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Of British-English origin, the colloquial imperative phrase cut the cackle (and come to the horses) means: stop talking (and get to the heart of the matter).
—Cf. cackle-cutting, derived from this phrase.

This phrase refers to the noun cackle, denoting the raucous clucking cry given by a hen, especially after laying an egg—hence also, figuratively, stupid loquacity, silly chatter.
—Cf. the noun cackleberry, designating a hen’s egg.

A variant of the phrase cut the cackle (and come to the horses) occurred, for example, in A rum do, this final touch for your big spread, by Sheila Hutchins, Express Cookery Editor, published in the Daily Express (London, England) of Friday 24^th December 1976 [page 4, column 6]:

Let us cut the cackle and come to the cooking.
A bit of quickly made pâté would be most useful at Christmas, either for starters or to make a little extra for the Boxing Day cold table.
This gorgeous chicken pâté is not only cheap but simple to make.

This is the origin of the phrase cut the cackle (and come to the horses), according to Albert Barrère and Charles Godfrey Leland in A Dictionary of Slang, Jargon & Cant. Embracing English, American, and Anglo-Indian Slang, Pidgin English, Tinkers’ Jargon and other irregular Phraseology (Edinburgh: The Ballantyne Press, 1889) [Vol. 1, page 216, column 1]:
—Note: The British circus performer Andrew Ducrow (1793-1842) was the originator of horsemanship acts, and proprietor of Astley’s Amphitheatre, a performance venue in London opened in 1773 by the British equestrian and circus owner Philip Astley (1742-1814):

Cackle (circus), the dialogue of a play. Some actors seek to derive this word from cacalogy [sic]. It is, however, far more likely to have been derived by the equestrian performers, who introduced and popularised it, from the more homely “cluck, cluck” of the humble barn-door fowl, after the process of laying an egg.
When manager of Astley’s, the great Ducrow, who shared the hatred which his craft has always more or less entertained towards the actor, was wont to apostrophise the performers in his equestrian drama after this fashion: “Come, I say, you mummers […] cut your cackle, and come to the ’osses!”

These are, in chronological order, the earliest occurrences of the phrase cut the cackle (and come to the horses) that I have found, in chronological order:

1-: From the column Our Representative Man, by ‘Your Representative’, published in Punch, or the London Charivari (London, England) of Saturday 28^th September 1878 [page 141]:

Miss Soldene is the right artiste in the right place. She fills the stage with her presence, and, what is still more important, she fills the house with her voice. Her singing voice I mean, not her speaking voice, but the talk is really objectless at the Alhambra, and Ducrow’s oft-quoted order to “cut the cackle and come to the ’osses,” applies directly here, when the sooner the cackle is cut, and the quicker we get to the music, singing, and dancing, the better the public are pleased, invariably.

2-: From Dramatic & Musical Gossip, by ‘Carados’, published in The Referee (London, England) of Sunday 28^th December 1884 [page 2, column 4]:
—Note: Astley’s Amphitheatre was renamed Sanger’s Amphitheatre after the British circus proprietor George Sanger (1825-1911) bought it in 1871:

Sanger’s Amphitheatre was twice on Boxing Day filled to its utmost holding capacity, and, judging from the satisfaction evinced by both audiences, there is no doubt that the operation will be repeated a good many times ere the pantomime is withdrawn. “Old Dame Trot” is indeed one of the best shows ever produced at this house […]. How St. George falls in love with Dame Trot’s daughter, Elaine, and the Seven Champions find it difficult to obtain cheap lodgings in Coventry, how Lady Godiva rides and Peeping Tom peeps as per legend, and how many other new lights are thrown upon ancient history, there is no need for me to explain. In the words of a former proprietor of this Amphitheatre I will, if you please, cut the cackle and come to “the ’osses,” under which designation I will, for once, include scenery, ballets, funny business, and zoological supernumeraries, all of which are very fine.

3-: From The South London Press (London, England) of Saturday 21^st March 1885 [page 12, column 5]:

“Khartoum” at Sanger’s.

In accordance with a tradition of the equestrian establishment in the Westminster-road, the war engaging our troops in the East has been made the subject of a drama. At old Astley’s, the Sikh war, the Battle of Alma, and other memorable events of military character, have furnished subjects for very successful spectacles, and there is little doubt that equal success will be achieved by “Khartoum.” Since Saturday night, when the drama was first produced, important changes have been made with good effect. The dialogue has been condensed, and old Phil Astley’s observation, “Cut the cackle and come the ’osses,” has apparently been remembered by the management.

4-: From Dramatic Novels, published in The Globe and Traveller (London, England) of Tuesday 2^nd June 1885 [page 1, column 5]:

An English audience loves action, and dislikes talk, except such a modicum as shall assist the movement of the play. In fact, if “action” be substituted for the last word of Ducrow’s oft-quoted expression, “Oh, cut the cackle and come to the ’osses,” it will exactly represent the opinion of ninety-nine British playgoers out of every hundred.

5-: From a review of The Corpse in the Copse; or, The Perils of Love: A Sensational Story (London: Field & Tuer, [&c.], 1886), by Lewis Lorraine—review published in The Saturday Review of Politics, Literature, Science, and Art (London, England) of Saturday of 10^th April 1886 [page 516, column 1]:

The Corpse in the Copse is as gruesome as heart can wish, though we fear enthusiastic amateurs of sensation will be inclined to echo the sentiment attributed to Astley (was it not?) when he requested the author of one of his equine melodramas to “cut the cackle and come to the ’orses,” in this case the story, which is obscured by a most inordinate amount of talk. Mr. Herbert ——’s feelings about the murder he wishes, yet dreads, to commit, are interminable, and detailed with the utmost conscience, but without much reality.