Data sheets: Lard

Introduction

Lard is defined as animal fat extracted from clean, healthy tissues from pigs that were in good health at the time of slaughter. For excellent quality, it is produced using only certain fatty cuts from the trimmings of the carcass in the slaughterhouse. But in reality, other scraps from the carcass are often included in the processing in varying proportions (skin, head skin trimmings, fat recovered during cleaning). The lard is obtained by a melting process of the fat, followed by a clarifying process to remove traces of protein, water, and solid particles. The processing and separation of the fat fraction from the rest of the tissues can be done in facilities adjacent to the slaughterhouse itself or in independent processing plants. For this reason, it is possible to find lard that is exclusively porcine in origin or that is mixed with other animal species (for example, with poultry fat). The melting point or titer of lard is between 20ºC and 40ºC, which is lower than that of tallow (Titer >40ºC) and higher than that of other oils that are present in liquid form (<20ºC). The fatty acid profile and content of the lard can vary depending on the origin (porcine or mixed) and the diet of the animals from which the lard was obtained (e.g. incorporating diets rich in oleic acid), making it very difficult to find a product with a constant and stable composition between batches and over time. The amount of fat (etherl extract, EE), moisture, impurities, and unsaponifiables, fatty acid profile, and amount of free fatty acids are basic parameters for determining the quality of the lard.

There is an interest in using lard as a feed ingredient due to its high energy content and its contribution of essential fatty acids (mainly linoleic acid). Lard contains considerable proportions of palmitic acid, stearic acid, oleic acid and linoleic acid. There are small amounts of palmitoleic acid and traces of linolenic acid, arachidonic acid and myristic acid. This composition determines the ratio between saturated and unsaturated fatty acids. It is used as an energy source for all physiological stages of the pig, although in lesser amounts for nursing and recently weaned pigs (<=3%), due to its high degree of saturation and moderate digestibility. The energy value of the lard will depend basically on the amount of total fat (saponifiable fraction since moisture, impurities and unsaponifiables have no energy value (considering it the non-elutable fraction if we add the oxidation products).

Comparative study of nutritional values

The systems used in the comparison are: FEDNA (Spain), CVB (Netherlands), INRA (France), NRC (USA), and Brazil.

Unlike other feed ingredients, the composition of lard is not differentiated according to quality, although chemically this would be possible by taking into account the differences in both moisture and ether extract. However, INRA and NRC do not give values for moisture and NRC does not give a value for the amount of fat (% of ether extract, EE). BRAZIL and FEDNA propose moisture values between 0.4 and 1% assuming that any component that is not moisture is total fat. Only CVB (even presenting a moisture value of 0.6%), considers a deviation of 0.1% between the dry matter and the total fat content, indicating that there are other compounds that are not fat (for example, impurities and unsaponifiables).

The NE (kcal/kg) values proposed by the different systems has a range of 650 kcal; with BRAZIL giving the lowest value (7100 kcal/kg) and FEDNA giving the highest value of 7750 kcal/kg. These changes in the NE value are not justified by the variations presented in terms of DM and EE, and could be related to changes in the fatty acid profile and their position in the glycerol molecule. In addition, parameters that determine NE value are not defined in all tables such as water content, impurities, unsaponifiables, amount of free fatty acids (FFA) and oxidation products. With the exception of INRA, the other European systems (FEDNA and CVB), which often use lard as an energy source, give higher values of NE compared to BRAZIL and NRC who give lower values for energy. Meanwhile, a positive correlation (r2 = 0.46) is observed between the fat digestibility coefficients and the final energy value. With the exception of FEDNA and CVB, it is surprising that all other systems give an ME value for lard that is between 0.60 and 2.95% lower than the DE value, although losses through urine or gas should be negligible.

The profiles and amounts of fatty acids are very similar between systems (with deviations between 0.02 and 0.98) with the exception of CVB which gives higher values for saturated fatty acids compared to the average of the other systems (+30% myristic acid, +12% palmitic acid and +26% stearic acid) and lower amounts of palmitoleic (-16%) and oleic acid (- 8%). This fact determines the ratio between saturated and unsaturated fatty acids of FEDNA (0.66), INRA (0.73), NRC (0.70) and BRAZIL (0.71) compared to CVB (0.88) which is higher. In this respect, the role of the diet of the animals from which the lard was made, can explain the reason for this difference.

Some systems (FEDNA, NRC) provide other reference values (iodine value as an indicator of the degree of saturation, titer or melting point and saponification value) that complement the information provided by the fatty acid profile, but do not add to it. None of the systems indicate the free fatty acid content, although it is a value that is usually incorporated into the equations for predicting NE. Nor is there any reference to the joint value, MIU (moisture, impurities and unsaponifiables) as an index or measure inversely related to the energy value. The water in lard can promote the proliferation of fat-hydrolyzing bacteria and can facilitate the action of enzymes with hydrolysis capacity. Fat-soluble impurities can be detected in the raw material, appearing as dark spots (polyethylene traces). And finally, the unsaponifiable matter is the material in the lard that cannot be converted into soap by the use of an alkali. These three parameters joined in a single index could be one of the best indicators to correct the energy value in the formulation matrix. Based on the mentioned values, lard can be classified as first quality if it has MIU values of <0.5, <0.2, and <1 respectively; a peroxide value <5 (indicator of primary oxidation); iodine value of 65 and FFA <2. Second quality lard has MIU values of <1;<1, and <2; peroxide value <8; iodine value 62; and FFA <10. This of course changes its energy value and the cost of the raw material.

Recent research findings

1. Dietary fat preference and effects on performance of piglets at weaning.

Piglets pre-trained to experience reducing lipid inclusion showed different subsequent preferences according to lipid source, with a preference for lard at 9% (L), soybean oil at 3% (S), and coconut oil at 6% (C) inclusion rate. Following abrupt weaning, whilst after 4 weeks those fed 9C had the heaviest body weights. Piglets fed a fixed 1:1 blend of 9C+9S had a poorer feed conversion ratio than those fed a blend of 9C+9L. The 9C and 9L combination groups showed better performance in both fixed blend and free choice feeding regimes. A feeding regime offering free choice combination of lipids might give the possibility for piglets to cope better with the transition at weaning.

2. Effects of intrauterine growth retardation and postnatal high-fat diet on hepatic inflammatory response in pigs.
Weaned piglets with IUGR or normal birthweight (NBW) (n = 20 each) received during the whole fattening period control diets (0% lard) or HF diets (HF, 10% lard). Compared with NBW pigs, IUGR pigs had lower daily gain and feed intake. Growth rate of pigs was increased by HF feeding. Pigs fed HF diets had lower peak concentrations of glucose and insulin, which decreased more slowly than in pigs that received the control diets. In summary, hepatic TLR4 signalling pathway and inflammatory response induced by HF feeding played an important role in the aggravated development of insulin resistance in pigs.

3. Fatty acid profile of the sow diet alters fat metabolism and fatty acid composition in weanling pigs.
Sows (n = 20) were fed with the experimental diets from day 35 of gestation and during lactation. When lard (L) was included in the sows' diet, increased concentrations of C18:1n-9 were found, whereas C18:2n-6 decreased in both colostrum and milk (P<0.01). Milk from sows fed L showed higher C16:0 and C18:1n-7 concentration in colostrum than those that were fed sunflower oil (SFO). On the first week after weaning, time effect was observed on intramuscular fat content in the pigs. The administration of polyunsaturated FA to gestating and lactating sows increased FA beta-oxidation in pigs after weaning which could help the mobilization of body reserves in this critical period.

4. The effects of diets enriched in omega-3 fatty acids on carcass characteristics and the fatty acid profile of intramuscular and subcutaneous fat in pigs.

The objective of this study was to determine the effect of the concentration of C18:3 n-3 and the total concentration of polyunsaturated fatty acids (PUFA) and n-3 PUFA in the diet on the performance of pigs, carcass characteristics, and fatty acid profile of intramuscular fat. Twenty-four crossbred pigs male Duroc x female(Polish Large White x Danish Landrace) were divided into 3 groups (A, B, and C) and from 60 to 105 kg body weight (BW). Diet A contained 1% rapeseed oil, 2% fish oil, and 0.5% lard; diet B contained 2.5% rapeseed oil and 1% linseed oil; and diet C contained 2.5% linseed oil and 1% fish oil. Fat mixtures in the diet did not influence growth, carcass performance, lipid or fatty acid concentrations in the tissues of the pigs, but changed their PUFA concentration. Supplementation of the diet for pigs with a mixture of linseed oil and fish oil makes it possible to obtain good quality pork with health-promoting properties.

References

FEDNA: http://www.fundacionfedna.org/
FND. CVB Feed Table 2016. http://www.cvbdiervoeding.nl
INRA. Sauvant D, Perez, J, y Tran G, 2004, Tables de composition et de valeur nutritive des matières premières destinées aux animaux d'élevage.
NRC 1982. United States-Canadian Tables of Feed Composition: Nutritional Data for United States and Canadian Feeds, Third Revision.
Rostagno, H,S, 2017, Tablas Brasileñas para aves y cerdos, Composición de Alimentos y Requerimientos Nutricionales, 4° Ed.