7, 14, 28 and 42 days after arrival. The calves were not given any antibiotic upon ar-
rival at the feed lot. The rate of spread varies with the organism. Few calves had either M. bovis or M. haemolytica in their nasal passages in Tennessee. The number of M. bovis-positive calves increased 2 weeks after arrival at the feedlot and peaked after a month. On the other hand, the calves carrying M. haemo-
lytica increased from the initial mixing of the cattle and peaked at 14 days. This coincided with the number of sick calves observed at the feedlot. The number of calves found to carry P. multocida
also rose steadily after arrival and peaked at 28 days, when 51 percent of the calves were positive. H. somni-positive calves rose more slowly than the
other 3 organisms, peaking at day 42 with 53 percent of the calves positive. Spire says this shows organisms frequently associ-
ated with pneumonia are present in the nasal passages of calves and notes it’s easy for the pathogens to migrate from the upper respiratory tract deeper into the animals’ lungs following periods of stress or viral infection, or when the calf’s immune system is compromised. He says, “Setting up a treatment program is a lot
percent were persistently infected with BVD. “That’s a signifi cant number,” he says, “because
that virus sheds out of that calf and goes to all the rest of them. We found BVD in load after load of cattle. It shifts our death loss up and shifts our sickness levels up and makes it tougher for crews on the other end to manage stocker calves in those situations.”
Crowded nose “The nose of the calf,” says Spire,
“is a crowded place.” A recent study conducted by Merck Animal Health examined high-risk calves that were collected from at least 20 operations in Tennessee, processed at an auction market and then shipped to a Nebraska feedlot. The calves had samples taken from their noses to check for M. hae- molytica, P. multocida, H. somni and M. bovis, fi rst at the sale barn and then upon arrival in Nebraska, and again
86 The Cattleman September 2013
more diffi cult because of the differences in rates and timing of spread of these organisms from one calf to another. In the case of Mannheimia, you would want to select a drug that is highly effective and delivered at arrival or shortly after receiving a group of calves. For Mycoplasma or Pasteurella, a drug used up front would be of limited value due to the low and slow spread of these 2 potential pathogens. Delivery of products to aid in controlling Histophilus might be targeted to even later in a receiving program.” Spire suggests producers select the antibiotic that
Stress creates
an environment where bacteria or viruses proliferate.
offers the longest persistence in the animal’s tissues. He says stocker calves will receive what’s called “metaphy- laxis,” the timely mass medication of a group of animals to eliminate or minimize an expected outbreak of disease. “We’ll treat them right at arrival,” he says. “There’s no guarantee that you’re going to steril- ize the nasal passage on these calves. You’ll reduce the numbers, but they tend to spring back.” He also says all drugs may not work
against all bugs. Of the 12 to 15 percent of calves that will be positive at arrival for M. haemolytica, around one quarter of them — 4 percent of the overall herd
thecattlemanmagazine.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124