Bird type, forage options play role in organic hen production

Genotype, diet protein level and forage material influence egg production for organically raised layer hens. 

A team of Danish researchers examined the effect of diets with differing protein contents and forages in the performance of New Hampshire (NH) and Lohmann Silver (LS) hens raised with organic production methods.

Forage nutritional levels should be considered in establishing hen diets for organic production, they said.

“Protein and amino acid content and high intake of foraging material influence production parameters in both genotypes, where LS performed more efficiently than NH,” ​said researchers. “The hens obtain most likely some nutrients from the high intake of maize silage plus carrots and alfalfa silage, however, the foraging material have diluted the total intake of nutrients to some extent, which possibly influenced the results obtained on the overall production parameters.”​

Why organic production​

The production of organic eggs is increasing in several European countries, with Denmark having the largest market share at 20.4% in 2013, said researchers. However, use of a 100% organic diet in the EU has been delayed until 2018, in favor of allowing 5% non-organic ingredients to continue being used, they said.

There are some concerns regarding whether a completely organic diet can contain sufficient amounts of essential amino acids, they said, as diets lacking nutrients can reduce egg production or stress birds. To compensate, some producers feed extra protein, which results in higher nitrogen and ammonia concentratins.

Additionally, in organic production, local growth of feed ingredients and protein sources is preferred, said researchers. An increased amount of soybeans or crops like quinoa would boost forms of locally grown protein.

“The overall objective of the study was to examine different strategies for a more sustainable production of organic eggs, which supports the overall welfare of the hens,” ​said researchers. “Specific objectives were to include two hen genotypes with different nutrient requirements given experimental diets with decreasing levels of protein and amino acids and with access to different kinds of foraging material.”​

“The intake of the experimental diets and forage material, egg production, egg quality, use of outdoor area, plumage condition and mortality were the response parameters considered,”​ they added.

Experiment details​

For the experiment, 1200 hens were fed one of three experimental diets from 18 to 41 weeks of age, said researchers. The birds also had access to either maize silage and carrots or alfalfa silage.

The three diets A, B and C contained different protein amounts and amino acid levels, but similar energy amounts, they said. The diets and forages were continually available and no additional amino acids were given.

Diet A was based on a standard organic layer feed and included wheat, barley, oats, maize, soybeans, calcium carbonate and fishmeal, they said. The other diets were based on feed ingredients grown organically in Denmark, like soybeans and quinoa; other ingredients included wheat, barley, oats, peas, fishmeal and calcium carbonate.

The amounts eaten were recorded in four-week increments and eggs were collected every three days, said researchers. Feed conversion ratio (FCR) was determined using diet and eggs laid.

Body weights were taken prior to the start of the experiment and at the end of the experiment, they said. Plumage condition scores were noted every two weeks.

The balance and digestibility were checked at the end of the study, they said. Mortality also was recorded.

Results found​

“The production parameters were significantly affected by genotype, diet and foraging material,” ​said researchers. “The NH genotype had an average laying rate of 70%, compared to 85% for LS. The FCR was also most efficient with LS hens fed diet A.”​

LS hens also had higher egg weights and masses, they said. The best results were for LS hens getting any of the diets with the alfalfa forage or the A diet and carrots and silage forage.

The decreased laying rate for the B and C diets may be an indication that essential amino acids were lacking, said researchers.

“There was no effect of the three diets A, B and C on laying rate for LS having access to alfalfa silage obtaining an average of 88.9%,” ​they said. “The laying rate for NH was lower when given diet C and alfalfa silage compared to NH hens on diet A and B, which means a different response compared to LS hens, as a significant interaction was seen between genotypes and forage material.”​

However, when both types of birds were given the carrot and silage forage, results were more consistent with the A diet producing more eggs than either B or C, they said.

Both groups of birds preferred the maize silage with carrots to the alfalfa silage, they said. Birds ate about 104g a day of the maize compared to about 57g a day for the alfalfa. However, silage intake may have altered the amounts of nutrients received.

The NH hens had a higher feed intake per egg than LS hens did, they said. Both genotypes had higher FCR with diet C and there was no effect from the forage.

For both types of birds, the retention of nitrogen and phosphorus was low, said researchers. But the concentration of nitrogen in the manure was influenced by bird type, diet and forage. The NH had higher levels, as did birds getting the A diet and the alfalfa silage.

“The coefficient of total tract digestibility (CTTAD) of the different nutrients was affected differently, having only minor effect on CTTAD of starch, being high in all groups,” ​the scientists said. “The CTTAD of methionine and cysteine was higher with diet A, compared with B and C.”​

The NH birds digested the feed better with access to alfalfa forage, they said. But, the LS hens had similar reactions to both forage types. And, calcium retention was best for the LS hens and for diet A.

“The decreasing level of protein and methionine, cysteine and other important amino acids in diet B and C affected production results for both genotypes, especially for the groups having access to maize silage plus carrots as foraging material,”​ said researchers. “The large amount of foraging material eaten by the hens in all groups resulted in a high daily intake of especially insoluble NSP [non-starch polysaccharides] present in the silages (​∼87% of total NSP), which probably diluted the nutrient concentration, having the greatest effect with diet B and C, being lower in protein and in some essential amino acids.”​

Additionally, birds getting the C diet had the worst plumage scores for the different diets at the end of the trial, they said.

The research was funded by the Danish Research Center for Organic Food and Farming.