الفهرس 
Introduction
Reproductive PerformanceOnly 14 pages are availabe for public view
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Abstract
The objective of this study was to evaluate the postpartum reproductive performance and ovarian activity of three lactating cow groups including buffalo (BF, n=28), Baladi (BA, n=13) and crossbreed (CB, n=13, Friesian x Baladi) during cold and hot seasons under the traditional conditions of Egyptian farmer. Results revealed that postpartum 1st ovulation interval was longer (P<0.05) in BF (35.0 d) than BA (17.4 d) and CB (19.1 d), being similar in cold and hot (23.1 d for each). Average ovulations/animal was 2.6 in both BF and BA and 3.2 in CB, being higher (3.2) in cold than in hot (2.6). Overall length of ovulatory cycle was 18.8, 19.6 and 18.5 d in BF, BA and CB, respectively, being similar in hot and cold (19.5 and 18.4 d). The highest frequency of ovulatory cycles was in short type in BF (46.1%), and CB (42.9%) and in normal type in BA (69.2%). Quiet ovulation was 38.5, 53.8 and 60% in BF, BA and CB, respectively, being similar in cold (52.4%) and hot (51.1%). Pg concentration showed different trends during different types of ovulatory cycles for all cow groups and during cold and hot. Only about 20% of BF showed postpartum anoestrus lasting for period of 33.5 days with average Pg concentration of 4.8 ng/ml, observing only in hot. Incidence of persistent corpus luteum (CL) was 40, 30 and 10% in CB, BA and BF. Average Pg was 45.2 vs. 21.1 and 20.5 ng/ml, respectively, and maximum Pg (64.4 vs. 40.0 and 43.2 ng/ml) was higher in BF than BA and CB, respectively. The main frequent oestrous symptom was bellowing in BF (95.0%), sniffing to other female (95%) in BA and mucus discharge (85%) in CB. All BF and BA cows versus 90% of CB exhibited oestrus. Number of oestrus cases/animal was 1.6, 1.4 and 1.2 in BF, CB and BA, respectively. All cows showed oestrus during hot (100%) versus 92.3% of those in cold. Number of oestrus cases/animal was 1.53 in cold and 1.29 in hot. Postpartum first oestrus/service interval tended to be longer in BF (61.3 d) and CB (59.9 d) than in BA (47.7 d), being nearly similar in cold (56.7 d) and hot (55.9 d). Service period (SP) was shorter and number of services /conception (NS/C) was lower in BA (3.8 d and 1.14 S/C) than in BF (15.1 d and 1.42 S/C) and CB (11.7 d and 1.41 S/C), but the differences were not significant. Average SP was shorter and NS/C was less in hot (6.5 d and 1.19 S/C) than in cold (13.8 d and 1.47 S/C), but this difference was not significant. Days open (DO) was shorter (P<0.05) in BA than in CB and BF (51.5 vs. 71.6 and 74.4 days, respectively). DO was insignificantly shorter in hot than in cold (63.4 and 68.3 days, respectively). Average length of calving interval (CI) was (P<0.05) the longest (386.6 d) in BF, followed by CB (351.1 d), while BA showed the shortest CI (336.5 d). Average CI was nearly similar in hot and cold seasons (349.2 and 353.2 d. respectively). Mean of herd pregnancy rate (PR) within 60 days postpartum was higher (P<0.05) for BA (92.3%) than BF and CB (39.3 and 30.8%, respectively), increased to be 100% in BA within 90 d-postpartum, and 89.3 and 92.3% in BF and CB within 120 day-postpartum. PR tended to be higher during hot than cold, being 96.2 and 89.3%, respectively. The current study may conclude that Baladi cows (Egyptian local breed) showed the best reproductive performance as compared to Egyptian buffalo and crossbred (Friesian x Baladi) cows.