Looking at it further it seems that in the 19th & early 20th century it was common to refer to entire cart horses, and also entire horses:
On 10th April 1863 the following item appeared in the ‘Pembrokeshire Herald‘:
“…CARDIGAN. CARDIGAN AGRICULTURAL CLUB – The annual show of Stallions took place at Cardigan on Monday, the 6th inst., to compete for the prizes given by the Cardigan Agricultural Society, &c, when the prizes were awarded as follows:- The prize given by James Bevan Bowen, Esq. for the best entire thoroughbred horse was awarded to Hospodar, by Hetman Platoff: the prize given by the Society for the best entire cart horse was awarded to Young Nelson; the prize for the best entire horse calculated to get good active cobs was awarded to Trotting Rattler. The judges were J. W. Adams, Esq, Brynda, J. Griffiths, Esq, Treforgan, S. Parker, Esq, Stepaside, W. L. Wagner, Esq, Manorived…”