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Forty-eight second, third and fourth parity crossbred sows were randomly allotted to four dietary treatments: corn:alfalfa-orchardgrass hay (46%; CH); CH plus lasalocid (CHL); corn-soybean meal (CS) or CS plus lasalocid (CSL). Sows were fed these diets through two successive gestations with dietary treatment initiated at 35 d post-coitum and continued until parturition. To equalize daily metabolizable energy intake (6.6 Mcal/sow), 2.64 kg of CH and CHL diets and 1.86 kg of CS and CSL diets were fed. Lasalocid intake was 130 mg · sow−1· d−1. Sows were weighed and backfat measurements were taken at 35 and 109 d of gestation. Sows also were weighed 14 d postpartum. A 14% crude protein corn-soybean meal diet was fed ad libitum to all sows during lactation and feed intake was recorded. Colostrum samples were obtained within 4 h of farrowing. All live piglets were weighed at birth and 14 d of age. There were no significant differences among dietary treatments in number of live piglets born, piglet birth weight, piglet weight at 14 d of age or sow rebreeding efficiency. Sows fed CHL and CSL diets had more (P<.12) live piglets at 14 d postpartum and lower (P<.03) total fat in colostrum than did CH- and CS-fed sows. Alfalfa-orchardgrass hay feeding resulted in less (P<.04) backfat deposition during gestation, more (P<.04) weight loss from 109 d postcoitum to 14 d postpartum and increased (P<.002) feed consumption during lactation. These results indicate that the corn:alfalfa-orchardgrass hay (46%) diet was essentially equal to the corn-soybean meal diet with regard to sow reproductive performance. Dietary lasalocid reduced fat percentage of sow colostrum.

Fourteen market-weight pigs of each breed, Hampshire and Chester White, were used to estimate the fraction of lactose in a 40% dried whey diet (30% lactose) which becomes available for microbial fermentation in the cecum and colon. Approximately 32 and 30% of the lactose consumed in a 1-hr feeding flowed into the large intestine over the ensuing 5 hr in Hampshire and Chester White pigs, respectively. The emptying rates of Cr-EDTA from the stomach were higher than for dry matter during the first 3 hours. However, lactose and Cr-EDTA left the stomach at the same rate. More than 70% of the Cr-EDTA consumed had passed into the large intestine by 5 hours. The pH of cecal and colonic contents decreased (P<.05) with time after feeding and the dry matter of the colonic contents also decreased (P<.05) with time after feeding. These results indicate that a substantial fraction of lactose is available for microbial fermentation in the large intestine of pigs fed a diet containing high levels of lactose.

Two 21-day feeding trials were conducted using either 24 Hampshire (H) or 24 Chester White (CW) pigs at approximately 5 months of age to evaluate the effects of a diet containing 40% dried whey on the performance and the lactase activities in the gut of finishing pigs. Dried whey increased the incidence and severity of diarrhea in both CW and H (P<.005) but depressed the rate of gain, gain/feed, and feed intake (P<.005) only in H. The pigs were slaughtered on day 19, following a 12-hr fast (0 hr), or at 1, 2 or 3 hr after consuming approximately 150 g of lactose from 500 g of the dried whey diet. Previous dietary treatment did not affect the rate at which lactose left the stomach or the recovery of lactose in the small intestine except for a diet × segment interaction (P<.05) in H where more lactose was recovered in the lower one-third of the intestine of the controls. Total mucosal and contents lactase activities in the small intestine were not altered by diet but total cecal lactase was increased (P<.05 H; P<.005 CW) in the groups fed dried whey. Times after feeding did not affect lactase activities in CW but in H the 0 hr group had lower (P<.005) total mucosal activity than the 1-, 2-, or 3-hr groups. The lactase activity in the contents of the intestine of H fed dried whey was greater (P<.05) than that of the controls.

Cholesterol utilized for steroid synthesis by ovarian tissue may be derived from de novo synthesis or cellular uptake of lipoprotein cholesterol. The majority of blood cholesterol is transported by either low (LDL) or high (HDL) density lipoproteins, depending on the animal species. Prior to vascularization, only HDL are in follicular fluid and contribute sterol to granulosa cells because other lipoproteins are unable to traverse the basement membrane due to their molecular masses. Following vascularization, both LDL and HDL bathe luteal cells. Most species preferentially use LDL cholesterol as a precursor for ovarian steroid synthesis. The LDL uptake by ovarian tissue occurs by receptor-mediated endocytosis. The receptor recognizes apolipoprotein B of LDL and apolipoprotein E found on some, but not all, HDL. Within a species, a positive relationship may exist between HDL apolipoprotein E content and importance of HDL cholesterol as a precursor for steroidogenesis. A “HDL pathway” exists for uptake of sterol from HDL void of apolipoprotein E. The HDL receptor exhibits broad binding specificity. Unlike LDL, the HDL particle is not internalized, and cholesterol preferentially is taken up relative to other HDL constituents. In most species, lipoproteins, rather than de novo synthesis from acetate, contribute the majority of cholesterol used for steroid production. Trophic hormones increase lipoprotein binding, internalization, degradation and conversion of lipoprotein-derived sterol to steroids, effects that are mediate through cyclic adenosine monophosphate. Knowledge recently acquired regarding lipoprotein sterol utilization by the ovary may be useful in developing nutritional, pharmacological or endocrine manipulations that may positively affect cholesterol clearance by the ovary, steroidogenesis and reproductive performance.

Summary.Interactions of bovine follicular fluid glycosaminoglycans (GAGs) with extracellular matrix (ECM) components fibronectin and laminin and with low-density lipoproteins (LDL) were examined using affinity chromatography. Glycosaminoglycans from small (diameter < 5 mm) and large (diameter 11–20 mm) follicles were isolated from follicular fluid. The dermatan sulphate or heparan sulphate from small or large follicles was applied to Fn–, Lm– or LDL–Sepharose columns. Portions of each fraction of the bound or unbound GAG were then subjected to gel filtration h.p.l.c. for quantification. The binding interaction between dermatan sulphate and fibronectin was significantly greater than between heparan sulphate and fibronectin (P< 0·05); the binding interaction between GAGs from small follicles and fibronectin was significantly greater than between GAGs from large follicles (P< 0·05). The binding interaction between GAGs from small follicles and laminin was significantly greater than for GAGs from large follicles (P< 0·05). Dermatan sulphate from small follicles bound to fibronectin (42%), laminin (36%) and LDL (14%) and that from large follicles bound to fibronectin (14%), laminin (23%) and LDL (14%). Heparan sulphate from small follicles bound to fibronectin (17%), laminin (15%) and that from large follicles bound to fibronectin (13%), laminin (10%) and LDL (6%). These results suggest that dermatan sulphate, but not heparan sulphate, from follicles at different stages of development exhibit a varied ability to interact with components of the ECM. Both substances bound to LDL comparably in small amounts.Keywords:follicle; glycosaminoglycans; fibronectin; laminin; extracellular matrix; lipoproteins; cow

Two experiments were conducted to determine the relationship of dietary particle size to the formation of gastric lesions in growing-finishing swine. The first experiment consisted of 2 trials of Latin square design using fundic-pyloric fistulated pigs to study the effect of particle size of corn on pH and pepsin activity of gastric contents. With cracked corn, pepsin activity and acidity were higher in both ad libitumfed pigs and in pigs fed once daily than when fine corn was fed. The results of this experiment with fundic-pyloric samples are opposite those obtained previously in slaughter experiments ill which entire stomach contents were sampled. This apparent disagreement was shown in Experiment 2 to be due to the localized area of the stomach from which the samples were taken in Experiment 1 and a lack of mixing of gastric contents in pigs fed cracked, but not fine corn. In Experiment 2, 60 pigs were fed once daily for 7 days and on the seventh day pigs were slaughtered at the following time intervals after feed removal: 0, 4, 8, 13 and 24 hours. The stomachs were removed in a manner to minimize mixing, then frozen and divided into esophageal, fundic and pyloric regions. The contents from each region were removed, weighed and analyzed for percent moisture, pepsin activity, pH and osmolality. When cracked corn was compared to fine corn, pH was higher in the esophageal region and the opposite result was observed in the pyloric region of the stomach. After 4 hr. pepsin values in the esophageal region were much lower for pigs fed cracked corn, an effect not consistently observed in the pyloric region. For pigs fed cracked corn, percent moisture was lower in all regions and osmolality tended to be higher in the esophageal region and lower in the pyloric region. An increased rate of passage was also observed when fine corn was fed. Histamine content of the fundic mucosa did not vary with diet or time after feeding. It is suggested that the increased incidence of esophagogastric ulcers observed when fine corn is fed is mediated by increased acidity or increased pepsin activity or both in the relatively unprotected esophageal region of the stomach. These effects are probably brought about by more mixing of gastric contents as a result of a greater fluidity.

Four experiments were conducted with 206 pigs, fed four corn-based diets differing only in fineness of grind of the corn, to study the effect of dietary particle size on the development of gastric lesions. In three of the experiments a decrease in particle size resulted in a significant increase in the incidence of lesions. Keratinization was the predominant lesion, but erosions and ulcers were also observed, particularly in pigs fed finely ground corn. In a fifth experiment, pigs that were changed from fine corn to cracked corn for 40 hr. prior to slaughter had significantly fewer gastric lesions than did pigs which continued to receive finely ground corn. Decreasing particle size of corn resulted in an increase in the hexosamine content, percent moisture, fluidity and pepsin activity, and a decrease in the weight and osmotic pressure of the gastric contents, but no change in pH. Gastric lesions were associated with fluid-appearing ingesta. Fluidity was dependent on percent moisture and to some extent on the water-binding capacity of the insoluble portion of the ingesta. The results indicate that the effect of dietary particle size on gastric lesions was caused by an alteration in pepsin activity, fluidity, or both, and notby a decreased secretion of mucins or an increased secretion of acid. The mechanism whereby particle size alters these parameters was not elucidated.

This project was developed to investigate the possibility of employing early postnatal nutritional manipulation as a means of changing the final fat mass in swine. Restricted feed intake during the suckling period exerted little effect on the adipose cell number and cell size of subcutaneous, viscera and bone fat of the pig, thus giving no appreciable differences in total fat mass between controls and underfed pigs at a constant body weight of 80 kilograms.Restricting nutrition soon after birth did have an effect on the development of intramuscular fat tissue, resulting in lower marbling scores, lower percent ether extractable lipid in muscle and a lesser amount of total intramuscular fat in underfed pigs. This difference was caused by fewer and smaller cells in underfed pigs, indicating that the nutritional manipulation appeared to change the cell population in this particular adipose site of the pig.This differential response of adipose sites to early nutrition led to a postulate that the intramuscular adipose tissue is the latest developing tissue with some portions of preadipocytes differentiating and developing after birth and thus is under the influence of early nutrition to a greater extent than other adipose tissues.From these findings, it is suggested that the restriction of caloric intake during the suckling period cannot be employed to reduce fat content of market swine.

The effect of early nutrition on the development of adipose tissue was studied to investigate the possibility of employing nutritional manipulation as a means of changing the final fat mass in swine. Poland China and Duroc pigs were subjected to severe caloric restriction during the suckling period, and their carcass traits and adipose cellularity were compared to full-fed control pigs at 24 weeks of age.The underfed pigs showed a significantly lower dressing percent, greater proportion of bone tissue, significantly lower proportions of subcutaneous fat and less backfat thickness. They also had a significantly less absolute and relative quantities of ether extractable lipid in subcutaneous, muscle, viscera and bone tissue. All these findings indicated that the restricted feeding during the infantile stage retards the development of body tissue. This was especially true for those later developing tissues, which produced a more premature body composition at a given chronological age.The significantly lesser amount of subcutaneous fat mass in underfed pigs was explainedsolely by significantly smaller cell size and not by the number of adipose cells. In contrast to subcutaneous depots, the significantly less intramuscular fat in underfed pigs was due to a smaller number of adipose cells as well as smaller ceil size than controls, indicating that the nutritional manipulation could change the cell population in this particular adipose site.

The objective of this study was to measure the influence of live and carcass shape on composition. Twenty-four steers and 16 gilts were selected to represent two species and to equally represent two distinct shapes (muscular and non-muscular). An attempt was made to visually standardize live weight, degree of fatness and chronological age at the time of live selection and because of certain errors in subjective appraisal, it was necessary that the influence of these variables be held constant by statistical procedures. The bovine pelvic limbs and the entire porcine carcasses were dissected into bone, skin, fat and muscle. All individual muscles and muscle groups were analyzed for ether-extractable lipids.The results provided the following conclusions:Non-muscular animals were considerably fatter than anticipated when evaluated subjectively and muscular ones were slightly thinner than anticipated.Even though ingesta and fatness were not standardized, muscular animals appeared to yield proportionately heavier carcasses, i.e., have higher dressing percentages.Muscular animals contained approximately 2% more fat-free muscle and this was due primarily to a one unit higher muscle-bone ratio. This indicates that the relationship of muscle and bone is not necessarily constant for meat animals.Regardless of the tendency for a few muscles to be proportionately larger, in most instances the majority of muscles and bones represented a constant proportion of the total muscle and skeleton mass respectively for the pelvic limbs and carcasses studied.After the effects of weight and fatness were held constant, the yield of various anatomical parts of the carcass were similar for both shape groups. Therefore, such measures as percent ham and loin are a direct reflection of fatness and are not affected by degree of muscularity.Animal or carcass shape is a significant factor in determining composition but its role is minor when compared to fatness. The importance of muscularity may be overlooked when carcass composition is determined by such techniques as specific gravity or proportion of trimmed wholesale or retail cuts in which bone is not removed and thus permitted to influence the net result.

Three experiments were conducted to determine the effect of dietary histidine and histamine on zinc deficiency in baby pigs fed an isolated soybean protein-based, semi-purified diet. One percent supplemental histidine (exp. 1) or 0.2% supplemental histamine (exp. 1) did not improve growth rate but had a beneficial effect on skin lesions. Two percent supplemental histidine (exp. 2 and 3) markedly decreased the incidence and severity of skin lesions of zinc deficient pigs but did not improve growth or increase serum alkaline phosphatase activity or zinc concentration of bone, liver, skin (exp. 3) and serum. Two percent supplemental histidine significantly increased whole blood and serum (exp. 3) histamine concentrations. Supplemental zinc prevented all signs of zinc deficiency in all experiments but did not significantly affect histamine concentration of the tissues analyzed. The data indicate that histidine alleviates the skin lesions of zinc deficient pigs by a mechanism other than increasing zinc availability, and that its effect may be mediated by conversion to histamine.

Two experiments involving 76 weanling pigs were conducted to determine the effect of a histidine-rich protein (blood meal) on the zinc-deficiency syndrome in weanling pigs. A high-calcium, corn-soybean meal diet produced severe zinc deficiency. Twenty percent blood meal added at the expense of corn prevented substantial skin lesions, maintained normal serum alkaline phosphatase activity and maintained normal serum, bone and liver zinc concentrations. Blood meal did not increase the zinc content of the diet (i.e., it contained about the same amount of zinc as did corn). Ten percent blood meal caused a response in the same direction as 20% blood meal, but its effect was not as pronounced. One hundred ppm supplemental zinc prevented all signs of zinc deficiency except mild, transient skin lesions. The zinc present in the blood meal diets appeared to be more available than the zinc present in the non-blood meal diets. However, high histidine content of blood meal diets may have alleviated certain signs (parakeratosis) of zinc deficiency by a mechanism other than increasing zinc availability.

The extent of mixing in vivoof the stomach contents of swine fed cracked versusfinely ground corn was assessed by labeling the body water pool with tritiated water and measuring 4 hr. later the specific activity of the water in 17 different regions of the stomach contents. Pigs fed the fine corn diet had a uniform distribution of tritiated water throughout the stomach contents while those fed cracked corn showed a marked gradient in specific activity of stomach water with the lowest values occurring in the esophageal region of the stomach. A gradient in pH was also observed in pigs fed the cracked corn, but not in those fed the fine corn diet. The percent moisture of stomach contents was lower in all regions of the stomach when cracked corn was compared to fine corn.These data demonstrate that stomach contents from pigs fed finely ground corn undergo more extensive mixing in vivothan those from pigs fed cracked corn, probably as a result of the greater fluidity of the contents. This increased mixing of stomach contents allows the secreted acid and pepsin from the lower part of the stomach to come into contact with the relatively unprotected esophageal mucosa. This may lead to the increased incidence of esophagogastric ulcers and related lesions associated with the feeding of finely ground diets.

Data on six lines of inbred swine and on the two-, three- and four-line crosses between them and on the results of using these in topcrosses are compared for their predictability from one mating system to another. The following appeared to have predictive value: Pig weaning weight in inbreds with two-line crosses classified by dam-line; pig 5-month weight in two- and three-line crosses and topcrosses classified by sire-line with each other; and the ratio of 5-month to 56-day pig weights in inbreds with 5-month weight in two- and three-line crosses and topcrosses classified by sire-line.Subdivision of variance in the two-line crosses for 56-day pig weights indicated that maternal effects are more important than general combining ability and that the opposite is true for 5-month pig weights. Neither showed evidence of specific combining ability. It was also indicated that there was a negative genetic correlation between the additive effects in the pig and the maternal effects of the line.Possible applications of the results to the genetic improvement of swine are discussed.

Results are presented from an experiment in which inbred lines of swine were tested in linecross and topcross combinations in an experimental breeding herd and in which inbred and linecross boars were compared with outbred boars in two-sire farm herds. Data from 270 litters farrowed in 4 years were studied in the first part of the experiment. The farm top-cross tests involved a total of 1648 litters in 93 herds over an 8-year period. The data from 228 litters in 14 of these herds were analyzed separately because the effect of topcrossing could not be separated from that of crossbreeding.These results showed that linecrossing resulted in a recovery of the vigor lost during inbreeding, but showed no average advantage for the linecrosses over outbred controls. This latter is in contrast to results obtained in some other experiments which have shown linecrosses to be superior to outbred purebreds.Topcrosses by inbred boars of predominantly Landrace breeding were significantly heavier at 5 months of age than non-topcrosses in the same herds. The actual difference was 11 lb. No other topcrosses by inbred boars showed any significant advantage in viability or rate of gain.Topcross gilts by inbred boars were consistently superior to their controls in size and weight of litters raised to 5 months. Results from 27 herds showed significant increases for the topcross gilts of 1.0 pig and 156 lb. in these two traits, respectively.There was an indication that inbred and linecross boars differed in their performance in topcrossing. Progeny of two-line cross boars showed a significant advantage in viability and quite large increases in pig and litter weights, whereas progeny of inbred boars of the parent lines showed no increase. In productivity comparisons, the gilts by inbred boars were superior to their controls, whereas gilts by linecross boars were not.More general implications of these results and of the effects of the inbreeding and selection practiced in the development of the lines will be considered in a subsequent paper.

A RENEWED interest in inbreeding as a means of improving livestock followed the rapid expansion of knowledge of genetic principles and the success of hybrid corn. This was one of the factors leading to the development of cooperative research on swine breeding methods between the U.S.D.A. and several midwest state experiment statioIls. Most of the efforts of the workers in this Regional Swine Breeding Laboratory during the first 15 years were devoted to developing and testing inbred lines, in order to measure the effects of inbreeding, the effectiveness of selection in offsetting the effects of inbreeding, and the performance of linecross and topcross offspring of the inbred parents.The Wisconsin Station developed and tested in various crosses five inbred lines, namely, three Chester White, one Yorkshire and one based on a cross of these two breeds. This report summarizes the data from this project on the effects of inbreeding and of the selection practiced in conjunction with this inbreeding.

The effects of various methods of feeding on the development of parakeratosis in growing swine were studied. “High calcium” rations were fed. Ad libitum-feeding, dry (self-feeding) was the most detrimental, while a combination of wetting the feed and supplying limited amounts of feed only twice a day (hand-feeding, wet) significantly stimulated body weight gains and reduced the severity of the parakeratotic skin lesions. Neither ad libitum-feeding, wet nor hand-feeding, dry alone had much beneficial effect on parakeratosis or on weight gains. Although in this study hand-feeding, wet proved beneficial, the response was significantly less than that obtained by supplementing the ration with 100 ppm of zinc. Altering the method of feeding did not affect weight gains or produce skin lesions in pigs receiving 100 ppm of supplemental zinc. This suggests that hand-feeding, wet may increase the availability of natural dietary zinc for the control of parakeratosis.Experiments performed in vitro demonstrated that zinc was readily removed from solution during the precipitation of calcium phosphates brought about by increasing from 3 to 6 the pH of solutions of calcium, phosphate and zinc. These conditions simulate somewhat the change in pH of ingesta during its passage from the stomach of the pig into the small intestine. Decreasing the Ca:P ratio of these solutions by varying the phosphate concentration markedly decreased the amount of zinc removed from solution. Possible relationships of zinc binding by calcium phosphates to the antagonistic effects of high dietary calcium on parakeratosis in swine and to the beneficial effect of hand-feeding, wet were discussed.

It has been amply demonstrated that parakeratosis of swine (Kernkamp and Ferrin, 1953) is adversely affected by feeding excessive amounts of calcium and is greatly alleviated by feeding supplemental zinc (Tucker and Salmon, 1955; Luecke et al., 1956; Lewis et al., 1956). Therefore, two possible methods of controlling this disease are apparent: (1) restricting the calcium intake, or (2) feeding supplemental zinc. A previous report (Lewis et al., 1956) indicated that pigs fed 0.8% calcium (and 0.5% phosphorus) readily developed parakeratosis, but not so rapidly as did pigs fed 1.1–1.4% calcium. Furthermore, the zinc content of a number of body components of swine fed the two levels of calcium with no added zinc was not significantly different. It appeared desirable to compare the effects of feeding a minimum level of calcium (i.e. slightly below the National Research Council (1953) recommendation) on the development of parakeratosis and on the zinc concentration of several body components with those observed from feeding higher levels of calcium.Previous experiments showed that 50 ppm of supplemental zinc in a ration containing 0.8% calcium did not completely prevent parakeratosis, but that 100 ppm of supplemental zinc effectively alleviated or prevented the disease (Lewis et al., 1956). Since zinc might be toxic at high levels it was deemed advisable to establish a safety margin.The purpose of this paper is to present data showing the relative effects of three levels of calcium feeding (0.5%, 0.8% and 1.2%) and two levels of zinc supplementation (100 ppm and

The incorporation of the fibrous feeds, corn cobs or alfalfa hay, into swine rations significantly decreased dressing percentages, carcass fatback thicknesses and leaf fat weights. The percentages of skinned ham, ham muscle and lean cuts were increased in the carcasses of restricted-fed pigs. The highest grading carcasses were obtained from pigs fed the basal ration and those fed 62% and 69% TDN with corn cobs and alfalfa hay respectively. However, the pigs from the latter two lots were leaner and yielded more desirable carcasses than those fed the basal ration. Gilts produced significantly leaner carcasses than barrows. No significant differences were observed between treatments for areas of the longissimus dorsi muscle, ham butt or the percentage belly.Length from snout to hind foot, length of hind leg and length of ham were significantly longer in the carcasses from restricted-fed pigs. No signifiicant differences for length of carcass were observed between treatments. The percentages of viscera from pigs fed the lower TDN levels were significantly higher than those from the basal lot. The moisture content of the longissimus dorsi muscle and the iodine number of the fatback from carcasses of pigs fed 62% TDN with alfalfa hay exceeded all other lots and they were significantly higher than pigs fed the basal ration. Intra-muscular fat was not significantly affected by treatment. The leanest carcasses were produced from pigs fed 62% TDN with alfalfa hay; but carcass quality and grade were decidedly inferior to other lots.

Restricting the TDN level by incorporating fibrous feeds into swine rations significantly decreased average daily gains. Feed consumption per 100 lb. gain was increased by restricting the digestible nutrients of the ration, but TDN consumed per 100 lb. of gain was essentially equal in all lots, except lot 8. Significant differences were observed between the pigs of the basal and hand-fed lot for the number of days on experiment and average daily gain. More efficient gains were also obtained in the hand-fed lot. No significant differences were found between protein levels.The level of crude fiber in the ration was found to be more highly correlated with the results of growth and carcass data than either TDN or protein level. The differences between treatments were not significant when the crude fiber content of the ration was less than 10%. In lot 8 pig performance was more severely affected by the high level of fiber or low TDN content of the alfalfa hay in the ration than the 70% restriction of the hand-fed lot.

Observations were made during four years on the age at puberty in gilts in the swine breeding experimental herd maintained by the Wisconsin Agricultural Experiment Station in cooperation with the Regional Swine Breeding Laboratory. The numbers of gilts used were, in 1950, 150; 1951, 106; 1952, 95; 1954, 162. The mean age at puberty of the inbred gilts in 1950 was 227.7 days. They were significantly older at puberty than the line-cross gilts (193.5 days).The mean ages at puberty for the gilts representing the four systems of mating in 1951 (inbred, 244.0; two-line cross, 214.5; three-line cross, 198.4; four-line cross, 208.2) differed only in respect to inbreeding and line crossing, with no significant difference between the different line crosses.Inbreeding of a gilt was shown to have a significant effect on the age at which she reached puberty. The effect of inbreeding of the dam was not shown to have a significant effect on the age at puberty of her off-spring.Significant differences were found between the inbred and line-cross gilts when classified into 154-day-weight classes to remove much of the effect of differences in growth rate.The 1952 studies indicated a significant difference between purebreds and crossbreds. Differences between different line crosses were non-significant, as they were in 1951.Differences in age at puberty in 1954 were found between mating types within the purebred and crossbred systems of mating as well as between the two systems.Differences shown between the average age at puberty of the reciprocal crosses between two breeds and the average age at puberty of their purebred parents suggest non-additive inheritance.

Parakeratosis of swine was antagonized by adding 2% bone meal to a basal ration and was greatly alleviated by the supplementation of the ration with SO ppm of zinc as zinc sulfate.Zinc supplementation had no effect on the zinc content of packed erythrocytes, spleen, intestine, or pancreas.Adding zinc to the ration increased the zinc concentrations in blood plasma, liver, and kidney.When nosupplemental zinc was fed, the addition of 2% bone meal to the ration did not significantly alter the zinc content of erythrocytes, blood plasma, liver, kidney, spleen, intestine, or pancreas.When 50 ppm of additional zinc was fed, supplementation of the ration with 2% bone meal decreased the zinc concentrations of liver and kidney, but had no significant effect on the amount of zinc present in erythrocytes, spleen, intestine, or pancreas.The addition of 2% bone meal to the ration had no effect on the pH of the contents of the upper or lower small intestine or the large intestine, but in this experiment appeared to slightly increase the pH of the stomach contents.Zinc supplementation appeared to slightly lower the pH of the contents of the large intestine but had no consistent effect on the pH in the stomach or in the upper or lower portion of the small intestine.

The effects of adding an antibiotic, better quality protein, calcium, phosphorus or zinc to rations of pigs on the development of parakeratosis were studied. The basal ration, composed of corn, soybean meal, meat scraps, limestone and salt, contained 15% protein, 0.82% calcium, 0.47% phosphorus and 35 ppm of zinc. The addition of an antibiotic or better quality protein had no significant effect on weight gains or the incidence and severity of parakeratosis. High calcium rations (1.1 or 1.4% calcium) with the additional calcium being supplied by bone meal, limestone or dicalcium phosphate greatly decreased weight gains and increased the onset of parakeratosis when compared to the basal ration. A monosodium phosphate supplemented ration had no significant effect on weight gains but significantly decreased the skin lesions of pigs when compared to pigs fed the basal ration. The addition to the ration of 50 ppm of zinc as zinc sulfate greatly reduced the incidence and severity of parakeratosis but did not completely prevent the appearance of this disease. The addition of 100 ppm of zinc to the ration of pigs with established cases of parakeratosis produced immediate and dramatic responses in weight gains and essentially eliminated the skin lesions within a 9-week period of treatment. The addition of 500 ppm of zinc to the ration did notelicit a better response than the 100 ppm level of zinc. Parakeratotic pigs injected with inorganic zinc (ZnSO4·7H2O) responded similarly to those fed zinc, but the injections caused severe local irritation.

An experiment has been conducted on 10 gilts which were given intramuscular injections of 3 mg. of diethylstilbestrol in corn oil on either the 6th, 11th, or 16th day of the estrual cycle. Injections on the 11th day were observed to lengthen the estrual cycle significantly, (apparently due to luteinization of follicles), while injections on the 16th day were variable in effect but most frequently caused a significant shortening of the cycle. Injections given on the 6th day of the cycle had no apparent effect. The average lengths of the completed cycles were 19.78, 25.60 and 17.75 days for those in which the injection was made on the 6th, 11th or 16th day, respectively. The corresponding recovery cycles were 19.00, 19.67 and 19.86 days.

Gilts of the Chester White (CW) and Poland China (PC) breeds were subjected to different sequences of feed levels; either self-fed (F) or hand-fed at ⅔ the full-fed rate (L) in each of two years to study the effects on ovulation rates, embryo survival and related reproductive phenomena.In each of the two years the experimental period began when the gilts were approximately 70 days of age and continued until the 25th day after the second heat period. The total period was divided into three phases: Phase I—prepuberty; phase II—the first estrual cycle; and phase III—from second heat (at which time all gilts were bred) until the 25th day of gestation. The feeding levels for the three successive phases are designated by a letter sequence, e.g., LFF.The 64 gilts in trial I averaged 215.7 days at puberty (SD of 29.2) and the 74 gilts in trial II averaged 213.2 days (SD of 27.8). Full-fed gilts in trial I and trial II respectively were 223 and 222 days of age at puberty as compared to 208 and 205 days for the limited-fed groups (P<0.01). Breed did not have a consistent effect over the two trials.Weight at 154 days and age at puberty were significantly associated (r of −0.27; P<0.01) within groups for the two years. Puberal age and time of birth (within spring season) were not associated.The first estrual cycle length averaged 21.1 days over both trials. Breed means did not differ but the CW gilts had more variation in each trial than the PC gilts (P<0.02).Fifty-seven gilts in trial I averaged 12.4 (SD of 2.6) at second heat and 53 gilts in trial II averaged 12.9 ova (SD of 3.0). The 13.5 and 14.8 ova means of the CW gilts in the two trials respectively were both greater (P<0.01) than the 11.3 and 11.2 ova means of the PC gilts. Trial I gilts kept on full feed throughout (FFF) had significantly more ova (13.9; P<0.01) than LLL (11.1) or FLL (11.1) gilts. The FFF group did not differ from LFF gilts (13.6 ova). In trial II the FF (L and F) group ovulation rate of 13.6 ova at second heat was greater (P<0.01) than the LLL mean of 11.1 ova but did not differ from the LFL mean of 13.5 ova—indicating the necessity of only a short period of full feeding to stimulate maximum ovulation.Second-heat ovulation rate and rate of gain during the first estrual cycle (within groups) were significantly associated over the two years (r=0.24; P<0.05). Weight of gilt at second heat and ovulation rate at that heat were not associated.The over-all fertilization rate of 96 percent was not affected by the individuality of the boar, breed of boar, mating system, feed level of the gilt, or breed of gilt.Embryo survival averaged 44.3 percent in trial I and 59.4 percent in trial II. The trial I CW and PC gilts had 40.8 percent and 47.9 percent embryo survival and 5.07 and 5.33 embryos respectively (P≅0.05). Trial II CW gilts had more embryos (8.8; P<0.05) than the PC gilts (6.4) but they did not differ in percentage of embryos surviving. Trial I FFF gilts had 32 percent embryo survival and 3.89 embryos as compared to 57 percent survival and 6.4 embryos for the LLL gilts. The trial II FFF gilts did not differ from the LLL gilts in number of surviving embryos (7.6 vs. 8.8) but the difference in percent survival was significant (P<0.01). Pooled probabilities of litter size differences for the two years indicated larger (P<0.02) litter for the LLL gilts. Trial I FLL gilts had 49 percent survival as compared to 32 percent for FFF gilts and the LFF gilts had 38 percent survival as compared to 57 percent for the LLL group. In trial II, FFF gilts had more embryos (7.6 vs. 4.6; P<0.05) and greater survival (53 percent vs. 35 percent; P<0.05) than the FFL gilts. The LFL gilts had 71 percent survival and 9.3 embryos and did not differ from the FFF gilts.Rate of gain both immediately before and immediately after breeding, was associated (P<0.01) in a positive direction in both instances with embryo survival but the second heat ovulation rate was negatively associated with survival rate (r=−0.25; P≅0.05).Standard partial regressions indicate a possible negative effect of back fat thickness on ovulation rate and on embryo survival but a positive effect (P<0.05) of slaughter weight on those two phenomena.

The total solids, solids-not-fat, protein, lactose, and ash content of sow's milk are reported for two groups of sows, one group on pasture, and one group in dry lot. The sows were milked manually after the injection of 1 ml. of Pitocin, on the first day of lactation, the third day, at the end of the first week, and each subsequent week throughout lactation.The mean values of milk constituents for pasture sows were, for first day colostrum: total solids 22.81 percent, solids-not-fat 15.92 percent, protein 11.25 percent, lactose 2.89 percent, and ash 0.72 percent; for later milk: total solids 19.47 percent, solids-not-fat 13.16 percent, protein 7.09 percent, lactose 5.18 percent, and ash 0.99 percent. The mean values of milk constituents for dry-lot sows were, for first-day colostrum: total solids 22.81 percent, solids-not-fat 17.21 percent, protein 14.29 percent, lactose 3.42 percent, and ash 0.73 percent; for later milk: total solids 20.69 percent, solids-not-fat 13.38 percent, protein 7.42 percent, lactose 5.08 percent, and ash 0.98 percent.