I still have my childhood copy of Christmas in the Country. It was garish when it was new. Now it is foxed and stained, but I read it every year. Maybe it's why I've always loved to imagine animals observing Christmas in the barn. For grown-ups, here is Thomas Hardy's lovely, wistful version of the idea:
The Oxen
Thomas Hardy
Christmas Eve, and twelve of the clock.
"Now they are all on their knees,"
An elder said as we sat in a flock
By the embers in hearthside ease.
We pictured the meek mild creatures where
They dwelt in their strawy pen,
Nor did it occur to one of us there
To doubt they were kneeling then.
So fair a fancy few would weave
In these years! Yet, I feel,
If someone said on Christmas Eve,
"Come; see the oxen kneel,
"In the lonely barton by yonder coomb
Our childhood used to know,"
I should go with him in the gloom,
Hoping it might be so.