ABSTRACT:The objective of this study was to evaluate the effects of selection for increased size of testes on semen and testis characteristics. Boars from a line selected for increased size of testes at 150 d of age (TS, n = 25) and a randomly selected control line (C, n = 18) were used. Semen was collected three times per week for 3 wk (TRT1) then daily for 3 wk (TRT2) beginning when boar age averaged 276 d. It was followed by a 4-wk period of one collection per week and then the TRT1-TRT2 sequence was repeated. After 64 collections, boars were castrated and testes were evaluated for sperm numbers. Volume of semen, percentage of motile sperm cells, and percentage of abnormal cells in the semen did not differ ( P > .05) between lines. Concentration of sperm cells in the semen was greater for TS boars at TRT 1 (35.0 million cells/mL, P < .10) and TRT 2 (29.5 million cells/mL, P < .01). Number of sperm cells per ejaculate was greater for TS boars (6.1 and 4.3 billion cells for TRT 1 and TRT 2, respectively; P < .05). Percentage of abnormal cells was less ( P < .05) for boars at the younger ages. Concentration of sperm cells was 16 to 18 million cells/mL semen greater ( P < .05) at the older ages. Significant differences in the shapes of the response curves with increasing collection number across lines and ages were found. These differences were small and not considered to be important. Line differences in testicular and epididymal sperm numbers and in daily sperm production were consistent with differences in semen traits. Repeatabilities of semen traits were between .16 and .74. Selection for increased size of testes can be used to improve the reproductive capacity of boars used for artificial insemination.
Eighty crossbred gilts were assigned randomly to treatments: 1) removal of an ovary and ipsilateral uterine horn (UHO) at 130 d of age and removal of the remaining ovary and uterine horn 12 d post-puberty; 2) UHO at 130 d of age, mated and reproductive tracts recovered when slaughtered at 30 d of gestation; 3) UHO 12 d post-puberty, mated and slaughtered at 30 d of gestation and 4) unoperated controls that were mated and slaughtered at 30 d of gestation. Age of puberty was not affected by treatments. Gilts in treatment 1 had a mean ovulation rate at the pubertal estrus comparable to gilts in treatment 3. But, gilts in treatments 2 and 3 had 16% fewer (P less than .01) corpora lutea at 30 d of gestation than control gilts. Length and weight of the remaining uterine horn at 12 d post-puberty for gilts treated at 130 d of age were similar to the averages of gilts left intact. Gilts with one uterine horn had 2.2 fewer live embryos at 30 d of gestation than control gilts (P less than .01). But, the proportion of corpora lutea represented by live embryos did not differ significantly among treatments. Gilts with one uterine horn had 1.1 fewer live embryos (P less than .15) after adjustment for number of corpora lutea, less uterine space occupied by each embryo (P less than .01) and less total placental membrane per embryo (P less than .05) than control gilts.(ABSTRACT TRUNCATED AT 250 WORDS)
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