Dairy ruminants provide a major part of the livestock and agriculture sectors. Due to the increase in world population and the subsequent increase in dairy product demands, the dairy sector has been intensified. Dairy farming intensification and the subsequent increase in animal nutritional demands and the increase in the average global temperature as well have subjected animals to various stress conditions that impact their health and welfare. Various management practices and nutritional strategies have been proposed and studied to alleviate these impacts, especially under heat stress, as well as during critical periods, like the transition period. Some of the nutritional interventions to cope with stress factors and ensure optimal health and production are the inclusion of functional fatty acids and amino acids and feed additives (minerals, prebiotics, probiotics, essential oils and herbs, phytobiotics, enzymes, etc.) that have been proven to regulate animals’ metabolism and improve their antioxidant status and immune function. Thus, these nutritional strategies could be the key to ensuring optimum growth, milk production, and reproduction efficiency. This review summarizes and highlights key nutritional approaches to support the remarkable metabolic adaptations ruminants are facing during the transition period and to reduce heat stress effects and evaluate their beneficial effects on animal physiology, performance, health, as well as welfare.

Camelina sativa seeds are rich in bioactive compounds such as polyunsaturated fatty acids (PUFA) and antioxidants, thus, their supplementation in ewes’ diets, may be an effective way to develop high nutritional dairy products. Therefore, the present study investigates the effect of the dietary inclusion of Camelina sativa seeds in ewes’ oxidative status and milk quality. Forty-eight dairy Chios ewes were divided into four homogenous groups and were fed individually. The concentrate of the control group (CON) had no inclusion of Camelina seeds, while the treatment groups (CSS6, CSS11, CSS16) were supplemented with 6%, 11%, and 16%, respectively. Including Camelina seeds in 6% and 11%, had no impact on milk performance, while in the CSS16, milk fat was significantly decreased compared to the CON. Supplementing Camelina seeds improved milk quality from a human health perspective by modifying the content of saturated fatty acid, the proportions of α-linolenic (C_{18:3 n-3}), and C_{18:2 cis-9, trans-11} (CLA), and the ω6/ω3 ratio. Furthermore, the activity of catalase (CAT) was significantly increased in the CSS11 and CSS16, and superoxide dismutase (SOD) activity also significantly upsurged in the CSS16. Still, the levels of malondialdehyde (MDA) were significantly increased in the CSS11 compared to the CON and CSS6, and in the CSS16 compared to the CSS6. In CSS16, protein carbonyls were significantly increased. Finally, in the CSS-fed ewes, milk oxidative stability was fortified, as suggested by the modifications in the activities of SOD, CAT, and glutathione peroxidase (GSH-Px), in the antioxidant capacity, and the oxidative stress biomarkers. Consequently, the incorporation of 6% Camelina seeds in the concentrates of ewes improves milk’s fatty acid profile and oxidative status. However, more research is required regarding the possible negative effects of the constant consumption of Camelina seeds by ewes.

Supplementing ruminant diets with microalgae, may prove an effective nutritional strategy to manipulate rumen microbiota. Forty-eight ewes were divided into four homogenous groups (n = 12) according to their fat-corrected milk yield (6%), body weight, age, and days in milk, and were fed individually with concentrate, alfalfa hay, and wheat straw. The concentrate of the control group (CON) had no Spirulina supplementation, while in the treated groups 5 (SP5), 10 (SP10), and 15 g (SP15) of Spirulina were supplemented as an additive in the concentrate. An initial screening using metagenomic next-generation sequencing technology was followed by RT-qPCR analysis for the targeting of specific microbes, which unveiled the main alterations of the rumen microbiota under the Spirulina supplementation levels. The relative abundance of Eubacterium ruminantium and Fibrobacter succinogenes in rumen fluid, as well as Ruminococcus albus in rumen solid fraction, were significantly increased in the SP15 group. Furthermore, the relative abundance of Prevotella brevis was significantly increased in the rumen fluid of the SP5 and SP10 groups. In contrast, the relative abundance of Ruminobacter amylophilus was significantly decreased in the rumen fluid of the SP10 compared to the CON group, while in the solid fraction it was significantly decreased in the SP groups. Moreover, the relative abundance of Selenomonas ruminantium was significantly decreased in the SP5 and SP15 groups, while the relative abundance of Streptococcus bovis was significantly decreased in the SP groups. Consequently, supplementing 15 g Spirulina/ewe/day increased the relative abundance of key cellulolytic species in the rumen, while amylolytic species were reduced only in the solid fraction.

Supplementing ruminant diets with unconventional feedstuffs (Camelina sativa seeds; CS) rich in bioactive molecules such as polyunsaturated fatty acids, may prove a potential eco-efficient strategy to manipulate rumen microbiome towards efficiency. Forty-eight ewes were divided into four homogenous groups (n = 12) according to their fat-corrected milk yield (6%), body weight, and age, and were fed individually with concentrate, alfalfa hay, and wheat straw. The concentrate of the control group (CON) had no CS inclusion, whereas the treated groups were supplemented with CS at 60 (CS6), 110 (CS11), and 160 (CS16) g·kg⁻¹ of concentrate, respectively. Rumen digesta was collected using an esophageal tube and then liquid and solid particles were separated using cheesecloth layers. An initial bacteriome screening using next-generation sequencing of 16S was followed by specific microbes targeting with a RT-qPCR platform, which unveiled the basic changes of the rumen microbiota under CS supplementation levels. The relative abundances of Archaea and methanogens were significantly reduced in the solid particles of CS11 and CS16. Furthermore, the relative abundance of Protozoa was significantly increased in both rumen fluid and solid particles of the CS6, whereas that of Fungi was significantly reduced in the rumen particle of the CS16. In rumen fluid, the relative abundance of Fibrobacter succinogens and Ruminobacter amylophilus were significantly increased in the CS6 and CS11, respectively. In the solid particles of the CS11, the relative abundance of Ruminococcus flavefaciens was significantly reduced, whereas those of Butyrivibrio proteoclasticus and Ruminobacter amylophilus were significantly increased. Additionally, the relative abundance of Selenomonas ruminantium was significantly increased in both CS11 and CS16. Consequently, the highest CS content in the concentrate reduced the relative abundance of methanogens without inducing radical changes in rumen microorganisms that could impair ruminal fermentation and ewes’ performance.

This study evaluated the effects of maternal supplementation with rumen-protected methionine (RPM), alone or combined with rumen-protected choline (RPC) and betaine (RPB), during the periconceptional and prepartum periods on reproductive outcomes and offspring performance in Chios ewes. One hundred synchronized ewes were assigned to three groups—control (no supplementation), M (5.50 g RPM/day), and MCB (3.50 g RPM, 1.60 g RPC, 0.49 g RPB/day)—from day −14 to +14 relative to mating. Blood was collected on days −14, 0, and +14 for ABTS (2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid), ferric-reducing ability (FRAP), and malondialdehyde (MDA), on days 18 and 21 for progesterone, and on day 26 for pregnancy-associated glycoprotein (PAG) detection. Thirty days before and up to lambing, the ewes were further divided into C-C, C-M, C-MCB, M-M, M-C, MCB-MCB, and MCB-C subgroups. Embryonic loss did not differ between groups. FRAP was higher (p < 0.001) in MCB ewes, and ABTS was lower (p < 0.05) in M ewes, in the periconceptional period. Offspring in the C-M, C-MCB, M-M, M-C, and MCB-MCB groups had higher birth weights (p < 0.01), along with increased MDA levels (p < 0.05). The results suggest that maternal methyl donor supplementation during early and/or late gestation enhances antioxidant status, supports embryonic development, and increases birth weight.

The increasing popularity of Greek yogurt generates large amounts of acid whey worldwide. The use of yogurt acid whey in animal nutrition is limited. The aim of this study was to determine the effect of a yogurt acid whey powder (YAWP) addition to maize forage prior to ensiling on the nutritional, microbial and fermentation quality of maize silage. Depending on the addition level of the YAWP to maize forage, there were the following four experimental treatments: YAWP 0, 2.5, 5 and 10% w/w. An increasing YAWP inclusion level linearly increased the maize silage dry matter, crude protein and ash concentrations, whereas it reduced the crude fiber, neutral-detergent fiber and acid-detergent fiber concentrations. The silage pH decreased quadratically with the increasing YAWP level, with the lower plateau noted for the YAWP 5% addition. Concentrations of total bacteria in the silage and Lactobacillus spp. decreased linearly with the YAWP increase. The silage acetic acid content decreased linearly, whereas propionic acid, lactic acid and the ratio of lactic to acetic acid increased linearly with the increasing YAWP level. The ammonia-N content decreased linearly with the increasing YAWP level. In conclusion, the incorporation of the 5 and 10% YAWP addition in silage preparation improved the nutritional and fermentative quality of the produced silage.