Browsing by Author "Spain, James Nobles"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Effect of protein source on milk composition of cows fed low fiber, high grain diets
    Spain, James Nobles (Virginia Tech, 1987)
    Thirty primiparous Holstein cows in mid lactation (106± 24 d) were randomly assigned to one of six diets in an incomplete block design. Each cow received two of six diets. Cows received the first diet for 32 d, then were offered a different diet for 32 d. received two of six diets. There were 5 observations per diet per period for a total of ten observations per treatment. Diets were 12% CP soybean meal (LSB), 20% CP soybean meal (HSB), 20% CP fishmeal (FM), 20% CP corn gluten meal (CG), 20% CP CG:SB, and 20% CP FM:SB. All diets were > 75% TDN and ~ 16% acid detergent fiber. Milk yield was not different between treatments. Milk fat percent, milk lactose percent, and fat corrected milk yield were higher in cows on CG (3.13%, 5.30%, 23 kg) in contrast to cows receiving FM (2.11%, 5.00%, 20.5 kg). Milk protein percent was not different, but milk protein yield was different across treatments. Rumen ammonia concentrations differed significantly with HSB (13.5 mg/dl) higher than LSB (7.33 mg/dl), indicating the increase in ruminally degraded protein. Plasma urea concentrations reflected rumen ammonia concentrations with HSB (16.2 mg/dl) higher than LSB (6.4 mg/dl). Results suggest that protein source can affect milk composition in cows fed low fiber diets.
  • Thumbnail Image
    Evaluating fish meal as a protein source for lactating dairy cows
    Spain, James Nobles (Virginia Polytechnic Institute and State University, 1989)
    A series of experiments were conducted to measure the mode of action by which fishmeal exerts its effect on milk composition of dairy cows. Production Study One measured the effect of increased fishmeal intake on milk production and milk composition in dairy cattle. Milk fat percentage and yield were decreased by increased fishmeal intake. This decrease was not associated with changes in ruminal fermentation patterns. Plasma long-chain n-3 polyunsaturated fatty acids were increased with increased fishmeal intake. Mammary slices from lactating bovine mammary gland were incubated with eicosapentaenoic acid. Changes in ¹⁴C-acetate metabolism were measured. Acetate oxidation and incorporation into milk lipid were not changed by eicosapentaenoic acid. However, tissue from mammary gland of cows milked 6 to 8 h prior to slaughter had 2 fold higher activity than tissue milked 1 h before slaughter. Disappearance of dry matter, crude protein, and lipid in fish meal from undegradable bags in the rumen was measured. Dry matter and crude protein degradation of fish meal were similar to published values. Lipid escaped rapidly with greater than 70% removed by 8 h. A subsequent fish oil infusion study revealed that intraruminal fish oil treatment did not significantly alter ruminal fermentation, or change fatty acid profiles in duodenal digesta, plasma, or milk. Duodenal infusion increased plasma concentrations of n-3 fatty acids but did not affect milk lipid fatty acid composition. A second production study compared the effects of fish meal versus fish oil on milk production and composition, and changes in fatty acids in plasma and milk. Fish meal significantly increased plasma n-3 fatty acids compared to the fish oil treatment. Residual fatty acids contained in fish meal seemed to be protected from rumen degradation and probably remained intact for digestion and absorption since plasma n-3 fatty acid concentrations increased. No changes in milk yield or composition were due to the experimental treatments. Fat in fish meal and fish oil source differed significantly in their ability to alter milk composition and plasma fatty acid profiles.