TEXT 5. Choice of Animals for the Commercial Herd

The following items should be given much consideration in choosing the annuals which are to form the foundation of a new herd or which are to serve as additions or replacements for a herd already m existence:

1. Freedom from disease.

2. Individuality.

3. Performance records (if available).

4. Performance of near relatives.

5. Age.

6. Cost.

Freedom from Disease. The most important item in the determina­tion of profits is percentage of calf crop, and the best insurance against poor calving percentage is a healthy herd. High selling prices due to extra quality and weight or low feed costs cannot offset low calving percentage and large death losses. .

Important contagious reproductive diseases of breeding cattle which must and can be guarded against are brucellosis (contagious abor­tion), leptospirosis and vibriosis in females and trichomoniasis in bulls. These diseases can be minimized at the time of purchase by demanding negative results from tests conducted by qualified veter­inarians on all breeding animals composing the foundation stock or additions to the herd. Replacements which are produced in one's own herd should be free of these diseases if the herd is healthy. How­ever, annual tests should be made on these additions as well.

TEXT 6.Significant Features of Ruminant Nutrition

Ruminant animals such as beef cattle are usually found on farms and ranches which, either because of choice on the part of the operator or because of necessity due to low rainfall, erosion problems, or infer­tility of the soil, produce large quantities of roughage and or pasture. Ruminant animals, so called because they ruminate or chew cuds, have special adaptations in their digestive systems which enable them to utilize roughages or feeds which contain comparatively high levels of crude fiber or cellulose and related compounds. An understanding of these special adaptations is of value in determining feed or nutrient requirements of beef cattle, and by the same token an understanding of nutrient requirements is essential for proper ration formulation.

Significant Features of Ruminant Nutrition. Monogastric ani­mals or those having simple stomachs, such as the pig and man, have a relatively low-capacity alimentary tract consisting of stomach, small and large intestines, and accessory glands. Digestion in these animals is largely of an enzymatic nature and little provision is made for either handling or digesting roughages; hence the diet of such animals must consist largely of concentrates or feeds low in crude fiber. In con­trast, ruminant animals have compound stomachs and a much more complex digestive system, and much remains to be learned about their anatomy and function. Productive research work with the artificial rumen and the rumen fistula in the live animal is shedding much light on the so-called darkest spot in animal nutrition, the rumen.

The most successful cattle feeders today are those who understand and take advantage of the following significant features of ruminant animal:

1. The Four-Compartment Stomach. The rumen or paun . first compartment, constitutes about 80 per cent of the total stoiin­capacity in adult cattle and may hold up to 50 or 60 gallons. Con­nected with the paunch are the second and third compartments, tht- reticulum or honeycomb and the omasum or manyplies, which con­stitute 5 and 7 or 8 per cent of the total stomach capacity, respec­tively, in mature animals. All three of the compartments thus far mentioned have a common opening or passageway called the eso­phageal groove, through which materials may pass freely. The func­tion of the reticulum is not too well understood, but it is known that the omasum is the site where much water is absorbed from the paunch contents prior to its passage into the fourth compartment, the abomasum or true stomach. The abomasum holds about 7 or 8 per cent of the total stomach contents, and this compartment is simi­lar in function to the stomach of simple-stomached animals.

Symbiotic Microorganisms of the Paunch. Because the paunch provides an ideal environment such as proper temperature, moisture, nutrient supply, et cetera, for bacterial life, literally billions of bac­teria—up to 100 billion per gram of dried paunch contents—and protozoa live in the paunch, to the mutual benefit of both the micro­bial life and the host animal, the ruminant. This mutual benefit or support is known as symbiosis. The breakdown of cellulose and related compounds by the enzymes produced by these symbiotic microorganisms accounts for the higher feeding value of roughages when fed to ruminants. Volatile fatty acids are produced as a result of the microbial fermentation of carbohydrates in the paunch.. The most important of these acids, in terms of amount of acid produced, are acetic, propionic, and butyric, in that order. It has been estimated that from 40 to 50 per cent of the carbohydrate portion of beef cattle rations may be converted to these acids and absorbed directly from the paunch, after which they are metabolized to be used as energy or stored as fat. Thus fatty acids are a major source of energy in ruminant rations, as contrasted with the situation in simple-stomached animals, in which carbohydrates are largely absorbed as glucose after digestion in the stomach and small intestine.

Bacteria Synthesize Protein in the Rumen. As bacteria and the other microorganisms living in the paunch of the ruminant animal multiply, they build or synthesize the protein required for new cells. They make use of whatever source of nitrogen is present in the feeds.