Modern milk production have come a long way when it comes to accommodating the
nutritional and physiological needs of the animals, but unfortunately the behavioural and
psychological needs of cows and heifers are often left unfulfilled. A long time for eating
is beneficial for the digestion and also gives the cattle something to do and decreases the risks for developing abnormal behaviours. An important factor that influences eating- and ruminating time is the particle size of the roughage. The aim of the study was to find out if particle size influences the behaviour of dairy heifers, in particular with regard to eating behaviour and abnormal behaviours.
The study was conducted at Uddetorp farm high school in Skara. Forty-two heifers of the
breeds SR and SF were housed in 8 slatted floor pens. Two separate roughage treatments
were tested; long silage (253.5 ± 39.6 (SD) mm) and short silage (25.6 ± 8.3 (SD) mm).
The silages were fed according to a change-over design with two experimental periods of
three weeks, with a week in between the periods when the heifers were fed both short and
long silage. The heifers also were fed both silages during one week before the trial
started, during which time a base registration of behaviours was conducted. Amounts of
concentrate were similar between treatment groups within the same live weight range.
During the last two weeks of each period all roughage was weighed before it was fed and
leftovers were collected and weighed. At the start and at the end of each period all heifers were weighed and scored for body condition. Behavioural recordings were conducted
during the last two days of each week of a period using video recordings around the clock
and direct observations for three sessions of two hours each per day. Behavioural data
from the video recordings and direct observations was analyzed using generalized linear
model (Proc Genmod) in SAS (Statistical Analysis Systems, version 9.1)
Results from the intake measurements showed that the younger heifers increased their DM intake in percentage of body weight and in kg per day when fed short silage compared to long silage. This difference in DM intake also could to a small extent depended on a higher dry-matter concentration but lower concentrations of ammonia and organic acids in the short compared to the long silage. However, the older heifers did not differ in DM intake between the two silages.
The behavioural analysis showed that the heifers spent significantly more time eating
when fed long compared with short silage (p<0.05, ?2 = 7.77, df = 2). The heifers spent
less time ruminating while lying down during base recordings than in either of the silage
treatments (p<0.05, ?2 = 6.84, df = 2). Between the two silage treatments however, there
was no difference in this behaviour. When the heifers were fed long silage, they spent
less time standing inactive (p<0.05, ?2 = 6.39, df = 2). The same result also was found in
the time the heifers spent lying inactive (p<0.05, ?2 = 7.11, df = 2). When fed short silage, the heifers spent significantly more time drinking water than when fed long silage
(p<0.05, ?2 = 5.82, df = 1). When fed long silage the time the heifers spent licking the
fixture decreased compared to when they were fed short silage (p<0.05, ?2 = 6.48, df = 2).
There also was an interaction between the particle size of the silage and the age of the
heifers when it came to time spent licking and biting on fixtures (p<0.05, ?2 = 3.99, df =1). The difference between the silage treatments was greater among the younger than the
older heifers in this behaviour. During base registration the heifers scratched themselves
more against the fixture compared to when they were fed either of the silages (p<0.05, ?2
= 6.16, df = 2). Looking at the time the heifers spent licking themselves there was an
interaction between the silage particle size and the age of the heifers (p<0.05, ?2 = 4.07, df = 1). The younger heifers sp...
