Influence of parity, birth order, litter size and birth weight on duration of farrowing and birth intervals in commercial exotic sows in Zimbabwe

Although the farrowing process has an impact on postnatal piglet survivability and growth performance, information on factors that influence the farrowing process under field conditions is rare. The objective of the study was to determine factors influencing the duration of farrowing and birth intervals in Large WhitexLandrace crossbred sows. Data were collected from the Pig Industry Board, Acturus, Zimbabwe. The durations of farrowing were log transformed to normalize them, while birth intervals remained skewed after the transformation. As a result, Friedman's test was used to analyse for factors affecting birth intervals. The mean duration of farrowing was 217 min. Number of piglets born alive (NBA), average birth weight and the presence or absence of stillbirths influenced ( P < 0.05) the duration of farrowing. The total number of piglets born (NBT) and order of piglets significantly influenced birth intervals ( P < 0.05). There was wide variation in birth intervals, with the within-litter coefficient of variation ranging from 50 to 140 percent. The relationship between birth interval and order of birth was: Y=0.1011x(2)-1.771x+37.917 ( P < 0.05). Relative birth order, expressed as a proportion of the total number of piglets born, also showed a significant quadratic relationship with birth interval: Y=0.0021x(2)-0.121x+23.952 ( P < 0.05). The study found that relative birth order, NBA and NBT play an important role in influencing birth intervals and duration of farrowing, while parity and piglet weight do not. Logarithmic transformation failed to normalise data on birth intervals, highlighting their highly skewed nature.