T.S. Stewart

Dietary Fat Content and Fiber Type Modulate Hind Gut Microbial Community and Metabolic Markers in the Pig

Obesity leads to changes in the gut microbial community which contribute to the metabolic dysregulation in obesity. Dietary fat and fiber affect the caloric density of foods. The impact of dietary fat content and fiber type on the microbial community in the hind gut is unknown. Effect of dietary fat level and fiber type on hindgut microbiota and volatile fatty acid (VFA) profiles was investigated. Expression of metabolic marker genes in the gut, adipose tissue and liver was determined. A 2×2 experiment was conducted in pigs fed at two dietary fat levels (5% or 17.5% swine grease) and two fiber types (4% inulin, fermentable fructo-oligosaccharide or 4% solka floc, non-fermentable cellulose). High fat diets (HFD) resulted in a higher (P<0.05) total body weight gain, feed efficiency and back fat accumulation than the low fat diet. Feeding of inulin, but not solka floc, attenuated (P<0.05) the HFD-induced higher body weight gain and fat mass accumulation. Inulin feeding tended to lead to higher total VFA production in the cecum and resulted in a higher (P<0.05) expression of acyl coA oxidase (ACO), a marker of peroxisomal β-oxidation. Inulin feeding also resulted in lower expression of sterol regulatory element binding protein 1c (SREBP-1c), a marker of lipid anabolism. Bacteria community structure characterized by DGGE analysis of PCR amplified 16S rRNA gene fragments showed that inulin feeding resulted in greater bacterial population richness than solka floc feeding. Cluster analysis of pairwise Dice similarity comparisons of the DGGE profiles showed grouping by fiber type but not the level of dietary fat. Canonical correspondence analysis (CCA) of PCR- DGGE profiles showed that inulin feeding negatively correlated with back fat thickness. This study suggests a strong interplay between dietary fat level and fiber type in determining susceptibility to obesity.

Effect of number of motile, frozen-thawed boar sperm and number of fixed-time inseminations on fertility in estrous-synchronized gilts ☆

There are advantages for use of frozen-thawed boar sperm (FTS) as a tool for preservation and transfer of valuable genetic material, despite its practical limitations. It was hypothesized that increasing the number of motile FTS and number of fixed-time artificial inseminations (AI) would improve pregnancy rate and litter size. Semen from six boars was frozen in 0.5mL straws at 500x10(6)cells/mL. Gilts approximately 170 days of age, were induced into estrus with PG600 and synchronized using MATRIX (synthetic progestagen). Following last feeding of MATRIX (LFM), gilts were checked twice daily for estrus. At onset of estrus, gilts were randomly assigned in a 3x2 factorial treatment design to receive 1x10(9) motile FTS (n=19), 2x10(9) motile FTS (n=19), 4x10(9) motile FTS (n=19) in a single AI at 32h after onset of estrus, or 1x10(9) motile FTS (n=18), 2x10(9) motile FTS (n=17), or 4x10(9) motile FTS (n=19) in each of the two AI at 24 and 32h following onset of estrus. Ultrasonography was performed at 12h intervals after estrus to estimate time of ovulation. Reproductive tracts were collected 28-34 days following AI. Estrus occurred at 139+/-2h (mean+/-SE) after LFM and ovulation at 33+/-1h following onset of estrus. Dose and number of inseminations did not interact or individually influence pregnancy rate at slaughter (73+/-4.2%) or numbers of normal fetuses (10.8+/-0.5). However, number of fetuses tended (P=0.14) to increase with double AI but not with dose. Boar did not affect pregnancy rate but did affect number of normal fetuses and embryonic survival (P<0.01). Longer intervals from insemination to ovulation reduced pregnancy rate (P<0.05), number of normal fetuses (P<0.001), and embryonic survival (P<0.01). Ovarian abnormalities at slaughter were associated with reduced pregnancy rate (P<0.001). The results of this experiment indicate that a double insemination using 2x10(9) motile sperm would produce the greatest number of piglets with fewest numbers of frozen sperm used, while double AI with 1x10(9) motile sperm would be most practical for pig production with limited genetic resources. Fertility was also influenced by boar, interval from insemination to ovulation, and gilt ovarian abnormalities.

Pedigree analysis of 5 swine breeds in the United States and the implications for genetic conservation.

Globally, genetic diversity of livestock populations is contracting. Knowing the true extent of the contraction is needed to develop effective conservation strategies. Although contractions of genetic diversity have been documented at the breed level, little within breed documentation has occurred. This situation is no different for US swine breeds. Therefore, the objective of this study was to establish an inbreeding baseline for 5 pig breeds via pedigree records extracted from purebred registrations to each breed association for Berkshire (n = 116,758), Duroc (n = 878,480), Hampshire (n = 744,270), Landrace (n = 126,566), and Yorkshire (n = 727,268). For all breeds the number of registrations peaked after 1990 and declined since that time. The breeder structure was analyzed for Berkshire and Duroc; the average breeder registered pigs for 4.0 yr for both breeds. Breeders were grouped by longevity and herd size, and the inbreeding levels for the current population (pigs born 2006 and later) were evaluated. Presently, more than 99% of all pigs are inbred with the majority having inbreeding less than 10%. The range for percentage of animals that are more than 25% inbred ranged from 1.16% for Yorkshire to 6.09% for Berkshire. The greatest inbreeding for all animals within a breed ranged from 51% for Landrace and 65% for Yorkshire. Sires were grouped into 10 percentiles based on number of great-grandprogeny (GGP) produced; for all breeds, the top 10 percentile accounted for more than 75% of all GGP. Sixty percent of all sires produced less than 1% of all GGP, indicating few males are contributing to future generations. Generations ranged from 17 to 19 per breed with a generation interval ranging from 1.65 yr for Berkshire to 2.21 yr for Yorkshire. Mean inbreeding (%) at generation 17 (the most generations computed across breeds), rate of inbreeding per generation, and effective population size were 12.3, 0.0065, and 77 for Berkshire; 11.8, 0.0044, and 113 for Duroc; 6.8, 0.0046, and 109 for Hampshire; 17.9, 0.0067, and 74 for Landrace; and 8.0, 0.0044, and 113 for Yorkshire, respectively. The 2 breeds with fewest registrations, Berkshire and Landrace, had greater inbreeding rates and smaller effective population sizes, suggesting a need for more immediate conservation efforts. This analysis provides a basis for future monitoring of the genetic diversity of pig breeds and serves as a basis for planning conservation activities.

Implications of the pH and temperature of diluted, cooled boar semen on fresh and frozen-thawed sperm motility characteristics

Boar semen is typically collected, diluted and cooled for AI use over numerous days, or frozen immediately after shipping to capable laboratories. The storage temperature and pH of the diluted, cooled boar semen could influence the fertility of boar sperm. Therefore, the purpose of this study was to determine the effects of pH and storage temperature on fresh and frozen-thawed boar sperm motility end points. Semen samples (n = 199) were collected, diluted, cooled and shipped overnight to the National Animal Germplasm Program laboratory for freezing and analysis from four boar stud facilities. The temperature, pH and motility characteristics, determined using computer automated semen analysis, were measured at arrival. Samples were then cryopreserved and post-thaw motility determined. The commercial stud was a significant source of variation for mean semen temperature and pH, as well as total and progressive motility, and numerous other sperm motility characteristics. Based on multiple regression analysis, pH was not a significant source of variation for fresh or frozen-thawed boar sperm motility end points. However, significant models were derived which demonstrated that storage temperature, boar, and the commercial stud influenced sperm motility end points and the potential success for surviving cryopreservation. We inferred that maintaining cooled boar semen at approximately 16 °C during storage will result in higher fresh and frozen-thawed boar sperm quality, which should result in greater fertility.

Development of a stochastic model of pig growth to evaluate the impact of birth and twenty-one-day body weight and potential sorting strategies on the body composition growth and lysine requirements of pigs.

Abstract A stochastic pig growth model was developed to reproduce the nonlinear relationships between birth, weaning, and nursery-exit weights to later grow-finish BW, body composition, and Lys requirements. Serial grow-finish BW measurements of barrows and gilts were fitted to mixed model generalized Michaelis-Menten (GMM) equations. Two random effects of the GMM equations were predicted as functions of birth weight and 21-d weaning weight. A population of pigs was created to reproduce the variances and covariance of the random effects of the GMM function. The protein and lipid mass of each pig was predicted from serial real-time ultrasonic backfat and loin depth measurements. Predicted protein and lipid mass data of the barrows and gilts were fitted to functions of BW, which included pig-specific random effects. The random effects for protein mass were fitted to regression equations including birth weight, 21-d BW, and parameters of the GMM function. The sorting of pigs into light and heavy groups based on weaning weight, nursery-exit weight, or 84-d BW was evaluated. Sorting based on nursery-exit weight produced groups of pigs with larger differences in days to 125-kg BW than sorting based on weaning weight. Sorting based on BW resulted in more precise feeding of pigs relative to their daily Lys requirements.

Use of a Stochastic Model to Evaluate the Growth Performance and Profitability of Pigs from Different Litter Sizes and Parities of Dams

A stochastic model was developed to evaluate the effects of total number of pigs born and dam parity on pig compositional growth and postweaning profitability. The survival of pigs was modeled as a function of parity and of birth weight. Two management strategies were simulated, either with or without cross-fostering. Without cross-fostering, litter sizes of 6 to 14 total pigs born were simulated. Litter sizes of 6 to 20 total pigs born were simulated to be crossfostered to obtain a constant of 11 pigs nursed. Pigs from parity 1 dams were predicted to be slower growing and have reduced survival compared with pigs from dams of other parities. Increasing total pigs born from 6 to 14 without crossfostering reduced 150-d BW by 8.0 kg and carcass weight at marketing from 5.8 to 6.2 kg. Differences in carcass value

Swine Genetic Evaluation and Selection Programs12

Summary Swine selection procedures which utilize not only each animal’s performance but also performance of relatives can potentially increase the rate of genetic improvement by increasing the accuracy of selection. Four criteria are: (1) accurate evaluation of both young and old males and females, (2) timeliness of data analysis and summarization, (3) ability to account for possible biases including prior genetic selection and assortative mating, and (4) practical considerations concerning computer memory requirements and cost. Best linear unbiased prediction (BLUP) procedures provide accurate predictions of genetic merit by simultaneously predicting breeding values and adjusting for fixed effects. Simplified BLUP procedures including the reduced animal model (RAM) with recursive prediction or SHORT-CUT BLUP provide accurate genetic evaluation with reduced computer memory requirements. Multivariate BLUP can be simplified or reduced by the use of canonical transformations. The use of multivariate BLUP genetic evaluations in conjunction with quadratic bioeconomic objectives should result in the selection criteria which will maximize selection response. Seedstock producers should select their replacements relative to the intended use of their descendants in commercial crossbreeding systems. For this reason, three indexes are suggested: a terminal sire, general, and dam-breed (maternal) objective. With the implementation of a comprehensive genetic program, alternative selection programs including the intense selection of dams for a maternal objective can further increase genetic progress.

Development of Tools to Study Immune-Mediated Allergenic Responses to Food and Feed

Publisher Summary The application of biotechnology to the production of food and feed presents both new opportunities and challenges to the health of both human and livestock. As the last decade has witnessed an increase in the prevalence of Food Allergy (FA), the development of validated animal models that can be used to evaluate the potential impact of new food and feeds, both on the development of allergic responses and on growth and development, is needed. Allergic reactions to food and feed are relatively rare but occasionally produce a severe immunological reaction in both humans and animals. Food allergy encompasses several immune mechanisms that can present with a variety of symptoms. This chapter discusses the incidence and severity of food allergy, and outlines the mechanism of Type 1 immediate hypersensitivity as it applies to man and livestock. It also describes an ongoing effort that is directed toward developing inbred swine populations in which neonatal piglets exhibit either reduced or enhanced hypersensitivity to soybean and peanut.