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Observations of 3,029 matings over 17 yr on an Ozark upland range were used to estimate heritability of pregnancy rate in Angus, Hereford and Polled Hereford cows. Pregnancy rate, the percentage of cows exposed that produced a live calf in the spring, was transformed using the empirical logit transformation and then analyzed for each breed separately by weighted least squares using a mixed model procedure. A numerator relationship matrix for sires of cows was incorporated into the sire model to account for relationships among sires. Variation among years significantly affected pregnancy rate in all three breeds. Age of dam significantly affected pregnancy rate in the Angus and Hereford groups. Paternal half-sib estimates of heritability from the observed binary data (h2b) for pregnancy rate were calculated on first-calf heifers and mature cows for each breed. Respective h2bestimates for heifers and mature cows were .17 and .09 in the Angus group, .04 and .01 in the Hereford group and .05 and .05 in the Polled Hereford group. The heritability estimates when binary records were transformed to the probit scale (h2) were .04 ± .003 and .02 ± .001 for Angus, .01 ± .002 and 0 for Hereford and .01 ± .001 and .02 ± .001 for Polled Hereford for heifers and mature cows, respectively. Heritability estimates in this study are in agreement with the literature, indicating little opportunity for improvement in pregnancy rate by selection within a breed.

Fifty-two weanling pigs from six litters(Pond et al., 1968) were fed a standard 18% protein corn-soybean meal diet from weaning to slaughter. The six litters were from gilts paired on the basis of parturition date so that one gilt fed the control diet and one fed the “protein-free” diet (0.5% protein) from week 4 of pregnancy to parturition made tip each pair. Each dam was fed the control diet throughout lactation and nursed one-half of her own litter and one-half of a pairmate's litter resulting from reciprocal transfer of one-half of each litter at birth. Individual bodyweight gains and feed consumption of each litter recorded from weaning to slaughter at 93 kg. revealed no differences associated with prenatal or preweaning treatment. Carcass backfat and cross-sectional area of the I. dorsimuscle between the 10th and 11th ribs also failed to reveal differences in carcass characteristics which could be considered as a crude index of muscle cell number as influenced by prenatal and early postnatal protein nutrition. It is concluded that in pigs the dam acts as an efficient “buffer” to at least partially protect the developing fetus against the effects of maternal protein deprivation during the final three-fourths of one gestation period.

A program was undertaken to eradicate atrophic rhinitis and virus pig pneumonia from the Cornell University swine herd. This consisted of breaking the cycle of infection by removing the pigs from their dams immediately after birth and raising them in isolation from other swine. Foundation animals were selected from pigs raised in this way and were mated by natural service to boars raised with them in isolation or by artificial insemination to regular herd sires. Pigs farrowed from these matings were raised in the conventional way, the only precaution being that of maintaining strict isolation from atrophic rhinitis- virus pneumonia- infected swine.Of 91 snouts and lungs checked from the main herd over a two-year period, 8 and 31 have been diagnosed positive for atrophic rhinitis and virus pneumonia, respectively, as compared to 0 and 0 out of 39 checked from the group raised in isolation.These preliminary data lend further support to the evidence that these two diseases are spread only by direct contact of infected swine with susceptible swine. This provides a means of simultaneously eradicating atrophic rhinitis and virus pig pneumonia from a swine herd under reasonably practical conditions.

The farrowing records of purebred litters from Berkshire, Chester White and Yorkshire sows for the 12-year period 1946–57 were examined.Highly significant breed differences (P<0.01) were found in average litter size, average live-pig birth weight, average number of mummified fetuses per litter, percentage of mummified fetuses, average number of stillborn pigs per litter and percentage of stillborn pigs. The average birth weight of live pigs exceeded that of stillborn pigs in all three breeds. The average litter weight was not statistically different among breeds. There was a significant (P<0.05) effect of year on average litter weight, but not on any of the other criteria considered.Single mummified fetuses occurred more frequently than two or more in a litter. Mummified fetuses were more prevalent in large than in small litters in the Chester White and Yorkshire breeds. The incidence of stillbirths increased with increasing litter size. The presence of mummified fetuses did not seem to be related to the occurrence of stillbirths.

Eighty-five Yorkshire and Berkshire × Yorkshire gilts were used in three experiments to determine the effect of the addition of a progesterone or estrogen derivative to the feed on the estrous cycle and on subsequent fertility. In experiment 1 the addition to the ration of 0.66 or 1.1 mg. of AMP per kg. of body weight for a 15-day period was effective in inhibiting estrus in all gilts during the feeding period. Twenty-one of 22 treated gilts showed signs of estrus within 1 week after hormone withdrawal. Some of the gilts in each group slaughtered 2 or 4 days following artificial insemination had a high incidence of cystic ovarian follicles, especially gilts on the 0.66 mg. level. The estrous cycle was synchronized to some degree at the second cycle following hormone withdrawal (21- to 33-day cycles). Conception at this estrus using natural service was 83.3%. Average litter size for the six gilts that farrowed in each of the control, 0.66-mg. and 1.1-mg. groups was 8.7, 10.2 and 7.8 live pigs, respectively.In experiments 2 and 3 the feeding of 16 mg. of MEE per gilt daily for 9 days, followed by feeding 1.32 mg. of MAP per kg. of body weight daily for 9 days, inhibited estrus in 29 of 31 gilts. Treated gilts showed typical signs of estrus, including swollen vulvas and behavioral changes, 3 to 8 days after hormone withdrawal in experiment 2 and 4 to 10 days in experiment 3. However, 2 of 11 treated gilts in experiment 2 and 5 of 20 in experiment 3 refused to accept the boar. First service conception of mated gilts was 81.8% for controls and 77.8% for treated gilts in experiment 2 and 100% for controls and 93.3% for treated gilts in experiment 3. Corresponding average litter sizes (live+stillborn pigs) were 8.1 and 8.9 in experiment 2 and 10.4 and 11.7 in experiment 3.