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The aim of the study was to evaluate the influence of the milk yield of a milk cow on the length of its calving interval. The studies were carried out on 104 crossbred cows (Black-and White x HF). On the basis of the breeding data the length of calving interval (OMC) as well as the insemination index, number of milking days and the milk yield of consecutive lactations, were analyzed. Only cows having at least three consecutive lactations were studied. Milk yield data were divided into three groups: lower than 5000 kg of milk per lactation, between 5000 to 7000 kg and more than 7000 kg per lactation. The results indicate the significant influence of the milk yield and the consecutive lactation period on the length of OMC. It was noted that the greater milk yield observed the longer the interval of OMC was. Some reproductive traits that were mentioned before were not as satisfactory as we expected them to be for the studied herd. We assume that other factors like insemination failure can influence the length of OMC and milk yield, which is indicated by the high value of the insemination index.
This study examined the effect of the body condition of Polish Holstein-Friesian cows in the last month before calving and in the first week of lactation and of the rate of the body condition loss in the early lactation on basic fertility indicators. Body condition of a total 327 cows was evaluated using the 5-point BCS scale. Five fertility indices were included. The fertility indicators analysed depended less on the BCS of cows in the last month before calving and in the first week of lactation, and more on the size of body condition loss and its duration. Scores of over 3.5 both before parturition and at the start of lactation were associated with the longest service periods and with the lowest percentage of conceptions after one insemination procedure. The length of the days open and calving intervals and the number of services per conception increased as the length of the decline in BCS after parturition increased. The most favourable values for the fertility indicators analysed can be expected in cows whose BCS before parturition and at the start of lactation was 2.75-3.5. A smaller energy deficit with a shorter duration after parturition was also more favourable for these traits.
The analysis concerned 543 intercalving and interpregnancy periods and insemination indices in Lowland Black and White cows utilized between 1973-1980 in seven breeding farms situated in various distances from the copper mill in Głogów. On the basis of pollution maps the breeding farms were divided into 3 zones depending on intensity of emission. The aim of the investigations was to find out whether any differences existed between some chosen indices of fertility in cows kept in an environment polluted with heavy metals. Regardless of the distance of the areas where the cows were utilized from the emission source the fertility indices exceeded the values generally accepted as optimal.
The data of 234 lactations In 111 bw cows, 217 lactations in 118 crossbred /50% HF/ cows and 275 lactations in 135 crossbred half-blood Swedish-freslan cows were studied. The cows were used in three herds of high productivity /average yield in bw primlgravida during 305 day lactation period reached 390 kg/ in south-west Poland. Statistically significant differences in milk production traits were shown only between F₁ crossbred /HF x bw/ and their bw contemporaries /SF x bw/. The differences between crossbred /HF x bw/ and /SF x bw/ proved to be statistically insignificant. Milk yield of F₁ crossbred /SF x bw/ was higher by 13,6% in the first lactation and by 8,8% in further lactations compered to the yield obtained from bw contemporaries. The differences in fat and FCM milk yield were similar. However, no significant differences in fertility indices were found in the population of the cows studied.
W badaniach przeprowadzonych na 40 krowach rasy cb, w 2 grupach żywieniowych, określono wpływ stosowania marchwi czerwonej jako źródła β-karotenu. W żywieniu krów grupy doświadczalnej (II) zastosowano dawkę wzbogaconą w β-karoten, w wyniku wprowadzenia do niej dodatku marchwi. Całkowita ilość β-karotenu w przeliczeniu na 100 kg masy ciała w grupie doświadczalnej (II) wynosiła 80 mg, a w grupie kontrolnej (I) bez udziału marchwi w dawce - 40 mg. Nie stwierdzono istotnego wpływu stosowanego żywienia na wydajność mleka w początkowym okresie laktacji (I - 13,4; II — 14,6 kg). Stwierdzono korzystny wpływ marchwi na wskaźniki rozrodczości krów. Indeks inseminacji w grupie doświadczalnej (II) wynosił 1,5, a w kontrolnej (I) 1,9. Okres międzyciążowy u krów w obu grupach kształtował się odpowiednio: 74 (II) i 111 (I) dni. Zawartość β-karotenu w osoczu krwi krów w grupie II wynosiła od 9,3 do 10,6 μmol, a w grupie I była niższa i wynosiła od 6,8 do 7,0 μmol. Nie stwierdzono wyraźnych różnic w zawartości witaminy A w osoczu krwi. Masa ciała cieląt pochodzących od krów z obu analizowanych grup była w okresie odchowu podobna.
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