NEWSLETTER ARTICLES

Livestock and Natural Resources

The following article by Dr. John Maas, Extension Veterinarian at UC Davis, provides a good summary of a cattle health problem many producers can or have experienced - pneumonia in cattle.

This can be a common and sometimes frustrating problem. Use of antibiotics to treat these cattle is just as common and sometimes just as frustrating. Most producers think of pneumonia as a single condition, because of the symptom syndrome. Calves and older cattle exhibit an increased respiratory rate (panting), fever (rectal temperature over 102.5°F), coughing, loss of appetite, and/or nasal discharge (mucous). Peumonia, however, has several different causes and varies in severity from mild to rapidly fatal, and we know from experience the disease can be unpredictable.

What is pneumonia?
Pneumonia is an inflammation of the tissues of the lungs that results from the response of the animal to an infectious agent, which can be either a virus or a bacteria, or in many cases both.

Common viruses that can initiate pneumonia in cattle include: IBR (infectious bovine rhinotracheitis virus; a herpes virus , BRSV (bovine respiratory syncytial virus), PI3 (parainfluenza 3 virus), certain rhino viruses, and a host of other viruses. Often the virus infection causes tissue damage, and then bacteria invade the compromised tissues.

The bacteria most often involved include Pasteurella hemolytica and Pasteurella multocida. These two bacteria are never far from cattle and are particularly adept at infecting lung tissue damaged by viruses. Other bacteria commonly involved in pneumonia include Mycoplasma species and Actinomyces species, to name a few.

Antibiotics have no effect on viruses (IBR, PI3, etc.) and will kill bacteria only if that particular strain of bacteria is susceptible to the antibiotic being used. Also, the dose of the antibiotic must be high enough and must be given long enough to kill the bacteria involved in the pneumonia. Bacteria can develop resistance to certain antibiotics and this resistance can be transferred from one generation of bacteria to subsequent generations genetically. Therefore, strains of antibiotic resistant bacteria can and have developed.

What are some of the criteria used to decide which antibiotic to use for pneumonia cases?
The first consideration has to do with the likely organism(s) involved in the pneumonia. This is usually based on past experience and specific signs of disease. Another could be the cost of the antibiotic; if a cheaper drug will work, we usually will select that drug. The next consideration could be the route of administration; whether it is administered subcutaneous [sub-Q], intramuscular [IM], intravenously [IV], or orally is also an important consideration. Also, the number of times per day that treatment must be given is very important. Whether or not the drug is given in an extra-label manner and thus would require a veterinarian's prescription can be important. The potential adverse side effects must be considered also. All common antibiotics have advantages as well as disadvantages.

What are some of the common antibiotics used for treatment of pneumonia in cattle?
There are a number of newer drugs as well as some that have been around for many years. Some of the newer drugs include: Naxcel®, Nuflor®, and Tilmicosin®. Also relatively new are the long acting tetracyclines, which can now be given subcutaneously instead of intramuscularly. Older drugs include Polyflex® (ampicillin), penicillin, Tylan®, sulfa drugs, and erythromycin.

There is no best drug to use, as is obvious from all the above considerations. As producers, you should discuss the best approach to treatment of pneumonia with your veterinarian. Come up with a plan to identify pneumonia cases, which drug to use, and by what route of administration to give this drug. Next decide how many days to treat and if therapy is not successful, what will the next treatment be. Know what the withdrawal time of these treatments is. If drugs are to be used in an extra-label manner, be sure to have your veterinarian's prescription label affixed to all drug containers. The new laws regarding prescription and extra-label drugs in California have changed, and these regulations must be followed more strictly than in the past to avoid serious potential problems for both producers and veterinarians.

EVALUATING BULLS FOR BREEDING SOUNDNESS
by Wayne Jensen

As breeding season is fast approaching, I thought the following article would be of interest. Many producers semen check their bulls, but do they really look at these animals in terms of their primary function, which is to get their cows pregnant as early in the breeding season as possible?

Up to 20% of all bulls have less than optimum fertility. Bulls with poor fertility may get some cows pregnant, but the proportion of open cows will be higher than normal. Additionally, the calving season may cover a longer period of time with many cows calving late.

In 1993, updated guidelines for evaluating and classifying bulls for breeding soundness were released by the Society for Theriogenology. The updated Breeding Soundness Evaluation (BSE) guidelines use parameters which have stood the test of time and incorporate the latest scientific information. In general, the minimum threshold standards selected are not overly rigorous. However, they are based on the latest scientific evidence and experiences with all breeds under varying managerial and environmental conditions.

These thresholds are based upon considerations of reproductive adequacy, not necessarily upon genetic merit. The guidelines provide minimum acceptable standards for a bull to be reproductively sound.

A BSE is comprised of the following four components:

1. a general physical examination

2. a reproductive examination

3. measuring scrotal circumference (SC)

4. a semen examination

General Physical Examination:
The physical examination should consist of a general evaluation of health, well-being and body condition of the bull. Any physical problem can potentially reduce fertility under natural mating circumstances, but some are more important than others.

Conformational and structural soundness are important components of breeding soundness. Defects in the structure of feet and legs can seriously affect fertility and can shorten the breeding life of a bull. Common leg problems relating to bull fertility include:

Sickle hocks

Postlegs

Pastern problems and sore hocks

Camped out hind legs

Bow legs

Additionally, bulls need to see, eat and smell. Any problem in these areas is good reason for questioning the breeding soundness of a bull.

Reproductive Examination:
A thorough examination of the male reproductive system follows the general physical examination. Developmental defects and inflammation are common problems. The accessory sex glands can be examined rectally, while the spermatic cord, scrotum, testicles, and epididymides can be palpated externally. The penis and prepuce are generally examined during electro-ejaculation for a semen sample.

Missing or underdeveloped portions of the male reproductive system are not common problems, but are important in that they can have severe effects on fertility. One common developmental defect, which will prevent a bull from servicing, is persistent penile frenulum (tied-back penis). Correction of this problem is easy, but be careful when using a bull even after correction. The condition appears to be heritable.

Inflammation of portions of the reproductive system is common, especially in groups of young bulls housed in fairly confined areas. This condition is often diagnosed as vesiculitis (inflammation of the vesicular glands), but it has been shown that inflammation in this area is usually accompanied by inflammation in adjacent accessory sex glands. Semen quality is generally decreased under these circumstances. Many bulls with this condition recover without any treatment; some respond to antibiotic therapy while others never recover.

Changes in testicular tone are associated with a degenerative process and can be detected to some degree by testicular palpation. Degenerative change in the testicles is a frequent cause of infertility. This condition is a common occurrence following inflammatory reactions. Many non-disease factors can also contribute to testicular degeneration (e.g., injury or old age). Regardless of the cause, the effect is reduced fertility.

Scrotal Circumference:
Minimum recommended scrotal circumferences for bulls of all breeds, based on age, are listed in Table 1. Emphasis is placed on standards for puberal bulls up to two years of age. Although these thresholds provide considerable latitude, variations will occur with breed, age, level of nutrition and genotype.

Table 1. Minimum recommended scrotal circumference based on age.

Age		SC (cm)
15 months		30
15-18 months		31
18-21 months		32
21-24 months		33
24 months		34

Only bulls with satisfactory feet and leg conformation, good overall health, adequate scrotal circumference, and freedom from reproductive tract problems are candidates for continuing an evaluation. If results of the physical examination or scrotal circumference are not satisfactory, results of the rest of the evaluation will be of little importance.

Semen Examination:
A bull must have at least 70% normal sperm to pass the BSE. However, this requirement does not make any distinction between types of abnormal sperm.

Taking into account the varied and often trying conditions encountered in collecting semen samples in the field, the minimum recommended sperm motility of 30% (see Table 2) serves to indicate a representative sample of semen was obtained. While total absence of motility may indicate severe reproductive problems, graduations of motility above 30% in samples collected by electro-ejaculation do not relate well to increasing pregnancy rates. For example, no motility in an otherwise good ejaculate may indicate a problem. but as long as one-third of the cells are motile, increases above this rate do not seem to relate to fertility.

Table 2. Motility Ranking.

Mass Activity (gross)	Rating	Individual Motility
Rapid swirling	Very good (VG)	70%
Slower swirling	Good (G)	50-69%
Generalized oscillation	Fair (F)	30-49%
Sporadic oscillation	Poor (P)	<30%

Recommended minimum motility is 30% or Fair (F).

For bulls to be classified as "Satisfactory Potential Breeders," they must pass a physical examination and equal or exceed the minimal thresholds in each of the following areas:

Scrotal circumference based on age

70% normal sperm

30% individual sperm are motile

Bulls which do not equal or exceed these thresholds will either be classified as "Unsatisfactory Potential Breeders" or will have their "Classification Deferred." Placement in the latter category always implies that a retest is intended (usually 30 to 60 days).

A BSE should be a systematic evaluation used to arrive at the best estimate of potential fertility. It should be emphasized that performing a BSE requires experience, judgment and scientific knowledge. As such, the estimate is related to skills of the veterinarian performing the evaluation.

A BSE is not a "fertility evaluation" - the only true fertility evaluation is placing a bull with cows and determining pregnancy rates, nor is it a "semen check." Checking only semen will cause one to overlook many factors affecting breeding soundness.

The BSE attempts to measure only the potential of a bull to get cows pregnant. It does not consider his desire or ability to perform in the breeding pasture. Presently, a good, quick, accurate method to measure libido or mating ability, both of which are extremely important factors in reproductive performance, is not available. The only way to make these assessments is for producers to observe one or two matings. Having all bulls subjected to a BSE every year will definitely help breeders identify infertile and subfertile bulls and will ultimately result in higher pregnancy rates in their herds.

After reading this article, you might take a look at your bulls. Even though you checked their semen, are you sure they can get your cows pregnant as early in the breeding season as possible?

1996 GROSS VALUE OF SANTA BARBARA COUNTY'S AGRICULTURAL COMMODITIES
by Wayne Jensen

Each year, agricultural commissioners in California report the value of the commodities produced in their respective counties. Santa Barbara is no exception. This year Bill Gillette and his staff reported the 1996 gross production in Santa Barbara County was valued at $581,637,098 with 33 commodities exceeding $1,000,000 in value.

How does this compare to the other counties in the state? Recently, I received a copy of the Summary of County Agricultural Commissioners’ Reports of the Gross Values of Commodity Groups for 1995-96 and learned Santa Barbara County ranked 15th among the 58 counties in California in the value of agricultural production in 1996. Several of the commodities grown in the county rank among the top five in the state. Santa Barbara County was the second leading county in the production of flowers and foliage, broccoli, and cauliflower, third in the production of avocados, and celery, and fourth in the production of lettuce, strawberries, asparagus, and spinach. I would be remiss if I didn’t mention, while Santa Barbara County isn’t in the top five livestock producing counties in the state, we still rank in the top ten.