Reproduction 1

摘要

Automated data collection systems were used to identify periods ofincreased activity at estrus and to assess factors affecting the magnitudeand duration of estrous activity. In total, 4,172 estrous periods in1,454 cows across 5 herds in Europe and Canada were studied. Eachherd used automated management systems manufactured by DeLaval(Tumba, Sweden) including a milk progesterone (MP4) measurementand analysis system (Herd Navigator), a body condition scoring system(BCS Camera) and an activity system (DelPro). A “heat alarm” (HA)was defined as 2 consecutive MP4 samples below 5 ng/mL following aluteal phase. Estrus was defined as an increase in activity within 7 d afterHA. Peaks in activity (estrus) were detected with an algorithm and themagnitude (fold change above baseline), duration, and area were determined.Cows were classified according to parity, month, BCS (≤2.75,2.75–3.0, 3.0–3.25, >3.25), days in milk (DIM; ≤56, 57–84, 85–140,and >140), and daily milk production (<40, 40–50, and >50 kg/d) at thetime of HA. Data were analyzed using a mixed model (PROC MIXED;SAS) with animal nested within herd defined as random. There was aneffect of herd (range: 65.7 to 78.7%; P < 0.001), month (range: 69.0%for May–Jun to 78.7% for Nov-Dec; P < 0.002) and BCS (range: 70.0%for ≤2.75 to 77.1% for >3.25; P < 0.004) on the percentage of cows withan activity peak after HA. Neither DIM, parity, nor milk affected peakdetection. For cows with an activity peak, the peak area was affected byherd (P < 0.001), DIM (P < 0.001), month (P < 0.001) and BCS (P <0.001). Differences in peak area were primarily associated with greaterpeak duration and not peak magnitude. Peak duration (h) differed forherds (range: 16.9 ± 0.3 to 19.2 ± 0.2; P < 0.001), DIM (range: 17.4 ±0.2 for ≤56 to 19.3 ± 0.3 for >140; P < 0.001), month (range: 17.3 ± 0.3for May–June to 19.1 ± 0.2 for Nov-Dec) and BCS (range: 17.6 ± 0.3for ≤2.75 to 18.9 ± 0.2 for >3.25; P < 0.001). Neither parity nor milkaffected peak area or duration. Conclusions were that estrous activity isaffected by herd, season (lowest in summer), BCS (lowest in low BCScows) and DIM (lowest in early lactation cows).