Replacing Soybean Meal with Hemp Leaves with Very Low THC Content in the Diet for Dairy Cows: Impact on Digestibility, Nitrogen Use Efficiency and Energy Metabolism

TL;DR

This study shows that hemp leaves with low THC can replace soybean meal in dairy cow diets without harming health or digestion, though improper adaptation may reduce feed intake and milk production.

Contribution

Demonstrates the viability of low-THC hemp leaves as a soybean meal alternative in dairy cow nutrition.

Findings

Hemp leaves had no negative effects on animal health or apparent digestibility.

Inadequate adaptation to the hemp diet reduced feed intake and milk yield.

Hemp feeding tended to lower methane yield and urinary nitrogen excretion.

Abstract

We studied the suitability of industrial hemp leaves with very low tetrahydrocannabinol content as an alternative protein source for dairy cow nutrition, relative to soybean meal, on performance traits, apparent digestibility, and animal health and behavior. Our findings show that dried Santhica 27 hemp leaves can be a suitable protein source for dairy cows, as animal health and apparent digestibility of the diet are not negatively affected; however, inadequate adaptation to the diet can result in a decreased feed intake and milk yield.

The aim was to investigate the suitability of Santhica 27 industrial hemp leaves as a protein source in dairy cow nutrition. Twelve Holstein dairy cows received a total mixed ration (TMR) containing 7.4% industrial hemp leaves (HEMP) and a TMR containing 3.5% soya extraction meal (CON) in a crossover design. Cows were kept in a free-stall barn for 2 weeks to measure feed intake, milk yield and sample plasma, ruminal fluid, and urine. In week 3, cows were housed in a respiration chamber to measure gas exchange, urine, and feces excretions. In the first two weeks, cows of the HEMP group rested longer but spent less time ruminating. Feeding the HEMP diet reduced dry matter intake (DMI), milk yield, and urinary N-metabolite concentrations and tended to lower total N-excretion, milk fat, and lactose concentrations. During the stay in the respiration chamber, DMI, milk yield, apparent digestibility, and crude protein degradability were similar between groups, but feeding the HEMP diet tended to reduce methane yield. In conclusion, Santhica 27 hemp leaves are a suitable protein source for dairy cows as they have no negative effects on animal health, apparent digestibility, and crude protein degradability. Nevertheless, inadequate adaptation to the diet reduces feed intake and milk yield.

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