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Communication Dans Un Congrès Année : 2023

Altering nutrients supply modified dynamics of milk components synthesis in dairy cows

Résumé

This study aimed to analyse the dynamics of milk component synthesis in response to increasing starch and balancing amino acids (AA) during mid-lactation in dairy cows. We hypothesized that altering the nutrient supply could modify the persistency of lactose, protein, and fat differently. Thirty-two multiparous dairy cows were involved in a randomized complete block design. They received 2 levels of starch (LS: low starch; HS: high starch) and 2 levels of AA supplies (AA- vs AA+) through rumen-protected AA according to a factorial design from 56 to 180 days in milk (DIM). The LS and HS diets provided (in g/kg DM) 155 vs 233 of starch, 384 vs 380 of NDF, 138 vs 142 of CP, 89.5 vs 94.5 of MP, and 6.54 vs 6.20 MJ/kg, respectively. The AA- vs AA+ diets were formulated to provide [in % of MP]: 6.4 vs 7.1% Lys, 2.0 vs 2.4% Met, and 2.1 vs 2.4% His, respectively. Milk protein and fat contents were measured twice a week, and lactose content once a week. Milk lactose, protein, and fat yields were modelled by linear regression with DIM, starch, AA, and covariates as predictors, and cow as a random effect. The slope of each milk component model was assumed to be an estimator of persistency. Lactose and protein yields were higher on HS than on LS diets (1,708 vs 1,895 g; P<0.001; 1,085 vs 1,201 g; P<0.001, respectively). The slope of lactose, protein, and fat yields models were higher on HS than on LS diets (-3.41 vs -1.41 g/d, P<0.001; -1.31 vs 0.29 g/d; P<0.001; -2.43 vs -0.43 g/d, P<0.001, respectively). This effect could be due to the stimulation of mammary synthesis by starch or by slightly higher supply of MP in the HS diet. Balancing AA increased the slope of lactose yield (-2.78 vs -2.04 g/d, P=0.01), however the effect tended to be not additive (at LS level: -4.05 vs -2.77 g/d; at HS level: -1.50 vs -1.31 g/d; AA × starch on slope: P=0.06). With the LS diet, balancing AA tended to increase the slope of fat yield (at LS level: -2.90 vs -1.96 g/d, AA × starch on slope: P<0.05). These results suggest that increasing starch or better balancing AA increased the persistency of milk components.
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Dates et versions

hal-04251470 , version 1 (20-10-2023)

Identifiants

  • HAL Id : hal-04251470 , version 1

Citer

Jean-Charles Anger, Christelle Loncke, Romain Bidaux, Sophie Lemosquet. Altering nutrients supply modified dynamics of milk components synthesis in dairy cows. 74. Annual meeting of the european federation of animal science (EAAP), EAAP, Aug 2023, Lyon, France. pp.837. ⟨hal-04251470⟩
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