Subsequent Gestation Research Articles

Influence of Energy Intake during Lactation on Subsequent Gestation, Lactation and Postweaning Performance of Sows

Influence of Energy Intake during Lactation on Subsequent Gestation, Lactation and Postweaning Performance of Sows

Effect of lactation length and fasting on various reproductive phenomena of sows.

One-hundred-seven Duroc sows were used to determine the effects of lactation length and postweaning fast on reproductive performance of weaned sows. The study involved lactation lengths of 21 or 30 days integrated with fasting periods of either 0, 2, 3 or 4 days. Effects of treatments on interval to estrus after weaning, number of corpora lutea and number of normal embryos present at day 25 of gestation, number of pigs born and number of pigs born alive per sow were determined. Within lactation group, length of fasting did not alter interval from weaning to estrus. Sows lactating 30 days returned to estrus in a shorter (P<.01) interval than did sows lactating 21 days (5.0 vs 8.2 days). Ovulation rate was reduced (P<.05) when sows were fasted 4 days after a 30-day lactation. Number of normal embryos was not affected by lactation length or fasting. Percentage embryo survival was not affected by fasting; however, sows lactating 30 days had better embryo survival, 79.0 vs 70.7%, when compared to sows lactating 21 days. Number of pigs born and number of pigs born alive were increased (P<.05) when sows lactated 30 days as opposed to 21 days. Fasting, after a 30-day lactation, significantly reduced the number of pigs born and number of pigs born alive. It would appear that postweaning fasting has no beneficial effect on ovulation rate, number of total embryos or percentage embryo survival, nor does it reduce the interval to first estrus after weaning. Also, 30-day lactation lengths resulted in improved sow performance in the subsequent gestation.

Thyroid function in human pregnancy: IX. Development or retardation of 7-year-old progeny of hypothyroxinemic women

Progeny of women, whose thyroid function was studied gestationally, had psychological and/or neurologic examinations at 8 months, 4 years and 7 years of age. In more than 100 pregnancies (at least 3 per cent of total pregnancies) hypothyroxinemia occurred and was treated adequately or inadequately. Children were delivered after uncomplicated pregnancies (except hypothyroxinemia), had birth weights of at least 2,500 grams, and were excluded when postnatal insults intervened. At 8 months and 4 years progeny of inadequately treated hypothyroxinemic women had the lowest psychological scores. Now 246 7-year-old children have been examined psychologically and neurologically (earlier data on only 101). Definite trends and a few statistically lower psychological scores of progeny of inadequately treated hypothyroxinemic pregnant women are compared with better psychological scores of 7-year-old children born to euthyroid and adequately treated hypothyroxinemic women. In six sibling sets outcome was better when hypothyroxinemic women were treated with adequate thyroid replacement therapy. If a woman has a poor reproductive history, early in a subsequent gestation, thyroid status should be examined and adequate thyroid medication considered seriously.

The reproduction of the African elephant, Loxodonta Africana

Between December 1946 and December 1948, and January to March 1950, 150 elephants made available in the course of control work carried out by the Uganda Game Department were examined in greater or less detail according to circumstances. Eighty-one were females, of which sixty-seven were adult and thirty-one had an embryo in the uterus. All the dissections were carried out in the field, and the present account includes observations on the terrain, the food of the elephant, and other aspects of its ecology. Linear measurements of the carcasses and photographs of the molar teeth provide a guide to the age of specimens. Tusk growth is nearly similar in males and females until puberty, after which those of females generally cease to grow. The reproductive organs of the male are briefly described; those of the female are described in more detail, and discrepancies between existing accounts are considered in the light of this relatively extensive series of specimens. The mode of formation of the ovarial sac is unusual and is described from foetal, neonatal and adult specimens. There is marked hypertrophy of the interstitial tissue of the foetal gonads during the later stages of gestation. Breeding occurs at all times of year, but mating is possibly more frequent in the period December to March than at other times. Both sexes reach maturity at 8 to 12 years, and the female continues to breed until old age. Parturition is followed by a lactation anoestrus, after which the female undergoes a number of brief oestrous cycles until pregnancy ensues, lactation being continued throughout the subsequent gestation period. The interval between parturition and subsequent conception is normally of the same order of duration as the gestation period, and the normal calving interval appears to be rather less than four years. The ovarian cycle of the adult is characterized by the occurrence of multiple ovulation and the presence of many apparently active and histologically indistinguishable corpora lutea in both ovaries at all the stages of pregnancy which were encountered. It is probable that the corpus luteum of pregnancy develops from one of a number of follicles which ovulate under the same hormonal stimulus, and that it persists together with the accessory corpora lutea, some of which arise from follicles which ovulate and some from follicles which luteinize without ovulating. The corpora lutea are replaced about mid-pregnancy by a second set, which are formed by the luteinization of all the follicles with antra in both ovaries; some at least of the larger ones ovulate while many smaller ones do not. Follicular growth is suppressed in the later stages of pregnancy. The cycle of events bears some resemblance to that which occurs in the mare, and the comparison is discussed in detail. The ovarian periphery is characterized by numerous subsurface crypts and papillose projections which increase the area of the germinal epithelium. A description of the placenta and foetal membranes is in preparation, and preliminary study reveals a striking similarity to Hyrax , particularly in the quadri-lobulate allantois. The findings are discussed with reference to the phylogenetic position of the genus, the probable role of the corpus luteum in pregnancy, and the significance of the results in relation to the conservation of existing wild elephant populations.