الفهرس 
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Abstract
The trials of this study were carried out in four dairy herds under our local Egyptian conditions. Animals under study were within the productive age (2 to 10 years) during the period between November 2009 to May 2012.
The present study aimed at application of seven trials to improve the productive and reproductive efficiency of animals under Egyptian conditions.
1-Supplementation of the diet of lactating dairy cows with S. cerevisiae yeast culture.
2-Estimating the effect of low negative DCAD close up prepartum diets (-5 and -35 mEq/Kg DM) on peripartum health conditions as well as its effect on postpartum performance of dairy cows.
3-Drenching of PG to low BCS postpartum dairy cows to improve their BCS and reproductivity.
4- Evaluating factors affecting on walking activity increase at estrus and subsequent conception in Holstein cows using the new pedometer system (AFIKIM).
5- Shortening the length of the dry period in an attempt to enhance reproductivity.
6-Estimating the effect of two TAI protocols (Ovsynch and Doublesynch) versus heat detection on fertility of dairy cows.
In the first trial, S. cerevisiae supplementation to early lactation dairy cows improved their postpartum body condition status as indicated by significantly higher BCS on day 60 postpartum (3.36±0.047), compared to 2.75±0.099 for control cows. Treated and control cows were in NEB postpartum but supplemented cows lost fewer (-0.69 vs. -0.97, respectively).
Yeast supplementation was associated with higher percentage of cyclic cows by 60 days postpartum (44.44 vs. 12.5%), shorter days to first estrus (54±3.79 vs. 74±4.12 days), days to first insemination (62.68±2.22 vs. 75.6±3.71 days), higher average daily milk yield (29.36±0.58 vs. 27.44±0.56 Kg).
Concerning the milk composition, S. cerevisiae supplemented cows had lower SCC, MUN, milk lactose% and milk protein%; compared to control cows. However, milk fat% was higher in supplemented cows in comparison to control cows.
Blood glucose was significantly higher in treated cows (69.4±0.74 mg/dl), compared to 66.71±0.49 mg/dl in control cows. Meanwhile, serum TG level was non-significantly lower in treated cows versus controls (27.73±2.02 vs. 29.53±1.45 mg/dl, respectively).
Low negative DCAD close up prepartum diets were associated with lower incidence of metabolic and reproductive disorders in herds 2 and 3 as compared to positive DCAD diet in herd 1.
The present study revealed lower incidence of uterine inertia, uterine prolapse, RFM, endometritis, COD and milk fever in herds 2 and 3 where low negative DCAD diets were fed to prepartum cows, compared to herd 1 giving positive DCAD diet. Meanwhile, there was a higher rate of abortion in herds 2 and 3.
Cows in herds two and three produced more milk (20.92±3.12 and 27.63±4.31 Kg/day, respectively), compared to 17.97±2.6 Kg/day for cows in herd 1.
Low negative DCAD diets were associated with better reproductive performance (higher percentage of cyclic cows by 60 days postpartum, shorter days to first estrus, days to first insemination, days to conception, fewer inseminations per conception and higher FICR) in herds 2 and 3 in comparison with herd 1.
The current study revealed that drenching of PG to low BCS postpartum dairy cows for a period of 15 days had minor effects on their postpartum reproductive performance in spite of its beneficial effects on their postpartum BCS status.
Dairy cows managed to have a short or traditional dry period produced significantly lower daily milk (17.96±0.36 and 18.43±0.58 Kg, respectively), compared to 21.29±0.4 Kg for cows having longer dry period.
In the current work, the average BCS loss to minimum was 0.66±0.098, 0.75±0.088 and 1.33±0.086 for cows with short, traditional and long dry periods, respectively. Additionally, cows with short and traditional dry periods had better overall reproductive performance, compared to those with long dry periods. Meanwhile FICR was higher in cows with short dry periods.
The current work concerning pedometry revealed also that factors such as parity, number of animals simultaneously in estrus and milk production significantly influenced cow’s activity at estrus and modified subsequent conception. While, DIM at insemination did not have significant effects on activity at estrus. Higher milk production and lower parity were associated with increased conception regardless of activity increase at estrus.
As regards to the effect of TAI protocols versus heat detection on reproductive efficiency of dairy cows, the present work showed that days open were lowest (77.1±4.06 days) for cyclic cows inseminated upon heat detection and were highest in acyclic cows treated with Ovsynch protocol (120±7.7 days). There was no significant difference in the average NIPC between groups.
Heat detection cyclic cows had the highest FICR and overall CR (44 and 45.45%, respectively), while acyclic cows submitted to Ovsynch protocol had the poorest FICR and overall CR (25 and 18.86%, respectively).
Cyclic cows treated with the doublesynch protocol had comparable FICR and overall CR results (41.67 and 43.48%, respectively) to those of heat detection cyclic cows (44 and 45.45, respectively).