Research shows that feeding growing lambs high-protein diets (up to 18% crude protein) and high-energy grain-based feeds does not damage their liver or kidney function. A 2026 study of 64 lambs found that while extra protein increased blood urea levels—a normal waste product—all liver and kidney health markers remained normal, indicating the organs handled the extra workload safely without damage.
Researchers tested whether feeding young lambs high-protein and high-energy diets could damage their livers or kidneys. They studied 64 young sheep over 57 days, giving some groups more concentrated feed and others more protein. Blood tests showed that while extra protein increased urea levels (a normal waste product), it didn’t harm the animals’ liver or kidney function. According to Gram Research analysis, this suggests that growing lambs can safely handle protein levels above their basic needs without developing organ damage, though urea levels should still be monitored.
Key Statistics
A 2026 study of 64 growing lambs found that increasing dietary protein from 12% to 18% caused serum urea to rise linearly, but did not affect liver enzymes (ALT, AST, AP, GGT) or kidney function markers (creatinine), indicating no organ damage occurred.
Research published in Tropical Animal Health and Production (2026) demonstrated that lambs fed concentrated grain diets up to 70% of total feed intake maintained normal blood markers for liver and kidney health, with no changes in albumin, cholesterol, or kidney function tests.
A 57-day feeding trial with 64 lambs showed that crude protein intake above nutritional requirements increased serum urea (p = 0.0002) but caused no changes in alkaline phosphatase, albumin, AST, ALT, GGT, creatinine, or cholesterol levels.
The Quick Take
- What they studied: Whether feeding young sheep extra protein and concentrated grain damages their liver or kidney function
- Who participated: 64 healthy male lambs, four months old, weighing about 20 kg each, fed individually for 57 days
- Key finding: High-protein diets increased urea (a waste product) in the blood, but didn’t harm liver or kidney health markers
- What it means for you: If you raise sheep, you can safely feed growing lambs extra protein without worrying about organ damage, though monitoring blood urea levels is still a good practice
The Research Details
Scientists divided 64 young lambs into two separate experiments. In the first experiment, they tested four different diets with varying amounts of concentrated grain (from 40% to 70% of the diet). In the second experiment, they tested four diets with different protein levels (ranging from 12% to 18% protein). All lambs ate as much as they wanted for 57 days, with a two-week adjustment period at the start. On day 54, the researchers took blood samples from all the lambs and tested them for eight different markers of liver and kidney health.
The researchers chose these specific blood tests because they’re the best way to detect if an organ is being damaged or stressed. Albumin shows if the liver is making proteins properly. Urea and creatinine show if the kidneys are filtering waste correctly. The liver enzymes (ALT, AST, AP, and GGT) show if liver cells are being damaged. By measuring all these markers, the scientists could tell if the high-protein, high-energy diets were hurting the animals’ organs.
This research approach is important because farmers need to know if feeding extra protein and energy to growing animals is safe. Previous studies in other animals suggested high protein might stress the kidneys, so testing this directly in sheep was necessary. By using blood markers instead of examining organs after death, the researchers could detect problems early and measure them precisely.
This study has good strengths: it used a reasonable number of animals (64), kept conditions controlled by housing lambs individually, and used standard blood tests that are well-established for detecting organ problems. However, the study only lasted 57 days, so we don’t know if problems might develop over longer periods. The study also only tested one breed of sheep (Santa Inês), so results might differ in other breeds. The researchers didn’t report some details about how they selected the lambs or whether they were truly random assignments.
What the Results Show
When researchers increased the amount of concentrated grain in the diet (Experiment 1), the blood markers for liver and kidney health stayed normal and didn’t change. This was true even when the lambs ate 70% concentrated feed instead of 40%. The only unusual finding was that urea levels were higher than the normal reference range (17-43 mg/dL), while creatinine was lower than normal (1.2-1.9 mg/dL).
In Experiment 2, when protein levels were increased from 12% to 18%, serum urea rose in a predictable, straight-line pattern—the more protein the lambs ate, the more urea appeared in their blood. However, all the liver health markers (ALT, AST, AP, GGT) and kidney function markers (creatinine, albumin) stayed completely normal. Cholesterol levels also remained unchanged.
The key insight is that while urea increased with extra protein, this is actually expected and normal. Urea is simply a waste product that the body makes when it breaks down protein. The fact that liver enzymes and kidney function markers didn’t change suggests the organs themselves weren’t being damaged—they were just working normally to process the extra protein.
The study found that albumin (a protein made by the liver) didn’t change with either higher energy or higher protein intake, suggesting the liver’s ability to make proteins stayed strong. Cholesterol levels also remained stable across all diet groups. These findings indicate that the liver was functioning normally even under the stress of processing extra nutrients. The creatinine levels being below the normal reference range in Experiment 1 is interesting but wasn’t explained by the researchers—it might suggest the lambs were very healthy or that the reference range used might not be perfectly accurate for this breed.
This research aligns with what scientists have found in other livestock species: healthy animals can usually handle extra protein without organ damage. However, some previous studies in cattle and pigs suggested that extremely high protein diets might eventually stress the kidneys. This sheep study suggests that at least in the short term (57 days), growing lambs are quite resilient. The finding that urea increases with protein is completely expected and matches what happens in humans and other animals—it’s not a sign of danger, just a sign that the body is processing protein.
The biggest limitation is that this study only lasted 57 days. We don’t know if problems might develop after months or years of high-protein feeding. The study also only tested one breed of sheep (Santa Inês), so results might be different in other breeds or in adult sheep. The researchers didn’t measure how much the lambs actually grew or how efficiently they converted feed to meat, so we don’t know if the extra protein and energy actually helped them grow better. Additionally, the study didn’t track what happened to the lambs after the experiment ended, so we can’t say whether any delayed effects occurred.
The Bottom Line
Based on this research, sheep farmers can safely feed growing lambs diets with extra protein and concentrated grain without immediate concern for liver or kidney damage (moderate-to-high confidence). However, it’s still wise to monitor blood urea levels periodically, as elevated urea might indicate the kidneys are working harder than normal. Farmers should also ensure lambs have adequate water, as high-protein diets require more water for proper kidney function. If lambs show signs of illness or poor appetite, blood work should be done to rule out other problems.
This research matters most to sheep farmers and livestock nutritionists who want to optimize growth in young lambs. It’s also relevant to veterinarians who advise on lamb nutrition. Pet owners with sheep should know this information but should consult their veterinarian before making major diet changes. This research is less relevant to people who don’t raise sheep, though it contributes to our general understanding of how animals process protein.
The study measured changes over 57 days, so any benefits or problems from diet changes would likely appear within 2 months. However, long-term effects (beyond 3-6 months) are unknown based on this research. If you change a lamb’s diet, you should monitor its health and appetite within the first few weeks and consider blood work after 4-6 weeks to check kidney function.
Frequently Asked Questions
Can high-protein diets damage a lamb’s kidneys?
A 2026 study of 64 lambs found that high-protein diets (up to 18% protein) did not damage kidney function markers like creatinine, even though blood urea increased. The kidneys appeared to handle the extra protein workload safely without organ damage.
What does elevated urea in sheep blood mean?
Elevated urea is a normal result of eating more protein—it’s simply the waste product created when the body breaks down protein. In this study, high urea didn’t indicate kidney disease; it just showed the kidneys were processing extra protein normally.
Is it safe to feed lambs concentrated grain diets?
Yes, according to this 2026 research. Lambs fed diets with 40-70% concentrated grain showed no changes in liver or kidney health markers over 57 days, suggesting concentrated feeds are safe when properly balanced.
How long does it take to see if a high-protein diet harms a lamb?
This study measured changes over 57 days (about 2 months) and found no organ damage. However, longer-term effects beyond 3-6 months are unknown, so periodic blood work is recommended for lambs on high-protein diets.
Should I monitor my lamb’s blood work if feeding high protein?
While this study showed no organ damage, monitoring blood urea and creatinine every 6-8 weeks is a good practice. It allows early detection of any problems and confirms the lamb’s kidneys are handling the diet well.
Want to Apply This Research?
- Track weekly weight gain and feed intake for each lamb, then calculate feed efficiency (pounds of feed per pound of weight gained). Also note any changes in water consumption or urine output, as these can indicate kidney stress.
- If using a livestock management app, input the protein percentage and concentrate level of each lamb’s diet, then set reminders for blood work every 6-8 weeks to monitor urea and creatinine levels. This allows early detection of any problems.
- Create a spreadsheet tracking each lamb’s diet composition, weight, and blood urea levels over time. Set alerts if urea exceeds 50 mg/dL or if weight gain drops below expected rates, which could indicate the diet needs adjustment.
This research applies specifically to growing lambs and may not apply to adult sheep, other livestock species, or other breeds. The study lasted only 57 days, so long-term effects are unknown. Always consult with a veterinarian or livestock nutritionist before making significant changes to your animal’s diet. This article is for informational purposes and should not replace professional veterinary or nutritional advice. Individual animals may respond differently to diet changes based on genetics, health status, and environmental factors.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.