Search

Residual feed intake (RFI) is an efficiency trait underpinning profitability and environmental sustainability in dairy production. This study compared performance during a complete lactation of 36 multiparous dairy cows divided into three equal-sized groups with high (HRFI), intermediate (IRFI) or low RFI (LRFI). Residual feed intake was determined by two different equations. Residual feed intake according to the NorFor system was calculated as (RFINorFor) = (NEintake)–(NEmaintenance + NEgestation + NEmilk—NEmobilisation + NEdeposition). Residual feed intake according to the USA National Research Council (NRC) (RFINRC) was calculated as: RFI = DMI − predicted DMI where predicteds DMI = [(0.372× ECM)+(0.0968×BW0.75)]×(1−e−0.192×(DIM/7+3.67)). Cows in the HRFINorFor group showed higher daily CH4 production, CH4/ECM and CH4 yield (g/kg DMI) than IRFINorFor and LRFINorFor cows. Cows characterized by high efficiency (LRFINorFor) according to the NorFor system had lower body weight. Dry matter intake and apparent dry matter digestibility were not affected by efficiency group but milk yield was lower in the low efficiency, HRFINorFor, group. Cows characterized by high efficiency according to the NRC system (LRFINRC) had lower dry matter intake while yield of CH4 was higher. Daily CH4 production and CH4 g/kg ECM did not differ between RFINRC groups. Dairy cows characterized by high efficiency (both LRFINorFor and LRFINRC cows) over a complete lactation mobilized more of their body reserves in early lactation as well as during the complete lactation. The results also indicated great phenotypic variation in RFI between different stages the lactation. [ABSTRACT FROM AUTHOR]

Ruminants can produce meat and milk from fibrous feed and byproducts not suitable for human consumption. However, high-yielding dairy cows are generally fed a high proportion of cereal grain and pulses, which could be consumed directly by humans. If high production of dairy cows could be maintained with ingredients of low human interest, the sustainability of dairy production would improve. In the present study, 37 multiparous [Holstein (n = 13) and Swedish Red (n = 24)] dairy cows were followed over a whole lactation. A low-concentrate diet of up to 6 kg concentrate per day (6kgConc) was fed to 27 cows, whereas 10 cows were fed a high-concentrate diet of up to 12 kg concentrate per day (12kgConc). The concentrate was mainly based on byproducts (sugar beet pulp, wheat bran, rapeseed meal, distiller's grain). Grass-clover silage of high digestibility was offered ad libitum. Over the whole lactation, cows on the 6kgConc diet had lower dry matter intake and higher forage intake than cows on the 12kgConc diet. Milk yield and energy balance were not influenced by dietary treatment. However, the cows on the 6kgConc diet numerically produced 2.4 kg less energy-corrected milk than cows on 12kgConc diet. The study lacked the statistical power to identify treatment effects on daily yield below 2.8 kg of milk due to low number of animals per treatment. Feed efficiency (as energy-corrected milk yield/dry matter intake or residual feed intake), body weight change, body condition change, milk fatty acid concentration in total milk fatty acids, plasma nonesterified fatty acids, glucose, β-hydroxybutyrate, and fertility measurements were not affected by diet, supporting the energy balance results. However, higher plasma concentrations of insulin-like growth factor-1 and insulin were observed in cows fed the 12kgConc diet. These findings show that cows can adapt to a high-forage diet virtually without human-grade ingredients, without compromising feed efficiency or energy balance, thereby contributing to sustainable food production. [ABSTRACT FROM AUTHOR]

• Effect of high and low levels of byproduct-based concentrate was studied. • Highly digestible grass-clover silage was fed ad libitum. • Dry matter intake or energy-corrected milk yield were not affected by diet. • Energy balance or metabolic indicators in blood or milk were not affected by diet. • Multiparous cows seemed to use more adipose tissue to support milk production. Dairy cows can produce highly nutritive food products (milk, meat etc.) from fibrous feed e.g. grass and different byproducts from the food and fuel industry, that cannot be consumed directly by humans. However, as there are limited amounts of byproducts available, decreasing the amount of byproduct-based concentrate in the diet could be a strategy for improving sustainability within dairy production if high milk production should be maintained. In this study, 26 multiparous (n = 14) and primiparous (n = 12) dairy cows of the breeds Swedish Red (n = 14) and Swedish Holstein (n = 12) were followed between lactation weeks 1 and 6. They were fed either a low-concentrate (n = 13; LC) or high-concentrate (n = 13; HC) byproduct-based (sugar beet pulp, rapeseed meal, distiller's grain, wheat bran) ration, in combination with highly digestible grass-clover silage ad libitum. To achieve similar concentrate intake per kg body weight in primiparous and multiparous cows, multiparous cows were offered 5 kg concentrate on the LC diet and 15 kg concentrate on the HC diet, while primiparous cows were offered 4 kg concentrate on the LC diet and 14 kg concentrate on the HC diet as target concentrate rations. We found no overall differences in dry matter intake, energy-corrected milk yield, energy balance, blood plasma metabolites, blood hormones or milk fatty acids between cows on the LC and HC diets. However, HC cows had a higher yield of ECM in lactation week 6 and gained body weight compared with LC cows. As expected, multiparous cows had higher dry matter intake and energy-corrected milk yield, but we found no difference in energy balance between parities. However, multiparous cows lost more body condition and had higher blood plasma concentrations of non-esterified fatty acids, indicating that they used more body tissue to support milk production. In conclusion, both multiparous and primiparous Swedish Red and Swedish Holstein dairy cows seem able to adapt to low-concentrate diets in early lactation when the diets are based on byproducts and grass-clover silage, providing the potential to increase sustainability in dairy production. [ABSTRACT FROM AUTHOR]