NavMeshAgent, my object is floating in the air.. why?? :(

Hi guys,

I'm trying to create a simple AI to my sheep but I have some problems. My sheep is floating in the air, she is not on the ground.

Anybody have any idea how to fix it? Thanks

Sheep.cs

 using UnityEngine;
 using System.Collections;
 
 public class Sheep
 {
     private GameObject obj;
     private Object prefab;
 
     public Sheep(string name, Vector3 position)
     {
         prefab = Resources.Load("Prefabs/Sheep");
         obj = GameObject.Instantiate(prefab) as GameObject;
         obj.name = name;
         obj.transform.position = position;
         obj.AddComponent<NavMeshAgent>();
         obj.AddComponent<AnimalActions>();
     }
 }

AnimalActions.cs

 using UnityEngine;
 using System.Collections;
 
 public class AnimalActions : MonoBehaviour
 {
     private NavMeshAgent nav;
     private GameObject[] waypoints;
     private int waypointIndex;
 
     void Awake()
     {
         nav = GetComponent<NavMeshAgent>();
         nav.obstacleAvoidanceType = ObstacleAvoidanceType.HighQualityObstacleAvoidance;
     }
 
     void Start()
     {
         waypoints = GameObject.FindGameObjectsWithTag("Farm");
         waypointIndex = Random.Range(0, waypoints.Length);
     }
 
     void Update()
     {
         if (nav.remainingDistance < 0.5f)
         {
             Patrol();
         }
     }
 
     void Patrol()
     {
         nav.destination = waypoints[waypointIndex].transform.position;
         waypointIndex = Random.Range(0, waypoints.Length);
     }
 }