VÝZNAM SLEDOVÁNÍ ZMĚN POMĚRU TUK/BÍLKOVINA V MLÉCE HOLŠTÝNSKÝCH DOJNIC

Milk samples of 24 pure-bred Holstein cows were taken during lactation and changes in milk fat to milk protein ratio and quality of rennet gel were evaluated. The cows were either fi rst (n=12) or second (n=12) calvers, in the same phase of lactation. The individual milk samples were taken on average on the day 25, 45, 73, 101, 133, 166, 199, 224, 253 and 280 of lactation and the following mean values of the F/P ratio were found: 1.91; 1.45; 1.38; 1.28; 1.22; 1.14; 1.26; 1.21; 1.09; 1.18. High values in the fi rst phase suggest a great energy defi ciency. The quality of rennet gel was also worst in the fi rst phase of lactation.V průběhu laktace byly odebírány vzorky od 24 čistokrevných holštýnských dojnic a hodnoceny změny poměru tuk/bílkovina a kvality sýřeniny. Dojnice se nacházely ve stejném počtu na první a druhé laktaci a byly ve stejném stádiu laktace. Odběr individuálních vzorků mléka probíhal v průměrném 25., 45., 73., 101., 133., 166., 199., 224., 253. a 280. dni laktace. Při jednolivých odběrech byly zjištěny tyto průměrné hodnoty poměru tuk/bílkovina: 1,91; 1.45; 1,38; 1,28; 1,22; 1,14; 1,26; 1,21; 1,09; 1,18. Vysoké hodnoty v první třetině laktace naznačují velký energetický deficit. V první třetině laktace byla též zjištěna nejhorší kvalita sýřeniny

Effect of season and herd on rennet coagulation time and other parameters of milk technological quality in Holstein dairy cows

In five herds of purebred Holstein dairy cows, altogether 220 bulk milk samples were collected with the following average parameters: rennet coagulation time (RCT) 265.2 sec., titratable acidity 6.40 °SH, active acidity 6.72 pH, specific density 1.0281 kg.l−1, fat content 3.81 g.100g−1, protein content 3.28 g.100g−1, lactose content 4.72 g.100g−1, and content of solids non-fat content 8.89 g.100g−1; average values of milk batch volume per herd and diurnal air temperature were 6,072 kg and 8.02 °C, respectively. It was found out that the variable “season“ (spring, summer, autumn or winter) significantly influenced nearly all parameters under study (the only exceptions were values of titratable acidity and milk batch volume). As compared with all other seasons, the significantly shortest RCT was recorded in summer. Further it was also found out that the variable “herd” influenced all parameters with the exception of average diurnal air temperature. Regardless to differences existing among individual herds, the shortest average RCT was recorded always in summer

Relationships Among Early Lactation Milk Fat Depression, Cattle Productivity and Fatty Acid Composition on Intensive Dairy Farms in Northern Italy

An observational study was conducted on three northern Italy Holstein dairy herds to evaluate the impact of milk fat depression (MFD, defined as milk fat lower than 3.2) on milk production and fatty acids (FA) composition in order to investigate the practical consequences and the possible origin of this phenomenon. The diet composition and the individual milk production and composition, were monitored during the first six months of lactation. Two virtual groups were created in each farm on the basis of the milk fat levels observed during the first two months of lactation (higher or lower than 3.2). Individual milk samples were taken from 16 animals /group/farm for composition and fatty acid analysis. The diet of Farm A, characterized by the highest average prevalence of MFD (33.1%), showed the highest acidogenic attitude (high NFC, low NDF, low peNDF8). The milk fat level differed significantly per group over time in all farms. Cattle with MFD showed tendentially lower energy corrected milk output and greater concentrations of C12:0÷C15:0, C18:1trans10, total polyunsaturated, total odd chain (OCFA), total n-6 as well as OCFA/branched chain fatty acids, and C18:1trans10/C18:1trans11 ratios. Farm A milk fat showed higher values of C12:0, C13:0, C14:0 and C15:0. It appears that MFD cattle are characterized by lower mammary energy output and a milk FA profile similar to cattle fed acidogenic diets, thus suggesting an alteration in the rumen fermentation patterns, as occurs in acidotic cattle

Genetic associations of test-day fat : protein ratio with milk yield, fertility, and udder health traits in Nordic Red cattle

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