The growth curve parameters as derived from 6 different models using 493 weight records for ABC are presented in Table 3. In the study, R2 (coefficient of determination) and RSD (Residual Standart Deviation) and corel (correlation) between the observed and estimated growth curves were used to compare the models. The 3rd degree polynomial model showed the highest R2 and corel and lowest RSD indicating the best goodness of fit. On the other hand, the Gompertz model was the least fitted to estimate the ABC weight based on its lowest value of R2. That is, the 3rd degree polynomial model with four parameters (β0, β1, β2, β3), which has the highest R2 and smallest RSD value, best explains the change in live weight according to age in ABC. In Fig. 1, the growth curve of the observed weights by gender and estimated according to the models is presented. As can be seen in Fig. 1, the model most compatible with the values observed in ABC from birth to 24 months is the 3rd degree polynomial model.
Table 3
Model comparison for growth of Anatolian Black Cattle
Model | β0 | β1 | β2 | β3 | R2 | RSD | corel |
2nd degree polynomial | 21.80 ± 0.619 | 0.44 ± 0.0132 | 0.01 ± 0.001 | - | 0.997 | 3.216 | 0.994 |
3rd degree polynomial | 18.72 ± 0.361 | 0.33 ± 0.099 | 0.01 ± 0.002 | 0.01 ± 0.001 | 0.999 | 1.388 | 0.998 |
| Wa | B | K | ti | | | |
Logistic | 206.09 ± 8.417 | - | -1.79 ± 1.788 | 8.84 ± 8.839 | 0.953 | 11.533 | 0.989 |
Brody | 225.56 ± 15.625 | 0.83 ± 0.027 | 0.01 ± 0.001 | - | 0.979 | 3.561 | 0.993 |
Von Bertalanffy | 169.96 ± 15.650 | -0.19 ± 0.124 | 0.01 ± 0.005 | - | 0.924 | 14.736 | 0.961 |
Gompertz | 129.05 ± 4.530 | 2.751 ± 0.079 | 0.40 ± 0.000 | - | 0.862 | 27.141 | 0.703 |
In similar studies, the 3rd degree polynomial model was determined as the most suitable model in Holstein breed by Heinrichs and Hargrove (1987); Ayrshire, Brown Swiss and Shorthorn breeds by Heinrichs and Hargrove (1994); Holstein and Brown Swiss breeds by Akbulut (1999). On the other hand, the most suitable models were Gompertz and Von Bertalanffy model (R2 = 0.70) in Madura breed by Hartati and Putra (2021); Richards model (R2 = 0.999) in Holstein by Tutkun (2019); Logistic model in pre-weaning period; Gompertz and Richards models in post-weaning period in the Holstein breed by Koşkan and Özkaya (2014); Richards model (R2 = 0.968, 0.960) in Brown-Swiss and Holsteins by Bayram and Akbulut (2009); the Richards model (R2 = 0.976) in Anatolian Buffaloes by Şahin et al. (2014). The most suitable models differ in studies conducted with different breeds and environmental conditions. In practice, determining the weight-age relationship of cattle requires a lot of expense and time (Bayram and Akbulut, 2009). In order to make reliable estimations in different regions and different breeds and to use the obtained parameters for selection purposes, first of all, the selection of the appropriate model is necessary.
In the rest of this paper, the results of the 3rd degree polynomial model were presented due to reason that it was determined as the best model for the evaluation of the environmental effects on the data obtained from animals. Table 4 reflects the least square means and their corresponding standard errors of β0, β1, β2, β3 parameters by environmental factors. As a result of the analysis, R2 values were found between 0.999-1.0 in all environmental factors, while corel values ranged between 0.997-1.0.
Table 4
Least square means and standard errors of the 3rd degree polynomial model parameters in ABC by different environmental factors
Factor | Group | n | β0 ± SE | β1 ± SE | β2 ± SE | β3 ± SE |
Sex | Female | 48 | 17.61 ± 0.608 | 0.01 ± 0.182 | 0.011 ± 0.0028 | 0.0009 ± 0.0004 |
Male | 65 | 20.25 ± 0.573 | 0.35 ± 0.171 | 0.005 ± 0.0027 | 0.0005 ± 0.0003 |
Dam Age | 2–3 | 31 | 21.18 ± 1.773 | -0.52 ± 0.530 | 0.006 ± 0.0083 | -0.0006 ± 0.0011 |
4–7 | 46 | 17.45 ± 0.797 | 0.80 ± 0.238 | 0.002 ± 0.0037 | 0.0006 ± 0.0005 |
8–10 | 17 | 18.12 ± 1.037 | 0.17 ± 0.310 | 0.006 ± 0.0048 | 0.0007 ± 0.0006 |
11+ | 19 | 18.99 ± 0.979 | 0.26 ± 0.293 | 0.019 ± 0.0046 | 0.0020 ± 0.0006 |
Parity | 1 | 29 | 14.40 ± 1.704 | 0.92 ± 0.510 | 0.010 ± 0.0080 | 0.0023 ± 0.0010 |
2 | 24 | 18.00 ± 0.985 | -0.45 ± 0.295 | 0.016 ± 0.0046 | 0.0012 ± 0.0006 |
3 | 19 | 19.95 ± 0.995 | -0.34 ± 0.297 | 0.018 ± 0.0046 | 0.0008 ± 0.0006 |
4 | 15 | 19.48 ± 1.084 | -0.39 ± 0.324 | 0.012 ± 0.0050 | -0.0001 ± 0.0007 |
5 | 12 | 20.90 ± 1.189 | 0.13 ± 0.355 | 0.003 ± 0.0055 | -0.0002 ± 0.0007 |
6 | 8 | 20.33 ± 1.511 | 0.63 ± 0.452 | -0.002 ± 0.0071 | 0.0001 ± 0.0009 |
7 | 6 | 19.47 ± 1.683 | 0.73 ± 0.503 | -0.002 ± 0.0079 | 0.0005 ± 0.0010 |
Year | 2015 | 18 | 17.81 ± 1.026 | 0.49 ± 0.307 | 0.003 ± 0.0047 | 0.0005 ± 0.0006 |
2016 | 23 | 19.03 ± 0.876 | 0.15 ± 0.262 | 0.007 ± 0.0041 | 0.0001 ± 0.0005 |
2017 | 17 | 18.39 ± 0.967 | 0.17 ± 0.289 | 0.003 ± 0.0045 | -0.0001 ± 0.0006 |
2018 | 24 | 19.70 ± 0.784 | 0.21 ± 0.234 | 0.008 ± 0.0036 | 0.0011 ± 0.0005 |
2019 | 10 | 19.27 ± 1.147 | -0.10 ± 0.343 | 0.012 ± 0.0054 | 0.0016 ± 0.0007 |
2020 | 21 | 19.39 ± 1.041 | 0.14 ± 0.311 | 0.013 ± 0.0047 | 0.0009 ± 0.0006 |
Season | Winter | 17 | 17.49 ± 0.960a | -0.15 ± 0.287 | 0.179 ± 0.0044a | 0.0019 ± 0.001 |
Spring | 55 | 19.78 ± 0.696ab | 0.37 ± 0.208 | 0.002 ± 0.0032b | 0.0002 ± 0.000 |
Summer | 26 | 20.58 ± 0.777b | 0.41 ± 0.232 | 0.004 ± 0.0036b | 0.0001 ± 0.000 |
Autumn | 15 | 17.88 ± 1.038ab | 0.08 ± 0.310 | 0.008 ± 0.0048ab | 0.0006 ± 0.001 |
a,b,c The means with the different superscripts within the factor in the same column are different (P < 0.05).
In Figs. 2, 3, 4, 5 and 6 the growth curves of animals according to sex, dam age, parity, birth year and birth season are presented by using the 3rd degree polynomial model. As Fig. 2 is examined, it has been determined that males have a higher weight than females in both observed and predicted values in all periods. Sahin et al. (2014) found that adult live weight was higher in males in all models (Lojistik, Gompertz, Richards, Brody) examined in Anatolian buffaloes. Hartati and Putra (2021) reported that the animals had similar growth characteristics in all models (Logistik, Gompertz, Von Bertalanffy) they examined in both sexes in Madura cattle. Growth in both males and females in the study continued until the age of 24 months, which can be clearly as seen in the linearly plotted growth curve in Fig. 2. Akbulut (1999), using the 3rd degree polynomial model, determined that the growth in Holstein and Brown Swiss breeds continued linearly up to 18 months.
As Figs. 3 and 4 are examined, the differences according to dam age and parity became more pronounced after 18 months of age. According to the chosen model, it was estimated at higher live weight calves born from 11 + age group in periods BW, 3M and 24M; 8–10 age group in periods 6M and 12M; 2–3 age group in 18M. When the graph of differences according to the parity is examined, it was determined to have higher weights animals born from cows 5th lactation in period BW; 7th lactation in periods 3M, 6M and 12M; 2nd lactation in periods 18M and 24M.
When Figs. 5 and 6 are examined, the differences according to the year of birth and season of birth began to appear mostly from 6M. Differences between years were found to have higher weights calves born in 2020 in periods birth, 6M and 12M; 2018 in periods 3M; 2019 in periods 18M and 24M. Differences between seasons were estimated to be heavier calves born in summer in periods birth and 6M; spring in periods 6M and 12M; autumn in periods 18M and 24M.
According to this model, the estimated values showed a deviation of around 1–2 kg in female and male animals at all periods compared to the observed values, while in males they showed a deviation of 3–5 kg only in the 12M and 18M periods. In other graphs, the differences between the generally estimated values and the observed values are between 1–3 kg, and the differences were found to be around 4–5 kg only in 18M periods. This indicates that the 3rd degree polynomial model is the most appropriate model for the growth values of ABC.
Monitoring the growth and development of animals during some periods in the growth process will be of great benefit to the farms in terms of herd management, care and feeding regulation (Şahin et al., 2014). In order to obtain reliable estimates of the growth curve parameters, it may be necessary to collect growth data until the point when the growth curve starts to flatten or the growth rate slows down (Koncagül and Çadırcı, 2009). Changes in body weight in animals reflect the influence of environmental factors and management systems, particularly nutrition (Entwistle et al., 2012). The fact that there is a difference in live weights according to the environmental conditions generally examined during the weighing periods in the ABC shows that the animals can change in the desired direction by selection. In addition, by monitoring the growth of the animals, early intervention can be made for animal that has a problem in their development.