Wild Horse Populations Field Studies in Genetics and Fertility: Report to the Bureau of Land Management, U.S. Department of the Interior (1991) / Chapter Skim
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RESEARCH AND RESULTS
RESEARCH AND RESULTS
Pages 3-20
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From page 3... ...
Although the results from one remaining field season in the fertility study are not included in this report, the data gathered to date have been extensively analyzed and permit the conclusions presented in Chapter 5. GENETICS STUDIES Research on wild horse parentage and population genetics included a genetic analysis of the inheritance of different proteins present in red blood cells and serum.
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From page 4... ...
Blood samples were collected from 975 horses in five populations. Two sites had two trap locations each, providing paired subpopulations; the other three sites had one trap site each (Flanigan, 175 animals in 30 bands; Wassuks, 119 in 21 bands; Beaty Butte, 112 in 17 bands; Stone Cabin, 239 in 30 bands at site 1 and 127 at site 2; and Clan Alpine, 104 in 17 bands at site 1 and 99 in 12 bands at site 2)
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From page 5... ...
• The above data and the dendrograms support the hypothesis that Great Basin horses originated from escaped or released domestic draft, saddle, and cavalry animals. • Paternity assignments included 121 foals from 69 intact harem bands.
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1988. Wild horse parentage and population genetics.
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TABLE 2-3 Foal Paternity in Harem Bands Trap Site Per- PerTypeofBand F W B SCI CA1 CA2 Total cent Total" cent Harem bands 12 10 12 20 8 7 69 45 Bands, 1 stallion 9 4 10 12 6 1 42 23 Excluded for all foals 3 0 4 4 1 0 12 29 5 22 Sire of all 6 4 3 6 4 0 23 56 14 61 Sire of some, not all 0 0 3 2 1 1 7 26 4 27 Bands, 2 or more stallions 3 6 2 8 2 6 27 22 Excluded for all foals 2 2 0 0 0 2 6 22 4 18 One is sire of all 1 3 2 4 2 2 14 52 11 50 One is sire of some 0 1 0 4 0 2 7 25 7 32 Foals in band with stallion 18 11 23 40 16 13 121 80 Without qualifying sire 7 3 9 I5 2 4 40 33 24 30 NOTE: Study area designations are F, Flanigan; W, Wassuks; B, Beaty Butte; SCI, Stone Cabin/site 1; CA1, Clan Alpine/site 1; CA2, Clan Alpine/site 2. Stone Cabin/ site 1 was located in west central Nevada, Nye County.
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From page 9... ...
• At the time research began in the fall of 1985, no studies using remote delivery had achieved more than 1 year of fertility control, nor was any technology known that would allow multiyear dosage. • No dosage levels of remotely delivered female hormones were known.
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From page 10... ...
A seventh group of 30 mares was maintained as nonimplanted controls. A second experimental sequence on corralled horses was initiated in April 1986 involved the seven dosages listed below using one of the following methods: subcutaneous implants in the rump and flank areas, intermuscular implants, and intraperitoneal insertion.
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From page 11... ...
• Implants containing 36 g of progesterone plus 8 g of ethinylestradiol or implants containing 36 g of progesterone plus 24 g of estradiol-l7p with glycerol as a cosolvent effectively blocked ovulation for two breeding seasons in more than 60 percent of the mares. • Implants containing 8 g of ethinylestradiol without progesterone were capable of blocking ovulation for at least one breeding season.
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From page 12... ...
At the time of its development, the intraperitoneal approach was on the cutting edge of a rapidly developing technology. MARE FERTILITY CONTROL STUDIES IN THE FIELD Steroid implants in the field constitute the second component of the mare fertility control experiments.
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From page 13... ...
Methods Wassuks Study Area In January 1986, 41 mares, 3 years old and older, in the Wassuks area of west central Nevada were implanted with silastic placebo rods to serve as undosed comparison animals. These mares and those in the Clan Alpine area (described below)
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From page 14... ...
were seen with foals. Among an estimated 109 untreated mares with marker collars observed during the aerial observations, 51 (47 percent)
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From page 15... ...
Meanwhile, the placebo implants bore foals in 1989 at about the same rate as in 1988. (In the Wassuks data the 95 percent confidence intervals around the foaling rate of 70 percent in 1989 overlap the 95 percent confidence intervals for
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From page 16... ...
17 3 .00-. 12 progesterone Placebo 31 Stone Cabin Ethinylestradiol 35 Ethinylestradiol and 37 progesterone Wassuks Placebo 30 14 1 6 21 .45 .03 .16 .70 .27-.63 .00-.09 .04-.28 .53-.86 "The 95 percent confidence intervals were calculated by the formula/)
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From page 17... ...
'Clan Alpine treatments combined with placebo implants in 1988. with generally observed foaling rates of wild horses, and the difference between them and the hormone-treated mares is clear and consistent in all test areas.
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From page 18... ...
Methods The Flanigan and Beaty Butte areas were selected for the vasectomy experiments. In the Flanigan area in northwestern Nevada, dominant stallions from 20 bands were vasectomized and fitted with radio collars; 5 dominant stallions from 5 other bands were radio-collared and left intact as comparison animals; and 139 3-year-old or older animals from these 25 bands were given plastic marker collars.
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From page 19... ...
1988a. Fertility control in wild horses.
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From page 20... ...
But in the Beaty Butte area, in 1987 there were two bands with foals out of the five stable bands observed, and in 1988 there were three that contained foals out of the five stable bands that were observed that year. Other bands at Beaty Butte that were observed to include a vasectomized stallion during these 2 years were either unstable or stud bands.
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