Potential Degradability Of Dry Matter Research Articles

Degradabilidade in situ da matéria seca, proteína bruta e fibra em detergente neutro do capim-furachão (Panicum repens, L.) submetido à adubação e em diferentes idades de corte

O objetivo deste estudo foi avaliar as degradabilidades potencial e efetiva da matéria seca (MS), proteína bruta (PB) e fibra em detergente neutro (FDN) do capim-furachão (Panicum repens, L.) em diferentes idades de corte (15, 30, 45, 60 e 75 dias) sob presença ou ausência de adubação. As taxas de passagem das fases líquida e sólida da digesta foram também avaliadas. Cinco bovinos machos, 7/8 Holandês/Zebu, entre 30 e 36 meses de idade, com média de 545 kg PV foram distribuídos em delineamento em quadrado latino em esquema de subparcelas. As parcelas foram as cinco idades de corte; as subparcelas, os dois níveis de adubação; e as subsubparcelas, os seis tempos de incubação. Idade de corte, adubação, tempo de incubação e interações entre idade e adubação e entre tempo de incubação e adubação influenciaram a degradabilidade ruminal da MS, PB e FDN. A degradabilidade potencial da MS aumentou com o tempo de incubação. A adubação melhorou e as idades de corte reduziram a degradabilidade efetiva da MS, PB e FDN. As taxas de degradação da matéria seca variaram de 0,0481 a 0,0299h-1.

Different means of administering polyethylene glycol to sheep: effect on the nutritive value of Acacia cyanophylla Lindl. foliage

AbstractPolyethylene glycol-4000 (PEG) was used to inactivate tannins in Acacia cyanophylla Lindl foliage. In the first of two experiments, four groups of five Barbarine sheep were held in metabolism crates so that intakes, apparent digestibilities, nitrogen balances and urinary excretion of allantoin could be measured. The second experiment involved four groups of three male Queue Fine de l'Ouest sheep fitted with rumen cannulae and housed in individual pens to measure rumen fermentation parameters and dry matter in situ degradation of A. cyanophylla foliage. All animals received fresh A. cyanophylla foliage ad libitum and 330 g concentrate on a daily basis. In each experiment, three groups of sheep received 20 g PEG daily, either mixed with concentrate (PEG-concentrate), dissolved in drinking water (PEG-water) or sprayed as a solution on A. cyanophylla foliage at the point of feeding (PEG-treatment). The fourth group was not supplied with PEG (control). Dry-matter intake of A. cyanophylla was low (28·3 g/kg metabolic live weight (M0·75) per day) and increased in sheep given the PEG-concentrate diet (38·2 g/kg M0·75 per day). PEG-concentrate and PEG-water diets resulted in an improvement in protein utilization as indicated by an increase of crude protein apparent digestibility (2·1 and 1·9 fold, respectively), nitrogen retention (3·2 fold with both dietary treatments) and urinary excretion of allantoin (1·9 and 1·5 fold, respectively). Improvements obtained with PEG-treatment diet were low and in general not significant (P > 0·05). Low neutral-detergent fibre and acid-detergent fibre apparent digestibility coefficients of diets led to the conclusion that conventional detergent extraction techniques are questionable in determining the in vivo digestibility of cell wall constituents for tannin-rich forages. Results from rumen fluid analyses indicated that sheep given PEG-containing diets had higher ammonia-nitrogen and volatile fatty acid (VFA) concentrations (P < 0·05). These results, coupled with the increase of allantoin excretion gave clear evidence that the efficiency of microbial synthesis was improved with PEG addition. The absence of change in ruminal pH and molar proportions of individual VF A suggested similar fermentation patterns among all dietary treatments. PEG supply increased the slowly degradable fraction of A. cyanophylla foliage incubated in the rumen (P < 0·05), thus dry matter potential degradability (a + b) was highest in sheep given PEG-containing diets. It is concluded that the affinity of acacia tannins to PEG, increased the availability of degradable proteins, which resulted in an improvement of the nutritive value of acacia foliage. However, for practical situations, adding PEG to concentrate or to drinking water is recommended for sheep browsing A. cyanophylla trees in the field or fed indoors.

The nutritional value of Piliostigma thonninghii (Mutukutu, Monkey bread) pods as a feed supplement for communal cattle in Zimbabwe

Piliostigma thonninghii pod samples obtained from two different communal areas of Zimbabwe (Kadoma and Gutu) throughout the 1993 dry season revealed that once mature there was no marked decline in the quality of the pod over the dry season. Chemical analyses on the P. thonninghii pod meal (PTPM) showed that it contained 919 dry matter (DM) per kg, 78.4 crude protein (CP), 230 crude fibre (CF), 446 neutral detergent fibre (NDF), 32.3 ether extract (EE), 47.9 crude ash (all expressed in g/kg DM) and 21.4 MJ gross energy (GE)/kg DM. Hence PTPM was found to be low in nitrogen but high in NDF. The in vivo DM, CP and NDF degradability patterns of PTPM and crushed maize meal (CMM; 21.3 MJ GE/kg) were assessed in four Holstein–Friesian steers (450 ± 20 kg) using the nylon bag technique. The effective degradability ( k = 0.05/h) for PTPM (33.4% DM, 29.8% CP and 18.9% NDF) were lower than those of CMM (46.1% DM, 40.8% CP and 27.7% NDF). PTPM had a much lower potential DM degradability than CMM, and will therefore, have lower nutritive value. However, PTPM could be a useful feed supplement to communal cattle grazing poor quality forage during the tropical dry season.

Degradability of forage protein supplements and their effects on the kinetics of digestion and passage

Degradability characteristics of oats hay (harvested at milk stage), oats straw, wheat middlings and forage legumes (lablab ( Lablab purpureus) hay, leaves of sesbania ( Sesbania sesban) and tagasaste ( Chamaecytisus palmensis) were evaluated in three sheep given native hay supplemented with cottonseed cake. In Trial 2, 18 fistulated male sheep were given six dietary treatments: ad libitum oats straw with 250 g (as fed) of lablab hay; ad libitum oats hay alone or supplemented with either 250 g (as fed) of lablab hay, wheat middlings (WM), sesbania or tagasaste. The effect of these diets on degradabilities of oats hay and oats straw and rumen particulate passage rate ( k1) were determined. Oats hay had higher ( P < 0.05) solubility, potential dry matter (DM) degradability and soluble nitrogen (N) (631 vs. 498 g per kg; p < 0.01) than oats straw. Oats hay DM degraded 2.3 times faster than oats straw when both were supplemented with lablab. Sheep given hay-lablab diet had a faster k1 (0.0371 vs. 0.0173 h −1; P < 0.01) and consumed more roughage (606 vs. 447 g per day; P < 0.01) than those given strawlablab diet. Sesbania had the highest potential DM degradability (921 g per kg) followed by WM (846), tagasaste (762) and lablab (706). WM (DM) degraded fastest followed in order by sesbania, lablab and tagasaste. Lablab had the highest soluble N (737 g per kg) and differed ( p < 0.001) from sesbania (298), WM (526) and tagasaste, which was negative (−38). Sesbania had the highest potential N degradability (922), followed by lablab (866), WM (849) and tagasaste (737). Supplements had similar ( P > 0.05) N degradation rates. Supplementation and type of supplement had no effect on any of the degradation characteristics of oats hay. Sheep given WM had the fastest k1 followed in order by lablab, sesbania and tagasaste. Supplementation increased the intakes of DM ( P < 0.01) and N ( P < 0.05) but not of neutral detergent fibre (NDF); but supplement types had no effect ( P > 0.05) on the intake of oats hay, total DM or NDF. It was concluded that supplementation with forage legumes had no effect on oats hay DM degradation rate but tended to enhance k1. Forage legumes that disappear fast from the rumen may induce lower substitution rates.

The effect of method of forage conservation and harvest season on the rumen degradation of forages harvested from permanent mountain meadows

AbstractAn irrigated permanent mountain meadow (Leon, Spain) was cut twice in 1987, in late June, and again in early September after the summer regrowth. Herbage harvested from each season was preserved by different methods, namely freezing (fresh), ensiling in plastic bags (silage) and sun-curing (hay). Rumen degradation characteristics were determined by the nylon bag technique. Forages harvested in September had a higher crude protein (CP) concentration (153 v. 104 g/kg dry matter (DM)) and a lower cell wall concentration (467 v. 599 g/kg DM) than those from the June cut, resulting in a greater DM potential degradability (0·856 v. 0·751) and a faster degradation rate (0·088 v. 0·057 per h). Method of conservation did not affect the CP concentration of the forages, but had a significant effect on their nitrogen (N) solubility and protein degradability. Hay had the lowest N solubility (0·388) and CP degradability. Ensiling led to an increase in the N solubility (0·668 v. 0·554) compared with the fresh control, resulting in a higher effective degradability of CP estimated for different rates of passage. Forage conservation caused a slight increase in the relative proportion of the cell wall in the total DM (mean neutral-detergent fibre concentrations for fresh forage, hay and silage were 510, 548 and 536 g/kg DM, respectively) presumably due to loss of cell contents. Potential DM degradabilities of fresh forage, hay and silage were similar (0·805, 0·813 and 0·791 respectively). Although hay seemed to be degraded to a greater extent and at a faster rate than the other two types of forages, the rumen degradation characteristics were not consistently affected by the method of conservation to an extent that could have important nutritional implications.