Use of heart girth to predict body weight of working oxen in the Ethiopian highlands

Models to predict live weight from heart girth in crossbred beef heifers

The objective of this study was to develop and evaluate linear, quadratic, and exponential mathematical models to predict live weight (LW) from heart girth (HG) in crossbred heifers raised in tropical humid conditions in Mexico. Live weight (363.32 ± 150.88 kg) and HG (166.83 ± 24.88 cm) were measured in 400 heifers aged between 3 and 24 months. Linear and non-linear regression was used to construct the prediction models. The goodness of fit of the models was evaluated using the Akaike information criterion (AIC), the Bayesian information criterion (BIC), coefficient of determination (R²), mean squared error (MSE), and root MSE (RMSE). In addition, the developed models were evaluated through internal and external cross-validation (k-folds) using independent data. The ability of the fitted models to predict the observed values was evaluated based on the root mean square error of prediction (RMSEP), R², and mean absolute error (MAE). The correlation coefficient between LW and HG was r = 0.98 (P < 0.001). The quadratic model showed the lowest values of MAE (736.57), RMSEP (27.13), AIC (3783.95), and BIC (3799.91). Additionally, this model exhibited better goodness-of-fit values regarding external and internal validation criteria (higher R² and lower RMSEP and MAE), thus having better predictive performance. The RMSE represented about 8% of the observed LW. Heart girth is highly correlated (r = 0.98) with LW. The quadratic model showed a high predictive capacity for crossbred heifers kept in tropical conditions.

Estimation of Liveweight from Body Measurements through Best Fitted Regression Model in Dezhou Donkey Breed

Dezhou donkey is an excellent local hide, meat and milk breed in Shandong Province. To accelerate the speed of breeding, reproduction and conversation, correlation and multiple regression analysis between body weight (BW) and body size of Dezhou donkey rearing under intensive farms was made by SAS 9.4 software (Statistical Analysis for Windows). A total of 162 donkeys of both gender of age 2 ~ 10 years old were used to investigate the relationships between BW and body dimensional traits (cm) including height of withers, body length; thoracic depth, thoracic girth (TG), thoracic width (TW), circumference of cannon bone (CB), height of rump, rump length (RL) and rump width (RW). The results showed that BW and body measurements have positive and great correlations with R² value ranged from 0.58 to 0.88 (P <0.01). The R² values from the single-parameter equations showed that the TG was highly related to BW (0.72, P < 0.01). The stepwise regression equations were applied to obtain the best prediction equations, and the results indicated that the prediction accuracy for BW was improved with the inclusion of more body measurement variables. The "best fit" models were: BW (kg) = 1.88 × TG + 1.27 × BL + 2.55 × TW + 4.61 × CB + 2.18 × RW + 1.78 × RL - 422.8 (R² = 0.906, P < .01). The predicted BW from the present equations showed the nearest value to the real BW (R² > 0.94, P < .01). In addition, the equations derived to predict the BW of donkeys in Britain, Morocco were less satisfactory for use with the present Dezhou donkey breed because they overestimated or underestimated the BW due to the different donkey breed.

Simple and robust algorithms to estimate liveweight in African smallholder cattle

Measurement of liveweight of stock is one of the most important production tools available to farmers – playing a role in nutrition, fertility management, health and marketing. Yet most farmers in sub-Saharan Africa do not have access to scales on which to weigh cattle. Heart girth measurements (and accompanying algorithms) have been used as a convenient and cost-effective alternative to scales, however despite a plethora of studies in the extant literature, the accuracy and sensitivity of such measures are not well described. Using three datasets from phenotypically and geographically diverse cattle populations, we developed and validated new algorithms with similar R2 to extant studies but lower errors of prediction over a full range of observed weights, than simple linear regression, that was valid for measurements in an unassociated animal population in sub-Saharan Africa. Our results further show that heart girth measurements are not sufficiently sensitive to accurately assess seasonal liveweight fluctuations in cattle and thus should not be relied on in situations where high precision is a critical consideration.

Pathogen Exposure in Cattle at the Livestock-Wildlife Interface

Land use is an important driver of variation in human infectious disease risk, but less is known about how land use affects disease risk in livestock. To understand how land use is associated with disease risk in livestock, we examined patterns of pathogen exposure in cattle across two livestock ranching systems in rural Kenya: private ranches with low- to medium-intensity cattle production and high wildlife densities, and group ranches with high-intensity cattle production and low wildlife densities. We surveyed cattle from six ranches for three pathogens: Brucella spp., bovine viral diarrhea virus (BVDV) and Leptospira serovar Hardjo. We found that exposure risk for Leptospira was higher on private ranches than on group ranches, but there was no difference in exposure by ranch type for Brucella or BVDV. We hypothesize that variation in livestock and wildlife contact patterns between ranch types may be driving the pattern observed for Leptospira exposure and that the different relationships we found between exposure risk and ranch type by pathogen may be explained by differences in transmission mode. Overall, our results suggest that wildlife-livestock contact patterns may play a key role in shaping pathogen transmission to livestock and that the magnitude of such effects likely depend on characteristics of the pathogen in question.

Use of body linear measurements to estimate liveweight of crossbred dairy cattle in smallholder farms in Kenya

Body linear measurements, and specifically heart girth (HG), have been shown to be useful predictors of cattle liveweight. To test the accuracy of body linear measurements for predicting liveweight, crossbred dairy cattle of different genotypes were measured and weighed. A total of 352 mature cows and 100 heifers were weighed using an electronic weighing scale and measurements of HG, body length, height at withers were taken using an ordinary measuring tape and body condition scored (BCS) using a five-point scale. The animals were grouped according to genotype and age. Genotype classification was undertaken from farmer recall and by visual appraisal as 40–60, 61–80 or 81–100 % exotic (non-indigenous). Age classification was simply as mature cows or heifers. Liveweight of the animals ranged from 102 to 433 kg. Liveweight was strongly correlated with HG (r = 0.84) and body condition scores (r = 0.70) and moderately correlated with body length (r = 0.64) and height at withers (0.61). Regressing LW on HG measurements gave statistically significant (P < 0.01) equations with R² ranging from of 0.53 to 0.78 and residual standard deviation ranging from 18.11 to 40.50 kg. The overall model developed (adjusted R² = 0.71) had a prediction error of 26 kg (or 11 % of the mean) and predicted LW of over 95 % of crossbred dairy cattle in the range of 100–450 kg, regardless of age and breed group. Including BCS in the model slightly improved the model fit but not the prediction error. It was concluded that the model can be useful in making general management decisions in smallholder farms.

Principal Component Analysis of Conformation and Blood Marker Traits at Pre- and Post-Weaning Stages of Growth in F2 Crossbred Nigerian Indigenous X Landrace Pigs

Linear body measurements and blood hematology and biochemistry parameters were taken on 92 and 15 grower pigs, respectively, chosen randomly from a crossbred F2 population of Nigerian Indigenous (NI) x Landrace pigs to evaluate body conformation and blood marker traits using a multivariate approach. For linear body measurements at pre-weaning stage (4 weeks old), two principal components accounted for 91.63% of the total variation in body conformation traits, while at post weaning stage (12 weeks old), one principal component accounted for 73.63% of the total variations in body conformation traits. The first factor (principal component) accounted for 72.34% of the total variance (body weight) while the second factor accounted for 19.29% (ear length) at pre-weaning stage. While at post-weaning stage only one factor contributed to the total variability of the original six traits tested, with 73.63% (body length). For blood parameters, three principal components accounted for 81.85% of the total variation at pre-weaning stage while 89.44% of the total variation at post-weaning stage was accounted for by four principal components. The first factor (principal component) accounted for 38.048% (Packed cell volume), the second accounted for 24.72% (hemoglobin) and the third accounted for 19.08% (aspartate transaminase). While at the post-weaning stage, the first factor was influenced by red blood corpuscles (37.17%), the second factor had its loading for hemoglobin (25.80%), the third factor had loading for white blood corpuscles (13.67%), while the fourth factor had loading for alkaline phosphatase only (12.80%). Using communality extraction factors, ear length best described body conformation at the pre-weaning stage; whereas, at post-weaning stage, body length was the best descriptor. In blood parameters, packed cell volume best described blood marker traits at the pre-weaning stage; whereas, at the post-weaning stage, red blood corpuscles best described it. Hence, the two extracted factors in linear body measurements and in blood parameters could be considered in breeding programs to improve and predict body conformation in crossbred pigs, as well as predict blood marker traits.

A live weight-heart girth relationship for accurate dosing of east African shorthorn zebu cattle

The accurate estimation of livestock weights is important for many aspects of livestock management including nutrition, production and appropriate dosing of pharmaceuticals. Subtherapeutic dosing has been shown to accelerate pathogen resistance which can have subsequent widespread impacts. There are a number of published models for the prediction of live weight from morphometric measurements of cattle, but many of these models use measurements difficult to gather and include complicated age, size and gender stratification. In this paper, we use data from the Infectious Diseases of East Africa calf cohort study and additional data collected at local markets in western Kenya to develop a simple model based on heart girth circumference to predict live weight of east African shorthorn zebu (SHZ) cattle. SHZ cattle are widespread throughout eastern and southern Africa and are economically important multipurpose animals. We demonstrate model accuracy by splitting the data into training and validation subsets and comparing fitted and predicted values. The final model is weight^0.262 = 0.95 + 0.022 × girth which has an R² value of 0.98 and 95 % prediction intervals that fall within the ±20 % body weight error band regarded as acceptable when dosing livestock. This model provides a highly reliable and accurate method for predicting weights of SHZ cattle using a single heart girth measurement which can be easily obtained with a tape measure in the field setting.

The small east african shorthorn zebu cows in Kenya. I: linear body measurements

Assessment of genetic diversity is a prerequisite for the management and conservation of animal genetic resources. Appropriate design of breeding programmes is therefore impossible for breeds that have not been adequately characterized either phenotypically and/or genetically. Phenotypic characteristics are important in breed identification and classification in ways that farming communities can relate with. This study phenotypically characterized two breeds of zebu cattle in Kenya. A total of 12 measurements (face length, ear length, horn length, heart girth, height at withers, chest depth, body length, height at rump, pelvis width, corpus length, pin bone width and tail length) were collected on 373 Maasai and 277 Kamba zebu kept by traditional farmers in south-east Kenya. The data were classified on the basis of breed group, age group, sex and coat colour pattern. Breed group, age group and sex significantly influenced all measurements. Coat colour pattern significantly influenced only height at withers, corpus length, ear length and tail length. Except for horn and ear length, all the other measurements were significantly higher for the Maasai zebu. Additionally, the Maasai zebu was taller than it was long. The opposite was true for the Kamba zebu. The Maasai and Kamba zebus can be classified as medium-sized breeds; however, great variations exist in their body sizes within and between the breeds.