This study aimed to evaluate the effect of concentrate-based
feeding (CF) and artificial pasture-based grazing (APG) management systems
on milk yield, fatty acids, nutritional indices, and milk physicochemical
characteristics of Awassi ewes. The research involved 300 heads of Awassi
ewes, which were divided into two groups. Awassi sheep were managed in a CF
and APG system to test the milk yield characteristics. The results showed a
significant (
Sheep production has a significant economic impact on the rural areas across Turkey, there are 45 177 690 heads of dual-purpose ewes, and they produce approximately 1 143 762 tons of milk (4.92 %) annually (TURSTAT, 2022). The major proportion of sheep milk is converted into high-value products like yogurt, butter, Ezine and Divle Obruk cheeses, and different types of Tulum, Van Otlu, and Mihaliç cheeses. Therefore, knowledge of the chemical composition, physicochemical properties, and nutritional value of sheep's milk is important. The quality and quantity of milk produced by farmers can be increased by providing a better management system, improved genetics, a hygienic environment, and better pasture conditions for grazing.
The dairy industry and consumers prefer high-quality milk. Moreover, in recent years, there has been an increasing interest of consumers in sheep and goat milk and products in terms of nature, nutrition, and health. The production of high-quality dairy products for the dairy industry is only possible by increasing the quality and quantity of milk. The quality of sheep milk is affected by genetic (breed) and environmental factors such as feeding, rearing system, milking method, and season. Sobrino et al. (2018) reported that milk quality evaluation is important not only for cheese production, but also for other dairy products. The composition and physicochemical characteristics of goat and sheep milk are essential for the successful development of the dairy goat and sheep industries as well as for the marketing of the products (Park et al., 2007). The chemical composition and physicochemical properties of the milk determine the quality of yogurt, cheese, and other products. The properties of milk depend on numerous factors. The lactation stage, nutrition, farm conditions, and all meteorological factors affect the milk yield, composition, and quality of milk (Kuchtik et al., 2017; Gonzalez-Ronquillo et al., 2021). The farming system in which sheep are raised can affect the milk properties depending on the intensive or semi-intensive production system. It is established that grazing can improve the fatty acid composition of milk (Kasapidou et al., 2021). Therefore, pasture-based feeding strategies could improve the fatty acid composition and the nutritional properties of sheep dairy products. However, it is believed that adequate and balanced fat consumption is necessary, and therefore fatty acids should be part of the diet in a proper ratio to provide the contents required by the body. Moreover, dietary fats can play positive or negative roles in the prevention and treatment of diseases (Chen and Liu 2020). The milk fatty acid composition and nutritional value were significantly improved in milk from farms using the semi-intensive production system, and this favorable effect was attributed to the inclusion of pasture in the sheep's diet. In nature, fatty acids occur in the form of mixtures of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs), so their nutritional and/or medicinal values must be determined. Furthermore, the fatty acid composition in the milk is highly influenced by external factors, including animal nutrition, farming management, and pasture composition.
The objective of this study was to evaluate the milk yield, chemical composition, physicochemical properties, fatty acid composition, and nutritional value of Awassi sheep milk produced in different management systems.
The study was carried out on a private dairy sheep farm located in the
Central Anatolia region, Turkey (37
Lambs were kept in cages with their mothers for the first 5 d after lambing. After the first week, lamb starter feed and alfalfa rough were given to the lamb ad libitum. Lambs were weaned at approximately 45 d of age. The milk control interval was determined to be 30 d. Ewes were dried off when milk yield decreased below 100 mL.
In this experiment, 300 heads of ewes between the ages of 2 and 6 were
selected from 2000 heads of sheep that gave birth in the same month and were
divided into two groups: concentrate-based feeding (CF) and artificial pasture-based grazing (APG). The first group of animals was kept in
permanent housing with no access to artificial pasture and was fed with a total mixed ratio (TMR) consisting of 0.965 kg d
The ewes in the APG group did not have any additional feeding; however, they were grazed for at least 8 h of the day on artificial pastures which had
separate electric fences. The pasture area, which was established as
approximately 30 ha in 2019, was divided equally into six parcels of 5 ha with electric fences. The grazing process for ewes was started when the plant
height of the species in the pasture reached approximately 15–20 cm. The
samples taken from the wire cages and placed in the pasture plots just before grazing with the sheep were divided by species, and it was determined that the botanic composition in the grazing season consisted of 85 % of grasses
and 15 % of legumes. The stocking rate was 24 ewes ha
Sample collection from pasture.
An area of 30 ha, which was previously used for growing field crops, was
planned for an artificial pasture establishment to be grazed with sheep. The
pasture was set up with a mixture of six different perennial species, including perennial ryegrass (
The CF and APG ewes were milked twice a day with an automatic milking system, and milk yields were obtained from the system at the end of lactation. The lambs suckled their mothers for 45 d, and then the sheep were milked. During this period, the lambs were separated 12 h before the milk control from their mothers, and ewes were directed to milking. The Fleishmann method was used to obtain the lactation milk yield for each ewe (Barillet et al., 1992). Lactation length was calculated as the date of dry-off and time of birth.
Milk samples of ewes from CF and APG ewes were collected individually during milking in 50 mL plastic screw-capped flasks, placed in isothermal containers with ice packs, and transported to the laboratory. For the chemical analysis of milk, a total of 150 individual samples was taken from the sheep once in the middle of lactation (early June) with a milk collection container mounted on the milking system. Milk composition (fat, protein, lactose, and total solid content) was determined by infrared analysis (FTIR interferometer) using a Milkana® Express Plus Analyzer. Somatic cell count (SCC) was determined with a Milkana® Somatic Scan Analyzer, and the obtained data were log-transformed to normalize the distribution. A pH meter equipped with a penetrating electrode and a thermometer (Hanna Instruments, HI–9025) was used to determine pH immediately after milking. It was calibrated with standard buffer solutions at pH 4.0 and 7.0 according to the manufacturer's instructions.
For the analysis of milk fatty acids, a total of 50 ewes' milk samples were collected in early June and kept at
The milk fatty acid profile was used to calculate the following indices related to healthy fat consumption. In addition, all nutritional indices were used to assess the nutritional value of milk and other dairy products in various studies. The hypocholesterolemic / hypercholesterolemic fatty acid ratio (h / H) ratio was calculated according to the formula reported by Chen and Liu (2020). The atherogenicity (AI) and thrombogenicity (TI) indices were calculated according to the following formulae offered by Ulbricht and Southgate (1991). The health-promoting index (HPI) was recommended by Chen et al. (2004).
Statistical analysis was performed using a one-way analysis of variance (ANOVA) with SPSS software package release 22.0 (SPSS, 2016). An analysis of variance was carried out considering the production system to have fixed effects. The results were
significant when the
Awassi sheep were managed on CF and APG production systems to compare the
milk yield. The lactation curves for the management systems are presented in Fig. 1, and the mean values of milk yield and lactation length of the Awassi ewes are shown in Table 1. The results obtained after feeding showed that there was a significant (
The abovementioned studies' results are in agreement with our results: the animals managed on grazing have their milk yield and lactation length significantly improved over the non-grazed intensively managed animals.
Milk yield and lactation length of the Awassi ewes of the different management systems.
ns: nonsignificant,
Lactation curves of the ewes' different management systems.
Table 2 shows the means of milk chemical composition and some milk quality
parameters. Milk from the CF and APG ewes had no significant difference
(
Milk chemical composition of the Awassi ewes in the CF and APG systems.
Electrical conductivity (EC), milk somatic cell count, and pH of milk did not differ significantly (
Kuleile et al. (2021) studied the performance of lactating ewes in four groups: control group, T1 forage only, T2 forage with concentrate, and T3 forage
with urea molasses and concentrate. The T1 group showed better milk than
the other groups, and the T3 group showed better amounts of milk protein, density, and solids not fact (SNF) than the control group and T2. Obeidat et al. (2019) reported similar results saying that the animals with supplementation showed better levels of SNF, protein, and milk butter fat than the control group. The T1 group fed only on
forage showed the lowest level of milk fat percentage. The dietary treatment
of the T3 group with concentrated urea molasses had an effect on milk which
caused higher levels of milk protein, density, SNF, and lactose content.
These results suggest that if the animals are supplemented with high
nutrients along with forage food, the milk composition of ewe's milk will be further improved. However, our study did not show any significant difference in milk composition, which indicates that the addition of supplementing
high-nutrient feed along with grazing can provide increased protein, SNF,
and butter fat. Daş et al. (2022) Awassi sheep overall mean fat, protein,
and lactose ratios were determined to be 6.27
The acidity of the milk indicates the freshness and withstanding ability of milk against heating. When milk is expressed, it shows a slightly acidic reaction. The natural acidity of milk is primarily composed of casein, phosphate, citrates, second-degree albumin, globulin, and carbon dioxide. Since the natural acidity of milk is related to the substances in its composition, the acidity levels of different compositions will also be different. For example, the acidity of sheep and buffalo milk, which has a high protein content, is higher than that of cow's milk.
Daş et al. (2022) measured pH on days 45, 75, 105, and 135, with values of 6.7, 6.55, 6.02, and 5.89. The pH values showed a decreasing trend
in value with the number of days passing, which is different from our findings. The pH value measured in the milk of Awassi sheep shows similarities to the Park et al. (2007) pH, 6.51–6.85, Sobrino et al. (2018) pH, 6.61, Gelasakis et al. (2018) pH, 6
Values for the fatty acid composition of milk are presented in Table 3.
Sheep milk fatty acid composition is given in Table 3. Palmitic (C16:0),
myristic (C14:0), stearic (C18:0), capric (C10:0), and lauric (C12:0) acids were the major saturated fatty acids in milk from both production systems. The levels
of linolenic acid (C18:2 n-6) were found to differ statistically (
Daş et al. (2022) measured the composition of fatty acids in Awassi sheep
under semi-intensive conditions, and the fatty acid records in their study showed higher values. However, the values of palmitic acid (C16:0) and stearic acid (C18:0) were higher in our study. Yakan et al. (2019) recorded a total of 22 fatty acids (from C4:0 to C24:0) for both feeding strategies, and a significant difference was seen between the short-chain fatty acids (from C4:0 to C10:0) in the feeding strategies. Five fatty acids (C10:0,
C14:0, C16:0, C18:0, and C18:1) accounted for
Fatty acid composition of the Awassi ewes in the CF and APG management systems.
The milk fatty acid composition profile for CF and APG for most of the fatty
acids was not very different in both groups, but in the case of C4:0, C6:0,
C16:0, C16:1, and C18:0, significant variation among CF and APG was seen. Five fatty acids (C10:0, C14:0, C16:0, C18:0, and C18:1) account for
Bodnar et al. (2021) reported that, while grazing, the amounts of linolenic (C18:3), stearic (C18:0), caprylic (C8:0), oleic (c9C18:1), caproic (C6:0), romanic (c9t11C18:2), butyric (C4:0), and vaccenic (t11C18:1) acids were significantly increased. However, the amounts of palmitoleic (C16:1), myristoleic (C14:1), lauric (C12:0), palmitic (C16:0), capric (C10:0), and linoleic (C18:2) acids were decreased significantly by grazing.
The effect of the production system on the lipid quality of milk is given in
Table 4. The effect of the production system on the SFAs, MUFAs, and PUFAs was nonsignificant (
Bodnar et al. (2021) reported that grazing increased the total number of n-3 PUFAs significantly, while on the other hand the number of medium-chain fatty acids (MCFAs), odd-chain fatty acids (OCFAs), n-6 PUFAs, PUFAs, and n-6/n-3 were significantly decreased by grazing in the milk and cheese of goats.
Daş et al. (2022) recorded higher values of SFAs in Awassi sheep; however, the values of MUFAs, PUFAs, and UFAs were higher in our study than their findings. De Renobales et al. (2012) recorded higher numbers of total unsaturated
fatty acids (PUFAs) and unsaturated FAs in the sheep with more grazing time and less hay than the other group, who had less grazing time and more hay. Group 1 with more grazing time reported more amounts of c9t11, vaccenic acids, CLA, and short- and medium-chain fatty acids than the other group, with the concentration being 3.4 more for these FA folds than the control group. In the FAs detected, the saturated FAs had 75 %, with most of them being short-chain fatty acids and stearic acid and not
atherogenic acids. The sheep group with more grazing time reported 56 % more non-atherogenic FAs than the control group, which had 49 % of these FAs.
Bonanno et al. (2016) studied the effect of grazing the Comisana breed with
ryegrass for 8 and 22 h d
According to Papaloukas et al. (2016), the available pastures in semi-extensive farming systems can contribute to the production of high-quality milk. The significant variability was mostly attributed to the diet. Specifically, the pasture-based diet during the months of spring and especially summer resulted in the amelioration of important ratios, indices, and groups of FAs in sheep's milk. Muldasheva et al. (2021) showed that milk from the semi-intensive production system had significantly improved fatty acid composition and lipid quality nutritional indices in relation to milk produced on intensive farms. Differences in the composition of fatty acids and the lipid quality indices were attributed to the inclusion of pasture in the sheep diet.
Table 4 gives the sums, ratios, and index values obtained from fatty acids. The h / H ratio, TI, and n3/n6 were affected significantly (
Milk nutritional indices of the Awassi ewes in the CF and APG management systems.
The h / H ratio was significantly higher (
The lactation milk yield and lactation length of sheep managed based on artificial pasture were found to be better than the feeding system based on concentrated feed. However, in this study, it was determined that there was no significant difference between the two management systems in terms of the chemical characteristics and quality of the milk of Awassi sheep. Although milk yield, chemical composition and quality characteristics of milk, and nutritional value are mostly influenced by the feeding and rearing systems of animals, factors such as breed, age, and season are also important. More studies are needed to reveal the seasonal and economic analysis and efficiency of two management systems in different seasons on milk composition, milk production, fatty acid, and milk nutrient content.
The data are available from the corresponding author upon request.
AC and MA conceptualized the hypotheses and design of the study. MMT, BY, and MUH performed the measurements. AC, MUH, and BY analyzed the data. AC and MUH wrote the manuscript draft. AC, MA, MUH, and BY reviewed and edited the manuscript.
The contact author has declared that none of the authors has any competing interests.
No ethical approval is required, because no significant impairment to the well-being or general condition of the animals has been made.
Publisher’s note: Copernicus Publications remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
This research has been supported by the Scientific and Technological Research Council of Turkey (grant no. 3190550).
This paper was edited by Steffen Maak and reviewed by two anonymous referees.