Materials and methods .1 Experimental design

UOP W 0.75

Chapter 1 Introduction

3.2 Materials and methods .1 Experimental design

The experimental unit was a yearling bull and the two treatments were the different breeds, Friesland and Hereford. Replication was limited to eight animals per treatment due to practical and financial constraints.

Eight Hereford and five Friesland bulls were obtained from Cedara. Four Friesland steers (bulls were not available) were bought from a commercial herd, an extra steer was purchased to make allowance for disease.

All the bulls had previously been on kikuyu pasture but were fed silage and hay during the winter months.

The experimental design was that eight bulls per breed would graze the same kikuyu pasture for a period of six months while growth parameters were measured. Some animals were removed from the pasture during the trial period but were still fed kikuyu ad libitum, for the feed intake investigation (26 November to 23 December 1996) and the digestibility investigation (17 February to 28 February 1997).

3.2.2 Experimental measures

Weight, height and condition score measurements were taken throughout the trial period. Animals were weighed every Thursday at the same time (8h30) to minimize the effects of gut fill on animal weight. The animals were not weighed during the feed intake and the digestibility investigations.

The height of the animals was measured four times during the season. Measurements were taken with an apparatus consisting of a sliding horizontal bar fitted to a calibrated vertical bar. The horizontal bar was rested on the animal's withers and the height was read off the vertical bar. The variability of height measurements was increased by the unevenness of the animal handling facility floor and the movement of the animal.

Condition score assessments were carried out five times during the trial according to Mulvaney's dairy scale (Mulvaney, 1977). The condition score assessments were performed by two or more people because of the subjective nature of the assessment.

3.2.3 Animal health

All necessary inoculations for common diseases in KwaZulu-Natal had been done prior to the trial. Dipping

for external parasites was carried outfour times during the season (21 December 1996, 11 February 1997, 13 March 1997 and 21 April 1997). Animals were dosed for internal parasites four times during the trial (25 October 1996, 12 November 1996,30 January 1997 and 20 March 1997). The first three doses were done with Valbazen (Albendazole 7.5 %m/v) and the fourth with Levisol (Leavamisole Hydrochloride 2.5 %m/v).

Three steers (numbers FS1, FS2, FS4) contracted Red Water (Babesia bigemena) and were treated with Veriben and Engemycin on the 22 December 1996. Steer FS4 died on the 10 January 1997 from stress after having fallen into a hole.

During the months of January and February 1997 the steers (FS1, FS2 and FS3) showed low weight gains and looked unthrifty. The veterinarian examined them (1 March 1997) and diagnosed pUlmonary disorders;

blood tests indicated that the steers also had Gallsickness and were treated accordingly.

3.2.4 Pasture management

A calcium lick was made available to the animals on the pasture for reasons discussed in Section 2.4.3.

A pasture rotation system was used to provide sufficient high quality kikuyu so as not to restrict dry matter intake. Five camps of 0.5 ha each were used to give a stocking rate of 6.4 animals/ha; this was, however, subject to change so as to fit in with the grazing management of Cedara. Based on visual observation of the pasture, when the sward appeared on average to be below 10 cm, the animals were moved to a new camp.

Animals usually spent about 7 days in each camp.

Pastures were fertilized with 250 kg nitrogen/ha/season. This was given as five 50 kg top-dressings during the kikuyu's growing season. The first dressing was given as ammonium sulphur nitrate (ASN) to maintain the kikuyu pasture's sulphur requirements while the remaining top-dressings were given in the form of limestone ammonium nitrate (LAN). Potassium and phosphate were applied according to requirement as determined by soil analyses (as recommended in Section 2.2.3).

All the pastures were dry-land and relied on rainfall for moisture. Rainfall and evaporation data for the trial period are shown in Figure 3.1.

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Figure 3.1: A comparison of monthly rainfall (mm) and evaporation (mm) during the trial period with the long-term running averages (Institute for Soil, Climate and Water, 1997).

The trial period (October 1996 to April 1997) was a moist season with a total rainfall of 809 mm as compared with the 80 year average of 744 mm. The distribution of rainfall, as shown in Figure 3.1, indicates that the rainfall during the months of January, February and April 1997 were significantly different to the monthly 80 year mean rainfall. January and April were wet months with an additional rainfall of 85 and 80 mm, respectively, being recorded. The additional rainfall that fell during the month of April was more than double the 80 year mean. February 1997 was a dry month in that the rainfall recorded was only half that of the 80 year mean rainfall.

The evaporation during the trial, as shown in Figure 3.1, was considerably lower than the 35 year mean (790 vs 1078 mm, respectively). The higher total rainfall and the lower total evaporation implies that more moisture, relative to the long term running average, was available for plant growth during the season. The increased rainfall could have had a negative influence on plant growth, since more nutrients were potentially leached from the soil, or the rainfall possibly contributed to a decrease in sunshine hours.

Temperature data for the trial period is shown in Figure 3.2.

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Figure 3.2: A comparison of monthly maximum and minimum temperatures rC) during the trial period with the long-term running averages (Institute for Soil, Climate and Water, 1997).

The monthly maximum and minimum temperatures recorded during the trial period, as shown in Figure 3.2, were similar to the 80 year average values. Temperature-wise, the trial period was thus an average season.

3.2.5 Statistical methods

The Genstat 5 (Release 3.1) statistical program (Lawes Agricultural Trust, Rothamsted Experimental Station) was used for statistical analyses. Statistical differences between treatment means were determined from analysis of variance tables with the use of the Students t-test at the 5%level. Regression analyses (linear and quadratic), where possible, were also performed.