Effect of Dietary Source of Omega-3 Fatty Acids on Milk Production, Fatty Acid Profiles and IGF-1 of Lactating Dairy Cows in Arid Subtropics

Abd El-Nasser Ahmed Mohammed1, Tarek Al-Shaheen1, Mohammed Al-Saiady2 and Ahmed El-Waziry3

1Department of Animal and Fish Production, College of Agricultural and Food Sciences, King Faisal University, P.O. Box 420, Al-Hassa 31982, Kingdom of Saudi Arabia

2ARASCO Research and Development Department, P.O. Box 53845, Riyadh 11593, Kingdom of Saudi Arabia

3Department of Animal and Fish Production, Faculty of Agriculture, El-Shatby, Alexandria University, P.O. Box 21454, Egypt.

ABSTRACT

Dietary omega-3 fatty acids are a type of polyunsaturated fat known to improve production and body health in animals and human as well. The current on-farm trial was to evaluate the effects of omega-3 fatty acids inclusion in the diets on milk production and fatty acid profiles and insulin growth factors-1 values in lactating dairy cattle. Three hundred Holstein lactating cows in a commercial farm were assorted to a control group fed basal control diet and two treated groups fed diets containing extruded flaxseed (7.0%) and salmate (25 g/head/day). The basal control, extruded flaxseed and salmate diets were formulated to be isonitrogenous and isoenergetic diets. The diets were given to each group from three weeks pre-parturition to week 23 of lactation. Feed intake, milk production and composition and fatty acid profiles were recorded during the study. Fat and energy corrected milk were calculated. Feed intake did not differ among groups. Flaxseed significantly (P<0.05) increased milk yield, fat corrected milk and energy corrected milk if compared to other groups. Milk fat (%) decreased significantly (P˂0.05), while saturated short-chain (C12:C15) and long-chain (C17:C20) fatty acids were higher (P˂0.05) in Salmate and extruded flaxseed groups. Moreover, the ratio of omega-6/omega-3 was the lowest in flaxseed group (3.76) compared to control (8.06) and salmate (8.31) groups. In conclusion, flaxseed diet improved (P < 0.05) milk production efficiency (kg milk/kg feed) and fatty acid profile compared to salmate and control diets.

Article Information

Received 10 December 2023

Revised 05 February 2024

Accepted 13 February 2024

Available online 16 May 2024

(early access)

Published 01 August 2024

Authors’ Contribution

MA designed the study. TA carried out the study and collected the data. AE statistically analyzed the results. AA wrote the manuscript. All authors interpreted the data, revised the manuscript, and approved the final version.

Key words

Flaxseed, Salmate, Milk, Fat, Fatty acids, IGF-1

DOI: https://dx.doi.org/10.17582/journal.pjz/20231210172024

* Corresponding author: aamohammed@kfu.edu.sa

0030-9923/2024/0005-2319 $ 9.00/0

Copyright 2024 by the authors. Licensee Zoological Society of Pakistan.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

INTRODUCTION

Dietary supplements to ruminant animals affect both productive and reproductive performances (Mohammed and Al-Suwaiegh, 2023). The global demand for an adequate meat and milk is predicted to increase by 35.0% by 2030 due to increase demand. Saudi Arabia, as a result, has encouraged the development in meat and milk production to overcome the increasing demand (Al-Suwaiegh et al., 2022). Therefore, several strategies have been explored a worldwide including dietary supplements that can improve meat and milk production.

Mammalian species can synthesize fatty acids except omega-3 and omega-6 families, which need to be given in the diet. Omega-3 fatty acids are a type of polyunsaturated fat (PUFs) found in fish oil. Supplementation of essential PUFs to ruminant animals are faced with lipolysis and bio-hydrogenation in the rumen and little are available for absorption in addition to their toxic effect on rumen microbes. Therefore, fat manipulation is required to ensure reaching unsaturated FAs to small intestine for absorption. This can be achieved through feed ingredients, changing the environment of rumen, shifting rumen bypass (Ibrahim and Hassen, 2023; Wei et al., 2023).

Omega-3 fatty acids particularly obtained from flaxseed and fish oil are found essential for animals and human health (Karageorgou et al., 2023; Elbarbary et al., 2023; Dere-Yelken et al., 2024). Some studies have been explored the effects of omega-3 fatty acids on milk production and composition. The results might be variable due to experimental conditions, animal species, the doses and flaxseed processing (Leduc et al., 2017; Meignan et al., 2017). Studies of omega-3 fatty acids on milk production and composition have shown no significant changes, while others reported slight increases or decreases depending on the type and amount of omega-3 fatty acids supplemented (Moallem et al., 2020; Beauregard et al., 2023). Flaxseed supplementation, particularly to high-yielding cows, has shown some potential to increase milk production. In addition, fish oil supplementation may have a a variable effect depending on the dose, where moderate doses may slightly increase milk production, while higher doses may suppress it due to it is potential negative effect on rumen function (Swanepoel and Robinson, 2020; Ferlay and Chilliard, 2020).

Fat content and fatty acid profiles of milk are highly correlated with quality, processing ability, sensory properties and body health. Regarding to effects of omega-3 fatty acids on milk composition, it has been found that omega-3 supplementation significantly altered the fatty acid profile of milk, increasing the proportion of omega-3 fatty acids and decreasing the ratio of omega-6 to omega-3 fatty acids (Petit, 2003; Ruiz-González et al., 2022). This shift in fatty acid profile can potentially improve the nutritional value of milk. Other milk components including lactose and minerals are generally not affected by omega-3 supplementation. Additionally, due to the direct and indirect roles of IGF-1 on milk production including mammary gland development, milk synthesis, nutrient uptake, hormonal regulation and energy balance (Meyer et al., 2017), the changes of IGF-1 were explored during the study. Therefore, this study was designed to investigate sources of omega-3 fatty acids including extruded flaxseed and salmate, on IGF-1, efficiency of milk production and fatty acid profile of lactating dairy cattle in arid subtropics.

MATERIALS AND METHODS

Animals management and diets

The current study was carried out in a dairy farm located in Riyadh of KSA from June to December 2023. Three hundred lactating Holstein cows were used for the study. The cows had 582±21 kg of body weight and 3.35±0.10 of body condition score.

The average ambient temperature ranged between 31 to 48 degrees Celsius and relative humidity ranged between 8 to 94 in Riyadh region of KSA. It is important to indicate that all cows were kept under evaporative cooling system, which works during stressful condition. The evaporative cooling system in the dairy farm starts to work automatically when the temperature inside the barns reaches 21°C. The fans will start first then cooling system by water spray when the temperature increases to 23 °C. Consequently, the average temperature was recorded as 25°C to 28°C by using that system. Animals were placed in an open lot and were divided equally into three groups based on previous average milk yield and parity: Second lactation (L2= 37 cows), third lactation (L3= 35 cows), fourth lactation (L4=16 cows), fifth lactation (L5=12 cows), and the average milk yield includes control (32.27kg), dry protected fish oil (Salmate) (33.70kg) and Flaxseed/linseed (28.99kg). The cows were randomly distributed through complete randomized design for investigating the effects of extruded flaxseed (7.0%) and salmate (25g/head/day) compared to basal control diet. The period of experiment lasted approximately six months. The control, extruded flaxseed and salmate diets were formulated to provide the nutrient requirement of lactating dairy cows according to body weight (580.0 kg) and body gain (0.2 kg day-1), milk production (17 kg day-1) and milk fat (3.5%) as recommended by NRC (2001). The cows were given ad libitum mineral mixture and fresh water. The rations of extruded flaxseed and salmate were prepared weekly to avoid lipid peroxidation. Sufficient amount of control, extruded flaxseed and salmate rations was offered to the lactating cows as a total mixed ration to allow for a 10.0% ort. Feed intake was recorded as the difference between the daily quantity of ration that was offered and its respective ort.

Extruded flaxseed and salmate supplements

Extruded flaxseed ingredient includes 85 g/kg flaxseed and 15 g/kg wheat bran obtained from ARASCO (ARASCO R and D Guidelines, Riyadh, KSA). The Chemical composition of extruded flaxseed is 44.0 fat, 28.0% fiber, ٢1.0% protein, 4% ash, 6% carbohydrates. The extruded flaxseed fat contains 47.0% omega-3 fatty acid (α -linolenic fatty acid, ALA C18:3 n-3), and 15.0 % omega-6 fatty acid (mostly linoleic acid, LA 18:2 n-6). Salmate is dried fish oil and natural protected source of polyunsaturated fatty acid. The salmate contains about 31.0% omega- 3 and 5.0% Omega-6 fatty acids.

Meteorological condition

In the commercial dairy farm, there is a monitoring station for recording the temperatures and humidity daily during the entire experimental period. Temperature-humidity index (THI) was calculated to quantify the degree of heat stress on cows using the following formula (West, 2003), THI = td - (0.5 x RH) (td - 58), where td is the dry bulb temperature in ˚F, and RH is the relative humidity as a fraction of the unit (Fig. 1).

 

Body condition score

Body condition score (BCS) using a five-point scale (where1 = emaciated and 5 = fat according to Wildman et al. (1982) were recorded at the beginning of the trial, after two months and at the end of the trial.

Milk sample collection and chemical analysis

Milk production and other information of control, extruded flaxseed, salmate groups were recorded electronically in milking parlor during the experimental period. Milk samples (50.0 mL) were collected from the control and experimental groups and stored in tubes for further chemical analysis. Milk samples of control and experimental groups, extruded flaxseed and salmate were analyzed for determination of casein, fat, protein, total solids (TS), solids non-fat (SNF), lactose, milk urea nitrogen. Fat corrected milk (3.5% fat) and energy corrected milk (3.5% fat and 3.2% protein) were calculated, respectively, according to formulas of Nordlund (1987) and Bernard (1997). Fatty acid contents were calculated as described by Glasser et al. (2007). In addition, the collected milk samples were stored (-20°C) without preservative to determine the FAs profiles using gas chromatography (Cruz-Hernandez et al., 2007).

Insulin-growth factor-1

Blood samples were collected biweekly and plasma samples were obtained and stored (-20°C). Insulin-growth factor-1(IGF-1) was determined by inhibition immunoassay technique (ELISA), using commercial kit (Ycusabio Company, Japan).

Statistical analysis

Data of feed intake, milk production, fatty acid profiles and IGF-1 values were statistically analyzed by generalized linear model procedure of SAS (2008) using the following model; Yijkl =μ+Ti+Eij; where Yij, the observation; Μ, the overall mean; Eij, standard error. Duncan’s Multiple Range Test (Duncans, 1955) was used to compare the means of the control and treated groups.

RESULTS

Feed intake (kg) and milk yield (kg/day)

Table I shows that dry matter intake increased (P > 0.05) in salmate groups when compared to the flaxseed and control groups during pre-partum period. During postpartum period, the dry matter intake showed a decreasing trend (P > 0.05) in salmate and extruded flaxseed groups when compared to the control group. Tables II presents the milk yield of lactating cows fed with the experimental diets (control, salmate and extruded flaxseed) over twenty-three weeks. Average milk yield was 46.87, 42.24 and 41.24 kg/d of extruded flaxseed, salmate and control groups, respectively. Extruded flaxseed and salmate diets increased milk yield by ١٣.٦٥%, and 2.4%, respectively, compared to control diet. Extruded flaxseed significantly (P<0.05) increased energy corrected milk. Fat corrected milk was not affected by feeding flaxseed compared to the control. Highest feed conversion ratio (1.78 kg milk/kg feed) was obtained in extruded flaxseed group followed by Salmate (1.58 kg milk/kg feed (and control diet (1.52 kg milk/kg feed. The difference in body condition score among groups was not significantly (P>0.05) differed.

 

Table I. Effect of salmate and extruded flaxseed diets on feed intake (dry matter basis) of lactating Holstein cows.

Fatty acids	Control	Treatments
		Salmate	Flaxseed
Prepartum, 21 days	11.24±0.81	13.23±0.81	11.95±0.81
Postpartum, 14 days	19.02±1.243	18.76±1.24	17.13±1.24
Postpartum,14 to 160 days	26.98±0.71	26.65±0.71	26.23±0.71

 

Control group fed basal diet. Extruded flaxseed group fed isoenergetic and isonitrogenous diet containing 7% extruded flaxseed. Salmate group fed isoenergetic and isonitrogenous diet containing 25 g/head/day of dried fish oil.

Saturated short-chain fatty acids

Table III shows saturated short-chain fatty acids of lactating Holstein cows. The value of C4:0 was significantly (P < 0.05) lower (0.64) in flaxseed group when compared to salmate (0.77) and control (0.74) groups. There was no significant difference in FAs values among all groups (C6:0 to C11:0). The value of C12:0 was significantly (P<0.05) higher in flaxseed group (2.62) compared to salmate (2.37) and control (2.33) groups. The values of C14:0 and C15:0 were significantly higher in flaxseed group compared to salmate and control treatments.

 

Table II. Effect of salmate and extruded flaxseed diets on milk production and efficiency of lactating Holstein cows.

Fatty acids	Control	Treatments
		Salmate	Flaxseed
Milk yield (kg/d)	41.24±0.26 c	42.24±0.26 b	46.87±0.26 a
Fat (%)	3.68±0.05 a	3.38±0.05 b	3.04±0.06 c
Fat corrected milk (kg/d)	42.72±0.51a	41.93±0.52b	43.77±0.55 a
Energy corrected milk (kg/d)	41.42±0.44 b	40.65±0.45 b	43.59±0.47 a
Production efficiency, (kg milk/kg feed)	1.52±0.81b	1.58±0.81b	1.78±0.81a
Body condition score	3.41±0.01	3.18±0.01	3.48±0.01

 

a, b, and c; values in the same row with different superscripts differ significantly (P < 0.05). For details of treatments, see Table I.

 

Table III. Effect of salmate and extruded flaxseed diets on saturated short-chain and long chain fatty acids of lactating Holstein cows.

Fatty acids	Control	Treatments
		Salmate	Flaxseed
Short chain fatty acid
C4:0	0.74±0.02a	0.77±0.02a	0.64±0.02b
C6:0	0.60±0.01	0.58±0.01	0.58±0.01
C8:0	0.57±0.009	0.57±0.009	0.59±0.01
C9:0	0.04±0.01	0.03±0.01	0.03±0.01
C10:0	1.63±0.14	1.88±0.14	1.84±0.16
C11:0	0.06±0.01	0.04±0.01	0.04±0.01
C12:0	2.33±0.03b	2.37±0.03b	2.62±0.04a
C13:0	0.09±0.003a	0.07±0.003b	0.09±0.004a
C14:0	9.38±0.10b	9.44±0.10b	10.45±0.11a
C15:0	0.88±0.01b	0.83±0.01c	0.94±0.01a
Long change fatty acid
C16:0	45.34±0.27a	46.03±0.28a	38.20±0.30b
C17:0	0.41±0.005b	0.39±0.005c	0.44±0.006a
C20:0	0.10±0.008b	0.09±0.008b	0.13±0.009a
C22:0	0.16±0.007	0.14±0.007	0.15±0.007
C23:0	0.13±0.009	0.12±0.01	0.13±0.01
C24:0	0.13±0.01	0.14±0.01	0.13±0.01

 

For details of treatments, see Table I.

 

Saturated long-chain fatty acids

The data of saturated long-chain fatty acids values is shown in Table III. The value of C16:0 was significantly higher in salmate (46.03) and control (45.34) groups compared to flaxseed group (38.20). The value of C17:0 was significantly higher (P<0.05) in flaxseed group (0.44) versus control (0.41) and Salmate (0.39) groups. The value of C20:0 was significantly higher (P<0.05) in flaxseed diet (0.13) compared to control (0.10) and salmate (0.09) groups. There was no significant difference in values of fatty acids (C22:0, C23:0 and C24:0) among all groups.

Monounsaturated fatty acids

The data of monounsaturated fatty acids values is shown in Table IV. The values of C10:1 and C20:1 was not differed among groups. The values of C14:1 was significantly (P<0.05) higher in the flaxseed group compared to salmate and control group. On the other hand, the value of C16:1 was significantly higher in salmate and control groups when compared to flaxseed group. The values of C18:1 and oleic acid was significantly higher in flaxseed group when compared to the salmate and control groups.

 

Table IV. Effect of salmate and extruded flaxseed diets on monounsaturated and polyunsaturated fatty acids of lactating Holstein cows.

Fatty acids	Control	Treatments
		Salmate	Flaxseed
Monounsaturated fatty acids
C10:1	0.10±0.007	0.11±0.007	0.11±0.007
C14:1	0.79±0.02b	0.78±0.02b	0.97±0.02a
C16:1	1.56±0.02a	1.57±0.02a	1.49±0.03b
C18:1	0.70±0.04c	0.82±0.04b	1.10±0.04a
C18:1 (Oleic)	20.19±0.20b	20.16±0.20b	22.75±0.22a
C20:1	0.35±0.04	0.32±0.04	0.43±0.04
Polyunsaturated fatty acids
C18:2 (Omega-6)	2.66±0.03b	2.66±0.03b	2.86±0.03a
C18:3 (Omega-3)	0.33±0.01b	0.32±0.01b	0.76±0.01a
C20:4	0.16±0.006	0.15±0.006	0.14±0.006
C20:5	0.12±0.009	0.12±0.009	0.12±0.009
C20:6	0.17±0.01b	0.19±0.01a	0.15±0.01c
Omega-6:Omega-3	8.06	8.31	3.76

 

For details of treatments, see Table I.

 

Polyunsaturated fatty acids

The data of polyunsaturated fatty acids values is shown in Table IV. The value of C18:2 (Omega-6) was significantly (P< 0.05) higher in flaxseed group compared to salmate and control groups. The same trend was found in value of C18:3 (Omega-3). More importantly, the omega-6/omega-3 ratio decreased by supplementation of flaxseed (3.76) compared to control (8.06) and salmate (8.31) groups.

Insulin growth factor-1

The data of insulin growth factor-1 (IGF-1) values is shown in Table V. The highest values of IGF-1 (P < 0.05) was found in flaxseed group followed by salmate and control groups, respectively. It seems that the values of IGF-1 in the groups follow the milk production curve in cattle, where the values of IGF-1increased till week 6 and decreased thereafter in all groups.

 

Table V. Effect of salmate and extruded flaxseed diets on insulin growth factors-1 of lactating Holstein cows.

Weeks	Insulin growth factor-1
	Control	Salmate	Flaxseed
Week 0	3.63 ± 0.06b	3.45 ± 0.09b	5.95 ± 0.24a
Week 2	4.45 ± 0.22b	4.08 ± 0.09b	6.53 ± 6.58a
Week 4	4.68 ± 0.14b	4.37 ± 0.07b	6.58 ± 0.11a
Week 6	4.42 ± 0.11c	5.15 ± 0.09b	7.36 ± 0.22a
Week 8	4.34 ± 0.06b	5.14 ± 0.09b	6.57 ± 0.16a
Week 10	4.23 ± 0.06b	4.82 ± 0.11b	6.19 ± 0.13a
Week 12	3.89 ± 0.09b	4.69 ± 0.11b	6.13 ± 0.16a
Week 14	3.87 ± 0.06b	4.68 ± 0.04b	5.85 ± 0.08a
Week 16	3.82 ± 0.08b	4.68 ± 0.03b	5.88 ± 0.16a
Week 18	3.61 ± 0.06c	4.58 ± 0.09b	5.74 ± 0.11a
Week 20	3.57 ± 0.07c	4.49 ± 0.07b	5.72 ± 9.04a
Week 22	2.99 ± 0.04c	4.48 ± 0.09b	5.50 ± 0.15a
Week 24	2.93 ± 0.06c	4.39 ± 0.09a	5.28 ± 0.09a
Week 26	2.81 ± 0.04b	4.11 ± 0.10b	4.43 ± 0.06a
Overall	3.85 ± 0.11b	3.84 ± 0.12b	5.88 ± 0.16a

 

For details of treatments, see Table I.

 

DISCUSSION

The effects of supplementation extruded flaxseed (7.0%) and salmate (25 g/head/day) to Frisian cows from three weeks pre-partum to 160 days postpartum on milk production and efficiency, fatty acid profiles and insulin growth factors-1 (IGF-1) is presented in Tables I-V. The results indicated that feed intake was none significantly (P > 0.05) decreased in salmate and extruded flaxseed groups. Values of milk yield (kg), fat (%), fatty acid profiles and IGF-1 were improved upon feeding extruded flaxseed diet.

Omega-3 and omega-6 families should be supplied in the diets because mammalian species cannot synthesize them. Furthermore, the problem with supplementation of essential fatty acids (FAs) to ruminant animals is occurrence of lipolysis and bio-hydrogenation of FAs in the rumen. Very little unsaturated FAs are available for absorption and the toxic effect of unsaturated FAs to rumen microbes is indicated (Vargas et al., 2020). Therefore, pathway of rumen bio-hydrogenation requires fat manipulation to ensure reaching dietary unsaturated FAs to small intestine in the form of conjugated linoleic acid (CLA). Several studies were previously evaluated the effects of fat supplementation on milk production and composition (Sadeghi et al., 2019; Al-Mufarji et al., 2023). However, caution is taken of dietary fat supplementation because of the significant decreases of feed intake (Maigaard et al., 2023).

The feed intake (P > 0.05) in salmate and extruded flaxseed groups were slightly decrease during postpartum period compared to control one, which might be attributed to generation of feedback satiety signals that prevent further feed intake over feeding large amounts of fats (Palmquist and Jenkins, 1980). Extruded flaxseed and salmate diets resulted in greater milk yield compared to control diet. Extruded flaxseed and salmate diets increased milk yield by ١٣.٦٥%, and 2.4%, respectively. In addition, milk fat (%) was significantly reduced in extruded flaxseed and salmate groups compared to control groups (3.04, 3.38 vs. 3.68). This is consistent with supplementing 200 g/d of fish oil, which resulted in a 26.0% reduction in milk fat compared to 200 g/d of olive oil (Mattos et al., 2004). When energy corrected milk was calculated, extruded flaxseed diet significantly (P<0.05) increased energy corrected milk compared to other groups. In this regard, the addition of 0.5-0.7 kg diet/d per cow from 21 days prepartum to 7 months postpartum has a potential effect on the milk yield of dairy cows (Moallem et al., 2020; Beauregard et al., 2023). The boost in milk production of extruded flaxseed diets could be highly related to their effects on comparable dry-matter intake (Table I), improved feed digestibility, increased energy intake and metabolism, improved rumen function (Moats et al., 2018) and enhanced hormonal activity including insulin growth factors-1 (Table V). In addition, FFAs seemed to cause a state of insulin resistance, increase the amount of glucose for synthesis of lactose and consequently for milk production (Andersen et al., 2008). Milk production efficiency (kg milk/kg feed) was significantly improved over feeding extruded flaxseed diet when compared to salmate and control diets (Table I). Of note, in the present trial, changes were observed in not only the milk yield by the addition of extruded flaxseed to the diets of lactating cows, but in the fat and energy corrected milk also as indicated in other studies (Moallem et al., 2020; Beauregard et al., 2023). Beauregard et al. (2023) estimated that CH4 intensity was reduced by 1.3 g/L of milk (9.2%) in herds receiving extruded flaxseed. Moreover, the values of IGF-1 indicated the highest in flaxseed group followed by salmate and control groups, respectively. It seems that the values of IGF-1 in the groups follow the milk production curve in cattle, where the values of IGF-1 increased till week 6 and decreased thereafter in all groups. This is consistent with the direct and indirect roles of IGF-1 on milk production through mammary gland development, milk synthesis, nutrient uptake, hormonal regulation and energy balance (Meyer et al., 2017).

CONCLUSION

The results of the current trial show that the extruded flaxseed (7.0%) or salmate (25 g/head/day) in diets of commercial lactating Holstein farm did not show any notable negative effects on feed intake. Additionally, milk production, fat and energy corrected milk, milk efficiency (kg milk/kg feed) were significantly improved due to extruded flaxseed feeding. The positive effects extended to milk composition through the ration of omega-6: Omega-3 ratio. Simultaneous improvement was confirmed in IGF-1 through the period of study.

ACKNOWELGMENT

The authors want to thank and acknowledge Deanship of Scientific Research, King Faisal University, Saudi Arabia for funding and support (GRANT5826).

Funding

The authors would like to acknowledge the support of the Research and Development Department of the Arabian Agricultural Services Company (Arasco).

IRB approval

The approval of the study was granted by the Ethical Research Committee of King Faisal University, Saudi Arabia.

Ethical statement

Animals care in the current trial was approved of the scientific research deanship ethical standards of King Fisal University (Ref. No. KFU-REC).

Statement of conflict of interest

The authors have declared no conflict of interest.

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