MATERIALS AND METHODS

Study area: This study was carried out at Reda Mansour Farm, in Elnobaria city, Alexandria, Egypt (June-July, 2018) regarding field trial, analysis of feeds, faeces, blood and milk take place in the Department of Animal Production, Faculty of Agriculture, Cairo University, Giza and Department of Dairy Sciences, National Research Centre, Giza, Egypt, through the period from August, 2018-March, 2020.

Experimental oil seeds: Two oilseeds were used in extruded forms (linseed and soybean seeds) in this study. They were exposed to the extruding process for 90 sec at 150°C with 130 rpm speed by using the SX85-II Twin-screw extruder from Shandong LUERYA Machinery Manufacturing Co., Ltd. No. 114, Dougou Industrial Park, Shizhong District, according to Harper²⁴. The chemical composition and fatty acids profile of the experimental oilseeds according to Chouinard et al.²⁵ showed in Table 1.

Experimental animals: Sixty dairy Damascus goats in average live weight (40 kg±1 kg), lactation seasons 2^nd and 3^rd with average daily milk yield 1300 g. Goats were divided into 4 groups each group contained 15 goats according to the season of lactation and live body weight. The experiment took place 60 days divided into the periods, 30 days preparation period then samples collected two times each 15 days. Samples were collected during 3 consecutive days in each period.

Experimental rations: The experimental rations for the experimental animal's groups were as follow: all of the treatments fed corn silage plus concentrate feed mixture (CFM), Roughage: Concentrate ratio was 50:50 in all groups to cover the total requirements of energy and protein needed for dairy goats’ maintenance and milk production according to NRC²⁶. Formulation of experimental concentrate feed mixtures presented in Table 2. The chemical composition of corn silage used in the feeding trial was as follows 7.2% crude protein, 26.80% crude fibre, 2.30% ether extract, 42.10% neutral detergent fibre and 25.60% acid detergent fibre.

Feeding procedures: The concentrate feed mixtures were offered to all animals after milking time (6 am and 4 pm). Corn silage was offered ad libitum for all animals but the quantities were recorded. Water was always available.

Milk recording and sampling: Goat’s milk was obtained by hand milking system two times daily at 6 am and 4 pm. The daily milk yield was individually recorded and corrected to 4% FCM by the following formula according to Gaines²⁷:

During the 3 days, collection period the milk samples were individually collected from each and stored at (-18°C) for further analysis.

Digestion trials: At the end of the experiment faeces samples were withdrawn by the end of each experimental period at 6 am for three successive days from each animal from the rectum, then dried at 70°C for 24 hrs. Dried faeces samples were kept individually in polyethylene bags for chemical analysis. Digestion coefficients were calculated for all animals by the acid insoluble ash (AIA) method, using silica as an internal marker according to Van Keulen and Young²⁸.

Nutrients digestibility were calculated according to the following formula:

Nutritive values as total digestible nutrients calculated according to McDonald et al.²⁹ as follows:

Blood sampling: On the final day of the sampling period, blood samples were individually taken from the jugular vein of individual animals. Blood samples were directly collected into clean dried heparinized glass tubes and centrifuged at 4000 rpm for 20 min. Blood plasma was then transferred into a clean dried glass vial then stored at -18°C until the chemical analysis.

Milk analysis and fatty acids profile: Chemical analysis of milk fat, protein, solids not fat, total solids and ash were determined by using Master Classic Ultrasonic Milk Analyzer. Milkotester Ltd. 49 Hristo Botev Str., 4470 Belovo, Bulgaria. One gram from each milk sample to determine the fatty acids profile was dissolved in 10 mL hexane and 1 mL of sodium methoxide (5.4 M) in methanol solution. After strong vertexing for 1 min, 1 mL of the clear hexane layer was extracted by filtering through PTFE membrane, transferred into 2 mL GCMS vial from which 2 μL was injected for GCMS analysis, Instrument used: GC/MSD 5977A, Agilent, USA, Column used: Agilent, DB225 60 m×250:m×0.25: m. Oven program: 40EC for 1 min then 7.2 EC min^–1 to 195 EC, 2.3 EC min^–1 to 230 EC for 15 min Inlet: Split mode, split ratio 25:1 Liner Agilent 5190-2294: 990: L Inlet Temperature: 250 EC. Auxiliary temperature: 250 EC.

Feed and feces analysis: Samples of feeds, rations and faeces were analyzed for DM (A.O.A.C³⁰, method 934.01), ash (no. 942.05), crude protein (no. 968.06), crude fibre (A.O.A.C. No. 942.05) and ether extract (no. 942.05) according to A.O.A.C.³¹. The Organic Matter (OM) was calculated as the difference between DM and ash contents. Also, nitrogen-free extract calculated by difference according to the following Eq.:

Neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents were analyzed sequentially (Van Soest et al.³²) using the ANKOM200 (ANKOM Technology 2052 O'Neil Road, Macedon NY 14502).

Blood plasma analysis: Blood plasma constituents were determined using commercial kits. Total protein and creatinine were determined as described by Tietz³³ and Walker³⁴, albumin was determined according to Doumas et al.³⁵, urea was determined according to Patton and Grouch³⁶. Blood plasma triglycerides were determined according to Lopes et al.³⁷ and Bucolo and david³⁸ and plasma cholesterol was measured according to Allain et al.³⁹.

Statistical analysis: Data were analyzed using the general linear model procedure of SAS⁴⁰. One-way ANOVA procedure used to analyze data following the next model:

where, μ is the overall mean of Y_ij, R_ij is the treatment effect, E_ij is the experimental error. The differences among means were separated according to Duncan’s New Multiple Range Test (Duncan’s⁴¹).

RESULTS AND DISCUSSION

Chemical composition of the experimental rations: Chemical composition and fibre fractions contents of the experimental rations in the Table 3 cleared that rations were closest in all values except ether extract (EE) content was higher in R₃ (8.94%) followed by R₄ (7.22%) then R₂ (5.77%) compared with control diet R₁ (4.27%). These variances reflected the addition of Full-fat extruded oilseeds, where R₃ contained 5% full-fat linseed with 35% fat mixture and R₂ contained 5% Full-fat soy seeds with 18.8% fat. Ration two contained 2.5% of each type of oilseeds.

Digestibility and nutritive values: Results of digestion coefficients and nutritive values shown in Table 4 revealed that no significant differences among all rations in DM digestibility. however, R₂ (mix of linseed and soy seed) recorded lower significant values in OM, CP, CF, NFE and NDF digestibility comparing with control and other experimental rations. The ratio in R₃ linseed recorded the highest values of fat digestibility (90.71%) compared to the rations. On the other hand, non-significant differences were observed among all ration treatments of ADF digestibility.

Meteab et al.¹ explained the positive effect of linseed addition by 10% to dairy Damascus goats’ rations through the higher possibility of escaping from mastication so, increased passage rate from the rumen and packaging the fat and protein in such a way not to negatively affect rumen function. In the same context, Khorasani et al.⁴², Syed et al.⁴³ and Kim et al.⁴⁴, suggested that oilseeds promote feed intake, increase the energy content of the diet and give partial protection versus microbial attack or reduce the impact of oil on ruminal microbial or both, leading to negligible effect on the digestion of fibres as well as improved CP digestibility.

Nutritive values expressed as total digestible nutrients (TDN) and digestible crude protein (DCP) in Table 4 showed that experimental seeds achieved higher values in TDN in case of separate inclusion in the ratio (R₃: 77.14% and R₄: 77.15%) but the (R₂) ration recorded the lower value (69.06%) comparing with control ration (R₁:74.65%). At the same time, no significant differences were observed among treatments in DCP, 11.7, 10.65, 11.06, 11.30 with R₁, R₂, R₃ and R₄, respectively. These results agreed with those findings by Meteab et al.¹ when dairy goat ration contained 10% whole linseed.

Milk yield and milk composition: Data in Table 5 cleared that ration three with extruded linseed recorded the highest (p = 0.002) daily milk production (1481 g day) by 19% more than the control ratio followed R₄ and R₂. The same trend of actual milk yield observed fat corrected milk where results being, 1290, 1108, 1080 and 1021 g/day with R₃, R₄, R₂ and R₁ (p<0.05). Results of the chemical composition of milk cleared the positive (p<0.05) effects of linseed in R₃ on milk fat contents 3.14% compared with other rations showed in Table 5. On the other hand, the ratio with soybean seeds recorded a lower value of 2.68% and that was lower than the ratio with a mix of two extruded seeds (R₂:3.08%) and control ratio (R₁:3.00%). Regarding other contents of milk, protein, lactose, lactose, total solids, solids not fat and ash did not observe any significant differences among experimental rations.

Generally, Nudda et al.⁴⁵ determining factors it could affect the chemical composition of milk, in terms of fat content and its fatty acid profile as follow: diet (composition and availability), animal (breed, lactation stage, body condition) and environmental (especially cold and heat stress). In the same context, Hermansen⁴⁶, Dhiman et al.⁴⁷ cleared that the addition of oilseeds in dairy rations have been many advantages when its inclusion in the diet. The oil in the seed is believed to be slowly released when the seed is masticated, which may help decrease detrimental effects on rumen fermentation (Harfoot and Hazelwood⁴⁸) and increase the efficiency of milk fat synthesis^49,50.

The same trend was observed with Meteab et al.¹ when linseed used by 10% in Damascus dairy goats’ rations. These results may be due to improvement in nutrients digestibility, which is leading to increased nutrients availability for milk constitutes synthesis. Similar observations were reported by Chilliard and Ferlay⁵¹ who generally observed that increase dietary lipids led to increasing milk yield, Gomez-Cortes et al.⁵² in ewes, Hurtaud et al.⁵³ in dairy cows and Abd El-Aziz et al.⁵⁴ in dairy buffaloes with linseed. Also, higher fat corrected milk (FCM) and fat content% in the milk of R₃ fed goats were attributed to high-fat content of linseed consequently high energy source. Moreover, Bernard et al.⁵⁵ and Bionaz et al.⁵⁶ found that fats as dietary supplements encourage the nutrient toward the mammary gland instead of toward fat deposition in the adipose tissue and activate the lipogenic gene expression at the mammary gland, leading to an increase in milk fat secretion. Moreover, the use of whole linseed and soybean seeds as protected fatty acids inside a seed coat did not disturb rumen function so, increased mammary lipogenesis because of the increased supply of unsaturated fatty acid (Table 6). Gargouri et al.⁵⁷ and Nudda et al.⁵⁸ consistent with the current results, in sheep conversely,

Martin et al.⁵⁹ reported decreased FCM yield and fat content on feeding lactating Holstein cows on extruded linseed and linseed oil diets and they explained these findings by lower DMI and lower digestibility of fibre due to the high level of oil intake. However, Petit¹⁰ reported no change in milk yield with the feeding of (13.3%) whole linseed and Petit and Cortes⁶⁰ when feeding of (72 and 36 g kg^–1 DM) the whole linseed. Increased milk protein concentration numerically in R₃ and R₄ fed goats may be due to the increased CP digestibility (Table 4) and increase blood total protein and albumin (Table 7). Nudda et al.⁵⁸ agreed with the present results, who reported that linseed supplementation to Saanen goats led to increased milk protein concentrations because of higher protein availability in the intestine. Milk total solids (TS) were increased with an increased level of linseed supply (R₃) than the other groups. This may be due to the increasing content of fat and protein in milk. These results agreed with Silva-Kazama et al.⁶¹ with dairy cows.

Milk fatty acids: Data of milk fatty acids profile in Table 6 cleared the positive effects of extruded oil seeds on long-chain fatty acids contents. Whereas the R₄ with soybean seeds recorded higher values (p<0.05) with C14, C15 and C16 being 10.18, 1.36 and 34.52%, respectively than other experimental rations. Regarding C18 isomers fatty acids, The R₃ (linseed ration) observed the highest values oleic (C18:1c, 35.70%) and linolenic (C18:3, 0.57%) incomparable with other groups of goats. Many researchers had been explained that the milk fatty acid (FA) profile can be modified to increase the proportion of monounsaturated and unsaturated fatty acids (UFA) and decrease the proportion of medium-chain FA by supplying oilseed to dairy rations^62-64. A wide range of positive health effects has been demonstrated for PUFA by lowering insulin resistance associated with cardiovascular disease^65,66.

Thus, increasing the concentration of PUFA in milk may be beneficial to public health and enhance the consumption of dairy products.

Blood parameters: Results of blood samples in Table 7 cleared that no significant differences among experimental animal groups with different rations in blood constituents except cholesterol contents. Whereas total protein, albumin and creatinine had the closest values in all experimental groups. Numerically R₃ recorded higher values 29.61 mg dL^–1 in triglycerides compared with other rations being 25.99, 24.58 and 21.23 with R₂, R₄ and R₁, respectively. On the other hand, blood urea recorded a higher value with R₄ 15.38 mg dL^–1 comparing with 11.52, 10.29 and 10.24 mg dL^–1 with R₂, R₃ and R₁, respectively. These results agreed with Li et al.⁶⁷ because the addition of lipid to animal diet generally increased plasma lipid contents. The same trend was observed with Rafalowski and Park⁶⁸, when dairy cows fed on diets that contained whole sun flower seeds and amounts increased from 10 to 30% in the concentrate compare with control cows. Also, Cozma et al.⁶⁹ noticed the increase in total blood lipids when dairy goats fed on hemp seed oil by 4.7% from daily dry matter, at the same time there was a significant difference in lipids fraction in blood.

Generally, the results of the study cleared that oilseeds such as linseed and soybean could be used in the extruded form to replace up to 5% of soybean meal in goat rations. Also, data of digestion coefficients and feeding values confirmed those seeds consider in a full-fat extruded form considered a good source of energy and protein in dairy goats. At the same time, the addition of oilseeds had effects positively on the milk fatty acids profile of goats.

CONCLUSION

Results of milk yield, milk fat and fatty acids profile of milk cleared the significant effects of linseed addition in the extruded form with dairy goats. Results of soybean addition individually were not promising that may be related to fatty acid profile and some of the anti-nutritional factors, so this issue needs more investigation with the Damascus goats. Generally, there were appositive effects of oilseeds on digestibility, milk and fatty acids without any adverse effects on blood parameters, so we suggest using extruded linseed in goats ration to achieve high yield milk production and beneficial milk fatty acids profile for both newcomers and humans and more immune boosters in blood.

SIGNIFICANCE STATEMENT

This study discovers the possible effect of using extruded linseed in dairy goats rations alone or combination with Full-fat soy seeds in milk yield, milk fatty acids profile and blood parameters. Results indicated that the milk fatty acids profile of dairy goats could be changed by changing the feed formula structure to produce functional milk with a high concentration of polyunsaturated fatty acids. This study will help researchers for more investigations on different oilseeds or with different levels for linseeds and soybean seeds.