Postpartum reproductive performance of dairy cows in medium and large scale farms in Kiambu and Nakuru districts of Kenya

Abstract

The goal of a reproductive management programme is to ensure that cows conceive within given time limit for optimal production and maximum profitability. In intensive dairy production systems in temperate countries, a calving interval of 12.5 months is dependent on early estrus detection and a short calving to conception interval of less than 90 days and is rated as economically beneficial. Reproductive performance of dairy cows in Kenya has only been evaluated in the smallholder production systems for which it is described as fair to poor. However, there is scanty information on the reproductive performance of dairy cows in medium and large scale farms in Kenya. A longitudinal study was undertaken in four medium and four large scale dairy farms in Kiambu and Nakuru districts of Kenya. The objectives of this study were: (1) To determine the status of the reproductive tract of dairy cows between day 30 and day 35 postpartum, (2) To determine postpartum reproductive performance of dairy cows by evaluating the following reproductive indices, calving to first observed heat interval, calving to first insemination interval, calving to conception interval and number of services per conception, (3) To evaluate and identify management-level and cow-level risk factors that may influence the reproductive performance indices. A total of 20 1 dairy cows that had either calved recently or were in their last month of gestation were recruited into the study. Each cow was examined once by per rectal palpation and vaginoscopy between day 30 and day 35 postpartum so as to determine the status of the reproductive tract. The study cows were then closely monitored for 7 consecutive months or until confirmed pregnant. Cow-level and management-level risk factors were noted and recorded. The Chi square (i) statistic was used to determine unconditional associations between the reproductive performance indices and the risk factors at p<0.05. Stepwise logistic regression was carried out to model the effects of cow-level and management-level risk factors against the four reproductive performance indices. The results revealed that by days 30-35 postpartum, 80% of the cows had resumed ovarian cyclicity, 73% had an involuted cervix and 40% had an involuted uterus. The most common postpartum disease encountered was clinical endometritis (15%). Vaginoscopy examination found 42% (79) of cows with various types of cervical discharges. Of these, only 15 cows were found to have either vulva discharge or perineum matting on visual inspection. The average intervals of calving to ftrst observed heat, calving to first insemination and calving to conception were 63.1, 86.8 and 117.7 days respectively. The cost of the high number of open days to the farms was estimated from projected milk loss per lactation and calves lost per cow's productive herd life. The average number of services per conception was 2.0. The factors found to be associated with calving to first observed heat of less than 40 days were: clear stringy cervical mucusKi.R. = 29.1, P <0.0001) compared to cloudy or purulent cervical discharge (O.R. = 5.9, P = 0.00l3), uterine horn diameters of less than 5cm (O.R. = 2.4, P = 0.0206) and an open cervix (O.R. = 5.8, P =0.0003). Calving to first insemination interval of less than 68 days was positively associated with a voluntary waiting period of 42 days (O.R. = 27.8, P <0.0001), but negatively associated with endometritis (~-estimate = - 0.752). Cows that did not receive any postpartum treatment (O.R. = 2.3, P =0.0148) and those that did not develop any postpartum disease (O.R. = 3.2, P :0.0091)were significantly associated with less than 2 services before conception.

Cows with >5cm uterine horn diameters were likely to have more than 2 inseminations (~- estimate = - 0.362) before conception. Factors that were positively associated with an optimal calving to conception interval of < 98 days were clear stringy cervical mucus (O.R. = 10.7, P =0.0006) on days 30-35 post-calving, postpartum intrauterine irrigation with povidone iodine (O.R.= 6.2, P <0.0001) and cows in their 2nd parity (O.R. = 3.2, P = 0.0069). The study concluded that reproductive performance of dairy cows in the medium and large scale farms in the two districts was sub-optimal despite finding the reproductive tract and ovaries reverted to normal functional status by days 30 to 35 postpartum. The sub-optimal performancewas attributed to the management laxity in observing for postpartum heat during the time preceding expiry of the voluntary waiting period this resulted in a delay in the calving to first observed heat interval. This subsequently delayed the calving to conception interval hence negatively impacting on the overall reproductive performance of s~udy cows. Reproductive inefficiency leads to excessively long lactations where cost of milk production may be higher than the revenues gained from milk. A situation that is aggravated by reduced calf-crop per cow and hence inadequate numbers of replacement heifers to maintain stable herd size. In the present study, the failure to detect heat early in the postpartum period cost the farms an estimated Ksh. 5, 4344 to Ksh. 12,540 per cow per year as loss in revenue due to foregonemilk for the extra 19 open days past the recommended 98 days calving to conception interval. However, this loss was over and above the reduced calf crop per cows herd life that affectsthe pool of heifer calves from which to select the replacement stock. The reproductive performance as measured by calving to conception interval of 117.7 days, for medium and large scale dairy farms, was better than that of 385 days reported for dairy cows in smallholder production systems in Kenya. The study also concluded that the use of vaginoscopy technique should be encouraged as a complement to per rectal palpation as it would enhance the detection of postpartum reproductive tract diseases, particularly endometritis. Considering that the ovaries had resumed cyclicity in all the cows within 35 days postpartum, it was recommended that medium and large scale dairy farms regardless of the voluntary waiting period in practice observe and record heat occurring before the expiry of the VWP. This will enable early detection of anoestrous cows and timely institution of appropriate interventions. The magnitude of loss in large dairy herds due to foregone milk and calves would more than meet the cost of enhanced heat detection by hiring and training more stockmen on heat detection methods in medium and large scale farms. This would improve reproductive efficiency by reducing the calving to conception interval. Future studies should focus on reproductive efficiency in intensively managed dairy production systems including zero-grazing unit as they produce more than 80% of milk sold in the Kenyan market.