Abstract：
The impact of heat stress on dairy cattle leads to significant economic losses and a negative impact on the welfare of the animals. The objective of this research was to evaluate the effect of the nutritional additive (Thermoplus®) in dairy cows under postpartum heat stress conditions, and its effects on the metabolic profile, production and quality of milk. Eighteen lactating Holstein cows (8 multiparous and ten primiparous), in a free-stall system, with a mean body condition score (BCS) of 3.14 ± 0.05, live weight of 624.55 ± 18, 61 kg, with initial mean days in milk (DIM) of 90 ± 10.11, were selected. The animals were grouped into a control (CG, n = 9) and a treatment (TG, n = 9). Both groups underwent 14 days of diet adaptation, the TG received the basal diet supplemented with 50 g of the additive, once a day, individually, while the control group received only the total diet. Data collection of metabolic and productive parameters were evaluated on days -14 (before adaptation), 1 (after the diet adaptation period), 16, 30, and 44. Milk, blood, and body condition score (BCS) were collected once a day, and heart rate, respiratory rate, and rectal temperature were collected twice a day. Serum concentrations of albumin, calcium, magnesium, glucose, gamma-glutamyl transferase (GGT), beta-hydroxybutyrate (BHBA), non-esterified fatty acids (NEFAs), and paraoxonase-1 (PON-1) were evaluated. In the milk, the percentage of fat, protein, lactose, and total solids were determined in each sampling. Milk yield was measured daily. Humidity and ambient temperature values were collected on the days of the collection every 30 min, from 5:30 am to 5:00 pm, to calculate the temperature-humidity index (THI). Statistical analyzes were performed using the SAS software (version 9.3, SAS Institute Inc., Cary, NC, USA). The THI ranged from 62.22 to 79.47. Our findings showed that when the THI was greater than 72, the animals in the TG were able to maintain milk yield (Odds ratio (OD) = -0.0577,), and the animals in the CG had a greater chance of reducing it (OD = -0.2301). Multiparous cows in the TG had higher milk yield than CG (32.57 ± 0.34 vs 30.50 ± 0.36 kg per day; P = 0.0078) and lower SCC (34.110 ± 6,940 vs 665.50 ± 214.41 cells per ml; P = 0.03), with the same percentages of total solids (P > 0.05). In multiparous metabolic markers, TG when compared CG had higher albumin concentrations (2.50 ± 0.07 vs 2.12 ± 0.07 g/dl; < 0.001), equal PON-1 (P > 0.05), and higher BHBA levels (0.49 ± 0.03 vs 0.39 ± 0.04 mmol/l). Primiparous from the CG had higher concentrations of NEFA (0.18 ± 0.02 mmol/l) than multiparous from the same group (0.09 ± 0.02 mmol/l) P = 0.0265. The use of the plant polyphenol extract in postpartum Holstein cows challenged by heat stress had beneficial effects on the production and health of the mammary gland in multiparous cows without decreasing milk solids. The non-reduction of the activities of the acute phase proteins indicates an immunomodulatory and inflammatory-reducing effect of the product used.
摘要：
热应激对奶牛的影响会导致重大的经济损失，并对动物的福利产生负面影响。这项研究的目的是评估营养添加剂（Thermoplus®）在产后热应激条件下的奶牛的效果，以及它对新陈代谢的影响，牛奶的产量和质量。18头泌乳荷斯坦奶牛（8头多胎和10头初产），在自由失速系统中，平均身体状况评分（BCS）为3.14±0.05，活重为624.55±18，61kg，选择初始平均牛奶天数(DIM)为90±10.11。将动物分组为对照(CG，n=9)和处理(TG，n=9)。两组都接受了14天的饮食适应，TG接受补充了50克添加剂的基础饮食，一天一次,个别,而对照组只接受总饮食。在第-14天（适应前）评估代谢和生产参数的数据收集，1（饮食适应期后），16、30和44。牛奶,血,每天收集一次身体状况评分（BCS），和心率,呼吸频率,每天两次收集直肠温度。血清白蛋白浓度,钙，镁，葡萄糖，γ-谷氨酰转移酶（GGT），β-羟基丁酸酯（BHBA），非酯化脂肪酸（NEFA），对氧磷酶-1(PON-1)进行了评价。在牛奶中，脂肪的百分比，蛋白质，乳糖,和总固体在每个样品中测定。每天测量牛奶产量。每30分钟收集一次的湿度和环境温度值，从早上5:30到下午5:00，计算温度-湿度指数（THI）。使用SAS软件（9.3版，SASInstituteInc.，凯里,NC,美国）。THI的范围从62.22到79.47。我们的发现表明，当THI大于72时，TG中的动物能够保持产奶量（赔率比（OD）=-0.0577，），CG中的动物有更大的机会减少它（OD=-0.2301）。TG中的多胎奶牛的产奶量高于CG（32.57±0.34vs30.50±0.36kg/天；P=0.0078），SCC较低（34.110±6,940vs665.50±214.41细胞/ml；P=0.03），具有相同的总固体百分比(P>0.05)。在多胎代谢标志物中，与之相比，TG具有更高的白蛋白浓度（2.50±0.07vs2.12±0.07g/dl；<0.001），等于PON-1(P>0.05)，和更高的BHBA水平（0.49±0.03vs0.39±0.04mmol/l）。CG初生的NEFA浓度（0.18±0.02mmol/l）高于同组的经产（0.09±0.02mmol/l），P=0.0265。在受到热应激挑战的产后荷斯坦奶牛中使用植物多酚提取物对经产奶牛的乳腺的生产和健康具有有益的影响，而不会减少乳固体。急性期蛋白活性的不降低表明所用产品具有免疫调节和减少炎症的作用。
