ANALYSIS OF EFFECTS OF TSETSE CONTROL ON LIVESTOCK PRODUCTIVITY AND HEALTH
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ANALYSIS OF EFFECTS OF TSETSE CONTROL ON LIVESTOCK PRODUCTIVITY AND HEALTH. Nicholas N. Ndiwa, Woudyalew Mulatu and John Rowlands International Livestock Research Institute. BACKGROUND.

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Analysis of effects of tsetse control on livestock productivity and health

ANALYSIS OF EFFECTS OF TSETSE CONTROL ON LIVESTOCK PRODUCTIVITY AND HEALTH

Nicholas N. Ndiwa, Woudyalew Mulatu and John Rowlands

International Livestock Research Institute


Analysis of effects of tsetse control on livestock productivity and health

BACKGROUND PRODUCTIVITY AND HEALTH

  • Trypanosomosis is a serious disease affecting livestock in many parts of sub-Saharan Africa including Ethiopia.

  • The parasite that causes the disease is carried by the tsetse fly.

  • Persistently high levels of trypanosomosis found in cattle at Ghibe in southwest Ethiopia, where ILRI works, occur because of drug resistance.

  • Thus, drug therapy on its own at Ghibe does not work.

  • The alternative is to reduce the numbers of tsetse flies.

  • Two interventions to control tsetse numbers have been implemented

  • 1. - with insecticide impregnated targets

  • 2. - with insecticide pour-on applied to the backs of cattle.


Analysis of effects of tsetse control on livestock productivity and health

Drug treatments for disease cases PRODUCTIVITY AND HEALTH

Time-line of treatments and tsetse control interventions

Invasion of third tsetse species

Drug treatment for all cattle

Drug treatment for all cattle

Jul-89

Jul-91

Jul-93

Jul-87

Jul-95

Jul-97

Mar-90

Mar-92

Mar-94

Mar-86

Mar-88

Mar-96

Mar-98

Nov-90

Nov-92

Nov-94

Nov-86

Nov-88

Nov-96

Targets

Pour-on

Theft of the targets


Analysis of effects of tsetse control on livestock productivity and health

Measurements were made monthly on the following: PRODUCTIVITY AND HEALTH

  • Packed cell volume (PCV)

  • Trypanosome prevalence

  • Body weight

Calves were ear-tagged at birth and their details recorded.

Disposal (deaths, disappearance or sales) were also recorded.


Analysis of effects of tsetse control on livestock productivity and health

Productivity and health variables calculated PRODUCTIVITY AND HEALTH

  • Tsetse density

  • Mean body weight, PCV, trypanosome prevalence, no. of treatments - separately for males and females

  • Calf growth rate and 12-month body weight

  • Mortality rate in males, females and calves

  • Abortion rate and calf/cow ratio to reflect fertility level

  • Herd size


Analysis of effects of tsetse control on livestock productivity and health

Possible time units for analysis PRODUCTIVITY AND HEALTH

One month?

Problems? - handling seasonal variation

- handling increasing ages of cattle

- handling pregnancy and lactation

- positive serial correlations from month to month

- other confounding random variables (e.g rainfall)

Three months?

Problems? - handling seasonal variation

- other confounding random variables

- also age, pregnancy, lactation

Six months?

- now possible to match with season (wet and dry)

- other factors not so important

Twelve months?

- best for matching with agronomic (planting and harvesting) and livestock production / management

- matches annual rain cycle


Analysis of effects of tsetse control on livestock productivity and health

Data set structure PRODUCTIVITY AND HEALTH


Analysis of effects of tsetse control on livestock productivity and health

Statistical model PRODUCTIVITY AND HEALTH

yijk=+si+pj+ck+(pc)jk+eijk

where s=season, p=period and c=control

Interaction not significant for any variable. Hence dropped for final model


Analysis of effects of tsetse control on livestock productivity and health

Genstat output for analysis of body weights for bulls PRODUCTIVITY AND HEALTH

Estimates of parameters

estimate s.e. t(18) t pr.

Constant 217.24 5.53 39.28 <.001

SEASON 2 6.48 5.07 1.28 0.217

PERIOD 2 11.06 5.10 2.17 0.044

CONTROL 2 11.40 5.28 2.16 <.045

Accumulated analysis of variance

Change d.f. s.s. m.s. v.r. F pr.

+ SEASON 1 231.11 231.1 1.64 0.217

+ PERIOD 1 762.3 762.3 5.40 0.032

+ CONTROL 1 658.2 658.2 4.66 <.045

Residual 18 2543.3 141.3

Total 21 4194.8 199.8

Least square means

Control Body weight s.e.

0 226.52 4.21

1 237.91 3.18


Analysis of effects of tsetse control on livestock productivity and health

Variable Tsetse control PRODUCTIVITY AND HEALTH

without withSEDP Change (%)

Bulls

Body weight (kg) 226.52 237.91 5.28 <0.001 8

PCV (%) 22.8 23.8 0.64 <0.01 7

Trypanasome prevalence (%) 0.36 0.31 0.042 <0.05 24

Annual mortality (%) 0.20 0.11 0.039 <0.001 62

Calves

Growth rate – wet season (kg/month) 0.22 0.23 0.025 0. 4

Body weight at 12 months (kg) 68 76 2.2 <0.01 12

Effect of tsetse control on selected variables


Analysis of effects of tsetse control on livestock productivity and health

Targets PRODUCTIVITY AND HEALTH

Pour-on


Analysis of effects of tsetse control on livestock productivity and health

Targets PRODUCTIVITY AND HEALTH

Pour-on


Analysis of effects of tsetse control on livestock productivity and health

Targets PRODUCTIVITY AND HEALTH

Pour-on


Analysis of effects of tsetse control on livestock productivity and health

Targets PRODUCTIVITY AND HEALTH

Pour-on


Analysis of effects of tsetse control on livestock productivity and health

  • Conclusions PRODUCTIVITY AND HEALTH

  • The general health of cattle improved with increased body weights and reduced mortality.

  • This corresponded to decreased trypanosome prevalence, although the average trypanosome prevalence still remained comparatively high.

  • Insecticidal pour-on has an effect, not only on tsetse, but also on other nuisance flies. This may also have helped towards improved cattle health over this period.

  • The analytical approach we adopted provided an analysis that simplified the difficulties in dealing with confounding factors and serial correlations between successive measurements.


Analysis of effects of tsetse control on livestock productivity and health

  • Conclusions PRODUCTIVITY AND HEALTH(continued)

  • We lagged the effect of tsetse control by 6-months based on the knowledge that the intervention of tsetse control has a delayed effect. The data appeared to show this.

  • Our method resulted in 13 observational units when tsetse control was applied and 9 when not; this was more than adequate for the statistical analysis.

  • The length of the study demonstrated that application of tsetse control can be sustainable.