Reproduction

Angora goats have a reputation for low reproduction rates. This causes problems for the producer in terms of lost income from sale of excess animals, making progress in herd improvement, and maintaining herd numbers. There are various reasons for low reproductive efficiency. The most important is inadequate nutrition at one or more stages of growth or during the reproductive cycle. Many reproductive problems can be cured with adequate nutrition and/or increased management inputs that must be considered in light of anticipated economic returns.

The reproductive processes of Angora goats are similar to those of other goats. Major exceptions are the pronounced seasonality of mating in Angoras and problems associated with the high and competing

Fig. 1 Angora goats grazing in western Texas. (Photograph courtesy of J.W. Walker.) (View this art in color at www. dekker.com.)

demands of fiber production. Most Angora goats will attain puberty and breed at 18 months of age. Well-fed, well-developed kids occasionally breed at 6 8 months of age. Both males and females are seasonal breeders, the female having recurring estrual periods during fall/winter if not bred. Estrous cycles last from 19 to 21 days, with estrus itself lasting about one day. Gestation length is 149 days (range 143 153 days). The body weight and development of the doe are major sources of variation in ovulation and kidding rates, the ovulation rate decreasing with lower body weights.

Normal birth weight of kids ranges from 2 to 3 kg. Larger kids cause birthing difficulties for their dams, whereas smaller kids have low survival rates. A normal kid crop for commercial herds is in the range of 40 to 80%. Kid crops of 150% (i.e., 50% of does raised twins) have been reported in well-managed, small flocks. Low-kid crops can be a result of failure to ovulate or conceive, loss of embryo (resorption or abortion), or death of kid after birth. Most of these problems can be affected in a positive manner by improving nutrition and increasing the level of management. An example of the former would include a period of supplemental feeding before and during breeding. Examples of the latter would include kidding in small pastures or through a barn instead of on the range. Again, cost-effectiveness of all extra inputs is a major consideration for producers.

dual-purpose Angora goat. Hence, more emphasis has been placed on body traits such as gain and mature weight. In its current form, the Angora goat produces fiber more efficiently than any other animal to which it has been compared. Selection for fine fiber (i.e., more valuable fiber) and against medullated (hollow) fibers has been practiced also. Most of the commonly measured and economically important production traits are inherited in a quantitative manner (i.e., under control of many genes). Derivation of comprehensive indices to assist with selection programs (though beyond the scope of this article) requires knowledge of the economic value, variability, and heritability of each trait, and the relationships among traits.

Because economic values change over time, average values calculated over a long period of time are most useful (unless there is a clear indication or guarantee of future value). Shelton[5] reported ''consensus values'' for heritability of the various traits. Highly heritable (>0.25) values include lock length; clean yield; mature weight; face, neck, and belly covering; secondary/primary follicle ratio; and scrotal division. Moderately heritable (0.15 0.25) values include fleece weight, fleece density, average fiber diameter, kemp (medullation) content, and weaning weight, and lowly heritable values include reproductive rate, longevity, and adaptability. Because Angora goat breeders are interested in many animal and fleece traits, developing a comprehensive selection index for Angora goats is a difficult task. To further complicate the issue, few of the traits are completely independent, and all are affected to some degree by such factors as age, nutrition, year, sex, and type of birth. The index for ranking yearling males on the Texas Agricultural Experiment Station annual central performance test[7] has received wide acceptance in the Texas industry.

Pregnancy And Childbirth

Pregnancy And Childbirth

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