner calves grazing the LN, high stocking rate (HS) and the high N (HN), LS
respectively. The ADG of the animals in the HN, LS paddock was 482.7 g day-1 and in the LN, HS
paddock was 310.6 g day-1. The low ADG for the LS treatment was due to the low CP
concentration of this paddock, with values as low as 55.1 g CP kg-1 DM recorded during the winter
grazing period. Low pasture nutritive value during winter can potentially limit animal production.spring grazing season the pasture contained an average of 101.0 g CP kg-1 DM, 639.1
g NDF kg-1 DM, 8.9 g Ca kg-1 DM and 2.1 g P kg-1 DM. The average leaf: stem ratio was 85:15,
IVOMD was 717.5 g kg-1 OM and effective DM degradability (in situ) was 56.1 %. The average OM
digestibility estimated with the alkane method varied between 720.8 to 768.3 g kg-1 depending on
the alkane used and weather a correction was made for the faecal recovery of the alkane used. On
average the forage available in the paddock with the LS had a significantly (P < 0.05) higher CP
concentration, leaf: stem ratio and IVOMD, with a significantly (P < 0.05) lower NDF concentration
than the HS paddock. This is probably due to the fact that in the HS paddock forage with a high
nutritive value was removed at a higher rate. Irrespective of the calculation used, digestibility
calculated by the alkane method did not differ significantly (P > 0.05) between paddocks at any
time period. The average intake in the paddock with medium grazing stocking rate (MS) was
significantly (P < 0.05) higher than the average for the other paddocks. The paddock with the MS was managed to supply a pasture DM allowance of 2.5 % body weight (BW). The DM intake over
the spring season was 2.2 % BW. The MS treatment supplied sufficient plant material without
resulting in large accumulation of plant material. The ADG for the spring season was 110.5 g day-1
and averages for each paddock did not differ significantly (P > 0.05) from each other.
During the / Dissertation (MSc Agric)--University of Pretoria, 2013. / gm2014 / Animal and Wildlife Sciences / unrestricted
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:up/oai:repository.up.ac.za:2263/40338 |
| Date | January 2013 |
| Creators | Janse Van Rensburg, Marjorie |
| Contributors | Van Niekerk, Willem A., marjoriejvr@hotmail.com, Truter, Wayne Frederick |
| Publisher | University of Pretoria |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
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