Results and discussion

UOP W 0.75

Chapter 1 Introduction

3.3 Results and discussion

Oct-96

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• Maximum temperature during trial

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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.

3.3.1 Age of trial animals

The exact birth dates of the Friesland bulls were unknown, however, they were all born between the middle of August and the middle of October 1995. The mean ages of the Hereford bulls and Friesland steers are presented in Table 3.1.

Table 3.1: Mean age (days) of Hereford bulls (HB), Friesland bulls (FB) and steers (FS) at the start of the trial (23 October 1996)

Measurement HB FB FS

(n

=

^{8) (n}

=

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³⁾

Initial age (days) 394 404 276

Range (days) 374 to 435 374 to 435 267 to 302

The data presented in Table 3.1 indicates that there is a large age difference (more than 115 days) between the Friesland steers and the Hereford and Friesland bulls. An analysis of variance performed on the Hereford bull and Friesland steer age data indicated that the difference in ages (394 versus 276 days) was highly significant (P < 0.01).

3.3.2 Weight gain

Weekly weights of the breeds during the trial period are shown in Figure 3.3.

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Figure 3.3: Average weight (kg) of Hereford bulls (HB), Friesland bulls (FB) and steers (FS) during the trial.

The Friesland steers were on average 60 kg heavier than the Hereford bulls at the start of the trial. The steers lost about 20 kg in weight during a period of two months from the middle of November to the middle of January due to the illness discussed in Section 3.2.3 and had a similar final average weight to the Hereford bulls at the end of the trial. The growth rate of the steers was affected by their vulnerability to disease. The steers were bought from a commercial herd in the Bisley Valley area and thus had no resistance to the strains of disease organisms at the trial site.

The Friesland steer data was excluded in the growth analysis investigation because of the significant age difference (118 days) and since growth was stunted by the various sicknesses (see Section 3.2.3) the steers contracted.

A summary of the weight performance of the Hereford and Friesland bulls during the trial is presented in Table 3.2.

Table 3.2: Weight performance of Hereford (HB) and Friesland (FB) bulls during the trial

Measurement HB FB CVO/O

(n

=

^{8) (n}

=

⁵⁾

Initial weight (kg) 221 a 292b 16

(±SE) (±15) (±16)

Final weight (kg) 338a 429 b 13

(±SE) (±16) (±24)

Weight gain (kg) 116 137 18

(±SE) (±9) (±9)

Average daily gain (kg/d) 0.61 0.73 18

(±SE) (±0.05) (±0.05)

Initial metabolic weight (kg W 0.75) 57.2a 70.6^b 12

(±SE) (±2.9) (±2.9)

Final metabolic weight (kg W 0.75) 78.6a 94.2b 10

(±SE) (±2.8) (±3.9)

Metabolic weight gain (kg W 0.75) 1.48 1.45 16

(±SE) (±0.1 ) (±0.05)

ADG/metabolic weight (g/kg W 0.75/d) 7.8 7.7 16

(±SE) (±0.54) (±0.25)

a,bValues bearing different superscripts in the same row are significantly different (P<0.05)

The results of the analysis of variance is summarised in Table 3.2 and confirms the trend in Figure 3.3. The Friesland bulls were found to be significantly heavier than the Hereford bulls, both at the start of the trial (by 71 kg) and at the end of the trial (by 91 kg). Even though the Friesland bulls had significantly different initial and final weights to the Hereford bulls, the weight gained during the trial was not significantly different (0.73 kg/day for the Friesland bulls and 0.61 kg/day for the Hereford bulls).

A linear regression model was found to fit the data the best (quadratic regression was inappropriate) and is illustrated in Figure 3.4, but only accounted for 60 %of the variance affecting weight gain. The equation describing weight gain over time (see Figure 3.4) for the Frieslands was:

y = O.6562(±O.0495)x + 293.86(±7.06) and that for the Herefords was:

y = O.6562(±O.0495)x + 214.37(±5.41) where y is weight (kg) and x is time (days).

[3.1]

[3.2]

The slope coefficients of equation [3.1] and [3.2] describing weight gain were the same (0.656) indicating that there was no significant difference in rate of weight gain over time between the breeds even though the y intercepts were different (due to different initial weights, with the Friesland bulls being 71 kg heavier).

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Figure 3.4: Linear regression model (equation [3.1] and [3.2]) of weight (kg) for Hereford (HB) and Friesland (FB) bulls over time (r2=0.6).

3.3.3 Height gain

Average heights of the breeds during the trial period are shown in Figure 3.5.

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