Milk Performance and Blood Biochemical Indicators of Dairy Goats Fed with Black Oat Supplements

Abstract

This research determined the milk performance and milk and blood biochemical indicators of dairy goats fed with black oat supplements. The experiment was conducted on 20 French Alpine goats on the 48th day of lactation, divided into two groups of 10 goats each (initial body weights (BW) of 53.90 and 52.15 kg). The research lasted for 30 days, and the monitoring of production properties and blood sampling were carried out on the 1st, 15th, and 30th days of the research. Goats in the BOG group were fed a diet in which yellow oats were gradually replaced with black oats, whereas goats in the COG group received a diet containing yellow oats (CP: 143.64 vs. 150.40 g/kg DM; EE: 48.60 vs. 48.80 g/kg DM; NEL: 7.18 vs. 7.19 MJ/kg DM). These values were subjected to repeated-measures analysis using the PROC MIXED procedure and were further analyzed using Tukey’s post hoc test. Compared with the COG group, no significant differences were observed in the BOG group for the production performance of the goats, except for a slightly increased milk yield (1264.94 vs. 1542.10 g/day, p = 0.098) and reduced concentrations of urea and globulin in the milk of the BOG group (7.90 vs. 7.05 mmol/L, p = 0.081; 5.16 vs. 3.96 g/L, p = 0.091). In the blood of BOG goats, a significantly lower urea concentration was detected (8.75 vs. 7.05 mmol/L, p = 0.020). However, compared with the COG group, goats in the BOG group showed a slight increase (p > 0.05) in protein fractions and a decrease in lipid-related indicators in the blood. These findings confirm the moderate benefit of black oats as a dietary supplement in feed for lactating goats.

1. Introduction

With the restriction on antibiotic use in animal feed, the role of biostimulants as growth promoters has become more prominent in ruminant production [1]. While in other parts of the world, the reduction in the use of antibiotics in agriculture, including decreased antibiotic use in food-producing animals, has been associated with a reduction in antimicrobial resistance in animals, it also raises considerable concerns [2,3]. In the study by Tang et al. [4], a meta-analysis of published research on restricting the use of antibiotics in food-producing animals was performed, and the authors concluded that numerous studies have found that restricting the use of antibiotics in food for animals reduces the presence of antibiotic-resistant bacteria. Also, the authors suggest that the broad implementation of strategies to reduce the use of antibiotics requires a balanced consideration of the benefits of reducing antibiotic resistance in animals as well as in humans [4].

Feedstuffs rich in natural biostimulants are used for the balancing of meals, and consumption of such feedstuffs has a positive influence on animals, including antimicrobial, antioxidant, anti-inflammatory, and antitumor effects [5]. Many forages, especially pigmented feed and agro-industrial by-products, contain various biostimulants recognized as beneficial in animal nutrition [6]. Among these compounds, dietary polyphenols are abundant in cereals, especially in whole grains [7]. Polyphenols do not directly contribute to the nutritional value of feed but are widely distributed throughout plant tissues and primarily include phenolic acids, flavonoids, and lignans. Their biological activity and risk–benefit profile depend on their chemical diversity, source, bioavailability, and potential dual effects in animal metabolism [8].

Yellow oats are recognized for their unique protein composition and high nutritional value. Unlike most cereals, whose proteins are predominantly prolamins, oat proteins consist mainly of globulins, resulting in a more balanced amino acid profile [9]. Oats are classified as whole grains and are particularly rich in soluble fiber (β-glucan), lipids, protein, and specific micronutrients [10]. Oats are a unique source of polyphenols (avenanthramides). In the diet of ruminants, oats usually comprise up to 20% [11].

Advances in plant breeding and food processing technologies that preserve the health-promoting properties of oats while expanding their application have stimulated research into different oat genotypes and their functional potential [12,13]. Oats comprise numerous varieties (genotypes), among which black oats warrant particular attention [14,15]. According to Fontaneli et al. [16], black oats can be cultivated either exclusively for forage or for both forage and grain production. Black oats are rich in polyphenols and phenolic acids [17], which exhibit anti-inflammatory, antiproliferative, and antipruritic activities [18].

In addition, Waqas et al. [19] emphasized that efforts in breeding ruminants for meat or milk production should focus on reducing greenhouse gas emissions by optimizing ruminal fermentation processes and improving rumen microflora composition. Diets rich in polyphenols may contribute to this objective. Although several studies have examined the use of black oats for livestock grazing or as a component of silage, relatively few have investigated the use of black oat grain in ruminant nutrition [20,21,22]. Available studies have primarily focused on grazing ruminants in Central and North America (e.g., Mexico and Brazil) [23,24,25,26] or on black oats included in silage [24,27,28]. These studies reported positive effects of black oats on production performance and the economic efficiency of ruminant production.

However, to the best of our knowledge, no studies available in scientific databases have evaluated the use of black oat grain in goat feeding. Therefore, the hypothesis of this study was that replacing yellow oats with black oats in the diet of dairy goats during early lactation would positively affect milk production and selected blood biochemical indicators. Accordingly, the objective of this study was to evaluate milk performance, milk biochemical parameters, and blood metabolic indicators in dairy goats fed diets supplemented with black oats.

2. Materials and Methods

2.1. Experimental Design and BW Analysis

The study was carried out on 20 French Alpine goats at the Djurković dairy goat farm, located in Osijek-Baranya County, Croatia. The experiment was conducted in 2022. The selected goats were in the 48th day of lactation. The preparatory period lasted for 7 days so that the goats could adjust to the new composition of the diet. The research lasted for 30 days. Weighing of the goats (initial BW 53.90 ± 6.09 and 52.15 ± 6.42 kg) and acquiring milk (initial milk production during morning milking: 1338 ± 682.02 and 1436 ± 513.70 g/L) and blood samples were carried out on the 1st, 15th, and 30th day of the experiment (48th, 63th, and 78th days of lactation). The goats were divided into two groups, with 10 goats in each group. The groups were kept in separate pens (5 m × 4 m). The goats were weighed with a livestock scale (Kern EOS 150K50XL animal platform scale (Kern & Sohn, Balingen, Germany)). The selected goats were, on average, 5 years old and in the fourth lactation. All animals were treated with an anthelmintic, cleared of parasites, were in good health, and exhibited an appropriate body condition. They were chosen from a herd consisting of 50 goats. The goats were housed in a barn, and milking was performed mechanically in a separate milking parlor. Body condition score (BCS) was observed on a 1- to 5-point scale, as described by Santucci and Maestrini [29], where the scale from 1 (thin) to 5 (obese) was divided in 0.25 intervals. All staff members handling live goats received appropriate education and training.

2.2. Diet Composition and Feed Analysis

Goats were fed a feed mixture (1.2 kg/day), the composition of which is overviewed in

Table 1. Composition and nutritional characteristics of the feed mixture and meadow hay fed to goats.

Ingredient (% DM)	Group		Black Oats	Hay
	COG	BOG
	Ingredients composition
Corn	42.30	42.30
Oats	15.00	-
Black oats	-	15.00
Barley	19.00	19.00
Soybean meal	9.00	9.00
Soybean, toasted	11.00	11.00
Limestone	0.30	0.30
Cattle salt	0.40	0.40
Mineral premix *	3.00	3.00
Chemical composition (g/kg DM)
Dry matter	948.80	951.00	952.00	951.15
Crude proteins	143.64	150.40	84.50	75.90
Ether extract	48.60	48.80	47.50	11.20
Crude fiber	50.18	50.50	101.10	328.60
Ash	65.04	65.10	28.60	47.40
NEL, MJ/kg	7.18	7.19	-	4.45
Polyphenols (total), mg gallic acid equivalents (GAE)/kg	1582.61	2054.63	1416.52	5650.61

COG: control oats, BOG: black oats; DM: dry matter; NEL: net energy for milk production. * Mineral–vitamin premix for goats: 21% calcium, 6% sodium, 5% phosphorus, 5% magnesium, 1,200,000 IU/kg vitamin A, 140,000 IU/kg vitamin D3, 6500 mg/kg zinc oxide, 3500 mg/kg vitamin E, 1500 mg/kg zinc (in the form of chelates), 600 mg/kg iron sulphate monohydrate, 500 mg/kg copper (in the form of chelates), 490 mg/kg copper sulphate pentahydrate, 60 mg/kg iodine in the form of anhydrous calcium iodate, 50 mg/kg selenium selenite, 40 mg/kg cobalt carbonate monohydrate, and 5 mg/kg manganese sulphate pentahydrate.

, according to NRC [30]. The goats’ daily meal consisted of the feed mixture and hay. The feed mixture was given to the goats twice a day during milking, individually, in separate feeding troughs. The goats also had ad libitum access to meadow hay, livestock salt, and water. The dietary ratio of roughage to concentrate was maintained at 60:40. In the control group of goats (COG), conventional yellow oats were used in the feed mixture at a level of 15% of the feed dry matter, whereas in the experimental group (BOG), it was completely replaced with black oats.

Samples of the feed mixtures were taken immediately after mixing and analyzed at the Central Analytical Agrobiotechnical Unit of the Faculty of Agrobiotechnical Sciences in Osijek. Both the feed mixture and hay were dehydrated and finely ground using an ultra-centrifugal mill free of heavy metals (Microtron MB 550; Kinematica, Luzern, Switzerland). Feed composition was determined using standard methods of AOAC [31]. Total polyphenols were extracted and quantified following the procedures outlined by Jakobek et al. [32], using the specified equipment (Shimadzu UV-1280 spectrophotometer (Shimadzu Europe GmbH, Duisburg, Germany)). Three separate extracts of each feed sample were prepared, and the total polyphenol content was expressed as mg of gallic acid equivalents (GAE) per kg of sample. Analyses were performed using a Shimadzu UV-1280 spectrophotometer (Shimadzu Europe GmbH), as detailed by Jakobek et al. [32].

2.3. Milk Sampling and Analysis

In this study, milk sampling was carried out on the 1st, 15th, and 30th day during the morning machine milking of the goats (7.00 a.m.). Three samples of milk were acquired in 30 mL bottles and cooled to 4 °C. Goat milking was performed manually, and milk samples were collected immediately after milking from each goat individually on the same day, in the morning. Milk samples were transported to the laboratory, where they were analyzed the following morning for chemical analysis, while samples intended for biochemical analysis were analyzed immediately after sampling and transported to the laboratory. The reagent (Azidiol) was present only in bottles intended for basic chemical analysis of milk. No cases of mastitis were observed in any of the goats throughout the experiment, as assessed by forestripping prior to each milk sampling. The chemical composition of the milk was obtained on the milkoScan FT 6000 analyzer (Foss Electric, Hillerød, Denmark) by following the HRN ISO 9622:2017 [33]. The following equation was used to calculate fat-corrected milk at 3.5% (FCM, kg/day; Pulina et al. [34]):

FCM = milk yield × (0.634 + 0.1046 × fat)

(1)

Somatic cell counts (SCC) were determined using a Fossomatic 5000 Analyzer (Foss Electric) based on the fluoro-opto-electronic method (HRN ISO 13366-2/Ispr.1:2007). Following the methods of Wiggans and Shook [35], the results were converted to logarithmic values using the following equation:

SCC = 3 + log2(SCC/100 000)

(2)

To determine biochemical indicators, fresh goat milk was centrifuged at 5000× g for 30 min to separate the fat (ROTOFIX 32A, Hettich GmbH & Co. KG, Tuttlingen, Germany), and the resulting milk plasma was analyzed.

Biochemical parameters, including Ca, inorganic P, Mg, AST (aspartate aminotransferase), ALT (alanine aminotransferase), GGT (γ-glutamyl transferase), ALP (alkaline phosphatase), urea, ALB (albumins), GLOB (globulins), and TP (total proteins), were measured using an Olympus AU 400 biochemical analyzer (Olympus, Tokyo Japan). Glutathione peroxidase (GPx) activity in milk was determined using the Ransel^® kit (Randox, Crumlin, UK).

2.4. Blood Sampling and Analysis

Goat blood samples were collected from vein jugulars in sterile vacuum tubes (Venoject^®, Leuven, Belgium) without EDTA and were centrifuged at 1609.92× g for 10 min using a ROTOFIX 32A centrifuge (Hettich GmbH & Co. KG, Tuttlingen, Germany) immediately after the completion of milking. The collected goat serum samples were analyzed using the Olympus AU400 biochemical analyzer (Olympus, Japan). In serum, the determined biochemical parameters were minerals, i.e., calcium, inorganic phosphorus, and magnesium; metabolites, i.e., urea; GUK (glucose); PROT (total proteins); ALB (albumin); CHOL (cholesterol); LDL-CHOL (low density lipoprotein); HDL-CHOL (high density lipoprotein); TGC (triglycerides); BHB (β-hydroxybutyrate); NEFA (non-esterified fatty acids); and enzyme activities, i.e., ALT (alanine aminotransferase), AST (aspartate aminotransferase), GGT (γ-glutamyl transferase), and CK (creatine kinase), all determined by using Olympus System reagents (Olympus Diagnostic GmbH, Dublin, Ireland). Globulin concentration (GLOB) was calculated as the difference between TP and ALB concentrations. The activity of glutathione peroxidase (GPx) in goat serum was assessed using the Ransel^® kit (Randox, UK) on the Olympus AU 400 analyzer (Olympus, Tokyo, Japan).

2.5. Statistical Analysis

Descriptive statistics for productive performance, milk quality, and milk and blood biochemical parameters were computed for each goat at every sampling point. These values were then subjected to a repeated-measure analysis using PROC MIXED (SAS 9.4 [36]), by applying the following model: Y_ijk = μ + d_i + h_ij + w_k + dw_ik + e_ijk, where μ means overall mean, d_i means fixed effect of diet (i = COG, BOG), h_ij means goats fed specific diets (j = COG, BOG), w_k means fixed effect of sampling time during lactation (k = 1–3), d_wik means interaction between diet and sampling time (diet × sampling time), and e_ijk means residual error. Mean values were analyzed using Tukey’s significant difference test, with p-values below 0.05 indicating statistically significant differences.

3. Results

The data presented in

Table 2. Production performances, milk quality, and biochemical indicators in goat milk during investigation.

	Diets		SEM	p Value
	COG	BOG		Diet	P	D × P
Live BW, kg	52.79	51.09	0.97	0.314	0.353	0.929
BCS, point	2.17	2.43	0.10	0.205	0.493	0.694
Milk yield, g/day	1264.94	1542.10	93.18	0.098	0.837	0.649
Fat, %	3.32	3.40	0.18	0.718	0.906	0.574
Protein, %	2.91	2.84	0.06	0.572	0.976	0.875
Lactose, %	4.45	4.38	0.03	0.245	0.169	0.661
Log SCC, log	6.13	6.14	0.09	0.929	0.834	0.533
Log CFU, log	3.97	3.96	0.12	0.980	0.725	0.365
Urea, mmol/L	7.90	7.05	0.27	0.081	0.011	0.149
Ca, mmol/L	34.82	37.90	2.18	0.497	0.418	0.381
P, mmol/L	24.16	24.03	0.82	0.939	0.757	0.525
TP, g/L	24.18	23.58	0.78	0.715	0.784	0.512
ALB, g/L	19.02	19.82	0.61	0.530	0.504	0.337
GLOB, g/L	5.16	3.96	0.32	0.091	0.936	0.869
AST, U/L	51.90	79.23	10.56	0.202	0.355	0.116
ALT, U/L	58.87	64.12	9.54	0.769	0.823	0.524
ALP, U/L	66.20	49.24	10.26	0.370	0.315	0.859
GGT, U/L	421.90	414.55	19.90	0.933	0.105	0.576
GPx, U/L	45.96	43.67	3.03	0.670	0.001	0.765

COG: control oat group; BOG: black oat group; D: diet; P: sampling time; D × P: interaction (diet × sampling time); SEM: standard error of mean; BW: body weight; BCS: body condition score; SCC: somatic cells count; CFU: colony-forming unit; TP: total proteins; ALB: albumins; GLOB: globulins; AST: aspartate aminotransferase; ALT: alanine aminotransferase; ALP: alkaline phosphatase; GGT: γ-glutamyl transferase; GPx: glutathione peroxidase.

refer to the BW and body condition scores (BCS) of the goats, from which it is evident that there were no significant differences between feeding treatments (p = 0.314 and p = 0.205). Data regarding milk yield showed a slight increase; however, no significant differences were observed between the BOG and COG groups (p = 0.098). Milk quality indicators and concentrations of biochemical indicators in milk did not differ significantly, except for slightly decreased urea and globulin concentrations in BOG milk compared to those for COG milk (p = 0.081 and p = 0.091). The conducted experiment did not result in significant changes in the production and quality of milk, except for the slightly increased amount of milk (1264.94:1542.10 g/day; p = 0.098) and slightly decreased concentrations of urea (7.90:7.05 mmol/L, p = 0.081) and globulin (5.16:3.96 g/L, p = 0.091) in milk (Table 2). A significant effect of sampling time on GPx activity (p = 0.001) in the milk of the studied goats was also determined.

The metabolic profile, assessed through blood biochemical indicators (metabolites, minerals, and enzyme activities), is presented in

Table 3. Concentrations of metabolites in the blood of goats during investigation.

	Diets		SEM	p Value
	COG	BOG		D	P	D × P
Urea, mmol/L	8.75	7.03	0.32	0.007	0.020	0.184
GUK, mmol/L	4.40	4.77	0.15	0.223	0.121	0.458
TP, g/L	66.15	69.62	1.68	0.307	0.129	0.750
ALB, g/L	23.30	24.60	0.63	0.312	0.311	0.643
GLOB, g/L	42.85	45.03	1.21	0.378	0.133	0.853
CHOL, mmol/L	2.35	2.19	0.09	0.341	0.374	0.680
HDL-CHOL, mmol/L	1.43	1.34	0.04	0.327	0.599	0.718
LDL-CHOL, mmol/L	0.80	0.72	0.05	0.390	0.255	0.582
TGC, mmol/L	0.27	0.25	0.01	0.747	0.001	0.013
NEFA, mmol/L	0.13	0.14	0.02	0.901	0.011	0.212
BHB, mmol/L	0.78	0.77	0.07	0.976	0.207	0.726

COG: control oat group; BOG: black oat group; D: diet; P: sampling time; D × P: interaction (diet × sampling time); SEM: standard error of mean; GUK: glucose; TP: total proteins; ALB: albumins; GLOB: globulins; CHOL: cholesterol; HDL-CHOL: HDL-cholesterol; LDL-CHOL: LDL-cholesterol; TGC: triglycerides; NEFA: non-esterified fatty acids; BHB: β-hydroxybutyrate.

and

Table 4. Enzyme activities in the blood of goats during investigation.

	Diets		SEM	p Value
	COB	BOG		D	P	D × P
AST, U/L	131.30	122.17	5.01	0.395	0.902	0.486
ALT, U/L	20.22	20.61	1.13	0.865	0.092	0.989
GGT, U/L	43.76	45.41	1.63	0.610	0.041	0.967
CK, U/L	184.95	197.76	12.50	0.577	0.186	0.496
GPx, U/L	1029.83	1023.76	55.25	0.955	0.023	0.669

COG: control oat group; BOG: black oat group; D: diet; P: sampling time; D × P: interaction (diet × sampling time); SEM: standard error of mean; AST: aspartate aminotransferase; ALT: alanine aminotransferase; GGT: γ-glutamyl transferase; CK- creatine kinase; GPx: glutathione peroxidase.

and Figure 1.

A significantly lower concentration of urea in the blood was found in the blood of goats from the BOG (8.75:7.03 mmol/L, p = 0.020) group, while the determined concentrations of minerals and other metabolites in the blood did not differ significantly (p > 0.05; Table 3; Figure 1). However, there was a smaller increase in protein fractions, but also a slight decrease in lipid indicators in the blood of goats in the BOG group compared to the levels in the COB group (p > 0.05). Concentrations of minerals, GUK, NEFA, and BHB in the blood of goats did not vary with respect to the feeding treatment (p > 0.05). A significant effect of sampling time on urea, TGC, and NEFA concentrations (p = 0.020, p = 0.001, and p = 0.011) was also observed, as well as a significant effect of the interaction (diet × sampling time) on TGC concentration (p = 0.013) in the blood of the studied goats.

Analysis of the enzyme activity in the blood of goats in both groups (Table 4) did not show any major differences that would be connected to the feeding treatment. A significant effect of sampling time on GPx activity (p = 0.023) in the blood of the studied goats was also determined.

4. Discussion

Plants rich in polyphenols or plant pure extracts supplemented in the feed of dairy ruminants can have an anti-inflammatory effect and increase milk production [37]. The conducted experiment did not result in significant changes in the production and quality of milk, except for the slightly increased amount of milk (1264.94:1542.10 g/day; p = 0.098) and slightly decreased concentration of urea (7.90:7.05 mmol/L, p = 0.081) and globulin (5.16:3.96 g/L, p = 0.091) in milk (Table 2). The above results can be connected with the effect of polyphenols in the BOG group compared to the COG group. Animal species, age, sex, physiological and health status, timing and duration of exposure, as well as polyphenol metabolism and bioavailability, are additional physiological factors that modulate their effects. Consistent with the slightly increased milk yield observed in the present study, supplementation of a phytogenic feed additive mixture rich in polyphenols in the diets of lactating Friesian cows at a dose of 3 g/day per cow was reported to increase milk production by 6% and energy-corrected milk by 13% [38]. As published by Kholif et al. [39], this improvement in milk yield could be due to improved rumen fermentation and efficient feed utilization. Namely, Salem et al. [40] concluded that milk yield in dairy cows can be increased by reducing protein and energy losses during fermentation and improving feed utilization by the rumen microflora. A review of the literature [1] found that the results of the effect of polyphenols from animal feed on milk production in dairy ruminants are contradictory. Furthermore, those authors point out that the positive effect on milk production in dairy ruminants was associated with the modulation of stressors when adding polyphenols to the diet, which was obvious in stressful periods, such as the transitional period of early lactation. The above results may also be the reason for the non-significant increased milk production in the BOG groups in our study.

Biochemical indicators showing the blood metabolic profile can be used for diagnosis and prognosis of diseases and for assessment of animal welfare and condition [41]. The average serum concentrations of minerals in our study, showed in Figure 1, were similar among treatments, but the goats exhibited lower concentrations of Ca (1.95 and 2.03 mmol/L) and higher conentrations of Mg (1.52 and 1.51 mmol/L) compared to the reference values for goats [42]. For Ca, the values ranged from 2.30 to 2.90 mmol/L, and for Mg, the values varied from 0.8 to 1.30 mmol/L. Such changes can be associated with the 1/3 lactation period of goats when milk production is the highest. Indeed, it is known that significant amounts of Ca are excreted in milk, especially in the 1/3 lactation period in small ruminants [43,44]. It is also known that lactation is a very demanding period for animals, and significant fluctuations in blood parameters can occur because of milk secretion [45,46]. The slightly higher concentration of TP in the blood of the BOG goats determined in this experiment (69.62:66.15 g/L, p = 0.307) can be connected with increased amino acids and microbial protein duodenal flux in ruminants supplemented with flavonoids [47]. A slightly higher concentration of serum globulins (GLOB) was observed in this research (45.03:42.85 g/L, p = 0.378), indicating an enhanced immune response [38]. The liver plays a central role in protein metabolism, and any hepatic damage is reflected in total serum protein levels [48]. In this study, the observed significance changes in blood urea concentrations may be linked to the polyphenol content in black oats provided to goats in the BOG group in comparison with that received by goats in the COG group (7.03:8.75 mmol/L, p = 0.007). Supporting this, Giannenas et al. [49] reported that supplementation of a plant-based feed additive rich in polyphenols in cows reduced blood urea, increased serum globulin and total protein concentrations, improved nutritional status, enhanced microbial protein synthesis, and minimized protein catabolism. The blood NEFA concentrations in both groups of goats in this research were similar (p > 0.05) and within reference values (<0.4 mmol/L), which indicated similar energy status [41,50].

In the present study, certain favorable improvements in lipid status were determined, as there was a certain slight decrease in the concentration of total CHOL (2.19:2.35 mmol/L, p = 0.341) and its fractions (HDL-CHOL 1.34:1.43 mmol/L, p = 0.032 and LDL-CHOL 0.72:0.80 mmol/L, p = 0.390) and TGC (0.25:0.27 mmol/L, p = 0.747) in the blood of the BOG group in comparison with those in the COG group. Research conducted on animals using colored grains rich in anthocyanins in ratio indicate, among other benefits, improvements in the oxidation of LDL-cholesterol, VLDL-cholesterol, and total triglycerides in the blood [51,52,53,54]. Furthermore, in a study by Sharma et al. [55], when feeding mice high-fat meals with the addition of black and purple wheat for 12 weeks led to a decrease in total cholesterol and triglyceride concentrations in the serum blood and an increase in blood glucose concentrations to normal levels. The determined non-significant reduction of lipid profile indicators (CHOL and its fractions and TGC) in the blood of goats in the BOG group in the present research indicates the need for a longer duration of the research, when a significant improvement in the blood lipid status of the researched goats could be expected when feeding with feed mixtures supplemented with black oats.

In the present study, no significant changes (p > 0.05) were observed in the blood enzyme activities of goats in the COB and BOG groups (Table 4), suggesting that liver metabolism remained normal and lipid metabolism was appropriate. As noted by Silanikove and Tiomkin [56], serum activities of AST and GGT, along with cholesterol (CHOL) concentrations, are commonly used to assess hepatic function in both humans and animals. The similarity in enzyme activities (AST, ALT, and GGT) between the COB and BOG groups indicates that dietary supplementation with black oats had no adverse effects on hepatic metabolism.

The limitations of this study are reflected in its relatively short duration, as well as in the shorter adaptation period of the goats to the new diet. Consequently, it is possible that not all long-term effects of the dietary change on production and metabolic parameters were fully expressed, and a longer study might result in clearer and more stable differences among the studied groups.

5. Conclusions

The use of black oats in the diet of goats during early lactation resulted in a slight increase in milk yield, a significant decrease in blood urea concentrations, and no significant changes in protein and lipid metabolism. These findings indicate that black oats can be used as an alternative feed ingredient in diets for lactating goats; however, further research is needed to expand the evaluation to include indicators of immune response and antioxidant status in goats.