Influence of method of surfactant supplementation on characteristics of digestion and feeding value of fat in Holstein steers fed a high-energy finishing diet

Abstract

Four Holstein steers (271 ± 11 kg) with cannulae in the rumen and proximal duodenum were used to study the influence of method of surfactant (Tween 80) supplementation on characteristics of digestion and feeding value of fat. Treatments consisted of a steam-flaked corn-based finishing diet supplemented with: (1) no supplemental fat, no surfactant; (2) 6% supplemental fat (yellow grease, no surfactant; (3) 5.75% supplemental fat plus 0.25% Tween 80 (TW) added to the diet as part of the premix (TW was mixed with premix before incorporation with grain in the mixer, as second step in diet preparation) and (4) 5.75% supplemental fat plus 0.25% TW combined directly with the supplemental fat (TW was mixed with supplemental fat before incorporation into the feed mix as penultimate step in diet preparation). There was no surfactant by supplemental fat interactions (p > 0.05). Surfactant did not affect (p > 0.05) site and extent of organic matter (OM), starch, N, acid detergent fiber (ADF) and fatty acid (FA) digestion, or digestible energy (DE) value of diet. Supplemental fat decreased (p < 0.05) ruminal and total tract digestion of OM and ADF and increased (p <0.05) the DE value of diet. The decrease in postruminal FA digestion was mainly due to decreased (p <0.05) digestion of C18:0. Digestible energy of supplemental fat averaged 6.87 Mcal/kg. It is concluded, that independent of method of addition, supplementing high-fat diets with 0.22% of Tween 80 does not influence site and extent of digestion or the feeding value of supplemental fat.

Keywords:

• digestion
• fat
• ruminants
• surfactants
• Tween 80

Introduction

Current standards (NRC 1996) for the net energy of maintenance (NE_m) and gain (NE_g) values of supplemental fats are 6.00 and 4.50 Mcal/kg. Estimates based on these values are consistent with empirically derived measures when total fatty acid (FA) intake did not exceed 0.86 g/kg of body weight (BW) (Plascencia et al. 2003). When FA intake exceeds 0.86 g/kg of BW, the NE value of fat declines (Zinn and Plascencia 2007). This decline is attributable to decreased postruminal FA digestion of saturated fatty acids (mainly stearic and palmitic acids; Plascencia et al. 2003). Plascencia et al. (2004) observed that with increasing level of fat supplementation, the bile:lipid ratio or emulsification capacity of intestinal chyme decreases.

Polyoxyethylene sorbitan monooleate (Tween 80; TW), a non-ionic surfactant, has an hydrophile-lipophile balance (HLB) value of 15, almost 2-fold HLB value than natural soy lecithin (∼8, McClements 2004). Compounds with HLB values >12, act as ‘oil-in water-emulsifier’. Thus, TW may have potential as feed additive in ruminant diets to promote intestinal FA absorption. To our knowledge, the use of TW as feed additive or their effects on digestive function and feed value of fats in ruminants have not been previously examined. The objective of this experiment was to evaluate the influence of method of TW addition in fat-supplemented high-energy diets on digestion and feed value of supplemental fat in cannulated Holstein steers.

Materials and methods

Four Holstein steers (271±11 kg) with cannulae in the rumen and proximal duodenum were used to study the influence of method of surfactant (Tween 80) supplementation on characteristics of digestion and feeding value of supplemental fat. Treatments consisted of a steam-flaked corn-based finishing diet (77.9% of corn) supplemented with: (1) no supplemental fat, no surfactant; (2) 6% supplemental fat (yellow grease, no surfactant; (3) 5.75% supplemental fat plus 0.25% Tween 80 (TW; IFN 8-08-031) added to the diet as part of the premix [TW was mixed with premix before incorporation with grain in the mixer (Leon Weill mixer, model 30910-7, Coyoacán, Mexico), as second step in diet preparation] and (4) 5.75% supplemental fat plus 0.25% TW combined directly with the supplemental fat (TW was mixed with supplemental fat before incorporation into the feed mix as penultimate step in diet preparation). Dry matter intake was restricted to 2% of BW. Composition of supplemental yellow grease was similar to that used in previous studies (Plascencia et al. 2003, 2004). Facilities and protocols for steers feeding, sampling procedures, laboratory analyses and calculations were identically for those that were described previously by Plascencia et al. (2008). The trial data were analysed using a general linear model procedure (SAS Inst. Inc., Cary, NC) based in a model for 4×4 Latin square experimental design. Treatments effects were tested using orthogonal contrast as follows: (1) T1 vs. T2, T3 and T4; (2) T2 vs. T3 and T4 and (3) T3 vs. T4. Treatment differences were considered to be significant when p ≤ 0.05.

Result and discussion

There were no treatment interactions (p >0.05), nor did supplemental TW affect (p >0.05) on site and extent of OM, starch, N, ADF and FA digestion, or DE value of diet (Table 1).

Table 1. Influence of surfactant Tween 80 method addition in fat-supplemented diet on characteristics of digestion in cannulated Holstein steers.

		6% supplemental fat^a
	No fat	No TW	TW-premix	TW-fat	SEM
Intake, g/d
DM	5406	5458	5470	5479
OM	5115	5180	5183	5199
Starch	2575	2394	2413	2400
ADF	374	357	371	366
N	104	101	103	101
Gross energy, Mcal/d	23.59	25.82	25.83	25.97
Ruminal digestion,% intake
OM^b	60.7	55.4	57.6	58.6	1.5
Starch	85.3	85.5	84.4	85.6	1.1
ADF^b	32.83	20.44	20.36	21.99	2.2
Feed N	55.57	54.27	55.01	56.02	1.4
Microbial efficiency^c	22.25	20.92	21.55	21.59	1.4
N efficiency^d	1.00	1.06	1.03	1.02	0.02
Postruminal digestion,% leaving abomasums
OM	63.00	61.39	60.24	60.80	1.08
Starch	94.25	92.52	93.90	94.65	1.8
ADF	10.62	9.91	11.17	8.20	1.2
N	67.68	68.43	69.30	69.12	2.3
Total tract digestion,% intake
OM^b	81.27	78.35	78.61	79.31	0.3
Starch	99.24	98.78	99.01	99.30	0.2
ADF^b	39.75	30.88	29.41	28.47	1.9
N	66.65	65.19	67.25	67.15	1.9
DE, Mcal/kg^b	3.49	3.648	3.65	3.66	0.01
Observed fat DE, Mcal/kg		6.73	6.82	6.93	0.23
^aNo TW=6% supplemental fat in diet without TW; TW-premix=5.75% supplemental fat plus 0.25% TW in diet, TW was mixed first with premix and added to the mixer as second step in diet preparation, and TW-fat=5.75% supplemental fat plus 0.25% TW in diet, TW was mixed first with fat and added to the mixer as penultimate step in diet preparation.
^bNo fat vs. supplemental fat effect (p<0.05).
^cDuodenal microbial N, g kg^-1 OM fermented in the rumen.
^dDuodenal non-ammonia N, g·g^-1 N intake.

Fat supplementation decreased (p<0.05) ruminal and total tract digestion of OM (5.8% and 3.1%) and ADF (36.2% and 25.6%), and increased (p<0.01, 4.5%) the DE value of diet. Decreased on ruminal OM digestion has been a consistent response to higher levels of fat supplementation (Zinn and Shen 1996). This effect is due to decreased ruminal fibre digestion, and the ruminal ‘indigestibility’ of fat itself (Zinn et al. 2000; Plascencia et al. 2003).

Given that DE value of SF corn is 4.10 Mcal/kg (NRC 1996), the replacement DE value of supplemental fat can be estimated as follows:

Fat DE, Mcal/kg =(ED supplemented diet – ED unsupplemented diet/0.060)+4.1.

The constant (0.060) represents the average of amount of fat plus TW that replaced steam-flaked corn in the fat-supplemented diets. Assuming the DE of TW is 0%, then the DE value of yellow grease is 7.1 Mcal/kg (6.81/0.958). This value represents 97% of the tabular value for supplemental fat (NRC 1996). The lower DE value for supplemental fat is attributable to decreased postruminal FA digestion observed at higher levels of total fat intake (Plascencia et al. 2003; Zinn and Plascencia 2007).

Treatments effects on postruminal FA digestion are shown in Table 2. Basis for the lack of surfactant effects on FA digestion is not certain. We had hypothesised that whereas the bile:lipid ratio of intestinal chyme decreases as level of fat supplementation increases (Plascencia et al. 2004), supplementation of high-fat diets with an emulsifier would promote intestinal fat digestion. The critical micelle concentration value for TW is from 0.01 to 0.016 (Bendikiene et al. 2008). Thus, whereas the dosage used for T4 (TW on fat) in the present experiment was 0.043 ml of TW/g of supplemental fat, doses of TW as low as 0.01 ml/l are expected to have appreciable emulsification potential (Jiao and Burgess 2003). Furthermore, Kan et al. (1999) observed a synergistic effect of phosphatidylcholine (main component of bile salts) and TW. However, Simões et al. (2005) determined in vitro that TW, depending on amphipath (amphiphile) concentrations, requires considerable time (up to several hours) to disintegrated lipid membranes.

Table 2. Influence of surfactant Tween 80 method addition in fat-supplemented diet on FA digestion in cannulated Holstein steers.

		6% supplemental fat^a
	No fat	No TW	TW-premix	TW-fat	SEM
Intake, g/d
C16:0	39.9	151.9	144.0	142.8	1.3
C18:0	5.7	48.6	46.9	45.9	0.5
C18:1	44.6	193.5	196.4	193.0	1.9
C18:2	34.2	43.1	52.7	55.3	0.3
Total	124.4	437.1	439.9	436.9	3.8
Total FA intake g/kg BW	0.46	1.61	1.62	1.61	–
Flow to duodenum, g/d
C16:0^b	25.0	79.1	82.4	81.0	1.9
C18:0^b	71.9	278.5	293.3	279.1	13.8
C18:1^b	36.4	81.9	68.2	73.7	9.2
C18:2	6.1	9.6	8.7	9.2	1.1
Total^b	139.4	449.1	452.6	443.0	13.9
Fecal excretion g/d
C16:0^b	3.7	13.5	14.6	12.1	0.9
C18:0^b	11.5	82.6	85.6	68.8	6.7
C18:1^b	3.6	8.8	9.1	8.3	0.5
C18:2^b	1.3	2.9	2.1	1.7	0.1
Total^b	20.0	106.8	111.4	90.9	7.8
Postruminal digestion,%
C16:0	85.4	82.9	82.5	85.2	0.9
C18:0^b	85.3	70.4	71.5	75.5	1.4
C18:1	89.5	88.0	86.6	88.6	1.6
C18:2	78.6	78.6	76.0	80.6	4.3
Total^b	86.3	76.1	75.9	78.6	1.1
^aNo TW=6% supplemental fat in diet without TW; TW-premix=5.75% supplemental fat plus 0.25% TW in diet, TW was mixed first with premix and added to the mixer as second step in diet preparation, and TW-fat=5.75% supplemental fat plus 0.25% TW in diet, TW was mixed first with fat and added to the mixer as penultimate step in diet preparation.
^bNo fat vs. supplemental fat effect (p<0.05).

Consisted with previous reports (Plascencia et al. 2003; Kucuk et al. 2004), supplemental fat decreased postruminal FA digestion (Table 2), mainly due to decreased digestion of C18:0. Across of fat-supplemental diets, the decline in postruminal digestion was 6.9-fold greater for C18:0 than for C16:0; consistent with the concept that intestinal digestion of saturated fatty acids decreases with increasing chain length (Zinn 1989). Furthermore, whereas C18:0 comprised only 10.8% of FA intake, it comprised 63.3% of total FA flow to the small intestine. Hence, decreased digestion of C18:0 explains most of the depression in total intestinal FA digestion due to fat supplementation (Zinn and Plascencia 2007).

Across fat-supplemented diets treatments, postruminal FA digestion averaged 76.8%, slightly (4%) greater than predicted (73.8%) based on level of fat intake (FA digestion,%=87.56 – 8.591FAI; Plascencia et al. 2003). Given that one gram of intestinally digestible fat (IDF) has a metabolizable energy (ME) value of 9 Kcal (100% of its physiological fuel value); and the partial efficiency of utilisation of metabolizable energy (ME) from dietary fat for BW gain is 67% (Plascencia et al. 2003), the NE_g value of dietary fat was 6.03 Kcal/g IDF. Applying the observed digestibility value (76.8), the NE_g value for the yellow grease used in this study is 4.63. Corresponding NE_m value is 5.74 Mcal/kg [where NE_m=(NE_g+0.41)/0.877; derived from NRC 1984], this energy value represents 95% of the tabular value of NRC (1996).

It is concluded, that independent of method of addition, supplementation of a high-fat finishing diet with 0.22% Tween 80 does not enhance diet digestion or the feeding value of supplemental fat.

Acknowledgements

Authors are thankful to the Consejo Nacional de Ciencia y Tecnología de México (CONACYT) for financial support. Fondo Ciencia Básica, Project No. 50344-Z.

Additional information

Notes on contributors

H. Dávila-Ramos

†Scholarships of the Consejo Nacional de Ciencia y Tecnología México

A. González-Castellón

†Scholarships of the Consejo Nacional de Ciencia y Tecnología México

S.H. Vega

†Scholarships of the Consejo Nacional de Ciencia y Tecnología México