Veterinary Epidemiology

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Browsing Veterinary Epidemiology by Author "AHMED, IBRAHIM"

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    EFFECT OF FAILURE OF PASSIVE TRANSFER OF IMMUNITY ON CRUDE MORBIDITY AND MORTALITY IN DAIRY CALVES
    (2007-06) AHMED, IBRAHIM; Prof. G. Gupta, Dr. Alemayehu Lemma
    A longitudinal prospective observational study on the concentrations of serum total protein (STP), as a measure of status of passive immunity, and its associations with crude calf morbidity and mortality in dairy farms in Debre Zeit and its surroundings was conducted from October 6, 2006 to May 15, 2007, with the objectives of determining the proportions of calves with failure of passive transfer (FPT) of immunity, describing the incidence rates of crude morbidity and mortality, and investigating the associations of the status of passive transfer of immunity with crude morbidity and mortality in the newborn dairy calves. A total of 354 crossbred dairy calves were included in the study. Serum samples were collected when the calves were from 24hrs to one week of age, and regularly monitored for clinical outcomes (morbidity and mortality) up to the age of six months. The mean STP concentration as measured during the first week of life was 66.4+16.6g/L and the values ranged from 28.8 to 99.8g/L. The proportion of calves with FPT, (where the STP concentrations were less than or equal to 55g/L) was found to be 30.23%. The overall incidence rate of crude morbidity and crude mortality found in this study were 52.3% and 18.9% respectively. A total of 21 potential risk factors were investigated for their associations with FPT, crude morbidity and crude mortality. Among these 9 variables that were considered for their effect on the status of passive transfer, 7 were found to be statistically significantly associated with FPT. Further analysis of these factors using logistic regression indicated that only 4 factors, age of the dam as represented by parity number (OR = 14.6, 95% CI = 6.27-33.84), age at first colostrum ingestion (OR = 7.2, 95% CI = 2.56-20.13), attendant at parturation (OR = 4.4, 95% CI = 1.48-13.10) and sex of the calf (OR = 3.8; 95% CI= 1.61-8.83) were significantly associated with FPT. Univariate analysis of 10 risk factors of crude morbidity showed that 6 factors were significantly associated with crude morbidity, but on multivariate analysis, only STP (OR = 11, 95% CI = 4.4-27.4) and attendant at birth (OR = 2.7, 95% CI = 1.3-7.2) had significant interaction in causing morbidity. Similarly, Cox regression model indicated that STP (p< 0.001), attendant at birth (p< 0.05), age at first colostrum ingestion (p< 0.05) and birth condition (p< 0.05) were significantly viii associated with earlier age at the onset of crude morbidity. The effect of FPT on crude morbidity was further analyzed by partitioning the crude morbidity into 8 STP strata and the highest incidence rates of crude morbidity (>95%) were observed in calves with STP concentrations < 55g/L, but a remarkable drop of crude morbidity was seen in calves with STP concentrations >65g/L. On the other hand, the greatest relative risk (RR = 2.5, 95% CI = 2.07-2.93) of crude morbidity were observed in calves with STP concentrations of < 55g/L. Out of 11 risk factors of crude mortality, 9 were showed significant association on univariate analysis, but when adjusted for their interaction, only age at the onset of morbidity (OR = 27.2, 95% CI = 7.6-97.1), STP (OR = 3.1, 95% CI = 1.4-9.2) and sex (OR = 2.7, 95% CI = 1.3-5.7) were found to be significantly associated with crude mortality. Similarly, Proportional Hazard (Cox) Regression showed that age at the onset of morbidity (p< 0.001), STP concentrations (p< 0.001), sex (p< 0.05) and time of birth (p< 0.05) were significantly associated with mortality at an earlier age of the calf. Furthermore, the highest incidence rate of crude mortality was observed in calves with STP concentrations < 55g/L, while the greatest relative risk (RR = 5.3, 95% CI = 3.73-7.56) of crude mortality was experienced by calves with STP concentrations < 35g/L. Calves with STP concentrations of 35.1-45.0 and 45.1-55.0g/L had lower relative risk (RR = 2.2, 95% CI = 1.32-3.81 and 2.9, 95% CI = 1.86-4.39, respectively) of crude mortality compared to calves with STP concentration < 35g/L. The optimum survival was observed in calves with STP concentrations > 55g/L with insignificant relative risk of crude mortality. Thirty three percent of the total death was attributed to FPT. Calves with lower STP values due to FPT of colostral immunity had increased risk of death and measuring the degree of passive transfer of colostral immunity at the first week of age was very important to proper management of young calves.