Not so long ago the major studios might have jumped at the chance to film the books of Dr. James Herriott - and would have known how to adapt and market them effectively. Now, one must be satisfied with a grudging but half-hearted gratitude for "All Things Bright and Beautiful," a dowdy, underfinanced, yet irresistibly appealing movie version of Herriot's second autobiographical best seller.

Why should Herriot's authentically colorful and inspiring material, a chronicle of his experience as a veterinarian in the Yorkshire countryside in the late '30s, have to limp along on meager production resources? The sales of his three books - "All Things Bright and Beautiful" was preceded by "All Things Great and Small" and followed by "All Things Wise and Wonderful" - would appear to justify a decent filmmaking investment. In fact, all three might have been made for the amount - $6 million - that MGM reportedly wasted on its misbegotten "International Velvet."

The first two volumes were filmed by Talent Associates, producer David Susskind's company, in association with Reader's Digest. Both pictures were released theatrically in England. Failing to find an American ditributor, "All Creatures Great and Small" eventually surfaced as a TV special sponsored by Hallmark. The sequel was acquired by Albert Schwartz, an independent who also imported Franco Brusati's "Bread and Chocolate."

The MGM that produced "Goodby, Mr. Chips," "Lassie Come Home" and "National Velvet" possessed the incentive and qualifications necessary to do justice to a book as unaffectedly decent and disarming as "All Things Bright and Beautiful," a leisurely, humerous memoir evoking a happy, active useful way of life. The MGM that produced "International Velvet" obviously can't distinguish the heart-warming from the hateful.

One can't pretend that "Bright and Beautiful" is an important or indispensable movie. It's discouraging to think how beautiful this subject matter might have been if it had attracted filmmakers at once gifted, dedicated and influential enough to demand a class production.Each time I stared at one of Arthur Ibbetson's washed-out landscapes or drab set-ups, I cursed the producers for lacking the wherewithal to hire a cinematographer conscious enough to render Herriot's settings in adequately vivid and evocative images.

Nevertheless, the inherent charm and contentment of Herriot's material keeps shining through. It's difficult to resist even a bumptious-looking movie that opens with an episode as satisfying as the downbeat to "All Things Bright and Beautiful," where young Dr. Herriot is summoned to the cageside of an ailing budgie, which promptly croaks the instant he reaches for it. What can the vet tell the dear old lady who has cherished the budgie's company for many years? His solution begins the story with a swell comic flourish while establishing our hero as a man of rare ingenuity and compassion.

The screenplay by Alan Plater retains Herriot's structure while soft-predaling his pronounced episode rhythm. The chapters of the book tend to consist of self-contained anecdotes, a potentially ideal arrangement for bedtime reading and TV serialization.

The movie is still more concerned with transposing the texture of a young practitioner's life than exploiting any particular dramatic crisis that might emerge from it. Plater generates a modest amount of suspense over an offer to practice in the city which seems especially tempting after Mrs. Herriot becomes pregnant. However, this potential crisis is approached and passed more or less incidentally.

A global crisis looms in the background: World War II. This specter is subtly used to enhance the value of the ordinary spectacle of life that absorbs the Herriots.The movie closes on a wonderful, unemphatic lyric note as Dr. Herriot goes out for a stroll with his infant son minutes after listening to a war declared over the wireless.

This sublime conception would have played even better if someone refrained from superimposing credits over the concluding images. The idea behind the fadeout remains exceptionally stirring. The gravity of the situation is ironically underlined by the calm, pensive responses of the country people we've come to identify with. Big gestures aren't appropriate here. It's a moment for getting on with business or taking the air with your child, ordinary activities that suddenly seem vulnerable and precious.

Simon Ward and Lisa Harrow portrayed the Herriots in "All Creatures Great and Small." Harrow returns in the sequel, but Ward has been replaced by John Alderton, best known here for his performance as Thomas Watkins, the aspiring, opportunistic chauffeur in "Upstairs, Downstairs." A prominent moustache gave Alderton a dashing, dangerous aspect as Watkins. Shorn of this adornment, he looks rather boyish and insipid, but he's such a droll, expert underplayer that he ends up making a sneaky virtue of his superficial wimpiness. His Dr. Herriot is made of sterner nice stuff than one might suspect at first glance.

Several characterizations benefit from a similarly loose, disarming method of delineation. For example, a student who briefly joins Herriot and his senior partner Siegfried Farnon (Colin Blakely in a rather too predictable impersonation of endearing irascibility) seems like a disaster when he steps off the train - too citified and silly-ass to adjust to the country. Without dropping certain silly-ass traits, the student nevertheless reveals himself to be game, perceptive and valuable.

Director Eric Till bears down too heavily on certain comic situations, especially Herriot's attempt to consume a heavy Yorkshire repast offered by a grateful client. However, he establishes just the right tone in a protracted wine-tasting session between Herriot and a wine-making old countryman, played delightfully by John Barrett.

This diversion is interrupted by the most impressive medical emergency in the film - the delivery of a newborn calf, with Alderton himself up to his elbow in the job. What a movie this might have been if everyone involved had responded with equal dedication! Herriot reads like a natural for classic children's films, but who's in the market for such and virtuousness in Hollywood?