Are calving interval, abortions, incidence of stillbirths and pre-weaning losses in Nguni cows associated with linear type traits?

Abstract

The association of six linear type traits with calving interval, abortions, incidence of stillbirths and pre-weaning losses in Nguni cows in semi-arid and sub-humid communal areas was investigated. It was hypothesised that the odds of a cow having caving interval greater than 1 year, aborting, experiencing stillbirths or losing a calf from calving to weaning decreased with increase in body depth, rump height, flank circumference, chest circumference, navel height and body length. Navel height was measured as the distance from the ground to the lowest point of the cow's belly bottom (navel). Data were collected from a total of 200 Nguni cows from two sites experiencing sub-humid and semi-arid environments (100 each) between May and June 2013. Cows in sub-humid regions were 2.57 times more likely to have a calving interval of 1 year than cows in semi-arid areas. As body depth increased, the number of calves lost by a cow before weaning decreased linearly (p<0.05) in all parities except parity 4. Cows in semi-arid regions were 2.13 times more likely to lose a calf from calving to weaning. For each unit increase in body depth, the odds of a cow aborting decreased by 1.12 and the odds of a cow having stillbirth decreased by 1.15. Rump height, flank circumference, chest circumference, navel height and body length were not associated with calving interval, abortions, incidence of stillbirths and pre-weaning losses. It was, therefore, concluded that body depth influences calving interval, incidence of stillbirths and abortions in Nguni cows.