Rodriguez-Venegas Rafael, Meza-Herrera Cesar Alberto, Robles-Trillo Pedro Antonio, Angel-Garcia Oscar, Legarreta-Gonzalez Martín Alfredo, Sánchez-Vocanegra Humberto Filemón, Rodriguez-Martinez Rafael
Programa de Doctorado en Ciencias Agropecuarias Unidad Laguna, Universidad Autónoma Agraria Antonio Narro, Torreón 27054, Coahuila, Mexico.
Unidad Regional Universitaria de Zonas Áridas, Universidad Autónoma Chapingo, Bermejillo 35230, Durango, Mexico.
Animals (Basel). 2023 May 22;13(10):1715. doi: 10.3390/ani13101715.
The possible effect of heat stress (HS), measured with the temperature-humidity index (THI) across seasons of the year (SY) upon milk production (MP), feed-to-milk efficiency (FME), and cow comfort (CC) was assessed in Holstein-Friesian cows in northern-arid Mexico. Data from 2467 cows (2146 milking and 321 dry) were recorded across SY [spring (SP), summer (SM), autumn (AT), and winter (WN)] between 2016 and 2019 in an intensive dairy farm located in the Comarca Lagunera (25° NL) with large fluctuations regarding ambient temperature and solar radiation. The THI was stratified into four classes: non-HS, <68; light HS, 68-71; moderate HS, 72-76; and intense HS, ≥77. The considered response variables were Milk production: both on a farm basis (totMP) and on a cow basis (cowMP); Nutritional efficiency: dry matter intake (DMI, kg); Feed conversion efficiency (FCE, kg) and energy-corrected milk (ECM, kg); Percentage of milking cows: (MC%); and Cow comfort: lying time (LT, h). Analyses of variance for unbalanced data were performed through "R". Both totMP and cowMP differed ( < 0.05) as HS increased; the largest values (i.e., 77,886 L and 35.9 L) occurred at lower THIs (i.e., <68 and 68-71) while the milk production fell (i.e., 66,584 L and 31.7 L) with the highest THIs (i.e., ≥77). Not only feed-to-milk efficiency (i.e., DMI, FCE, and ECM) but also the MC% exhibited a similar trend; a visible drop ( < 0.05) occurred from a THI of 68-71 onwards. Furthermore, the LT declined as the THI augmented, from 10.6 h at <68 to 8.5 h at ≥77. Moreover, differences ( < 0.05) also arose across seasons; TotMP, cowMP, DMI, FCE, and ECM revealed their largest ( < 0.05) values in WN and SP, halfway ones in AT, with the lowermost figures in SM. In the same way, cow comfort differed ( < 0.05) among seasons, with diverse lying times (h); WT, 10.5; AT, 10.20; SP, 9.3 h; and 8.8 in SM. Finally, the potential economic burden that HS caused at the producer (USD 233.2 million) and industry-market levels (USD 311.1 M), as well as its impact upon nutrient and alimentary security at the society level (i.e., 311 M milk liters and 195,415.82 Gcal), were also quantified.
在墨西哥北部干旱地区的荷斯坦 - 弗里生奶牛中，评估了利用温湿度指数（THI）衡量的热应激（HS）在一年不同季节（SY）对产奶量（MP）、饲料转化为牛奶的效率（FME）和奶牛舒适度（CC）的可能影响。2016年至2019年期间，在位于拉古内拉地区（北纬25°）的一个集约化奶牛场记录了2467头奶牛（2146头泌乳牛和321头干奶牛）的数据，该地区环境温度和太阳辐射波动较大。THI被分为四类：无热应激，<68；轻度热应激，68 - 71；中度热应激，72 - 76；重度热应激，≥77。所考虑的响应变量包括：产奶量：农场水平（总产奶量，totMP）和个体奶牛水平（个体产奶量，cowMP）；营养效率：干物质摄入量（DMI，千克）；饲料转化效率（FCE，千克）和能量校正奶量（ECM，千克）；泌乳奶牛百分比（MC%）；以及奶牛舒适度：躺卧时间（LT，小时）。通过“R”软件对不平衡数据进行方差分析。随着热应激增加，总产奶量和个体产奶量均有差异（P<0.05）；最高值（即77,886升和35.9升）出现在较低的THI水平（即<68和）68 - 71），而产奶量在最高THI水平（即≥77）时下降（即66,584升和31.7升）。不仅饲料转化为牛奶的效率（即DMI、FCE和ECM），而且MC%也呈现类似趋势；从THI为68 - 71开始出现明显下降（P<0.05）。此外，随着THI升高，躺卧时间减少，从<68时的10.6小时降至≥77时的8.5小时。此外，不同季节之间也存在差异（P<0.05）；总产奶量、个体产奶量、DMI、FCE和ECM在冬季和春季显示出最高值（P<0.05），秋季居中，夏季最低。同样，奶牛舒适度在不同季节也存在差异（P<0.05），躺卧时间不同（小时）；冬季为10.5小时；秋季为10.20小时；春季为9.3小时；夏季为8.8小时。最后，还量化了热应激给生产者造成的潜在经济负担（2.332亿美元）和行业 - 市场层面的负担（3.111亿美元），以及其对社会层面营养和粮食安全的影响（即3.11亿升牛奶和195,415.82千兆卡）。
