Voluntary Intake Of Roughages Research Articles

Digestibility and voluntary intake of roughages by wild boar and Meishan pigs

AbstractThe digestibility and voluntary intake of fibrous roughages and acorns was studied in six wild boar and five Meishan pigs. The neutral-detergent fibre (NDF) concentration of the diets ranged from 139 to 767 g/kg of the organic matter. Organic matter digestibility of acorns, mixed grass and wheat straw was higher in wild boar (P < 0·05) while voluntary food intake of the Meishan pigs was higher for mixed grass, hay and wheat straw (P < 0·05). Organic matter digestibility (P < 0·01) and NDF digestibility (P < 0·05) were both negatively related to NDF concentration of the diet. No relationship existed between voluntary food intake and NDF concentration of the diet. The apparent nitrogen (N) digestibility was positively related (P < 0·01) to dietary N while no relationship was found with dietary NDF. The negative effect of NDF on digestibility could only be partly explained by the lignin concentration of NDF. Much more important was the lower efficiency of the carbohydrate fermentation in the caecum and colon when compared with the direct absorption of glucose from the small intestine. It was estimated that digestible NDF at a maximum contributed proportionately 0·26 to the metabolizable energy intake of the animals. It was concluded that wild boar and domestic pigs should be able to maintain themselves on an all fresh grass diet when NDF concentration of the diet does not exceed about 550 g/kg and N concentration is not too low.

In sacco degradation characteristics as predictors of digestibility and voluntary intake of roughages by mature ewes

The in situ nylon bag technique was evaluated as a method of predicting digestibility and voluntary intake of roughages. Twelve feedstuffs including five untreated cereal straws, two cereal straws treated with urea and five grass hays were each offered to six–eight mature non-pregnant and non-lactating ewes (70.4±8.4 kg), ad libitum, over a period of eight weeks. Soyabean meal was given as supplement in variable amounts to cover rumen microbes requirements for degradable nitrogen. Two rumen fistulated rams were used to measure the digestibility of each diet and the kinetics of dry matter (DM) degradation in the rumen of the roughages. Apparent organic matter digestibility (OMD) of the roughages ranged from 0.441 to 0.600 g kg −1 and DM intake from 9.6 to 17.9 g kg −1 of live weight. DM degradation after 96 or 72 h incubation were the best predictors of roughages OMD ( r 2=0.73 and 0.70, respectively) while prediction of DM intake was most accurate from 3 h DM degradation and ADF content of roughages ( r 2=0.68 and 0.67, respectively). In contrast, digestible DM intake was best predicted by a multiple regression equation including the degradation constants soluble fraction and rate of degradation accounting for 89% of the variation observed. Live weight variation of ewes was also well predicted from a similar equation or from soluble fraction alone ( r 2=0.80) but the predictive capability of ADF was higher ( r 2=0.86) for this purpose.

Calcium Soaps of Olive Fatty Acids in the Diets of Manchega Dairy Ewes: Effects on Digestibility and Production

Two experiments were carried out with dairy ewes to determine the effects of supplementation of calcium soaps of olive fatty acids at 10% of the basal diet on digestibility, roughage intake, milk production and composition, and response to early induced ovulation. The addition of calcium soaps of olive fatty acids to the diets of dairy ewes significantly decreased the digestibility of dietary dry matter but not the digestibility of other components. The digestibility of crude fat was enhanced. Voluntary intake of roughage, with fixed concentrate allowances, was slightly, but not significantly, reduced for ewes fed the supplemented diet. After weaning at 35 d postpartum and during the next 5-wk period of twice daily milking, ewes fed the supplemented diet produced more total solids in milk than did ewes fed the basal diet. Ewes fed the supplemented diet also tended to produce more milk, protein, and milk energy and tended to have greater milk fat percentages. The composition of milk fatty acids was changed by the calcium soaps of olive fatty acids. Fewer short- and medium-chain fatty acids (C6:0, C8:0, C10:0, C12:0, C14:0, and C16:0), less C18:2, and more C18:1 and C18:0 were obtained in the milk of ewes fed the supplemented diet. Responses to ovulation induced at 60 d after lambing, while ewes were still lactating, were significantly higher for ewes fed the diet supplemented with calcium soaps of olive fatty acids than for ewes fed the basal diet. The calcium soaps of olive fatty acids appeared to be a useful source of energy for dairy ewes, and dairy ewes may be a good model for the study of the effects of nutrition during early lactation on reproductive performance of dairy ruminants.

Effect of Rumen Fill on Voluntary Intake by Steers

Rumen capacity can constrain the voluntary intake of roughages. Few published experiments have combined manipulation of rumen digesta volumes with measurements of intake, eating behaviour, and rumen volume and outflow. All these measurements were made in the experiment reported here.Three Holstein steers (680-750kg) with large rumen canulae were used. They were given hay ad libitum (degradation characteristics a = 35.2, b = 45.6, c = 0.0397 when degradation (P) in ‘t’ hours is given by P = a + b(l-e-ct). The hay was ‘chopped’ to lengths of about 40-60mm and supplemented with urea, sodium sulphate, minerals & vitamins. There were seven periods of five days. Periods 1, 3, 5 & 7 were controls, and periods 2, 4 & 6 treatment (3x3 latin square). As treatments the reticulo-rumen was totally emptied once daily, and the digesta weighed, sampled, and A) 1.15 (add), B) 0.75 (remove), or C) 1.00 (replace) returned to the rumen (digesta from B was used to add to A). Daily DM intake and excretion, feeding behaviour, and digesta flow (pulse dose of PEG on the last day of all seven periods) measured. Digesta was manipulated at 11.30h, the process taking less than an hour. Treatment effects were analysed as differences from the means of the controls proceeding and succeeding the appropriate treatment. These differences (‘change’ or ‘Δ’ values) were analysed as 3 x 3 latin squares, with period and animal effects included in the residual variance.

Effect of intraruminal infusions of volatile fatty acids on the intake of a low-digestibility straw by sheep

The voluntary intake of roughage diets by ruminants is related to their degradation characteristics (Hovell et al., 1986). Furthermore, as forage quality is improved the outflow of undegraded particles is increased. Previous studies have shown that differences between forages in outflow from the rumen were mainly associated with the outflow of liquid from the rumen. In this context there could be chemical factors arising from the rapid fermentation of the more degradable forages that could stimulate salivary flow or movement of water across the rumen wall, increasing liquid outflow from the rumen, and thus washing undegraded residues from the rumen and enabling the animal to eat more. One possible signal is rumen volatile fatty acids (VFA) levels since YFA production and concentration are significantly greater with roughages that support greater intakes and rumen outflows. Intraruminal infusions of VFA have been shown to depress feed intake in ruminants (Baile & Forbes, 1974). However, most of the infusion studies have been conducted with animals fed diets containing concentrates or high-quality forages, and most of them examined short-term intake responses to intraruminal infusions of, probably, supraphysiological levels of VFA (Dejong, 1986). The aim of this experiment was to examine whether the voluntary intake of a low quality roughage by sheep could be affected by the infusion of VFA at different doses into the rumen.

Factors Affecting Digestibility and Voluntary Intake of Roughages in Ruminants

Factors Affecting Digestibility and Voluntary Intake of Roughages in Ruminants

The effect of changing the physical form of roughage on the performance of the early-weaned calf

ABSTRACTAn experiment was conducted using two batches of 40 purchased male Hereford × Friesian calves, reared conventionally with weaning after 5 weeks. Five diets were offered ad libitum for 9 weeks: a basic concentrate pellet A offered alone, or with additional chopped or long straw; a diet incorporating 35 g sodium bicarbonate per kg in the basic pellet; and a complete diet with the inclusion of 176g chopped straw (20 mm) per kg in the concentrate pellet.Concentrate intakes and live-weight gains tended to increase with voluntary intake of roughage and the inclusion of buffer in the diet; giving a complete diet, however, gave the best results, with total intake increased to 1 -6 of that for diet A and also significantly increased weight gains.Rumen acidity was decreased by roughage consumption or by buffer inclusion in the diet. Increasing roughage consumption tended to promote an increase in the molar proportions of acetic and butyric acids in the rumen liquor, and a decrease in the molar proportion of propionic acid.Results suggested that chopping the roughage into 20-mm lengths did not obviously alter the rumen-buffering characteristics of long roughage, provided that a greater quantity was included in chopped form.

The voluntary intake of roughages by pregnant and by lactating dairy cows

SUMMARY1. Effects of late pregnancy and early lactation on the voluntary intake of dried grass (Expt 1) and a poor quality seeds hay (Expt 2) by dairy cows are described. Each cow received a constant daily allocation of concentrates throughout late pregnancy. After calving half the cows received an 80% increase in concentrates, and the remainder continued to receive their pre-partum allowance.2. Mean daily intakes of dried grass were higher than those of poor quality seeds hay. Intake of dried grass in week 2 of lactation was significantly correlated with the live weight of the cows, but a non-significant correlation was observed when seeds hay was offered.3. During late pregnancy mean daily intakes of both roughages were approximately constant until the week immediately before par turition, when a significant decline occurred.4. After calving mean daily intakes of both roughages increased throughout the first six weeks of lactation by 20–30% of the intake at week 1 post partum.5. The 80% increase in daily concentrate allocation in early lactation caused a significant decline of 0·55 kg dried grass dry-matter intake per kg concentrate dry matter; the decline of 0·17 kg poor quality hay dry matter per kg concentrate dry matter was not significant.

The effect of concentrates on the voluntary intake of roughages by cows

SummarySeven changeover experiments were conducted to examine the effect of giving restricted amounts of concentrates on the voluntary intake of different roughages by non-lactating dairy cows. The addition of up to 6 kg concentrates daily to the diet of cows receiving roughage ad lib. caused little change in the intake of hay and a small increase in the intake of barley straw. Larger amounts of concentrates of 6 and 8 kg daily reduced hay intake by between 0·2 and 0·4 kg dry matter/kg concentrate dry matter given. When concentrates were given to the cows the rate of decline in intake of hay tended to be greatest with the hays of highest digestibility. The daily addition of up to 8 kg concentrates to the diet of cows offered silage ad lib. caused only small depressions in the intake of silage. The results are discussed in relation to recent work on this subject with cattle and sheep.

Nutritional status and intake regulation in sheep. V. Effects of intraruminal infusions of volatile fatty acids upon voluntary intake of roughage by sheep

Results of experiments with infusions of volatile fatty acids into the rumen reveal that the induced changes in voluntary intake of roughages are not immediate, and vary in extent between animals. Single infusions resulted in subsequent depressions of feed intake, these being only partly related to the amount of energy of the infused volatile fatty acids. When longer-term infusions were made, acetic acid in small quantities depressed feed intake more than did propionic, and propionic acid modified the effect of acetic when the two were given together. Also recorded is an observation that animals receiving a casein-supplemented roughage diet reduced their feed intake when casein was infused per duodenum over 14-day periods. Results are discussed in relation to an hypothesis of an indirect mechanism attempting to maintain or restore the original energy balance, but showing considerable delay or inertia and imprecision when observed on a day to day basis.

The Influence of Supplementary Feeding and Grazing Restriction on the Voluntary Intake of Roughages and Liveweight Gain by Beef Cattle

The Influence of Supplementary Feeding and Grazing Restriction on the Voluntary Intake of Roughages and Liveweight Gain by Beef Cattle

The voluntary intake of roughages by steers

1. Four roughages were given ad lib. to each of eight steers. The amount consumed and the apparent digestibility of the energy of each roughage were determined together with the weight gains of the steers.2. The mean voluntary intake of dry matter was related to the mean apparent digestibility of the energy of the roughages in the same quantitative way for the steers as had been noted with sheep. Mean weight gains were proportional to the mean number of calories of energy apparently digested.3. Significant differences between individuals occurred in their voluntary food intakes, and those animals which consumed most digested it least efficiently. The variation in intake from individual to individual expressed as a standard deviation was ±7·5% of the mean.4. The quantitative similarity of sheep and cattle as far as the relationship between their voluntary consumption of food of different apparent digestibility is concerned, is contrasted with their dissimilarity with respect to fasting metabolism. It is suggested that sheep are likely to prove more efficient convertors of the energy of roughages to body gain than are cattle.Further work is clearly necessary to explore the extent of these differences.