Welcome to the Longhorn arena! One "general" reference (loose-leaf thick notebook) is the Texas Beef Cattle Management Handbook, published by Texas A & M University. A good introductory book is "Storey's Guide to Raising Beef Cattle."
Longhorns, being beef cattle, have been in USA for around 500 years. Survivors and very hardy, tolerant of all climate types. Easy unassisted calving. Two breed associations: <A HREF="http://www.itla.com" TARGET="_blank">www.itla.com</A> and <A HREF="http://www.tlbaa.com" TARGET="_blank">www.tlbaa.com</A> have very good information on them.
Feeding: eat anything other cattle eat. Vaccinations: Usually spring and fall with multi-purpose serum, such as 7-Way. De-worming twice yearly: Injectible Dectomax or Ivomec. Longhorns are generally easy-keepers. As with any cattle, fencing is related to the amount of "security" and peace and quiet you are willing to tolerate. I personally use 5-1/2 foot high 6 & 7 barb wire fencing. Even a 1% chance of one of our registered foundation stock getting out is too much grief for me at my age. They like to frollic and play at times and can jump and buck when bored or introduced to a new pasture. Love to check out for weak spots in fences when they first arrive at your place...then settle down. Most longhorns are peaceful, docile, excellent mamas, and very people-friendly.