Effects of soybean oil supplement to diets of lactating dairy cows, on productive performance, and milk fat acids profile: a meta-analysis

Figures & data

Table 1. Summary of papers used for meta-analysis.

Author	NC^a	Breed	Dose (g/kg)	Parameters
Abel-caines et al. 1998	1	Holstein	22.5	DMI, MY, MFP , MFY, MPP, MPY, MLP, MLY, C4, C6, C8, C10, C12, C14, C16, C18, C18:1 trans11, C18:2, C18:3
AlZahal et al. 2008	2	Holstein	17,34	DMI, MY, MFP , MFY, MPP, MPY, C6, C8, C10, C12, C14, C15, C16, C17, C18, C20, C18:2, C18:3
Barletta et al. 2016	1	Holstein	30	DMI, MY, MFP , MFY, MPP, MPY, MLP, MLY, C4, C6, C8, C10, C12, C14, C15, C16, C17, C18, C20, C18:1 cis9, C18:1 trans11, C18:2, C18:33, cis9 trans11 CLA
Bu et al. 2007	1	Holstein	40	DMI, MY, MFP, MFY, MPP, MPY, MLP, C8, C10, C12, C14, C16, C18, C18:1 cis9, C18:1 trans11, C18:2, C18:33, cis9 trans11 CLA, trans 10 cis12 CLA
Dhiman et al. 2000 Exp1	1	Holstein	36	DMI, MY, MFP, MFY, MPY, MLP
Dhiman et al. 2000 Exp2	4	Holstein	5, 10, 20, 40	DMI, MY, MFP, MFY, MPP, MPY, MLP, C16, C18, C18:2, C18:3
Fatahnia et al. 2008	1	Holstein	30	DMI, MY, MFP, MFY, MPP, MPY, MLP, MLY, C10, C12, C14, C15, C16, C17, C18, C20, C18:1 cis9, C18:1 trans11, C18:2, C18:3, trans 10 cis12 CLA
Huang et al. 2008	1	Holstein	50	DMI, MY, MFP, MFY, MPP, MPY, MLP, MLY, C4, C6, C8, C10, C12, C14, C15, C16, C17, C18, C20, C18:2, C18:3
Jenkins et al. 1996	1	Holstein	35	DMI, MY, MFP, MFY, MPP, MPY, C4, C6, C8, C10, C12, C14, C16, C18, C18:2
Loor et al. 2002	1	Jersey	35	DMI
Vargas-Bello-Pérez et al. 2015	1	Holstein	26	C4, C6, C8, C10, C12, C14, C15, C16, C17, C18, C20, C18:1 cis9, C18:1 trans11, C18:2, C18:3, cis9 trans11 CLA
Ye et al. 2009	1	Holstein	20	DMI, MY, MFP, MPP, MLP, C8, C10, C12, C14, C15, C16, C18, C20, C18:2, C18:33, cis9 trans11 CLA, trans 10 cis12 CLA
Zheng et al. 2005	1	Holstein	20	DMI, MY, MFP, MFY, MPP, MPY, MLP, MLY, C14, C16, C18, C18:1 cis9, C18:1 trans11, C18:23, cis9 trans11 CLA, trans 10 cis12 CLA

DMI: Dry Matter Intake; MY: Milk Yield; MFP: Milk Fat Percentage; MFY: Milk Fat Yield; MPP: Milk Protein Percentage; MPY: Milk Protein Yield; MLP: Milk Lactose Percentage; MLY: Milk Lactose Yield; CLA: Conjugated Linoleic Acid.

^a No. of comparisons.

Figure 1. Forest plot of the influence of soybean oil on milk production of dairy cows based on Standardised Mean Differences (SMD). The mean effect size, calculated according to a random effects model, is indicated by the diamond at the bottom. The size of the squares illustrates the weight of each study relative to the mean effect size. Smaller squares represent less weight.

Figure 2. Funnel plot for analysing publication bias of milk production. Empty circles indicate observed values.

Table 2. Effect size and heterogeneity for the effect of soybean oil on dry matter intake, milk production and milk composition in dairy cows.

Outcome^a	NC^b	SMD^c	95% confidence intervals	p- value	DM^d	95% confidence intervals	Q	p- value	I^2
DMI	16	−0.305	−0.544, −0.065	.013	−0.269	−0.542, 0.005	9.297	.861	0
MY	15	0.362	0.111, 0.612	.005	0.634	−0.072, 1.339	14.393	.421	2.734
MFP	15	−1.015	−1.483, −0.547	<.001	−0.376	−0.500, −0.253	40.279	<.001	65.242
MFY	14	−0.565	−1.000, −0.129	.011	−0.091	−0.149, −0.033	32.349	.002	59.814
MPP	14	−0.369	−0.767, 0.029	.069	−0.075	−0.122, −0.029	28.334	.008	54.118
MPY	14	0.058	−0.205, 0.322	.665	−0.002	−0.024, 0.021	13.535	.407	3.953
MLP	11	−0.038	−0.324, 0.248	.794	−0.009	−0.063, 0.046	4.407	.927	0
MLY	5	−0.018	−0.426, 0.391	.933	−0.019	−0.063, 0.025	3.536	.472	0

^a DMI: Dry Matter Intake; MY: Milk Yield; MFP: Milk Fat Percentage; MFY: Milk Fat Yield; MPP: Milk Protein Percentage; MPY: Milk Protein Yield; MLP: Milk Lactose Percentage; MLY: Milk Lactose Yield.

^b NC: No. of comparisons.

^c SMD: Standardised Mean Difference.

^d DM: Difference in Means.

Figure 3. Forest plot of the influence of soybean oil on milk fat percentage in milk of dairy cows based on Standardised Mean Differences (SMD). The mean effect size, calculated according to a random effects model, is indicated by the diamond at the bottom. The size of the squares illustrates the weight of each study relative to the mean effect size. Smaller squares represent less weight.

Figure 4. Funnel plot for analysing publication bias of milk fat percentage. Empty circles indicate observed values.

Table 4. Summary of meta-regression analysis.

Outcomes^a	Covariate^b	Slope	p- value	Intercept	p- value
MFP	Dose	−0.050	.003	0.347	.480
	DTFA	−0.041	.024	−0.003	.994
	D18:2	−0.084	.011	0.015	.972
	DNDF	0.061	.027	−0.750	.001
MFY	Dose	−0.037	.037	0.448	.391
	DTFA	−0.028	.126	0.117	.813
	D18:2	−0.066	.047	0.249	.585
	DNDF	0.063	.031	−0.263	.274
MPP	Dose	−0.002	.872	−0.302	.551
	DTFA	0.003	.825	−0.463	.307
	D18:2	0.014	.652	−0.544	.206
C10	Dose	−0.108	.006	1.480	.218
	DTFA	−0.060	.120	−0.140	.895
	D18:2	−0.150	.028	−0.179	.846
C12	Dose	−0.113	.034	1.330	.413
	DTFA	−0.100	.020	0.625	.598
	D18:2	−0.272	.0001	1.399	.130
C14	Dose	−0.113	.006	0.829	.490
	DTFA	−0.082	.034	−0.298	.775
	D18:2	−0.206	.001	0.134	.872
C16	Dose	−0.071	.007	−0.295	.683
	DTFA	−0.071	.007	−0.488	.465
	D18:2	−0.158	.0008	−0.306	.602
C18	Dose	0.034	.147	0.380	.572
	DTFA	0.027	.244	0.635	.302
	D18:2	0.078	.072	0.347	.545
C18:2	Dose	0.053	.046	−0.541	.476
	DTFA	0.034	.225	0.040	.956
	D18:2	0.071	.177	0.012	.986

^a MFP: Milk Fat Percentage; MFY: Milk Fat Yield; MPP: Milk Protein Percentage.

^b Dose: Dose of Soybean oil; DTFA: Difference of Total Fatty Acids in treatment and control diets; D18:2: Difference of C18:2 in treatment and control diets; DNDF: Difference of Neutral Detergent Fibre in treatment and control diets.

Figure 5. Forest plot of the influence of soybean oil on C18:2 in milk of dairy cows based on Standardised Mean Differences (SMD). The mean effect size, calculated according to a random effects model, is indicated by the diamond at the bottom. The size of the squares illustrates the weight of each study relative to the mean effect size. Smaller squares represent less weight.

Figure 6. Funnel plot for analysing publication bias of C18:2 in milk. Empty circles indicate observed values and solid dots are the potentially missing studies.

Table 3. Effect size and heterogeneity for the effect of soybean oil on milk fatty acid profiles in dairy cows.

Outcome	NC^a	SMD^b	95% confidence intervals	p- value	DM^c	95% confidence intervals	Q	p- value	I^2
C4	5	−0.913	−1.896, 0.071	.069	−0.294	−0.593, 0.006	17.805	.001	77.534
C6	7	−1.597	−2.387, 0.806	<.001	−0.469	−0.675, −0.263	23.528	.001	74.499
C8	9	−1.228	−1.934, −0.522	.001	−0.358	−0.489, −0.227	36.199	.001	77.900
C10	10	−1.647	−2.410, −0.938	<.001	−0.957	−1.201, −0.713	41.015	<.001	78.057
C12	10	−1.941	−2.816, −1.066	<.001	−0.984	−1.385, −0.584	53.593	<.001	83.207
C14	11	−2.352	−3.114, −1.591	<.001	−2.771	−3.382, −2.160	45.691	<.001	78.114
C15	7	−1.353	−1.950, −0.757	<.001	−0.203	−0.294, −0.112	12.088	.060	50.363
C16	15	−2.128	−2.737, −1.519	<.001	−5.467	−6.830, −4.103	53.380	<.001	73.773
C17	5	−0.784	−2.322, 0.753	.317	−0.021	−0.095, 0.053	37.275	<.001	89.269
C18	15	1.271	0.732, 1.810	<.001	2.050	0.990, 3.110	51.635	<.001	72.887
C20	7	0.049	−0.490, 0.588	.859	0.003	−0.020, 0.027	12.184	.058	50.755
C18:1 Cis9	5	0.951	−0.053, 1.955	.063	2.058	0.012, 4.104	16.321	.003	75.491
C18:1 Trans11	5	2.606	1.118, 4.094	.001	2.435	1.145, 3.725	26.788	<.001	85.068
18:2	15	0.854	0.234, 1.475	.007	0.405	0.133, 0.678	73.794	<.001	81.028
18:3	13	0.147	−0.196, 0.491	.401	0.008	−0.014, 0.030	18.887	.091	36.464
Cis9 Trans 11 CLA	5	1.877	0.322, 3.432	.018	0.788	0.173, 1.404	35.879	<.001	88.851
Trans 10 Cis12 CLA	4	0.470	0.017, 0.923	.042	0.018	−0.006, 0.041	1.986	.575	0

CLA: Conjugated Linoleic Acid.

^a NC: No. of comparisons.

^b SMD: Standardised Mean Difference.

^c DM: Difference in Means.

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