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Testing of Producer Cover Crop Cocktail Samples

Research Coordinator: Dr. Akim Omokanye

Location: Fairview Research Farm

From: Peace Country Beef & Forage Association 2020 Annual Report

Funded by the Canadian Agricultural Partnership - Government of Alberta

In the Peace Country, beef cattle producers are growing a lot of acres of diverse annual crop mixtures, commonly known as cocktails, for forage production. Four to six or more crops in a mixture may be considered as a practical application of ecological principles based on biodiversity, plant interactions, and other natural regulation mechanisms as well as improved soil carbon stocks. In general, cocktail mixtures could increase forage production, improve water and soil quality, increase nutrient cycling, and improve moisture conservation and crop productivity. A diverse annual crop mixture can be selected from different crop groups or plant families such as cereals or grasses, legumes, and brassicas. The different groups correspond to different plant functional groups. Each species in a mixture will likely mature at different times, providing available immature forage continuously through the growing season.

PCBFA has been testing several cocktails, including simple to complex ones, in small plots for many years now. In collaboration with PCBFA, producers have been able to come up with cocktail mixtures for specific needs including swath grazing and silage on their farms. Producers also grow commercial cocktails with and without modifying the crop compositions as shown on the product labels. The objective of this present study is to compare forage yield and quality of different cocktails that producers use for livestock feed in the Peace.

Methods

The study was carried out at Fairview Research Farm (RR #35), MD of Fairview.

The previous crop at this site was an alfalfa hay crop for several years until it was ploughed in the fall of 2018. The site was chemical fallowed in 2019, but tilled before seeding in 2020.

Soil analysis carried out in the fall of 2018 from 0-6” soil depth showed an organic matter content of 8.2%, a pH of 6.2, and an electrical conductivity of 0.21 ds/m. The soil had 10 lbs N/acre, 14 lbs P/acre, and 485 lbs K/acre, as well as 9 lbs S/acre.

Experimental Design: randomized complete block design in 3 replications.

This year, we seeded 14 different cocktails including samples from beef cattle producers and seed companies as shown in Table 1 below.

Seeding was done on May 29 with a Fabro plot drill equipped with disc-type openers on 9” row spacing.

Six rows that were 8 m long were sown per plot.

Seed was weighed and mixed in an envelope prior to seeding.

Mixed row seeding method was used for the mixtures.

Seeding depth was 0.75”.

Fertility was 60 lbs/acre of 11-52-0 to all legumes.

The cocktails were inoculated with granular inoculant at seeding.

Spraying: pre-emergent (StartUp glyphosate + LI surfactant).

We harvested the cocktails for forage dry matter (DM) yield on August 26th and forage samples were sent to A & L Laboratory, Ontario for forage quality determination.

Results and Implications

Forage Dry Matter Yield

Of all mixes tested, Mix 5 yielded the most at 14,242 lbs/ac, followed by Mix 7 at 13,750 lbs/ac. Mixes 13 & 14 were also mixtures of note in terms of dry matter yield. The poorest yielding mixture was Mix 9, which came in at about half of the yield of the top mixture in the trial. Overall, 9 of 14 mixtures produced dry matter yield that was more than 10,000 lbs/ac.

Forage Quality

Crude Protein (CP) and CP yield

Protein measurements varied significantly among the different mixtures. Eight out of the 14 mixtures came back with greater than 10% CP. Although Mix 9 had the lowest dry matter yield of all mixtures tested, it actually came back with the highest crude protein of all mixtures tested at a whopping 20.7%.

A beef cow’s crude protein requirements are as follows: mid gestation 7%, late gestation 9%, lactation (after calving) 11%. This is over and above the crude protein requirements of any class of beef animal at any stage of growth or gestation. All mixes tested with the exception of Mixes 3 & 14 had enough crude protein content to sustain a beef cow through to late gestation. Although Mix 14 was one of the highest yielding crops in terms of biomass, it only had a crude protein measurement of 8.7%. This could be due to the lower proportion of legumes in this mixture. Mix 14 along with 5 other mixtures (Mix 2, 3, 4, 5, 6) that had less than 10% CP generally had lower content in them only varying from 11-37% legumes in the mixtures. Mixtures with greater CP had more than 40% legumes at harvest. For cocktails, the commonly grown legumes in the Peace Country are forage peas, clovers (crimson and berseem), and hairy vetches. Including at least 40% of such legumes in cocktails would no doubt greatly improve forage CP for beef cattle.

Mix 7 produced the highest forage CP yield (2324 lbs CP/acre), which significantly differed from other mixes (except for Mix 8).


Energy

Protein is a building block. Energy gives the ability to use the building blocks for growth and other productive purposes. There are six measures for energy that are used in beef cattle production including the 3 net energy systems and total digestible nutrients (TDN). TDN is useful for beef cow rations that are primarily forage. The net energy system separates the energy requirements into their fractional components used for tissue maintenance (net energy for maintenance, NEM), tissue gain (net energy for gain, NEG), and lactation (net energy for lactation, NEL).

Using TDN to determine the amount of energy, the rule of thumb for beef cow energy requirements is 55-60-65. This implies that the mid-gestation requirement is 55% TDN, 60% TDN during mid-gestation, and 65% TDN after calving. All mixtures came in over the 60% mid-gestation TDN requirement. Mixtures 2, 7, 9, 10, and 11 all came in over the 65% TDN threshold, meaning that they would have sufficient energy for a cow with calf at side.

The NEL, NEG, and NEM respectively varied from 1.24-1.39, 0.60-0.77 and 1.32-1.49 Mcal/kg. Mix 6 had the least NEL, NEG, and NEM, while Mix 9 was consistently highest in all three. For growing and finishing calves, which require 1.08-2.29 MCal/kg, the NEM for the mixes were well within these recommended values by NASEM (2016). On the other hand, for mature beef cattle, all mixes were well above the required NEM of 0.97-1.10 MCal/kg for dry gestating beef cows and 1.19-1.28 MCal/kg for nursing beef cows.

Minerals

Ca levels in all mixes (0.80-1.53%) exceeded the recommended Ca levels for mature beef cattle (0.58% Ca).

P levels for all mixtures (0.17-0.32% P) were adequate for a dry gestating beef cow (0.16% P) but only mixes 7, 8, 9, and 11 had sufficient levels for a nursing beef cow.

K & Mg levels were all above recommended levels, but not to the point of toxicity.

The forage Na levels in all mixes were lower than the recommended amount for beef cattle.


Conclusion

In terms of protein and energy requirements of beef cows, all mixtures (with the exception of Mixes 3 & 14) would suffice for cattle leading up to calving time. Mixes 7, 9, and 10 would comfortably meet and exceed nutritional requirements during lactation with a calf at side. Cattle should maintain body condition on these feeds. It is worth noting however that Mixes 9 & 10 did have the lowest dry matter yield, with some of the best nutritional content. Mix 7 had significantly more yield than mixes 9 & 10, and is a suitable feedstuff for all classes of beef cattle.

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