Smid Anne-Marieke C, Burnett Tracy A, Madureira Augusto M L, McLellan Kathryn J, Wegner Claire S, von Keyserlingk Marina A G, Weary Daniel M
Faculty of Land and Food Systems, Animal Welfare Program, The University of British Columbia, Vancouver, British Columbia, Canada.
Faculty of Veterinary Medicine, The University of Calgary, Calgary, Alberta, Canada.
PLoS One. 2024 Aug 8;19(8):e0308182. doi: 10.1371/journal.pone.0308182. eCollection 2024.
Dairy cows have a partial preference to access an outdoor deep-bedded pack, but the effects of continuous access to an outdoor area on estrous behaviors has not been studied. Our objective was to investigate if access to an outdoor open deep-bedded pack improves the expression of estrus behaviors. We enrolled 60 lactating Holstein cows directly after calving and followed them each for 12 weeks. Cows were housed in a single freestall pen holding 36 cows at a time, with a dynamic group composition. Half of the cows were randomly assigned to the OUTDOOR treatment; these cows had access to an outdoor open pack via an automated selection gate. INDOOR cows were housed together with OUTDOOR cows but were not allowed outdoor access. All cows were fitted with an automated activity monitor (AAM) 21 ± 3 d before expected calving date. Estrous behaviors (i.e., standing to be mounted and mounting behaviors) were continuously monitored using video, and the intensity of mounting (i.e., the number of standing to be mounted and other mounting behaviors per hour) was calculated per estrus event per cow. Temperature and humidity were monitored by data loggers indoors, and these data were used to calculate the Temperature Humidity Index (THI). Following an alert from the AAM, cows were checked to detect the presence of a dominant preovulatory follicle and an absence of a mature corpus luteum (CL) by rectal ultrasonography following milking, as well as 7 d thereafter to confirm ovulation by the presence of a new CL. A total of 94 estrus events were used in the final analysis. INDOOR cows tended to have a lower mounting intensity with increasing indoor THI, but no such effect was noted for OUTDOOR cows. The total number of cows in estrus positively influenced mounting intensity. OUTDOOR cows had a longer duration of estrus, as measured by the automated monitors, compared with INDOOR cows (12.4 ± 0.7 h versus 9.9 ± 0.8 h). Estrus event number and the total number of cows in estrus were both positively associated with estrus duration. These results indicate that access to an outdoor pack tended to increase mounting behavior for freestall housed dairy cows, especially during periods of elevated THI. We conclude that providing dairy cows access to an outdoor area can help with estrus detection and may thus help improve the reproductive programs on dairy farms.
奶牛对进入室外厚垫草畜舍有一定偏好，但持续进入室外区域对发情行为的影响尚未得到研究。我们的目的是调查进入室外开放式厚垫草畜舍是否能改善发情行为的表现。我们在产犊后直接招募了60头泌乳期荷斯坦奶牛，并对每头牛跟踪12周。奶牛被饲养在一个每次可容纳36头牛的单栏自由牛舍中，牛群组成动态变化。一半的奶牛被随机分配到室外处理组；这些奶牛可通过自动选择门进入室外开放式畜舍。室内组奶牛与室外组奶牛一起饲养，但不允许进入室外。所有奶牛在预计产犊日期前21±3天安装了自动活动监测器（AAM）。使用视频持续监测发情行为（即站立接受爬跨和爬跨行为），并计算每头奶牛每次发情事件的爬跨强度（即每小时站立接受爬跨和其他爬跨行为的次数）。室内通过数据记录器监测温度和湿度，这些数据用于计算温湿度指数（THI）。在AAM发出警报后，对奶牛进行检查，在挤奶后通过直肠超声检查以检测是否存在优势排卵前卵泡且无成熟黄体（CL），并在7天后再次检查以通过新CL的存在确认排卵。最终分析共使用了94次发情事件。随着室内THI升高，室内组奶牛的爬跨强度往往较低，但室外组奶牛未观察到这种影响。发情奶牛的总数对爬跨强度有正向影响。与室内组奶牛相比，通过自动监测器测量，室外组奶牛的发情持续时间更长（12.4±0.7小时对9.9±0.8小时）。发情事件数量和发情奶牛总数均与发情持续时间呈正相关。这些结果表明，进入室外畜舍往往会增加自由牛舍饲养奶牛的爬跨行为，尤其是在THI升高期间。我们得出结论，为奶牛提供进入室外区域的机会有助于发情检测，从而可能有助于改善奶牛场的繁殖计划。
