Factors influencing postpartal reproductive traits of crossbred dairy cows in the Sudan

Abstract

The purpose of the present study is to determine postpartal reproductive traits such as the time required for complete uterine involution, commencement of ovarian activity, first postpartum oestrus, the open period, number of services per conception and the calving interval. Moreover, factors affecting these parameters such as, age, parity, body weight, milk yield at the first three months, foreign blood percentage and season were considered. Eighty six (86) recently calved crossbred (Kenana or Butana X Friesian) dairy cows and heifers from Khartoum University Farm were used. Their ages were between 2.5 – 17.0 years and the number of calvings was between the first and the tenth. All cows were identified by ear tags, and the data about age, age at first calving, parity, date of last calving, foreign blood percentage, milk yield at first three months, life body weight, nature of last calving, calving interval, reproductive disorder and oestrous cycle were available. Rectal palpation had been done once weekly immediately after calving till the appearance of first postpartal oestrus. The uterus was examined till it returned to its pregravid size. The two ovaries were examined for the changes occurred such as, graffian follicles, ovulation, corpus luteum and ovarian cysts. Each animal was observed visually to detect the first oestrus postpartum. Body weight had been recorded every 15 days till the animal had been inseminated. 12 The findings of rectal palpation of the uterus showed that time required for complete uterine involution with an overall average of 30.44±3.16 days. The results obtained from manipulation of ovaries indicated that commencement of ovarian activity occurred at an overall average of 31.64±11.37 days. The observation of recrudescence first oestrus postpartum took an overall average of 62.90±22.17 days. The open period till the cow was served lasted on an overall average of 158.69±85.12 days. The average number of services per conception for all cows was 4.45±1.80. The effect of age on uterine involution was strong (r=0.615). There was weak effect of age on the time of commencement of ovarian activity (r= -0.186), and occurrence of first oestrus (r=0.134). However, there was no correlation (r=0.046) between age and open period, and the effect of age on number of services per conception was weak (r=0.150). The effect of body weight on uterine involution was moderate (r=0.279). Nevertheless, body weight had a moderate negative correlation with ovarian activity, and occurrence of first oestrus (r= -0.222, r= -0.231, respectively). There was no significant effect of body weight on open period (r= - 0.099), or on number of services per conception (r= -0.137). The effect of foreign blood percentage was weak on uterine involution (r= - 0.197). The foreign blood percentage had no significant effect on almost all the reproductive traits studied except for the open period, where moderate correlation was computed (r=0.238). There was weak effect of foreign blood percentage on number of services per conception (r=0.185). 13 Parity had a strong positive correlation (r=0.523) on uterine involution, and a weak negative correlation (r= -0.181) with ovarian activity. On the other hand parity showed no effects on occurrence of first oestrus (r=0.071). or on open period (r= -0.029), and the same result was obtained with the number of services per conception (r=0.053). The effect of milk yield on uterine involution was moderate (r=0.289). No effect of milk yield on ovarian activity (r= -0.076), neither on occurrence of first oestrus (r=0.041), nor on open period (r=0.021), and the same was true with the number of services per conception (r= -0.019). The effect of season was strong on uterine involution (r= -0.328), ovarian activity (r= -0.327), and on occurrence of first oestrus (r= -0.391). Periods required to accomplish these parameters were significantly reduced during Winter compared to Summer. However, There was no effect of season on open period (r=0.054), nor on number of services per conception (r= -0.048). This study concluded that postpartal reproductive traits of crossbred cows in the Sudan were comparable to those of their temperate ancestor except for the open period and calving interval where managemental problems could be questioned. Many factors were found to affect postpartal traits including, age, body weight, parity, milk yield, season and the foreign blood inheritance and they should be carefully approached in any crossbreeding programmes for improvement of dairy production in idigenous cows.