Effect of herbal feed additives on milk performance and health status of dairy goats

After many years when antibiotics were used in animal feeds to improve animal performance, the European Union banned their use (15). Interest in natural feed additives that improve animal health, raise livestock farming productivity and enhance the quality of animal products is therefore increasing among farmers and the scientific community (19). Feed additives containing phytochemicals are a promising alternative to antibiotics. These additives, especially polyphenols, are biologically active chemical compounds found in plants which provide health benefits beyond those attributed to macronutrients and micronutrients (10). Phytochemicals accumulate in different parts of the plants: the roots, stems, leaves, flowers, fruits or seeds. Medicinal plants, commonly known as herbs, are particularly rich in these compounds (6), and when used in the diet of ruminants may enhance feed taste and stimulate appetite. As regulators of digestive functions, they influence the motility of the digestive tract and the secretion of digestive juices, reduce the occurrence of diarrhoea, and regulate the pH of the digestive tract, ruminal fermentation and bacterial diversity (11). They can also have a protective effect as metabolism regulators and a beneficial one on animal product quality (30). Some herbs have anabolic, anti-stress and strengthening properties, can even counteract the negative impact of anti-nutritional substances in feed, and by demonstration in lactating cows, they often increased milk production (18). The bioactive properties of polyphenols also play a significant role in preventing many chronic diseases. The largest group of naturally occurring polyphenols are flavonoids, which include apigenin (AP). Chlorogenic acid (CA) is a polyphenolic compound produced by plants through the shikimic acid pathway during aerobic respiration (13). Both these compounds have antioxidant, anti-inflammatory and anticancer properties, can inhibit platelet aggregation and can reduce the level of low-density lipoproteins in plasma and cell proliferation (16). Apigenin occurs mainly in the form of glucosides in herbs, including chamomile and thyme, and in vegetables and fruits (23).

Because of the biological activity of AP and CA, their concentration level in plants as well as bioavailability for humans and animals are of great importance. Karaźniewicz-Łada et al. (13) observed significantly higher concentrations of AP and CA in the serum of dairy goats fed a diet supplemented with 40g/day/animal of a polyherbal additive compared to AP and CA concentrations in the serum of an unsupplemented control group. These results indicate the positive nutritional effect that may improve goats’ health and impart health benefits to human consumers of dairy goat products (13). Other studies conducted on goats have shown the positive effect of nutritional herbal additives on milk production and composition and on intestinal lactic acid bacteria count (8). Kholif et al. (15) demonstrated that a supplement of 10g/goat/day of rosemary and lemongrass had a significant positive effect on daily milk yield and milk chemical composition (P-value < 0.001). The authors also demonstrated that the fat in the goats’ milk contained a significantly higher proportion of unsaturated fatty acids and conjugated linoleic acid and a lower proportion of total saturated fatty acids (P-value < 0.05). Most studies did not show any negative effects of herbal supplements on the health status of animals (9). However, because of the wide variation in the composition and dosage of herbal supplements for farm animal feed, assessing their impact on animal health is exigent. The aim of this study was to investigate the impact of multiherbal feed additives administered to dairy goats in the amount of 20 or 40 g/animal/day on the production and chemical composition of milk, as well as on the health status of the experimental animals. The hypothesis was tested that herbal feed additives used in goat diets positively affect the animals’ health, productivity and milk composition. To the best of the authors’ knowledge, very little scientific literature comprehensively discusses this issue, which is nevertheless of great scientific and practical importance.

The effects of herbal supplements (feeding group) and time of test-day milking and milk sampling on milk yield, milk composition, processing properties and SCC are presented in Table 3. The effect of the feeding group was statistically significant on fat percentage in milk (P-value = 0.0323). In the milk of experimental goats, this percentage was significantly higher than in the milk of the CTR group (P-value < 0.05). Milk obtained from the 7/20 g group had the highest fat level – 4.32% – which differed statistically significantly (P-value < 0.05). Moreover, a significant effect of herbal supplements was also noted for fat : protein ratio (FPR) and pH acidity (P-values respectively 0.0026 and 0.0074). The time of test-day milking and milk sampling had a significant impact on the levels of all studied milk parameters (P-value = 0.0001). Generally, the basic composition of milk (percentage of fat, protein, casein and dry matter) in the 16^th (and last) week of the experiment was characterised by a higher level of values compared to the level recorded during the first test-day milking (week 4).

At the same time, milk yield and fat-corrected milk yield were significantly influenced by the group × time interaction, with P-values of 0.0003 and 0.0037, respectively. This indicates the level variation of a given factor over time in particular feeding groups. The reaction of the animals to the herbal supplement varied. For example, animals from the 7/20 g group experienced a gradual decrease in milk yield from the beginning to the end of the experiment. Milk production in the CTR group also had a downward trend during the first four weeks. However, in the period from the 8^th to the 12^th week of the experiment, we observed a reverse trend with yields reaching 3.15 kg of milk per day. The effect of the group × time interaction on milk acidity was significantly lower (P-value = 0.0490). The pH values of milk from individual nutritional groups obtained at different time intervals were typical of those of good, regular-quality goats’ milk.

Table 4 shows the mean values of haematological and haematochemical parameters for all dietary groups studied in this experiment. An Anderson–Darling normality test proved that the data were normally distributed (P-value > 0.05) with a Gaussian distribution, and no outlier values were found. None of the blood samples collected contained clots or underwent haemolysis. No effect of dietary group was found on RBC, HGB, MCV, MCH, MCHC, PLT, red blood cell distribution width coefficient of variation (RDW-CV) or WBC (P > 0.05). Mixture and dose did not affect any haematological parameter except HCT. The lowest HCT value was found in goats from the 9/20 g group and this was statistically significantly lower (P-value < 0.05); it was similar to that found in goats from the 7/40 g group, which was, however, not significantly lower (P-value > 0.05). It is worth emphasising that the HCT in the blood of goats from all feeding groups was within the reference range given by Aiello and Moses (1). The diet had no effect on the WBC. The proportions of neutrophils, lymphocytes, monocytes, eosinophils and basophils were also similar for all experimental groups (P-value > 0.05). The effect of the feeding group had a statistically significant impact only on one biochemical parameter – triglycerides (P-value ≤ 0.05). The lowest triglyceride concentration (15.67 mg/dL) was found in the blood serum of goats from the 9/40 g group and the highest concentration (22.83 mg/dL) was reported for goats from the 9/20 g group (P-value ≤ 0.05) (Table 4).

Data for APPs in the blood plasma of all five groups of goats are presented in Table 5. Because the distribution of Hp and SAA was significantly right-hand asymmetric (coefficients of asymmetry = 4.01 and 6.02, respectively) their concentrations were presented as the median, interquartile range and range. No significant differences in SAA concentration between the five groups were found (P-value = 0.195). Although the omnibus Kruskal–Wallis H test indicated significant difference between groups in Hp (P = 0.010), the post-hoc Dunn’s test did not confirm any significant difference in pair-wise comparisons – only Hp in the 7/20 g group was close to significantly higher than Hp in the control group.

The numbers of goats with APPs > RIs (12) are shown in Table 6. Haptoglobin and SAA were concurrently elevated >RIs in 3 out of 60 goats (5%), only SAA was elevated >RI in 6 goats (10%), and both APPs were normal in 51 goats (85%). Although a greater number of goats with increased Hp and SAA levels was found in the control group of animals, there was no significant difference in the proportion of goats with increased Hp (P-value = 0.190) or SAA (P-value = 0.197) between the five groups.

Spearman’s rank correlation coefficients between APPs and haematological and biochemistry parameters are presented in Table 7. Statistically significant (P-values ≤ 0.05 and ≤ 0.01) negative correlations between haematological parameters of blood plasma and the APP level were found between Hp and HGB, Hp and HCT and Hp and lymphocytes in blood from the 7/20 g group; between Hp and HGB and Hp and neutrophils in blood from the 9/20 g group; between SAA and monocytes in blood from the 9/40 g group; and between SAA and WBC and SAA and lymphocytes in blood from the CTR group. Positive correlations at the significance levels of P-value ≤ 0.05 and ≤ 0.01 were found between Hp and neutrophils in blood from the 7/20 g group; between Hp and HGB and Hp and MCHC in blood from the 9/40 g group; and between SAA and basophils in blood from the CTR group. Only one statistically significant negative correlation was found in the group of biochemical parameters, which was between Hp and HDL cholesterol in blood from the CTR group (P-value ≤ 0.05).

The experimental herbal additives contained seven or nine different herb species. The large number of herbs used and their relatively ready availability make the preparations suitable for universal use. When designing the composition of the mixtures, the authors were guided by the content of bioactive substances and the typical properties of individual species of medicinal plants. The selected plants are thought to have a beneficial effect on animals, mainly in terms of improving digestion and metabolism. The proportion of herbs with such an effect was 50% in the seven-herb preparation and also 50% in the nine-herb preparation; the effect of stimulating milk production was one possessed by a 35% proportion of the seven-herb mixture and a 40% proportion of the nine-herb mixture, and bacteriostatic and anti-inflammatory effects were attributed to 55% of the composition of the seven-herb supplement and to 60% of the composition of the nine-herb counterpart.

The chemical composition of milk from all feeding groups of goats did not differ from the average values typical for goats’ milk. These, according to Siddiqui et al. (25), are a pH value of 5.05–6.72, TS of 12.07–12.97%, lactose content of 4.00–4.79%, protein content of 2.20–3.40%, fat content of 2.25–4.08%, casein content of 2.5% and FDP of -0.560. The freezing point ranged from –0.561 to –0.564°C and was consistent with the average range for goats’ milk (28).

The physiological concentration of urea in goats’ milk is not defined, and in reviewed investigations its concentration fluctuated between 217 and 624 mg/L (4). The urea concentrations obtained in our experiment were between 299 and 330 mg/L and within this range. The SCC in the experimental milk ranged from 534 to 560 × 10³ cells/mL, confirming that its cytological quality made it suitable for the production of high-quality dairy products, including fermented drinks. The SCC in goats’ milk is generally higher than in sheep’s and cows’ milk (13). According to the research of Kaskous et al. (13), the SCC in the milk of healthy goats fluctuates between 200 × 10³ and 1500 × 10³ cells/mL and is 764 × 10³ cells/mL on average.

In the current study, we did not find any effect of the herbal supplement on milk yield or FCM. In the experiment of Kholif et al. (15), a supplement of 10g/goat/day of lemongrass or rosemary herbs significantly increased the milk production of Damascus goats (P-value < 0.001). Moreover, goats obtaining these herbal supplements produced milk with higher protein, fat and dry matter than the control group (P-value < 0.001). Replacement of a concentrate feed mixture with Moringa oleifera leaf silage and Chlorella vulgaris microalgae mixture in the diet of Damascus goats improved milk yield and milk composition, particularly daily production of protein, fat and total solids (P-value < 0.05) (15).

All haematological data obtained in our study are within the physiological ranges for goats (1, 7). The HGB, RBC, WBC, MCV, MCH, MCHC and PLT were not influenced by diet. In the literature, these results were reported for clinically healthy goats to lie within the ranges of 9.05–9.65 g/dL, 11.82–12.98 T/L, 10.40–11.88 G/L, 19.81–20.24 fl, 7.54–7.70 pg, 37.10–38.75 g/dL and 279.17–330.00 G/L for HGB, RBC,WBC, MCV, MCH, MCHC and PLT, respectively (1, 2, 7, 20, 21). The normal RBC values observed in this study indicate that no goats were suffering from haemolytic anaemia and that erythrogenesis was not depressed. The haematological parameters of healthy goats, in particular RBC, HGB, HCT, MCV, MCH, MCHC, PLT and RDW-CV, show several differences and depend on the breed, sex and age of the goat (3). Arfuso et al.(3) analysed the blood of five native Italian goat breeds and found an effect of breed (P < 0.05) on RBC, HGB, HCT, MCV, MCHC and PLT. They also found an age and sex interaction affecting one parameter: two-year-old Messinese goats had more erythrocytes and higher HGB concentrations than older (>5 years) Messinese female goats (P < 0.05).

In the current study, we found an effect of herbal supplements on HCT in the peripheral blood of animals. The HCT measured in the blood samples of the group of goats receiving a mixture of 7 herbs in an amount of 20 g per day/animal was 22.68% and was the lowest among all nutritional groups (P-value < 0.05) (Table 4). There are examples in the scientific literature of feed additives that reduce the level of HCT in the blood of dairy goats (27). Giorgino et al. (9) found that adding citric and sorbic acid and thymol and vanillin to the nutritional ration of dairy goats reduced the HCT percentage on the 54^th (and last) day of the experiment (P-value < 0.05). In this experiment, all the morphological parameters of blood were within the physiological ranges of clinically healthy goats (1), confirming that supplementation with citric and sorbic organic acids and thymol and vanillin pure botanicals has no negative impact on the metabolic status of dairy goats. The addition of these components increased the fat level in milk (P-value = 0.04). A beneficial, statistically significant effect of the supplement on the milk coagulation index was also found (9).

Alongside erythrocytes and thrombocytes, leukocytes are one of the most important morphological elements of blood. Their functions include absorbing and digesting microorganisms, producing antibodies, and for certain of them, triggering the reaction of other appropriate leukocytes. There are five types of leukocytes: neutrophils (NEU) – polymorphonuclear leukocytes, eosinophils (EOS) – acidophils, basophils (BA), monocytes (MON) and lymphocytes (LYM). The sum leukocyte count (WBC) and the percentages of NEU, EOS, BA, MON and LYM determined in this study were similar for all feeding groups (P-value > 0.05) and were within the range of reference values given by Brooks et al. (5) for clinically healthy animals.

We also found a statistically significant decrease in the concentration of triglycerides in the blood of animals receiving herbal mixtures, especially in the 7/20 and 9/40 g groups This may have been due to the presence of phytochemicals in the herbal supplements that have the ability to reduce their synthesis and absorption (24). A similar decrease in triglyceride concentration was also found by Mohammadabadi et. al. (17), who fed dairy goats with fodder containing button mangrove (Conocarpus erectus) leaves and twigs.

Acute phase proteins constitute a large group of plasma proteins which mainly come from the liver in response to the pro-inflammatory cytokines IL-1, IL-6 and TNF-α. During an acute phase reaction (APR), the concentrations of APPs in the blood plasma rapidly increase, while in healthy animals, APPs are undetectable or present in negligible amounts, as noted by Heller and Johns (12). These researchers nominate APPs as useful indicators for detecting animals with subclinical infections, determining the prognosis of clinical infection, differentiating between viral and bacterial diseases, monitoring treatment and assessing vaccine effectiveness and stress conditions, and they consider Hp and SAA to be the major APPs in sheep and goats. The concentration of APPs in the blood serum of goats is not found in a specific range for a specific disease, but estimating it may help determine the animals’ health status (12). In our research Hp and SAA were within the RIs for healthy goats, i.e. 0.399–1.242 g/L and 0.435–2.050 mg/L, respectively (12).

The effect of a given amount of concentrate feed in goats’ diet on the APPs in blood plasma was studied by Wang et al. (29). They found statistically significant differences in Hg and SAA concentrations between the groups which received a high, medium or low amount of concentrate feed (P-value < 0.05). The levels of Hg and SAA determined in their studies were much higher than those found in ours, and were 1.46–1.85 g/L and 4.39– 5.48 mg/L, respectively (29). In the same study, a diet rich in rice improved the slaughter characteristics and meat quality of young Liuyang Black goats, but had a negative effect on gut microbiota and induced an APR, as the blood plasma SAA concentration was significantly increased (P-value = 0.010).

The use of herbal supplements in the diet of dairy goats did not negatively affect their milk production, especially not milk yield or composition. In this study we found a positive effect of the administered multi-herbal mixtures on % fat concentration and fat : protein ratio in milk. Better results in this respect were achieved in the 7/20 g group. Time of test-day milking and milk sampling had highly significant effects on all studied milk parameters. Moreover, the feeding group × time of test-day milking and milk sampling interactions significantly affected milk yield and fat-corrected milk yield. The haematological and haematochemical parameters and APP plasma concentrations revealed no negative consequences of the supplementation of two multiherbal additives administered in the amounts of 20 or 40 g per animal per day. These findings encourage further research on herbal supplementation in the dairy goat diet.