Dietary energy source in dairy cows in early lactation: energy partitioning and milk composition

Metabolic problems related to negative energy balance suggest a role for the balance in supply of lipogenic and glucogenic nutrients. To test the effect of lipogenic and glucogenic nutrients on energy partitioning, energy balance and nitrogen balance of 16 lactating dairy cows were determined by indirect calorimetry in climate respiration chambers from wk 2 to 9 postpartum. Cows were fed a diet high in lipogenic nutrients or a diet high in glucogenic nutrients from wk 3 prepartum until wk 9 postpartum. Diets were isocaloric (net energy basis) and equal in intestinal digestible protein. There was no effect of diet on metabolizable energy intake and heat production. Cows fed the lipogenic diet partitioned more energy to milk than cows fed the glucogenic diet [1,175 +/- 18 vs. 1,073 +/- 12 kJ/(kg(0.75) x d)] and had a higher milk fat yield (1.89 +/- 0.02 vs. 1.67 +/- 0.03 kg/d). The increase in milk fat production was caused by an increase in C16:0, C18:0, and C18:1 in milk fat. No difference was found in energy retained as body protein, but energy mobilized from body fat tended to be higher in cows fed the lipogenic diet than in cows fed the glucogenic diet [190 +/- 23 vs. 113 +/- 26 kJ/(kg(0.75) x d)]. Overall, results demonstrate that energy partitioning between milk and body tissue can be altered by feeding isocaloric diets differing in lipogenic and glucogenic nutrient content.

Effect of Glucogenic vs. Lipogenic Diets on Energy Balance, Blood Metabolites, and Reproduction in Primiparous and Multiparous Dairy Cows in Early Lactation

Increasing the availability of glucogenic nutrients relative to lipogenic nutrients has been hypothesized to decrease the production of milk fat, to improve the energy balance (EB), and to decrease the incidence and severity of metabolic and reproductive disorders in dairy cows in early lactation. Therefore, our objective was to evaluate the effects of a glucogenic, lipogenic, or mixed diet on EB, plasma metabolites and metabolic hormones, liver triacylglycerides (TAG), and reproductive variables in high-producing dairy cows in early lactation. Cows (n = 114) were randomly assigned to 1 of 3 diets and were fed either a mainly lipogenic diet, a mainly glucogenic diet, or a mixture of both diets (50:50 dry matter basis) from wk 3 before the expected calving date until 9 wk postpartum. Diets were isocaloric (net energy basis) and equal in intestinal digestible protein. Dry matter intake, net energy intake, milk yield, and milk protein percentage did not differ among diets. Milk lactose percentage was less for cows fed the lipogenic diet. Milk fat percentage was less for multiparous cows fed the glucogenic diet compared with cows fed the mixed or lipogenic diet (3.69 vs. 4.02 vs. 4.22 +/- 0.07%, respectively). The calculated EB was less negative for multiparous cows fed the glucogenic diet compared with cows fed the mixed or lipogenic diet [-33 vs. -125 vs. -89 +/- 21 kJ/(kg(0.75) x d), respectively]. Postpartum, the glucogenic diet decreased plasma nonesterified fatty acids, beta-hydroxybutyrate, and liver TAG concentrations and increased insulin concentration in multiparous cows. The glucogenic diet tended to decrease the number of days until first milk progesterone rise in multiparous cows compared with the mixed or lipogenic diet (20.4 vs. 24.4 vs. 26.4 +/- 2.1 d, respectively). Diet had no effect on any of the above-mentioned variables in primiparous cows, except that milk lactose percentage was greater for primiparous cows fed the glucogenic diet. We concluded that the glucogenic diet was effective in improving the calculated EB and decreasing plasma beta-hydroxybutyrate and liver TAG concentrations, suggesting a reduced risk of metabolic disorders in multiparous dairy cows fed a glucogenic diet.

Digestion of feed amino acids in the rumen and small intestine of dairy cows measured with nylon-bag techniques

The disappearance of total N, non-protein-N and amino acid-N after washing, rumen incubation and intestinal passage of sugarbeet pulp, maize-gluten feed, maize feed meal, palm kernel meal, soyabean hulls, soyabean meal, grass silage, maize silage and concentrate was measured in four dairy cows using nylon-bag techniques. Disappearance of amino acid-N after washing varied between feedstuffs from 14 to 69% of feed amino acid-N, and was lower than disappearance of non-protein-N. For sugarbeet pulp, grass silage and maize silage, washing had a considerable effect on the amino acid profile. Disappearance of amino acid-N after rumen incubation was also lower than non-protein-N and varied between feedstuffs from 25 to 73% of feed amino acid-N. Rumen incubation had only a small effect on the amino acid profile of the residue after washing. Disappearance of amino acid-N in the intestine varied between feedstuffs from 70 to 99% of rumen undegraded amino acid-N, and was higher than the disappearance of non-protein-N. Intestinal incubation showed a considerable effect on the amino acid profile for all feedstuffs. It was concluded that protein that was assumed to escape rumen degradation and was absorbable in the intestine was higher in amino acids and methionine, and lower in non-amino acid-N and glutamic acid and proline compared with protein in the feedstuff.