Cattle played important roles at Monticello. They supplied beef, milk, and butter, while their manure was used to fertilize crops. Oxen were used to pull plows and carts, and later on, were butchered for their meat. Generally, Jefferson did not import cattle, but got them from Western Virginia . The cattle were raised on plantations in Albemarle and Bedford counties and were butchered either at Bedford or at Monticello. They grazed in pastures and woods, but never in cultivated fields .
Primary Source References 
1775 8 February 8. "A large plough with 4. oxen ploughed 24. furrows half a mile long 10.I. broad & 6.I. deep in a day, which is about 1 1/4 acres." 
1795 December 25. "Recd. of Philip Timberlake for an ox from Poplar forest sold on the road 50/." 
1813 July 19. "Drew in his [David Higginbotham's] favor on Gibson & Jefferson for 80.D. to wit for the 25. D. ante 10., the 5. now recd. & 50.D. for Sharp for a pr. of oxen." 
1793 June 30. (Jefferson to Thomas Mann Randolph). "Such a farm will well maintain 150. cattle, which properly attended to will make manure enought for ine feild [sic] every year...I presume that oxen may be substituted for half the horses." (in a letter discussing a farming plan that would have five ploughs, each with a pair of horses. 
1793 August 11. (Jefferson to Thomas Mann Randolph). "I found considerable hopes on the [[threshing machine]] expected, as 4. horses suffice to work that, and I had proposed to work my ploughs with oxen." 
1819 March 29. (Petty Vaughn to Jefferson). Vaughan gave Jefferson at Monticello a "hastily written" paper "respecting ox yokes, with an accompanying model." This model is lost.
1822 March 9. (Edmund Bacon to Jefferson) "We have 7 mules and one horse here and four oxen and three milk cows."
References from Jefferson to Poplar Forest overseer, Jeremiah Goodman
1811 December 31. "We are in very great want of the pair oxen from Poplar forest, as only 1. pair of those we have are worth a farthing for work. As soon as you can spare the other pair I must get you to send them here. The day I left Poplar forest I met many carts with a pr. of oxen and a horse carrying a hhd. of tobo. to Lynchbg. and with great ease. It occurred to me that had much better adopt this mode of carrying our tobo. to market, and wheat also. Each plantation might equip 2. such carts, so as with the [wa]ggon they might send 5 hhds. of tobo. or 160. bushels of wheat a day to market." 
1814 November 11. Regarding carrying wheat crop to the mills: "A cart with 2 oxen and a horse, will do as much at this as a waggon." Regarding poor condition of Poplar Forest livestock: "If we added to this [provision of peas], as we might do, large supples of hay from clean and well kept meadows, our oxen would be kept in order to do double work, cows give 3. or 4. times the milk, and every thing be fat, without opening the corn house door for a single animal." 
In the period from 1794 to 1796, the Monticello and Shadwell overseers submitted reports on livestock. Hugh Petit noted that the Monticello oxen would need four barrels of corn each month, the beeves would take three barrels per month, and the out Cattle at the quarter would take on a barrel & half per month . Eli Alexander reported seven oxen and ten cows at Shadwell on 10 January 1795 . At another time in 1794 or 1795 he estimated the cattle's need for corn within one hundred days: "8 oxen when hauling to have 2 gallons each suppose 40 days is 80 bushels of corn." So, presumably the oxen got no corn on their days off .
2. See Betts, Edwin M., ed. Thomas Jefferson's Farm Book: With Commentary and Relevant Extracts from Other Writings. Princeton: Princeton University Press, 1953. Rep. 1976, 1987, 1999. Manuscript and transcription available online at http://www.thomasjeffersonpapers.org/farm/, 110-111.
3. Please note this list is not comprehensive.
4. Bear, James A. Jr., and Lucia C. Stanton, eds. Jefferson's Memorandum Books: Accounts, with Legal Records and Miscellany, 1767-1826. Princeton, NJ: Princeton University Press, 1997., 1:386.
5. Ibid, 2:935.
6. Ibid, 2:1290.
8. Ibid, 26:658.
9. Betts, Edwin M., ed. Thomas Jefferson's Farm Book: With Commentary and Relevant Extracts from Other Writings. Princeton: Princeton University Press, 1953. Rep. 1976, 1987, 1999. Manuscript and transcription available online at http://www.thomasjeffersonpapers.org/farm/, 68.
13. Eli Alexander List. Ibid.
- McEwan, Barbara. Thomas Jefferson: Farmer. Jefferson, N.C.: McFarland, 1991.
- Look for sources in Thomas Jefferson's Farm Book at the Massachusetts Historical Society.