Novel microbial diversity adherent to plant biomass in the herbivore gastrointestinal tract, as revealed by ribosomal intergenic spacer analysis and rrs gene sequencing.

It is well recognized that a dynamic biofilm develops upon plant biomass in the herbivore gastrointestinal tract, but this component of the microbiome has not previously been specifically sampled, or directly compared with the biodiversity present in the planktonic fraction of digesta. In this study, the digesta collected from four sheep fed two different diets was separated into three fractions: the planktonic phase, and the microbial populations either weakly or tightly adherent to plant biomass. The community DNA prepared from each fraction was then subjected to both ribosomal intergenic spacer analysis (RISA) and denaturing gradient gel electrophoresis (DGGE). Both types of analysis showed that dietary factors influence community structure, and that the adherent fractions produced more complex profiles. The RIS-clone libraries prepared from the planktonic and adherent populations were then subjected to restriction fragment length polymorphism (RFLP) and DNA sequence analyses, which resulted in a far greater degree of discrimination among the fractions. Although many of the sequenced clones from the adherent populations were assigned to various clusters within the low G+C Gram-positive bacteria, the clone libraries from animals consuming an all-grass diet were largely comprised of novel lineages of Clostridium, while in animals consuming the starch-containing diet, Selenomonas and Ruminococcus spp. were the dominant low G+C Gram-positive bacteria. Additionally, the libraries from hay-fed animals also contained clones most similar to asaccharolytic Clostridia, and other Gram-positive bacteria that specialize in the transformation of plant phenolic compounds and the formation of cinnamic, phenylacetic and phenylpropionic acids. These results reveal, for the first time, the phylogeny of adherent subpopulations that specialize in the transformation of plant lignins and other secondary compounds, which potentiate polysaccharide hydrolysis by other members of the biofilm.

Rate of carcass components gain, carcass characteristics, and muscle longissimus tenderness in lambs fed dietary protein sources with a low quality roughage diet.

An experiment was conducted to examine the effects of infrequently fed (twice/week) protein supplements on rate of carcass components gain, carcass traits and tenderness of meat in lambs. Forty-three Dorset Horn×Merino wether lambs (aged 4 months) were assigned by stratified randomization (live weight basis) to five dietary treatments to compare the results with lambs fed very low quality (5.1 MJME/day) roughage diet. Lambs on control diet (BAS; treatment 1) and all other dietary treatment groups were offered ad libitum amounts of a mixed roughage diet (oat hay:lucerne hay) at the ratio of 85:15 throughout the 10-week experimental study. Supplements of barley grain with added urea and sulphate (USB, 226 g DM/day; treatment 2); lupins (LUP, 231 g DM/day; treatment 3); cottonseed meal (CSM, 152 g DM/day; treatment 4); fish meal (FM, 97 g DM/day; treatment 5) were offered at isonitrogenous amounts. Final live weight (FLW) and empty body weight (EBW) were greater (P<0.01) with FM, LUP, USB and CSM when compared with BAS. Rates of gain of carcass components observed during the experimental period resulted in lower carcass fatness (P<0.05) and greater muscle content (P<0.01) with FM; and higher (P<0.05) level of fat and muscle in the carcass with LUP compared to those on BAS diet. Other diets (USB and CSM) had less marked effects, but higher rate of daily fat gain in the carcass with LUP and CSM was indicated by greater carcass fat depth (P<0.05; the total tissue depth of muscle and fat at the twelfth rib, 110 mm from the midline; GR) and content of intramuscular fat (P<0.05), respectively. Energy gained as fat in the carcass was lowest with FM (P<0.05), highest with BAS and intermediate with all other treatments. The increase in carcass leanness and reduction in fatness with FM and USB compared to BAS and other treatments affected neither (P>0.1) meat tenderness (Warner-Bratzler shear force) nor sarcomere length of longissimus thoracis muscle. Feeding small amounts of protein supplements to lambs on very low quality forage diets during dry seasons may be a viable path to improve the carcass weight and leanness in lambs without changing the meat tenderness.

Hypophyseal-portal somatostatin (SRIH) and jugular venous growth hormone secretion in the conscious unrestrained ewe.

Somatostatin (SRIH) release into hypophyseal portal blood varies reciprocally with growth hormone (GH) pulse generation in the male rat. However, few studies have directly evaluated this relationship in the female of any species. To address this issue, we carried out intensive (5 min) and extended (240 min) simultaneous monitoring of hypophyseal portal SRIH and internal jugular GH secretion in 7 unanesthetized ewes. Bihormonal synchrony was assessed by three statistically independent but complementary analyses: (i) cross-approximate entropy (X-ApEn) analysis to appraise the conditional regularity of SRIH/GH release patterns; (ii) cross-correlation analysis of paired sample SRIH and GH release rates, and (iii) probability analysis of random versus nonrandom SRIH and GH discrete pulse concordance. From a one-variable perspective, ApEn analysis documented consistently more irregular patterns of SRIH than GH release (94 +/- 4.3 and 72 +/- 8.1%, respectively, of the mean irregularity of 1,000 individual random-shuffled cognate series, p = 0.034). From a two-variable perspective, X-ApEn analysis revealed a nearly mean random relationship between SRIH and GH release patterns (group mean +/- SEM, 94 +/- 4.5% of the mean asynchrony of 1,000 randomly shuffled SRIH/GH pairs). Cross-correlation analysis disclosed highly variable linkages between SRIH and GH secretion; viz, negative cross-correlations in 5 sheep, positive relationships in 4, and both positive and negative SRIH/GH associations in 2 animals, wherein changes in SRIH secretion either preceded or followed those of GH. Peak detection by model-free cluster analysis quantified a total of 28 SRIH and 31 GH release episodes. Corresponding interpulse intervals (min) were comparable (37 +/- 4 (SRIH) and 43 +/- 12 (GH)), but the mean fractional (%) amplitude of SRIH peaks was 3.5-fold lower (60 +/- 10%) than that for GH (225 +/- 50%) (p = 0.024). Pulse-concordance probability testing showed that discrete peaks of SRIH and GH secretion coincided only 33% of the time, although this value exceeded chance expectation (p < 10(-4)). In summary, the present analysis applies intensive (5 min) and extended (240 min) simultaneous sampling of hypophyseal-portal and jugular venous blood to quantitate the degree of coordinate SRIH and GH secretion in the unanesthetized ovariectomized ewe. Thereby, we unmask highly irregular SRIH release patterns, and nearly random SRIH and GH associations. We conclude that, to the extent that in vivo sampling reflects physiological SRIH/somatotrope activity, the female sheep maintains complex time-varying interactions between SRIH and GH release.

Dietary manipulation of muscle long-chain omega-3 and omega-6 fatty acids and sensory properties of lamb meat.

The effects of dietary manipulation of muscle long-chain omega-3 fatty acids (FA) on sensory properties of cooked meat in second cross ([Merino×Border Leicester]×Poll Dorset) wether lambs were evaluated. Lambs fed dietary supplements of fish meal (FM, Exp. 1) and fish oil (FO, Exp. 2) showed moderately (P<0.01) and markedly (P<0.001) increased muscle long-chain omega-3 FA content compared with those fed the basal diet of lucerne chaff and oat chaff. Protected canola seed (PCS, Exp. 1) significantly (P<0.001) increased omega-6 FA content of the longissimus muscle. In each of the 2 experiments (1 and 2), after being fed experimental diets for 6 weeks lambs were slaughtered at a commercial abattoir. At 24 h post-mortem (PM) the semitendinosus and biceps femoris muscles were removed from animals and stored at -20°C until evaluation of sensory properties using experienced panel members. The muscle samples were stored for 3 (Exp. 1) and 12 (Exp. 2) months then removed, thawed and cooked for sensory evaluation. The meat samples were cooked under standardized conditions in a convection microwave at 180°C (20-25 min) to an internal temperature of 75°C. Cooked samples were tested for flavour, aroma, juiciness and overall palatability. The significant increase in muscle long-chain omega-3 with FM (Exp. 1 and 2) and FO (Exp. 2) or omega-6 FA with PCS (Exp. 1) were not detrimental to sensory panel evaluations of flavour or aroma of cooked meat when compared with the basal diet. However, meat from FM (Exp. 1) had lower juiciness and FO (Exp. 2) had lower overall palatability. Protected sunflower meal protein with FO (Exp. 2) significantly lowered ratings for flavour, juiciness and overall palatability. Lamb meat with increased levels of long-chain omega-3 FA can be produced without altering the sensory quality (flavour or aroma) of the cooked meat.