News About Goats

by VICTOR L. SIMMONS

GOATS, being useful and personable animals, are attracting more and more interest among Americans. Consumers want to know more about goat milk, mohair, and chevon. Breeders look for guidance to develop better animals and better products.

As with other animals, progress in breeding milk goats depends upon selecting and mating animals that inherit the ability to give more milk and butterfat. Physical appearance alone is an unreliable index. A newer and better method is genetic selection by basing the choice of breeding stock on records of individual performance and progeny and on the pedigree, if other records are unavailable. Data of this kind will enable breeders to develop constructive breeding programs and to identify individuals most likely to improve their herds.

Through a Star Milker award, introduced by the American Milk Goat Record Association, new opportunity is provided for obtaining performance records for does tested at Official Milking Competitions. This 24-hour test is particularly important to goat owners who keep (toes only for the family milk supply or as a hobby. Such animals may now be tested without the expense of the usual Advanced Registry 10-month testing. Goat raisers may obtain information about entering their does in official milking competitions or qualifying them for "Star Milker Certificates" by getting in touch with the American Milk Goat Record Association, Sherborn, Mass.

Most does breed only in the fall and early winter, and a way to spread the period over which they come in milk is greatly needed by dairymen and others who must have a regular supply of milk. The simplest and most practical plan at present, provided there are enough does in a herd, is to breed some of them early and some late in the breeding season. A relatively large number of dry does may result, however, from their failure to come in heat as regularly or to breed with as much certainty during the latter part as in the early months of the breeding season.

Research with Hormones

The selection of does that tend to breed out of season gives some opportunity to develop strains that breed at all times of the year. But such natural methods take time, so scientists have been exploring the chances of artificially inducing lactation and stimulating extraseasonal breeding. Work by A. A. Lewis and C. W. Turner at the University of Missouri, and S. J. Folley, F. G. Young, and F. H. Malpress, at the University of Reading and the National Institute for Medical Research, London, first pointed to the possibility of inducing lactation in virgin goats by injections of stilbestrol, a synthetic chemical product having the properties of the natural estrogenic hormones. Later the scientists found that lactation induced in virgin and dry does by stilbestrol could be augmented with treatments of anterior pituitary gland extracts. This combination gave quicker results than injections with estrogen alone. In some cases, in which estrogen failed to induce lactation, the injection of anterior-pituitary extract was followed by heavy milk secretion. These experiments indicate that artificial induction of lactation depends on the maintenance of the proper relation of the estrogen level in the circulation to the activity of the anterior pituitary.

Research with hormones in their relation to lactation has suggested a rather peculiar phenomenon. The administration of estrogens and stilbestrol in certain amounts may effectively stimulate the initiation of milk secretion in virgin or dry animals but at the same time established lactation may be seriously depressed by the same hormones. J. P. Mixner, J. Meites, and Turner, working at the University of Missouri, initiated lactation in yearling virgin Toggenburg goats by daily subcutaneous injections of 0.25 milligram of stilbestrol, but in milking goats doses varying from one to four milligrams a day reduced the milk yield, apparently in proportion to the dosages given. The lactation-stimulating effects of small dosages of the hormone are explained as due to its stimulation of the anterior pituitary to the secretion of lactogenic hormone, while the lactation-inhibiting effects are thought by one group of workers to be the result of an overstimulation of the adrenal cortex.

The importance of hormones in udder growth and development has been shown experimentally. Mixner stimulated the mammary glands of virgin females to extensive lobule-alveolar growth by daily injection of estrogen (stilbestrol) and progesterone and indicated the need for both of these in causing complete mammary growth. Similarly, the British researchers found that either natural or synthetic estrogen will cause teat growth in virgin females.

The theory that goats breed normally in the fall because the days (periods of light) are becoming shorter may have much practical logic. T. H. Bissonnette, in experiments at Trinity College, Hartford, and at Hillshire's Goat Farm, Killingly, Conn., has shown that breeding cycles in goats may be induced by artificially shortened days or inhibited by lengthened days. He also concludes that the annual "temperature cycle is not a major factor in environmental control of sexual or breeding cycles in goats."

Stimulation of extraseasonal breeding in does by use of gonad-stimulating hormones has been emphasized in experiments by Department workers at Beltsville. In a preliminary test, Ralph W. Phillips, Ralph G. Schott, and I found that a dose of 200 rat units, or four cubic centimeters of pregnant mare serum (PMS) was without effect, but a dose of 400 rat units was enough to bring dry does into estrus. Lactating does were more difficult to bring in heat than dry does. We made a second experiment with similar treatments, but followed by an examination of the ovaries; it revealed that follicular growth and ovulation were frequently produced without visible estrus. If this condition occurs naturally, it may explain the difficulty in getting some does bred.

The inconsistency of inducing estrus in anestrous does indicates a need for study of the physiological mechanisms controlling estrus in the goat. Dr. Phillips, R. M. Fraps, and A. H. Frank report that very small doses of estradiol benzoate (0.05 milligram) will induce estrus in spayed does. The duration of estrus increases as the dosage of estrogen increases, but the latent period (hours from injection to estrus) does not vary consistently with the dosage of estrogen. For full estrous response in laboratory rodents, estrogen should be followed with progesterone, but there is little evidence that this procedure gives the same reaction in the doe. On the contrary, progesterone seems to shorten the duration of estrus induced by estradiol benzoate. Once the factors involved in the production of estrus are clearly understood, the induction of estrus and ovulation properly synchronized in anestrous does will have practical possibilities.