الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 106 |  |  |
| | | from | 106 | | |
Abstract
The experimental work of this study was carried out at El-Tonsy (International Company for Animal Wealth) dairy cattle farm from July 2014 to June 2015 under the supervision of Animal production department staff, Faculty of Agriculture, Benha UniversityThe aim of this study is to investigate the effect of different dry periods, draying off methods and parity number on the daily and total milk yield, its components as well as blood plasma parameters of imported Holstein Friesian cows in the delta of Egypt.In this study 27Holstein-Friesian cows in different paraties and stage of lactation were divided into three groups (each group contained 9 cows);the first group dried by sudden stop method, and contained cows below 10 Kg milk/day, the second group dried by irregular milking method, and contained cows between 11-20 Kg milk/day and the third group dried by incomplete milking method, and contained cows exceed over 20 Kg milk/day which can be illustrated as the following:1. Sudden stop drying off method: at the last week of lactation cows fed on low production concentrate mixture before sudden stop milking method till drying.
2. Irregular milking drying off method: at the last week of lactation cows milked once per day till drying.
3. Incomplete milking drying off method: at the last week of lactation cows milked incompletely till drying.
After the end of milking season, cow’s teats were injected by antimicrobial (dry cow therapy) and wax material to protect the udder from invading bacteria during the dry period.
All previous mentioned methods were applied according to Wayne et al., (1933).
Total milk production for all cows of the herd (N=620) and average daily milk yield during ten months of lactation for all experimental cows (N=27) were recorded. Milk samples and blood samples were taken from all experimental cows every 100 days during lactation season to analyze some milk (moisture, total solids, fat, solids not fat, protein, lactose and ash%) and blood (total protein, albumin, globulin, A/G ratio, triglyceride, total cholesterol, calcium, Potassium and magnesium) components.
The results obtained in this study can be summarized as follows:
1. Effect of dry period length:
- The differences among means of herd cow’s milk yield due to dry period effect (experimental 1) were highly significant (P<0.001). Cows that dried at 61-119 days before calving had the highest total milk yield (8465.77 Kg) followed by cows that dried at 46-60 days (8336.73 Kg), cows that dried at ≥45 days (7836.97 Kg) and cows that dried at 120 days (7693.50Kg).- Experimental Cows that dried at 60 days had higher average daily milk yield than cows dried at 60 days in the next lactation.- Cows that dried at >60 days had higher milk components (total solids, fat and protein%) than cows dried at60 days in the next lactation.While in conterary, Cows with short dry period at (60 days) had higher blood plasma total protein and cholesterol than cows with long dry period at (<60 days) in the next lactation. 2 - Drying off methods effect on experimental cows:
- Cows that dried by incomplete milking method had the highest total milk yield (10889.85 Kg) than that dried by irregular milking method (10187.45 Kg) or sudden stop (9786.01 Kg) and the same trend was observed for average daily milk yield during ten months of lactation except at 8th and 9th month. The differences between means of experimental cow’s milk yield, due to drying method effect, were non-significant except at average daily milk yield at 2nd month of lactation (P<0.05). - Cows that dried by incomplete milking method had the highest milk components (total solids, fat, solids not fat, protein and lactose %) than cows dried by other methods but, for water%, cows that dried by sudden stop milking method had the highest value (88.26%) followed by Irregular milking method (87.91%) and incomplete milking method (87.48%).The differences, were highly significant (P<0.001) for all studied milk components except for ash%.- Experimental cows blood plasma parameters (total protein, globulin, albumin, A/G ratio, triglyceride, cholesterol, calcium, potassium and magnesium) in the three drying off methods were almost the same value. And differences between means of them were not significant. 3- Effect of Parity number: - In the herd (experiment 1), it was found that fifth or more parity cows had the lower total milk yield (7082.10 Kg) than that at second (8987.05 Kg), fourth (8208.30 Kg) and third (8055.51 Kg) parities and the differences among these means were highly significant (P<0.001). - In the experimental cows, it was found that second parity cows had lower total milk yield (8336.90 Kg) than that at fourth or more (12801.16 Kg) and third (9725.25 Kg) parities. The differences between means of experimental cow’s milk yield (Kg) and lactation length (days), due to parity effect, were non-significant.- Experimental Cows at fourth or more parity had the highest milk components (total solids, fat, solids not fat and protein%) than cows at second and third parity, respectively, except for water% cows at second parity had the highest value (88.30%) followed by cows at third parity (87.83%) and cows at fourth or more parity (87.52%). The differences between means of experimental cow’s milk components, were highly significant (P<0.001) for all milk components except for lactose and ash% .- Fourth or more parity experimental cows had the highest means of Albumin, A/ G ratio, cholesterol, calcium, potassium and magnesium in blood plasma while, second parity cows had the lowest means in all studied blood plasma parameters. Generally differences between means of experimental cow’s studied blood plasma parameters were significant and( ranged from P<0.05 to P<0.01). 4- Stage of lactation effect on milk components and blood plasma parameters of experimental cows:Cows at third stage of lactation (last 100 days) had significantly (P<0.001) highest values of studied milk components (total solids, fat, solids not fat, protein, lactose and ash%) than cows at other stages of lactation (first and second 100 days), except, for water% where, cows at first stage of lactation had the highest value (88.43%) followed by cows at second stage of lactation (87.72%) and cows at third stage of lactation (87.44%). Cows in the third stage of lactation (last 100 days) had significantly highest values of total protein, globulin and albumin than cows in other stages of lactation and cows in the first stage of lactation (first 100 days) had lower values in the same blood plasma components, while other stages had intermediate results. The differences among these means were significant and ranged from P<0.05 to P<0.01.
5-Linear regressions of experimental cow’s milk yield on studied factors:
The linear regression coefficients of experimental cow’s milk yield and lactation length on each of dry period, cows weight at dry period, cows weight at parturition and cows weight after 50 days of lactation were not significant, except for regression coefficients of daily milk yield at fourth month of lactation on cows weight at parturition (P<0.05) and regression coefficients of daily milk yield at third, fourth and fifth months of lactation on cows weight after 50 days of lactation (ranged from