Characteristics of lipids and their feeding value in swine diets

In livestock diets, energy is one of the most expensive nutritional components of feed formulation. Because lipids are a concentrated energy source, inclusion of lipids are known to affect growth rate and feed efficiency, but are also known to affect diet palatability, feed dustiness, and pellet quality. In reviewing the literature, the majority of research studies conducted on the subject of lipids have focused mainly on the effects of feeding presumably high quality lipids on growth performance, digestion, and metabolism in young animals. There is, however, the wide array of composition and quality differences among lipid sources available to the animal industry making it essential to understand differences in lipid composition and quality factors affecting their digestion and metabolism more fully. In addition there is often confusion in lipid nomenclature, measuring lipid content and composition, and evaluating quality factors necessary to understand the true feeding value to animals. Lastly, advances in understanding lipid digestion, post-absorption metabolism, and physiological processes (e.g., cell division and differentiation, immune function and inflammation); and in metabolic oxidative stress in the animal and lipid peroxidation, necessitates a more compressive assessment of factors affecting the value of lipid supplementation to livestock diets. The following review provides insight into lipid classification, digestion and absorption, lipid peroxidation indices, lipid quality and nutritional value, and antioxidants in growing pigs.

Consumption of Oxidized Soybean Oil Increased Intestinal Oxidative Stress and Affected Intestinal Immune Variables in Yellow-feathered Broilers

This study investigated the effect of oxidized soybean oil in the diet of young chickens on growth performance and intestinal oxidative stress, and indices of intestinal immune function. Corn-soybean-based diets containing 2% mixtures of fresh and oxidized soybean oil provided 6 levels (0.15, 1.01, 3.14, 4.95, 7.05, and 8.97 meqO₂/kg) of peroxide value (POV) in the diets. Each dietary treatment, fed for 22 d, had 6 replicates, each containing 30 birds (n = 1,080). Increasing POV levels reduced average daily feed intake (ADFI) of the broilers during d 1 to 10, body weight and average daily gain at d 22 but did not affect overall ADFI. Concentrations of malondialdehyde (MDA) increased in plasma and jejunum as POV increased but total antioxidative capacity (T-AOC) declined in plasma and jejunum. Catalase (CAT) activity declined in plasma and jejunum as did plasma glutathione S-transferase (GST). Effects were apparent at POV exceeding 3.14 meqO₂/kg for early ADFI and MDA in jejunum, and POV exceeding 1.01 meqO₂/kg for CAT in plasma and jejunum, GST in plasma and T-AOC in jejunum. Relative jejunal abundance of nuclear factor kappa B (NF-κB) P50 and NF-κB P65 increased as dietary POV increased. Increasing POV levels reduced the jejunal concentrations of secretory immunoglobulin A and cluster of differentiation (CD) 4 and CD8 molecules with differences from controls apparent at dietary POV of 3.14 to 4.95 meqO₂/kg. These findings indicated that growth performance, feed intake, and the local immune system of the small intestine were compromised by oxidative stress when young broilers were fed moderately oxidized soybean oil.

Evaluating the quality of feed fats and oils and their effects on pig growth performance

Feed fats and oils provide significant amounts of energy to swine diets, but there is large variation in composition, quality, feeding value, and price among sources. Common measures of lipid quality include moisture, insolubles, and unsaponifiables (MIU), titer, and free fatty acid content, but provide limited information regarding their feeding value. Lipid peroxidation is an important quality factor related to animal growth performance and health, but maximum tolerable limits in various lipids have not been established. Several indicative assays can be used to detect the presence of various peroxidation compounds, but due to the complexity and numerous compounds produced and degraded during peroxidation process, no single method can adequately determine the extent of peroxidation. Until further information is available, using a combination of peroxide value, thiobarbituric acid reactive substances (TBARS), and anisidine value appear to provide a reasonable assessment of the extent of peroxidation in a lipid at a reasonable cost. However, fatty acid composition of the lipid being evaluated should be considered when selecting specific assays. Predictive tests can also be used to estimate the stability or susceptibility of lipids to peroxidation and include active oxygen method, oil stability index, and oxygen bomb method. A review of 16 published studies with pigs has shown an average decrease of 11.4% in growth rate, 8.8% feed intake fed isocaloric diets containing peroxidized lipids compared to diets containing unperoxidized lipids of the same source. Furthermore, serum vitamin E content was generally reduced and serum TBARS content was increased when peroxidized lipids were fed in these studies, suggesting that feeding peroxidized lipids negatively affects metabolic oxidative status of pigs. However, it is unclear if antioxidants are useful additions to lipids to maintain optimal nutritional value, or if their addition to swine diets is beneficial in overcoming a metabolic oxidative challenge.

Effect of feeding peroxidized dried distillers grains with solubles to sows and progeny on growth performance and metabolic oxidative status of nursery pigs

This experiment evaluated the effects of including peroxidized corn dried distillers grains with solubles (DDGS) in diets for sows and nursery pigs on growth performance, vitamin E (VE), and Se status, and the incidence of mulberry heart disease (MHD) of nursery pigs. Sows (n = 12) were fed corn-soybean meal diets (C-SBM) or C-SBM diets with DDGS (40% and 20% in gestation and lactation, respectively) for 3 parities. In the third parity, 108 weaned pigs (BW = 6.6 ± 0.36 kg) were blocked by BW within litter, assigned to pens (2 pigs/pen; 5 and 4 pens per litter for groups 1 and 2, respectively), and pens were assigned 1 of 3 nursery diets: 1) corn-soybean meal (CON), 2) 30% peroxidized DDGS (Ox-D), and 3) 30% Ox-D with 5 × NRC (1998) level of VE (Ox-D+5VE) for 7 wk, in a 2 × 3 factorial arrangement of sow and nursery diets (n = 9 pens/treatment). The peroxidized DDGS source in nursery diets contained concentrations of thiobarbituric acid reactive substances (TBARS) and peroxide values that were 25 and 27 times greater than a reference corn sample. Sow colostrum, milk, and serum, as well as pig serum and liver samples, were analyzed for α-tocopherol and Se concentrations. Pig serum was analyzed for glutathione peroxidase activity (GPx), TBARS, and sulfur-containing AA (SAA). Pig hearts were evaluated for gross and histopathological lesions indicative of MHD, but none were detected. Pigs from sows fed DDGS tended to have reduced (P = 0.07) VE in serum during lactation and reduced VE at weaning (P < 0.01; 5.6 vs. 6.7 ± 0.1 µg/mL) compared with pigs from sows fed C-SBM. Inclusion of DDGS in sow diets reduced the VE status of pigs during lactation, but not in the nursery when MHD can be a concern. Pigs fed Ox-D+5VE (P = 0.08) tended to have, and those fed Ox-D (P = 0.04) had greater ADFI than pigs fed CON, but ADG was not affected (P > 0.1) by nursery diet. Feeding Ox-D or Ox-D+5VE increased (P < 0.05) serum α-tocopherol compared with CON (2.5, 2.8, and 3.4 ± 0.09 µg/mL, respectively), but TBARS and GPx were not affected by nursery diet. Serum concentration of SAA was 40% to 50% greater (P < 0.01) for pigs fed Ox-D or Ox-D+5VE compared with those fed C-SBM, which was likely due to greater (P < 0.01) SAA intake for pigs fed Ox-D. The antioxidant properties of SAA may have spared VE and Se and masked any effect of Ox-D on metabolic oxidation status. Therefore, increasing the dietary VE concentration was unnecessary in nursery diets containing Ox-D.

The effects of ovariectomy on meat performance and expression of GH/IGF-I in young goats

Zhang, L., Wang, Y.-y., Fu, M.-z., Li, G., An, N., Li, S.-y. and Zhou, Z.-q. 2014. The effects of ovariectomy on meat performance and expression of GH/IGF-I in young goats. Can. J. Anim. Sci. 94: 619–626. Experiments were carried out to investigate the effects of ovariectomy on meat production efficiency and to explore the expression of GH/IGF-I in young goats. Animal performance, meat quality, levels of serum growth hormone (GH) and insulin-like growth factor 1 (IGF-I), and mRNA levels of three key genes [GH Receptor (GHR), IGF-I and IGF-I Receptor (IGF-IR)] in longissimus dorsi and biceps femoris muscles were measured. The results show that carcass weight, net meat mass, fat weight and loin eye area of ovariectomized goats were higher than those of the controls, and ovariectomized goats lost 0.40 kg of bone weight (P<0.05). There was no statistically valid difference for the color, pH, water-holding capacity, or cooking rate of meat (P>0.05) between the two groups, except for the shear value, which was significantly lower in the Ovx group than in the control group (P<0.05). The results of this research show for the first time a significant trend (P<0.05) for serum GH and IGF-I in the direction of increasing in ovariectomized goats. Furthermore, the mRNA levels of GHR, IGF-I and IGF-IR in muscle were all up-regulated, except for the IGF-I gene in biceps femoris, by ovariectomy. In summary, ovariectomy showed a beneficial promotion in animal performance, but did not reduce meat quality, and increased serum GH and IGF-I and mRNA expression levels of GHR, IGF-I and IGF-IR in young female goats.

Supplementing antioxidants to pigs fed diets high in oxidants: I. Effects on growth performance, liver function, and oxidative status

The objective of the study was to determine the effects of a dietary antioxidant blend (ethoxyquin and propyl gallate) and vitamin E on growth performance, liver function, and oxidative status in pigs fed diets high in oxidants. Crossbred barrows (n=100, 10.91±0.65 kg BW, 36±2 d of age, Landrace×Duroc) were allotted to 5 treatments on the basis of BW (5 replicate pens per treatment, 4 pigs per pen). Treatments included 1) HO, high-oxidant diet containing 5% oxidized soybean oil and 10% PUFA source (providing 2.05% docosahexaenoic acid in the diet), 2) VE, the HO diet with 11 IU/kg of added vitamin E, 3) AOX, the HO diet with antioxidant blend (135 mg/kg), 4) VE+AOX, the HO diet with both vitamin E and antioxidant blend, and 5) SC, a standard corn-soy control diet. The trial lasted for 118 d; on d 83, the HO diet pigs were switched to the SC diet because the animals were displaying very poor health. Compared with SC pigs, HO pigs had decreased ADG (0.92 vs. 0.51 kg for d 26 to 55, 1.29 vs. 0.34 kg for d 56 to 82; P<0.05) and ADFI (1.84 vs. 0.96 kg for d 26 to 55, 3.41 vs. 1.14 kg for d 56 to 82; P<0.05). However, switching the HO pigs to the SC diet resulted in HO pigs having a greater ADG than VE-fed pigs from d 83 to 118 (0.90 vs. 0.60 kg; P<0.05). The antioxidant blend restored pig performance to a level similar that of pigs fed the SC diet (P>0.05) with greater G:F for the entire period (0.44 vs. 0.38; P<0.05). A greater liver to BW ratio was found in HO compared with other treatments on d 55 and in VE on d 118. Total bilirubin concentration in plasma of HO pigs on d 55 was greater than that in VE+AOX pigs (P<0.05), whereas on d 118, bilirubin concentration in VE was higher than those in VE+AOX and SC (P<0.05). A similar trend was observed in aspartate transaminase. Plasma concentrations of thiobarbituric acid reactive substances (TBARS) and carbonyl were elevated (P<0.05) in the HO pigs compared with the SC pigs on d 55 but not on d 118. Liver TBARS and carbonyl concentrations showed a similar trend, except that HO pigs had the greatest carbonyl concentration on d 118. Pigs fed AOX diets had plasma and liver TBARS and carbonyl concentrations similar to those fed SC diets. In the oxidative stress model used in this study, dietary addition of antioxidant blend or antioxidant blend+vitaimin E was effective in improving growth, liver function, and plasma markers of oxidative stress, but VE alone was not.

Dietary antioxidant supplementation enhances lipid and protein oxidative stability of chicken broiler meat through promotion of antioxidant enzyme activity

Recent nutrigenomic studies have shown that animal nutrition can have a major influence on tissue gene expression. Dietary antioxidant supplements can enhance the quality of meat through modification of tissue metabolic processes. This study investigated the influence of dietary antioxidants and quality of oil on the oxidative and enzymatic properties of chicken broiler breast meat stored in an oxygen-enriched package (HiOx: 80% O₂/20% CO₂) in comparison with air-permeable polyvinylchloride (PVC) or skin packaging systems during retail display at 2 to 4°C for up to 21 d. Broilers were fed either a diet with a low-oxidized (peroxide value 23 mEq of O₂/kg) or high-oxidized (peroxide value 121 mEq of O₂/kg) oil, supplemented with or without an algae-based Se yeast and organic mineral antioxidant pack for 42 d. Lipid and protein oxidation and tissue enzymatic activity were analyzed. In all packaging systems, lipid oxidation (TBA reactive substances) was inhibited by up to 32.5% (P < 0.05) with an antioxidant-supplemented diet when compared with diets without antioxidants, particularly in the HiOx and PVC systems. Protein sulfhydryls were significantly protected by antioxidant diets (e.g., by 14.6 and 17.8% for low-and high-oxidized dietary groups, respectively, in PVC d 7 samples). Glutathione peroxidase, catalase, and superoxide dismutase activities were significantly higher (P < 0.05) in antioxidant-supplemented diets compared with the basal diet, regardless of oil quality. Also, serum carbonyls were lower in broilers fed a low-oxidized antioxidant-supplemented treatment. The results demonstrate that dietary antioxidants can minimize the oxidative instability of proteins and lipids, and the protection may be linked to improved cellular antioxidant enzymatic activity.