Internal Parasite Control In Calves

Press, Issue 32333, 26 June 1970, Page 10

Internal Parasite Control In Calves

The value of calves as a source of farm income has assumed greater importance in recent years because of the continuing high price for beef. The demand for bobby calves for rearing for beef production has resulted in a wider interest in the care of calves and it is during the first winter that the problems of rearing young stock are greatest.

The high cost of week-old calves or weaned calves has reached the point where profit margins are narrow and one death during the first winter immediately reduces the expected profit level. The primary aim when rearing calves for profit must be to bring them in to the spring at the maximum body weight and healthy. Such calves will be ready to develop and grow with the spring-summer grass growth. Winter management must revolve round adequate feeding and the control of both external and internal parasites. Early recognition of internal parasites and treatment will, in most instances, prevent loss of body weight and unthriftiness. All young stock, calves included, carry some degree of infestation but under sound management and feeding, the level of infestation is kept at a minimum. However, under conditions of stress, such as lowered food intake, prolonged cold, wet conditions, extended yarding and transport, lack of shelter, overstocking, the level of parasites quickly multiplies. The number of eggs shed on to the pasture rises sharply and far greater numbers of

infective larvae are ingested. Early symptoms of calves affected with internal parasites will be loss of appetite, loss of body weight, and general signs of unthriftiness. The coats become rough and dry. Calves will only pick at grass and they tend to move away from the mob. They become weak and reluctant to travel. When handled it will be seen that the mucous membranes of the eye and mouth have lost their normal pink colouration and have become pale and white. In severe cases, there will be

diarrhoea and emaciation. Death will result or, because of their lowered resistance, calves will become susceptible to secondary diseases or conditions. It therefore becomes necessary to be able to recognise symptoms early. This demands almost daily observation of each animal. If doubtful of the cause of unthriftiness, or if internal parasites may be a factor, immediate advice should be sought from a private veterinarian or the Animal Health Division of the Department of Agriculture. Most calves are susceptible to internal parasites and the most troublesome are those species found in

the abomasum or fourth stomach and in the first section of the small intestines. All these worms have a similar life cycle beginning with the adult worm laying eggs which are passed out on to the ground in the faeces. Under suitable conditions these eggs hatch into infective larvae which climb on to the blades of grass and are in turn eaten by the grazing calf. They reach maturity in the host animal and so complete the cycle. It is the adult worm in the fourth stomach and intestine which causes progressive anaemia by sucking blood from the stomach wall and by interfering with the absorption of foodstuffs by the animal. Under moist conditions and prolonged muggy weather, over-stocked pastures favour a marked increase of infective larvae. The cycle can be easily broken, however, by denying stock, and particularly young animals, access to infected pastures and giving them clean paddocks which have been spelled long enough to allow most of the larvae to

The accompanying item contains excerpts from an article on the control of internal parasites in calves prepared by Mr .4. R. Diack, livestock instructor of the Department of Agriculture, Christchurch.

die. This period is usually 15 to 21 days but may be greater during moist or humid conditions. The principle of rotational grazing has been proved beyond all reasonable doubt to be the most effective and economic method of parasite control. The old method of, set stocking calves in a calf paddock cannot be too strongly condemned. The shifting of stock through a number of fresh paddocks at regular short periods involves the farmer in some extra labour. Calves must be moved ahead of other stock and should not graze any area longer than two to three days. The feed is then always fresh, leafy, clean, and almost free from infective worm larvae. There are several cattie drenches available which, if used according to the manufacturer's recommendation, will reduce the adult worm to a minimum level. However, it is the management immediately after treatment which is the vital factor if full control is to be obtained. The action of most drenches is to reduce the animal's burden of mature worms. After drenching, calves should be held for a day in a handy yard while the drench acts, then turned out on fresh pasture and rotated on to other clean paddocks at short intervals. The problems of internal parasites in calves cannot be complete without considering the problem of lung worm infestation. Lung worm is often found in young stock already affected with stomach or intestinal worms and can be a factor which accelerates un-

thriftiness and death. Lung worm can be a problem in the late winter-early spring period, particularly after a cold, wet winter. This is the most critical period in the early life of a calf, when the stress factor is greatest for a few weeks until spring growth starts. The lung worm parasite is a white, round worm up the 3in in length and lives in the trachea and bronchi of the lungs. The larvae are picked up from the pasture and penetrate the intestinal wall and travel by the bloodstream to the lungs where the mature worm develops. The cycle is completed by coughing up the eggs which are swallowed and develop into infective larvae while passing through the intestine and out on to the ground. The characteristic symptoms of lung worm infestation is a husky cough together with heavy breathing. Under suitable moist conditions, lung worms may occur so severly as to cause pneumonia and death. Generally, however, normal drenching for stomach worms, together with the right follow-up management, permits the animal to develop a level of immunity against any light infestation of lung worms. “As a guide to good calf management, I suggest the following principles: “(a) If your calves are not thriving at present, seek advice. It may be that drenching now and good winter husbandry will be the answer. Early use of a broad-spectrum drench will keep calves healthy and at maximum growth rate. “(b) Keep calves and yearling stock off wet and swampy country. Adult stock which develop some resistance to worm infestation can graze wet country far more effectively. “(c) Avoid over-stocking. Carry out rotational grazing if possible. Clean pasture should always be provided. As you double the stocking rate you quadruple the parasitic burden. The longer calves are left on a paddock the more complete is the life cycle of the parasite. “(d) Always keep the nutrition of the calf at as high a level as possible by a supplementary ration of high quality hay and other recognised foods. This is good husbandry and assists the calf to overcome and resist other infections.’’