Effect of dietary incremental levels of flaxseed supplementation on productive performance of lactating Damascus goats

— It is believable that supplemental essential fatty acids can change the fatty Acid (FA) composition in the milk. Feeding flaxseed to dairy animals improves milk production and milk quality, resulting in healthier milk for consumer. So, the objective of our study was to evaluate the effect of inclusion of ascending levels of flaxseed in Damascus goat's ration on performance and milk composition. Twenty-four of lactating Damascus goats (39.60 ±0.50 kg weight and 2-3 years old) were divided into three groups (randomly, eight animals each). The basic diet of control group (T1) consisted of 56.67% concentrate feed mixture (CFM) and 33.33% alfalfa hay and supplemented with 10% full fat soya, while the other groups were supplemented with 5% flaxseed + 5% full fat soya (T2) and 10% flaxseed (T3), respectively. Inclusion of higher level of flaxseed (10%) in goat’s ration increases dry matter intake (DMI) with the positive effect on digestibility of most nutrients. In addition, rumen fermentation was affected with increased fat supply where levels of total volatile fatty acids ( TVFA’s ) and ammonia-N (NH 3 -N) are increased with reduced rumen pH values in animals fed on T3. In this study, significant increase of blood plasma total protein, globulin, albumin, urea and high-density lipoprotein concentration, whereas significant decrease of triglycerides, cholesterol and Low-density lipoprotein concentration in response to higher supplemental fat than T1 and T2. Goats supplemented with higher level of flaxseed recorded higher body weight, milk yield and fat corrected milk (FCM) yield, milk fat, protein and total solid content than the other groups (T1 and T2). In conclusion, higher flaxseed supply in dairy Damascus goat's diets resulted in improved total tract digestibility, feed efficiency and rumen fermentation parameters and milk production, milk composition while reduced blood lipids.

This study aimed to evaluate the effect of increment of flaxseed supply levels (two levels versus control) in Damascus goat's ration on its productive performance during lactation period.

II.
MATERIALS AND METHODS This experiment was conducted at the Mariout Research Station (30 km to Alexandria) and labs of animal nutrition department, Desert Research Center (DRC) , El-Matarya , Cairo, Egypt.

The experimental animals, design and rations
Twenty-four Damascus goats (39.60 ±0.50 kg and 2-3 years) were randomly divided into three groups (eight animals each). All of the experimental groups were fed on 90% basal diet that consisted of 56.67% concentrate feed mixture (CFM) and 33.33% alfalfa hay) and supplemented with one of these supplements:10% full fat soya (T1), 5% flaxseed + 5% full fat soya (T2) or 10% flaxseed (T3), respectively. Three experimental rations were formulated to cover goats requirements according to (NRC 1981). The chemical composition of the feed ingreadents and the experimental rations are presented in Table (1). Complete rations (concentrate + alfalfa ) were offered twice daily at 7 am and 4 pm in quantities sufficient to allow free choice access to the ration, and animals have free access to clean fresh water. The animal weighed biweekly befor morning feeding and the orts were determined. Oilseeds Fatty acids analysis Fatty acids contents of soybean and linseed were analyzed according to AOAC, (2000) using Ultra Gas Chromatographs (Table 2).

Digestibility trials
A digestibility trial was performed at the end of lactation period and samples were taken through 45 days of lactation period. The feces were collected using fecal grab samples method from all doses, three times daily (7.00, 14.00 and 18.00) for three consecutive days. Acid-insoluble ash was used as an internal marker to estimate fecal output and nutrient digestibility. The digestibility coefficient of a given nutrient was calculated according to the following formula (Van Kulen and Young, 1977):

Blood samples
At the end of the experimental trial, blood samples were taken from 4 animals for each group (the same animals were used to get rumen liquor content sample). A sample of 10 ml of blood per animal was withdrawn from the jugular vein before morning feeding. The blood samples were directly collected into vacationer tubes (containing EDTA as an anti-coagulant). The blood plasma was obtained by centrifuging the blood samples soon after collection at 4000 rpm for 15 minutes. Blood plasma was transferred into a clean dried glass vials and then stored in deep freezer at -18º C for subsequent specific chemical analysis.

Milk samples
Daily milk yield (DMY) was individually recorded weekly after colostrum period, up to 12 th week of lactation. Doses were kept away from their kids for 12 h (9 pm: 9 am) (overnight), and then one teat was hand milked while the second teat was left for suckled kids. The daily milk yield was determined in two consecutive days the first for left teat and the second for right teat. Consequently, DMY was estimated as an average of the two teats. Milk was multiplied by 4: (2 teats X 2 (two half day) to complete 24 h) (Alsheikh, 2013). Milk samples were obtained weekly from each goat for 12 weeks and stored in glass bottles (50 ml) then analyzed to determine milk composition.

Analytical methods Feedstuffs and fecal analysis
Samples (feeds and feces) were oven-dried (55° C for 72 h), then ground in welly mill fitted with a 1 mm screen (local manufacture). Feeds and fecal samples were subjected to proximate chemical analyses crude protein

Determination of basic rumen fermentation parameters
The pH of rumen liquor was immediately recorded using Gallen Kamp pH Stick pH K-120 -B. quantitative analysis of ammonia concentration was carried out by a modified Nessler's method modified by Szumacher-Strabel et al. (2002) and total volatile fatty acids (TVF's) were determined by steam distillation according to Warner (1964). Biochemical analysis of blood plasma Blood serum samples were analyzed using commercial kits (Human Co. Germany). Total protein, albumin, urea, and creatinine were used as indicators for kidney function, while alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were used as indicators for liver function and lipid profile (triglycerides (TG), cholesterol, high-density lipoprotein (HDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol and total lipids) as indicators for fat mobilization. All measurements were done using Jenway spectrophotometer (UK) and the kits purchased from Human Co. Globulin concentration was calculated by subtraction of total plasma protein and plasma albumin. The albumin /globulin (A/G) ratio was calculated.

Milk analysis
Milk samples were analyzed for total solids, fat, total protein and lactose by infrared spectrophotometry (Foss 120 Milko-Scan, Foss Electric, Hillerød, Denmark). Solids-not-fat (SNF) was calculated by difference. Fat corrected milk (4% fat) was calculated by using the following equation according to Gaines (1928):

Statistical analysis
Data were statistically analyzed using (SAS, 2006). Separation among means was carried out according to Duncan Multiple Range test (Duncan, 1955). Data of body weight changes, digestibility and blood parameters were statistically analyzed according to the following model: Y ij = μ + T i + e ij , Where y ij = represents observation, μ=: the overall mean, T i = effect of treatment (experimental group), e ij : experimental error. While the data of rumen fermentation parameter and milk production were statistically analyzed according to the following model: Y ij = µ + T i +S+ an(t) +S*T + e ij . Where: Y ij = the observation on the I th treatment, µ = Overall mean, T i = Effect of the I th treatment, S = Effect of the period, an (t) = Effect of the animal in the treatment and e ij = Random experimental error.

Effect of experimental rations on digestibility and nutritive value
Animals supplemented with the highest level of flaxseed (10%, T3) recorded significant higher digestibility of all nutrients (DM, P=0.019, OM, P=.044, EE, P=0.007, CF, P=0.02 except CP showed non significant differences P=0.45 and nitrogen free extract (P=0.056) compared to 0 and 5% levels (T1 and T2) (table 3). improved digestibility with 10% flaxseed supply may be due to that flaxseeds are small, flat and oval-shaped (2×5 mm), therefore, flaxseed may result in 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, while promoting feed intake, increase the energy content of the diet and gives a partial protection versus microbial attack or reduces the impact of oil on ruminal microbial or both, leading to negligible effect on the digestion of fibers as well as Improved CP digestibility The reduction in CF digestibility in the animals fed ration of T1and T2 (supplemented with 10 and 5% full fat soybean) compared to the animals fed ration of T3 (supplemented with 10 % flaxseed) may be due to that the fats in full fat soy is not protected and affect negatively on rumen function and cellulolytic bacteria which led to decrease fiber digestion on the contrary for flaxseed the fat is protected as indicated by Improved feed digestibility in the present study resulted in significant enhancement of nutritive value as total digestible nutrients (TDN, P= 0.001 % with 10% flaxseed supplementation (T3). However, digestible crude protein (DCP%) increased (P=0.009) with 10% soybean supplementation. This may be due to that the ration containing 10 % soybean recorded higher CP contents (20.37) compared to the other experimental treatments

Effect of experimental rations on Feed intake
Results of dry matter intake (DMI) Table (4) showed that supplementation with higher level of flaxseed (T3) resulted in numerically higher dry matter intake (DMI) during the lactation period. This may be attributed to the increment in nutrient digestibility (table 4) which promote rumen discharge consequently force the animal to eat a lot.  The goats fed on 10% flaxseeds recorded numerically higher TDN intake compared with the other experimental groups (T1 and T2) in response to increase TDN content for ration of T3 compared to T1 and T2 (table  4). On the other hand, the animals of T1 recorded higher crude protein intake (CPI) and digestible crude protein (DCPI) compared to T2 and T3 as a result of increased CP content for ration T1 (table 1) as well as increase of DCP content for T1 compared to T2 and T3 (table 4).

Effect of experimental rations on rumen fermentation parameters
Concerning ruminal fermentation parameters Table  (  This controversial in results may be due to the level of supplement and it's form (oil or seed), experimental animal, experimental ration or experimental conditions as whole. Regarding the ruminal pH level, it is decreased significantly with higher level of flaxseed supply and this may be related to increased production of TVF'S resulting in decrease in pH value.

Effect of experimental rations on blood parameters
Blood plasma concentrations of total protein (TP), albumin and globulin (Table 6) were increased significantly (P<0.0001) with higher flaxseed level (T3) compared to the other experimental groups (T1 and T2). This may be due to that T3 recorded the highest CP digestibility (table 3) Table 2). In this connection Harris et al. (1997) found that (ω-3) fatty acids reduce plasma triglyceride levels, by inhibiting the synthesis of lowdensity lipoprotein and triglycerides in the liver. The present results supported this concept because about 53% of fatty acids content of flaxseeds are α-linolenic acid (ω-3) (table 2) that inhibiting the synthesis of very low-density lipoprotein cholesterol and triglycerides in the liver. Consequently, feeding whole flaxseed increased blood concentrations of (ω-3) fatty acids and decreased the ω-6 fatty acid level in blood (Petit, 2002). It is also possible to attribute the reduction of cholesterol and triglycerides levels to flaxseed CP content, where Bhathena et al. (2002) found that flaxseed proteins were effective in lowering plasma cholesterol and triacylglycerol levels compared to soybean and casein proteins in obese rats. The gradual increase (P=0.0001) in level of high-density lipoprotein (HDL) in blood plasma of animals fed on rations supplemented with 5 and 10% flaxseed in the current study was matching with the reduction of cholesterol, triglycerides and LDL levels because HDL removes fats and cholesterol from cells including within artery wall and transport it back to the liver for excretion or reutilization (Peter, 2005). Blood urea concentration was increased in animals fed on ration supplemented with 10 % flaxseed compared to the animals fed ration supplemented with zero and 5% flaxseed ( Table 6). This increase in urea concentration was supported by the increased CP digestibility (Table 3) as an indicator to improved protein metabolism and improved N utilization with increasing flaxseed level. These results are also supported with higher levels of plasma total protein as an indicator for improved protein metabolism in liver. In this line, Sharma e t al. (1972) reported lower urea N concentration is usually reported with decreased N digestibility and vice versa.
Regarding creatinine levels, animals fed on T1 recorded significantly higher levels of creatinine than other treatments (T2 and T3), but all values were within the normal range indicating normal renal function. Blood plasma level of aspartate amino transferase (AST) was similar among treatments while flaxseed supply stimulates (P<0.01) blood alanine amino transferase (ALT) activity and its highest level was recorded in goats supplemented with higher level of flaxseed (T3) compared with other treatments although ALT activity lies within the normal range in all treatments. Nudda et al., (2013) agree with the present findings and they found that inclusion of extruded linseed in dairy goat's diets did not affect renal and hepatic function biomarkers in serum except AST and ALT which tended to differ.

Milk yield, Composition and feed conversion ratio
Data of Table, (8) showed the effect of experimental treatment on milk yield and its composition. Introducing higher level of flaxseed in goats diets (T3) increased milk yield (P<0.01) and improved its composition compared with milk of goats fed T1 or T2 rations. This may be due to increased DM and TDN intake (table 5), improved nutrients digestibility (DM, OM, CP, CF, NDF and ADF) in goats fed on T3 ration (Table 4)  Also, increased percentage of solids not fat (SNF) in the same pattern (P<0.05) may be due to increased protein and lactos in milk hence SNF are residual substances after extraction of fat from milk. lactose % results didn't affected in the current study similar to Miroslava et al. (2013) with goats fed flaxseed. The previous results of the current study indicating general and mostly significant improvement in animal performance (increased DMI, nutrients digestibility, milk yield and all milk macro compounds) with increased supply of flaxseed (T3) so, this improvement associated with the best (P<0.01) feed conversion ratio (FCR) either related to milk yield or to fat corrected milk.

IV.
CONCLUSION In conclusion, flaxseed supplementations in Damascus goat's diets during lactation period, lead to improve total tract digestibility, reduced blood plasma lipids and rumen fermentation. Also, flaxseed increase milk production (milk yield and fat corrected milk yield), milk fat content and protein concentration in milk. Finally, flaxseed inclusion (10%) has beneficial impacts on the fat profile of milk producing healthier dairy products for consumers. Further studies should be conducted to obtain the best inclusion level of flaxseed to get more benefits.