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Gestation length (GL) can potentially affect health and performance of both the dam and the newborn calf, and it is controlled by two genetic components, direct and maternal. This means that both the calf (direct effect) and the cow (maternal effect) genotypes contribute to determine GL and its variability. The aims of the present study were to estimate direct and maternal variance components of GL, develop a routine genetic evaluation of GL in Italian Holstein and evaluate potential (un)favourable associations with traits for which selection is undertaken in this population. A multiple‐trait repeatability linear animal model was employed for the estimation of variance components considering GL in first and later parities as different traits. The posterior mean (PM) of heritability of the direct effect was 0.43 for first parity and 0.35 for later parities. The PM of heritability of the maternal effect was lower, being 0.08 for primiparae and 0.06 for pluriparae. The posterior standard deviation (PSD) of the heritability estimates was small, ranging from 0.001 to 0.005. The relationship of direct and maternal effects with important traits such as milk yield and fertility indicated that selecting for extreme GL, longer or shorter, may have negative consequences on several traits, suggesting that GL has an intermediate optimum in dairy cattle. In conclusion, this study reveals that selecting an intermediate GL in the Italian Holstein population is advisable. Although scarcely variable compared to other conventional traits for which Italian Holstein is selected, GL is heritable and a deeper knowledge can be useful for decision‐making at the farm level. [ABSTRACT FROM AUTHOR]

The present study aimed to evaluate analytical performances of radial immunodiffusion (RID) technique for the quantification of milk lactoferrin (LF), and to investigate the main sources of variation of LF concentration in individual milk samples of Holstein Friesian (HF, n = 1516) and Simmental (SI, n = 230) cows. Repeatability (RSDr) and reproducibility (RSDR) of RID method were assessed as relative standard deviation of 15 measurements within the same day and 45 measurements across 3 d, respectively. Sources of variation of milk LF were investigated through a mixed linear model which included the fixed effects of classes of stage of lactation and parity (and their interaction), cow breed, udder health status (UHS, based on somatic cell count and differential somatic cell count), and the random effects of the herd-test day nested within breed and the residual. Method performances were satisfactory in terms of repeatability (RSDr < 9%) and reproducibility (RSDR < 8%), suggesting that the RID can be considered as a consistent cow-side test for the quantification of milk LF. Milk LF was positively associated with somatic cell score (r = 0.40) and negatively with lactose content (r = −0.33). Lower concentration of LF was observed in milk of 'healthy' and 'susceptible' cows (13.03 and 12.87 mg/dL, respectively) compared to 'mastitic' and 'chronic' cows (17.91 and 17.33 mg/dL, respectively). In this light, milk LF has the potential to be a useful biomarker to detect early mastitis. Further research is advisable to deepen the association between milk LF content and observed clinical mastitis. Radial immunodiffusion method for milk lactoferrin quantification is repeatable and reproducible. Somatic cell count is positively associated with milk lactoferrin content. Milk lactoferrin is less concentrated in milk of healthy and susceptible than potentially mastitic and chronic cows. [ABSTRACT FROM AUTHOR]

This paper investigated sources of variation of milk fatty acid (FA, g/100 g total FA) profile routinely predicted by mid-infrared spectroscopy in Pinzgauer dual-purpose cattle breed. A total of 19,578 individual milk samples collected from 1232 cows and 77 herds between 2011 and 2014 were available for phenotypic characterisation. Data were analysed using a linear mixed model which included stage of lactation, parity and their interaction as fixed effects, and cow and herd-test-day as random effects. Milk yield averaged 20.87 kg/d, and means for fat, protein and casein were 4.01, 3.44 and 2.72%, respectively. Saturated FA (SFA), monounsaturated FA (MUFA) and polyunsaturated FA (PUFA) averaged 69.20, 25.43 and 3.19 g/100 g total FA, respectively. About half of the SFA were provided by C16:0 (31.24 g/100 g total FA), and almost all MUFA by C18:1 (22.18 g/100 g total FA). Fixed effects were significant in explaining the variation of the studied traits. Milk of first-parity cows had the lowest percentage of SFA, medium-chain FA and C14:0, and the greatest percentage of MUFA, PUFA, trans FA, short- and long-chain FA, and C18:1. Saturated FA, C14:0 and C16:0 increased from calving until 120 days in milk, whereas unsaturated FA, MUFA, PUFA, long-chain FA, C18:0 and C18:1 decreased. Although both parity and stage of lactation affected milk FA, greater variation was observed during lactation than among parities. [ABSTRACT FROM AUTHOR]

Population-level phenotyping is, for some traits, hardly achievable due to limitation of reference analyses. Mid-infrared spectroscopy (MIRS) is a quick and cost-effective laboratory technique allowing the prediction of innovative milk quality features on a large scale. The present study aimed at investigating factors associated with milk Ca, K, Mg, Na and P contents predicted by MIRS models on a large multi-breed spectral data set of 123,240 test-day records. Two dairy (Holstein-Friesian and Brown Swiss) and two dual-purpose (Simmental and Alpine Grey) cattle breeds were considered. Sources of variation of predicted milk mineral contents were studied using linear mixed models, including the fixed effects of breed, month of sampling, stage of lactation, parity and interactions between the main effects. Random factors were herd nested within breed, cow nested within breed and the residual. Calcium content was greater in milk of dual-purpose than dairy cattle breeds. Simmental cows produced milk with the greatest content of Ca and Na, and milk of Holstein-Friesian had the lowest P content. Variation of content of Ca, Mg, Na and P throughout lactations exhibited an opposite trend to that of milk yield, with the lowest values around the peak of lactation. On the other hand, K content mirrored the trend of milk yield. Multiparous cows had lower content of milk minerals, with the exception of Na, compared with first parity animals. Environmental factors identified in the present study can be considered for within-breed genetic evaluation to adjust records of milk mineral contents for these effects. [ABSTRACT FROM AUTHOR]

Aim of the project was to evaluate behavioral and productive variations of dairy cows detected by automatic monitoring systems, during different seasons. Environmental data (Temperature (T, °C), Relative Humidity, (RH, %) and Temperature and Humidity Index (THI)), were recorded inside the pens by electronic probes during 4 periods over 2 years, for a total of 473 days. Fans and sprinklers were activated at THI >60. Hundred lactating and dry cows were equipped with monitoring tag (Heatime-Pro, SCR Engineers Ltd.) that recorded continuously time (min/d) spent ruminating (RT), panting (PT) and feeding (FT). Daily PT and FT data were recorded as group average [lactating (LC) or dry], while RT and milk production were extracted as individual data. Four classes of environmental stress were identified based on maximum THI: comfort (C, THI < 60, 101d), moderate stress (MS, 60< THI >69, 92d), stress (S, 70< THI >75, 102d), severe stress (SS, THI >75, 178d). Behavioral and productive data were compared between classes. Data were analyzed by mixed model with repeated measures, with environmental class, group (dry or lactating), parity and interactions as fixed effect. Cow was included as random effect for RT and milk production. Means comparison was performed by Tukey post hoc test. All behavioral outcomes were influenced by heat stress (P < .001, table 1). Panting increased linearly with maximum THI recorded, being highest during SS days in LC (49.6 min/d, P < .001). FT and RT (min/d) were lowest (P < .001) during S days (206.9, FT and 473.1, RT) and RT reached the lowest values in cows within 15 DIM (456.4). Milk production was affected in multiparous cows, with a linear reduction from C to SS days (P < .001). Heat stress deeply affected cows behavior and performances, despite cooling systems. Automatic monitoring of these parameters can effectively help in detecting heat stress and consequently adopt strategies to improve animal welfare. [ABSTRACT FROM AUTHOR]