Evaluation of Black Pied first-calf heifers` lactation of various genotypes

Purpose: Comparative assessment of the fullness of lactation of primarmels of different genotypes.Materials and methods. The article presents the results of the assessment of the lactation activities, which was carried out in the SEC "Kazminsky" Kochubeevsky district of the Stavropol region on the livestock of the black and motley breed of local and brown populations from the Vologda region from LLC "Zaozerier" (farm №. 1) and SHPK "Proseukhon" (farm №2). Three experienced animals groups of 30 goals were formed in each, studies were carried out according to generally accepted methods.Results. The greatest amount of milk for 305 days I lactation was obtained from the first elevations brought from LLC "Zaozerier" - 7368 kg, which is 3.64% more than from the cows of their own reproduction and 8.85% more than from animals grown in SEC "Proseukhonskoye". The lactation stability ratio was calculated in two ways, and in both cases there was more than 100, the factor of the fullness of lactation in the cows of the studied genotypes this indicator was also very high and amounted to 87.7-91.6, which indicates a high level of breeding and tribal work, and On the significant influence of genetic factors on the lactation activity of the studied animals. According to the nature of the lactation curve, the pilot of all three genotypes can be attributed to the I type - high stable lactation. However, the greatest amount of milk from cows was obtained in the third phase of lactation.Conclusion. Thus, it can be concluded that the period of adaptation did not have a significant impact on the lactation activity of the delivered first elements. The animals studied were characterized by high productivity and sustainable lactation.It is desirable when evaluating the cows, along with productivity for 305 days of lactation, consider individual qualities and the ability to hold high productivity to a large part of the lactation period. For more differentiated selection of cows in the breeding group, we recommend using the stability coefficients and the usefulness of lactation.

Feed behavior and milk productivity in cows of different fattening

The results of feed behavior and milk productivity in the cows of Ukrainian black-speckled dairy breed of different fattening of the first and second lactations from the first month to the end of lactation are given. The analysis of the herd showed that the highest milk productivity in cows of the first lactation was found in the group of fattening from 3 to 4 points, which was by 9.2 % (P ≥ 0.99) higher, compared to the group of cows with fattening 4 points and more. The milk yield in cows of the second lactation with fattening from 3 to 4 points exceeded the milk yield of cows with fattening 4 points and more by 12.9 % (P ≥ 0.95). The content of fat and protein in milk was higher in the cows with higher fattening, compared to the cows with lower fattening. The highest average daily milk yield was found in cows of the first lactation with fattening from 3 to 4 points. Depending on the month, it was by 5.5–11.7 % (P ≥ 0.95 – P ≥ 0.999) higher, compared to the cows with fattening 4 points and more, while it was by 6.9–10.0 % (P ≥ 0.95 – P ≥ 0.999) higher in cows of the second lactation. The gestation period of cows has a significant effect on the reduction of milk yield. The milk yield of cows in connection with the term of their gestation are reduced by 0.1 kg per day during the second month after insemination, by 0.2 kg per day during the third month, by 0.3 kg per day during the fourth month, by 0.6 kg per day during the fifth month, by 1.0 kg per day during the sixth month, by 1.7 kg per day during the seventh month and by 2.8 kg per day during the eighth month. The analysis of the dynamics of monthly milk yield shows that lactation curves of cows increase from the first day of lactation to its peak, which occurs in the 2nd – 4th month after calving. The lactation curve in the cows with fattening from 3 to 4 points has a higher peak in the 2nd –3d month of lactation, compared to the cows with higher (more than 4 points) fattening. The animals of all groups, except for cows of the second lactation (with fattening 4 and more points) showed the maximum productivity in the 2nd –3d month of lactation; then the lactation curve decreased with different intensity. The index of constancy of lactation and the index of falling milk yield are the important indicators that characterize the stability of lactation curves. The constancy of lactation curves having been determined by I. Johansson-Hansson index was higher in the cows with fattening 4 and more points, compared to the indicator of the cows with fattening from 3 to 4 points. The studies of behavioral reactions have shown that the animals of the first lactation with an average (from 3 to 4 points) fattening consume feed during 208.5 minutes, which is by 17 minutes (P ≥ 0.999) longer than the animals with higher average fattening, and by 14.5 minutes (P ≥ 0.99) longer than the animals of the second lactation.

Evaluation of Non-linear Models to Predict Potential Milk Yield of Beef Cows According to Parity Order Under Grazing

This study aimed to evaluate the effect of parity order on milk yield (MY) and composition over time of grazing beef cows and to evaluate non-linear models to describe the lactation curve. Thirty-six pregnant Nellore cows (12 nulliparous, 2 years; 12 primiparous, 3 years; and 12 multiparous, 4–6 years) were included in the study. With calving day assigned as day 0, milking was performed using a milking machine to estimate MY on days 7, 14, 21, 42, 63, 91, 119, 154, and 203. Dummy variable analyses were applied to estimate its effects on MY, composition (kg and percentage), afternoon/morning, and afternoon/total proportions. Since multiparous cows had higher MY than nulliparous and primiparous cows, two different groups were used for lactation curve analysis: Mult (multiparous) and Null/Prim (nulliparous and primiparous). The MY estimated by the last edition of BR-Corte (Nutrient Requirements of Zebu and Crossbred Cattle) equation was compared with the observed values from this study. Five nonlinear models proposed by Wood (WD), Jenkins & Ferrell (JF), Wilmink (WK), Henriques (HR) and Cobby & Le Du (CL) were evaluated. Models were validated using an independent dataset of multiparous and primiparous cows. The estimates for parameters a, b, and c of the CL equation were compared between groups, and the BR-Corte equation used the model identity methodology. Nulliparous and primiparous cows displayed similar MY (P > 0.05); however, multiparous cows had an average MY that is 0.70 kg/day greater than that of nulliparous and primiparous cows (P < 0.05). Milk protein and total solids were higher for multiparous cows (P < 0.05). Effect of days in milking was found for milk fat, protein, and total solids (P < 0.05). The yield of all milk components was higher for multiparous cows than for nulliparous and primiparous cows. The afternoon/morning and afternoon/total proportions of milk production were not affected by parities and days in milking (P > 0.05), with an average of 0.76 and 0.42, respectively. The BR-Corte equation did not correctly estimate the MY (P < 0.05). The equations of WD, WK, and CL had the best estimate of MY for both Mult and Null/Prim datasets. The equations had a very similar Akaike's information criterion with correction and mean square error of prediction.

Physiology of milk production and modelling of the lactation curve.

Lactation is defined as the combined processes of synthesis, secretion, and excretion of milk, starting at calving and continuing until natural or induced drying off in the lactating female. Milk production follows a common pattern in several mammalian species known as a lactation curve. A typical lactation curve starts at day four after calving, reaching peak yield in early lactation, followed by a daily decrease in milk yield (persistency) until the lactating female is artificially dried off, or the lactation comes to a natural end. Mathematical models have been applied to lactation curves to provide information in relation to lactation curve parameters, providing valuable information for herd management and breeding decisions. Therefore, the aim of this study was to review the most used mathematical models for the prediction of dairy production curves. The importance of modelling lactation curves is to predict the yield for each day with the minimum possible error, to be able to elucidate the underlying pattern of milk production in the presence of local variation associated with the effect of the environment. The usefulness of any model of adjustment to the lactation curve depends on its capacity to mimic the biological process of developing milk production and to adjust the factors that affect it. Furthermore, these models can only be used to adjust productive records adequately, or to provide a biological understanding of the lactation process.

Comparison and estimation of different linear and nonlinear lactation curve submodels in random regression analyses on dairy cattle

In the random regression model (RRM) for milk yield, by replacing empirical lactation curves with the five-order Legendre polynomial to fit fixed groups, the RRM can be transformed to a hierarchical model that consisted of a RRM in the first hierarchy with Legendre polynomials as individuals’ lactation curves resolved by restricted maximum likelihood (REML) software, and a multivariate animal model for phenotypic regression coefficients in the second hierarchy resolved by DMU software. Some empirical lactation functions can be embedded into the RRM at the first hierarchy to well fit phenotypic lactation curve of the average observations across all animals. The functional relationship between each parameter and time can be described by a Legendre polynomial or an empirical curve usually called submodel, and according to three commonly used criteria, the optimal submodels were picked from linear and nonlinear submodels except for polynomials. The so-called hierarchical estimation for the RRMs in dairy cattle indicated that more biologically meaningful models were available to fit the lactation curves; moreover, with the same number of parameters, the empirical lactation curves (MIL1, MIL5, and MK1 for 3, 4, and 5 parameters, respectively) performed higher goodness of fit than Legendre polynomial when modelling individuals’ phenotypic lactation curves.

Lactation curve, milk production of Pelibuey ewes and preweaning growth rate of the lambs

Objective: To estimate the lactation curve and milk production of Pelibuey ewes andthe relationship with preweaning growth rate of the lambs.Design/methodology/approach: Forty five Pelibuey ewes were milked during 70days in Montecillo, México, in 2018, to estimate daily and total milk production. Thelactation curve was fitted with the incomplete gamma function. In addition, the effectsof type of birth and ewe weight at milking on milk production were analyzed, andcorrelations were calculated between ewe milk production and growth rate of thelambs, per week and for the entire lactation Results: A “typical” lactation curve was found, average ewe milk production for theentire lactation, weighted for the number of lambs suckling, was 131±8 L, with444±24 g d -1 . Ewe weight at milking had an effect (p<0.01) on milk production.Positive correlations were found (p<0.05) between ewe milk production andpreweaning growth rate of the lambs.Limitations on study/implications: There is a strong dependency of the lambs forthe milk production of the Pelibuey ewe, a factor of great relevance so that lambs cangain body weight and survive during lactation.Findings/conclusions: Pelibuey ewes produce less milk than dairy ewes. Therefore,lambs should be weaned at a maximum of 10 weeks of lactation.

Influence of caprine arthritis encephalitis on milk production and quality along the lactation curve in primiparous dairy goats

The aim of this study was to examine the influence of caprine arthritis encephalitis (CAE) on the production of milk and its components (protein, fat and total solids) along the lactation curve of primiparous goats. The study was developed using a database from the years 2014 to 2018. Sixty-one animals were subjected to the serological test for CAE, whose result indicated that 42 were seropositive and 19 seronegative, and milk production and quality data were compiled. To adjust the curve for production of milk, fat, protein and total solids during lactation, the following nonlinear model developed by Wood (1967) was used: Y = atb e-ct, where Y represents the observations of milk, fat, protein or total solid production at time t; a is the parameter associated with the initial production; b is the parameter associated with the rate of rise in production until the peak; c is the parameter associated with the rate of decline of the lactation curve; and is the representative time of the day in milk. The parameters were compared by the confidence interval considering 95% probability. Peak production was calculated using the following formula: a(b/c)b e-b. There was no statistical difference (p > 0.05) between seropositive and seronegative primiparous goats for initial production and the rates of rise and decline of the parameters of milk, fat, protein and total solid production. However, at their peak, these variables were 26, 27, 23 and 23% higher, respectively, in the seronegative goats than in their seropositive counterparts. In conclusion, CAE does not affect milk production or the production of fat, protein and total solids along the lactation curve, but seropositive goats produce less milk and respective components at the peak of the lactation curve than seronegative goats.

COMPARATIVE FEATURES OF DAIRY EFFICIENCY OF COWS OF THE GOLSHTEIN AND HOLSHTINIZED BLACK AND WHITE BREEDS OF THE REPUBLIC OF KAZAKHSTAN

В последние 20—25 лет на маточном поголовье черно-пестрого скота активно использовалось семя быков-производителей голштинской породы, завезенных по импорту из США и Канады. Это привело к тому, что в республике сформировался массив черно-пестрого скота с высокой долей кровности по улучшающей голштинской породе. Параллельно по импорту завозились и животные голштинской породы, в основном телки случного возраста и нетели. В конечном итоге в Казахстане образовались генотипы, схожие по внешним признакам, но отличающиеся по продуктивности. В статье отражены результаты научных исследований по сравнительному изучению молочной продуктивности коров двух родственных пород черно-пестрой масти. Показано, что высококровные (более 87,5 % по улучшающей породе) животные по удою на 30—43% уступали чистопородному голштинскому скоту, однако помеси на 2—4% превосходили голштинов по содержанию жира и белка в молоке. Отмечены идентичные биологические свойства обеих пород, связанные с лактационной кривой, как за полную лактацию, так и по суточным надоям. Полученные результаты обосновывают целесообразность полного поглощения значительной части казахстанской популяции черно-пестрого скота голштинской породой. Однако необходимо определенную часть животных сохранить в чистоте и на этой основе создать генофондные стада. In the last 20—25 years, the seed of bulls-producers of the Holstein breed, imported from the USA and Canada, has been actively used on the broodstock of black-and-white cattle. This led to the formation in the republic of an array of black-and-white cattle with a high proportion of blood in the improving Holstein breed. At the same time, animals of the Holstein breed were also imported, mainly heifers of breeding age and heifers. Ultimately, genotypes were formed in Kazakhstan, similar in appearance, but differing in productivity. The article reflects the results of scientific research on a comparative study of the milk productivity of cows of two related breeds of black and white color. It has been shown that high-blooded (more than 87.5% in the improving breed) animals in milk yield were 30—43% inferior to pure-bred Holstein cattle, but hybrids exceeded Holsteins by 2—4% in fat and protein content in milk. The identical biological properties of both breeds, associated with the lactation curve, both for full lactation and for daily milk yield, were noted. The obtained results justify the feasibility of fully absorbing a significant part of the Kazakh population of black and white cattle by the Holstein breed. However, it is necessary to keep a certain part of the animals clean and on this basis create gene-pool herds.

The effect of age at first calving on the milking performance of primiparous Jersey cows

<b>The aim of this study was to determine the effect of age at first calving on the milking performance of primiparous Jersey cows (261 cows). Analyses were conducted on 2461 test day milking samples from 17.09.2007 to 26.07.2016. The primiparous cows were divided into four groups according to their age at first calving (≤ 24, > 24–26, > 26–28, > 28 months), and their daily milk yields were compared. Fourfold contingency tables were prepared to investigate the distribution of the population of cows calving at different ages and the peak daily milk yield. The significance of the association between factors was estimated using Fisher's exact test. To illustrate the course of 305-day lactation in primiparous cows varying in age at first calving, linear graphs were plotted with linear trends for daily milk yields. Primiparous Jersey cows calving at the age of > 26–28 months of life had the highest daily milk yield. In terms of the contents of basic milk constituents in the first lactation, the most advantageous age at first calving was > 24–26 months of life. However, a younger age at first calving (≤ 24 months) was associated with a lower somatic cell count in milk as well as a more favourable lactation curve for daily milk yield. The results of the study may suggest that Jersey cows calving at an earlier age (up to 24 months) may have a longer productive life and thus better performance parameters.

Characterization of Lactation Curve Patterns using Non-linear Models in Crossbred Dairy Cattle

Background: Lactation curve patterns are currently integrated in dairy cow’s management software. Lactation curve modeling is useful for monitoring individual yields for diet planning, determining optimum strategies for insemination and genetic evaluation. It also helps for predicting expected missing values on field records and gives concise summary of biological efficiency and persistency of dairy cows.Methods: The study was aimed to characterize the lactation curve pattern for crossbred dairy cattle using different non-linear models. During the period 1991 to 2018, daily milk yield (DMY) consisted of 281698 records of 750 crossbred dairy cows maintained at Livestock Farms. GADVASU, Ludhiana, were collected for the study. Different non-linear models viz. exponential decline function (EDF), parabolic exponential model (PEM), inverse polynomial model (IPM), gamma-type function (GTF), mixed log function (MLF) and Ali and Schaeffer model (ASF) were used for the analysis. The model(s) that best fit and describe the curve characteristics was selected on the basis of coefficient of determination (R2), coefficient of variation (CV), Akaike information criterion (AIC) and mean square error (MSE).Result: The study clearly revealed that the PRM gave highest fit to DMY data with R2, MSE, AIC and CV values of 98.10%, 0.087, -743.31 and 2.37%, respectively. The IPM had also best fitted the observed DMY data with highest R2 (98.05%), lower MSE (0.089), low AIC (-735.8972) and lower CV (2.40%) values. The fitting of observed DMY data with predicted DMY were also found to be higher in the MLF (R2= 96.46%, MSE= 0.159, AIC= -558.16 and CV= 3.21%) and GTF (R2= 95.85%, MSE= 0.190, AIC= -505.24 and CV= 3.50%), whilst the EDF and PEM Models depicted relatively low fit to the DMY data when compared with the other non-linear models. However, IPM and GTF models can be used for accurate prediction of daily milk yield in the crossbred cattle population because they were typical standard lactation curves.