Search

The metabolism of boar semen differs in several respects from that of bull and ram. Anaerobically, boar spermatozoa convert fructose to lactic acid at a much lower rate than ram or bull spermatozoa, and under these conditions their motility is also characteristically small. Aerobically, boar spermatozoa convert fructose to lactic acid at the same or even lower rate, yet their motility is very high. This is due to the ability of boar spermatozoa to oxidize lactic acid with an efficiency as high as that encountered in ram or bull semen. Apart from lactic acid, boar spermatozoa are capable of utilizing aerobically a number of other substrates, including glycerol, pyruvic acid and acetic acid, but unlike ram spermatozoa, they lack the ability to oxidize sorbitol. Two other unusual features of the aerobic metabolism of boar semen are (i) an increase in oxygen uptake, which occurs after the semen has been stored in vitro, and (ii) the occurrence in the boar seminal plasma of an easily oxidizable substance which is responsible for the plasma's own oxygen uptake.

Eggs were recovered in vivoin a modified Tyrode's solution from 29 donor gilts and transferred to 27 unmated recipients. Ovulation time of donors and recipients was synchronized. Eggs from B donors were transferred to the left oviduct or upper uterine horn, and eggs from W donors were transferred to the right side in 18 gilts. When the uteri and fetal contents were examined at about 90 days of gestation, migration of one or more eggs from one horn to the other had occurred in all (14) of the pregnant animals. Mixing of embryos from the two different sides occurred in 9 of 11 gilts in which both B and W fetuses survived to examination.Eggs were transferred to one uterine horn only in nine gilts. Five of these nine were pregnant when examined at 21 days of gestation. Two had embryos in both uterine horns and three had embryos in only one horn.Of 263 eggs transferred 110 (42%) developed into fetuses. Of 184 eggs transferred to recipient gilts which were pregnant at examination, 60% had developed into fetuses. Egg transfer can be used effectively in studies on implantation and other aspects of swine reproductive physiology.

Latterly many new ideas and techniques leading to increased efficiency of production have been applied in different branches of agriculture. Among them, controlled breeding, if successful, could have a profound influence on efficiency and on certain management practices. The idea introduces for the first time the possibility of being able to plan and control the production of some of the larger farm animals, and planning is the key to success in any major industry.

The sequence of morphological changes in the nuclei of follicular oocytes in the pig has been examined after a single injection of human chorionic gonadotrophin (hcg), given during pro-oestrus.Oocytes remained in the germinal vesicle (dictyate) stage until 18 hr after injection of hcg. Chromatin condensation, followed by completion of prophase of the first maturation division, then occurred, and the chromosomes were arranged on the first metaphase spindle by 26 hr after hcg. From 26 until 34 hr after hcg, the chromosomes remained at first metaphase, but between 35 and 37 hr, anaphase, telophase and abstriction of the first polar body were completed. The great majority of eggs recovered from individual animals showed similar stages of maturation.

Chemical methods for the analysis of three characteristic constituents of seminal plasma, namely, fructose, citric acid and ergothioneine, were applied in an attempt to evaluate in a quantitative manner the participation of seminal plasma in the passage of sperm along the female reproductive tract of two species, the pig and the horse.At specified intervals after mating, the reproductive tract of the gilt and the mare, respectively, was exposed, the uterine horns and Fallopian tubes clamped into several segments and the contents of the isolated portions withdrawn for analysis.In the gilt, about 40 min after mating, the uterine horns were found to be filled with semen containing spermatozoa, as well as fructose, ergothioneine and citric acid, but 6 hr after mating the bulk of sperm and seminal plasma had disappeared. In the mare, 50 min after mating, spermatozoa, ergothioneine and citric acid were recovered from both uterine horns, in proportions resembling those found in fresh stallion semen.

Corpora lutea induced in pigs on Day 6 regressed with the naturally formed corpora lutea towards the end of the cycle. Hormonal induction of corpora lutea on Days 8, 10 or 16 significantly prolonged the cycle despite involution of the original corpora lutea about 16 days after ovulation. The interval between the exogenous administration of hcgand the appearance of the next oestrus varied with the day on which the accessory corpora lutea were formed. The estimated functional life span of the corpora lutea induced on Days 6, 8, 10 and 16 was 12·5 14·5, 15·0 and 19·3 days respectively. That these induced corpora lutea were fully functional was shown by the luteal progesterone levels estimated using the protein-binding and u.v. spectrophotometric techniques.Hysterectomy resulted in both the spontaneous corpora lutea and those induced on Day 6 being maintained for at least 60 days.It is concluded that Days 6 to 8 may represent a critical phase in the relationship between the uterus and the corpora lutea in non-pregnant pigs.

Polyspermy can be produced experimentally in pigs by delayed mating, which results in the fertilization of aged eggs (Pitkjanen, 1955; Thibault, 1959; Hancock, 1959; Dziuk & Polge, 1962; Hunter, 1967). A high incidence of polyspermy has also been observed in pigs following induced ovulation and insemination during the luteal phase of the oestrous cycle (Hunter, 1966). These observations suggest that the endogenous level of progesterone at the time of fertilization might affect the block to polyspermy in pig eggs, since, under both conditions cited, developing or fully functional corpora lutea would be present in the ovaries at the time of sperm penetration. The present study was conducted to determine the frequency of polyspermy in pigs injected with progesterone at various intervals before ovulation and fertilization.The experimental animals were thirty-six mature, crossbred, Large White × Essex,

Boar spermatozoa fertilized only a small proportion of the follicular and ovulated eggs that were transferred into the uterus of artificially inseminated gilts. The possibility that spermatozoa had entered the oviduct or were influenced by tubal secretions before penetration cannot be excluded. Sperm penetration in uterowas not observed when oviducts were ligated at the uterotubal junction before transferring eggs into the uterus.