Association of A80V, R25C, AND Y7F leptin gene sites with productive longevity duration in Kholmogory cows

Objective: to study the dependence of productive longevity of cows of black and motley breed on genetically determined factors - linearity and bloodiness in Holstein breed.
 Methods: zootechnical, biological, statistical.
 The materials of the studies were pedigree cards of cows and bulls, bull catalogs, zootechnical reports on pedigree work with the herd, the cattle base of the Grodno region, and also registers of rearing and rearing of the litter.
 To study the effect on the longevity of cows and their lifelong productivity of the "linear accessory" factor, all animals that were eliminated in 2006-2014 were divided into groups according to the lines: Adema 25437, Annas Adema 30587, Vis Eidial 933122, Montvik Chiftein 95679, Nico 31652 , Pabst Governera 882933, Reflection Sovering 198998, S. Sensation 1267271, Hiltes Adema 37910.
 Depending on the bloodiness of the Holstein breed, the animals were divided into four groups: I - up to 25% of Holstein genes, II- 25,0 – 49,9% of the genes of the Holstein genus, III - Holstein blood 50% and more, IV - purebred black-motley cows.
 Indicators of milk productivity (life-time milk yield (kg) and lifetime yield of milk fat (kg), milk yield for 1 day of lactation (kg), total duration of the lactation period (days) were studied in the experimental animals, and the duration of economic use (lactations).
 Main results. The results obtained during the statistical processing of data indicate that the cows belonging to the Pabst Governera line 882933 differed in the longest period of economic use among the abandoned animals. Duration of use in animals of this line was 8.43 lactations, which is more than for cows of other lines at 1,72-6,67 lactation. It should be noted that cows belonging to the Adem 25437 lines (6,71 lactations) and S. Sensation 1267271 (5,49 lactations) were also characterized by a rather long period of economic use.
 Due to the long period of use of the cow, the Pabst Governera line 882933 had the highest indicator of lifelong milk yield – 51535,58 kg of milk and the yield of milk fat – 1914,03. But as for milk for one day of lactation, here the leadership belonged to individuals belonging to the line Vis Eidial 933122 and amounted to 21,19 kg of milk per day. Also, a fairly high indicator of milk yield for one day of lactation was observed in animals belonging to the line Montvik Chiftain 95679 – 21,02 kg of milk.
 As a result of the research it was found that the largest term of economic use was characterized by low-breed hybrids with Holstein breed (up to 25%) – 3,63 lactations. This group of animals exceeded the individuals of the remaining groups by 0,21-0,76 lactations. It is worth noting that purebred black-motley individuals also differed by a long period of productive use – 3,42 lactations.
 Conclusions. Analysis of the impact on productive longevity and indicators of lifetime productivity of the "linearity" factor among abandoned animals in the "Progress-Vertelishki" made it possible to establish the existence of significant differences in the duration of economic use of cows of different linear affiliation. Cows of the Pabst Governera line 882933 – 8,43 lactations, 51535,58 kg of milk and 1914,03 kg of milk fat were distinguished by the greatest period of productive longevity, and also by the highest milk yield and milk fat content. It was established that the crossing of black and white cattle with Holstein breed positively influenced the productive longevity of animals, but on condition that the blood on the improving rock did not exceed 25%. Low-breed hybrids with Holstein breed exceeded the animals of other groups by the duration of their economic use by 0,21-0,76 lactations. Thus, we recommend breeding cows of black and motley breeds in the "Progress-Vertelishki", taking into account the impact on productive longevity and milk productivity of such factors as linearity and bloodiness in Holstein breed.

In pedigree farm of Cherkasy region, in the modern highly mechanized technologies of milk production, research on studying influence of sires’ heredity on the duration of use and lifetime productivity of their daughters was conducted. The research materials were withdrawn livestock of daughters of Ukrainian Black-and-White and Holstein sires in the amount of 784 head. Duration of lactation, milk yield, content and yield of milk fat for the entire lactation were recorded for each lactation. The following indicators were studied: lifetime, duration of economic use, lifetime milk yield, lifetime milk fat yield, average lifetime fat content in milk, average milk yield per day, average milk yield for a day of economic use and the number of used lactations. On assessing lifetime, the best were daughters of Ukrainian Black-and-White Dairy sires with indicators 3589 and 3303 days. A reliable difference in their favor in comparison with the average for the herd was 1351 and 1065 days (P < 0.001). Comparison of progeny of native sires and Holstein sires also showed significant predominance in lifetime of daughters in their favor, which ranged from 373 to 1841 days (P < 0.001), and duration of productive use – from 438 to 1815 days (P < 0.001). Variability in the number of used lactations varied widely from 1.7 to 6.1 units. In the ranking on the ground of number of used lactations the first and second were sires of domestic breeding – Fajans (6.1lact.) and Avans (5.2 lact.). Most daughters of Holstein sires were used less than the average for the herd. Highly reliable negative correlation between milk yield during the first lactation and the use duration indicators, the lack of correlation between the first lactation yield and lifetime yield obtained in our studies on experimental livestock of 784 head, gives grounds to assert that high milk yield during the first lactation leads to reduction in duration of use and does not always guarantee high figures of lifetime productivity. Milk yield for a day of economic use has a high positive correlation with yield in the first lactation (r = 0.438), lifetime milk yield (r = 0.325), lifetime milk fat yield (r = 0.283) and, especially, yield for a day of life (r = 0.701). With traits of lifetime, economic use duration and CEU, milk yield per day of life has slight negative correlation. Thus, according to figures of use duration and lifetime productivity for progeny of estimated sires of different origin, it is possible to make the generalization that improvement of Ukrainian dairy breeds should be based on the best genetic resources of sires of domestic breeding. When you use foreign breeding sires it is advisable to combine their breeding qualities with assessment of longevity. According to the research should make the following conclusions. The duration of use and lifetime productivity of Ukrainian Black-and-White Dairy cows in the breeding herd are determined by of sires’ individual heredity. High level of milk yield during the first lactation in estimated sires’ progeny does not guarantee an increase in traits of economic use and lifetime productivity. Progeny of domestic breeding bulls was better by traits of productive longevity than purebred progeny of Holstein sires.

DAIRY PRODUCTIVITY SAANEN GOATS OF SELECTION OF LATVIA

EVALUATION OF THE FAMILIES OF DAIRY HERD BY THE PRODUCTIVITY AND BREEDING VALUE

Researches results of cows of the Ukrainian Red-and-White lifetime productivity dairy breed on traits of duration of economic use within the limits of an estimation of crossbred genotypes and genealogical formations are resulted. Reliable influence of the conditional share of Holstein breed heredity on the economic use duration and lifetime milk productivity of cows has been established. For the longest time in the herd, crossbred cows with Holstein bloodline of 25.0 % and crossbreeds with heredity of the parent breed up to 50.0 % were used. At the final stage of crossing in animals with blood ratio of 62.5-87.5 %, a noticeable reduction in the duration of economic use was observed. Animals with Holstein bloodlines of 75.0 and 87.5% were inferior to groups of crossbred cows with heredity of 25.0 and 50.0% with reliable difference of 590 and 633 (P<0.001), 432 and 475 (P<0.001) days, respectively. At the same time, from cows with a share of Holstein blood of 87.5 %, the highest lifetime milk yield was obtained with an excess of cows groups of other genotypes by 1250-3260 kg of milk with reliable difference compared to crossbred genotypes with bloodness - 25.0 % (P<0.001), 37.5 (P<0.001), 50.0 (P<0.01) and 62.5 % (P<0.05). The hereditary influence of lines on the indicators of lifetime productivity in intralinear selection and in some variants of interlinear combinations was proved. The influence of genealogical formations on longevity indicators in in-line selection was evidenced by reliable difference between the extreme variants of the assessed lines on the basis of economic use (651 days; P <0.001) and liftime milk yield (14267 kg; P <0.001). According to the results of interline selection in different variants of paternal and maternal lines combinations, significant variability of the offspring obtained from these variants was established, according to the estimated traits of duration of use and lifetume milk production. Cows obtained in all variants of interlinear selection of parental lines Enhancer, Hannover and Valiant with sires of maternal line S. Cavalier have always had high indicators of duration of economic use and lifetime milk productivity.

The development of milk horse breeding in Russia contributes to the high genetic potential of heavy draft stud mares. The Republic of Mari El has been breeding heavy draft horses to produce koumiss since 1977. The efficiency of heavy draft horse breeding depends on the intensity of use of the breeding stock. At the same time the duration of economic use of animals is of great importance as the duration of the use of horses provides not only economic benefits but also the breeding progress of the herd. The studies on duration of economic use of Lithuanian heavy draft stud mares and their lifetime productivity were conducted on the Koumiss farm of ZAO PZ “Semenovsky” of the Medvedevsky region of the Mari El Republic. The studies have shown that the duration of economic use of Lithuanian heavy draft stud mares on the farm is 4, 195 days or 11.5 years on the average. The study of the lifetime productivity revealed that the Lithuanian heavy draft stud mares had a high lifetime milk yield. As a result of the research the significant positive correlation between the duration of use of the mares and their lifetime milk yield was found out. There is a small positive correlation between the duration of economic use and 1-day milk yield of the economic use and 1-day lactation. The analysis of duration of economic use of Lithuanian heavy draft stud mares depending on their father’s genotype has showed that the longest lactation in the herd was among the daughters of stallion Sunkumas 32 – 15 years. Thus, when conducting selection and breeding work, the farms have great possibilities to increase the period of economic use of horses on this farm and increase their lifetime productivity.

There are indicators data of body weight, body parts measurements, reproductive ability, milk production, morphological and functional properties of udder, the duration of use and economic reasons of disposal of Simmental cows in terms of Lviv oblast. It was established that the experimental cows by live weight during their growth in all ages have been prevailing minimum requirements of breed standard. They are marked by peculiar to combined breed type of body structure with well–defined not only milk but also meat forms, they had strong skeleton and were quite tall (withers height – 131.1 cm). However, the width of the breast in most cows, that is not enough for combined breed (on an average 41.4 cm). Simmentals age at the moment of the 1st insemination was 19.7, while during the 1st calving – 29.0 months, the duration of the service–period, depending on lactation, was within 96.8 – 112.0, of inter–calving period – within 381.6 – 396.9 day. They were characterized by an average fertility and high adaptablity. Simmentals milk yield, depending on lactation, was 3026,4–3810,2 kg, fat content in milk – 3.76 – 3.81% and quantity of milk fat 113.6 – 145.0 kg. Cows after the 4th calving had the highest milk productivity. During the all studied lactations cows milk yield and quantity of milk fat predominated breed standard. They had a well developed udder. 68.2% cows after the first calving had cupped udder, 25.9% – wash–tub and 6.9% – round udder. Their intensity of milk yield was 1.53 kg/min. Simmental cows duration of economic use in the conditions of Lviv oblast was 1.904.1 day or 5.3 lactations, lifetime yield – 18011, lifetime quantity of milk fat – 688 kg. Most reasons for dropped out of the herd was dysfunction of reproduction (35.7%) and low productivity (21.3%).

THE INFLUENCE OF SIRES ON MILK YIELDS AND ITS QUALITY IN STALL HOUSING OF COW

The purpose of research is to study, systematize and summarize the available scientific data on the effect of the leptin gene on the duration of economic use of cattle over the past ten years. This paper presents the results of scientific research on the effect of polymorphisms A80V, Y7F and R25C on the duration of use of animals in agriculture. Polymorphisms R25C and Y7F occur in the second, and A80V – in the third exon of the leptin gene. Research has linked the R25C site to milk protein content, milk fat content, calving ease, and pregnancy duration. The CC genotype is associated with a greater risk of culling in cows. The Y7F site is associated with animal viability, and the FF genotype has a higher risk of culling. The LEP-A80V site affects the duration of animal management and the level of profitability. Cows with the VV genotype have a higher risk of culling than cows with the AA genotype. Assessment of the influence of the leptin gene must be carried out comprehensively across all loci, and not just one. Assessing the combined effect of a gene at three loci allows for a more refined analysis of the animal’s potential. Studies show that the YY genotype predominates at the Y7F site, and genotypes with the F allele are washed out of the population. Most often in domestic farms, the heterozygous genotype of the R25C site is found, but the RR genotype has a positive effect on the longevity of animals. Genotypes AA and AV are more common on the A80V site, the frequency of occurrence of the unfavorable genotype VV is lower. Thus, studying the effect of leptin gene polymorphisms on the economic use of cattle is an important area of scientific research in agriculture. Research results make it possible to predict the duration of use of animals and increase the profitability of agricultural enterprises.

EFFICIENCY OF IMPORTED COWS LIFETIME USE

The studies were conducted on high-producing cows of Precarpathian innerbreed type of Ukrainian Red-and-White Dairy cattle and their progeny, according to zootechnical accounting in private farm enterprise "Mamayivske" in Kytsman district of Chernivtsi region. It was established that during the period from 1995 to 2010 the farm had 20 cows with milk yields over 8000 kg. The highest milk production by the best lactation had cows Maratka 3235, Vorovka 5982 and Chaika 3839, their milk yields were 10586; 9380 and 9008 kgrespectively, fat content in milk – 3.61, 3.79 and 3.77% and fat yield – 382.2, 355.5 and 339.6 kg. The cows had the highest milk yields mostly during the third lactation, and milk yields on average reached record in 3.85 lactations.
 High-yielding cows belonged to 5 bloodlines: R. Sovering 198998, P. Astronaut 1458744, R. Citation 267150, Rigel 352882 and Hanover 1629391. The most numerous one was Astronaut bloodline (11 cows). Daughters of Tyulpan 7451 (R. Sovering bloodline) had the highest level of milk production during the best lactation. They predominated in milk yield during the best lactation over Gybrid’s daughters (Citation bloodline) by 156 kg, T. Tourist’s daughters (Rigel bloodline) by 401 kg, Sekret’s daughters (P. Astronaut bloodline) by 473 kg and M. G. Horizont’s daughters (Hanover bloodline) by 812 kg , by fat yield – by 4.6, 8.6, 9.9 and 26.8 kg, respectively but they were inferior by fat content in milk by 0.02, 0.07, 0.09 and 0.04%. Sekret’s daughters had higher fat content in milk. By this trait, they predominated over Hybrid’s daughters by 0.07, T. Tourist’s daughters – by 0.02 and M. G. Horizont’s daughters – by 0.05%. The average breeding value of bulls, daughters of whom had milk productivity of more than 8000 kg, was +276 kg.
 The highest milk yields were in cows whose mothers belonged to P. Astronaut and Hanover bloodlines and fathers – to R. Sovering bloodline (daughters’ milk yield was 9303 and 9008 kg respectively). High milk yield (8842 kg) also was in cows whose mothers belonged to P. Astronaut bloodline and fathers – to R. Citation bloodline. The best cows by fat content in milk were obtained from a combination of bloodlines V. Ideal – P. Astronaut (3.80%), Rigel – Rigel (3.80%), V. Ideal – Rigel (3.78%) and V. Ideal – Rigel (3.78%).
 Coefficients of repeatability for milk production decreased with increase in period between the comparable lactations. By milk yield for I-VI and the best lactations they were within 0.206-0.495, and by fat content in milk – within 0.337-0.469.
 The better daughters by milk yield not always were obtained from high-yielding cows and, on the contrary, the worse ones – from low-yielding cows. Most cows with high milk yields were from mothers with yields not exceeding 6000 kg of milk, and only with average milk performance of mothers not more than 7281 kg of milk, their daughters predominated in milk yields. With the increase in average productivity of mothers to 8456 kg of milk or more, daughters were inferior to their mothers by1180-3454 kg of milk, but, in all cases, they had a higher milk yield than the average for the herd.
 Positive correlations were found between mothers' milk yield and milk yield, fat content in milk and fat yield of their daughters, but their values partly depended on mothers’ productivity. The highest correlation coefficients between productivity of daughters and mothers were observed at the mothers’ yields not higher than 6999 kg (r = 0.221-0.273), and the lowest – at mothers’ yields over 9,000 kg (r = 0.155-0.182).
 It was found that bull Arbat 1577, estimated on milk production in 69 daughters, had the highest breeding value. The rank of its breeding value was P5 (improver "excellent"). Cows Maratka 3235 (+3204 and +1860 kg), Krona 8490 (+2202 and +1315 kg) Vorovka 5972 (+1710 and +1121 kg), Kava 5450 (+1626 and +1004 kg) Shchoka 5870 (+1602 and +937 kg) had the highest breeding value in terms of best lactation and based on three sources of information, respectively.

The productivity cow dairy breed largely depends on the careful evaluation and selection of animals by milk production and the type of exterior. The estimation of animals by measuring of body plays an important role in plant-breeding work in the process of further improvement of the newly formed Ukrainian dairy breeds by the type. It’s because exterior is one of the main signs of breeding dairy cattle together with indicators of milk production, reproductive ability and productive longevity.
 The aim of research was to investigate the formation of milk productivity of cows black and white dairy cattle based on their body measurements after the first calving.
 The research was done on animals Ukrainian black-and-white dairy breed in the «Milk River» farm in the Sokal and Brody offices breeding reproducers «Breeder» Lviv region and plant-breeding «Yamnytsya» Ivano-Frankivsk region.
 The body measurements of first calving cows (height at withers and depth of chest, breast width, chest girth, scythe body length, the width of the pelvic bones and metacarpus circumference cow) and milk productivity (the milk yield, fat content in milk and milk fat) cows first, second, third
 and better lactation were studied by the materials zoo technical accounting. The force of influence on performance metrics was calculated by Single-factor disperse analysis method. The results of research were treated by variational statistics by G.F. Lakin.
 Established that the milk yield of cows Ukrainian black-and-white dairy cattle depends on body measurements after the first calving. The cows Ukrainian black-and-white dairy breed in Western Ukraine that after the first calving had a height at the withers 134-136,9 cm, depth of chest – 76 cm or more, chest width – 47 cm or more, chest girth by shoulder blades – 196-203,9 cm, scythe body length – 160-164,9 cm, the width of the pelvic bones – 53 cm and metacarpus circumference cow –19-20,4 cm, are the most productive.
 Animals with these measurements of the body most of the largest number of yield milk and milk fat had probable advantage over cows with other indicators of these measurements. By the fat
 content in milk by the first, second, third and better lactation there was no significant difference between animals with different body measurements after the first calving in most cases.
 Among the studied parameters milk productivity of cows and measurements of their bodies after first calving we found varying strength and direction of correlation. The correlation coefficients between body measurements firstborns and yield milk by the first, second, third and better lactation were positive and depended on measurements and lactation ranged from +0,297 to +0,478.
 Between such measurements of firstborns, as the height at the withers, the depth of chest, width of chest, chest girth in blades, the width of the pelvic bones and with fat content in milk for the first, second, third and better lactation correlation coefficients were though low, but positive, and dependently on measurements and lactation were within +0,026 – +0,109. The correlation coefficients between the oblique body length after the first calving cows and fat content in milk were negative (-0,045 – -0,005) and between metacarpus circumference and fat ranged from negative to positive values (-0,038 – +0,017).
 The correlation coefficients between measurements body in firstborn and milk fat yield in the first, second, third and better lactation were positive and dependently on measurements and lactation ranged from +0,288 to +0,473.
 The likely positive correlation coefficient between soundings article body and yield milk and milk fat yield indicates that selection of cows by exterior will ensure the effectiveness of selection by milk productivity.
 The impact of body measurements cows after first calving on the milk yield value dependently on lactation yield was 7,6-22,9 %, on the yield of milk fat – 7,1-22,9 %. The greatest influence on these indicators were height at the withers, the depth of the chest, chest girth shoulder blades and scythe body length, somewhat lower impact had breast width and the width of the pelvic bones and lowest – metacarpus circumference.
 The impact of body measurements cows after first calving on the fat content in milk was negligible and, dependently on measurements and lactation ranged from 0,1 to 1,6 %.

The main goal of dairy breeds selection should be improving breeding and productive qualities of animals under modern conditions. The majority of farms, using native breeds to produce milk, has created optimal conditions for keeping and feeding, selection and matching, growing of replacements etc. Further improvement of created native dairy breeds for economically useful traits occurs at total use of purebred Holstein bulls (semen) of foreign selection. In order to realistically assess milk productivity (milk yield, fat content in milk and fat yield) of Ukrainian Black-and-White and Red-and-White Dairy cows should be conducted a comparative analysis of Holstein cows under the same conditions of feeding and keeping.
 It was established that Ukrainian Red-and-White Dairy cows were characterized by the highest milk yields for 305 days of all lactations, taken into account, the among three investigated breeds. Their milk yield during the first lactation was 5933 kg of milk, during the second – 6393 kg, the third – 6391 kg and during higher lactation – 6650 kg. Ukrainian Black-and-White Dairy cows were second by milk yield (except for the second lactation), during the first lactation – 5932 kg of milk, the third – 6462 kg and higher – 6541 kg, and Holstein cows were third, during the first lactation – 5794 kg of milk, the second – 6381 kg, the third – 6335 kg and higher – 6469 kg.
 The fat content was almost the same and varied within 3.49-3.58% in milk of Ukrainian Red-and-White Dairy cattle, 3.50-3.60% in milk of Ukrainian Black-and-White Dairy cattle and 3.50-3.56% in Holsteins’ milk. The difference between the breeds was within 0.01-0.04%.
 All the investigated breeds had predominance in fat yield for three lactations over standards of these breeds: Ukrainian Red-and-White Dairy cows from 75.1 to 93.4 kg, Ukrainian Black-and-White Dairy cows – 75.1-89.0 kg respectively and Holstein cows – 41.9-60.2 kg.
 It was found different level of positive correlation between milk yield and fat yield in all the cases and high correlation (r = 0.604-0.921, P < 0.001) in five cases (41.7%)
 Negative correlation coefficients indicate that selection of animals to higher milk yield in the herd will decrease the second trait – fat content in milk. Positive and highly significant correlation between milk yield and fat yield indicates that selection of cows in the herd to higher milk yields will increase fat yield.
 It was revealed that bulls were among the factors impacted the milk productivity (milk yield, fat content, fat yield) of three investigated breeds. So, the force (η²x) of father’s impact on milk yield was15.4-47.9%, fat content – 22.0-43.4% and fat yield – 14.9-47.7% taking into account a lactation and a breed. The force of lines impact (η²x) was second; it was on milk yield 6.1-24.5%, fat content – 4.1-17.1 and fat yield – 5.8-23.5%. The force of breeds impact (η²x) was last; it was on milk yield 0.3-2.9%, fat content – 0.2-0.3% and fat yield – 0.6-2.7%.
 So, the comparative studies of milk productivity of Ukrainian Red-and-White and Black-and-White Dairy cattle with Holsteins indicate that under similar conditions of feeding and keeping, these native breeds can compete with Holstein cattle. The milk yield for 305 days of higher lactation was 6650 kg of milk in Ukrainian Red-and-White Dairy cows, 6541 kg in Ukrainian Black-and-White Dairy cows and 6469 kg in Holsteins.
 It was found the inverse correlation r = -0.025-0.316 between milk yield and fat content in milk in most cases. Selection and matching of animals in the herd should be carried out simultaneously on these traits. It was found positive repeatability of milk yields between the first and second, the third and higher lactations (rs = 0.036-0.741), indicating the reliability of forecasting increase in milk productivity during the next lactations in all herd. Bulls have the greatest impact (η²x) on milk productivity among the factors taken into account: milk yield – 15.4-47.9%, fat content in milk – 22.0-43.4% and fat yield – 14.9-47.7%.

Study aims were to investigate associations of hyperketolactia (HYKL) status of Holstein dairy cows between 6 and 60 d in milk (DIM), defined by milk acetone (mACE) and β-hydroxybutyrate (mBHB) content, with daily milk yield and composition. Milk samples (∼5.0 million) were collected over a 5-yr period (2014-2019) within the milk recording system in Poland. Concentrations of mACE and mBHB determined by Fourier-transform infrared spectroscopy were used to categorize samples into 4 ketolactia groups. Based on threshold values of ≥0.15 mmol/L mACE and ≥0.10 mmol/L mBHB, ketolactia groups were normoketolactia (NKL; mACE <0.15 mmol/L and mBHB <0.10 mmol/L), BHB hyperketolactia (HYKLBHB; mACE <0.15 mmol/L and mBHB ≥0.10 mmol/L), ACE hyperketolactia (HYKLACE; mACE ≥0.15 mmol/L and mBHB <0.10 mmol/L), and ACE and BHB hyperketolactia (HYKLACEBHB; mACE ≥0.15 mmol/L and mBHB ≥0.10 mmol/L). To investigate ketolactia association with production outcomes, a linear model was developed, including ketolactia group, DIM, parity, their interactions, year-season as fixed effects, and random effects of herd and cow. Among all milk samples, 31.2% were classified as HYKL, and of these, 52.6%, 39.6%, and 7.8% were HYKLACEBHB, HYKLBHB, and HYKLACE, respectively. Ketolactia groups differed for all traits studied in all parities and DIM. Among HYKL groups, lowest milk yield was found in HYKLACEBHB cows, except for 6 to 30 DIM in first- and second-lactation cows. Milk yield of HYKLBHB cows was higher than that of NKL cows until 20 to 30 DIM, and then it was lower than NKL cows. Milk yield of HYKLACE cows was mostly lower than NKL cows. Energy-corrected milk (ECM) yield of HYKLACEBHB cows was higher than that of NKL cows until 30 to 35 DIM for second lactation and third lactation or greater, and in the whole study period for first lactation. The yield of ECM for HYKLBHB cows was mostly higher than that of NKL cows, whereas HYKLACE cows had higher ECM than NKL cows until 15 to 25 DIM and then was lower for the HYKLACE group. Milk composition differed among HYKL groups. Highest milk fat (MF) and lowest milk lactose (ML) contents were observed in HYKLACEBHB cows. Cows in HYKLACEBHB and HYKLBHB groups had higher MF and lower milk protein (MP; except in 6-8 DIM in first lactation) and ML content than NKL cows. Milk fat content was higher in HYKLACE than NKL cows in first lactation and during the first 30 to 40 DIM in older cows. Lactose content was lower in HYKLACE than in NKL cows within 30 to 40 DIM; afterward it was higher in NKL cows. Lower MP content was found in HYKLACE than in NKL cows, except during 6 to 9 DIM for cows in first lactation and third lactation or greater. In conclusion, HYKL is associated with altered milk production in all parities, but a range of these negative relations depends on ketone status addressing both ACE and BHB contents. Further research is needed to ascertain underpinning biochemical defects of HYKL from elevated ACE, alone or in combination with BHB, during early lactation.

The cost of being early or late: Biological and economic outcomes of age at first calving in dairy buffaloes.