Madruga A, Mainau E, González L A, Rodríguez-Prado M, Ruíz de la Torre J L, Manteca X, Ferret A
J Anim Sci. 2017 Aug;95(8):3322-3330. doi: 10.2527/jas.2017.1608.
The objective of this experiment was to compare the effects of using 2 different forage sources on intake and sorting and feeding behavior in growing heifers fed a high-concentrate diet offered as a total mixed ration (TMR). Eight Simmental heifers (initial BW of 148.1 ± 4.83 kg) were used in a crossover design experiment. Treatment diets were a TMR with either barley straw (BS) or alfalfa hay (AH) as forage source. Diets were offered on an ad libitum basis, with a forage to concentrate ratio of 8 to 92. The experiment was performed in two 28-d periods, with 3 wk of diet adaptation and 1 wk of sampling in each period. Heifers were weighed before feeding on 2 consecutive days at the beginning and the end of the experiment, and in the sampling week. Feed and refusal samples were collected daily in the sampling week for DM determination and chemical analysis. Particle size separation was performed using the 3-screen Penn State Particle Separator. Dry matter digestibility was estimated using acid-insoluble ash as internal marker. Feeding behavior was recorded using an automated feeding system. Sorting behavior was measured with the intake of different particle size. Dry matter intake was greater ( < 0.05) in heifers fed BS (6.7 kg/d) than AH (5.8 kg/d) when these animals faced TMR for first time in period 1, but DMI did not differ between diets in period 2 when they were accustomed to the method of feeding. Apparent DM digestibility did not differ between diets (62.7 and 64.3% for BS and AH, respectively). Heifers fed BS sorted in both periods against long particle size ( < 0.01) and against medium particle size in period 2 ( < 0.01), a behavior that did not appear in heifers fed AH. Heifers sorted for short particle size in both diets in period 1, this behavior being maintained in period 2 for heifers fed BS, while it disappeared in heifers fed AH. This sorting behavior preferentially shown in heifers fed BS resulted in a tendency ( = 0.06) for greater length of each meal and a longer feeding time ( = 0.02). In conclusion, at 8% of incorporation, forage source affected intake in only 1 of the 2 experimental periods. Heifers fed BS showed a sorting behavior with preferential consumption for concentrate in the TMR, feeding time being greater in BS than in AH. In contrast, heifers fed AH sorted for short particle size when faced for the first time with a new method of feeding, this sorting behavior disappearing once heifers had got familiar with it.
本试验的目的是比较在以全混合日粮（TMR）形式提供高浓度日粮的生长小母牛中，使用两种不同饲料来源对采食量、分选和采食行为的影响。采用交叉设计试验，选用8头西门塔尔小母牛（初始体重148.1±4.83千克）。处理日粮是以大麦秸秆（BS）或苜蓿干草（AH）为饲料来源的TMR。日粮自由采食，饲料与精料比例为8:92。试验分两个28天周期进行，每个周期有3周的日粮适应期和1周的采样期。在试验开始和结束时以及采样周，连续两天在饲喂前对小母牛进行称重。在采样周每天收集饲料和剩料样本，用于测定干物质和化学分析。使用三层宾夕法尼亚州立颗粒分离器进行粒度分离。用酸不溶性灰分作为内标估计干物质消化率。使用自动饲喂系统记录采食行为。通过不同粒度的采食量测量分选行为。当这些动物在第1周期首次面对TMR时，采食BS的小母牛干物质采食量更高（P<0.05），为6.7千克/天，而采食AH的小母牛为5.8千克/天，但在第2周期当它们习惯了饲喂方法后，两种日粮的干物质采食量没有差异。两种日粮的表观干物质消化率没有差异（BS和AH分别为62.7%和64.3%）。采食BS的小母牛在两个周期都对长粒度（P<0.01）进行分选，在第2周期对中粒度也进行分选（P<0.01），采食AH的小母牛没有出现这种行为。在第1周期，两种日粮的小母牛都对短粒度进行分选，采食BS的小母牛在第2周期保持了这种行为，而采食AH的小母牛则消失了。采食BS的小母牛优先表现出的这种分选行为导致每餐时间更长（P=0.06）和采食时间更长（P=0.02）的趋势。总之，在掺入量为8%时，饲料来源仅在2个试验周期中的1个周期影响采食量。采食BS的小母牛表现出一种分选行为，在TMR中优先消耗精料，采食BS的小母牛的采食时间比采食AH的长。相反，采食AH的小母牛在首次面对新的饲喂方法时对短粒度进行分选，一旦熟悉了这种方法，这种分选行为就消失了。
