The technology of green fodder production is especially important in arid and semiarid regions. Hydroponics improves on average the amount of crops in the same space, as traditional soil-based farming and can reduce water consumption compared to traditional farming methods. Limited research has been carried out on the use of hydroponic fodder and milk quality.
A comparative study of traditional (Malta farm) and hydroponic fodder (Gozo farm) was conducted in Malta with 20 cows of the Holstein–Friesian breed from two farms. Individual and bulk-tank milk samples were collected once a week for a period of 1 month in order to evaluate physical (pH, conductivity, density, freezing point) and chemical (fat, protein, ash, lactose, solid nonfat) parameters as well as mineral (Zn, Cu, Pb, Ba) content. Milk proximate and physical data were processed by analysis of variance (ANOVA) for repeated measures and an ANOVA procedure with farm and time as effects for minerals.
The results indicated differences in fat content and pH, showing higher
values (
The Maltese islands are situated at the center of the Mediterranean Sea,
with two major inhabited islands: Malta and Gozo. Their surface areas are
approximately 300 and 100 km
Milk composition is economically important to milk producers and processors, and it is nutritionally important to consumers. It has been known for years that variations in milk composition occur. However, the strong selection of cow breeds, particularly over the last 50 years, has reduced this type of variability considerably (Huppertz and Kelly, 2009). The composition of milk is made up of fats (on average making up 4 % of the milk), proteins (3.2 %), other “solids” (5.3 %), and water (87.5 %) (European Commission, 2006). Factors that affect milk composition include breed, genetic variation within breed, health, environment, management practices, and diet. Among the different dietary regimens worldwide, hydroponic fodder production is now widely accepted. There are some arguments about sprouting grains for convenience in green forage production with hydroponic systems to compensate for the feed resources for animals (Hassan et al., 2016). Hydroponic green fodder is produced from forage grains, having a high germination rate and growing over a short period of time in a special chamber that provides the appropriate growing conditions (Fazaeli et al., 2011). The development of this planting system has enabled the production of fresh forage from oats, barley, wheat, and other grains (Rodriguez-Muela et al., 2004).
In Malta, out of 11 428.5 ha utilized for agriculture, 5552.8 ha are used for the production of fodder crops (NSO, 2012). The fodder is either allowed to dry in situ and then harvested in bales or else harvested and silaged. Additional feed is imported and in some instances transformed into concentrates by local feed mills. Unfortunately, cows do not acquire the benefits of fresh pasture. The hydroponic fodder system is an ideal solution in places where there is limited land area for the growing of fodder or where pasture grazing is limited or nonexistent. It is also sustainable as it occupies a small land area, thus making it ideal for limited areas such as the farms in Malta. This system provides a considerable amount of fresh fodder with a high nutritional value every day at a low cost. Hence, this research aims to evaluate milk quality in terms of physicochemical characteristics and assess the content of Cd, Pb, Cu, and Zn in milk coming from dairy farms in which different feed regimens (traditional and hydroponic) are given.
The experiment was conducted on 20 cows of the Holstein–Friesian (HF) breed from
two farms, one from Malta (ML) (
Recently, particularly in GZ, farmers are feeding fresh hydroponic grass every day.
This is mixed with hay (alfalfa), local straw, silage, and concentrates,
while others are feeding hay, local straw, and concentrates to their cows. Both
farms feed nearly the same concentrates, but with different rations and
ingredients, using the total mixed ration (TMR) system. Feed was offered to
achieve 5 % refusal on the basis of the feeding practice followed
on both farms. The cows were milked two times per day at 05:30 and
15:00 and at 07:00 and 16:00 (GMT
Ingredients and chemical composition (% of DM) of Malta (MT) and Gozo (GZ) diets.
Hydroponic fodder barley was produced in a hydroponics chamber measuring
about 4 m
Weekly samples of individual ingredients were collected and subjected to chemical analysis. Samples were analyzed in triplicate for chemical composition using an Infrastar 1400RTW near-infrared spectrophotometer (Unity Scientific, Brookfield, USA), and values for crude protein, ethyl ether extract (fat), ash content, neutral detergent fiber (NDF), and acid detergent fiber (ADF) were used to calculate the chemical composition of the TMR (Table 1).
Individual and bulk-tank milk samples were taken once a week for a period of
1 month, from mid-November to mid-December 2013. A total of 88
samples were collected. The selected sampling day was fixed for both farms
throughout the experimental period. The samples were taken in the morning
and were analyzed in the afternoon. The individual milk samples were taken
from a container connected to the pipeline system as soon as the cow
stopped milking. All individual samples were labeled with the same ear tag
number of the cow and were kept in a refrigerator (4
A MasterPro LM2 (Milkotester Ltd., Belovo, Bulgaria) was used to measure protein, fat, freezing point, density, solid nonfat, lactose, salts, added water, conductivity, and pH in milk samples. The principle of such instruments is the measurement of turbidity, or light scattering, caused by fat globules in milk. All samples were analyzed in triplicate.
The concentration of Zn, Cu, Pb, and Ba in the bulk and individual milk samples
was determined by a microwave plasma–atomic emission spectrometer (MP-AES; Agilent
4100, Agilent Technologies, Santa Clara, USA) after mineralization.
Briefly, milk samples (2 mL) were treated with 5 %
Each metal was calibrated against a known set of standardized concentrations at the optimal wavelengths (nm). The instrument and metal parameters are listed in Tables 2 and 3.
MP-AES configuration and operating conditions.
Figures of merit from the MP-AES method representing the wavelength of
detection, correlation coefficient (
Milk proximate data were analyzed using a repeated measurement analysis
procedure with farm and time as the main effects. Farm, time,
and time–farm combinations were included in the model. For metal analysis, a
factorial analysis of variance (ANOVA) model with second-order interaction
was applied, considering farm and time as fixed factors; the Student–Newman–Keuls (SNK) test for
multiple comparisons was applied. The effect of replicate samples was tested
separately, was not significant for any of the examined parameters, and
was omitted from the model. Principal component analysis and Pearson
correlations were conducted on all samples using XLSTAT v.2014.4.04
(
Recently, interest has been renewed in the utilization of fresh forage for dairy cows. Where dairying relies on the sole use of a TMR for feeding dairy cows, this interest in fresh forage may be justified when feed costs increase along with greater volatility in the price of conventional feeds (Menoza et al., 2016). The hydroponic fodder system is an ideal solution in Malta, providing a large amount of fresh fodder every day with minimal nutritional input, which efficiently encourages rapid growth.
In fact, it is ideal for areas where it is not possible to grow fresh fodder in a field over a very short period of time all year round. Studies have shown that this system may help the dairy cattle by increasing the fat percentage and health benefits of the herd (Naik et al., 2015).
This study was carried out to investigate whether the consumption of
hydroponic fodder affects milk quality. To determine whether the sampled
cows represented the herd, the bulk tank was sampled alongside the
individual cows. The results of the proximate analysis of the average milk
values of the 10 cows and the bulk tank (Table 4) did not show significant
variations (
The hydroponic fodder system produces fresh daily forage with a high nutritional value. Barley is placed in growing trays without any type of medium and allowed to grow over a period of 7 d. Germination starts within 24 h with a high germination rate of 85 % or better depending on how efficiently the temperature and light are maintained inside the system. Artificial light is used in this system to maximize growth, and special wavelength lights are strategically positioned to illuminate the seed beds for maximum growth. At the end of each cycle, hydroponic grass yields a constant layer of sproutings and densely packed roots. In 7 d the fodder crops, typically barley, reach a height of around 15–20 cm. The dairy cows consume the entire material without any waste because it is all edible and fresh. Hydroponic fodder requires no additional nutrients because it uses the resources and energy from the seed itself. This system requires a regular single-phase power supply, a potable water supply, and a low operating cost with minimum labor requirements. It only takes around 1 h of work per day to clean the trays, reseed, and harvest. With this system fresh grass is harvested daily all year round regardless of the weather. Setting up this system is more sustainable than importing hay from other countries as the cost of transport is expensive and the feed quality is inferior. On the other hand, hydroponic fodder is cheaper, resulting in improved milk quality (Carrillo et al., 2013). The cost of a bale of hay is much higher than cultivating fresh fodder each day. Some studies have showed controversial results with this system, and the relationship between the hydroponic system and milk quality is not always positive. Saidi and Omar (2015) observed no difference in the composition of milk from ewes fed with hydroponic barley. In the present work, carried out on cows, the average milk fat content in GZ was 4 % and that in MT for the 4-week period was 3.5 % (Table 4). Analysis of variance revealed the following results: GZ milk had a higher fat content and a higher pH. Fat is a main component in milk and has important nutritional and technological properties. About 98 % of milk fat is represented in the form of triglycerides, which are essentially esters of glycerol and fatty acid. The properties of milk fat are to a large extent determined by the fatty acid composition (Larsen et al., 2014).
Effect of feeding system on milk chemical composition (average of individual cows with bulk-tank values in brackets).
Ns: not significant
Milk mineral content in two different farms during the observed
period. Bold values represent a correlation between parameters at
The fatty acids in milk originate from different sources: de novo synthesis in the
mammary gland, body fat reserve, and fatty acid produced from bacteria in the
rumen as recently reviewed (Hanuš, et al., 2018). Young fresh fodder
contains more fatty acids than other forages, which are harvested when they
mature (Elgersma et al., 2015), and contains fatty acids that improve the
quality of the milk. It is hypothesized that the transcription of enzymes
involved in milk fat synthesis is affected by grazing fresh forage
containing large concentrations of polyunsaturated fatty acids (PUFAs) (Wiking et al., 2010). The high fat
content found in the present paper is likely due to a major PUFA content in
feed (such as silage and hydroponic fodder) not consumed in the MT farm. The
milk protein content of cows in both farms was quite similar (
Solid nonfat (SNF) correlated positively with density, protein, and
conductivity but negatively with added water (
“Essential minerals” (Ca, Fe, Zn, Cu, and Se) are those required for the complete life cycle of an organism, the absence or insufficiency of which in the human diet could result in modifications of metabolic functions and some diseases. However, some essential metals become “toxic” when their concentration is high, especially at levels exceeding 40- to 200-fold (Rao, 2005). Two typical toxic metals are Cd and Pb. Several recent investigations show that the presence of toxic metals in foods is observed worldwide (Tunegovà et al., 2016). Studies show that high levels of Cd and Pb in milk are related to external sources and environmental pollution (Sola-Larrañaga and Navarro-Blasco, 2009; Malhat et al., 2012). Öhrvik et al. (2006) reported that developmental problems observed in mice sucklings are due to the dysfunctional effects of high levels of Cd on the mammary glands. The term “heavy metals” poorly describes the nature of metals (Duffus, 2002). In the present study, the term “toxic metals” refers to Ba and Pb, while “essential metals” refer to copper (Cu) and zinc (Zn).
Milk mineral content in two different farms during the observed period.
Ns: not significant.
Results on mineral content are presented in Table 6. The GZ farm exhibited
higher Pb and Cu content than MT. Lead concentrations in both farms exceed
the maximum limit of 0.02 mg kg
The mean Cu contents were 0.70 and 0.75 mg L
Concerning Zn concentration, the MT farm showed higher results than GZ,
though these were generally lower than those reported in the literature.
Reference values of milk concentrations of Zn range from 2 to 6 mg L
In conclusion, the use of hydroponic culture modified the chemical composition of milk with respect to fat content, which is a desirable parameter. Moreover, principal component analysis revealed that with respect to proximate analysis, the quality of milk from cows from the GZ farm was superior to that of cows from the MT farm. The difference between minerals in the two farms may not be easily interpreted as the environment plays an important role, particularly with contaminants in the air, water, and soil.
Further studies are needed to establish the effects of long-term feeding with different types of hydroponic fodder and to investigate the effects of these hydroponic fodders on the productive and reproductive performance of dairy cows. Further studies may be directed towards the development of feeding strategies with respect to the inclusion of hydroponic fodder under different agroclimatic conditions.
Data are available from the corresponding author upon request.
EA, AA, and GP designed the experiment; AA performed the experiment, and EA and AA performed the lab analysis; EA and GP analyzed the data; GP and EA prepared the paper, and AA contributed to the paper.
The authors declare that they have no conflict of interest.
This paper was edited by Manfred Mielenz and reviewed by three anonymous referees.