Animal Industry Report: Volume 650, Issue 1
The data demonstrate that cows with the genotypes κ- casein BB and β-lactoglobulin BB produce milk with a protein composition that is favorable for increased cheese yield. For proportions of αS1-casein, κ-casein, and β-lactoglobulin in total milk protein, κ-casein and β-lactoglobulin genotypes explained more than 50 and 25% of the heritability and repeatability estimates, respectively, and more than 14% of the phenotypic variance. Diet had only a minimal effect on milk protein composition. In conclusion, increasing cheese yield through modification of milk protein composition can be achieved most rapidly by selection for cows with κ-casein BB and β-lactoglobulin BB genotypes.
The effect of form of starter grain (coarse versus ground) and inclusion of various levels of hay on rumen development was evaluated. Two experiments were conducted to determine the effect of form of diet and forage inclusion on intake, growth, feed efficiency and weaning age in dairy calves. Diets consisted of commercial coarse starter (C), ground starter (G), coarse starter with 7.5% bromegrass hay of consistent particle size (8 - 19 mm) (H1), and coarse starter with 15% hay (H2). In experiment 1, intake was held constant across treatments until weaning, when feed was offered ad libitum. Calves receiving H1 and H2 were heavier, had greater body weight gain and greater feed efficiency than calves receiving C. There were no differences in intake. Total volatile fatty acid (VFA) concentrations were higher and the proportion of acetate was lower for calves fed G versus C. In experiment 2, calves (n = 56) were offered diets on an ad libitum basis and weaned according to intake. There were no differences in body weight gain, average daily gain, feed efficiency and age at weaning with respect to treatment. Starter and total dry matter intake tended to be greater in calves fed H1 and H2 versus C.
Addition of controlled particle size hay to diets of young calves appears to favorably alter rumen environment resulting in increased intake and improved feed efficiency. Forage of a consistent particle size can be successfully utilized in starter rations of young calves.
Dwarfism in American Angus was a major cause of concern in the 1970’s. Until recently when several calves from some sire x dam crosses resulted in phenotypically dwarf calves not cases have been observed since then. Six affected calves from 3 sire and 5 dam matings and unrelated normal Angus animals were genotyped for the presence of known mutations, which have been reported in Japanese brown and Australian Dexter cattle. We detected only wild-type alleles in dwarf and phenotypically normal Angus cattle, indicating that known mutations associated with Japanese brown cattle or Dexter dwarfism are not responsible for dwarfism in the American Angus breed. However, this does not preclude the possibility that novel mutations may have arisen in American Angus cattle. In order to begin to identify the causative mutation(s) for dwarfism, a whole genome scan of the affected American Angus pedigree is being pursued.