Ten animals from two litters of English large white pigs were weaned at 12—15 days of age and placed one per cage within constant—temperature rooms. In the first group, a comparison was made between three animals raised at 5°C and their littermates raised at 35°C. There were marked differences in appearance and in gross morphology. Those from the cold environment had more hair, were shorter and more stocky, and had a shorter tail and smaller ears than their littermates. A second group of animals were raised at 20°C and 35°C; it was found that with respect to all measurements the 20°C pigs were intermediate between the 5° and 35°C animals. These observations accord with Bergmann's Rule that animals raised in colder environments are characterized by a reduced surface area/body weight ratio. The results likewise substantiate Allen's Rule that in colder climates the length of appendages and of extremities is reduced.

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Since "miniature swine" are being used extensively as a research a dmal and since the literature concerning tooth eruption is not very precise, it has seemed advisable to observe and record tooth eruption in the "miniature swine" being used and to make comparisons with existing literature of domestic swine.A total of 55 pigs of the Pitman-Moore strain were observed weekly from birth until their dentition was complete at about 26 weeks. Lateral x-ray head plates and study models of both arches were made weekly for two members of the group. The study models and x-rays served for orientation and positive identification of teeth; and with the weekly observations constitute the data.Analysis of the data indicated there was no significant difference in the eruption time for any tooth due to the sex of the individual. A mean sequence of eruption for each arch was established for the group based on coefficients of concordance. There was no significant difference in sequence of eruption due to sex or litter.The eruption time and sequence noted for Pitman-Moore swine differed slightly from that recorded for domestic swine. The differences observed were slight and could be explained by the probably infrequent observations of domestic swine or small sample size.

Porcine reproductive and respiratory syndrome (PRRS) virus is a major swine virus that causes reproductive impairment in sows, as well as respiratory disease, reduction in growth rates, and mortalities in all ages of pigs. The objective of this study was to quantify the impact PRRS has on grower-finisher pig feed efficiency and tissue accretion rates. Thirty PRRS naïve, littermate pairs of maternal line Choice Genetics gilts (33.6 ± 0.58 kg BW) were selected and pairs split across 2 barns consisting of 5 pens (n = 6 pigs/pen per barn). Pigs in both barns were fed corn-soybean-DDGS diets ad libitum. All pigs in one barn were inoculated (CHAL) via an i.m. injection of a live PRRS strain isolated from the region (0 d post inoculation, dpi), while pigs in the other barn were given a saline control injection (CONT). Pig performance (ADG, ADFI, G:F) was assessed from 35 kg BW until each group reached market BW (128 kg). Additionally, longitudinal apparent total tract digestibility (ATTD) and body composition was assessed using Dual-energy X-ray absorptiometry (DXA) post inoculation (dpi) to estimate lean, protein, fat and bone accretion rates. Serological data from CHAL pigs showed that PRRS titers peaked 7 dpi and these pigs seroconverted by 35 dpi. According to both genomic and protein PRRS titers, CONT pigs were naïve to CHAL throughout the study. The PRRS infection reduced (P < 0.001) ATTD of dry matter, energy and nitrogen by 3 to 5% at 21 dpi and the reduction in ATTD persisted after 65 dpi. Compared to the CONT, CHAL pigs had decreased ADG (0.89 vs. 0.80 kg/d, P < 0.001), ADFI (2.05 vs. 1.93 kg/d, P < 0.001), and G:F (0.44 vs. 0.41 kg/d, P < 0.001) over the entire test period. The CHAL pigs also had attenuated DXA predicted whole body accretion of lean (547 vs. 633 g/d, P = 0.001), protein (109 vs. 126 g/d, P = 0.001) and fat (169 vs. 205 g/d, P = 0.001) compared to their CONT counterparts from dpi 0 to 80. Based on carcass data at slaughter (and consistent with the DXA data), CHAL pigs had leaner carcasses and reduced yields. These data clearly demonstrate that PRRS infection reduces digestibility, feed efficiency and protein accretion rates in grower-finisher pigs.

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The vascular supply to the skin of pigs was studied in animals perfused with the dye, monastral fast blue. The arrangement of the blood vessels in control animals was in three plexuses, similar to that in other mammals but with the middle plexus poorly developed.A litter of pigs was divided into two groups at the age of 12 days and one group was raised in a warm room and the other in a cold room. The pigs were killed at age three months when the warm room was 35°C and the cold room 5°C. A quantitative evaluation of the blood supply to the skin of the experimental animals revealed that the pigs from the warm room had more blood vessels in the skin than those raised in the cold; the difference was statistically significant (P < 0.01). In the case of pigs from a second litter reared at 35°C and 20°C, no significant difference in the number of blood vessels was detected.Unlike most domestic animals the hair coat of the pig is sparse and for this reason changes in the blood flow through the skin are likely to be as important in the regulation of heat loss as they are in man. In addition to making physiological measurements of blood flow, however, it is also of importance to know the anatomical arrangement of the skin blood vessels, and to determine the extent to which this arrangement can be modified by long periods of exposure to different ambient temperatures. This information is crucial to a better understanding of the process of adaptation to environmental temperature in the pig, which is already known to involve changes in heat production, in thyroid activity and in behavior (Ingram and Mount, '65; Ingram and Slebodzinski, '65; Baldwin and Ingram, '68).Some information about the vascularity of the pig's skin is already available (Moritz and Henriques, '57), but the species has not been studied from the point of view of heat loss. Moritz and Henriques ('47) studied sections of skin treated with benzidine and emphasized the resemblance to human skin, which is so great in some instances that it is difficult to distinguish between them. In the present study blood vessels were injected with a dye and the skin vessels of pigs living at different en-ANAT. REC., 163: 517-524.vironmental temperatures were compared quantitatively with each other. MATERIALS AND METHODS AnimalsPigs of the English Large White breed, of both sexes, aged 12 weeks were used. In studies of the general distribution of blood vessels the animals were taken from the farm stock and the environmental temperature at which they had been living was not specially controlled. In the studies on acclimatization the temperature at which the animals lived was controlled from 12 days of age. Injection of dyeThe animals were deeply anesthetized with sodium pentabarbitone and the neck region opened to expose the carotid arteries and jugular veins. One glass cannula was then introduced into the carotid artery of one side and another into the contralateral internal jugular vein. The carotid artery was then perfused at a pressure of 120 to 180 mm Hg with a so...

The diameters of collagen fibrils were measured in three varieties of periodontal connective tissue in the rat mandible (incisor periodontal ligament, incisor enamel-related connective tissue and molar periodontal ligament). Despite structural and functional differences between the tissues, a similar range of collagen fibril diameters was seen in each (average 45 nm). Variation between animals and between adjacent fiber bundles in any given tissue was observed. Even within any single fiber bundle, the fibrils had a variety of diameters. Although it has been claimed that collagen fibrils have diameters which are multiples of 8 nm, such a relationship could not be discerned for periodontal collagen fibrils. It was estimated that about 65 per cent of a periodontal collagen fiber bundle or sheet is composed of ground substance. Despite reports of abundant oxytalan fibers in periodontal tissues at the light microscope level, only one fiber having characteristics of oxytalan was observed in this electron microscopic study. Some aspects of the functional significance of the findings are discussed.