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Physiological adaptation and lipid utilization efficiency in lactating fat-tailed Turki-Qashqaei ewes fed graded levels of cracked safflower

This study demonstrates that while increasing dietary cracked safflower in lactating fat-tailed Turki-Qashqaei ewes boosts milk fat yield and unsaturated fatty acid intake, it concurrently reduces nutrient digestibility and alters blood metabolites, indicating that ruminal biohydrogenation and post-absorptive constraints limit the linear efficiency of lipid utilization in this breed.

Original authors: Shiva Forouzanfar, Amir Ahmadpour, Mousa Zarrin, Mehrdad Meamar

Published 2026-07-14

📖 6 min read🧠 Deep dive

CC BY 4.0

Original authors: Shiva Forouzanfar, Amir Ahmadpour, Mousa Zarrin, Mehrdad Meamar

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine a flock of Turki-Qashqaei ewes, a special breed of sheep famous for their fluffy, fat-filled tails that act like built-in backpacks of energy. These moms are currently lactating, which is basically their body's "all-hands-on-deck" mode for making milk. The scientists wanted to see what happens if they feed these moms a diet loaded with cracked safflower seeds, a source of healthy oils, to see if it supercharges their milk production or if their bodies get confused.

They set up a little experiment with three groups of 12 moms each. One group got the regular diet (0% safflower), one got a "light snack" version (3% safflower), and the third got the "heavy snack" version (6% safflower). They replaced some of the usual barley grain with the seeds so the total energy stayed the same, just swapping the fuel type.

Here is the story of what happened, based on the data they collected:

The Fuel Intake: No "Full" Signal

You might think that if you feed a sheep more fatty, oily seeds, they would feel full faster and eat less. But that didn't happen. The sheep ate almost the exact same amount of food every day, whether they had 0% or 6% safflower. Their stomachs didn't send a "stop eating" signal.

However, because the safflower is so oily, the group eating 6% safflower actually swallowed way more fat. Their intake of ether extract (the scientific term for the fat in their food) went up, and their intake of linoleic acid (a specific type of oil found in safflower) skyrocketed by about 181.5% compared to the control group. It was like swapping a plain cracker for a cracker covered in a thick layer of butter; the volume is the same, but the fat content is massive.

The Digestive Factory: A Clogged Conveyor Belt

Inside the sheep's stomach (the rumen), there are tiny microbes that act like a factory, breaking down food. When the sheep ate the high-fat diet (6% safflower), the factory started to slow down. The scientists found that the sheep couldn't digest their food as well as before.

Specifically, the ability to break down dry matter dropped from 68.52% in the control group to 65.14% in the high-fat group. The same thing happened with fiber (NDF and ADF) and even the fat itself (ether extract digestibility dropped from 85.56% to 78.92%).

Think of it like pouring too much oil into a machine; the gears get slippery and can't grab the other parts as well. The high fat didn't stop the machine, but it made it less efficient at chewing up the fiber. Interestingly, the protein digestion stayed the same, so the "protein workers" in the stomach were still doing their job fine.

The Rumen: A Calm Lake

Despite the extra oil, the rumen environment remained surprisingly calm. The pH level (acidity) stayed steady around 6.5, and the levels of ammonia and total gases (VFA) didn't change much. It's as if the sheep's stomach is a very resilient lake; even when you throw in a big splash of oil, the water level and temperature don't go wild. The balance between different types of fermentation gases (acetate and propionate) stayed mostly the same, too.

The Blood: A Shift in Energy Currency

When the scientists looked at the sheep's blood, they saw some interesting changes, especially in the group eating 6% safflower.

Glucose: The sugar in their blood dropped by about 11% (from 3.72 mmol/L down to 3.31 mmol/L).
Fat in Blood: At the same time, the levels of free fatty acids (NEFA) jumped by 107% (from 0.14 mmol/L to 0.29 mmol/L), and triglycerides (another type of fat) rose by 86% (from 0.21 mmol/L to 0.39 mmol/L).

This suggests the sheep's bodies were switching gears. Instead of relying on sugar, they were pulling more fat from their own reserves (like that fat tail!) and circulating it in the blood to be used as fuel. It's like the body said, "We have too much oil coming in, so let's stop burning sugar and start burning the fat we have stored."

The Milk: More Fat, But Not Perfectly Efficient

Did the extra oil make more milk fat? Yes. The milk fat yield went up, reaching 0.19 kg/d in the high-fat group compared to 0.15 kg/d in the control group.

However, the efficiency of using that oil was tricky.

When they looked at how much milk fat was produced per unit of fat eaten, it actually went up (from 2.49 to 2.91).
But, when they looked specifically at how much of the linoleic acid (the safflower oil) actually ended up in the milk, it went down (from 10.51 to 9.24).

This is the big twist. The sheep made more milk fat overall, but they didn't use the safflower oil directly to do it. Instead, the body seems to be filtering the oil. A lot of the safflower oil gets changed by the stomach bacteria (a process called biohydrogenation) or burned off as energy before it can reach the milk. The sheep are good at making milk fat, but they aren't very good at taking that specific safflower oil and putting it straight into the milk.

The Hormone Team

The hormones in the sheep's blood told a story of adaptation.

Glucagon: This hormone, which tells the body to release stored energy, shot up by 60% in the high-fat group. It's like the body's alarm clock ringing to say, "We need to mobilize our fat reserves!"
Insulin: This stayed steady, which is normal for sheep.
IGF-1: This growth hormone went up by about 15% and then leveled off, suggesting the body was trying to keep the milk production going strong.

The Bottom Line

The paper suggests that feeding cracked safflower seeds to these fat-tailed sheep changes how their bodies handle energy, but it doesn't give a simple "more oil = more milk" result.

The high-fat diet made the sheep digest their food slightly less efficiently and changed their blood chemistry to rely more on fat than sugar. While they did produce more milk fat, the body had to work hard to adapt, and a lot of the specific safflower oil was lost in the process of digestion or used for energy rather than milk.

The authors conclude that for these fat-tailed breeds, adding oil is less about a straight line to more production and more about how the sheep's unique body (with its fat tail and special metabolism) adapts to the new fuel. It's a complex dance of digestion, blood chemistry, and hormone signals, proving that nature is rarely as simple as just "add more, get more."

Technical Summary: Physiological Adaptation and Lipid Utilization Efficiency in Lactating Fat-Tailed Turki-Qashqaei Ewes

Problem Statement
Dietary lipid supplementation is a standard strategy in ruminant nutrition to increase energy density and supply essential fatty acids, particularly during the high-demand period of lactation. However, the physiological mechanisms governing lipid utilization in small ruminants, specifically fat-tailed breeds like the Turki-Qashqaei, remain poorly understood. Unlike monogastric species, ruminants are subject to extensive ruminal biohydrogenation, which alters the profile of unsaturated fatty acids (UFA) before they reach the small intestine. While previous research has focused on productive outcomes (milk yield and composition) in dairy cattle and thin-tailed sheep, there is a scarcity of empirical data regarding how fat-tailed breeds—characterized by distinct tail adipose energy reserves—adapt metabolically to graded increases in dietary unsaturated lipid supply. The specific interplay between ruminal biohydrogenation, post-absorptive metabolism, and the unique energy storage strategies of fat-tailed breeds during lactation requires further mechanistic investigation.

Methodology
The study employed a completely randomized design using 36 multiparous lactating fat-tailed Turki-Qashqaei ewes (approx. 31 days in milk, 54.5 kg body weight). Animals were assigned to three dietary treatments (n=12 per group) involving graded inclusion levels of cracked safflower seeds: 0% (SS0), 3% (SS3), and 6% (SS6) of dry matter (DM). The safflower replaced equivalent proportions of barley grain to maintain isonitrogenous and isoenergetic conditions relative to NRC (2007) recommendations.

Data collection occurred over a 21-day period following a 12-day adaptation phase. The study evaluated:

Intake and Digestibility: Daily feed intake and apparent total-tract digestibility of nutrients (DM, OM, CP, EE, NDF, ADF) were measured using the acid-insoluble ash (AIA) internal marker method.
Rumen Fermentation: Fluid samples were analyzed for pH, ammonia-N, total volatile fatty acids (VFA), and the acetate:propionate ratio.
Blood Metabolites and Endocrine Profile: Serum was analyzed for glucose, $\beta$ -hydroxybutyrate (BHB), non-esterified fatty acids (NEFA), triglycerides (TG), total protein, albumin, and a panel of hormones (glucagon, insulin, leptin, prolactin, adiponectin, IGF-1).
Milk Production and Lipid Indices: Milk yield and fat content were recorded. Derived indices included milk fat yield per ether extract (EE) intake and milk long-chain fatty acid (LCFA) output per linoleic acid intake to assess lipid utilization efficiency.

Key Results

Intake and Digestibility: Increasing safflower inclusion did not affect total dry matter intake (DMI). However, digestible DMI per unit of metabolic body weight declined linearly. Apparent digestibility coefficients for DM, organic matter, ether extract, NDF, and ADF decreased significantly with higher safflower inclusion, with the most pronounced reductions observed at the 6% level. Crude protein digestibility remained unaffected.
Rumen Fermentation: Rumen fermentation parameters (pH, ammonia-N, total VFA, and acetate:propionate ratio) remained stable across all treatments, indicating that moderate safflower inclusion (up to 6% DM) did not disrupt ruminal homeostasis.
Blood Metabolites: At the 6% inclusion level, serum glucose decreased significantly (approx. 11% reduction) compared to controls. Conversely, NEFA and triglyceride concentrations increased markedly (107% and 86% increases, respectively). Total protein and albumin levels also increased linearly. Serum BHB remained stable, suggesting enhanced lipid mobilization without ketosis.
Endocrine Responses: Serum glucagon concentrations showed a sharp, dose-dependent increase at the 6% level (approx. 60% higher than control), while insulin, leptin, and prolactin remained stable. Adiponectin showed a quadratic response (peaking at 3%), and IGF-1 increased linearly, plateauing at the 3% level.
Lipid Utilization and Milk Fat: Milk fat yield increased significantly with safflower supplementation. While the efficiency of converting ether extract intake into milk fat rose linearly, the efficiency of converting dietary linoleic acid into milk long-chain fatty acids declined linearly. This indicates a nonlinear metabolic regulation where increased dietary UFA supply does not result in proportional increases in milk LCFA output.

Key Contributions
The study provides mechanistic insights into how fat-tailed sheep manage increased dietary unsaturated lipid loads. It demonstrates that while moderate lipid supplementation can enhance milk fat yield, it triggers specific physiological adaptations rather than simple linear productive gains. The research highlights that the efficiency of lipid utilization in lactating fat-tailed ewes is constrained by ruminal biohydrogenation and post-absorptive metabolic limits, leading to a shift in nutrient partitioning. The findings suggest that the unique tail fat depot in these breeds may act as a buffer, influencing how excess fatty acids are handled (e.g., oxidation or storage) rather than solely being directed toward milk synthesis.

Significance and Claims
The paper claims that its findings offer a physiologically grounded perspective on lipid metabolism in fat-tailed breeds, moving beyond simple production metrics. It asserts that the observed nonlinear responses—specifically the decline in linoleic acid utilization efficiency despite increased milk fat yield—reflect adaptive metabolic regulation involving ruminal biohydrogenation and systemic constraints. The study concludes that lipid supplementation in lactating fat-tailed ewes primarily influences nutrient utilization efficiency and physiological adaptation. These insights are presented as essential for developing feeding strategies that optimize nutrient use without compromising rumen function or metabolic health, particularly in semi-arid regions where safflower residues are available. The authors emphasize that future strategies must account for both ruminal and post-absorptive constraints when formulating diets for these specific breeds.