福岡県農業総合試験場研究報告

[摘要］福岡県内で乳用牛群検定を実施した2,993頭のデータを用いて、分娩後日数を説明変数とする五次回帰式泌乳曲線を作成し、北部九州における産次別および分娩季節別の特徴を明らかにした。産次別の泌乳曲線では、初産次は、最高日乳量および305日乳量が最も少なく、泌乳ピーク以降の乳量低下が最も緩やかであった。2産次は、初産次に比較して最高日乳量が120.9％，305日乳量が110.6％と大幅に増加し、泌乳ピーク以降の乳量低下が急であった。最高日乳量および305日乳量は、4産次が最も多く、その後の産次で漸減した。分娩季節別の泌乳曲線では、1～3月分娩は最高日乳量が他の分娩季節に比べて多く、泌乳ピーク以降の乳量低下が急であった。4～6月分娩は最高日乳量が少なく、泌乳ピーク以降の乳量低下が緩やかな傾向であった。このような泌乳曲線のパターンの違いは、305日乳量水準が9,000㎏以上の高泌乳牛において顕著であった。305日乳量に対する分娩季節の影響は、305日乳量水準が7,000kg台および8,000㎏台の乳牛においては極めて小さく，このことは、生産現場において普及している暑熱対策が一定の効果をもたらし、乳量低下が軽減された結果と考えられた。

　Influences of Parity and Calving Season on Lactation Curve described by a Multiple Regression Model in Northern Kyushu. KOGA Yasuhiro and Katuyuki YAMASHITA (Fukuoka Agricultural Research Center, Chikushino, Fukuoka 818-8549, Japan) Bull. Fukuoka Agric. Rec. Cent.. 18 : 101 - 105 (1999)

　The features of lactation curves in the different parity and calving season were investigated, using a multiple regression model based on 2,993 Holstein milk performance test records in Fukuoka. The peak daily milk yield and the 305-day milk yield calculated by the lactation curve formula in the second parity were 20.9% and 10.7%, respectively, higher than those in the first parity. The peak daily milk yield and the 305-day milk yield were highest in the forth parity. The persistency index of lactation in the first parity was highest, and that in the second parity was lowest. The peak daily milk yield in the case of calving in Jan.-Mar. was higher than that of calving in other month, and the daily milk yield after the peak fell more rapidly. The peak daily milk yield in the case of calving in Apr.-Jun. was lower than that of calving in other month, but the daily milk yield after the peak fell gradually. The influences of calving season on the peak daily milk yield and the persistency index of lactation were more pronounced in the dairy cattle with the capacity of 305-day milk yield level above 9,000kg than in those with the lower capacity.