Time-course Changes in the Relationship between Serum and Milk β-carotene Concentrations in Mid-lactation Dairy Cows following a Shift from Drylot Feeding to Time-limited Grazing

JARQ : Japan Agricultural Research Quarterly
ISSN 00213551
書誌レコードID(総合目録DB) AA0068709X
本文フルテキスト
Grazing cows ingest large quantities of β-carotene (BC) from fresh pasture. The absorbed BC is carried to the mammary glands by the bloodstream and is subsequently transferred to the milk. This study was undertaken to assess the time-course changes in the relationship between serum and milk BC concentrations by calculating the rate of serum and milk BC concentration increase and estimating the mammary transfer of BC efficiency rate in mid-lactation dairy cows following a shift from drylot to time-limited grazing. For the first experiment, dairy cows were allocated to two treatment groups (each n = 3). The experimental grazing durations were 4 h (4hG) or 7 h (7hG) daily for 3 weeks. The serum BC concentration in the 7hG group was higher than that in the 4hG group. Nevertheless, no difference in milk BC concentration was found between the 4hG and 7hG groups. To investigate whether a difference exists in the rate of serum and milk BC increase in cows with time-limited grazing of more than 7 h daily, we conducted a second experiment for which the designated grazing time was 8 h daily for 4 weeks (n = 8). The rate of serum BC increase was greater than that of milk BC during days 14 to 28 of grazing. During the first 3 weeks of grazing, the estimated mammary extraction rate of BC significantly decreased, and the values at days 14 and 21 were significantly lower than those in drylot-feeding cows. These results suggest that the serum BC concentration strongly reflects the daily grazing time; however, the change in milk BC concentration is apparently delayed compared with that in the serum in cows grazing more than 7 h daily, and the relationship between the serum and milk BC concentrations changes following a shift from drylot feeding to time-limited grazing.
刊行年月日
作成者 Satoshi HAGA Kazuhiro MATOBA Hiroshi ISHIZAKI Yasuko TOGAMURA Yasuko UEDA Yoshihiro KARIYA
著者キーワード carotenoid extraction rate mammary gland transfer rate of increase
公開者 Japan International Research Center for Agricultural Sciences
受付日 2018-10-10
受理日 2019-01-08
53
3
開始ページ 215
終了ページ 222
DOI 10.6090/jarq.53.215
言語 eng

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