Harrison Taylor D, Chaney Elizabeth M, Brandt Kiernan J, Ault-Seay Taylor B, Schneider Liesel G, Strickland Lew G, Schrick F Neal, McLean Kyle J
Department of Animal Science, University of Tennessee, Institute of Agriculture, Knoxville, TN 37996, USA.
Transl Anim Sci. 2022 Jan 9;6(1):txac001. doi: 10.1093/tas/txac001. eCollection 2022 Jan.
Bulls often experience various levels of nutrient availability throughout the year. Nutritional management is a critical factor on overall ejaculate composition and the ability to get females pregnant. We hypothesized that differing nutritional levels and body condition score (BCS) affect reproductive fertility parameters in bulls. Mature Angus bulls ( = 11) were individually housed and randomly assigned to one of two dietary regimens: 1) over-fed ( = 5) or 2) restricted ( = 6). Bulls were fed the same ration at different volumes to achieve desired effects resulting in eight individual treatments: gain to an over-fed body condition score ([BCS]; GO), gain after nutrient restriction (GR), loss after an over-fed BCS (LO), loss from nutrient restriction (LR), maintenance at ideal adiposity (BCS = 6) after overfeeding (IMO), maintenance at ideal adiposity after nutrient restriction (IMR), maintenance at an over-fed BCS (BCS = 8; MO), and maintenance at a restricted BCS (BCS = 4; MR). Body weight (BW) and BCS were recorded every 2 wk to monitor bull weight and BCS changes. Scrotal circumference was measured every 28 d. Body fat and sperm motility and morphology were evaluated every 84 d. Scrotal circumference, motility, and morphology were normalized to the initial value of each bull. Thus, allowing the individual bull to serve as a control. Statistical analyses were conducted with PROC GLIMMIX of SAS as a complete randomized design to determine if treatment influenced BW, BCS, scrotal circumference, motility, morphology, and adipose thickness. Scrotal circumference ( < 0.001) had the least amount of deviation from initial during the LR (0.29 ± 0.44) treatment and the greatest during the MO (3.06 ± 0.44), LO (2.28 ± 0.44), MR (2.43 ± 0.44), GR (3.03 ± 0.44), and IMR (2.91 ± 0.44) treatments. Sperm motility was not affected by nutritional treatments ( = 0.55). Both head and total defects of sperm differed ( = 0.02) due to nutritional treatments. Increased head abnormalities occurred during the LO (37.60 ± 8.61) treatment, with no differences between the other treatments. Total defects increased during the LO (43.80 ± 9.55) treatment with similar increases in bulls during the GR (29.40 ± 9.55) and IMR (35.60 ± 9.55) treatments. In conclusion, male fertility was impacted when a deviation from a BCS of 6 occurred which could be detrimental to reproductive and beef production efficiency.
公牛全年经常会经历不同水平的营养供应。营养管理是影响精液整体成分以及使母牛受孕能力的关键因素。我们假设不同的营养水平和体况评分（BCS）会影响公牛的繁殖生育参数。11头成年安格斯公牛被单独圈养，并随机分配到两种饮食方案之一：1）过度饲喂（n = 5）或2）限制饲喂（n = 6）。给公牛饲喂相同的日粮，但量不同以达到预期效果，从而产生8种个体处理方式：增重至过度饲喂体况评分（[BCS]；GO）、营养限制后增重（GR）、过度饲喂BCS后减重（LO）、营养限制导致的减重（LR）、过度饲喂后维持理想肥胖度（BCS = 6；IMO）、营养限制后维持理想肥胖度（IMR）、维持过度饲喂BCS（BCS = 8；MO）以及维持限制饲喂BCS（BCS = 4；MR）。每2周记录一次体重（BW）和BCS，以监测公牛体重和BCS的变化。每28天测量一次阴囊周长。每84天评估一次体脂、精子活力和形态。阴囊周长、活力和形态均以每头公牛的初始值进行标准化。因此，使每头公牛可作为对照。使用SAS的PROC GLIMMIX进行统计分析，作为完全随机设计，以确定处理方式是否影响BW、BCS、阴囊周长、活力、形态和脂肪厚度。在LR（0.29±0.44）处理期间，阴囊周长与初始值的偏差最小（P < 0.001），而在MO（3.06±0.44）、LO（2.28±0.44）、MR（2.43±0.44）、GR（3.03±0.44）和IMR（2.91±0.44）处理期间偏差最大。营养处理对精子活力没有影响（P = 0.55）。由于营养处理，精子头部和总缺陷存在差异（P = 0.02）。在LO（37.60±8.61）处理期间，头部异常增加，其他处理之间无差异。在LO（43.80±9.55）处理期间，总缺陷增加，GR（29.40±9.55）和IMR（35.60±9.55）处理的公牛也有类似增加。总之，当BCS偏离6时，雄性生育能力会受到影响，这可能对繁殖和牛肉生产效率不利。
