Effect of lactation stage and breed on the concentration of unsaturated fatty acids in milkfat of New Zealand dairy cattle
David Silva-VillacortaN. López‐VillalobosBlair HtHickson ReSpelman RjJanine MelisDavis DavisBerry SdkKlaus LehnertSnell Rg
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Milkfat composition influences the nutritional value and manufacturing characteristics of milk. This research studied the influence of: 1) stage of lactation on the concentration of unsaturated fatty acids (UFA) in milkfat of Holstein-Friesian, Jersey and Crossbred cows, 2) segregation of cows according to their UFA concentration in milkfat. The concentration of UFA in milkfat was predicted with a calibration equation using Fourier transform infrared spectroscopy. The data (21,757 test-day records) were analysed using a mixed model with a third-order orthogonal polynomial. In the three breeds studied, after early lactation the concentration of UFA in milkfat decreased steadily as the lactation progressed, but in Holstein-Friesian cows it increased slightly at the end of lactation. Throughout lactation, Holstein-Friesian cows produced milkfat with a higher concentration of UFA than Jersey and Crossbred cows. In each herd, cows were split into a high and a low group according to the average UFA concentration of the herd. The high UFA group had higher (P <0.001) milk yield, but lower (P <0.001) yields and concentrations of fat and protein than the low UFA group. This study indicates that concentration of UFA in milkfat is affected by breed and stage of lactation in New Zealand dairy cattle.Keywords:
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Summary Milk and butterfat yields, and the properties of butterfats from the milks, were compared in three successive years for early- and late-calving cows of monozygotic twin pairs grazed on the same pastures, over the period when both cows of the twin pairs were in lactation. The seasonal fluctuations in the properties of the butterfat were closely similar for the two groups of cows in all three trials. This was taken to indicate that the known regular pattern of seasonal change in the properties of New Zealand butterfat over all North Island districts is not due to change in stage of lactation of the cows but is probably the result of a regular change in the feeding conditions. The average milk and butterfat yields were lower for the early-calving cows during the comparison period, the iodine values were higher, and the Reichert and saponification values were lower. The early-calving cows were uniformly heavier than the late-calving cows. It is suggested that the consistent differences in the butterfat characteristics over the whole comparison period could be due to differences in the extent to which body fat reserves were drawn upon by the cows for maintenance of lactation. The average carotene and vitamin A contents of the butterfats were not appreciably different for the two groups of cows, indicating that these values are not directly related to stage of lactation of the cows or to yield of milk or butterfat.
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The objective of the study was to assess the influence of lactation number, daily milk yield, somatic cell count and milk composition on the freezing point of milk of Polish Holstein-Friesian cows. The data comprised 3,067,343 test day milk samples collected in 2014 from 865,198 first seven lactations of 714,018 Polish Holstein-Friesian cows, made available by the Polish Federation of Cattle Breeders and Dairy Farmers. The cows calved in 20,043 herds in 2013 and 2014. Four lactation classes were created: first, second, third, and fourth to seventh (4 class). Analysis of variance using the MIXED procedure in SAS was applied to milk freezing point (MFP). The following factors were included in the analysis: lactation class, daily milk yield (16 kg, 16.1–24 kg, >24 kg), fat content (<3.6%, 3.6–4.4%, >4.4%), protein content (<3.1%, 3.1–3.5%, >3.5%), urea content (150 mg·L-1, 151–269 mg·L-1, 270 mg·L-1), lactose content (<4.75%, 4.75–5%, >5%), somatic cell count (<400,000, 400,000) and dry matter in milk (12.5%, 12.6–13.4% and 13.5%), with interactions between lactation and each of the factors mentioned above. MFP decreased with increasing daily milk yield, protein, urea, lactose content and dry matter content, while MFP slightly increased with increasing fat content and somatic cell count. The differences in means of MFP between daily milk yield classes, fat, protein, urea and lactose content, dry matter and somatic cell count were highly significant (P<0.001).
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This research was conducted to determine the characteristics of milk yield of Holstein Friesian cows raised at Kocas state farm in Central Anatolia. The material of the research was 970 lactation records of 362 dairy cows raised from 1988 to 1995 at Kocas state farm. Statistical analysis of the records was conducted with the Minitab version 9.2 computer program. Significant differences between groups were determined by the method of Least Significant Difference (LSD). The general mean values of lactation length, lactation milk yield and 305 day milk yield were respectively 304.4±1.39 days, 4966±32.96 kg and 4784± 27.35.
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The study aimed to determine factors affecting the dry period length and effect of dry days on milk yield, milk composition and lactation length in the next lactation of dairy cows. Data used for analysis included 7264 lactation records collected from 2012 to 2016 on 4737 Holstein cows raised in 152 herds. The statistical model used to determine the factors influencing the dry period length showed that multiparous cows had a dry period 3.7 days longer than primiparous cows, and cows that calved from October to February had a dry period 2.5 days shorter than that of cows calved from March to September. The mixed model used to evaluate the influence of dry period on milk yield, milk composition and lactation length showed that the dry period influenced significantly milk yield and composition in the next 305 d lactation, but not the lactation length (P>0.05). Milk, fat and protein yields in the subsequent lactation were maximized with a 41 to 60-d dry period, whereas dry periods less than 20 d result in very pronounced losses in subsequent lactation yield. Fat and protein percentages were highest with the dry period classes greater than 80-d and less or equal than 20 d, respectively. The interaction between parity and dry length period was not significant (P>0.05) for any studied trait, indicating that dry days effects on milk yield and composition were consistent across lactations. It was concluded that dry period of 40 to 80 dry days does provide maximal performance in Holstein cows.
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In this study milk samples from Holstein Friesian cows were collected and analyzed during the first and second lactation period in a period of six months. The following parameters have been examined: protein content, fat content, lactose, and dry matter in milk. The average values of the content of milk protein, fat, lactose and dry matter in the milk of first lactation were as following: 3,14%, 3,25%, 4,46 %, 11,48% and in the milk of second lactation are: 3,21%, 3,29%, 4,39% and 11,68%.%. Milk from cows in the second lactation had a higher concentration of protein, more fat and dry matter than cow's milk from the first lactation. Keywords: quality, chemical composition, milk, lactation, breeds.
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