Abstract
The objective of this study was to determine the effects of milk fat depression induced by supplementing conjugated linoleic acid (CLA; trans-10,cis-12 and cis-9,trans-11 CLA) or feeding a higher starch and oil-containing diet (HSO) on metabolic changes in dairy cows after calving. The main hypothesis was that the 2 strategies to decrease milk fat yield could have different effects on performance, energy balance (EB), and inflammatory status in early lactation. Thirty-three Nordic Red dairy cows were used in a randomized block design from 1 to 112 d of lactation and fed one of the following treatments: control (CON), CLA-supplemented diet, or HSO diet. Dry matter intake and milk yield were measured daily whereas milk composition was measured weekly throughout the experiment. Nutrient digestibility, EB, and plasma hormones and metabolites were measured at 3, 7, 11, and 15 wk of lactation in respiration chambers. The HSO diet led to lower intakes of dry matter, neutral detergent fiber, and gross energy compared with CON and CLA diets. The CLA diet and especially the HSO diet resulted in lower energy-corrected milk yield during the first 7 wk of lactation than those fed CON. The EB was numerically higher for HSO and CLA diets compared with CON at wk 3 and 7. Plasma glucose concentration was higher by the CLA diet at wk 3 and by the HSO diet from wk 3 to 15 compared with CON. Plasma nonesterified fatty acids were higher at wk 3 in the CON group (indicating more lipid mobilization) but decreased thereafter to similar levels with the other groups. The HSO-fed cows had higher plasma ceruloplasmin, paraoxonase, and total bilirubin concentrations in the entire experiment and showed the highest levels of reactive oxygen metabolites. These results suggest an increased inflammatory and oxidative stress state in the HSO cows and probably different regulation of the innate immune system. This study provides evidence that milk fat depression induced by feeding HSO (as well as CLA) decreased milk fat secretion and improved EB compared with CON in early lactation. The increase in plasma glucose and paraoxonase levels with the HSO diet may imply a better ability of the liver to cope with the metabolic demand after parturition. However, the negative effect of HSO on feed intake, and the indication of increased inflammatory and oxidative stress warrant further studies before the HSO feeding strategy could be supported as an alternative to improve EB in early lactation.
Highlights
Feed intake is often inadequate during early- to mid-lactation to support the rapid increase in energy required for milk production resulting in negative energy balance (EB) affecting health, production, and reproductive performance (Grummer, 1993)
This study provides evidence that milk fat depression induced by feeding higher starch and oilcontaining diet (HSO) decreased milk fat secretion and improved EB compared with CON in early lactation
Energy metabolism was measured using indirect open-circuit respiratory chambers for half of the cows (n = 16) whereas for the rest of the cows (n = 17), it was estimated based on the same partitioning of gross energy (GE) intake for methane and heat production as their counterparts within each diet and chamber period in addition to the measured feed intake, milk yield, and total feces and urine DM contents in the metabolic units
Summary
Feed intake is often inadequate during early- to mid-lactation to support the rapid increase in energy required for milk production resulting in negative energy balance (EB) affecting health, production, and reproductive performance (Grummer, 1993). Milk fat depression (MFD) might improve negative EB during the transition period by partitioning the energy spared from milk fat synthesis toward body reserves (Moore et al, 2004; Harvatine et al, 2009), especially if feed intake (Boerman et al, 2015), health conditions, and immune or oxidative status (Mazzetti et al, 2020) are not compromised. A maximum 50% reduction in milk fat synthesis has been observed during diet-induced MFD (i.e., feeding high-concentrate or high PUFA diets; Bauman and Griinari, 2003) and in dose-response studies with abomasal infusion of trans10,cis-12 CLA isomer (Baumgard et al, 2002; de Veth et al, 2004; Haubold et al, 2020). The effects of dietary CLA supplements on EB and feed intake during early lactation are inconsistent (Bernal-Santos et al, 2003; Moallem et al, 2010; Schäfers et al, 2017)
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