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Simple Summary: Growth traits are important parameters in husbandry. Especially for meat-type animals, understanding the genetic background and identifying naturally occurring polymorphisms can enhance production. Also, meat quality is a very important factor for food processing and consumers. In this study, we analyse IGFBP genes for possible polymorphisms that may influence growth traits and/or meat quality traits in rabbits. We found one polymorphism that influences the pH value, one of the most important indicators of meat quality, and therefore, this polymorphism may be used in the selection process. Rabbits are important livestock animals, popular for their nutritional value. Nowadays, the molecular background of traits influencing the quality of meat and meat products is in high demand. Therefore, in the current study, we analyse the sequences of IGFBP1, IGFBP2, IGFBP4, IGFBP5, and IGFBP6 for possible polymorphisms. Based on a bioinformatics analysis in an association study on 466 animals of different breeds (New Zealand White × Flemish Giant crossbreed (9NZWxFG), Termond White (TW), Popielno White (PW), and Flemish Giant (FG)), we analyse the influence of five polymorphisms within the IGFBP genes. Statistically significant differences were found among the carcass and meat quality traits but not for all of the analysed rabbit breeds. The most promising polymorphism was g.158093018A>T within the IGFBP5 gene. The values of pH24 of m.longissimus lumborum (m.l.l.) and biceps femoris muscles (m.b.f.) were higher for the AT genotypes compared to the AA genotypes for the TW and NZWxFG crossbreeds. Also, for pH24, we found differences in ing.41594308T>C for NZWxFG, where the TT genotype values were higher than the TC values. We found differences in L*24 on m.l.l. for g.41592248A>C for NZWxFG. For m.b.f., significant differences were found in b*45 for g.3431insAC in the FG population and a*45 for g.41592248A>C and g.158093018A>T in the TW population. The shear force statistically differed for g.158093018A>T in TW rabbits and g.41592248A>C for NZWxFG. We conclude that this polymorphism may be promising for better quality rabbit meat and may be implemented in selection processes. [ABSTRACT FROM AUTHOR]

Simple Summary: Culturing of muscle precursor cells—satellite cells—is the basis for research on obtaining meat using in vitro techniques, which can become an alternative to traditional meat production. The available literature data do not give a clear answer as to the medium used at the proliferation stage of bovine satellite cells; therefore, there is a need to select the level of components of the growth medium. In our research, based on the fluorometric measurement of proliferating cell growth and qPCR analysis, we examined the effect of the three most common components: glucose, serum (bovine or horse), and bFGF—a mitogenic factor. The results show that the most critical component affecting the proliferation rate is the serum—the addition of bovine serum, followed by the addition of bFGF—at 10 ng/mL. In turn, the lower glucose content ensures the maintenance of cells at the early stage of myogenesis and, thus, the self-renewal of their population. In conclusion, a higher proliferation rate of bovine satellite cells is ensured under the conditions of bovine serum and a mitogenic factor at 10 ng/mL. It is predicted that already in 2040, 35% of requirements for meat will be provided by in vitro production. Recreating the course of myogenesis in vitro, and thus resembling a structure of muscle tissue, is the basis for research focusing on obtaining cultured meat and requires providing relevant factors supporting the proliferation of satellite cells—being precursors of skeletal muscles. The present work aimed to develop the composition of the medium that would most effectively stimulate the proliferation of bovine satellite cells (BSCs). The modeling and optimization methods included the measurements of the synergistic, co-stimulatory effect of three medium components: the amount of glucose, the type of serum (bovine or horse), and the amount of mitogenic factor—bFGF. Additionally, the qPCR analyses determined the expression of genes involved in myogenesis, such as Pax7 and Myogenic Regulatory Factors, depending on the level of the tested factor. The results showed significant positive effects of serum type (bovine serum) and mitogenic factor (addition of 10 ng/mL bFGF) on the proliferation rate. In turn, qPCR analysis displayed no significant differences in the relative expression level of Pax7 genes and MRF factors for both factors. However, a statistically higher Pax7 and Myf5 gene expression level was revealed when a low glucose medium was used (p < 0.05). In conclusion, the components of the medium, such as bovine serum and the addition of a mitogenic factor at the level of 10 ng/mL, ensure a higher proliferation rate of BSCs and lower glucose content ensured the expression of crucial genes in the self-renewal of the satellite cell population. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the possibility of using two nonlinear models, i.e. the von Bertalanffy and Gompertz functions, for fitting growth curves of Popielno White and New Zealand White rabbits. The study was conducted using 37 Popielno White (21 male and 16 female) and 55 New Zealand White (28 male and 27 female) rabbits. The nonlinear regression procedure (NLIN) in SAS 9.4 software was used to model the rabbits’ growth curves from birth to 12 weeks of age. To see how rabbit growth might progress in subsequent weeks, we extrapolated the weights of the rabbits up to the age of 30 weeks. Six criteria were used to compare models: mean error, mean squared error, mean absolute error, quotient between the error sum of squares and observed sum of squares, corrected Akaike information criterion, and Bayesian information criterion. The shape of all curves was sigmoid, and both models fitted well to the data from birth to 12 weeks of age, i.e. during the interpolation process. A problem with the fit occurred later, during the extrapolation process, i.e. when the models were used to predict the animals’ course of growth in subsequent weeks. When body weight was extrapolated in later weeks of life, the fitting of the von Bertalanffy model was slightly worse, and asymptotic body weight was overestimated. To predict the further course of rabbit growth in practice, the Gompertz function would be a better choice. The Gompertz model could also be a helpful tool for breeders to describe the growth process of rabbits and to select a more economically profitable breed. [ABSTRACT FROM AUTHOR]

Leptin is a hormone synthesized and secreted primarily in adipose cells that help to regulate energy balance. This study examined the associations of single nucleotide polymorphisms in the rabbit leptin gene with growth traits, slaughter traits and physicochemical parameters of New Zealand White (NZW) and Belgian Giant Grey (BGG) crossbreed rabbits. In total, 320 crossbreed animals were genotyped for polymorphisms within exon 2—g.16081633T>C,intron 1_2—g.16081420C>T,and within UTR—g.16079636C>Gfor association analysis. Identified polymorphisms within rabbits leptin gene showed significant differences for dissectible fat percentage in carcass and dissectible fat weight in intermediate part (g.16081633T>C). Moreover, meat traits like protein content (g.16081633T>C; g.16079636C>G), intramuscular fat content (g.16081633T>C; g.16079636C>G, g.16081420C>T), dry matter (g.16081420C>T),ash (g.16081420C>T),water (g.16081420C>T),and cohesiveness (g.16081420C>T, g.16079636C>G) were affected by polymorphisms in leptin gene. We conclude that polymorphism in the rabbit leptin gene influences important carcass and meat traits of NZW × BGG crossbreeds. Therefore, polymorphisms identified in this study may be used in selection as a meat trait markers. [ABSTRACT FROM AUTHOR]

The objective of this study was to estimate genetic correlations of lactose percentage and urea concentration in milk with conformation traits related to udder and legs of Polish Holstein-Friesian cows. Data consisted of 5,813 test-day records and type scores of 791 primiparous cows. The analysis involved two descriptive traits (udder, feet and legs, scored from 50 to 100) and 11 linearly scored traits (describing udder: fore udder height, rear udder height, central ligament, udder depth, udder width, fore teat placement, teat length, rear teat placement; describing legs: rear legs - side view, foot angle, rear legs - rear view; on a scale of 1 to 9). Genetic correlations were calculated based on (co)variances estimated using the Bayesian method via Gibbs sampling and the multitrait animal model. Genetic correlations between lactose content and conformation traits ranged from -0.18 to 0.23, while those between milk urea concentration and conformation traits ranged between -0.02 and 0.43, respectively. Absolute values of average genetic correlations with daily lactose percentage exceeded 0.15 only for udder (descriptive trait) and several linearly scored traits, i.e. central ligament, udder depth, rear teat placement, and rear legs - rear view. Milk urea content was weakly or moderately genetically correlated with six type traits: udder, and five linearly scored traits: fore udder height, central ligament, udder width, teat length, and rear legs - side view. Absolute values of genetic correlations between these traits exceeded 0.15. Our results showed that type traits connected with udder were more highly genetically correlated with both lactose and milk urea contents than type traits describing legs. It meant that an increase in both lactose percentage and urea concentration in milk might be expected as an indirect response to selection for better udder, whereas selection for improvement of legs would not affect lactose percentage and milk urea content. [ABSTRACT FROM AUTHOR]

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The objective of the study was to estimate genetic parameters for lactose percentage and urea concentration in milk of Polish Holstein-Friesian cows. Data consisted of 104,875 test-day records from the first three lactations of 6,299 cows. Genetic parameters were estimated using the Bayesian method via Gibbs sampling and the multitrait animal model. The linear model for lactose percentage, milk urea content and production traits (milk yield, fat percentage, protein percentage) included the fixed herd-test-day effect, fixed regressions within age at calving by season of calving subclasses, and random regressions for additive genetic and permanent environmental effects. All regressions were modeled using fourth-order Legendre polynomials. The average daily heritability of lactose percentage was on an intermediate level and ranged from 0.24 to 0.35. Average daily heritability of milk urea concentration was lower (0.16 to 0.24). Lactose percentage was positively genetically correlated with milk yield (0.29, 0.29 and 0.34 in first, second and third lactations, respectively) and negatively genetically correlated with protein percentage (-0.21, -0.19, -0.13 in lactations 1, 2 and 3), and fat percentage in the first lactation (-0.24). Genetic correlations of milk urea concentration and other milk traits (fat, protein and lactose percentages) were rather low or close to zero (-0.16 to 0.19), except for the genetic correlation with milk yield (0.19 to 0.35). The results show that selection for lactose percentage and milk urea content is possible, although more research on the relationship with other traits, mainly conformation, fertility and health, is needed. [ABSTRACT FROM AUTHOR]

The objectives of this study were (1) to examine different shapes of lactation curves when the Wilmink function is fitted to test-day yields, and (2) to analyze the relationships between lactation curve shape and factors determining it in Polish Holstein-Friesian (HF) cows. Test-day milk yields were collected for 1,359,040 Polish Holstein-Friesian cows that calved from 1995 to 2008. A multipletrait prediction (MTP) procedure was used to fit individual lactation curves and estimate partial, peak and 305-d lactation yields using the Wilmink function. The Wilmink function was able to model two groups of lactation curves: standard and atypical. Atypical curves were found more often in later lactations rather than first lactations of Polish HF cows. For standard curves, peak yields (on average, about 23 kg in the first and 28-30 kg in later parities) occurred at around 38 days in milk (DIM) in the first lactations and 30 DIM in later lactations. For atypical curves, mean milk yields at peak were similar in value. Milk yield recording should start as early as possible, because the distance between the first test and calving is the factor that significantly affected the occurrence of atypical lactation curves. An effect of season and parity on the occurrence of atypical curves also was observed in the Polish Holstein- Friesian population. The effect of season was especially noticeable for cows that calved between April and September with only one yield recorded. [ABSTRACT FROM AUTHOR]

The objectives of this study were to analyze the genetic properties of three measures of lactation persistency in Polish Holstein-Friesian cows, and possibly to choose one measure which could be used for estimation of breeding value for lactation persistency in the Polish dairy cattle population. Data included 117,327 first three lactations of 110,141 cows calved in 1995-2009. The lactation curve model of Ali and Schaeffer was fitted to test-day milk yields. The first definition of persistency (P2:1) was milk yield in the second 100 days in milk (DIM) divided by yield in the first 100 DIM. The second definition (P3:1) was milk yield in the third 100 DIM divided by yield in the first 100 DIM, and the third definition (Pd) was milk yield at 280 DIM divided by milk yield at 60 DIM. The multipletrait REML method was applied for (co)variance component estimation. Heritabilities for three measures of persistency were very low, and ranged from 0.01 to 0.08. Genetic correlations were highest between P3:1 and Pd (0.96-0.99), and lowest between P2:1 and Pd (0.66-0.81), in the first three lactations. The correlations between 305-d milk yield and P3:1 or Pd in each of the first three lactations, and P2:1 in the second lactation, were negative and moderate. The phenotypic correlations between 305-d milk yield and persistency measures were low in the first three lactations. The phenotypic correlation between milk yield and Pd in each lactation was almost the same (0.14-0.15); the correlation between milk yield and P3:1 (0.11-0.17) or P2:1 (0.08-0.13) showed little variation in the first three lactations. All three compared measures of persistency were low-heritable and practically uncorrelated with total milk yield of 305-d lactations, so any of them could be used in the breeding program. However, the Pd measure could be recommended for use in practice because it is easy to calculate and interpret. [ABSTRACT FROM AUTHOR]

Rabbits are important livestock animals, popular for their nutritional value. Nowadays, the molecular background of traits influencing the quality of meat and meat products is in high demand. Therefore, in the current study, we analyse the sequences of IGFBP1 , IGFBP2 , IGFBP4 , IGFBP5 , and IGFBP6 for possible polymorphisms. Based on a bioinformatics analysis in an association study on 466 animals of different breeds (New Zealand White × Flemish Giant crossbreed (9NZWxFG), Termond White (TW), Popielno White (PW), and Flemish Giant (FG)), we analyse the influence of five polymorphisms within the IGFBP genes. Statistically significant differences were found among the carcass and meat quality traits but not for all of the analysed rabbit breeds. The most promising polymorphism was g.158093018A>T within the IGFBP5 gene. The values of pH24 of m.longissimus lumborum (m.l.l.) and biceps femoris muscles (m.b.f.) were higher for the AT genotypes compared to the AA genotypes for the TW and NZWxFG crossbreeds. Also, for pH24, we found differences in ing.41594308T>C for NZWxFG, where the TT genotype values were higher than the TC values. We found differences in L*24 on m.l.l. for g.41592248A>C for NZWxFG. For m.b.f., significant differences were found in b*45 for g.3431insAC in the FG population and a*45 for g.41592248A>C and g.158093018A>T in the TW population. The shear force statistically differed for g.158093018A>T in TW rabbits and g.41592248A>C for NZWxFG. We conclude that this polymorphism may be promising for better quality rabbit meat and may be implemented in selection processes.