Impact of early postweaning growth rate as affected by diet complexity and space allocation on subsequent growth performance of pigs in a wean-to-finish production system

Impact of Early Weaning on Development of the Swine Gut Microbiome

Considering that pigs are naturally weaned between 12 and 18 weeks of age, the common practice in the modern swine industry of weaning as early as between two and four weeks of age increases challenges during this transition period. Indeed, young pigs with an immature gut are suddenly separated from the sow, switched from milk to a diet consisting of only solid ingredients, and subjected to a new social hierarchy from mixing multiple litters. From the perspective of host gut development, weaning under these conditions causes a regression in histological structure as well as in digestive and barrier functions. While the gut is the main center of immunity in mature animals, the underdeveloped gut of early weaned pigs has yet to contribute to this function until seven weeks of age. The gut microbiota or microbiome, an essential contributor to the health and nutrition of their animal host, undergoes dramatic alterations during this transition, and this descriptive review aims to present a microbial ecology-based perspective on these events. Indeed, as gut microbial communities are dependent on cross-feeding relationships, the change in substrate availability triggers a cascade of succession events until a stable composition is reached. During this process, the gut microbiota is unstable and prone to dysbiosis, which can devolve into a diseased state. One potential strategy to accelerate maturation of the gut microbiome would be to identify microbial species that are critical to mature swine gut microbiomes, and develop strategies to facilitate their establishment in early post-weaning microbial communities.

Formulating Diets for Improved Health Status of Pigs: Current Knowledge and Perspectives

Our understanding of nutrition has been evolving to support both performance and immune status of pigs, particularly in disease-challenged animals which experience repartitioning of nutrients from growth towards the immune response. In this sense, it is critical to understand how stress may impact nutrient metabolism and the effects of nutritional interventions able to modulate organ (e.g., gastrointestinal tract) functionality and health. This will be pivotal in the development of effective diet formulation strategies in the context of improved animal performance and health. Therefore, this review will address qualitative and quantitative effects of immune system stimulation on voluntary feed intake and growth performance measurements in pigs. Due to the known repartitioning of nutrients, the effects of stimulating the immune system on nutrient requirements, stratified according to different challenge models, will be explored. Finally, different nutritional strategies (i.e., low protein, amino acid-supplemented diets; functional amino acid supplementation; dietary fiber level and source; diet complexity; organic acids; plant secondary metabolites) will be presented and discussed in the context of their possible role in enhancing the immune response and animal performance.

Functional amino acid supplementation attenuates the negative effects of plant-based nursery diets on the response of pigs to a subsequent Salmonella Typhimurium challenge

Functional amino acids (FAA) attenuate the effects of Salmonella challenge in pigs. However, this may be affected by protein source (PS). The objective of the present study was to determine the effects of nursery dietary PS and FAA supplementation on growth performance and immune status of pigs subsequently challenged with Salmonella Typhimurium (ST). Thirty-two weanling pigs (8.7 ± 0.23 kg) were assigned to a feeding program for 31 d in a 2 × 2 factorial arrangement. Factors were dietary PS (plant-based [PB] vs. animal-based [AB]) and FAA profile (basal [FAA-] or supplemented [FAA+; Thr, Met, and Trp at 120% of requirements]). Pigs were subsequently placed on a common grower diet and, after a 7-d adaptation, were inoculated with ST and monitored for 7 d postinoculation. Growth performance, rectal temperature, fecal score, gut health, ST shedding score, intestinal colonization and translocation, and blood parameters of acute-phase response and antioxidant balance were measured pre- and postinoculation. Data were analyzed with a 2 (AB vs. PB) × 2 (FAA- vs. FAA+) factorial arrangement of treatments and differences between means were considered significant at P ≤ 0.05. Postinoculation fecal score was worse, ST shedding, cecal myeloperoxidase, and cecal and colonic ST colonization were greater in PB compared to AB pigs (P < 0.05). Translocation of ST to spleen was decreased by FAA+ (P < 0.05), regardless of dietary PS. Postinoculation, AB pigs had greater average daily gain compared to PB-FAA- (P < 0.05). Pigs fed AB-FAA- showed increased average daily feed intake compared to PB-FAA- pigs (P < 0.05) and feed efficiency was increased in AB-FAA+ compared to PB-FAA- pigs (P < 0.05). Feeding PB ingredients in nursery diets seems to increase susceptibility of pigs to Salmonella. Moreover, FAA supplementation partially attenuated the negative effects of PB diets on the response of pigs to ST challenge.

Dihydromyricetin Enhances Intestinal Antioxidant Capacity of Growing-Finishing Pigs by Activating ERK/Nrf2/HO-1 Signaling Pathway

Oxidative stress is one of the main factors affecting animal health and reducing performance. The small intestine is the primary site of free-radical attacks. Dihydromyricetin (DHM) is a flavonoid compound with antioxidant, anti-inflammatory, and other biological activities, which is mainly extracted from Rattan tea. However, the effects of DHM on the intestinal antioxidant function of growing-finishing pigs and related mechanisms remain unclear. The aim of this study was to investigate the effect of dietary DHM supplementation on the intestinal antioxidant capacity of growing-finishing pigs and its mechanism. Our results show that dietary 0.03% DHM increased the activities of the total antioxidant capacity (T-AOC), catalase (CAT), and glutathione peroxidase (GSH-Px), decreased malondialdehyde (MDA) level, and upregulated protein expressions of HO-1, NQO1, nuclear Nrf2, and phospho-ERK (p-ERK) in the jejunum of growing-finishing pigs. Again, we found that 20 μmol/mL and 40 μmol/mL DHM treatment significantly upregulated the protein expression of HO-1 and promoted the nuclear translocation of Nrf2 and ERK phosphorylation in IPCE-J2 cells. ERK inhibitor PD98059 eliminated the DHM-induced upregulation of p-ERK, nuclear Nrf2, and HO-1. Our findings provided the first evidence that DHM enhanced the intestinal antioxidant capacity of growing-finishing pigs by activating the ERK/Nrf2/HO-1 signaling pathway.

Research Progress on Oxidative Stress and Its Nutritional Regulation Strategies in Pigs

Oxidative stress refers to the dramatic increase in the production of free radicals in human and animal bodies or the decrease in the ability to scavenging free radicals, thus breaking the antioxidation-oxidation balance. Various factors can induce oxidative stress in pig production. Oxidative stress has an important effect on pig performance and healthy growth, and has become one of the important factors restricting pig production. Based on the overview of the generation of oxidative stress, its effects on pigs, and signal transduction pathways, this paper discussed the nutritional measures to alleviate oxidative stress in pigs, in order to provide ideas for the nutritional research of anti-oxidative stress in pigs.

Postweaning mortality in commercial swine production. I: review of non-infectious contributing factors

Postweaning mortality is a complex causal matrix involving animal, environment, and infectious etiologic factors. Despite advances in swine productivity such as total pigs born, growth rate, feed intake, and efficiency, there have been modest to no improvements in postweaning mortality rates over the last several years. Industry averages for postweaning mortality range from four to eight percent for each the nursery, grow-finish, or wean-finish stages. Retrospective mortality causal analyses of individual databases have been performed. However, little information derived from meta-analysis, systematic review, or comprehensive literature reviews are available. In order to develop and evaluate strategies to comprehensively manage and reduce postweaning mortality, addressing the complexity and range of impact that factors have on mortality is necessary to identify and prioritize such contributing factors. Our objective is to describe the current state of knowledge regarding non-infectious causes of postweaning mortality, focusing on estimates of frequency and magnitude of effect where available. Postweaning mortality can be generalized into non-infectious and infectious causes, with non-infectious factors further classified into anatomic abnormalities, toxicity, animal factors, facility factors, nutritional inadequacies, season, and management factors. Important non-infectious factors that have been identified through review of literature include birth weight, pre-weaning management, weaning age and weight, and season. Additionally, reasons for mortality with a low incidence but a high magnitude include abdominal organ torsion/volvulus, sodium ion or ionophore toxicosis, or dietary imbalance due to feed formulation or manufacture error. Many interactive effects are present between and among infectious and non-infectious factors, but an important trend is the impact that non-infectious factors have on the incidence, severity, and resolution of infectious disease. Strategies to reduce postweaning mortality must consider the dynamic, complex state that forms the causal web. Control of postweaning mortality through understanding of the complexity, evaluation of mortality reduction strategies through rigorous scientific evaluation, and implementation remains an area of opportunity for continued growth and development in the global swine industry.

Diet complexity and l-threonine supplementation: effects on nutrient digestibility, nitrogen and energy balance, and body composition in nursery pigs

This study was conducted to investigate the effects of dietary complexity and l-Thr supplementation on energy and nutrient utilization in nursery pigs. Thirty-two nursery pigs (7.23 ± 0.48 kg) were randomly assigned to a 2 × 2 factorial treatment arrangement based on diet complexity (complex vs. simple) with different levels of l-Thr supplementation. The complex diet contained animal protein sources (e.g., fish meal and plasma) and a dairy product (e.g., dried whey) to mimic a conventional nursery diet. The simple diet was formulated with corn, wheat, and soybean meal. Both diets were supplemented with l-Thr to contain either 100% or 115% (SUP Thr) of the estimated standardized ileal digestible Thr requirement for 9 kg body weight pigs (NRC, 2012). The pigs were individually housed in metabolism crates and fed an experimental diet ad libitum for a 7-d adaptation period and 5 d of total but separate urine and fecal collection. On day 14, all pigs were euthanized to determine body composition. The diet complexity, l-Thr supplementation, and their interactions were considered main effects. Pigs fed the complex diet tended to exhibit greater (P < 0.10) apparent total tract digestibility (ATTD) of ash and urinary energy output than those fed the simple diet. The complex diet had greater (P < 0.05) digestible energy and net energy contents than the simple diet. Furthermore, the complex diet-fed pigs had lower (P < 0.05) plasma urea nitrogen concentration on day 14 than simple diet-fed pigs. The SUP Thr decreased (P < 0.05) ATTD of acid detergent fiber but trended (P < 0.10) toward a decrease in urinary nitrogen (N) output and an increase in N retention and body N mass. In conclusion, the simple diet for nursery pigs had lower digestible and net energy contents than a complex diet. The SUP Thr can improve N utilization and body protein deposition, irrespective of diet complexity.

The effect of creep feed intake and starter diet allowance on piglets' gut structure and growth performance after weaning

Diets offered to lactating and weaned piglets are the most expensive diets within pig production; however, the effect of these diets on lifetime pig performance is inconsistent. The objective of the current study was to investigate the impact of creep feed consumption during lactation and different starter diet allowances on piglets' gut structure and lifetime growth performance. In total, 320 pigs and 80 pigs (Landrace × Large White) were used after weaning in a 2 × 2 factorial arrangement to study growth performance and gut structure, respectively. At weaning, piglets that ate creep feed and piglets that were not offered creep feed during lactation were allocated to 2 kg/pig [low level (LL)] or 6 kg/pig [high level (HL)] of starter 1 diet (16.5 MJ DE/kg, 22.5% CP, and 1.7% total Lys) allowance. At weaning and at 1 and 3 wk after weaning, 8 piglets per treatment were sacrificed, and their small intestine morphology was evaluated (villus height and crypt depth). Piglets that ate creep feed had increased feed intake during the first week after weaning (P < 0.05), but no effect of creep feed intake was observed on piglets growth or gut structure during the postweaning period (both P > 0.05). Piglets that were fed HL after weaning had higher ADG and BW from weaning to 16 wk after weaning (both P < 0.05) and had lower feed conversion ratio (FCR) from weaning to 6 wk after weaning (P < 0.05). Piglets fed HL after weaning also had higher villi height and greater crypt depth than LL piglets at 3 wk after weaning (both P < 0.05). Creep feed consumption during lactation increases feed intake early after weaning, suggesting an improved capacity of piglets to cope with weaning, but did not influence their growth performance. Offering piglets 6 kg of starter diet enhances piglets' growth performance during the growing and finishing phase, probably by improving gut structure after weaning.

Genetic parameter estimates for growth performance of crossbred piglets

The direct heritability estimates for piglet weights in pre and post weaning stages were moderate and improvement through mass selection is plausible. In the pre-weaning stage, the piglets had maximum genetic potential at birth (BW) to be exploited through direct selection. The 3 random effects, namely direct additive, maternal additive and litter  permanent environmental effects had significant roles during different phases of pre-weaning growth and all must be included in the model used for formulating a breeding program. For post-weaning traits, the direct additive and permanent litter effects were the predominant factors governing the variability. The non-significance of postweaning maternal influence was as per expectation because the piglets moved away from maternal care after 8thweekof age.

Impact of housing nursery pigs according to body weight on the onset of feed intake, aggressive behavior, and growth performance

Housing nursery pigs according to body weight is an observed common practice in production systems and, supposedly, improves growth performance and reduces body weight (BW) variation. This 42-day study evaluated the effects of housing nursery pigs according to BW on performance, onset of feed intake, and aggressive behavior. A total of 504 pigs were ranked by BW at weaning and categorized into three groups of 168 pigs each: light, medium, and heavy. Pigs were randomly distributed to unsorted pens (Unsorted) containing 6 pigs of each weight group and sorted pens with 18 pigs from just one group per pen (Sorted). From weaning to day 3, pigs were fed a diet containing 1% iron oxide dye and rectal swabs presenting red coloration were evaluated to assess feed intake onset. Eight pens were video recorded to evaluate aggressive behavior. Sorted-Heavy pigs delayed the onset of feed intake (P ≤ 0.011) and presented more aggressive behaviors than Sorted-Light and Sorted-Medium pigs (P ≤ 0.036). In Unsorted, onset of feed intake showed no differences between weight categories. Also, no differences were observed for aggressive behavior between Sorted and Unsorted. Final BW showed no differences between Sorted and Unsorted pigs. The within-pen weight coefficient variation (CV) was slightly different (P = 0.042) between Sorted and Unsorted pigs (13.3 and 15.6%, respectively), at the end of the study. Thus, sorting nursery pigs by BW did not improve growth performance and also, induce a lag of post-weaning feed intake onset and increased fights in Heavy pigs.

Estimation of direct and maternal genetic parameters for individual birth weight, weaning weight, and probe weight in Yorkshire and Landrace pigs

As a result of selecting for increased litter size, newborn piglets are being born lighter and have a lower chance of survival. Raising fewer pigs to market weight would have a negative impact on the industry and farmer profitability; thus, understanding the genetics of individual growth performance traits will determine whether these traits will play an important role in pig breeding schemes. This study aimed to estimate genetic parameters for individual birth weight (BW), weaning weight (WW), and probe weight (PW) in Canadian-purebred Yorkshire and Landrace pigs. PW is a live weight taken at the time of the ultrasound measurements, when pigs weigh about 100 kg. Data were collected from 2 large and related breeding herds from 2003 to 2015. Four linear animal models were used, which included the following: Model 1-direct additive genetic effect; Model 2-direct additive genetic and maternal genetic effect; Model 3-direct additive genetic and common litter effect; and Model 4-direct additive genetic, maternal genetic, and common litter effect. The model which included all 3 random effects (Model 4) was determined to be the best fit to the data. Low to moderate direct heritability estimates were observed as follows: 0.15 ± 0.03 for BW, 0.04 ± 0.01 for WW, and 0.33 ± 0.03 for PW for the Yorkshire breed; and 0.05 ± 0.01 for BW, 0.01 ± 0.01 for WW, and 0.27 ± 0.03 for PW in the Landrace breed. As expected, the direct heritability estimates increased with age as a result of decreased maternal influence on the trait. Bivariate animal models were also used to estimate genetic and environmental correlations between traits. Strong direct genetic correlations were observed between BW and WW in both breeds. Based on the estimates of genetic parameters, individual BW could be evaluated and considered in breeding programs aiming to increase BW and improve subsequent performance. Different selection emphasis could also be applied on direct and maternal additive genetic effects on BW to optimize the breeding programs and improve selection efficiency.

Influence of various levels of milk by-products in weaner diets on growth performance, blood urea nitrogen, diarrhea incidence, and pork quality of weaning to finishing pigs

OBJECTIVE

This study was conducted to evaluate various levels of milk by-product in weaning pig diet on growth performance, blood profiles, carcass characteristics and economic performance for weaning to finishing pigs.

METHODS

A total of 160 weaning pigs ([Yorkshire×Landrace]×Duroc), average 7.01±1.32 kg body weight (BW), were allotted to four treatments by BW and sex in 10 replications with 4 pigs per pen in a randomized complete block design. Pigs were fed each treatment diet with various levels of milk by-product (Phase 1: 0%, 10%, 20%, and 30%, Phase 2: 0%, 5%, 10%, and 15%, respectively). During weaning period (0 to 5 week), weaning pigs were fed experimental diets and all pigs were fed the same commercial feed during growing-finishing period (6 to 14 week).

RESULTS

In the growth trial, BW, average daily gain (ADG), and average daily feed intake (ADFI) in the nursery period (5 weeks) increased as the milk by-product level in the diet increased (linear, p<0.05). Linear increases of pig BW with increasing the milk product levels were observed until late growing period (linear, p = 0.01). However, there were no significant differences in BW at the finishing periods, ADG, ADFI, and gain:feed ratio during the entire growing-finishing periods. The blood urea nitrogen concentration had no significant difference among dietary treatments. High inclusion level of milk by-product in weaner diet decreased crude protein (quadratic, p = 0.05) and crude ash (Linear, p = 0.05) of Longissimus muscle. In addition, cooking loss and water holding capacity increased with increasing milk product levels in the weaner diets (linear, p<0.01; p = 0.05). High milk by-product treatment had higher feed cost per weight gain compared to non-milk by-products treatment (linear, p = 0.01).

CONCLUSION

Supplementation of 10% to 5% milk by-products in weaning pig diet had results equivalent to the 30% to 15% milk treatment and 0% milk by-product supplementation in the diet had no negative influence on growth performance of finishing pigs.

Impact of nursery feeding program on subsequent growth performance, carcass quality, meat quality, and physical and chemical body composition of growing-finishing pigs

An experiment was conducted to examine the effect of the nursery feeding program on subsequent growth performance, carcass quality, meat quality, and physical and chemical body composition of growing-finishing pigs. Four dietary treatments were used in a 2 × 2 factorial arrangement of treatments based on diet complexity (Complex vs. Simple) and in-feed antibiotics (2,730 [+AB] vs. 0 [-AB] mg of chlortetracycline /kg].A total of 552 pigs, in 5 blocks, were weaned at 21 ± 2 d of age with an initial BW of 7.03 ± 0.07 kg. Each experimental block had 3 pens per treatment, with 8 pigs per pen in blocks 1 and 2, and 10 pigs per pen in the remaining 3 blocks. Nursery diets were fed in a 3-phase feeding program (Phase I, II, and III diets fed for 1, 2, and 3 wk, respectively). All pigs were fed common grower-finisher diets thereafter. Six pigs per treatment were slaughtered for chemical body composition analysis at wk 2, 8, 12, and 17 postweaning. An additional 11 pigs per treatment were slaughtered at wk 17 postweaning (approximately 115 kg BW or market weight) for analysis of carcass characteristics, chemical and physical body composition, and meat quality. During the nursery phase, ADG was lower (P < 0.05) for pigs fed the Simple diet than those fed the Complex diet (491 vs. 528 g/d). Antibiotic usage improved (P < 0.05) ADG in Phases II (408 vs. 438 g/d) and III (689 vs. 720 g/d). In Phase I and II, G:F was lower (P < 0.05) for pigs fed the Simple diet than those fed the Complex diet (0.46 vs. 0.58 and 0.75 vs. 0.78 in Phases I and II, respectively). During the grower phase, pigs previously fed -AB diets grew faster than pigs fed +AB diets (P < 0.05; 1,009 vs. 971 g/d). There were no treatment effects on overall ADG or G:F from weaning to finishing. Nursery feeding program did not affect carcass quality characteristics. However, pigs previously fed +AB diets tended (P = 0.07) to have increased LM depth. Nursery feeding program had no effect on objective or subjective meat quality measures, chemical body composition, or the weight of primal and retail carcass cuts at wk 17 postweaning, with the exception of primal belly weight. These results indicate that feeding simple nursery diets, or nursery diets without antibiotics, compromises growth performance during the nursery period but does not affect overall growth performance between weaning and market BW, carcass characteristics, and meat quality. Thus, feed costs for nursery pigs can be reduced by feeding simple diets without compromising market BW and carcass and meat quality.

Effects of varying nursery phase-feeding programs on growth performance of pigs during the nursery and subsequent grow-finish phases

The present study investigated the effects of varying durations of nursery diets differing in percentages of milk products on growth performance of pigs during the nursery phase (NP) and subsequent grow-finish phase (GFP) to find the feasibility of reducing the use of nursery diets containing costly milk products. A total of 204 21-d-old weanling female and castrated male pigs were subjected to one of three nursery phase feeding programs differing in durations on the NP 1 and 2 and GFP diets containing 20%, 7%, and 0% lacrosse and 35%, 8%, and 0% dried whey, respectively, in 6 pens (experimental units) for 33 d: HIGH (NP 1, 2 and 3 diets for 7, 14, and 12 d), MEDIUM (NP 2 and 3 for 14 and 19 d), and LOW (NP 2 and 3 and GFP 1 for 7, 14, and 12 d). Subsequently, 84 randomly selected pigs [14 pigs (replicates)/pen] were fed the GFP 1, 2 and 3 diets during d 54-96, 96-135, and 135-182 of age, respectively. The final body weight (BW) and average daily gain (ADG) of nursery pigs did not differ among the HIGH, MEDIUM, and LOW groups (14.8, 13.3, and 13.7 kg in BW and 273, 225, and 237 g in ADG, respectively). The average daily feed intake during the nursery phase was greater (p <0.01) in the HIGH group than in the MEDIUM and LOW groups, whereas the gain:feed ratio did not differ across the treatments. The BW on d 182 and ADG during d 54-182 were greater in the HIGH and MEDIUM groups vs. the LOW group (110.0, 107.6, and 99.6 kg in BW, respectively; p <0.01). The backfat thickness and carcass grade at slaughter on d 183 did not differ across the treatments. In conclusion, the MEDIUM program may be inferior to the commonly used HIGH program in supporting nursery pig growth. Nevertheless, the former appears to be more efficient than the latter in production cost per market pig whereas the LOW program is thought to be inefficient because of its negative effect on post-nursery pig growth.

Influence of feed flavors and nursery diet complexity on preweaning and nursery pig performance

In Exp. 1, 50 sows and their litters were used to determine the effects of adding a feed flavor to the creep diet on the proportion of pigs consuming creep feed ("eaters") and preweaning performance. Sows were blocked according to parity and date of farrowing and allotted to 2 experimental treatments: 1) litters fed a creep diet with no flavor (negative control) or 2) negative control diet with the feed flavor (Luctarom) included at 1,500 mg/kg. Both creep diets contained 1.0% chromic oxide and were offered ad libitum from d 18 until weaning at d 21. Adding flavor to the creep diet did not (P > 0.41) affect weaning weights, total BW gain, ADG, total creep feed intake, daily creep feed intake, or the proportion of creep feed eaters in whole litters. In Exp. 2, 480 weanling pigs (6.58 ± 0.41 kg; 20 ± 2 d) from Exp. 1 were randomly selected by preweaning treatment group, blocked by initial BW, and allotted to 1 of 8 treatments in a randomized complete block design to determine the interactive effects of preweaning exposure to flavor (exposed vs. unexposed), nursery diet complexity (complex vs. simple), and flavor addition to nursery diets (with vs. without flavor). Each treatment had 10 replications (pens) with 6 pigs per pen. Diets with flavor were supplemented with the flavor at 1,500 mg/kg in phase 1 diets and 1,000 mg/kg in phase 2 diets. A tendency for a 3-way interaction for ADG from d 5 to 10 (P = 0.10), 10 to 28 (P = 0.09), and 0 to 28 (P = 0.06) was observed. Postweaning ADG of pigs exposed to flavor in creep feed and fed flavored complex diets in the nursery was greater than pigs in any other treatment combination. Increasing diet complexity improved (P < 0.01) ADG and ADFI during both postweaning phases. Adding flavor to creep feed had no effect on G:F (P > 0.34) and pig BW (P > 0.45) in both postweaning periods. Adding flavor to starter diets tended to improve ADFI (P = 0.06) during d 0 to 5. In conclusion, adding flavor to the creep feed did not affect litter creep feed intake, the proportion of piglets consuming creep feed, or preweaning performance when creep was provided for 3 d before weaning. Preweaning exposure to feed flavor improved postweaning ADG in pigs fed complex diets supplemented with the same flavor but did not influence performance of pigs fed simple diets.

Effects of grouping unfamiliar cohorts, high ambient temperature and stocking density on live performance of growing pigs

Ninety-six crossbred intact male pigs (34.5 +/- 3.5 kg BW) were allocated by weight and vocalization score to a 2 x 2 x 2 dynamic experimental design including two stocking densities (1 or 2 m(2)/pig), two temperatures (22 degrees C and 30 degrees C), and two short groupings of unfamiliar cohorts (six pigs as one pig per group, and six pigs per group). The study was conducted over 8 wk, and live weight gain (WTG) and feed intake (FI; as-fed basis) were measured weekly. During the first week, pigs were housed in individual pens from four independent rooms. To group pigs, pen partitions were removed. Pigs were grouped in Rooms 2 and 3 from wk 2 to 4, and in Rooms 1 and 4 during wk 7. Temperature was increased from 22 degrees C to 30 degrees C in Rooms 1 and 2 during wk 4 and 7. Pen partitions were replaced in Rooms 2 and 3 at the end of wk 4 and in Rooms 1 and 4 at the end of wk 7 to return pigs to their individual pens. Grouping pigs decreased FI during wk 3 (15.08 +/- 0.43 vs. 14.03 +/- 0.41 kg P < 0.10), and during wk 7 (17.42 +/- 0.46 vs. 14.24 +/- 0.41 kg; P < 0.01). In addition, grouping had a negative effect (P < 0.001) on WTG at wk 3 (7.38 +/- 0.28 vs. 5.71 +/- 0.28 kg) and at wk 7 (6.70 +/- 0.26 vs. 2.99 +/- 0.26 kg). For grouped pigs, raising the temperature decreased (P < 0.01) WTG (7.49 +/- 0.29 vs. 6.41 +/- 0.29 kg during wk 4, and 3.37 +/- 0.38 vs. 2.62 +/- 0.38 kg during wk 7). Mean FI was decreased (P < 0.01) with the 30 degrees C treatment during wk 7 only (15.49 +/- 0.33 kg at 22 degrees C compared with 12.99 +/- 0.33 kg at 30 degrees C). Compensatory feed intake was evident after the treatments had ceased at wk 6, whereby previously heat-treated grouped pigs had a higher FI (17.97 +/- 0.45 kg) than the animals individually housed at 22 degrees C (12.99 +/- 0.33 kg). Stocking density effects were noted after the grouping and high temperature treatments had ceased. For instance, during wk 5, low-density-housed pigs grew faster (P < 0.001) than their high-density counterparts (9.04 +/- 0.38 vs. 7.49 +/- 0.29 kg). In conclusion, under the conditions of this study, the grouping of unfamiliar cohorts and high ambient temperature treatments had a detrimental effect on pig performance, and these effects were reversible.

Effects of diet complexity and dietary lactose levels during three starter phases on postweaning pig performance123

Four experiments involving 1,005 crossbred pigs weaned at 19 +/- 2 d of age evaluated the effect of diet complexity and lactose level on starter pig performances. Experiment 1 was a randomized complete block (RCB) conducted in nine replicates with 135 pigs. A complex diet using several protein sources, a semicomplex diet with fewer protein sources, and a simple diet of corn and soybean meal comprised the three treatment groups. All diets contained 25% lactose (as-fed basis) with lysine (total) constant from d 0 to 14 (1.55%) and d 14 to 28 (1.45%), respectively. Gain, feed intake, and feed efficiency (P < 0.05) improved as diet complexity increased during both periods. In Exp. 2, 240 pigs in eight replicates in a RCB design were fed complex diets, but dietary lactose (total; as-fed basis) levels ranged from 10 to 35% in 5% increments from 0 to 14 d after weaning. From 14 to 30 d, a common 17% lactose diet was fed to evaluate the effects of early lactose level on subsequent responses. Gains (P < 0.05) increased for the 0- to 7- and 0- to 14-d periods as lactose increased to 30%. Similar gains resulted for all treatment groups from 14 to 30 d after weaning, with no evidence of compensatory responses to early lactose levels. In Exp. 3, 330 pigs were fed complex diets. From 0 to 7 d after weaning, the diets contained 25% lactose (as-fed basis), and from 7 to 21 d postweaning, the lactose levels ranged from 7 to 31% in 5% increments. Gain (P < 0.01) and feed efficiency (P < 0.05) increased from 7 to 21 d to the 17% lactose level. In Exp. 4, 300 pigs were fed 25 and 17% (as-fed basis) lactose diets from 0 to 7 and 7 to 21 d postweaning, respectively. From 21 to 35 d postweaning, lactose levels of 0 to 20% in 5% increments were added to a corn-soybean meal diet. The experiment was conducted as a RCB design in 12 replicates. Gain (P < 0.05) and feed intake (P < 0.05) increased to 10 to 15% lactose. When the data from Exp. 4 were partitioned into lighter (15.0 kg) and heavier (17.7 kg) pig weight replicates, only the lighter replicates had significant improvements in gain, feed intake, and feed efficiency (P < 0.05) in response to dietary lactose. These results demonstrated that starter pigs performed better when fed complex diets, that dietary lactose levels of 25 to 30% (to 7 kg BW) during the initial week postweaning, 15 to 20% lactose during d 7 to 21 (to 12.5 kg BW), and 10 to 15% lactose during d 21 to 35 postweaning (to 25 kg BW) resulted in maximum performance.

Effect of restricted postweaning growth resulting from reduced floor and feeder-trough space on pig growth performance to slaughter weight in a wean-to-finish production system

The effect of reduced pig growth rate postweaning as a result of restricted floor space and feeder trough space on subsequent growth to slaughter was investigated in a wean-to-finish system. Crossbred pigs (n = 1,728) were used in a randomized block design with a 2 x 2 x 2 factorial arrangement of treatments: 1) floor space (high [0.630 m2/pig] vs. low floor space [0.315 m2/pig]), 2) feeder trough space (unrestricted [4 cm/pig] vs. restricted feeder trough space [2 cm/pig]), and 3) period of imposing floor- and feeder-trough-space treatments (12 vs. 14 wk postweaning). Growth performance was measured from weaning (5.5 +/- 0.01 kg of BW; 17 d of age) to slaughter (the end of wk 25 postweaning). From the end of the treatment period to the end of wk 25, pigs on all treatments had the same floor and feeder trough space. Pigs with low floor space had lower (P < 0.01) ADG, ADFI, and gain:feed ratio than those with high floor space, and were therefore lighter (P < 0.05) at the end of the postweaning treatment period. Pigs given the restricted feeder trough space had lower (P < 0.05) ADFI, similar (P > 0.05) ADG, and higher (P < 0.01) gain:feed ratio than those with unrestricted feeder trough space during the treatment period. Pigs in the 14-wk treatment period had higher (P < 0.01) ADG and ADFI, but lower gain:feed than those in the 12-wk treatment during that period. In the subsequent period, from the end of treatment to wk 25, there was an interaction (P < 0.05) between floor space and treatment period; the difference in ADG and gain:feed for pigs on low vs. high floor space was greater for the 14-wk than the 12-wk treatment period. However, low-floor-space pigs tended (P = 0.06) to be lighter than high-floor-space pigs at the end of wk 25 postweaning. Neither feeder trough space nor treatment period affected pig growth performance during the period from the end of treatment to wk 25. Carcass backfat and longissimus depths at the end of wk 25 were not influenced (P > 0.05) by treatment. In summary, pigs with restricted growth due to low floor space until either 12 or 14 wk postweaning had increased growth and feed efficiency in the subsequent period to wk 25 postweaning, with only a slight effect on BW and no effect on carcass measures.