1Departamento de Bovinos, Facultad de Veterinaria,Instituto de Producción Animal Veterinaria,Universidad de la República, Ruta 1 km 42.500, 80100 San José,Uruguay.
2Programa de Posgrado, Facultad de Veterinaria,Universidad de la República, Lasplaces 1550, 11600 Montevideo,Uruguay.
Animal. 2019 Jun;13(6):1297-1303. doi: 10.1017/S1751731118002835. Epub 2018 Oct 23.
In intensive feeding systems, competition may be high and social dominance may affect animal performance by changing dry matter intake (DMI) and behavioral time budgets. If competition level is maintain over time, the strategies developed by heifers of different social status are expected to differ. Thus, the aim of this study was to compare individual DMI, intake rate and eating, ruminating, lying and standing behaviors in dominant (DOM) and subordinate (SUB) pre-pubertal dairy heifers in a model study implying continuous competitive situations. A total of 16 Holstein and Jersey×Holstein pre-pubertal heifers (251±10 days old, weighing 208±14 kg; mean±SEM) were allocated into eight homogeneous dyads. Each dyad was maintained during 120 days (day 0=beginning of measurements) in pens, and received a total mixed ration from one feeder/dyad. The DOM and SUB heifers was determined (day 0, twice during the first month of the experiment and every month afterwards) by observation of the winner in agonistic interactions in each dyad after the feed was supplied. The general activity pattern (eating, ruminating, lying and standing) of each heifer was recorded by direct instantaneous scan-sampling, every 10 min for 12 h, in 7 days (days 1, 21, 35, 60, 75, 100 and 120). Individual DMI was estimated with the double marker technique, in three intervals (I=days 17-26; II=days 78-87 and III=days 112-120), while estimated intake rate (kg/min) was calculated for each interval as the DMI per total eating time. After the experiment was concluded, data of the first 5 and the last 6 h of the 12 h scan-sampling (related to the moment the feed was supplied) was grouped according to the moments of greater and lesser competition for feed on each day. During the first 5 h, where competition was expected to be highest, no differences in eating behavior were found between heifers of different social status, but DOM heifers spent more time ruminating and lying than SUB heifers, while SUB spent more time standing than DOM heifers. No differences were found on DMI between DOM and SUB, but SUB ate at a faster rate on interval II compared with DOM heifers. In conclusion, in this model study of heifer dyads, SUB heifers had greater intake rate with no differences in feed intake, spent less time ruminating and lying, and more time standing than DOM heifers during the first hours after feed delivery.
在密集饲养系统中，竞争可能很激烈，社会优势地位可能通过改变干物质摄入量（DMI）和行为时间预算来影响动物表现。如果竞争水平随着时间的推移而保持不变，那么不同社会地位的小母牛所采用的策略预计会有所不同。因此，本研究的目的是比较主导（DOM）和从属（SUB）青春期前荷斯坦和泽西×荷斯坦小母牛在持续竞争情况下的个体 DMI、摄食率和采食、反刍、躺卧和站立行为。共有 16 头荷斯坦和泽西×荷斯坦青春期前小母牛（251±10 天龄，体重 208±14kg；均值±SEM）被分配到 8 个同质双元组中。每个双元组在围栏中饲养 120 天（测量开始之日=第 0 天），每个双元组从一个喂食器/双元组中接受全混合日粮。在每个双元组供应饲料后，通过观察每个双元组中在竞争互动中的获胜者，确定 DOM 和 SUB 小母牛（第 0 天，在实验开始后的第一个月内进行两次，之后每月一次）。每个小母牛的一般活动模式（采食、反刍、躺卧和站立）通过直接瞬时扫描采样，每 10 分钟记录一次，持续 12 小时，共 7 天（第 1、21、35、60、75、100 和 120 天）。使用双标记技术，在三个时间段（I=第 17-26 天；II=第 78-87 天和 III=第 112-120 天）估计个体 DMI，同时为每个时间段计算估计的摄食率（kg/min），方法是将 DMI 除以总采食时间。实验结束后，将 12 小时扫描采样的前 5 小时和最后 6 小时的数据（与饲料供应时刻相关）根据每天饲料竞争较大和较小的时刻进行分组。在前 5 小时，预计竞争最为激烈，不同社会地位的小母牛之间在采食行为上没有差异，但 DOM 小母牛反刍和躺卧的时间多于 SUB 小母牛，而 SUB 小母牛站立的时间多于 DOM 小母牛。在 DMI 方面，DOM 和 SUB 之间没有差异，但 SUB 小母牛在 II 期间的摄食率比 DOM 小母牛快。总之，在这项关于小母牛双元组的模型研究中，与 DOM 小母牛相比，SUB 小母牛在饲料供应后的最初几小时内的摄食率更高，采食量无差异，反刍和躺卧时间更少，站立时间更多。
