The pattern below comes from the Little Hen Rescue website in the UK. I've put a link to their site at the end of the pattern as I couldn't work out how to copy the images of hens wearing their warm woolly jerseys.
Pattern for Knitted Hen Jacket
Materials
Double knitting yarn (100g makes approximately 3 jumpers)
2 buttons or 10cm Velcro
1 pair of number 8 (4mm) knitting needles
4mm crochet hook
Knitted in stocking stitch with garter stitch borders
Cast on 41 sts,
Work 4 rows K
Increase for tabs;
Cast on 10 sts at beginning of next row, k14, p to last 4 sts, k4.
Cast on 10 sts at beginning of next row, k14, p to last 14sts, k14.
Work buttonholes; (work these 2 rows straight if using Velcro).
(K2 , yf k2tog) 3 times, work to end keeping edges in garter st.
Repeat this row for buttonholes on the other tab.
Cast off 10 sts at beginning of next row.
Next row – cast off 10 sts, k4, p2 tog, p to last 6 sts, p2tog, k4.
Dec 1 st at each end on every fol 6th row until 25 sts remain.
Divide for neck;
Work 11 sts, cast off 3, work to end – complete this half first.
1) k4, p to end
2) cast off 2, k to end
3) k4, p to end
4) k2tog, k to end
5) k4, p2tog, p to end
Work 4 rows straight
10) K to last 5 sts, inc in next st, k4.
11) K4, p to last st, inc in next st.
12) Cast on 2 sts, k to end, (11sts)
13) K4, p to end
14) K
Break yarn and rejoin to the other side of neck.
Work to match, reversing shaping’s and ending at winghole edge.
Next row – k, cast on 3, k across sts from other side of neck.
Next row , k4 inc in next st, p to last 5 sts, inc in next st, k4.
Inc 1 st at each end of every fol 6th row until there are 41 sts on the needle.
Work 6 rows straight.
Change to gst and knit 4 rows.
Cast off.
Sew on buttons or Velcro as desired.
Work double crochet around neck.
