Effects of supplemental energy sources and <Emphasis Type="Italic">trans</Emphasis>-10, <Emphasis Type="Italic">cis</Emphasis>-12 conjugated linoleic acids (CLA) on milk yield and composition in lactating Holstein cows |
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Authors: | Xueyan Lin Guoyi Liang Pengcheng Su Zhonghua Wang |
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Institution: | (1) Laboratory of Molecular Signaling, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, 20892-9410 Bethesda, Maryland, USA;(2) School of Bio-Resources and PNU-Special Animal Biotechnology Center, Pusan National University, 627-706 Miryang, South Korea;(3) College of Agriculture, Life & Environment Sciences, Chungbuk National University, 361-763 Cheongju, South Korea;(4) School of Agricultural Biotechnology, Seoul National University, 151-921 Seoul, South Korea |
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Abstract: | The effects of supplemental energy sources (corn or saturated fatty acids) and trans-10, cis-12CLA on milk yield and composition were investigated in the present study. Four multiparous Holstein cows (560±31 kg BW,
98±10.5 DIM) were designated to a 2×2 factorial 4×4 Latin Square experiment. Treatments were isoenergetic supplementation
of corn or calcium salt of saturated fatty acids (CaFA) with or without calcium salt of CLA. Both milk yield and composition
were affected by sources of supplemental energy. Compared to CaFA supplementation, corn supplementation increased the milk
yield, the lactose yield, and the content and yield of milk protein but decreased the yield and content of milk fat. Plasma
insulin was higher, plasma glucose tended to be higher, and plasma non-esterified fatty acid (NEFA) was lower when corn rather
than CaFA was supplemented. CaCLA supplementation did not affect milk yield and the yield of measured milk components, but
increased the content of milk protein and decreased the content of total solids. Plasma glucose was decreased by CaCLA supplementation.
Content and yield of short and medium chain fatty acids (⩽16 carbon atoms) in milk fat increased or remained unchanged while
those of long chain fatty acids (> 16 carbon atoms) decreased or remained unchanged by corn supplementation. CaCLA supplementation
failed to increase the content and yield of trans-10, cis-12CLA in milk fat, which explained the unobserved depression of milk fat synthesis by CaCLA supplementation. Yields of de novo synthesized fatty acids in the mammary gland were increased rather than decreased by corn supplementation. The decreased
milk fat yield by corn supplementation could be exclusively attributed to reductions in preformed fatty acids, which might
be a result of depressed lipolysis by stimulated insulin secretion. |
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