Results Directory UMM :Data Elmu:jurnal:A:Applied Animal Behaviour Science:Vol69.Issue1.Aug2000:

Table 1 Structure of the ANOVA table used for analysis of data obtained from video tapes. Data were analysed using an ANOVA procedure for a split unit design with trial as the main experimental unit and grazing period as the split unit. The effects of infection status, contamination pattern and appropriate interactions were investigated Ž . Source of variation Degrees of freedom missing values Main residual stratum Contamination pattern 1 Grazing period 1 Contamination pattern=grazing period 1 Residual 8 Main residual units stratum Infection status 1 Infection status=contamination pattern 1 Infection status=grazing period 1 Ž . Residual 8 1 Ž . Total 22 1 Log transformations were taken of larval count data prior to analysis. The difference between larval counts from pasture and ingested herbage was determined and this difference was subjected to a two-way ANOVA to investigate the effects of infection status and contamination pattern.

3. Results

3.1. Herbage parameters In experiment 1 contamination of patches with faeces had no significant effect on the Ž in vitro OMD uncontaminated: 0.69 0.01; contaminated: 0.69 0.01; F s 0.02, 1,34 . Ž y1 P 0.8 or the concentration of nitrogen uncontaminated: 26.0 0.5 g kg DM ; y1 . contaminated: 25.2 0.4 g kg DM ; F s 1.30, P 0.2 . In experiment 2, contami- 1,34 Ž nation of patches with faeces had no significant effect on the in vitro OMD uncon- . taminated: 0.81 0.01; contaminated: 0.81 0.01; F s 0.13, P 0.7 or the con- 1,28 Ž y1 centration of nitrogen uncontaminated: 24.7 0.7 g kg DM ; uncontaminated: 24.5 y1 . 0.5 g kg DM ; F s 0.06, P 0.8 . This confirmed that faecal contamination had no 1,28 effect on the sward chemical characteristics measured. 3.1.1. Experiment 1 Larvae were recovered from both contaminated and uncontaminated patches within Ž . plots regardless of the source of contamination treatment Table 2 , although counts were negligible on uncontaminated patches and patches contaminated with faeces from uninfected animals. The source of contamination on plots had no significant effect on Ž . larva counts obtained from uncontaminated patches F s 0.432, P 0.6 . There was 2,15 Table 2 Pasture larva counts expressed as number of larvae kg DM y1 herbage for plots with three different types of Ž . contamination mean valuess.e.; ns6 Type of contamination Patch type Contaminated Uncontaminated Ž . Faeces from parasite-free animal F 2511 64 Ž . Faeces from parasite infected animal FP 36441636 2916 Ž . Parasites P 47661942 126 no significant difference between larva counts from contaminated and uncontaminated Ž . plots from plot type F t s 1.38, df s 0.10, P 0.1 Larval counts differed significantly Ž between contaminated and uncontaminated patches on plot type FP F s 27.1, 1,10 . Ž . P - 0.001 and on plot type P F s 47.5, P - 0.001 . There was no significant 1,10 difference between larval counts obtained from contaminated patches on plot type FP Ž . and those from plot type P F s 0.25, P 0.6 . 1,10 3.2. Parasitic status of animals In experiment 1, all animals excreted nematode eggs on the first day of grazing trials Ž . mean faecal egg count 458; range 126–905 eggs per gram of faeces . In both experiments, infected animals were free of clinical signs of infection throughout the study. In experiment 2, nematode eggs were not excreted by any of the non-parasitized animals. Parasitized animals all excreted nematode eggs on the first day of grazing trials Ž . mean faecal egg count 543; range 99–1517 eggs per gram of faeces . 3.3. Patch selection 3.3.1. Experiment 1 Single-sample t-tests revealed that sheep spent significantly more time grazing in Ž uncontaminated patches than in faecal contaminated patches expected value with no discriminations 0.500; Plot F: proportion of observations in uncontaminated patches s 0.759, t s 8.56, df s 5, P - 0.001; Plot FP: proportion of observations in uncontami- . nated patches s 0.805, t s 10.57, df s 6, P - 0.001 . However, where plots were Ž . contaminated only with O. circumcincta larvae P , sheep showed no preference for Ž either contaminated or uncontaminated patches expected value with no discrimination s 0.500; proportion of observations in uncontaminated patches s 0.529; t s 0.56, df s 5, . Ž . P 0.5 Fig. 2a . The proportion of time sheep spent grazing uncontaminated patches on plots contami- Ž . nated with faeces from infected animals FP did not differ from the proportion of time spent grazing uncontaminated patches on plots contaminated with faeces from infected Ž . Ž . animals F F s 1.2, P 0.2 . The proportion of time spent grazing uncontaminated 1,10 Ž . patches was lower when animals grazed plots contaminated with parasite larvae P than Ž . Fig. 2. a Proportion of total grazing time spent in uncontaminated patches by infected sheep grazing plots Ž . Ž . with three different sources of contamination mean valuess.e. ; ns6. b Duration of grazing bouts in Ž uncontaminated patches by infected sheep grazing plots with varying sources of contamination mean . valuess.e. ; ns6. Ž . Ž . when they grazed plots contaminated with faeces from infected FP or uninfected F Ž . animals F s 14.7, P - 0.001 . 2,15 The average amount of time spent in an uncontaminated patch during discrete foraging bouts was greater when sheep grazed plots contaminated with faeces than when Ž . they grazed plots contaminated with only parasites F s 12.39, P - 0.001 . The 2,15 average length of a single encounter with an uncontaminated patches was not influenced Ž . Ž . by whether the faeces came from a worm-free F or a worm-infected sheep FP Ž . Ž . F s 0.612, P 0.4 Fig. 2b . 1,10 3.3.2. Experiment 2 The total proportion of each grazing period that was spent in uncontaminated patches is summarised in Table 3. A single-sample t-test showed that overall sheep spent more Ž time grazing in uncontaminated patches than in contaminated patches total mean proportion of observations in uncontaminated patches, 0.575; s.e.s 0.011; expected . value with no discriminations 0.500; t s 6.87, df s 22, P - 0.001 . Neither the pattern Ž . Ž . of contamination F s 0.23, P 0.6 nor the grazing period F s 1.60, P 0.2 1,8 1,8 had a significant effect on proportion of time spent grazing in uncontaminated patches. Ž . However, infected animals Group 2 spent a significantly higher proportion of their Ž . time F s 8.03, P s 0.022 grazing in uncontaminated areas than did uninfected 1,8 Ž . Ž . animals Group 4 Table 2 . A significant infection status = patch distribution pattern Ž . interaction F s 6.51, P s 0.034 indicated that discrimination between uncontami- 1,8 nated and contaminated patches was considerably greater by infected animals in the Ž . plots with the Large patch L contamination pattern whilst there was no significant Ž . Ž . difference in plots with the Small patch S contamination pattern Fig. 3a . The duration of discrete foraging bouts in uncontaminated patches is summarised in Table 4. Grazing period had no effect on the amount of time which was spent in each Ž . uncontaminated patch during a foraging bout F s 0.01, P 0.9 . The average 1,8 amount of time spent in an uncontaminated patch during any particular encounter was Ž . greater for infected animals than for uninfected animals F s 14.77, P s 0.005 . 1,8 Animals grazing the Large patch distribution spent longer in uncontaminated patches on Ž each individual encounter than when grazing the small patch distribution F s 12.29, 1,8 . P s 0.008 . There was a significant interaction between infection status and patch Ž . distribution pattern F s 8.65, P s 0.019 on the amount of time spent in an uncon- 1,8 taminated patch on each foraging bout. This was due to the difference between infected Table 3 Ž . Mean proportion of total time unfistulated animals Groups 2 and 4 spent grazing uncontaminated patches Ž . Ž . s.e. . Observations were recorded over two grazing periods period 1s 0–30 min; period 2 s60–90 min Period Contamination pattern Infection status and group Mean Infected — Group 2 Uninfected — Group 4 Ž . Ž . Ž . Ž . 1 Small patch S 0.5810.024 ns 3 0.5780.021 ns 3 0.5800.014 ns6 Ž . Ž . Ž . Ž . Large patch L 0.6500.021 ns 3 0.5570.032 ns 3 0.6030.027 ns6 Ž . Ž . Ž . Ž . Mean Period 1 0.6150.021 ns6 0.5680.018 ns6 0.5910.015 ns12 Ž . Ž . Ž . Ž . 2 Small Patch S 0.5670.021 ns 3 0.5610.024 ns 3 0.5640.014 ns6 Ž . Ž . Ž . Ž . Large patch L 0.5830.022 ns 2 0.5290.045 ns 3 0.5510.029 ns 5 Ž . Ž . Ž . Ž . Mean Period 2 0.5740.014 ns 5 0.5450.024 ns6 0.5580.015 ns11 Ž . Ž . Ž . Overall mean 0.5960.014 ns11 0.5560.015 ns12 0.5750.011 ns 23 Ž . Fig. 3. a Proportion of total grazing time spent in uncontaminated patches by infected and uninfected sheep Ž . grazing plots with two different contamination patterns mean valuess.e. . Sheep rested during the second Ž . period of one grazing trial and data was not collected. Hence, for infected animals Group 2 , grazing Large Ž . Ž . patch L contamination pattern, ns 5. In all other cases ns6. b Duration of grazing bouts in uncontami- Ž . nated patches for infected and uninfected sheep on plots of varying contamination pattern mean valuess.e. . Sheep rested during the second period of one grazing trial and data was not collected. Hence, for infected Ž . Ž . animals Group 2 grazing Large patch L contamination pattern, ns 5. In all other cases ns6. Table 4 Ž . Ž Duration of discrete sampling events min in uncontaminated patches by unfistulated animals Groups 2 and . Ž . Ž 4 . Observations were recorded over two grazing periods Period 1s 0–30 min; Period 2 s60–90 min mean . valuess.e. Period Contamination pattern Infection status and group Mean Infected — Group 2 Uninfected — Group 4 Ž . Ž . Ž . Ž . 1 Small patch S 2.600.12 ns 3 2.270.12 ns 3 2.430.11 ns6 Ž . Ž . Ž . Ž . Large patch L 4.370.47 ns 3 2.930.60 ns 3 3.650.47 ns6 Ž . Ž . Ž . Ž . Mean Period 1 3.480.45 ns6 2.600.31 ns6 3.040.29 ns12 Ž . Ž . Ž . Ž . 2 Small patch S 2.500.30 ns 3 2.430.15 ns 3 2.470.15 ns6 Ž . Ž . Ž . Ž . Large patch L 4.401.10 ns 2 2.670.35 ns 3 3.360.58 ns 5 Ž . Ž . Ž . Ž . Mean Period 2 3.260.60 ns 5 2.550.18 ns6 2.870.30 ns11 Ž . Ž . Ž . Overall mean 3.380.35 ns11 2.580.17 ns12 2.980.20 ns 23 and uninfected animals being greater when animals grazed the Large patch distribution Ž . Fig. 3b . 3.4. LarÕa counts from pasture and ingested herbage samples Larval counts from pasture and ingested herbage obtained in experiment 2 are summarised in Table 5. Overall, the number of larvae recovered from ingested herbage Ž y1 . 155 19 kg DM were lower than the number that were obtained from pasture Ž y1 . herbage 286 63 kg DM . Paired t-test results showed that this difference verged on Ž . significance t s 2.09, df s 17, P - 0.052 . ANOVA results showed that overall, the difference between larval counts from ingested and pasture herbage was not influenced Ž . by the infection status of sheep F s 0.047, P 0.8 or by the distribution pattern of 1,12 Ž . contamination F s 0.668, P 0.5 . However, there was a significant status = pattern 2,12 Ž . Ž . interaction F s 6.215, P s 0.014 Fig. 4 . The largest difference between the 2,12 number of larvae isolated from pasture and the number isolated from ingested samples occurred when infected animals grazed plots with a dispersed pattern of contamination Ž . Ž . D . When plots with a dispersed contamination pattern D were grazed by uninfected sheep the difference between the number of larvae from pasture and ingested herbage Table 5 Larval counts from herbage ingested by fistulated animals, expressed as number of larvae per kg dry matter, for infected and uninfected animals grazing plots with three patterns of contamination. Counts from Ž . corresponding pasture herbage samples are also given mean valuess.e. Infection status Herbage Contamination pattern Mean type Ž . Ž . Ž . Dispersed D Small patch S Large patch L Ž . Ž . Ž . Ž . Infected Ingested 23171 ns 3 15016 ns 3 11821 ns 3 16628 ns9 Ž . Ž . Ž . Ž . Ž . Group 1 Pasture 47757 ns 3 19556 ns 3 485361 ns 3 26540 ns 21 Ž . Ž . Ž . Ž . Uninfected Ingested 21560 ns 3 8710 ns 3 1279 ns 3 14326 ns9 Ž . Ž . Ž . Ž . Ž . Group 3 Pasture 24267 ns 3 15739 ns 3 1609 ns 3 19326 ns 21 Ž . Ž . Ž . Ž . Mean Ingested 22342 ns6 13910 ns6 10212 ns6 15519 ns18 Ž . Ž . Ž . Ž . Pasture 36066 ns6 17632 ns6 322177 ns6 28663 ns18 Fig. 4. The difference between ingested and pasture herbage counts for infected and uninfected sheep grazing Ž . plots with different patterns of contamination mean valuess.e. ; ns 3. Ž samples was lower than when aggregated patterns of contamination were grazed S and . Ž . Ž . L . When sheep grazed plots with either a Small S or Large L patch contamination pattern, the difference between the number of larvae on herbage and the number that were ingested was greatest for uninfected animals.

4. Discussion and conclusions