Using dried fly larvae as livestock feed studied

Using dried fly larvae as livestock feed studied

CORNELL animal scientists, entomologists and a business professor will examine the environmental impact and commercial potential of quickly processing dairy cow manure with fly larvae and then using the dried larvae as livestock feed.

For dairy farms, manure waste presents an ongoing disposal challenge, while at the same time, the common housefly is considered a public health problem.

With a 2013 grant from Cornell's David R. Atkinson Center for a Sustainable Future, the researchers hope to exploit the housefly's life cycle and hasten the decay process of manure — to make it into a usable fertilizer in as quickly as eight days. The residual larvae may then be dried and made into high-quality protein supplements for aquaculture and livestock.

"Manure is a natural substrate for fly larvae. We can decrease manure volume, control for nutritional content and decrease its potential for eutrophication (leached, heavy doses of nutrients in water bodies)," Vimal Selvaraj, Cornell assistant professor of animal science and the principal investigator on the grant, said.

Co-researchers are: Patricia Johnson, professor and chair of animal science; Jan Nyrop, professor of entomology and senior associate dean of the Cornell College of Agriculture & Life Sciences, and Mark Milstein, clinical professor of management at the Samuel Curtis Johnson Graduate School of Management and director of the school's Center for Sustainable Global Enterprise.

Nyrop will examine larval-growing density, Johnson will examine how the larval proteins affect the diets of broiler chickens and Milstein will explore the larvae meal's market potential and the costs of scaling up commercial operations.

Flies and manure have long coexisted. Female flies can ovulate up to 700 eggs during a life cycle, and the larvae thrive on decaying waste.

An army of flies can reduce a manure mass by half, concurrently lowering the nitrogen and phosphorus content of the manure. Meanwhile, the residual larvae can be harvested as a feed source high in protein and essential amino acids.

While the collected larvae will be dried and ground into meal to replace soybean meal or fish meal in animal feed, additional toxicological safety testing for heavy metals, residual drugs and antibiotics will be examined, the researchers added.

 

Fecal microbiomes

An understanding of the bovine fecal microbiome could contribute to solving issues regarding animal production, cattle health and food safety, according to M. Kim, L. Kuehn, J. Bono, E. Berry, N. Kalchayanand, H. Freetly and J. Wells of the U.S. Department of Agriculture's U.S. Meat Animal Research Center and J. Kim and A. Benson of the University of Nebraska-Lincoln. They presented poster W21 at the recent joint annual meeting of the American Society of Animal Science and American Dairy Science Assn. in Indianapolis, Ind.

Kim et al. said their goal was to examine the influence of diet on the fecal microbiome in feedlot cattle by using next-generation pyrosequencing technology.

They investigated the fecal microbiomes of 426 cattle fed one of three diets: (1) a finishing diet that consisted of 83% dry-rolled corn, 13% corn silage and 4% supplement, (2) a late growing diet that consisted of 66% dry-rolled corn, 26% corn silage and 8% supplement and (3) an early growing diet that consisted of 70% corn silage and 30% alfalfa haylage.

Kim et al. obtained more than 2.1 million 16S rRNA gene sequences from 333 cattle with at least 2,000 sequence reads and that were classified into taxa using the RDP classifier.

Among the diet groups, Firmicutes was the first predominant phylum, accounting for more than 50% of total sequences in all three diet groups, the researchers reported, adding that Bacteroidetes was the second predominant phylum in the finishing and the late growing diet groups, while TM7 was the second predominant phylum in the early growing diet group.

The genera Fecalibacterium, Anaerovibrio, Prevotella, Parabacteroides and Pantoea were significantly more abundant (P < 0.0001) in the late growing diet group than in the other two groups, while the genera Oscillibacter, Turicibacter, Coprococcus, Clostridium, Blautia, Lactobacillus and Subdoligranulum were significantly more abundant (P < 0.0001) in the finishing diet group than the other groups, Kim et al. said. The abundance of the genera Sporacetigenium, Anaerovorax, Propionibacterium and Akkermansia was significantly higher (P < 0.0001) in the early growing diet than the other two diet groups.

Kim et al. concluded that diet has an effect on the fecal microbiome of cattle, particularly between cattle fed forage-rich and grain-rich diets.

Condensed tannins. C. Rivera, A. Plascencia and N. Torrentera of UABC in Mexico and R. Zinn of the University of California-Davis reported on two trials conducted to evaluate the effects of tannin source and level on feedlot cattle performance during the late finishing phase when metabolizable protein intake is not limiting requirements for growth (poster T16).

In trial 1, 96 calf-fed Holstein steers were used in a randomized complete block design experiment to evaluate the level of tannin supplementation, Rivera et al. said. Treatments consisted of a steam-flaked corn-based finishing diet supplemented with 0%, 0.2%, 0.4% and 0.6% condensed tannin (CT).

Across the 84-day feeding period, tannin supplementation increased average daily gain (ADG), gain efficiency and the ratio of observed net energy for maintenance (NEm) to expected NEm (Table 1), the researchers reported.

In trial 2, Rivera et al. used 96 calf-fed Holstein steers in a randomized complete block design experiment to compare the influence of tannin source (condensed or hydrolysable) on cattle performance during the late finishing phase.

They said dietary treatments consisted of a steam-flaked corn-based finishing diet supplemented with 0% tannin, 0.6% CT, 0.6% hydrolysable tannin (HT) or a mixture of 0.3% CT and 0.3% HT (dry matter basis).

Across the 84-day feeding period, tannin supplementation tended to increase ADG and DMI (Table 2), but there were no treatment effects on gain efficiency and observed:expected diet NEm, Rivera et al. reported.

They concluded that tannin supplementation may enhance feedlot cattle growth performance during the late finishing phase independently of effects on ruminal metabolism protein (the metabolizable protein supply from the basal non-supplemented diet was already in excess of requirements for growth).

Low-fat distillers grains. As the ethanol industry develops new manufacturing processes that alter the nutritional profile of the resulting co-products, researchers are continually evaluating the new products for inclusion in diets for livestock.

I. Ceconi, A. DiCostanzo and G.I. Crawford of the University of Minnesota and M. Ruiz-Moreno of the University of Florida reported in abstract 739 that, compared with conventional dried distillers grains (DDGs), the lower fat and higher protein content of low-fat DDGs (LF-DDG) may attenuate the negative effects of excessive dietary fat on the growth of fiber-digesting ruminal microbes.

Ceconi et al. explained that a further consequence of this effect is a decrease in organic matter total-tract digestibility (OMD), feed intake and overall performance of feedlot cattle.

Ceconi et al. conducted an experiment to evaluate the effect of LF-DDG inclusion in beef cattle finishing diets on OMD and ruminal fermentation.

Six ruminally cannulated Holstein steers were assigned randomly to a duplicated 3 x 3 Latin square design. Steers were fed ad libitum once daily one of three dietary treatments containing (on a dry matter basis): 84% dry-rolled corn, 10% ryegrass haylage and 6% supplement (control) or 53% dry-rolled corn, 10% ryegrass haylage and 2% supplement with either 35% traditional DDGs or 35% LF-DDG.

According to Ceconi et al., dietary CP levels were 12.1%, 15.9% and 19.9% and fat concentrations were 3.7%, 6.7% and 4.5% for the control, traditional DDG and LF-DDG diets, respectively.

Organic matter intake was greater (P < 0.01) for steers fed DDGs and LF-DDG than controls (Table 3), Ceconi et al. reported, but dietary treatment did not affect OMD (P = 0.12) or ruminal pH (P = 0.64).

The ruminal ammonia concentration was smaller and the ruminal volatile fatty acid (VFA) level was greater (P < 0.04) for the control and LF-DDG diets than the traditional DDG diet, the researchers said. Inclusion of LF-DDG resulted in a smaller ammonia-nitrogen concentration and increased ruminal VFA level compared with traditional DDG inclusion, Ceconi et al. noted.

They concluded that partial replacement of dry-rolled corn with LF-DDG led to no change in ruminal ammonia and VFA concentration, while replacement with conventional DDG led to an increased ammonia nitrogen concentration and decreased ruminal VFA level.

 

1. Effect of level of CT during late finishing period (trial 1)

 

-CT, %-

Std. error

 

0

0.2

0.4

0.6

of means

P-value

ADG, kg/day

1.37

1.42

1.48

1.50

0.04

0.05

Gain efficiency

0.122

0.128

0.128

0.129

0.002

0.04

Observed:expected NEm

0.92

0.95

0.94

0.95

0.01

0.06

 

2. Effect of tannin source during late finishing phase (trial 2)

 

-Tannin source-

Std.

 

None

0.6% CT

0.6% HT

0.3% CT/
0.3% HT

error of means

P-value

ADG, kg/day

1.53

1.64

1.61

1.65

0.06

0.08

DMI, kg/day

10.0

10.3

10.2

10.7

0.15

0.06

Gain efficiency

0.152

0.159

0.157

0.155

0.005

0.42

Observed:expected NEm

0.97

0.99

0.99

0.97

0.02

0.38

 

3. Effect of LF-DDG on rumen parameters

 

-Diet-

Control

DDG

LF-DDG

Organic matter intake, kg

8.09

8.26

8.31

OMD, %

69.7

69.0

72.8

Ruminal pH

5.78

5.73

5.66

Ruminal ammonia, mg/dL

2.74

2.69

3.75

Ruminal VFA, mM

92.8

92.4

74.6

 

Volume:85 Issue:32

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