Lifetime Milk Yield Research Articles

Тривалість продуктивного використання корів у стадах української чорно-рябої молочної породи в умовах племінних господарств Тернопільської області

Goal. To study the duration of productive use of cows of Ukrainian black-motley dairy breed in breeding herds of farms of Ternopil region, and to substantiate the principles of breeding and zootechnical work for effective selection of cattle with a projected long term of economic use in the Western region of Ukraine. Methods. Primary zootechnical documentation is studied of experimental farms on the following indicators: life expectancy, economic use and lactation, lifetime milk yield, milk fat yield, and average lifetime fat content in milk, as well as a comprehensive final indicator of average milk yield per 1 day of life, economic life, economic use and lactation (according to the generally accepted zootechnical methods for the period of 2009–2020). Correlation analysis was used to determine the nature, direction and relationship between exterior constitutional characteristics and productivity of cows with indicators of the effectiveness of their lifelong use. Statistical processing of research results and correlation analysis were carried out by methods of variation statistics according to M.O. Plokhynskyi, Ye.K. Merkurieva. Results. The presence is fixed of genetic diversity of cows because determines the longevity of livestock and the possibility of selection for the duration of exploitation of animals. Correlation analysis established the possibility of predicting the efficiency of lifelong use by individual indicators. There is a reliable relationship between the age of the first calving with lifelong milk yield, lifelong fat content in milk, the average duration of lactation, economic use, life. The links between lifelong milk yield and the duration of economic use, life, the average duration of lactation, and indicators of lifelong productivity and economic use are highly reliable. A significant influence of paratype factors on the formation of lifelong milk yield was revealed. Conclusions. The highest on average (among the studied indicators) reliable relationship (relative variability) with the efficiency of lifelong use are the indicators of the age of the first calving, duration of economic use, life, the average duration of lactation.

Lifetime performance and longevity traits in Slovak Spotted dairy cows in dependence on feeding system

Article Details: Received: 2020-10-23 | Accepted: 2020-11-27 | Available online: 2021-01-31 https://doi.org/10.15414/afz.2021.24.mi-prap.114-117 The objective of this study was to analyse eight milk yield and longevity traits in dependence on feeding (grazing) system. Data of purebred Slovak Spotted dairy cows (35,812 heads) culled in the period between 2006 and 2019 were evaluated. Only herds those feeding (grazing) system was known were taken into account. Dairy cows were assigned to four groups: (1) heifers not grazed, cows not grazed (17,628 heads), (2) heifers grazed, cows not grazed (13,056 heads), (3) heifers not grazed, cows grazed (156 heads) and (4) heifers grazed, cows grazed (4,972 heads). The highest average 305-day milk yield (6,139.22 kg) and lifetime milk yield (18,606.78 kg) were found in animals of group (1). Contrariwise, longevity traits were found more favourable in animals of group (4). Their productive life was by 102.78 days longer and average parity was by 0.14 higher in comparison to group (1). The differences between groups were found significant. Keywords: milk yield, longevity, grazing, heifers, cows, Slovak Spotted cattle References Bujko, J. et al. (2020). Changes in production and reproduction traits in population of the Slovak spotted cattle. Acta fytotechnica et zootechnica, 23(3), 161–166, https://doi.org/10.15414/afz.2020.23.03.161-166. Canji, V. et al. (2008). Effect of conformation traits on longevity of cows of Slovak simmental breed . Slovak Journal of Animal Science, 41(2), 83–90. Fuerst–Waltl, B. et al. (2019). Mountain pasturing of rearing stock reduces the culling rist as dairy cows. Animal , 13(1), 209–212, doi: 10.1017/S1751731118001465. Krogmeier, D. et al. (2015). The effect of alpine pasturing of heifers on the longevity and on different yield traits of cows in Simmental and Brown Swiss cattle. Zuchtungskunde, 87(2), 107–119. Petrovic, M. et al. (2009). The effect of systematic factors on milk yield in Simmental cows over complete lactations. Biotechnology in Animal Husbandry , 25(1-2), 61–71, DOI: 10.2298/BAH0902061P . Ludovic-Toma, C. et al. (2017). Comparative study on production, reproduction and functional traits between Fleckvieh and Braunvieh cattle. Asian – Australasian Journal of Animal Sciences , 30(5), 666-671, doi: 10.5713/ajas.16.0588 . SAS Institute Inc.: SAS/STAT ® 9.2User’s Guide, Second Edition , Cary, NC USA, 2009. Strapak, P. et al. (2008). Effect of selected factors on the lenght of productive life of cows. S lovak Journal of Animal Science , 41(2), 77–82. Strapak, P. et al. (2010). Relation of the length of productive life and the body conformation traits in Slovak Simmental breed. Archives Animal Breeding , 53, 393–402. https://doi.org/10.5194/aab-53-393-2010

The effect of dairy heifer pre-breeding growth rate on first lactation milk yield in spring-calving, pasture-based herds

Optimising heifer growth rate may offer an opportunity to improve lifetime milk yield per cow, enhancing the environmental and economic efficiency of dairy farming operations. The effect of dairy heifer pre-breeding average daily weight gain (ADGPB) on first lactation milk yield was investigated. This observational study employed a data set comprising 265 Holstein-Friesian, or Holstein-Friesian-cross-Jersey heifers from seven commercial, spring-calving, pasture-based dairy herds, where the major component of the diet was grazed grass. These were weighed at birth and prior to breeding and ADGPB was calculated. Milk recordings were performed throughout the heifers' first lactation and 305-day yield figures calculated from these records. Yields were corrected to 4% fat and 3.1% protein to create standardised 305-day milk yield (SMY), which was the outcome of interest. Median ADGPB was 0.72 kg/day. Median 305-day yield was 5 967 kg. Linear regression was used to investigate the effect of weight and genetic, age and first calving factors on SMY. Pre-breeding average daily weight gain, age at first calving and predicted transmitting abilities for milk protein production and calving interval were all significant in the final model, which also included the random effects of farm and month of calving within year. ADGPB was quadratically related to first lactation SMY, with an ADGPB of 0.82 kg/day corresponding to the maximum predicted SMY. The model predicted that a heifer growing at 0.82 kg/day would produce 1 120 kg more SMY than a heifer growing at 0.55 kg/day, 218 kg more than a heifer growing at 0.7 kg/day and 103 kg more than a heifer growing at 0.90 kg/day. Manipulation of heifer growth rate may offer a viable method of increasing first lactation milk yield.

Продуктивное долголетие голштинских коров ленинградской популяции при разных способах содержания

To identify the advantages of a tethering system (TS) or loose-housing system (LHS), a comparative analysis of the level of milk productivity and the duration of productive longevity of cows in the Leningrad Region was carried out for a livestock of 4,272 cows that left in 2015–2019. The following indicators were calculated: period of productive use (PPU) – age in days from the first calving to the retirement of the cow, lifetime milk yield (LTMY); milk yield (kg) for 1 milking day, for 1 day of PPU and 1 day of life (Efficiency of Milk Production – EMP) – calculated by dividing lifetime milk yield by the number of milk days, PPU or life. With TS the LTMY is higher by 10,634 kg, which is obtained for 107 additional days of their productive use, milk production for 1 day of milking, the day of use, EMP is higher by 8,2 kg, 6,7 kg and 4,6 kg, respectively, the majority of cows have an EMP level in the ranges of 10,01–15,00 kg of milk (32,0%) and 15,01–20,00 kg (38,2%), and 11,0% of animals have reached an EMP level of more than 20,00 kg of milk. With LHS mainly cows are concentrated in the ranges of 5,01–10,00 kg of milk (43,6%) and 10,01–15,00 kg of milk (46,6%). Desirable cows with LTMY over 30 thousand kg, and in this range, the EMP is almost 10 times higher with TS (43,9 instead of 4,5%). The results obtained cannot be attributed to the advantages of TS. This is confirmed by the great influence of the father on the EMP (factor «Sire» – 0,679) or the inherent genetic potential of productivity, and only by 0,268 system (factor «System of housing») and by 0,296 (factor «Farm») housing conditions on the farm. The «System of housing» influences more on milk yield per 1 day of PPU than on EMP and LTMY (0,342 instead of 0,268 and 0,110, respectively). The effectiveness of LHS is evidenced by the fact that when comparing animals with the same level of EMP under this system, they are used for a longer time and, accordingly, produce more milk per life. So, with a level of 5,01–10,00 kg of milk, cows have a LTMY of 18,1% more with LHS, which were used for 0,54 lactation with PPU for 211 days longer than analogs with TS. A similar trend is observed at the level of 10,01–15,00 kg (+20,8%, +1,17 lact., +461 days) and at the level of 15,01–20,00 kg (+11,3%, +1,18 lact., +499 days). Therefore, for profitable dairy production with a LTMY of more than 30 thousand kg of milk during the PPU of Holstein cows with a LHS, attention should be paid to the level of the inherent genetic potential of productivity (according to the analyzed sample, at least 8000 kg of milk), that is, to select bulls with high breeding qualities.

The effect of holstein bulls’kappa-casein gene genotype on the productive longevity of their female offspring in the republic of Bashkortostan

Increased productivity in the industry can be achieved by breeding for productive longevity through searching and using genetic markers. The study analysed the data of 1476 animals with at least one completed lactation. Depending on the linear affiliation and kappa-casein gene genotype of servicing bulls, their female offspring were divided into 4 groups. The CSN3 A allele frequency in the studied bulls was 81.91%, the CSN3 B allele was 18.09%. The highest frequency of the desired CSN3 B allele in the servicing bulls-producers of the Reflection Sovering line was 20.83%, which is 3.69% more than in the bulls of the Vis Back Ideal line. The animal life length analysis showed that the female progeny of bulls from the Reflection Sovering line (2.46 lactation), especially those with the CSN3 AB genotype (2.59 lactation), had the longest life. The offspring of CSN3AB genotype bulls of the Reflection Sovering line had the highest lifetime milk yield (18490 kg). The CSN3AB genotype cows of the Reflection Sovering line had the highest average milk yield on the 1st day of a cow’s life of 9.05 kg.

Influence of country of origin and lineage on the lifetime milk production of Holstein cows

<b>This work investigated the percentage influence of country of origin and lineage on parameters of lifetime milk production in Holstein cows brought as heifers to Ukraine from Western Europe. The animals were kept untethered in new, modern, uninsulated steel cowsheds in a large dairy complex. Data from the Orsek dairy management system were used to evaluate randomly selected cows of different origins with complete lactation for lifetime milk, fat and protein yield. Despite significant differences in milk productivity between animals depending on their country of origin and line, the share of the influence of these factors was fairly small. Two-way analysis of variance showed that the percentage influence of the line on lifetime milk yield was 5,5%, and its influence on the yield of milk fat and protein was 6,3-7,8%. The percentage influence of the country of origin was even smaller, at 0,5–2,6% (with a greater impact on milk yield). The rather small effect of the factors studied could be due to the influence of environmental factors (feeding and living conditions), which should be investigated in further studies. </b>

Milk productivity of cows of Black-and-White breed depending on the part of Holstein blood

A retrospective analysis of the dynamics of traits of milk productivity of Black-and-White cows with increased the part of Holstein breed blood has been carried out. Two groups have been formed from the number of culling animals of two adjacent generations: the 1st group (basic generation) with the part of Holstein breed blood of 3/4 (75 %) and the 2nd group with the part of Holstein breed blood of 7/8 (87,5 %) per 35 heads in each. As a result, it has been found that cows with the part of blood of 7/8 had the best indicators of milk productivity for I, II and III lactation. They significantly exceeded the indicators of cows with part of Holstein blood of 3/4 in terms of milk yield and yield of milk fat. The decrease in average daily milk yields for months of lactation in high-blooded cows was lower by 3 %, and the indicator of full-competed lactation was higher by 17,8 %. High-blooded animals have been culled out of the herd more intensively. By the end of the third lactation, the livability of livestock in the 1st group was 100 %, and in the second group – 23 %. The best parameters of productive longevity were distinguished by animals of the basic generation with the part of Holstein breed blood of 3/4. They signifi cantly surpassed of high-blooded animals in terms of longevity and period of productive longevity, respectively, by 1109 (P < 0,001) and 739 (P < 0,001) days, and in terms of lifetime milk yield – by 14392 kg (P < 0,001). The increase of the part of the blood of cows to 7/8 was carried out using purebred producers of foreign selection, the new generation of high-blooded animals had a relatively high genetic potential. However, 7/8-blooded cows of Holstein breed used it only by 53,4 %, which was by 24,3 % (P < 0,001) lower than the base generation. Thus, in the current environments of CJSC “Konstantinovo” high-blooded animals of Holstein breed do not suffi ciently realize the genetic potential, and the increase in productivity is associated with the loss of milk due to the decrease in the duration of economic use of animals. Based on this, we propose at the present stage to suspend the upgrading crossbreeding and return to the using Holsteinized sires domestic selection with the part of Holstein breed blood of 75 to 85 %.

Age at first calving in dairy cows: which months do you aim for to maximise productivity?

PICO question
 In dairy cattle, which months should producers target age at first calving in order to maximise milk yield, minimize risk of non-voluntary culling and optimize fertility?
 
 Clinical bottom line
 Category of research question
 Risk
 The number and type of study designs reviewed
 Seventeen papers were critically reviewed: 15 sets of case series, one review of case series and cohort studies and one randomised control trial, summarising over 2.4 million individual cow records
 Strength of evidence
 Strong
 Outcomes reported
 An optimum range of age at first calving (AFC) on dairy farms appears to be 22–25 months inclusive. Lower or higher than this figure can bring lower first lactation 305 day and lifetime milk yields, lower fertility and lower chances of surviving to a second lactation. Achieving an AFC of 22–25 months can bring the highest economic return to dairies
 Conclusion
 Age at first calving is a useful and key performance parameter to measure in dairy cattle. Achieving a range of 22–25 months at first calving can help to optimise both long term milk yield, fertility and longevity within the herd
 
 How to apply this evidence in practice
 The application of evidence into practice should take into account multiple factors, not limited to: individual clinical expertise, patient’s circumstances and owners’ values, country, location or clinic where you work, the individual case in front of you, the availability of therapies and resources.
 Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.
 

The Impact Level of Milk Production on Some Reproductive and Lifetime Milk Yield in Friesian Cows in Egyptian Farms

The Impact Level of Milk Production on Some Reproductive and Lifetime Milk Yield in Friesian Cows in Egyptian Farms

Association between age at first calving and milk production in first lactation on longevity traits in Holstein cows

The objective of this research was to determine the association between age at first calving (AFC) and milk production in the first lactation of longevity traits for Holstein cows. The research was conducted on 2307 cows raised on 4 farms in AP Vojvodina. The cows were culled in the period from 2017 to 2018. The cows belonged to the group of Holstein Friesian breed of cattle. Cow longevity was observed using three parameters: number of lactations (NL), lifetime milk yield (LMY) and length of productive life (LPL). The research involved the influence of the farm on which the animals realized their production, the season of first calving. A mean value obtained for the length of productive life in the analysed population was 1207 days (3.30 years on average). During this period the animals on average realized 2.45 lactations and produced on average 18798 kg milk. All studied traits showed a high level of variability. From these data, the study sought to determine the influence of factors on the traits of longevity, our research present that studied factors showed high statistical significance on these traits except in the case of the season of first calving where a statistical significance effect wasn?t observed. The season of first calving did not affect the animal traits for longevity and, generally, didn?t affect the calving interval. Regarding the obtained correlation data between age at first calving and length of productive life, it can be concluded that belated AFC leads to reduced reproductive performance.

Biophysical qualities of the hoof horn and its influence on cows productive longevity

The main research objective was to study the influence of the hoof shape, hardness and elasticity of the hoofed horn on the cows’ productive use period duration in modern dairy complexes. The research object was black-motley cows, rejected due to limb disease. The shape of the hoof is divided into normal, with angle of 45-55о, sharp – less than 45о and obtuse – more than 55о. In the group of retired cows with the correct shape, there was 76% of animals. Studies have shown that 55.2% of cows had a hoof hardness 80-85 ShA, but the longest period of life was in animals with a score of 91 or more ShA, and the maximum lifetime milk yield with an indicator 86-90 ShA. Most of (61,6%) retired cows had an indicator of hoof horn elasticity 3,1-3,5×1010 Pa. Moreover, the highest rates of productive longevity were observed in cows with hoof horn elasticity 2,6-3,0×1010 Pa. Therefore, for further use, it is desirable to select animals having front wall inclination angle of the hoof 50-550, with hardness hoofed horn 86-90 ShA, and elasticity 2,6-3,0×1010 Pa.

Influence of bulls-producers on productivity and longevity of subsidiaries

The mean group values of phenotypes of the daughters of each bull were determined and taken into account for the milk yield for 305 days of maximum lactation, longevity (the number of full lactations) and life-long milk yield. As the source material, we used the data of pedigree cows of the black-motley breed of SPK Kolginsky. They were estimated 7,468 heads of cows that were left between 2003 and 2018. The highest longevity and the lifetime milk yield were characterized by the daughters of bulls of the line M. Chiftein 95679. An average of 30556.64 kg of milk was received from them for 4.73 lactations. It exceeded the average value in the sample: by longevity – by 0.24 lactation (5.3%), by life-long milk yield – by 351.01 kg (1.1%). In the Vis Beck Aydial 1013415line, in order to increase the period of productive use of cows, the bull Auction 7318 should be preferred. Among bulls of the Reflex Sovering 198998 line, the breeding material of the bull Solo 62181522 should be used more widely. In the Montvik Chiftein95679 line, the best combination of longevity and lifetime productivity indicators were in daughter of the bull Emos 61280669. 
 
 
 

Genetic Assessment for some Productive and Fertility Traits Using Maximum Likelihood (REML) Of Friesian Cows in Egypt

This study aimed to evaluate the genetic improvement program of the Friesian cows. SAS program was used to calculate averages and significant effect, and (REML) program was used to estimate genetic parameters for productive traits lifetime milk yield (LTMY), daily milk yield (DMY), Lactation Length (LL) and Lactation number complete (LNC), and fertility traits days open (DO) and calving interval (CI). The least square means of LTMY, DMY, LL, LNC, DO and CI were 17546 (Kg), 12(Kg), 304 (d), 3.5 (lactations), 78 (d) and 379(d), respectively. The effect of the month, year of calving and age at first calving (AFC) were significant for all the traits except, the farm was non-significant to DMY. Estimates of the heritability (h2a) were 0.09, 0.44, 0.24 and 0.34 for LTMY, DMY, LL and LNC, respectively, whereas 0.13 and 0.17 for DO and CI, respectively. High h2a of productivity traits, particularly DMY, emphasized the possibility of achieving a significant rate of genetic improvement in this trait through selection program. The genetic correlations were positive ranging from 0.02 to 0.76 , except CI with (DMY, LL and LNC ) were negative and ranging from -0.07 to -0.76 . The highest genetic and phenotypic correlation between DMY and LTMY. The low genetic value of these fertility traits reflected the lack of patients' genetic advancement for these traits while, phenotypic correlation estimates were positive except reproductive traits with some productive traits. Repeatability estimates are few and close to the heritability value due to the small presence of permanent environmental variation, confirming the unpredictability of the cow from its current records of fertility traits.

DOCTOR OF AGRICULTURAL SCIENCES Yu. P. POLUPAN – REACHED CREATIVE PRICES AND PRIVACY OF SCIENCE

DOCTOR OF AGRICULTURAL SCIENCES Yu. P. POLUPAN – REACHED CREATIVE PRICES AND PRIVACY OF SCIENCE

THE RELATION OF PRODUCTIVE LONGEVITY OF LITHUANIAN HEAVY DRAFT MARES WITH THE UDDER CAPACITY

complex of ZAO Semenovsky breeding plant. In mares of the Lithuanian breed, the udder capacitywas the highest among the draft horse breeds: the average udder capacity was 3.01±0.04 kg, and the maximum uddercapacity was 4.75 kg of milk.The udder capacity of mares of the Lithuanian heavy draft breed varied during the day, the lactation and theontogenesis of mares, it was determined more by genetic factors - the coefficient of heritability of this trait was 0.60.The maximum duration of economic use of the Lithuanian draft mares was 23 years, during which the maximumlifelong milk yield reached 88138 kg, and the milk yield for the highest lactation was 8576 kg of milk.It was found that the udder capacity is positively correlated with the milk yield of mares. The correlationcoefficient between the udder capacity and the lifetime milk yield of mare of the Lithuanian heavy draft breed waspositive and significant r = +0.67. Studies have been conducted to determine the possibility of using this indicator forthe selection of animals with long-term economic use and a high lifetime milk yield. It was found that it is possibleduring the first lactation to select mares by the udder capacity, distinguishing by the period of economic use and highlifetime milk yield.

INFLUENCE OF INCREASING THE MILK YIELD FOR THE FIRST LACTATION OF THE LITHUANIAN HEAVY DRAFT HORSES ON THEIR PRODUCTIVE LONGEVITY

Horses are late-ripening animals with low fecundity and therefore should be used in dairy horsebreeding for a long time to ensure the profitability of the industry. In Central Russia, mare's milk is produced fromdraft horse breeds, including Lithuanian heavy-draft horses. They are highly productive animals. With intensiveincreasing the milk yield for the first lactation, the lifetime milk yield and the period of productive use may be declined. Studies have shown that the optimal level of increased milk yield for Lithuanian draft mares is 3001-4000 kgof milk. At this level, the mares give the highest possible lifetime yield of 24,403.66 and the highest amount of milkfat and milk protein. If the increase in the milk yield for the first lactation reaches 6000 kg and above, then in maresof the studied breed the period of productive use and the lifetime yield reduce.

The impact of age at the first calving on lifetime milk yield, life span and herd life of dairy cows

The impact of age at the first calving on lifetime milk yield, life span and herd life of dairy cows

ВЛИЯНИЕ ВОЗРАСТА ПЕРВОГО ОСЕМЕНЕНИЯ НА ПРОДУКТИВНОЕ ДОЛГОЛЕТИЕ КОРОВ ЧЕРНО-ПЕСТРОЙ И ХОЛМОГОРСКОЙ ПОРОДЫ

The influence of the age at the first fruitful insemination on the productive longevity of the blackand-white and Kholmogory cows in Udmurt republic was analysed. The study results are presented in the paper. The economic use period of the study cows did not have statistical differences and lasted 3,42–3,43 lactation periods. Black-and-white cows exceeded Kholmogory cows in the lifetime milk yield (by 3416,5 kg), fat content in milk (by 0,47 %) and milk amount in terms of basic standards (by 6317,7 kg) (P > 0,999). The optimal age for the first insemination of black-and-white cows can be considered 16–17 months, since insemination at the specified age ensures highest longevity in cows (3,85 lactations) and the highest lifetime milk yield indices (21347,8 kg), also expressed in terms of basic standards (27065,6 kg). Too early insemination of the black-and-white cows (up to 15 months) is not recommended, as it results in the decreased lifetime milk yields (up to 15491,4 kg), fat and protein content and shortens the economic use period of the animals up to 3,33 lactation periods. The lowest longevity (3,07 lactation periods) was observed in the black-and-white cows inseminated at the age of more than 20 months. The Kholmogory cows demonstrated an increase in lifetime milk yields (1084,5 kg (P > 0,95)) and the economic use period (1,05 lactation period (P > 0,999)) when the age of the first insemination was increased. However, as the fat mass ratio in milk decreased (by 0,06 % (P > 0,999)) and the protein mass ratio in milk fell (by 0,02 % (P > 0,999)), the increase in lifetime milk yield in terms of basic standards resulted from the increase in the age of the first insemination has no significant differences.

Duration of economic use of lithuanian heavy draft stud mares

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.

Effect of age at first calving and other non-genetic factors on longevity and production traits in Holstein cattle under Vojvodina Province condition, Serbia

The effect of age at first calving (AFC) and various non-genetic factors i.e. season of calving, farm and system of housing on longevity and production traits were investigated. Longevity traits were studied using total lifetime (TL), length of productive life (LPL) and number of lactations (NL) while production was researched using lifetime milk yield (LMY). Data of 2037 Holstein dairy cows were provided by the main breeding organizations at the Faculty of Agriculture, University of Novi Sad. The average values and variability of examined traits as well as the effect of factors on longevity and production traits were investigated using fixed effect model by general linear model (GLM) procedure in software package Statistica 13. Results showed highly significant effect of the AFC, calving season and farm, on all studied longevity traits (P less than 0.01), while non- significant effect was expressed on lifetime milk yield (P greater than 0.05). The mean of AFC, TL, LPL, NL and LMY for Holstein cows were 27.3, 67.5, 40.2 months, 2.45 and 18798.0 kg, respectively. The maximum values of LPL, NL and LMY were noticed for cows with age at first calving before 23 months of age. The LPL ranged from 47.88 (AFC less than 23 m) to 35.84 m (AFC>29 m) and declined progressively when the AFC is increased, particularly in cows calving at more than 29 m.