Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad 9177948974, Iran.
AgResearch Ltd., Grasslands Research Centre, Private Bag 11008, Palmerston North 4474, New Zealand.
J Dairy Sci. 2020 Oct;103(10):8910-8921. doi: 10.3168/jds.2020-18345. Epub 2020 Jul 23.
This study evaluated the effects of conditioner retention time during the pelleting process of starter feed on intake, nutrient digestibility, ruminal fermentation, blood metabolites, and growth performance of dairy calves. A total of 30 Holstein female dairy calves [40 ± 1.93 kg of body weight (BW)] were randomly assigned to 1 of 3 treatments: (1) pelleted starter conditioned for 0 min (CON), (2) pelleted starter conditioned for 2 min, and (3) pelleted starter conditioned for 4 min. Three pelleted starter feeds had similar nutritional composition, and the starters were blended with 3% chopped wheat straw and fed to individually housed calves from d 3 to 70 of age. All calves were fed 4 L/d of pasteurized whole milk twice daily at 0800 and 1600 h from d 3 to 50 of calf age, followed by 2 L/d of morning feeding from 51 to 56 d of age. All calves were weaned on d 56 of age and remained in the study until d 70 of age. With the increase of conditioner retention time during pellet processing for 0, 2, and 4 min, the gelatinized starch content of pelleted starter feed linearly increased from 14, 30, and 45%, respectively. Additionally, the pellet durability and hardness also linearly increased with increasing conditioner retention time during pelleting. Feeding pelleted feed prepared using different conditioner retention time did not affect feed dry matter intake, metabolizable energy intake, weaning BW, final BW, or feed efficiency during the study. We observed no differences in the total-tract apparent digestibility of organic matter, neutral detergent fiber, and crude protein around weaning (d 49 to 56 of age) and after weaning (d 63 to 70 of calf cage); however, the digestibility of dry matter and starch after weaning was increased with increasing conditioner retention time during pelleting of starter feed. No difference was found in overall average daily gain (ADG) or growth rates of hip height, withers height, and heart girth. Ruminal volatile fatty acid profile was not affected by pelleting under different conditioner retention times. The ruminal ammonia concentration tended to be lower for calves fed the 4-min diet compared with those fed the CON diet during the postweaning period. The postweaning (d 57-70 of age) ADG was greater for calves fed the 4-min diet compared with those fed the CON diet. In conclusion, the conditioning time during the pelleting process of starter feed increased the gelatinization of starch, durability, and hardness of the pellets but did not influence feed intake, feed efficiency, and skeletal growth during the first 70 d of age. Increasing conditioning time during the pelleting process improved postweaning ADG; however, the final BW of calves was similar among treatments.
本研究评估了在犊牛开食料制粒过程中，调质时间对采食量、养分消化率、瘤胃发酵、血液代谢物和生长性能的影响。将 30 头荷斯坦雌性犊牛[40±1.93kg 体重（BW）]随机分为 3 种处理之一：（1）调质 0min 的制粒开食料（CON），（2）调质 2min 的制粒开食料，和（3）调质 4min 的制粒开食料。三种制粒开食料具有相似的营养成分，开食料与 3%切碎的小麦秸秆混合，从犊牛 3 日龄到 70 日龄单独饲养的犊牛。所有犊牛从 3 日龄到 50 日龄，每天两次饲喂 4L 巴氏消毒全奶，时间为 0800 和 1600h，从 51 日龄到 56 日龄，每天早上饲喂 2L。所有犊牛在 56 日龄断奶，并在 70 日龄断奶前留在研究中。随着制粒过程中调质时间从 0 增加到 2 和 4min，制粒开食料的糊化淀粉含量分别线性增加到 14%、30%和 45%。此外，随着制粒过程中调质时间的增加，颗粒的耐用性和硬度也呈线性增加。使用不同调质时间制备的颗粒饲料不会影响干物质采食量、可代谢能采食量、断奶 BW、最终 BW 或整个研究期间的饲料效率。在断奶（49-56 日龄）和断奶后（63-70 日龄），我们没有观察到总肠道有机物、中性洗涤纤维和粗蛋白的表观消化率有差异；然而，随着制粒开食料调质时间的增加，断奶后干物质和淀粉的消化率增加。在整个平均日增重（ADG）或臀部高度、肩高和胸围的生长速度方面没有差异。不同调质时间制粒不会影响瘤胃挥发性脂肪酸谱。与对照组相比，在断奶后阶段，饲喂 4min 日粮的犊牛瘤胃氨浓度有下降趋势。与对照组相比，在断奶后（57-70 日龄），饲喂 4min 日粮的犊牛 ADG 更高。总之，开食料制粒过程中的调质时间增加了淀粉的糊化程度、颗粒的耐用性和硬度，但在 70 日龄前的阶段不影响采食量、饲料效率和骨骼生长。增加制粒过程中的调质时间可以提高断奶后的 ADG；然而，犊牛的最终 BW 在处理之间相似。
