Mikrolevä lypsylehmien valkuaisrehuna : vaikutus syöntiin, aineenvaihduntaan ja maidontuotantoon

Mikrolevät ovat potentiaalinen kotieläinten valkuaisrehu, sillä ne sisältävät yleensä paljon raakavalkuaista ja ravitsemuksellisesti hyviä rasvahappoja. Mikrolevät kasvavat nopeasti, tarvitsevat vain vähän ravinteita ja niitä voidaan kasvattaa alueilla, jotka ovat sopimattomia muuhun viljelyyn. Tämän tutkimuksen tavoitteena oli selvittää, voidaanko mikrolevällä korvata lypsylehmien valkuaisrehuna käytettävää rypsiä. Tutkimuksessa tarkasteltiin, miten rypsin korvaaminen osittain tai kokonaan mikrolevällä vaikuttaa lehmien kuiva-aineen syöntiin, ravintoaineiden sulavuuteen, plasman aminohappopitoisuuksiin ja aineenvaihduntatuotteisiin, maitorauhasen aineenvaihduntaan sekä maitotuotokseen ja maidon koostumukseen. Hypoteesina oli, että mikrolevä maittaa heikommin kuin rypsi, ja sen vuoksi lehmien kuiva-aineen syönti jää vähäisemmäksi mikroleväruokinnoissa. Toinen hypoteesi oli, että mikrolevä sisältää vähemmän histidiiniä kuin rypsi, ja sen vuoksi maito- ja valkuaistuotos jäävät mikroleväruokinnoissa pienemmiksi kuin käytettäessä valkuaisrehuna rypsiä. Tutkimus toteutettiin Viikin opetus- ja tutkimustilan navetassa. Kokeessa oli mukana kuusi ayrshirelehmää. Koemalli oli toistettu 3 x 3 latinalainen neliö. Koejakson pituus oli 3 viikkoa. Kontrollikäsittelynä oli rypsiruokinta (2,3 kg ilmakuivana). Kaksi muuta koekäsittelyä olivat ruokinta, jossa mikrolevä (Spirulina platensis ja Chlorella vulgaris 1:1 seos) korvasi puolet rypsin valkuaisesta ja ruokinta, jossa mikrolevä korvasi rypsin valkuaisen kokonaan. Kaikissa koekäsittelyissä lehmät saivat lisäksi viljaleikettä siten, että väkirehun osuus oli vakio (11 kg/pv) sekä vapaasti nurmisäilörehua. Rypsin korvaaminen osittain tai kokonaan mikrolevällä ei vaikuttanut lehmien kuiva-aineen syöntiin tai ravintoaineiden sulavuuteen. Mikroleväruokinnoissa histidiinin saanti oli pienempää kuin rypsiruokinnassa. Pienempi histidiinin saanti näkyi plasman histidiinipitoisuuden suoraviivaisena vähenemisenä (56,5 – 50,5 µmol/l) mikrolevän korvatessa rypsiä, mutta ei vaikuttanut maitotuotokseen tai maidon valkuais- tai rasvatuotoksiin. Koekäsittelyt eivät vaikuttaneet plasman aineenvaihduntatuotteisiin tai maitorauhasen aineenvaihduntaan. Lehmien plasman histidiinipitoisuus oli suuri kaikissa ruokinnoissa, mikä saattoi vaikuttaa siihen, että dieetistä saatavan histidiinin määrän väheneminen ei näkynyt maito- ja valkuaistuotoksissa. Lisäksi kokeen lehmät olivat myöhäisessä laktaatiokauden vaiheessa, mikä saattoi tasoittaa eroja koekäsittelyiden välillä. Valkuaisrehujen erilainen rasvahappokoostumus heijastui maitorasvan rasvahappokoostumukseen, mutta muutokset olivat määrällisesti pieniä. Tämän tutkimuksen tulosten perusteella mikrolevää voidaan käyttää lypsylehmien valkuaisrehuna. Mikrolevällä voitiin laktaatiokauden lopulla korvata rypsi joko kokonaan tai osittain ilman, että lypsylehmien kuiva-aineen syönti, maitotuotos, maitovalkuaisen tai -rasvan tuotos vähenivät.Micro algae are potential protein supplement for farm animals as micro algae are often rich in protein and contain nutritionally beneficial fatty acids. Micro algae grow rapidly and with low nutrient requirements, and can be cultivated in areas that are not suitable for cultivation of other food or feed. The aim of this study was to investigate whether micro algae can be used as an alternative protein supplement for rapeseed meal for dairy cows. We investigated how partial or total replacement of rapeseed meal with micro algae affects levels of dry matter intake, plasma concentrations of amino acids and metabolites, mammary gland metabolism, milk yield, and milk composition in dairy cows. Our hypothesis was that micro algae is less palatable than rapeseed meal, and therefore dry matter intake is lower in micro algae diets. Our second hypothesis was that micro algae contain less histidine than rapeseed meal, and therefore the milk and protein yields are lower in micro algae diets. The study was conducted at the research farm of University of Helsinki. Six multiparous Finnish Ayrshire cows participated in this experiment. The study design was a replicated 3 x 3 Latin square with 3-week periods. In the control diet, the protein supplement was rapeseed meal (2,3 kg air dry). The two other treatments were a diet where micro algae (Spirulina platensis and Chlorella vulgaris 1:1 mixture) replaced half of the rapeseed meal protein, and a diet where micro algae replaced all of the protein of rapeseed meal. In all diets, the cows were offered cereal-based concentrates, so that total concentrate portion was 11 kg /d and grass silage ad libitum. Replacing rapeseed meal partly or completely with micro algae had no effect on dry matter intake or digestibility of nutrients. In the micro algae diets, histidine intake was lower than in the control rapeseed diet. Lower histidine intake decreased the plasma histidine concentration linearly (56,5 – 50,5 µmol/l) but had no effect on milk, protein, or fat yields. Micro algae treatment had no effect on plasma metabolites or mammary gland metabolism. Plasma histidine concentration was high in all treatments, which may explain why the milk and protein yields did not decrease with micro algae diets. In addition, the cows were in late lactation, which may have attenuated the differences between treatments. The differences in fatty acid compositions between rapeseed and micro algae were reflected in the milk fatty acid compositions. However, the differences in milk fatty acid compositions were very small. This study suggests that micro algae can be used as a protein source for dairy cows. Micro algae can replace rapeseed meal partly or completely for dairy cows in late lactation without adverse effects in dry matter intake, or milk, protein, or fat yields

Ileal and total tract digestibility and nitrogen utilisation in blue fox (Vulpes lagopus) fed low-protein diets supplemented with DL-methionine and L-histidine

To formulate low-protein diets for blue foxes with sufficient amounts of amino acids (AA), AA digestibility and AA requirements of the animals are crucial information. Therefore, a digestibility and nitrogen (N) balance trial was conducted with 20 blue foxes to determine the macronutrient and AA digestibility and N utilisation in low-protein diets supplemented with DL-methionine (Met) and L-histidine (His). In addition, plasma urea and plasma AA were measured. The diets were designated as P24 (control), P20, P20M, P16M and P16MH and contained energy from digestible crude protein (DCP) at 24%, 20% or 16% of total dietary metabolisable energy (ME). The 20% protein level was fed with or without Met and the 16% protein level was fed with Met and with or without His. The apparent total-tract digestibility (ATTD) of crude protein linearly decreased with decreasing dietary protein level. The ATTD of dry matter, organic matter and crude carbohydrates increased when wheat starch was added as a replacement for protein. The apparent ileal digestibility (AID) and ATTD methods were compared to determine the AA digestibility. The decreasing dietary protein supply decreased the ATTD of most of the AA: threonine, tryptophan (Trp), valine, alanine (Ala), aspartic acid (Asp), glutamic acid, glycine (Gly), proline (Pro), serine (Ser) and total AA. The AID of the AA was constant between diets. Diverging AA showed higher or lower digestibility when determined in the AID or ATTD methods. Isoleucine, lysine, Met, Ala and tyrosine showed higher levels of AID. Arginine, His, cysteine (Cys), Trp, Asp, Gly, Pro and Ser showed higher levels of ATTD, which may reflect the net loss of these AA in the large intestine. Met and His supplementation improved the ATTD and AID of the AA in question, respectively, but did not affect the other variables examined. N retention did not differ between diets and renal N excretion decreased with decreasing protein level; thus N utilisation improved. It was concluded that the protein supply and AA composition in low-protein diets with supplemented Met were adequate for adult blue foxes, since the lower protein supply improved N utilisation and did not affect N retention. However, His supplementation failed to reach the designed level and therefore showed no clear results.Peer reviewe

Effects of feed energy and protein level on growth and pelt parameters in blue foxes (Vulpes lagopus) in the late growing-furring period

The aim of the present study was to determine whether a decrease in feed energy content would prevent extreme body weight (BW) gain and fatness in blue foxes in the late growing-furring period, without compromising pelt quality or pelt size. BW gain, body mass index (BMI), body condition score (BCS), and pelt characteristics were studied in 60 blue foxes divided into four equal-sized groups from mid-October until pelting (50 days). Experimental diets in were “high energy – high protein”, “high energy – low protein”, “low energy – high protein”, and “low energy – low protein”. High-energy diets contained 19.3 MJ metabolisable energy (ME) in kg dry matter (DM) and high-protein diets contained digestible crude protein (DCP) 20% of ME. Low-energy diets contained 16.3 MJ ME in kg DM and low-protein diets DCP 17% of ME. Feeding was gradually increased towards ad libitum. Reduced ME intake had no effect on pelt size or pelt quality. High-energy feeds resulted in heavier animals with higher BMI. However, the final BW exceeded 20 kg and BCS was “fat” or “extremely fat” in all groups.Peer reviewe

Performance in blue fox (Vulpes lagopus) fed low-protein diets supplemented with DL-methionine and L-histidine

The effects of low-protein diets supplemented with DL-methionine (MET) and L-histidine (HIS) on growth, pelt size and pelt quality were studied in two performance trials conducted at the Kannus Research Farm Luova Ltd, Finland. Both trials were conducted with 200 blue foxes, caged male-female pairs, initial age on average 20 weeks (trial 1) and 25 weeks (trial 2). In trial 1, diets contained digestible crude protein (DCP) 24%, 20% and 16% of metabolisable energy (ME). In trial 2, diets contained DCP 20%, 16.5% and 13% of ME. In both trials, the middle protein level was fed with or without MET and the lowest protein level was fed with MET and with or without HIS. In trial 1, blue foxes showed the greatest average daily gain (ADG) in the highest protein diet. Pelt size and pelt quality were not affected. In trial 2, blue foxes showed the greatest ADG in the low-protein groups. Pelt size and pelt quality were not affected.Peer reviewe