Fresh cow nutrition

Performance improves when the diet is rich in metabolizable protein and balanced in terms of amino acids

After calving, cows must rapidly increase dry matter intake to meet nutrient requirements and support the rise in milk production.

During the first weeks of lactation, intake is not always sufficient to cover these demands and, consequently, cows mobilize body fat and protein reserves to sustain productive performance.

Recent research indicates that increasing the supply of metabolizable protein (MP) and balancing the amino acid (AA) profile of the fresh cow ration can increase voluntary intake, milk production, and help minimize body weight loss during the first weeks of lactation.

Researchers at Ohio State University evaluated four dietary strategies to identify the most effective way to increase metabolizable protein and balance amino acids in fresh cow rations. Both immediate results and carryover effects during the first 90 days of lactation were assessed.

The study

A total of 40 primiparous and 40 multiparous cows were enrolled in the trial. All cows received the same close-up diet before calving. After calving, cows were randomly assigned to one of four diets and fed until 25 days in milk (DIM). From 26 to 90 DIM, all cows were fed the same lactation diet containing 17% crude protein.

During the 3-week treatment period, the four experimental diets were:
– MP-deficient diet: 20% below MP requirements;
– MP-adequate diet: meeting MP requirements, with soybean meal as the main protein source;
– Mixed diet: meeting MP requirements, based on a mix of soybean meal, rapeseed meal, corn gluten meal, plus rumen-protected amino acids;
– Mixed diet with lower forage NDF (fNDF): meeting MP requirements but with reduced forage-derived NDF.

The mixed diet was formulated to ensure an adequate supply of rumen undegradable protein (RUP) and an amino acid profile similar to the essential amino acid profile of casein.

Bill Weiss, professor of dairy cattle nutrition at Ohio State University, explains that previous research (Schei et al., 2005) showed cows have a greater ability to mobilize body fat reserves to produce energy than to mobilize body protein. However, during early lactation, protein—not energy—is the primary limiting factor. Much recent research has focused on determining how much MP fresh cows require, how to meet these requirements while maintaining amino acid balance, and how to increase dry matter intake to achieve optimal performance.

This experiment was designed to address these questions and identify the nutritional strategy that works best in fresh cows.

Results

For several measured parameters, results were similar for both multiparous and primiparous cows. During the first 25 days of lactation, dry matter intake increased by approximately 1.10 kg/cow/day in all cows fed mixed diets compared with cows fed an MP-adequate diet based on a single protein source. In addition, all cows fed diets with the highest MP level increased milk yield, energy-corrected milk (ECM), and milk components by 6–7%, regardless of parity.

When forage NDF in the diet was reduced while maintaining a high MP level, multiparous and primiparous cows responded differently. Multiparous cows reduced dry matter intake and produced less milk, whereas primiparous cows increased both intake and milk production when fed the mixed diet with lower forage NDF.

This indicates that multiparous cows may have a higher requirement for forage-derived NDF than primiparous cows during early lactation. During the subsequent period (26 to 50 DIM), differences between multiparous and primiparous cows again emerged.

Multiparous cows showed greater intake and milk production when they had received the mixed diet at the start of lactation. In contrast, primiparous cows showed greater dry matter intake and improved productive performance when, during the fresh cow phase, they were fed the mixed diet with a lower forage NDF content.

When cumulative milk production at 92 DIM was evaluated, differences in intake and production between multiparous and primiparous cows related to forage NDF levels persisted.

The period from 26 to 92 DIM provides further evidence that multiparous cows have a higher fNDF requirement than primiparous cows when fed high-MP rations at the beginning of lactation.

Nutrient partitioning in fresh cow nutrition

In another article published in the May 2021 issue of the Journal of Dairy Science, researchers evaluated whether the nutritional strategies examined affected mobilization of body protein or fat reserves, body composition, or nutrient partitioning during early lactation. Using empty body composition, several interactions between dietary treatment and parity were observed.

Overall, feeding fresh cows a diet rich in metabolizable protein (MP) with a balanced amino acid (AA) profile increases dry matter intake and reduces tissue mobilization.

Overall, feeding fresh cows a diet rich in MP with a balanced AA profile increased dry matter intake and reduced tissue mobilization. However, the additional energy derived from increased intake was partitioned differently depending on parity.

Interestingly, when forage NDF was reduced while maintaining high MP, tissue mobilization tended to increase. Again, differences between primiparous and multiparous cows were observed: primiparous cows mobilized more body fat, whereas multiparous cows mobilized more body protein.

Overall, results indicate that parity, amino acid profile, and the concentration of forage NDF fed to fresh cows can influence both short- and long-term nutrient partitioning between body tissues and milk production.

In primiparous cows fed a mixed diet (soybean meal, rapeseed meal, corn gluten meal, and protected amino acids) or a mixed diet with lower forage NDF, metabolizable protein intake ranged from 1,800 to 1,850 g/day. In multiparous cows fed the mixed diet, MP intake reached approximately 2,500 g/day.

These findings are highly valuable and allow fresh cow diets to be adjusted to provide the nutrients required to maximize productive performance.

Energytech

Energytech is a blend of energy feeds with different digestive dynamics, supported by specific supplementation to enhance their utilization by the animal.

• Flaxseed: provides lipids of high nutritional interest, not only for energy value but also for omega-3 fatty acid content.
• Fractionated palmitic acid: supplies fat without interfering with fiber digestibility and supports milk fat content.
• Toasted full-fat soybean: provides bypass protein and rumen-available oil.
• Carob: rich in sugars, supporting optimal ruminal microflora activity.
• Dextrose: an essential element in the energy metabolism cycle.
• Vitamin E: a key ally against lipid oxidation.
• B-group vitamins, choline, niacinamide, and methionine: support hepatic energy metabolism.
• Highly bioavailable trace elements: act as catalysts in energy utilization reactions.

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Bibliografy “Nutrizione vacche fresche”:

• Tebbe & Weiss, 2021a. J. Dairy Sci. 104:5583-5600
• Tebbe & Weiss, 2021b. J. Dairy Sci. 104:5601-5616