Phenotypic and genetic variability of production traits and milk fatty acid contents across days in milk for Walloon Holstein first-parity cows

• Published in: Journal of dairy science Vol. 94; no. 8; pp. 4152 - 4163
• Main Authors: Bastin, C., Gengler, N., Soyeurt, H.
• Format: Journal Article Web Resource
• Language: English
• Published: New York, NY Elsevier Inc 01.08.2011; Elsevier; American Dairy Science Association
• Subjects: animal models; Animal production & animal husbandry; Animal productions; Animals; Biological and medical sciences; body fat; breeding value; Cattle - genetics; Cattle - physiology; cows; diet; early lactation; energy balance; fatty acid; fatty acids; Fatty Acids - analysis; Female; Food industries; Fundamental and applied biological sciences. Psychology; genetic correlation; genetic variation; Genetic Variation - genetics; Genetics & genetic processes; Génétique & processus génétiques; herds; heritability; Holstein; Lactation - genetics; late lactation; Life sciences; mammary glands; milk; Milk - chemistry; Milk and cheese industries. Ice creams; milk fat; milk yield; Parity - genetics; Phenotype; physiological state; Pregnancy; Productions animales & zootechnie; Quantitative Trait, Heritable; random regression; Sciences du vivant; Terrestrial animal productions; Time Factors; Vertebrates; Belgium; fatty acid; milk fat; genetic correlation; random regression; Correlation; Genetic variability; Dairy cattle; Ox; Lipids; Production; Genetics; Milk fat; Parity; Ungulata; Milk; Farming animal; Dairy product; Regression; Cow; Fatty acids; Vertebrata; Mammalia; Content; Dairy industry; Artiodactyla; Day
• ISSN: 0022-0302; 1525-3198; 1525-3198
• DOI: 10.3168/jds.2010-4108

The objective of this study was to assess the phenotypic and genetic variability of production traits and milk fatty acid (FA) contents throughout lactation. Genetic parameters for milk, fat, and protein yields, fat and protein contents, and 19 groups and individual FA contents in milk were estimated for first-parity Holstein cows in the Walloon Region of Belgium using single-trait, test-day animal models and random regressions. Data included 130,285 records from 26,166 cows in 531 herds. Heritabilities indicated that de novo synthesized FA were under stronger genetic control than FA originating from the diet and from body fat mobilization. Estimates for saturated short- and medium-chain individual FA ranged from 0.35 for C4:0 to 0.44 for C8:0, whereas those for monounsaturated long-chain individual FA were lower (around 0.18). Moreover, de novo synthesized FA were more heritable in mid to late lactation. Approximate daily genetic correlations among traits were calculated as correlations between daily breeding values for days in milk between 5 and 305. Averaged daily genetic correlations between milk yield and FA contents did not vary strongly among FA (around −0.35) but they varied strongly across days in milk, especially in early lactation. Results indicate that cows selected for high milk yield in early lactation would have lower de novo synthesized FA contents in milk but a slightly higher content of C18:1 cis-9, indicating that such cows might mobilize body fat reserves. Genetic correlations among FA emphasized the combination of FA according to their origin: contents in milk of de novo FA were highly correlated with each other (from 0.64 to 0.99). Results also showed that genetic correlations between C18:1 cis-9 and other FA varied strongly during the first 100 d in milk and reinforced the statement that the release of long-chain FA inhibits FA synthesis in the mammary gland while the cow is in negative energy balance. Finally, results showed that the FA profile in milk changed during the lactation phenotypically and genetically, emphasizing the relationship between the physiological status of cow and milk composition.