Season Of Calving Research Articles

Реалізація генетичного потенціалу продуктивності корів української чорно-рябої молочної породи залежно від сезону отелення в умовах степової зони

The purpose. To investigate influence of season of calving of cows upon realization of genetic potential of their productivity. Methods. Analysis of variance of attributes of milk yield, correlative interaction of breed with amount of lactations. Results. Implementation of genetic potential of productivity of cows of Ukrainian black-motley dairy breed in conditions of steppe zone of Ukraine with optimum toughness and stability of lactation depends on season of their calving. These indexes can be used also as criterion of conformity of ecological conditions to that genotype, and divergence specifies an opportunity of the subsequent selection operation. Conclusions. In steppe zone of Ukraine the genetic potential of productivity with optimum toughness and stability of lactation is more full manifested at calving cows of Ukrainian black-motley dairy breed in I and IV quarters of year.

Dairy production and sources of cellular variability of milk of cow's in two large farms in semi-arid environment (Tunisia coastal)

This investigation, referring to a description of the Individual Counts Cellular (CCI) of milk, accompanied by an analysis , so some quantitative and qualitative milk parameters that a number of physiological and zootechnical factors of cellular evolution, was performed on two large cattle farms conducted in semi-arid coastal enviroment (region of Sousse, Tunisia), subject tri-daily in mechanical milking room. It is especially striking that the arithmetic mean (MA) of the CCI cows's was 371000 cell. / ml, while the geometric mean (MG) of the CCI cows's was only 107500 cell. / ml. The median was 73,000 cell. / ml, value close to the MG and widely spaced from the MA, thus revealing the usefulness of the MG. A great heterogeneity of cell quality of the milk was noted, however, without clearly identify correlation with the chemical composition of milk. In two large herds followed, the variation of CCI was inversely related to dairy production. On the other hand, the CCI found an increases with the rank of lactation, the stage of lactation and the spring season of calving.

Efectos No Genéticos sobre la Reproducción en Vacas Mestizas con Predominio Bos indicus en el Municipio de Arauca, Colombia

<p>Los factores no genéticos o ambientales son la principal causa de variación de los parámetros reproductivos en vacas mestizas en regiones tropicales. El objetivo fue determinar algunos factores no genéticos que afectan la edad al primer parto (EPP) y el intervalo entre partos (IEP) en vacas doble propósito en el municipio de Arauca, Colombia. Se analizó la información de 176 y 110 datos de EPP e IEP de vacas con predominio de razas <em>indicus</em>. Se consideró el efecto de los factores fijos para EPP: Finca (FIN: 1, 2, 3), época de primer parto (EPPP: seca, lluviosa), año de primer parto (APP: 1992….2011), sexo de la cría (SCR: M, H). Para IEP: finca (FIN), época de intervalo entre partos (EIP), año de intervalo entre partos (AIEP), sexo de la cría (SCR) y numero de parto (NP: 1…5). Los datos se analizaron utilizando los procedimientos GLM de SAS y para la comparación de medias se usó el test Duncan con un nivel de significancia 5%. La media estimada para la EPP fue de 1243,56±160,3 días y para el IEP fue de 608,03 ±165,4 días. La FIN y el APP fue un factor de variación significativo (p<0,05) para la EPP, mientras que El NP y el AIEP fue un factor de variación significativo (p<0,05) para el IEP. Los demás factores no fueron significativos (p>0,05) para los parámetros analizados. Se concluye que la influencia ambiental sobre los parámetros reproductivos depende de la región donde se localice el sistema de producción y se relaciona con el manejo técnico y productivo propio de cada finca. Los valores encontrados se consideran adecuados para el sistema de producción dada las condiciones de manejo en la sabana inundable y está dentro del rango establecido para los grupos raciales con predominio de las razas cebuinas.</p>

Environmental Factors Affecting Some Productive and reproductive Traits in Egyptian Buffaloes

This study was conducted to evaluate the effect of some environmental factors on milk production in Egyptian buffaloesand the effect of parity and season of calving on calving interval and days open. There was a significant effect of parity(P ≤ 0.05) on 305day milk yield, while season of calving had a highly significant effect (P ≤ 0.01) on 305day milk yield.Animals with age at first service less than 21 months and age at first calving less than 35 months had higher milk yieldthan other animals (2489.5 and 2526.7 kg, respectively). With increasing days open, milk production increased so animalshad more than 160 days open produced 2757.8 kg milk. Milk yield in winter (2600.5 kg) was higher than in summerseason (2441.5 kg). Animals which conceived four or more services produce more milk yield (2529.8 kg). Season ofcalving had a significant effect (P ≤ 0.05) but parity had a highly significant effect (P ≤ 0.01) on calving interval and daysopen. There was direct relationship between milk yield with each of calving interval and days open. Animals that gavemore than 3000 kg showed the maximum calving interval and days open (14 months and 111.8 days, respectively)

Evaluation of factors associated with immunoglobulin G, fat, protein, and lactose concentrations in bovine colostrum and colostrum management practices in grassland-based dairy systems in Northern Ireland

The objectives of this study were to investigate colostrum feeding practices and colostrum quality on commercial grassland-based dairy farms, and to identify factors associated with colostrum quality that could help inform the development of colostrum management protocols. Over 1 yr, background information associated with dairy calvings and colostrum management practices were recorded on 21 commercial dairy farms. Colostrum samples (n = 1,239) were analyzed for fat, protein, lactose, and IgG concentration. A subset was analyzed for somatic cell count and total viable bacteria count. Factors associated with nutritional and IgG concentrations were determined using both univariate and multivariate models. This study found that 51% of calves were administered their first feed of colostrum via esophageal tube, and the majority of calves (80%) were fed >2 L of colostrum at their first feed (mean = 2.9 L, SD = 0.79), at a mean time of 3.2 h (SD 4.36) after birth, but this ranged across farms. The mean colostral fat, protein, and lactose percentages and IgG concentrations were 6.4%, 14%, 2.7%, and 55 mg/mL, respectively. The mean somatic cell count and total viable count were 6.3 log10 and 6.1 log10, respectively. Overall, 44% of colostrum samples contained <50 mg/mL IgG, and almost 81% were in excess of industry guidelines (<100,000 cfu/mL) for bacterial contamination. In the multivariate model, IgG concentration was associated with parity and time from parturition to colostrum collection. The nutritional properties of colostrum were associated with parity, prepartum vaccination, season of calving, and dry cow nutrition. The large variation in colostrum quality found in the current study highlights the importance of routine colostrum testing, and now that factors associated with lower-quality colostrum on grassland-based dairy farms have been identified, producers and advisers are better informed and able to develop risk-based colostrum management protocols.

Dairy cattle industry and genetic improvement programs in Thailand

The objective of the present study was to estimate genetic parameters and evaluate the genetic trends of 100-day milk yield (MY), fat percentage (FP) and protein percentage (PP) in three government dairy cattle farms in Thailand, located in the north and north-east of the country. The data consisted of records from 1745 first-lactation cows that calved between 1986 and 2015, which were the progeny of 287 sires and 1237 dams. Most of the animals were crossbred Holstein-Friesian with native or zebu animals. The total number of animals in the pedigree was 4753. Univariate and bivariate linear mixed models were used to estimate genetic parameters and breeding values by using ASReml-R. The fixed effects in the model were herd, year of calving, season of calving, breed group and the interaction between year and season of calving, and the random effects were animal and residual. All fixed effects had significant effects on the three traits, except breed group. The estimated heritabilities for MY, FP and PP were 0.242 ± 0.061, 0.066 ± 0.048 and 0.329 ± 0.072 respectively. The genetic correlation for MY and FP, MY and PP, and FP and PP were 0.219 ± 0.352, –0.271 ± 0.177 and 0.452 ± 0.255 respectively. The genetic trends based on estimated breeding values over year of birth did not show consistent improvement in all three traits, although there was a slight declining trend in MY in the later years.

Effect of Non Genetic Factors on the Concentration of Immunoglobulin G in the Colostrum of Murrah Buffaloes

Individual variation in Immunoglobulin contents of first colostrum may be responsible for differences in susceptibility of calves to infections. The present study was undertaken to analyze effect of various non genetic factors on the concentration of immunoglobulin G in the colostrum dams before first milking. Colostrum (before first milking) of 40 newly parturated Murrah buffaloes maintained at Livestock Production Management (LPM) Section of IVRI, Izatnagar, was digested with rennet and then analyzed by indirect ELISA. Records pertaining to calving including parity of dam (1 through 8), season of calving (rainy, autumn and winters), time of calving (day and night) and volume of colostrum (at first milking) were collected and analyzed by least square analysis and regression analysis. Levels of IgG in buffalo colostrum (before first milking) estimated by Indirect ELISA ranged from 11.22 to 185.1 mg/ml and mean IgG concentration in colostrum was 51.71 ± 5.99 mg/ml. The effect of parity of dam and colostrum volume (first milking) on colostral IgG concentrations was found to be significant at p

Environmental and maternal factors associated with gross placental morphology in dairy cattle.

This article reports on a study of gross placental morphology of 282 expelled placentas from 89 primi- and 193 multiparous Holstein dams immediately after calving and examines associations with environmental factors such as typical herd features and season of calving, and maternal factors such as age at calving, level of milk yield at conception and cumulative amount of milk produced during gestation. The highest correlation between calf measurements and placental characteristics was found between the weight of the calf and the total cotyledonary surface (r=.643; p<.001), confirming the high importance of the cotyledonary surface available for nutrient transfer to the developing foetus. Younger age in adolescent and smaller heart girth in multiparous dams were associated with a higher cotyledon number, suggesting placental compensation in dams with lower capacities in terms of dry matter intake. No significant association between milk yield during gestation in multiparous animals and gross placental morphometrics could be detected, indicating that factors such as the amount of milk produced during gestation affect placental development less than foetal weight close to term. Therefore, placental growth may be sustained at the expense of other tissues in an attempt to maintain pregnancy and minimize the adverse consequences for the foetus. This study offers evidence concerning factors affecting the placental surface size for nutrient transfer from dam to calf in dairy cattle based on gross morphometrics, but needs confirmation from studies in which this surface size is more profoundly assessed by measuring the branches present in the cotyledonary villi.

Effects of the presence of grazing-experienced heifers on the development of foraging behavior at the feeding station scale for first-grazing season calves.

In this study, effects of grazing-experienced heifer presence on foraging behavior development at the feeding station (FS) scale for first-grazing season calves were determined. A group of four calves grazing alone (C), and another comprising four calves (Wc) and three grazing-experienced heifers (Wh), were alternately stocked every day for 2h on the same pasture for 26days. The foraging time budget for Wc was significantly longer than that for C (P<0.05) on day 7, and was similar to that for Wh on all days. Bite rate per FS was significantly higher for Wc (15.5 bite/min) than for C (13.2 bite/min) from day 1 to 14 (33.4 vs. 29.0 bite/min, respectively; P<0.01) and significantly lower than that for Wh on all days. The number of steps taken between adjacent FSs by Wc (4.7) was significantly lower than that for C (7.2) on days 1 and 14 (2.1 vs. 2.9 steps, respectively; P<0.01) and was similar to Wh on all days. This suggests that grazing-experienced heifers have positive effects on the foraging behavior development of new-season grazing calves through 14days after the start of stocking.

Performance appraisal and genetic parameter estimation of all lactation traits in Karan fries cattle

Present investigation comprehends the study of the effect of genetic and non-genetic factors and estimation of genetic parameters of Karan Fries cattle with respect to production and reproduction traits across all lactations. Data consisted of a total of 5878 lactation records on 1988 cows over a period of 32 years (1981 to 2012), maintained at ICAR-NDRI, Karnal. Overall least-squares means for CFS(days), SP(days), LL(days), CI(days), 305MY(kg), TMY(kg), MY/LL(kg/days), MY/CI(kg/days) and DPR were found to be 78.21±1.59, 115.46±2.14, 326.57±2.60, 403.91±2.54, 3634.78 ± 30.91, 3976.77 ± 41.03, 12.19 ± 0.08, 10.28 ± 0.08 and 0.37 ± 0.80, respectively. Both production and fertility traits were significantly affected by different factors viz. season of calving, period of calving, parity and genetic group. LSANOVA heritability estimates of SP, CI, LL, CFS, DPR, 305MY, TMY, MY/LL, MY/CI were 0.18±0.08, 0.15±0.07, 0.11±0.05, 0.10±0.09, 0.07±0.07, 0.39±0.09, 0.26±0.07, 0.35±0.08 and 0.42±0.10, respectively. Heritability estimates indicated that fertility traits were less affected by additive gene action. Genetic correlation estimates indicated unfavourable positive correlation between fertility and production traits.

Development of genetic and genomic evaluation for wellness traits in US Holstein cows

In March 2016, Zoetis Genetics offered the first commercially available evaluation for wellness traits of Holstein dairy cattle. Phenotypic data on health events, pedigree, and genotypes were collected directly from producers upon obtaining their permission. Among all recorded health events, 6 traits were chosen to be included in the evaluation: mastitis, metritis, retained placenta, displaced abomasum, ketosis, and lameness. Each trait was defined as a binary event, having a value of 1 if a cow has been recorded with a disorder at any point during the lactation and zero otherwise. The number of phenotypic records ranged from 1.8 million for ketosis to 4.1 million for mastitis. Over 14 million pedigree records and 114,216 genotypes were included in the evaluation. All traits were analyzed using univariate threshold animal model with repeated observations, including fixed effect of parity and random effects of herd by year by season of calving, animal, and permanent environment. A total of 45,425 single nucleotide polymorphisms were used in the genomic analyses. Animals genotyped with low-density chips were imputed to the required number of single nucleotide polymorphisms. All analyses were based on the single-step genomic BLUP, a method that combines phenotype, pedigree, and genotype information. Predicted transmitting abilities were expressed in percentage points as a difference from the average estimated probability of a disorder in the base population. Reliabilities of breeding values were obtained by approximation based on partitioning of a function of reliability into contributions from records, pedigree, and genotypes. Reliabilities of genomic predicted transmitting abilities for young genotyped and pedigreed females without recorded health events had average values between 50.2% (displaced abomasum) and 51.9% (mastitis). Genomic predictions for wellness traits can provide new information about an animal’s genetic potential for health and new selection tools for dairy wellness improvement.

Genetic analysis of first lactation production and fertility traits in Karan Fries cattle

The present investigation encompasses the genetic analysis of first lactation production and fertility performance of Karan Fries cattle. Data were collected on 1,988 cows maintained at National Dairy Research Institute (NDRI), Karnal, Haryana over a period of 34 years (1978 to 2012). Least squares analysis was carried out to study the effect of non-genetic factors, viz. season of first calving (SC), period of first calving (PC), genetic group (GG) and age at first calving group (AFCG) on first lactation fertility and production traits. Least squares means of age at first calving (AFC), first calving to first service (FCFS), first service period (FSP), first lactation length (FLL), first calving interval (FCI), first lactation 305 day or less milk yield (F305MY), first lactation total milk yield (FTMY), milk yield per day of first lactation length (MY/FLL), milk yield per day of first calving interval (MY/FCI) and first lactation daughter pregnancy rate (FDPR) were 957.48±6.54 days, 79.46±3.58 days, 130.03±4.43 days, 347.02±5.51 days, 415.47±5.21 days, 3,213.91±47.61 kg, 3,760.49±74.27 kg, 10.49±0.12 kg/day, 9.14±0.13 kg/ day and 0.33±1.42, respectively. Overview of least squares analysis regarding first lactation traits indicated that most of the non-genetic factors excepting AFC group, significantly affected the performance of the animal. Results revealed the superiority of F1 over other GG of Karan Fries cows indicating a significant effect of heterosis. Heritability estimated by both analysis of variance and average information restricted maximum likelihood methods indicated that the fertility traits were less affected by additive gene action; the estimates for production traits indicated higher role of additive gene action. Both phenotypic and genetic correlation estimates indicated antagonistic association between fertility and production traits.

Impact of environmental factors on milk β-hydroxybutyric acid and acetone levels in Holstein cattle associated with production traits

The objective of this study was to estimate the environmental factors affecting milk β-hydroxybutyric acid (BHBA) and acetone (Ac) concentrations in Holstein cattle. A total of 264,221 test-day records collected from the Korea Animal Improvement Association (KAIA) during the period of 2012 to 2014 were used in this study. Analysis of variance (ANOVA) was performed to determine the factors significantly affecting ketone body concentrations. Parameters considered in the model were season of test, season of calving, parity, lactation stage, and milk collecting time (AM and PM). According to the ANOVA, the R² for milk BHBA and Ac were 0.5226 and 0.4961, respectively. ‘Season of test’ showed a considerable influence on ketone body concentration. Least square (LS) means for milk BHBA concentrations was the lowest (39.04 μM) in winter while it increased up to 62.91 μM in summer. But Ac concentration did not significantly change along with ‘season of test’. The means of milk BHBA and Ac concentrations were high at first lactation stage, low around second lactation stage, and then gradually increased. Cows milked in the morning had lower mean BHBA and Ac concentrations (48.49 μM and 121.69 μM, respectively) in comparison to those milked in the evening (53.46 μM and 130.42 μM, respectively). The LS means of BHBA and Ac slightly increased over parities. These results suggest that proper maintenance of milk collection, herd management programs, and evaluation of ketone body levels in milk should be considered for the efficient management of resistance to ketosis.

Short communication: Relationship of activity and rumination to abundance of pest flies among organically certified cows fed 3 levels of concentrate.

The objectives of this study were to evaluate activity, rumination time, and their association with 3 kinds of pasture flies for organic dairy cows (n=57) fed 3 grain supplementation strategies during the grazing season from May to September 2013. Cows were assigned to 1 of 3 replicate supplementation groups: (1) no corn-grain supplementation (100% pasture, PAS, n=19); (2) low corn-grain (2.72kg/cow per day, LG, n=19); and (3) high corn-grain (5.44kg/cow per day, HG, n=19). Cows calved during 2 seasons (fall and spring) at the University of Minnesota West Central Research and Outreach Center, Morris, from October to December 2012 and March to May 2013. Supplement (corn-grain and minerals) was fed in a total mixed ration of corn silage and alfalfa silage, and at least 30% of diet dry matter intake for LG and HG cows consisted of pasture. Activity and rumination time (daily and 2-h blocks of time) were monitored electronically using HR-LD tags (SCR Engineers Ltd., Netanya, Israel) for 125d. Activity (cow body movement and head movement) was reported in activity units from SCR DataFlow II software, and rumination times were reported in minutes per day. PROC HPMIXED in SAS (SAS Institute Inc., Cary, NC) was used for statistical analysis, and independent variables were season of calving (fall or spring), month of grazing (June to September), supplementation group, and interactions of month of grazing and supplementation group. Replicate was a random effect with repeated measures. Daily activity was higher for PAS cows (1,138 activity units) than for HG cows (1,001 activity units), and LG cows (1,019 activity units). Daily activity was highest in July (1,258 activity units) and lowest in September (819 activity units). Rumination was not different for PAS (397min/d), LG (384min/d), or HG (370min/d) cows. Daily rumination was greater in September (402min/d) than in July (361min/d). Daily activity increased rapidly between 0600-0800h and 1600-1800h. From 1800 to 2000h, cows had a rapid decline in activity until 0600h the next day. All supplementation groups had the greatest rumination activity from 0200 to 0400h and the least between 1000 and 1200h. Greater activity of cows on a herd basis was moderately correlated with increased fly populations. Monthly activity patterns of grazing cows were associated with fly populations on cows.

Peripartal rumination dynamics and health status in cows calving in hot and cool seasons.

Our objective was to evaluate the effect of season of calving, associated with variable levels of heat stress, on the dynamics of rumination during the prepartum period and early lactation of cows that were healthy or affected by peripartal health disorders. Three weeks before the estimated due date, 210 multiparous Holstein cows at the University of Florida Dairy Unit were affixed with a neck collar containing rumination loggers, providing rumination time (RT) in 2-h periods. One blood sample was collected in a subpopulation of cows (n=76) at 12 to 48h postcalving to assess metabolic status by determining serum calcium, nonesterified fatty acid, and β-hydroxybutyrate concentrations. The occurrence of peripartal health disorders (dystocia, clinical ketosis, clinical hypocalcemia, metritis, and mastitis) was assessed by University of Florida veterinarians and trained farm personnel. We analyzed the dynamics of daily RT over ± 14d relative to parturition in cows that were healthy or affected by specific health disorders by season of calving [hot season, June to September (n=77); cool season, November to April (n=118)] using repeated measures analysis and comparison of least squares means at different time points relative to calving. Rumination was consistently reduced on the day of calving in both healthy and sick cows in both the hot and cool seasons. Only hot-season calvings had shorter average daily RT prepartum and postpartum in cows affected by severe negative energy balance and subclinical ketosis. Dystocia during the hot season was associated with shorter daily RT prepartum; for cool-season calvings, cows with dystocia had reduced RT postpartum. We also observed reduced RT in cows with ketosis prepartum and postpartum in both the hot and cool seasons. Daily RT was reduced postpartum in cows with hypocalcemia and mastitis that calved during the cool season, and it was shorter in cows with metritis in both the hot and cool seasons. Our results indicated that the effect of heat stress on changes in rumination patterns around calving for sick cows depends on the specific health disorder or metabolic condition.

Genetic evaluation of reproduction performance of Jersey × Red Sindhi crossbred cows

Aim:The present investigation was undertaken to study the reproduction performance and effect of non-genetic factors on reproduction performance of Jersey crossbred cows.Materials and Methods:Data on 355 Jersey crossbred cattle maintained at the Post-graduate Research Institute in Animal Sciences, Kattupakkam, Tamil Nadu, distributed over 30 years (1985 to 2014). The effect of various non-genetic factors including the period of birth, season of birth, period of calving, season of calving and parity were analyzed through least-squares analyses using univariate general linear model. The different (co)variance components for calculation of genetic parameters were estimated using restricted maximum likelihood method by fitting an animal model.Results:The overall least-squares means (±standard error) of age at first service, age at first calving, weight at first calving, service period, calving interval, dry period, and number of services per conception were 848.06±9.72 days, 1204±12.20 days, 289.81±1.71 kg, 210.01±6.41 days, 489.12±6.45 days, 137.96±5.58 days, 2.50±0.07, respectively. Period of calving had either significant (p<0.05) or highly significant (p<0.01) effect on all reproduction traits studied except service period, calving interval, and dry period. Number of services per conception was affected by season of calving. Parity had significant influence (p<0.05) or highly significant (p<0.01) influence on all the traits studied except service period and dry period. Heritability estimates of age at first service, age at first calving, weight at first calving, service period, calving interval, dry period, and number of services per conception were 0.299, 0.220, 0.017, 0.142, 0.222, 0.177, and 0.042, respectively. The estimates of repeatability for service period, calving interval, dry period, and number of services per conception were 0.219, 0.234, 0.420, and 0.001, respectively.Conclusions:The reproduction performances of Jersey × Red Sindhi crossbreds were lower when compared to the earlier reports on Jersey crossbreds. Heritability and repeatability values were also low to moderate, indicating limited scope for improvement through selection.

Factors affecting timing and intensity of calving season of beef cow-calf producers in the Midwest

Despite demonstrated market incentives to adopt controlled calving seasons, many producers still have herds that calve somewhat broadly throughout the year. We postulate this observed management behavior is related to a variety of factors. Primary data, collected through a coordinated survey effort with the USDA National Agricultural Statistics Service, were used to quantify factors that affect producers’ decisions regarding timing and intensity of calving season. Of the survey respondents, 88% were commercial producers and 12% were seedstock producers or operated a combination seedstock–commercial operation with an overall average of 63 beef cows. Ninety-seven, 50, 33, and 26% of farms calve in the spring (March, April, May), summer (June, July, August), fall (September, October, November), and winter (December, January, February), respectively. Twenty-two percent observed a calving season exclusively in the spring. Sixty-six percent of respondents indicated calving season was dictated by weather, 34% because of labor availability, and 31% because of tradition. Least often reasons for calving season were market timing (16%), feed availability (8%), and other (4%). Producer-stated reasons for calving season explained 62% of the variation in timing and intensity of calving on an operation, whereas a model of producer demographic and operation characteristics explained 83% of the variation. These results highlight the importance of evaluating producer and operation characteristics in addition to producer input when making recommendations to enhance production efficiency and profitability. Furthermore, understanding the factors that affect calving season provides opportunities for improved extension and research programming.

بررسی عوامل موثر بر نسبت جنسی ثانویه گاوهای شیری هلشتاین

نسبت ثانویه جنسی، نسبت گوساله های نر به ماده زنده متولد شده است. مطالعات انجام شده در گونه های مختلف پستانداران نشان می دهد که فاکتورهای متعددی بر نسبت جنسی ثانویه تاثیر دارند. تغییر در نسبت جنسی ثانویه در گاوهای شیری به لحاظ اقتصادی اهمیت داشته و مورد توجه قرار گرفته است و توانایی تغییر آن می تواند درآمد و سوددهی یک گاوداری را تحت تاثیر قرار دهد. هدف از این آزمایش بررسی تاثیر پاره ای از عوامل موثر بر نسبت جنسی در گاوهای هلشتاین ایران بود. در مطالعه حاضر از داده‌های شش گله بزرگ گاو شیری در خلال سال‌های 1375 تا 1389 استفاده شد. میانگین تولید استاندارد شده 305 روز گله‌ها 8145 کیلوگرم (با دامنه 7578 تا 8670 کیلوگرم) بود. گله های مزبور تحت پوشش مرکز اصلاح نژاد ایران بوده و ثبت مشخصات و رکوردگیری آن‌ها به صورت منظم توسط کارشناسان شرکت‌های تعاونی گاوداران انجام می‌شد. این گله‌ها در ناحیه شمال شرقی کشور قرار داشتند. داده های تولیدی (روز تولید و تولید تجمیعی ظیر شیر تصحیح شده بر اساس 60 و 305 روز شیردهی)، داده‌های تولید مثلی (نظیر سال زایش، فصل زایش، نوع زایش، جنس گوساله متولد شده، آخرین اطلاعات مربوط به تلقیح، روزهای باز)، و جزئیات حذف احتمالی از گله و یا مرگ ثبت می‌شد. داده‌های جمع‌آوری شده از گله‌ها پیش از تجزیه و تحلیل مجددا راستی آزمایی شد. بر اساس اسپرم استفاده شده، اسپرم‌ها به چهار گروه ایرانی، کانادایی، آمریکایی و سایر کشورها (شامل اسپرم‌های تهیه شده از کشورهای اروپایی) تقسیم بندی شدند. برای آنالیز آماری داده ها از مدل رگرسیون لجستیک استفاده شد. نتایج نشان داد که درصد گوساله های نر به گوساله های ماده 53 به 47 بود. در مطالعه حاضر نوع اسپرم مورد استفاده در تلقیح مصنوعی (شامل: ایرانی، آمریکایی و کانادایی) تاثیر معنی داری بر نسبت ثانویه جنسی نداشت. سال زایش نیز تاثیری بر نسبت جنسی نداشت. نتایج مطالعه حاضر نشان داد که نوع زایمان (طبیعی و یا غیرطبیعی) تاثیر معنی داری بر نسبت ثانویه جنسی داشت (0.001P

Optimization of dry period in Karan Fries cow.

Aim:The objective of this study was to optimize dry period (DP) length that can maximize the production across adjacent lactations and overall lifetime yield.Materials and Methods:Performance records with respect to DP spread over a period of 15-year in Karan Fries (KF) cattle maintained at Livestock Research Centre (National Dairy Research Institute), were collected for the study. Data of 681 KF cows were analyzed by least square technique to examine the effect of non-genetic factors on DP. Season of calving was classified into four seasons: Winter season (December-March), summer season (April-June), rainy season (July-September), and autumn season (October-November); period of calving into five periods: 1998-2000 (1-period), 2001-2003 (II-period), 2004-2006 (III-period), 2007-2009 (IV-period), and 2010-2012 (V-period), and parity into six parities, i.e., 1st, 2nd, 3rd, 4th, 5th, and >6th parities to see the effect of non-genetic factors on DP.Results:Period of calving, season of calving, and parity did not affect the DP significantly (p<0.05). The overall least square mean of DP was 67.93±2.12 days. For the optimization of DP with regard to milk productivity, analysis was carried out by class interval method. DP was classified into eight classes (<22, 23-45, 46-67, 68-89, 90-111, 112-133, 134-155, and >156 days), and optimum level was obtained at 46-67 days (3rd class) with the following respective milk yield (MY) of 305 daily MY (4016.44±43.68 kg), total MY (4704.21±61.51 kg), MY per day of lactation length (13.03±0.13 kg), and MY per day of calving interval (11.68±0.41 kg).Conclusion:From the study, it was concluded that this optimal DP length (46-67 days) is suitable for maximizing the production. Hence, one should aim to dry off pregnant cows to achieve a DP of appropriate length to enhance productivity in the next lactation, as very short and very long DP reduces the economic profitability in dairy animals.

Risk factors associated with abnormal parturition and their effects on production and reproductive performance in Frieswal cattle of India

Records of 1024 Frieswal cows maintained at the Military Farm, Meerut, India over a period of 20 years from 1989 to 2008, sired by 91 bulls were included in the present study to assess the incidence and risk factors associated with abnormal parturition like dystocia, stillbirth, premature birth and abortion. The overall incidence of abnormal parturition in this herd of Frieswal was 14.01%, out of which 7.91, 3.99, 1.12 and 0.99% correspond to stillbirth, abortion, dystocia and premature birth. Wald Chi square analysis revealed season of calving (p&lt;0.04), period of calving (p&lt;0.0001) and parity (p&lt;0.0008) influenced normal calving. The effect of abnormal parturition on the total milk yield, lactation length, calving interval and dry period was also assessed along with other non-genetic factors viz., season, period of calving and parity. A reduction in milk yield was observed (p&lt;0.01) in animals which had undergone abnormal parturition (2723.75± 67.88 kg) in comparison to normally calved animals (3310.08± 35.36 kg). The dry period was also found to be longer in abnormally calved animals (127.18±4.63 days) than normal ones (117.75±2.39 days). Regular monitoring and better reproductive management will surely reduce the incidence of abnormal parturition, and thereby increase the production and reproductive performance of the animals.