Gilt Development Research Articles

219 Effect of stocking density on F1 gilt grow-finish performance

Abstract As replacement rates in the swine industry have increased, gilt development units have increased the number of females developed in the same allotted space. The impact of decreasing space is not well understood on the developing gilt. Therefore, the objective of this study was to evaluate differences in grow-finish performance for developing gilts housed at different stocking densities. At 10 wk of age 824 F1 females (DNA L241, DNA Genetics, Columbus, NE) were randomly allotted to 12 pens per treatment of either 0.71 m2 (n = 360), 0.93 m2 (n = 264), or 1.25 m2 (n = 204). Body weights (BW) were individually collected at 10, 24, and 31 wk of age. Backfat and loin depth were measured using an Exxago Ultrasound between the 10th and 11th rib at 24 and 31 wk of age. Feed consumption was measured at the pen level using a Feed Logic system. Mortality date, reason, and BW were recorded throughout the grow-finish phase. At 10-wk of age, there was no significant difference in BW between the treatments. Differences in BW were observed between treatment 0.71 m2 at 119.3 kg compared with 0.93 m2 and 1.25 m2 at 123.4 kg and 125.6 kg, respectively (P < 0.01). All stocking densities were significantly different (P < 0.01) at 31 wk of age with 0.71 m2 at 142.4 kg, 0.93 m2 at 152.4 kg and 1.25 m2 at 156.5 kg. Backfat and loin depth were significantly different at 24 wk for 0.71 m2 compared with 0.93 m2 and 1.25 m2 (P < 0.05). At 31 wk of age, all treatments were significantly different for backfat with 0.71 m2 at 16.1 mm, 0.93 m2 at 18.0 mm and 1.25 m2 at 19.1 mm (P < 0.05). Feed conversion was not different across treatments from 71 d of age until 84 d of age and from 84 until 111 d of age. However, feed conversion was significantly different from 111 d until 167 d of age for 0.71 m2 at 3.83 compared with 1.25 m2 at 3.40 (P < 0.10). Mortality was not different between treatments (P < 0.05). Gilts that were assigned to the least square foot treatment grew slower and had decreased backfat and loin depth. This could potentially impact the timing of the estrus detection and matings in the replacement gilt population. Overall, producers looking to improve the BW of females entering the breeding herd should evaluate increasing the space allotted per female in their gilt developer.

83 Effect of stocking density on F1 gilt reproductive performance

Abstract Replacement females are the future of a farm, and their development can impact production. Currently, replacement gilts are housed in many different environments. Stocking density of replacement females is one factor that varies across production systems. Therefore, the objective of this study was to evaluate the effect of different stocking densities on replacement gilt reproductive performance. At 10 wk of age, DNA L241 females (n = 824; DNA Genetics, Columbus, NE) were randomly allotted to finishing pens with 3 different stocking densities. Each stocking density consisted of 12 pens of 0.71 m2 (n = 360), 0.93 m2 (n = 264), and 1.25 m2 (n = 204). Heat detection started at 20 wk of age with fence line exposure for 2 wk at 15 minutes per pen. Within pen boar exposure occurred from 22 to 31 wk of age for a minimum of 10 min per pen. Starting at 20 wk of age, females that exhibited red and swollen vulvas or standing estrus were recorded. Body weight, backfat, and loin depth measurements were collected at estrus detection. A blood progesterone assay was performed on all females at 24 wk of age. Further blood progesterone assays were performed at 27, 29 and 31 wk of age on any female for which progesterone was not detected on previous assays. Females were mated on their 2nd estrus if they were at least 136 kg or on their first estrus if they were over 145 kg. Body weight was recorded at the time of mating. For females that cycled by 31 wk, females in the 0.71 m2 treatment cycled significantly earlier than the 0.93 m2 treatment, 147 vs 153 d post-weaning respectively (P < 0.05). No difference was detected in age at mating; however, gilts in the 0.71 m2 treatment were 5.9 kg and 8.2 kg lighter than the 0.93 and 1.25 m2 treatments respectively (P < 0.01). At 31 wk of age 60% of the 0.71 m2, 71% of the 0.93 m2, and 77% of the 1.25 m2 treatments had cycled according to visual heat detection. However, according to the progesterone assay, at 31 wk of age 75% of 0.71 m2, 81% of the 0.93 m2, and 84% of the 1.25 m2 had cycled. The accuracy of visual heat detection compared with progesterone assay were 79.4% for 0.71 m2, 77.3% for 0.93 m2, and 85.8% for 1.25 m2 treatments. Overall, the 1.25 m2 treatment resulted in heavier females at mating, a greater rate of females cycling, and a more accurate detection of females cycling than the 0.71 m2 treatment. Swine producers can improve the percentage of females detected in estrus and mated in the desired period by providing additional rearing space during gilt development.

Effect of Body Weight and Age at Puberty and Mating on Subsequent Gilt Development Weights, Litter Traits, and Colostral Immunoglobulin G of the F1 Large White X Landrace Gilts

Effect of Body Weight and Age at Puberty and Mating on Subsequent Gilt Development Weights, Litter Traits, and Colostral Immunoglobulin G of the F1 Large White X Landrace Gilts

31 Importance of Good Sow Development: Focusing on Nutrition and Feeding from Gilt Development to Subsequent Parities

Abstract Continuous genetic progress leads to significant improvements in growth and efficiency of PIC Camborough gilts. As an example, gilt weight gain per day of age has increased dramatically in the past decade. This implies that gilts are heavier at a similar breeding age, which increases the likelihood of breeding overweight gilts. Additionally, sows have less backfat depth and are leaner compared with their predecessors. It has been reported that gilt retention rate until parity 3 declines when breeding gilts with over 160 kg of body weight. Hence, controlling growth rate of developing gilts could be helpful to achieve the target breeding weight (135 to 160kg). A recent study reported that reducing dietary nutrient density (ME and SID Lys) from 57 kg until breeding significantly reduced breeding weight by 4 kg (P < 0.05). The slower growing gilts had reduced stillborn (P < 0.01), had 0.79 more pigs born alive (P = 0.10), and weaned a total of 238 more pigs over three reproductive cycles. However, with the genetic trend for faster growth rate, it is inevitable to breed overweight gilts in production. Energy requirement for maintenance (MEm) of gestating sows is a function of body weight of the sow. Thus, heavier gilts at breeding need more energy for maintenance. An assessment using data from 2,475 gilts collected in commercial sow farms evaluated how different feeding levels satisfy the MEm of a gilt herd bred at 154 kg. The results showed that feeding 5.90 Mcal of ME/day or 4.40 Mcal of NE/day results in only a few gilts fed below maintenance from 90 to 112 days of gestation. However, if a decreased feeding level (5.17 Mcal of ME/day or 3.85 Mcal of NE/day) was adopted, which has been seen in production with a purpose of reducing body condition, almost all the gilts would be fed under maintenance from 90 to 112 days of gestation. Gilts are still growing and developing during their first gestation and inadequate feeding level may jeopardize their growth and development, which could lead to poor lifetime productivity. Heavier gilts become heavier sows in the subsequent parities; thus, the sows also require more energy for maintenance during subsequent gestations. Therefore, PIC recommends feeding gilts, ideal and fat sows with 5.90 Mcal of ME/day or 4.40 Mcal of NE/day throughout gestation. Feeding this level throughout gestation will result in an estimation of no overall caliper change. Whereas for thin sows that need to recovery condition, PIC recommends feeding 8.60 Mcal of ME/day or 6.50 Mcal of NE/day (Figure 1). Feeding this level throughout gestation will result in an estimated overall gain of 3 caliper units. In summary, the increased potential for growth and efficiency of PIC gilts warrants the adoption of multiple strategies to improve longevity and lifetime productivity.

49 Leveraging Big Data Analytics to Improve Disease Surveillance and Welfare in Pig Production

Abstract Large amounts of data are routinely collected in pig production, including operational farm data and, more recently, data from digital tools such as remote and on-site sensing technologies. Furthermore, additional sources of information, such as demographic, economic, and weather variables, can be combined with farm data. Integrating and analyzing such data can generate valuable insights and data-driven decision-making tools for disease surveillance, animal welfare, and production system optimization. This presentation discusses two examples of big data integration and analysis in the context of optimizing management practices in pig production. The first example pertains to a data analytics project related to total transportation losses (TTL) of market-weight pigs, an important animal welfare concern that economically impacts producers and abattoirs. After merging and checking data for errors, the final dataset included 4.5M+ pigs from 420 farms loaded in 26,819 shipments delivered to two abattoirs. Results from a generalized additive mixed model (GAMM) technique showed that the risk of loss per shipment was constant for temperature-humidity index (THI) values between −10 and 10. Additionally, a strong interaction between wind speed and precipitation was associated with TTL. TTL were strongly associated with the type of driver and the distance traveled, in addition to weather variables. The second example pertains to swine disease surveillance, in which data from a multi-site system, where pigs are transported between farms after each particular production phase, were investigated. Reports of 76,566 shipments across sites were obtained and used to characterize pig movement flow, conduct percolation analysis to investigate network robustness to interventions for diseases with different transmissibility, and assess the potential impact of each farm type on disease dissemination across the system. Topological properties of networks were investigated, such as the number of nodes and edges, degree assortativity, density, average path length, diameter, clustering coefficients, giant strongly connected component, giant weakly connected component, giant in component, and giant out component. Overall, the results indicated that gilt development units, nursery, and sow farms have a more central role in the pig production hierarchical structure. As such, they are potential major factors in the introduction and spread of diseases in the system. Wean-to-finishing and finishing sites displayed high in-degree values, indicating that they are more susceptible to infection. Additionally, the characteristics of a disease should have strong implications for biosecurity practices across production sites.

273 Longitudinal Investigation of Nutrient Intervention During Gilts Development on Sow Reproductive Performance and Longevity

Abstract The objective of this study was to evaluate the dietary nutrient level and vitamin D source during gilt development on sow reproductive performance and longevity. Three groups of gilts (n = 60 in each group, PIC Camborough) were received at 9 weeks of age (average BW: 21.2 ± 0.67 kg) and assigned to one of four dietary treatments. Treatments comprised two levels of dietary nutrients (Adeq: optimal growing diets that exceed NRC 2012 recommendations or Low: moderate slow growing diet that SID lys and ME levels were gradually reduced by 0.03% and 0 kcal/kg, 0.15% and 146 kcal/kg, and 0.15% and 150 kcal/kg, respectively) and two sources of vitamin D [StD: 1653 IU cholecalciferol/kg or HyD: 500 IU cholecalciferol/kg + 50 mcg calcifediol (ROVIMIX HY-D DSM Nutritional Products North America)] during development phase 1 (22 to 57 kg), 2 (57 to 91 kg), and 3 (91 until breeding). Dietary nutrient level treatment was withdrawn during gestation and lactation stages, while sows remained on their vitamin D treatments through three reproduction cycles. Replacement gilts (n = 12 in each cycle) were handled and treated the same as the initial three groups of gilts and introduced to each group at the end of each cycle. Gilts fed Low diets had decreased ADG (P = 0.01), lighter BW (P < 0.01), increased ADFI (P < 0.01), and poorer feed efficiency during development (P < 0.01) when compared with gilts fed Adeq. Gilts fed Low were lighter (149.8 kg) than the Adeq (153.9 kg) fed gilts. Sows fed Low diets during their development had reduced number of stillborn (P < 0.01), 0.79 more pigs born alive (P = 0.10), and weaned a total of 238 more pigs than Adeq sows (2,127 vs 1,889, P < 0.01). Numerically greater lactation intake allowed sows developed using Low diets to have greater backfat at weaning compared with those developed using Adeq diets (weaning backfat: 13.0 vs 11.9 mm, P = 0.03). Gilts and sows fed HyD had significantly greater born alive litter weight (P = 0.03) due to numerical greater born alive (14.2 vs 13.47, P = 0.14) but average born alive piglet BW (P = 0.86) was not different. Piglets from sows fed HyD_Low diets had greater preweaning mortality compared with piglets from sows fed StD_Low diets because of greater number of pigs born alive observed in HyD_Low sows (1.323.vs.1,143, P = 0.02). Interestingly, a total of 5 sows that were culled due to lameness were all from the first cycle and StD treatment. Moreover, the percentage of sows rebred tended to be greater in sows fed HyD diets (P=0.08). These data indicate that the level of dietary nutrients fed during gilt's development and feeding HyD continuously from gilt development through subsequent reproductive phases, modulated reproductive performance.

PSIV-1 Nutrient Intervention During Gilt Development Leads to Effects on Progeny Growth Responses

Abstract To elucidate the effect of early life dietary nutrient level and vitamin D source during gilt development on progeny growth performance, equal number of weaning age piglets (n = 72) were selected from each of 4 sow treatments group. All pigs were fed a common 3,000 ppm zinc diet for first two weeks postweaning to allow for accommodating the weaning process. At the beginning of week 3, pigs were sorted by sow parity and BW within gender and stratified based on maternal dietary treatments. Dietary treatments during gilt development period included two levels of dietary nutrients (Adeq: optimal growing diet that exceed NRC 2012 recommendation or Low: moderate slow growing diet that SID lys and ME levels were gradually reduced by 0.03% and 0 kcal/kg, 0.15% and 146 kcal/kg, and 0.15% and 150 kcal/kg, respectively) and two sources of vitamin D [StD: 1653 IU cholecalciferol/kg or HyD: 500 IU cholecalciferol/kg + 50 mcg calcifediol (ROVIMIX HY.D DSM Nutritional Products North America)] during development phase 1 (23 to 57 kg), 2 (57 to 91 kg), and 3 (91 until breeding). Dietary nutrient level treatment was withdrawn during gestation and lactation stages, while sows remained on their vitamin D treatments. Progeny were fed with a 6-phase feeding regimen as nursery phase 3 (14 d) and 4 (14 d), grower phase 1 (28 d) and 2 (28 d), and finisher phase 1 (28 d) and 2 (28 d). All pigs were transferred to a commercial processing plant where carcass characteristics were measured. Data were analyzed using Mixed procedure of SAS (Cary, NC) with maternal diet nutrient level, vitamin D source and the interaction as fixed effects. Progeny born from sows fed HyD diets had greater ADG in overall grower/finisher phases (P = 0.04) and during the whole trial (P = 0.03). This weight gain improvement increased the final BW, HCW, and yield percentage over StD derived progeny by 3.19 kg, 3.56 kg and 0.11% (P = 0.04, 0.02 and < 0.01), respectively. Dietary nutrient level had limited effect on progeny ADG and BW during the preslaughter period. The maternal vitamin D source did not affect progeny ADFI but overall G:F tended (P = 0.06) to be greater in pigs sourced from dams fed HyD . A maternal vitamin D by nutrient level interaction was observed for ADFI during grower/finisher phases (P = 0.05) and overall (P = 0.07) because progeny from gilts fed a low nutrient level had greater intake than cohorts from gilts fed an adequate nutrient diet, while ADFI was similar for all offspring from gilts fed HyD diets. These results indicate that manipulating nutrients during gilt development, or feeding HyD rather than StD to reproducing sows, can affect growth of their progeny to slaughter.

222 Effects of Nutritional Strategies of Growth Rate Manipulation During the Gilt Development Phases on Growth and Reproductive Performance

Abstract Our objective was to evaluate the effects of nutritional interventions for growth rate manipulation during the gilt development phases on growth and reproductive performance. A total of 810 Camborough L42 gilts from three gilt groups were received between 9 to 11 weeks of age. Gilts were individually weighed, and pens of gilts were allotted to one of two dietary treatments balanced by lot (birth week) and pen weight for a total of 24 pens/treatment. Treatments consisted of two levels of dietary nutrients:1) diets based on corn, soybean meal, and wheat middlings formulated to meet or exceed the PIC standardized ileal digestible (SID) lysine (Lys) recommendations with a total dietary fiber content (TDF) of 10, 10, and 11% (Adeq); and2) slower growing diets based on corn, soybean meal, wheat middlings, and corn germ where SID Lys was reduced by 6, 11, and 11%, dietary metabolizable energy level was reduced by 2.7, 4.6, and 4.7%, and TDF content was increased to 15, 18, and 20% (Low). Diets were fed in three phases as 27.2 to 54.5 kg, 54.5 to 81.8 kg, and 81.8 to 113.6 kg of body weight (BW). At the end of phase 3, gilts were individually weighed and the number of selected gilts per pen was recorded. After selection, gilts were heat checked with the date of heat-no-service (HNS) recorded and then sent to sow farms for breeding in the next recorded heat. Data were analyzed using generalized linear mixed models considering treatment as fixed effect, lot as random effect, and covariates were included if they were statistically significant and improved model fit. Gilts fed the Low diets had less overall average daily gain compared with gilts fed Adeq diets (P < 0.05; Table 1). This response was mainly driven by a marginal significant reduction (P < 0.10) in average daily feed intake for the gilts fed Low diets compared with Adeq, with no evidence for differences (P > 0.10) in overall feed efficiency. As a result of the reduction in growth rate, gilts fed the Low diets were 4.8 kg lighter (P < 0.05) at selection compared with gilts fed Adeq diets. There was no evidence for treatment differences in selection rate, breeding rate, age at first HNS nor age at first breeding (P > 0.10). In summary, results from this study demonstrated that nutritional strategies can be applied to reduce developing gilts growth rate without negatively affecting puberty, selection rate, or age at first breeding.

Duration of Mycoplasma hyopneumoniae detection in pigs following purposeful aerosol exposure

Swine disease elimination programs for Mycoplasma hyopneumoniae are commonly applied in the North American swine industry and may include the aerosolization of medium containing lung tissue to achieve population exposure prior to start. Field data has indicated M. hyopneumoniae PCR detection in pigs beyond 240 days post-herd closure (dphc; planned end of an elimination program) and is thought to contribute to disease elimination programs’ failure. Here, the duration of M. hyopneumoniae detection in sows and replacement gilts following aerosolized lung homogenate exposure, as part of a dual disease elimination program, was determined. A subset of sows and gilts from a commercial sow herd and off-site gilt development unit were longitudinally sampled to collect deep tracheal catheter secretions at various times post-exposure. Samples were tested for M. hyopneumoniae using a species-specific real-time PCR. A proportion of 58, 51, 52, 19, and 2% females were detected positive at 30, 60, 120, 180 and 240 dphc, respectively. Noteworthy, a greater proportion of gilts exposed at the off-site GDU were detected PCR positive for M. hyopneumoniae at each sampling event, compared to sows. In this study, assaying for genetic material in live female pigs showed extended detection of M. hyopneumoniae until at least 240 dphc. This data suggests persistence of M. hyopneumoniae longer than previously reported and highlights the importance of performing diagnostic testing to confirm negativity to the bacterium, prior to opening sow herds, especially late in the herd closure timeline.

Test 2

From November 2021 to February 2022, 37 swine nutritionists representing 29 production systems and 8 nutrition supplier companies in the United States were surveyed about added vitamins and trace mineral concentrations in swine diets. Respondents were asked to provide vitamin and trace mineral inclusion rates, weight ranges associated with each dietary phase, and number of sows utilizing their nutritional recommendations. Survey participants represented 4.38 million sows, or 72% of the U.S. industry. Data were compiled into 3 nursery phases (weaning to 15 lb; 15 to 25 lb; and 25 to 50 lb), 3 finishing phases (50 to 120; 120 to 220; and 220 lb to market), gilt development, gestation, lactation, and boar diets. Within each dietary phase, the vitamins and trace minerals of interest included: vitamin A, vitamin D, vitamin E, vitamin K, thiamin, riboflavin, niacin, pantothenic acid, pyridoxine, biotin, folic acid, vitamin B12, choline, vitamin C, carnitine, copper, iodine, iron, manganese, selenium, zinc, cobalt, and chromium. Descriptive statistics used included: average, weighted average (determined by the total number of sows), median, minimum, maximum, 25th percentile (lowest quartile), and 75th percentile (highest quartile). In addition, all average vitamin and trace mineral concentrations within each phase of production were compared to the requirement estimates reported in the NRC.[1] The results of this survey follow similar trends observed in a previous survey in 2016.[2] Nutritionists generally supplemented vitamins and trace minerals well above the NRC (2012) requirements. However, greater variation among respondents was observed in all vitamins and trace minerals, particularly in the fat soluble vitamins. Also, the use of alternative sources of vitamin D (25-OH-D3), E (natural, d-alpha-tocopherol), and organic or chelated minerals like copper, manganese, selenium, and zinc is becoming more frequent. In addition, comparisons to the most recent NRC (2012) requirement estimates highlight the necessity of future research to better understand vitamin and trace mineral requirements in swine diets.

Relationships between gilt development and herd production efficiency are revealed by simulation

<br />The gilt development level is a critical factor for profitability in the pig industry. To evaluate the impact of different gilt development levels on the age structure and production efficiency of female herds we used the performance data of a pig farm that was simulated over a ten-year period, with current production statistics from the Chinese pig industry as a basis for the model. In a herd of 600 breeding sows, we compared age structure, number born alive (NBA), longevity and sow lifetime productivity in three scenarios with gilt culling rates of 10%, 20%, and 30%. The results show that the gilt development has no significant effects on the age structure. The gilt development had no significant effects either on sow reproductive performance or production efficiency. However, the annual replacement rate, longevity, and sow lifetime productivity varied significantly in the three levels of gilt development (<i>P </i>< 0.01). We conclude that the gilt development is closely related to herd turnover and reproductive performance, and ultimately affects the cost of pig production. Gilt development is, therefore, an extremely important factor in an integrated pig production system.

Relationships of genomic estimated breeding values for age at puberty, birth weight, and growth during development in normal cyclic and acyclic gilts.

Managing replacement gilts to reach optimal body weight and growth rate for boar stimulation and first breeding is a key component for sow reproductive longevity and producer profitability. Failure to display pubertal estrus remains a major reason that gilts are culled from the herd. Puberty is metabolically gated so evaluating phenotypic and genetic relationships between birth weight and growth traits with age at puberty and acyclicity can provide valuable insight for efficient gilt development. Data on a litter of origin of the gilt, average daily gain at different stages of development, and age at puberty were available for age-matched cyclic (n = 4,861) and acyclic gilts (prepubertal anestrus, n = 578; behavioral anestrus, n = 428). Genomic estimated breeding values were predicted for each trait using genomic best linear unbiased prediction. Primiparous sows produced more acyclic gilts than multiparous sows (P < 0.05). Accounting for effects of parity and litter size, prepubertal anestrus gilts were heavier at birth and behaviorally anestrus gilts grew faster during the finisher period compared to cyclic gilts (P < 0.05), reflecting possible prenatal programming that negatively affects optimal pubertal development and antagonistic effects between adolescent growth and expression of estrus of gilts from first parity sows. Regression of phenotypic age at puberty with lifetime growth rate (birth to selection) showed a negative linear relationship whereas genomic estimated breeding values showed a negative quadratic relationship indicating that gilts with the least and greatest growth are less optimal as replacements. The slopes of these relationships are small with low negative phenotypic (r = -0.06) and genetic correlations (r = -0.13). The addition of data from acyclic gilts did not substantially change the estimates for genetic relationships between growth and pubertal onset. Although this study identified differences in birth weight and growth rate between cyclic and acyclic gilts the genetic relationships are weak, suggesting that genetic selection for these traits can be achieved separately. Avoiding the smallest and largest gilts in a cohort born to first parity sows could result in gilts with optimal development and reduce the proportion of replacement gilts that are acyclic.

Industry survey of added vitamins and trace minerals in U.S. swine diets.

From November 2021 to February 2022, 37 swine nutritionists representing 29 production systems and 8 nutrition supplier companies in the United States were surveyed about added vitamin and trace mineral concentrations in swine diets. Respondents were asked to provide vitamin premix and trace mineral concentrations, inclusion rates, and weight ranges associated with feeding phases. Survey participants represented 4.38 million sows, or 72% of the U.S. industry. Data were compiled into three nursery phases (phase 1, weaning to 7 kg; phase 2, 7 to 11 kg; and phase 3, 11 to 23 kg), three finishing phases (23 to 55 kg; 55 to 100 kg; 100 kg to market), gilt development, gestation, lactation, and boar. Within each dietary phase, the vitamins and trace minerals of interest included: vitamins A, D, E, and K, thiamin, riboflavin, niacin, pantothenic acid, pyridoxine, biotin, folic acid, vitamin B12, choline, vitamin C, carnitine, copper, iodine, iron, manganese, selenium, zinc, cobalt, and chromium. Descriptive statistics used included: average, weighted average (determined by the total number of sows represented), median, minimum, maximum, 25th percentile (lowest quartile), and 75th percentile (highest quartile). In addition, all average supplementation rates for vitamins and trace minerals within each phase of production were compared to the requirement estimates reported in the NRC (2012). Nutritionists generally supplemented vitamins and trace minerals well above the NRC (2012) requirement estimates. However, great variation among respondents was observed in all vitamins and trace minerals, particularly in the fat-soluble vitamins. Also, the use of alternative sources of vitamin D [25(OH)D3], E (natural, d-alpha-tocopherol), and organic or chelated minerals like copper, manganese, selenium, and zinc were being used by approximately 40% of the respondents, primarily in breeding herd and nursery diets. Understanding current supplementation practices may help develop research trials to test different vitamin and trace mineral inclusions and provide an industry benchmark of vitamin and trace mineral usage.

The effect of moderate energy and protein restriction during gilt development on changes in body weight and backfat depth and subsequent lactation performance.

Eighty-eight gilts [initial body weight (BW) 49.8 ± 0.8 kg] were recruited to determine the effects of moderate energy and protein restriction during the development period on changes in BW and backfat depth (BF) and subsequent lactation performance. Gilts were randomly assigned to one of four feeding programs: 1) standard commercial diet fed ad libitum (CON), 2) standard commercial diet fed 10% or 3) 20% below ad libitum, or 4) a high-fiber diet fed ad libitum [2.5 times more fiber (neutral detergent fiber) than the commercial diet to dilute net energy and crude protein by approximately 20% and 13%, respectively; FIB]. The gilts were housed individually and received the feeding programs between 90 and 190 (breeding) d of age and standard gestation and lactation diets thereafter. Litters were standardized to 12 ± 1 pigs within 48 h of farrowing; weaning occurred at 20.0 ± 0.4 d of age. Gilts that received the 20% restricted program had lower overall average daily feed intake (ADFI) during the development period (2.64 ± 0.04 kg; P < 0.05) versus all other feeding programs and gilts that received the 10% restricted program had lower ADFI than FIB and CON, which were not different (2.96 vs. 3.44 and 3.47 ± 0.04 kg for 10%, FIB and CON, respectively; P < 0.05). Plasma free fatty acid (FFA) concentrations on day 180 of age were lower for gilts that received the 10% and 20% restricted programs compared to gilts that received the FIB and CON programs, which were not different (97 and 86 vs. 220 and 149 ± 29 µEq/L, respectively; P < 0.05). Plasma concentrations of glucose, urea, prolactin, and IGF-1 were not different among feeding programs on day 180 of age. At breeding, gilts that received the FIB and 10% programs had lower BW and BF versus CON (145.7 and 144.8 vs. 155.2 ± 0.9 kg and 14.4 and 14.8 vs. 16.5 ± 0.2 mm for BW and BF, respectively; P < 0.05) but greater BW than gilts that received the 20% restricted program (137.9 kg; P < 0.05). The BW and BF of gilts did not differ at the end of gestation or at weaning. The ADFI of sows during lactation and offspring birth weight and growth rate during lactation and the 5-wk nursery period were not influenced by gilt development feeding program. Therefore, a high-fiber feeding program could be used in group-housing gilt-development scenarios, where feed is offered ad libitum, to control BW and BF prior to breeding without influencing milk production in the subsequent lactation period.

279 Identification of Potential Biomarkers of Reproductive Development in Vaginal Gene Expression Associated with Serum Concentrations of Reproductive Hormones at key Periods in Gilt Development

Abstract Early puberty in gilts is associated with long-term reproductive performance. The ability to predict who will achieve early puberty is limited to intensive and invasive collection of serial blood samples to assess reproductive hormones, which is not practical for on-farm use. The objective of this pilot study was to characterize changes in gene expression in the vaginal epithelium related to reproduction during key periods in pubertal development. Pre-pubertal gilts (n =13) in 2 cohorts were followed from 70 d of age until first estrus or 213-215 d of age. Blood and vaginal epithelia were collected at five key timepoints during reproductive development (d70/77, d100/110, d130, d160 and first estrus or end of trial). Total RNA were isolated from vaginal epithelia and relative gene expression of two toll-like receptors (TLR-4 and TLR-5), tacykinin precursor-3 (TAC-3), insulin-like growth factor-1 (IGF-1), and estrogen receptor (ER)-alpha was quantified by real time RT-PCR, relative to the expression of RPLP0. Of the 13 gilts, 3 exhibited estrus early (d169 to 174), 3 were average (d194 to 195), 2 were late (d203 to 213), 3 were deemed anestrus and 2 had a silent estrus (one prior to d160 and one after d200). Statistical analysis of relative expression of each gene relative to 70 d was performed using the PCR package in RStudio (version 1.2.5025). Analysis of gene expression utilized Fisher’s exact t-test for genes TLR-4, TLR-5 and TAC-3, and ANOVA for genes ER-alpha, IGF-1. Expression of IGF-1 and TAC-3 were up-regulated 9-fold and 7-fold, at the start of boar exposure (d 160; P &amp;lt; 0.05). Expression of ER-alpha tended to be upregulated 3-fold at 100 d of age (P = 0.08). Expression of TLR-4 and TLR-5 was not detected for most samples until standing estrus. These transcripts may be putative biomarkers for early estrus detection.

Gilt development to improve offspring performance and survivability.

Methods for developing incoming replacement gilts can indirectly and directly influence survivability of their offspring. Indirectly, having proper gilt development reduces culling rates and mortality, which increases longevity and creates a more mature sow herd. Older sows are more likely to have greater immunity than gilts and therefore can pass this along to their pigs in both quantity and quality of colostrum and milk, thus improving piglet survivability. Directly, proper gilt development will maximize mammary gland development which increases colostrum and milk production leading to large, healthy pig. As for the developing gilt at birth, increasing colostrum intake, reducing nursing pressure, providing adequate space allowance, and good growth rate can increase the likelihood that gilts successfully enter and remain in the herd. Light birth weight gilts (<1 kg) or gilts from litters with low birth weight should be removed early in the selection process. Gilts should be weaned at 24 d of age or older and then can be grown in a variety of ways as long as lifetime growth rate is over 600 g/d. Current genetic lines with exceptional growth rate run the risk of being bred too heavy, reducing longevity. On the other hand, restricting feed intake at specific times could be detrimental to mammary development. In these situations, reducing diet amino acid concentration and allowing ad libitum feed is a possible strategy. Gilts should be bred between 135 and 160 kg and at second estrus or later while in a positive metabolic state to increase lifetime productivity and longevity in the herd. Once bred, gilts should be fed to maintain or build body reserves without becoming over-conditioned at farrowing. Proper body condition at farrowing impacts the percentage of pigs born alive as well as colostrum and milk production, and consequently, offspring performance and survivability. Combined with the benefit in pig immunity conferred by an older sow parity structure, gilt development has lasting impacts on offspring performance and survivability.

34 Swine Breeding Herd Practicum Winternship

Abstract Approximately 70% of Animal Science students at Mizzou enroll without large animal experience, and commercial swine production exposure is very low (1-3%). As such, few consider careers in the swine industry. Winter break is 4 or 5 weeks long, allowing more than enough family time. An opportunity for full-time employment for students for 1-2 weeks over winter break on commercial sow units was arranged for 1 or 2 students each of 2 years. Host farms reported students were ‘shell shocked’ for the first 3 or 4 d, finding the scope of production overwhelming. A more formal program was designed to introduce students to modern swine breeding herd management, combining academic and field training over a period of several months. Eligible students have at least sophomore standing, can demonstrate a sincere interest in learning about careers in commercial pork production, and are able to commute to farms within 2 hr of campus. Cooperating farms provide hands-on experience on a modern commercial sow farm, help arrange housing, and pay students nominally during the winter break portion. Students are interviewed, and those selected to participate (n = up to 6) sign a code of conduct and participation agreement. In the fall semester they attend 8 hours of classroom instruction covering: gilt development; isolation/acclimation and biosecurity; reproductive anatomy/physiology; detection and synchronization of estrus; artificial insemination; pregnancy diagnosis; farrowing room preparation; induction of farrowing; obstetrical intervention; colostrum management; d 1 pig care; feeding and handling sows and piglets; careers. Interspersed on weekends during fall semester are 3 weekend days shadowing/working in pairs on commercial farms within 1.5 hours of campus. This training prepares them for ‘full time employment’ on a breeding farm, and students work for 1 or 2 weeks over the winter break on commercial sow units. Upon completion of the full-time employment phase, students prepare a written summary of their experience, upon which the majority of their grade rests.

189 Swine Production and Greenhouse Gases

Abstract Like much of agriculture, the swine industry is being asked to improve the sustainability of their production systems. In an integrated project, swine researchers, agronomists, and renewable energy scientists collected data to analyze the greenhouse gas and fossil energy footprints from Minnesota commercial swine production facilities as well as cropping and swine production data from the University of Minnesota West Central Research and Outreach Center. These environmental impacts were assessed using life cycle assessment (LCA) methodology in a cradle to farm gate study that examined the impacts on a per unit of liveweight pork produced basis. In the average commercial system, the GHG emissions were 2.41 kg CO2 equiv. per kg hog LW, with 75% emitted during the grow-finish phase, 6% in farrowing, 9% in the nursery phase, 7% in gestation, and 2% in gilt development. GHG emissions for direct operation of swine facilities were 0.15 kg CO2 equiv. per kg and accounted for 6% of emissions in the average commercial scenario. The majority of GHG emissions were in the production of crops and the breakdown of manure during storage. This talk will explore the methods, data, and results from this study and other similar environmental impact studies for swine production. It will also discuss how producers can measure impacts at their farms and implement changes to improve their environmental impacts. An important consideration in the discussion is the ability of producers to directly reduce fossil energy and its carbon footprint, because fossil energy consumption impacts both the environmental and economic aspects of swine production.

Effects of restricting energy during the gilt development period on growth and reproduction of lines differing in lean growth rate: responses in reproductive performance and longevity.

Longevity and reproductive performance are economically important traits in the swine industry that are largely influenced by nutrition and other environmental factors. Reproductive performance and longevity through 4 parities was assessed in gilts of 2 genetic lines developed on ad libitum access to feed or restricted to 75% of ad libitum intake. A total of 661 gilts were used in a 2 × 2 factorial with half of the gilts allocated to an ad libitum diet (AL; n = 330), while the other half were energy restricted by 25% (R; n = 331) from 123 to 235 d of age. All gilts were sired by an industry maternal line. Dams of the gilts were from either a Large White (W) by Landrace (L) industry maternal line or Nebraska Selection Line 45X, producing gilts designated as W × L (n = 355) and L45X (n = 306), respectively. Daily estrus detection began at 140 d of age to obtain age at puberty (AP). Gilts (n = 510) were mated on their second or later estrus, beginning at 240 d of age. Sow weight and backfat were recorded at 110 d of gestation and weaning of each parity. Number of live-born, stillborn, and mummified pigs per litter and piglet birth and weaning weights were recorded through 4 parities. More L45X than W × L and more AL than R gilts reached puberty by 230 d of age (P < 0.01). Dietary treatment did not affect probability to produce parities 1 to 4 or any litter trait analyzed. The L45X females tended to be more likely to produce parities 1 (P < 0.08) and 3 (P < 0.06), while W × L had heavier litters at birth (P < 0.01) and weaning (P = 0.01). Treatment by parity interactions (P < 0.01) existed for weight and backfat prior to farrowing and backfat at weaning, and weight at weaning exhibited a line by treatment by parity interaction (P = 0.04) as R sows had lower weights and backfats in earlier parities, but caught up to AL sows in later parities. A treatment by parity interaction (P < 0.01) was also present for backfat loss from farrowing to weaning as R gilts lost less backfat than AL in parities 1 and 2, but more in parities 3 and 4. No significant differences were detected between lines or treatments for lifetime production traits. The populations of pigs and data presented here provide a framework for a diverse array of further studies. Alternative approaches to restrict energy have been assessed in addition to methods of marker-assisted and genomic selection for improvement of litter size and sow longevity.

151 A Web Application to Establish Customized Feeding Program and Nutrient Specifications for Highly Prolific Sows

Abstract A web application was developed to provide a dynamic feeding program for PIC maternal dam lines during gilt development, gestation, peri-partum, lactation and wean-to-service interval (WSI). These recommendations for each production phase are based on peer-reviewed large-scale commercial research. The tool was developed using the Shiny package of R and includes CSS themes, html widgets, and JavaScript actions. Inputs, include pigs weaned per sow per year (PWSY), farrowing rate (FR), total born (TB), replacement rate, the existing feeding program of the breeding herd and the diet energy and standardized ileal digestible (SID) lysine (Lys) levels. Outputs include the feeding program, nutrient specifications and estimates of economic opportunity and performance improvement. The feeding program is based on user-defined energy and SID Lys levels for the gestation and lactation diets and the PIC nutrient recommendations for the breeding herd. Correspondingly, recommended specifications of other nutrients in the diets are provided and calculated based on the recommended feeding program. The tool provides economic and productivity opportunity analysis by comparing the PIC recommendations and the current user feeding programs. Improvement in PWSY is driven by the energy intake impact on caliper score during breeding and farrowing and consequently to FR and TB. This web application can be used by nutritionists and production managers to compare their current feeding practices to PIC recommendations for highly prolific sows. This will aid in their decision-making process regarding nutrition and feeding programs considering productivity and profitability outcomes.