The research team, led by Rabia Arslan together with Necmettin Ünal and Akın Yakan of Ankara University’s Faculty of Veterinary Medicine, worked with 36 healthy male Lalahan lambs, all born as singletons during the same lambing season and weaned at about 90 days of age. The lambs were randomly divided into three groups and fed intensively until each group reached an average live weight of 35, 40, or 45 kilograms. Six lambs from each group, those closest to the group mean, were then selected for slaughter, giving the team 18 carcasses to dissect, weigh, and analyze joint by joint. Every animal received the same treatment before the experiment began: raised alongside their mothers under identical herd management, with ewes that had given birth at least twice, ensuring the lambs genuinely represented the Lalahan genotype.

The feeding regime was carefully standardized. Fattening started with 400 grams of concentrate per lamb per day plus 300 grams of alfalfa hay, after which the lambs were individually fed concentrate ad libitum with the same limited hay ration. Feeders were weighed morning and evening, leftovers collected and deducted, and body weights recorded every 14 days before feeding. Each lamb enjoyed 2 square meters of space, 50 centimeters of feeder length, and unlimited drinking water. From these meticulous measurements the researchers calculated the two numbers that matter most in fattening economics: daily weight gain and feed conversion rate, the kilograms of concentrate needed to produce one kilogram of body weight.

The growth numbers tell a story of steady, efficient performance. Average daily weight gains were 241.50, 243.33, and 235.45 grams in the 35, 40, and 45 kilogram groups respectively, figures that sit comfortably within the 230 to 265 gram range reported for intensively fattened Kıvırcık lambs, the breed from which Lalahan sheep largely descend. More impressive was the feed conversion. The Lalahan lambs needed just 3.590, 3.958, and 4.392 kilograms of concentrate per kilogram of gain in the three groups, substantially better than the 5.29 to 6.14 kilograms reported for Kıvırcık lambs in comparable intensive systems. In plain terms, these crossbred lambs turned feed into meat considerably more cheaply than one of their parent breeds, a trait with obvious economic value for producers operating on thin margins.

As expected, feed conversion worsened as the lambs grew heavier, because larger animals devote more of each meal to maintenance rather than growth. The jump from 3.590 to 4.392 kilograms of feed per kilogram of gain between the lightest and heaviest groups illustrates the classic diminishing returns of extended fattening. Yet the daily gain barely budged across the three groups, hovering around 240 grams regardless of target weight. That combination, flat growth rate but rising feed cost, is precisely why the question of when to stop fattening is so consequential, and why the carcass data that followed would prove decisive.

Slaughter characteristics were assessed both against pre-slaughter body weight and against empty-body weight, a refinement that accounts for the variable fullness of the digestive tract. Hot dressing percentages, the proportion of live weight that becomes a fresh carcass, were 46.22, 45.49, and 47.05 percent across the three groups, with cold dressing percentages of 45.26, 44.66, and 46.11 percent after 24 hours of chilling at 4 degrees Celsius. None of these differences reached statistical significance, though there was a slight upward trend with weight, likely reflecting greater muscle and fat deposition in heavier animals. The researchers also tracked how individual body components shifted with weight: feet and empty rumen proportions fell, while omental and mesenteric fat depots and testicle proportions rose, the latter a sign that the longer-fattened lambs were approaching puberty.

The carcass dissection delivered the study’s most consequential findings. Lean meat content was 61.82 percent in the 35 kilogram group and 61.04 percent in the 40 kilogram group, but dropped significantly to 57.53 percent at 45 kilograms. Fat told the mirror-image story: 13.57 and 14.05 percent in the two lighter groups, then a statistically significant leap to 19.46 percent in the heaviest lambs. Bone percentages stayed essentially constant at around 18 percent. The lean-to-fat ratio, a key index of carcass quality, was 4.56 and 4.35 in the 35 and 40 kilogram groups but collapsed to 2.98 at 45 kilograms. Notably, the lean percentages exceeded those reported for most Turkish native breeds, while the fat percentages were lower, an advantage the authors highlight as particularly important for modern consumers who increasingly prefer leaner carcasses.

Prime cuts shifted with weight as well. The hind leg, the most valuable joint, accounted for 31.57, 30.04, and 28.41 percent of the carcass in the three groups, a significant decline, while the loin fell from 8.41 to 7.19 percent. The back cut bucked the trend, rising from 13.39 to 14.72 percent. Meanwhile, the cross-sectional area of the longissimus dorsi muscle, the prized eye muscle running along the spine, grew steadily and significantly with slaughter weight, from 14.29 to 16.16 to 17.73 square centimeters, outperforming values reported for Kıvırcık lambs at comparable weights. Back fat depth also climbed, from 1.13 to 1.57 to 2.43 millimeters, though it remained generally lower than in other native breeds. The fact that muscle area expanded faster than fat thickness is, the authors argue, a genuine strength of the genotype.

Placing all the evidence side by side, the case for 40 kilograms becomes compelling. At that weight the lambs achieved their highest average daily gain, maintained a lean percentage above 61 percent, kept carcass fat near 14 percent, and avoided the steep feed conversion penalty that sets in beyond it. The 45 kilogram lambs delivered bigger eye muscles but paid for them with nearly a fifth of the carcass as fat and the worst feed efficiency of the trial. The 35 kilogram lambs were lean and efficient but left growth potential unrealized. The authors note that their recommendation aligns with international literature suggesting that around 38 to 42 kilograms represents the optimal balance between muscle development and fat deposition in medium-sized native and crossbred genotypes, even as European meat-type breeds are pushed to heavier weights.

Beyond the headline number, the study carries broader significance for Turkish agriculture, where sheep meat accounts for only 9.1 percent of red meat production despite growing demand for high-protein foods. The Lalahan genotype was bred for exactly this gap: an animal with good herding instinct, easy management, adequate fertility, and the hardiness to prosper on steppe pastures. Previous work had documented the breed’s reproductive performance, including estrus rates near 99 percent and twin births at just over 25 percent, but its meat traits had never been systematically measured. This first comprehensive assessment shows the Lalahan lamb matching or exceeding its Kıvırcık parentage in fattening performance, slaughter yield, and carcass composition, with a muscle-to-fat balance that suits contemporary market preferences. For a country seeking to raise its lamb output under challenging climatic conditions, a genotype that converts feed efficiently, deposits fat sparingly, and hits its peak value at a well-defined weight offers producers something rare: a clear, evidence-based target for profitability.

Subject of Research: Fattening performance, slaughter traits, and carcass characteristics of Lalahan-genotype lambs at different slaughter weights in Türkiye

Article Title: Meat production traits of Lalahan sheep: fattening, slaughter, and carcass characteristics of lambs

Article References: Arslan, R., Ünal, N., & Yakan, A. (2026). Meat production traits of Lalahan sheep: fattening, slaughter, and carcass characteristics of lambs. Archives Animal Breeding, 69(3), 431-439. https://doi.org/10.5194/aab-69-431-2026

Image Credits: AI Generated

DOI: 10.5194/aab-69-431-2026

Keywords: Lalahan sheep, lamb meat production, slaughter weight, carcass characteristics, feed conversion rate, daily weight gain, Kıvırcık, Akkaraman, crossbreeding, Türkiye, steppe conditions, animal breeding

The research, led by Camila S. da Silva of Embrapa Mid-North together with colleagues at Embrapa Dairy Cattle in Minas Gerais, Michigan State University, and the Federal University of Minas Gerais, was conducted at the Multi-User Laboratory of Livestock Bioefficiency and Sustainability in Coronel Pacheco, a humid subtropical site in the heart of Brazilian dairy country. The heifers entered the trial at roughly two and a half years of age with an average body weight of 563 kilograms. None were inseminated during the study, a deliberate design choice that removed pregnancy as a confounding factor and allowed the researchers to isolate how lactation itself reshapes the animal’s energy economy. The cows were housed in a free-stall barn equipped with electronic feed bins and automated weighing platforms, so that every kilogram of feed consumed and every fluctuation in body weight was captured in real time.

The animals received a total mixed ration based on corn silage, chopped hay, soybean meal, ground corn, urea, and minerals, reformulated at each of three lactation stages so that the roughage-to-concentrate ratio shifted from 62:38 in early lactation to 81:19 by late lactation. The diet supplied on average 18.41 megajoules of gross energy per kilogram of dry matter. Measuring what happened to that energy required an unusually demanding experimental battery: six total-tract digestibility trials, in which feces were collected completely over five consecutive days and urine was sampled by spot collections; and respirometry sessions in open-circuit respiration chambers, where cows spent 22-hour periods under thermoneutral conditions while oxygen consumption, carbon dioxide production, and methane output were quantified. From these measurements the team calculated digestible energy intake, metabolizable energy intake, heat production, and ultimately the full energy balance of each cow.

The headline finding is that these animals are, metabolically speaking, unusually comfortable dairy cows. Milk yield averaged 16.1 kilograms per day, with fat-corrected yield at 18.4 kilograms, moderate figures by Holstein standards but achieved with striking stability. Dry matter intake held nearly flat across the lactation, drifting only from 15.7 kilograms per day in early lactation to 14.7 in late lactation. Digestible and metabolizable energy intakes likewise barely moved, hovering near 180 and 150 megajoules per day respectively. In contrast to the dramatic metabolic rollercoaster familiar from high-producing Holsteins, the F1 crossbreds simply never fell into a deep or prolonged energy deficit. Their energy balance dipped to only about −12.9 megajoules per day in the earliest stage and turned positive, reaching +8.8 megajoules per day, once cows reached mid-lactation.

That short negative phase is arguably the study’s most consequential result. In purebred Holsteins selected for extreme yields, the weeks after calving typically bring a punishing gap between the energy poured into milk and the energy the cow can physically consume, forcing the animal to mobilize body reserves and predisposing her to ketosis, impaired fertility, and other transition disorders. The F1 cows in this study resolved their negative balance within roughly two to three weeks postpartum. The authors attribute this resilience to the combination of moderate milk output, stable intake, and a genetic predisposition toward fat storage inherited partly from the zebu side. Bos indicus cattle and their crosses deposit proportionally more subcutaneous fat, whereas Holsteins accumulate visceral fat and channel nutrients preferentially into the mammary gland, leaving pure Holsteins metabolically far more vulnerable in early lactation.

Body condition data reinforced this picture. The cows averaged a body condition score of 3.7 on the five-point scale just two weeks after calving, climbed to 4.2 by fifteen weeks, and settled at 4.4 by week twenty-eight—a whole-lactation average of 4.1. Body weight rose steadily from around 592 kilograms in early lactation to 695 kilograms in late lactation, with the animals reaching about 726 kilograms at forty-two weeks in milk. Because the heifers had calved at roughly 78 percent of their hypothetical mature weight at thirty months, the researchers conclude that these animals grew faster than the average Brazilian Girolando herd, likely reflecting the standardized genetics and intensive rearing nutrition applied from calfhood onward. Still growing while lactating, they were effectively funding two demanding biological projects simultaneously without apparent metabolic strain.

The partitioning of dietary energy reveals where the calories went. Heat production was the single largest expenditure, consuming 34.1 percent of gross energy intake, with cows losing between 96.1 and 89.0 megajoules per day as heat across the three stages. Fecal energy losses came a close second at 33.2 percent, a figure that reflects the substantial roughage content of the rations, while urinary losses remained a minor and remarkably constant 3.4 megajoules per day. Energy retained in milk accounted for 20 percent of gross intake, declining from 61.2 megajoules per day in early lactation to 46.0 in late lactation as milk yield fell. Notably, and counter to what has been reported for Holsteins, both heat and methane losses declined rather than rose from early to late lactation in these crossbreds, most likely because energy intake itself tapered alongside the falling concentrate proportion of the diet.

The methane numbers carry implications well beyond cattle nutrition. Enteric methane represented 7.6 percent of gross energy intake—a methane conversion factor about one percentage point above the 6.5 percent default that the Intergovernmental Panel on Climate Change assigns to cattle and buffalo. In absolute terms, methane energy losses fell from 22.8 megajoules per day in early lactation to 18.6 in late lactation. The authors urge caution in generalizing the figure, since fiber fractions and feeding level strongly influence rumen passage rate and thus methanogenesis, and their diets contained only about half the concentrate of some comparison studies. Indeed, crossbred cows in comparable trials lost more energy as methane than Holsteins or Jerseys on high-concentrate rations. Still, with livestock methane under intensifying scrutiny as a greenhouse gas, the data identify a concrete research target: understanding and mitigating methane conversion in F1 and other Girolando compositions under tropical feeding systems.

Milk composition adds another dimension to the crossbred’s commercial case. The cows produced milk with an average fat content of 4.66 percent and protein of 3.57 percent, sitting at the upper end of published ranges for Girolando animals and above the breed averages of roughly 3.9 and 3.3 percent. Since pure Holsteins typically produce a larger but skimmer volume, the solids-rich F1 milk can counterbalance the yield gap, particularly attractive for producers diversifying into cheese and other dairy products. Feed efficiency told a similar intermediate story: cows converted each kilogram of dry matter into 1.16 kilograms of milk in early lactation, declining to 0.93 by late lactation, with an overall lactation figure near 1.05—better than Gyr, below elite Holstein, and potentially convergent with both when nutrient availability is not limiting.

Taken together, the study delivers a persuasive argument that F1 Holstein × Gyr cows are a viable and physiologically sustainable option for confined tropical milk production, combining heat tolerance and intake stability with acceptable yields and unusually gentle metabolic transitions. The authors are careful to note the caveats: the favorable energy balance reflects not only genotype but also excellent nutrition and a comparatively late age at first calving, and the pronounced tendency toward over-conditioning in mid-to-late lactation demands careful dietary energy control before subsequent calvings. They also emphasize that comparable measurements under grazing conditions—where most tropical F1 cows actually live—are essential next steps. But as a metabolic portrait of the cow that milks Brazil, the data finally fill in the energy ledger, showing precisely how a hybrid animal manages to give milk, gain weight, stay cool, and recover from calving faster than either of its parent breeds could alone.

Subject of Research: Energy metabolism and partitioning in primiparous F1 Holstein × Gyr dairy cows throughout lactation

Article Title: Unveiling the energy metabolism of primiparous F1 Holstein × Gyr cows throughout lactation

Article References: da Silva, C. S., Rodrigues, J. P. P., Sacramento, J. P., Coelho, S. G., & Campos, M. M. (2026). Unveiling the energy metabolism of primiparous F1 Holstein × Gyr cows throughout lactation. Discover Agriculture, 4(1), Article 296. https://doi.org/10.1007/s44279-026-00774-2

Image Credits: AI Generated

DOI: 10.1007/s44279-026-00774-2

Keywords: dairy cattle, Holstein, Gyr, Girolando, energy metabolism, lactation, tropical agriculture, methane emissions, body condition, feed efficiency, crossbreeding, respirometry