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Communication Dans Un Congrès Année : 2020

Dietary restriction of dairy cows: a lever to study the lipolytic system in milk and mammary gland

Résumé

Milk lipolysis is defined as the hydrolysis of triglycerides, the major component of milk fat. Short-chain fatty acids released in milk are responsible for rancid flavour. In addition, the presence of partial glycerides impairs milk functional properties such as foaming and creaming abilities. Milk lipolysis represents an important criterion to assess the quality of milk and depends on both animal parameters and breeding factors. Low-energy diets were found to be associated with higher levels of spontaneous lipolysis, particularly in late lactation. In our experiment, dairy cows were fed a diet at 65% of their dry matter ingested ad libitum to induce spontaneous lipolysis in milk and for studying milk composition associated with lipolysis. Two groups of 22 cows (165±16 days in milk, half primiparous cows) received either a control diet (100% of the dry matter intake ad libitum) or the experimental diet according to a 2×2 cross-over design. Lipolysis was analysed by the copper-soap method. Milk fat globule and casein micelles size distributions were evaluated by laser light scattering. The duration of the restriction was 5 days. The statistical model used was the MIXED procedure of SAS. As expected, feeding restriction caused an increase in spontaneous lipolysis of milk (+0.20 Meq/100 g of fat, P<0.01). At the same time, milk yield and protein content decreased (-5.1 kg/d and -1.3 g/kg respectively, P<0.01) whereas no effect was observed on milk fat content. The increase in spontaneous lipolysis was associated with an increase in the diameter of milk fat globules (+0.17 μm, P<0.05) without effect on the diameter of casein micelles. Dietary restriction induced changes in parameters of the metabolism of dairy cows with an increase in plasma non-esterified fatty acids, triglycerides and urea, indicators of the mobilisation of body fat and the catabolism of proteins associated with dietary restriction. This zootechnical approach will be enriched by proteomics and transcriptomics approaches applied to milk and/or mammary gland on a set of animals selected for being extreme in term of lipolysis.
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Dates et versions

hal-03131056 , version 1 (04-02-2021)

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  • HAL Id : hal-03131056 , version 1

Citer

Catherine Hurtaud, Laurence Bernard, Marion Boutinaud, Christelle Cebo. Dietary restriction of dairy cows: a lever to study the lipolytic system in milk and mammary gland. 71. Annual Meeting of the European Federation of Animal Science (EAAP), EAAP, Dec 2020, Virtual meeting, Portugal. ⟨hal-03131056⟩
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