Mark Knauer
· Professor and Extension Swine SpecialistNorth Carolina State University · Animal Science
Active 2004–2025
About
Dr. Mark Knauer is a Professor and Extension Swine Specialist in the Department of Animal Science at North Carolina State University. He is based in Polk Hall, Room 205, and can be reached via phone at 919-515-8797 or email at mark_knauer@ncsu.edu. His work focuses on swine, contributing to the field through extension activities that provide research-based information to producers and stakeholders. As a faculty member, he is involved in genetics and genomics, specifically quantitative genomics, supporting advancements in animal science through research and outreach efforts.
Research topics
- Computer Science
- Environmental science
- Statistics
- Engineering
- Political Science
- Artificial Intelligence
- Ecology
- Biology
- Animal science
- Mathematics
- Genetics
- Electrical engineering
- Environmental engineering
- Meteorology
- Geography
- Waste management
- Econometrics
Selected publications
Genetic parameters for image-based estimations of swine feet and leg conformation traits
Journal of Animal Science · 2025-01-01 · 2 citations
articleOpen accessThe objectives of this study were to develop and evaluate a novel algorithm for image extraction of structural conformation traits and estimate variance components among skeletal conformation, growth, and herd retention traits. An Intel RealSense D435i camera was used to obtain left-side-view RGB images on individual purebred Duroc pigs (n = 846) at 156 d of age. Frames were selected by a trained swine evaluator when either the left front leg (n = 1056), left back leg (n = 888), or both left legs (n = 728) were present in the field of view and the respective foot pads from toe to heel were in contact with the ground. Selected images were processed through Apple Inc's image segmentation algorithm to extract the pig from the background. Segmented pig images were then processed through a novel algorithm developed in this study. The algorithm identified the leg and estimated 21 skeletal conformation traits from each leg. Steps for user intervention were added to assist the algorithm in identifying which leg(s) were present and the general location of each leg to increase the accuracy of leg identification and trait acquisition. The algorithm correctly identified at least one front and one back leg from an image for 99.9% and 98.0% of the pigs, respectively. Heritability estimates ranged from 0.01 to 0.33 for all conformation traits with the quadratic term for the curvature of the anterior side of the front and the height of the back leg having the highest heritability for each location (h2 = 0.33 and 0.30, respectively). Genetic correlations among image feet and leg conformation traits and production traits (finishing average daily gain, weight per day of age, and finishing feed efficiency) ranged from -0.37 to 0.19. Boars that remained in the breeding herd for longer than 200 d tended (P = 0.08) to have greater curvature of the front leg and lower (P = 0.07) angularity between the midpoint of the foot and the anterior point of the pastern and had significantly (P = 0.03) shorter distance between the pastern and the top of the shoulder than those that were removed prior to 200 d. Gilts that remained in the breeding herd for longer than 200 d tended (P = 0.08) to have less curvature of the back leg. The current study presents an algorithm that extracts novel, objective structural conformation traits and reports corresponding genetic and phenotypic parameters.
Animal - science proceedings · 2025-08-01
articleAgriculture · 2025-09-30
articleOpen accessIn swine production, it is broadly recognized that ventilation rates and indoor environmental conditions influence pig productivity. However, sparse scientific data are available on the combined effects and potential interactions of these factors in commercial production systems. This study investigated indoor environmental and management factors influencing wean-to-finish pig mortality in a commercial system. Temperature, relative humidity (RH), and carbon dioxide (CO2) were recorded every 10 min in the front and back of 16 barns across five grow-finish sites in eastern North Carolina for two turns (four barns) or three turns (12 barns) for a total of 44 pig groups. Proportional weekly mortality was modeled using a generalized linear mixed model. Results showed that pigs in environments warmer than the desired room temperature had lower mortality (p < 0.001), suggesting cold stress was more detrimental than heat stress. Elevated RH and CO2 at the back of the barn were linked to increased mortality (p < 0.001), highlighting air exchange rates as a key indicator. Mortality was greatest in pig groups placed during Spring and lowest in Summer (p < 0.05), and mortality declined as pigs aged (p = 0.0134). Surprisingly, greater barn occupancy correlated with lower mortality (p = 0.0012), potentially related to piglet quality at placement. The predictive power of the model varied with the turn of pigs, with R2 averaging 0.24 (ranging from 0.001 to 0.61) and an average RMSE of 0.36% (ranging from 0.17% to 0.77%). Ammonia (NH3) was recorded at the back of six barns, and concentrations were modeled. Greater NH3 concentrations were associated with increased pig age, RH, and CO2, as well as lower deviation from desired room temperature and lower barn occupancy. Collectively, these findings highlight the importance of proper ventilation and management on swine productivity.
2025-07-23
otherSenior authorPSI-22 Effects of modifying PPAR activity on carnitine uptake in swine mammary organoids.
Journal of Animal Science · 2025-10-01
articleOpen accessSenior authorAbstract Carnitine is essential in growth and development of newborn pigs due to its role in energy production and detoxification via removing acyl-residues. The primary source of carnitine after birth is sow’s milk because newborn pigs have a limited capacity to synthesize carnitine. The carnitine concentration in sow milk varies with dietary carnitine and lactation stage in which the expression of mammary organic cation transporter (OCTN) may play a decisive role as the mediator of carnitine homeostasis. Regulation of peroxisome proliferator–activated receptor (PPAR) influences expression of genes associated with carnitine synthesis and OCTN activity in liver, kidney and enterocyte, but the regulatory role in mammary tissue is not clear especially as lactation leads to down-regulation of PPARα. In this study, the effects of altering PPARα and PPARγ expression on carnitine uptake was examined in vitro in organoids cultured from mammary tissue of pregnant sows. The organoids were incubated with PPARα agonist clofibrate (10 µM), PPARγ agonist thiazolidinedione (TDZ, 10 µM) and antagonist GW9662 (5 µM) in a 3-dimentional environment. The expression of genes PPARα and PPARγ, and genes associated with carnitine uptake OCTN1 (SLC22A4) and OCTN2 (SLC22A5), and genes associated with fatty acid oxidation, carnitine palmitoyltransferase (CPTIα), CPTIβ and acyl-CoA oxidase (ACOX) were determined after 48 hours using RT-PCR. Carnitine uptake rate was measured by adding 16 μM of 3H-labeled carnitine (1µCi/µmol) to cultures for 30 minutes. Clofibrate stimulated expression of PPARα, SLC22A4, SLC22A5 and CPTIβ (p &lt; 0.05) with no significant changes in PPARγ, CPTIα and ACOX (p &gt; 0.1). However, the stimulation did not change carnitine uptake. TDZ had no impact on the expression of all examined genes but GW-9662 significantly increased CPTIα expression by 4-fold. Consistent with CPTIα expression, carnitine transfer rate increased by 70%. Correlation analysis between the gene expression and carnitine uptake rate indicated that the elevation of carnitine uptake was correlated with CPTIα expression (p &lt; 0.005, Corr=0.97) or the ratio of CPTIα/CPTIβ, (p &lt; 0.005, Corr=0.99). We conclude that up-regulation of PPARα expression increases expression of genes associated with mammary carnitine transporters and fatty acid oxidation, but carnitine uptake is subject to the metabolic status of mammary tissue. Supported by Animal Health and Production and Animal Products (grant no. 2023-67015-39663/1030033) from the USDA National Institute of Food and Agriculture, and by the North Carolina Agricultural Research Hatch projects 1016618 and 02780. Keyword: carnitine, mammary, organoids
Translational Animal Science · 2025-01-01
articleOpen accessAbstract Two experiments were conducted to determine the effects of a botanical-derived feed additive containing capsicum oleoresin, clove and garlic essential oils (CCG; Fytera Start, Selko, Indianapolis, IN) in nursery pigs fed with or without pharmacological levels of Zn and Cu. In Exp. 1756 pigs (Duroc × Landrace/Large White composite (Smithfield Premium Genetics), initially 7.8 ± 0.09 kg) were used in a 40-d study to determine the effects of CCG level on growth performance of nursery pigs fed pharmacological levels of Zn and Cu. In Exp. 2340 barrows (DNA 200 × 400, initially 6.1 ± 0.08 kg) were used in 38-d study to determine the effect of CCG in diets with or without pharmacological levels of Zn and Cu on growth performance and fecal dry matter (DM). For both experiments, pigs were randomly allotted to pens which were allotted to 1 of 4 dietary treatments in a completely randomized design. There were 9 pigs per pen and 21 pens per treatment in Exp. 1 and 5 pigs per pen and 17 pens per treatment in Exp. 2. Dietary treatments in Exp. 1 were corn-soybean meal based with pharmacological levels of Zn and Cu and included either 0, 25, 50, or 100 mg/kg of CCG. Dietary treatments in Exp. 2 were arranged in a 2 × 2 factorial with main effects of CCG (none or 100 mg/kg) and nutritional or pharmacological levels of Zn and Cu. All Exp. 2 diets contained 110 mg/kg of Zn and 16.5 mg/kg of Cu from the trace mineral premix. For both experiments, pharmacological levels of Zn were added at 3,000 and 2,000 mg/kg in phase 1 and 2, respectively and Cu was added at 250 mg/kg in all phases. For Exp. 1, overall average daily gain (ADG) increased (linear, P &lt; 0.05) and average daily feed intake (ADFI) tended to increase (linear, P &lt; 0.10) as CCG increased from 0 to 100 mg/kg. For Exp. 2, there was a CCG × Zn/Cu interaction observed for overall ADG and ADFI (P &lt; 0.05) where CCG numerically increased ADG and ADFI in pigs fed nutritional levels of Zn and Cu; but reduced ADG and ADFI in pigs fed pharmacological levels of Zn and Cu. There was a Zn/Cu × day interaction (P = 0.001) for fecal DM, in which there was no difference (P &gt; 0.10) in fecal DM on d 10, but pigs fed pharmacological levels of Zn and Cu had lower (P &lt; 0.001) fecal DM on d 21 compared to pigs fed nutritional levels of Zn and Cu. In summary, when included in diets with pharmacological levels of Zn and Cu, feeding increasing levels of CCG increased ADG in Exp. 1 but did not improve performance in Exp 2.
PSIV-14 Effect of water nipple size on nursery pig performance
Journal of Animal Science · 2025-05-01
articleOpen accessSenior authorAbstract The objective of the current study was to evaluate nipple drinker size on nursery pig performance. In lactation, all piglets had access to a baby piglet water nipple placed near the sow feeder. At weaning, piglets were placed into one of four nursery rooms with supplemental heating, mechanical ventilation and tri-bar flooring. Pigs (n=756) were randomly allocated to 84 pens (9 pigs per pen, 0.23 m2 per pig) where they were watered with a standard nursery nipple drinker (Aqua Series 1/2“ X 3/8” Nursery Nipple, Hog Slat, Newton Grove, NC) or a standard grow-finish nipple drinker (Aqua Series 1/2” Finish Water Nipple, Hog Slat, Newton Grove, NC). All pens had ad libitum access to feed and water for the 42 day trial. Data was analyzed in SAS using PROC GLM. Fixed effects included nursery room and nipple drinker size. Results are shown in Table 1. No differences were detected between nipple drinker sizes for body weight (P≥0.90), average daily gain (P≥0.68), average daily feed intake (P≥0.56), or feed-to-gain ratio (P≥0.28). These results suggest either a nursery nipple drinker or a grow-finish nipple drinker could be successfully used in the nursery to water pigs. Further piglet water research in lactation and early nursery is warranted.
Applied Animal Science · 2024-12-01
articleOpen accessJournal of Animal Science · 2024-05-01
articleOpen accessAbstract Ideal conditioned sows are desired because they maximize herd performance, improve female well-being, and optimize financial outcomes. Sow productivity has increased, and body composition of females has changed, with sows being leaner and having less adipose tissue compared with their predecessors. Our objective was to determine the relationship between sow caliper measurements with sow reproductive performance and longevity in the herd. Data collected in four different production systems located in the US and Brazil were used, with 3,083, 356, 7,456, and 26,773 individual PIC Camborough observations represented within each of these databases. Caliper measurements were collected at due to farrow and weaned sows and were recorded in units, standardized to an ideal range of 12 to 15 units. Caliper change in lactation was determined as the caliper units at weaning minus the caliper units pre-farrowing. Response variables included proportion of born alive and stillborn piglets, lactation feed intake, as well as removal and mortality risk for all causes, or specifically for reproductive and pelvic organ prolapse (POP) causes. Data were analyzed using generalized linear mixed models, hazard ratio analysis, and survival models with the lmer, glmer, and surv functions of R. Sow served as the experimental unit. Caliper measurements at farrowing had curvilinear associations (P &lt; 0.05) with percentage born alive piglets and percentage stillborn piglets. Increasing caliper units at farrowing resulted in linear reduction (P &lt; 0.05) in lactation average daily feed intake and in linear increase (P &lt; 0.05) in caliper losses during lactation. Sows losing 1 to 2, 3 to 4, or 5 and greater caliper units in lactation had 1.5, 1.8, and 2.4 times, respectively, greater risk (P &lt; 0.05) of being removed from the herd in the next cycle compared with sows that gained 0 or more units. Reduced caliper units in due-to-farrow sows resulted in reduced probability (P &lt; 0.05) of survival in the next cycle considering prolapse removal reasons. Sows with due to farrow caliper units of 12 to 15 had 1 to 1.6 times (95% Odd Ratio Confidence Interval), 9 to 11 had 1.2 to 2.1 times, and less than 9 caliper units 3.1 to 3.2 times greater risk of death or being removed from the herd due to POP compared with those with &gt;15 units. Reduced caliper units in due-to-farrow sows resulted in reduced probability of survival in the next cycle considering all removal and mortality causes. Specifically, sows with less than 9 caliper units at farrowing had 2.0 times greater risk (P &lt; 0.05) of removal and 4.4 times greater risk (P &lt; 0.05) of mortality compared with sows with over 15 caliper units. In summary, both under and over-conditioned sows have reduced productivity. Underconditioned sows are at greater risk for mortality and for POP related removal.
Journal of Animal Science · 2024 · 5 citations
- Computer Science
- Political Science
- Statistics
The negative effects of heat stress on swine reproduction have been well documented and the recent global warming trend caused by climate change is leading to more days with high temperatures every year. This has caused a reduction in litter trait performance of Landrace sows in Taiwan, a country extending across tropical and subtropical oceanic zones. Therefore, this study developed a modified model to determine which stages of pregnancy, before, early, middle, and late, had the largest impacts of heat stress on litter traits. A reaction norm model (RNM) was used to identify sows with high resilience to heat stress for litter traits followed by analysis of the modified model. Data from Landrace sows were collected from 2 farms in Taiwan between 2008 and 2021. A total of 11,059 records were collected for total number born (TNB), number born alive (NBA), and stillborn rate (STBR). The results showed that the heritabilities of TNB, NBA, and STBR were 0.170, 0.115, and 0.077, respectively. These results were similar between the conventional model and the modified model. In the modified model, the before and early stages of sow pregnancy were the significant periods for TNB and NBA (P < 0.05), while the early and middle stages were significant for STBR (P < 0.05). According to the RNM results, the heritability estimates for TNB, NBA, and STBR were 0.23 to 0.11, 0.18 to 0.08, and 0.10 to 0.04, respectively, showing a decrease from low temperature-humidity index (THI) to high THI. The minimum genetic correlations between the highest and the lowest THI for TNB, NBA, and STBR were 0.85, 0.64, and 0.80, respectively. The results of the RNM for breeding value showed re-ranking across THI values. In conclusion, similar results were obtained for heritability when the model was modified for heat stress estimation. Yet re-ranking of breeding values across THI could help farmers to select not only for improved litter trait performance but also for heat stress resilience of Landrace sows in Taiwan.
Frequent coauthors
- 12 shared
Jeffrey Wiegert
Mitchell Institute
- 10 shared
Kenneth J. Stalder
Christensen Fund
- 10 shared
Zack Peppmeier
North Carolina State University
- 9 shared
Locke A. Karriker
Kansas State University
- 9 shared
Sanjay B. Shah
- 7 shared
G Sée
University of Nebraska–Lincoln
- 7 shared
E. van Heugten
North Carolina State University
- 7 shared
T. J. Baas
Royal HaskoningDHV (Czechia)
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