Uterine Mass and Uterine Blood Volume in Mice Selected 21 Generations for Alternative Criteria to Increase Litter Size

Lines of mice, selected for 21 generations using alternative criteria to increase litter size, were evaluated for uterine mass and uterine blood volume to help explain differences in uterine capacity. For this study, mice were sampled from Generation 27, the sixth generation after relaxation of selection. Mice came from all four criteria of selection (LS = selection on number born to unaltered females; M = selection on an index of ovulation rate and ova success; UT = selection on uterine capacity; and LC = unselected control) in each of three replicates (a total of 12 lines). Measurement was at one of two stages, either 3 d or 6 d of gestation. Matings were at 10 wk of age, and a total of 508 mice (17 to 26 per line-day of pregnancy subclass) were measured. The mean of the three selected groups exceeded the control in uterine mass ( P \u3c .001), uterine blood volume ( P \u3c .002), uterine mass/body mass (P \u3c .03), and uterine blood volume/body mass ( P \u3c .04 ) but not in uterine blood volume/uterine mass. Greater uterine mass and concomitantly greater uterine blood volume may have been partly responsible for greater uterine capacity resulting from LS, M, and UT selections

Melengestrol Acetate at Greater Doses Than Typically Used for Estrous Synchrony in Bovine Females Does Not Mimic Endogenous Progesterone in Regulation of Secretion of Luteinizing Hormone and 17β-Estradiol

Our working hypothesis was that doses of melengestrol acetate (MGA) greater than those typically administered in estrous synchrony regimens would regulate secretion of LH and 17β-estradiol (E2) as endogenous progesterone (P4) does during the midluteal phase of the estrous cycle. We also hypothesized that endogenous P4 from the CL would interact with MGA to further decrease the frequency of LH pulses and E2. Cows on Day 5 of their estrous cycle (Day 0 = estrus) were randomly assigned to an untreated control group (CONT, n = 5) or to one of six MGA treatment groups (n = 5 per group): 1) MGA administered orally each day via a gelatin capsule at a dose of 0.5 mg MGA/cow with the CL present (0.5CL); 2) 0.5 mg MGA/cow daily in the absence of CL (0.5NO); 3) 1.0 mg MGA with CL present (1.OCL); 4) 1.0 mg MGA without CL (1.ONO); 5) 1.5 mg MGA with CL present (1.5CL); 6) 1.5 mg without CL (1.5NO). MGA was administered for 10 days (Day 5 = initiation of treatment). To regress CL, cows assigned to groups without CL received injections of prostaglandin F2α (PGF, 0; 25 mg) on Days 6 and 7 of their estrous cycle. All cows were administered PGF2α. at the end of the 10-day treatment period. During the treatment period, daily blood samples were collected to determine concentrations of E2. Serial blood samples were collected at 15-min intervals for 24 h on Days 8, 11, and 14 to determine pattern of LH secretion. Frequency of LH pulses on Days 8, 11, and 14 was greater (p \u3c 0.05) in cows without CL (0.5NO, 1.ONO, and 1.5NO) than in cows with CL (0.5CL, 1.OCL, 1.5CL, and CONT). Mean concentrations of LH were greater (p \u3c 0.05) in cows from the 0.5NO group on Days 8 and 11 and were greater (p \u3c 0.05) in cows from the 0.5NO, 1.ONO, and 1.5NO groups on Day 14 as compared to cows with CL. Overall mean concentrations of LH across Days 8, 11, and 14 were greatest (p \u3c 0.05) in cows from the 0.5NO group and were also greater (p \u3c 0.05) in cows from the 0.5NO, 1.ONO, and 1.5NO groups as compared to cows in the 0.5CL, 1.OCL, 1.5CL, and CONT groups. Mean concentrations of E2 during the treatment period were greater (p \u3c 0.05) in cows from the 0.5NO group than in cows from either the 1.ONO or the 1.5NO group; these values were also greater (p \u3c 0.05) in cows of the 0.5NO, 1.ONO, and 1.5NO groups as compared to cows of the 1.OCL and CONT groups. Therefore, we reject our working hypothesis because doses of MGA greater than those typically used in estrous synchrony protocols did not suppress LH and E2 to the same extent that endogenous P4 does. In addition, MGA treatment when CL were present did not result in a further suppression of LH pulse frequency or of E2 as compared to the values in control cows with functional CL

EC85-219 1985 Nebraska Swine Report

This 1985 Nebraska Swine Report was prepared by the staff in Animal Science and cooperating departments for use in the Extension and Teaching programs at the University of Nebraska-Lincoln. Authors from the following areas contributed to this publication: Swine Nutrition, swine diseases, pathology, economics, engineering, swine breeding, meats, agronomy, and diagnostic laboratory. It covers the following areas: breeding, disease control, feeding, nutrition, economics, housing and meats

Serum Cholesterol Concentration of Mice Selected for Litter Size and its Relationship to Litter Size and Testis Mass

This study assessed the genetic relationship between litter size and serum cholesterol concentration and between litter size and testis mass in mice. Mice were from a long-term experiment in which selection had occurred for 21 generations in three replicated lines per criterion of selection (LS = selection to increase litter size based on number born; LC = unselected control). Thereafter, random mating within lines was practiced. Serum cholesterol concentrations were evaluated in female and male mice from two replicates at Generation 29 and one replicate at Generation 30. Body weights and blood samples were collected from primiparous females 8 d after weaning their pups. Data from males were collected as they came out of breeding cages. In addition, the testes were excised, stripped clean of connective tissue and the epididymides, and weighed. Means for body mass of females and males, serum cholesterol, number born, and testis mass were as follows: 35.2 vs 32.5 g ( P \u3c .09), 33.9 vs 30.7 g ( P \u3c .08), 117.5 vs 110.5 mg/dL ( P \u3c .08), 14.0 vs 10.3 pups (P \u3c .04), and 126 vs 122 mg, respectively, for LS and LC. Serum cholesterol was greater in males than in females (133.3 vs 95.1 mg/dL; P \u3c .001), but there was no interaction between sex and selection criterion. Serum cholesterol concentration was not correlated phenotypically to number born or body mass, but it had a small negative relationship with testis mass. Therefore, we concluded that selection for litter size tended to increase serum cholesterol in addition to the increase in number born but did not change testis mass

EC83-219 1983 Nebraska Swine Report

This 1983 Nebraska Swine Report was prepared by the staff in Animal Science and cooperating departments for use in the Extension and Teaching programs at the University of Nebraska-Lincoln. Authors from the following areas contributed to this publication: Swine Nutrition, swine diseases, pathology, economics, engineering, swine breeding, meats, agronomy, and diagnostic laboratory. It covers the following areas: breeding, disease control, feeding, nutrition, economics, housing and meats