Unit Of Digestible Organic Matter Intake Research Articles

Effect of forage particle size and feeding frequency on fermentation patterns and sites and extent of digestion in dairy cows fed mixed diets

This trial aimed at studying the effects and possible interactions between forage particle size and feeding frequency on the site and extent of digestion and ruminal fermentations throughout the day in dairy cows fed mixed diets. Two forage particle sizes (chopped, C, or ground and pelleted, G, dehydrated alfalfa) and two feeding frequencies (two (2) or six (6) times daily) were combined in a 2×2! arrangement. Four mid-lactation cows with cannulae in the rumen and proximal duodenum were used in a 4×4 Latin square design. They were fed at 95% of ad-libitum intake with three hours access to the manger after each meal distribution. On a dry-matter (DM) basis, the four diets consisted of 40% dehydrated whole-crop maize, 4% long perennial ryegrass hay, 25% dehydrated alfalfa and 31% concentrate (69% wheat). Dry-matter intake averaged 22.2 kg day −1. No interaction between forage particle size and feeding frequency was found. Feeding G rather than C diets reduced chewing time (22.4 vs. 26.2 min kg −1 DM), total and ruminal digestibilities of organic matter (OM) and cell-wall constituents ( p<0.10), and increased the non-ammonia nitrogen flow into the duodenum per unit of digestible OM intake ( p<0.05). Feeding G diets also reduced the molar proportion of acetic acid and increased the molar proportions of propionic and valeric acids. These changes in ruminal digestion were associated with a lower fibrolytic activity and modifications in ruminal environment. The daily means of pH and ammonia concentration were decreased, while the range of pH during the day and the time when pH and ammonia concentration were low (<6.0 and 2.9 mmol l −1, respectively) were increased. At the same time, the proportion of fluid in the reticular contents and the fractional outflow rate of liquids and small particles were decreased. Increasing feeding frequency did not affect carbohydrate digestion and mean ruminal parameters, although post-feeding variations of pH, osmolality and ammonia concentration were much less pronounced. It is concluded that reduced forage particle size can sharply affect the quantity and the nature of digestive end-products by altering chemical and physical conditions in the rumen. However, the magnitude of this effect is not dependent on the amount of fermentable OM entering the rumen in one meal.

The effect of starch supplementation of straw on microbial protein supply in sheep

The effect on microbial N (MN) supply of supplementation of straw with a mixture of maize starch and ground barley was examined. Urinary excretion of purine derivatives (PD) was used as an index of microbial protein supply. Six wether sheep of 42–48 kg with rumen cannulae were offered ad libitum either barley straw with 5% molasses, or barley straw with 15.5 or 31.0% of a mixture of maize starch and ground barley (1.2:1.0), and 9 and 13% molasses respectively. All sheep received all three diets for periods of 21 days, excreta being collected during the last 7 days. Digestible organic matter intake (DOMI) increased with starch inclusion as 435, 750 and 1043 (SED 47) g day −1 for the three diets respectively. Total PD excretion was 7.0, 12.3 and 21.1 (SED 0.92) mmol day −1, and the estimated MN supply was 5.7, 10.5 and 18.2 (SED 0.84) g day −1. Expressed as per unit DOMI, MN supply was 12.8, 14.1 and 17.5 (SED 1.3) g N kg −1 DOMI. Rumen liquid and solid outflow rates (fraction of rumen volume h −1) were 0.047, 0.054 and 0.073 (SED 0.0074) and 0.078, 0.105 and 0.130 (SED 0.0083) respectively. MN supply per unit DOMI increased probably due to a greater rumen outflow rate. The practical implication is that with low quality straw, supplementation of starch concentrate up to 31% of the whole diet increased both voluntary food intake and the supply of microbial protein per unit of DOMI.

Feed intake and digestion responses in sheep to the addition of inorganic sulfur to a herbage diet of low sulfur content

Young sheep were used in feed intake and digestion studies with a wheaten straw diet of low sulfur (S) content (0.71 g S kg-1 organic matter) fed without additional S (low S diet) or containing sodium sulfate (high S diet). With the high S diet, relative to the low S diet, (i) the levels of sulfide in rumen liquor were elevated, (ii) less time was spent in ruminating activities, (iii) rumen liquor volume tended to be lower (-l0%), (iv) indigestible markers were cleared more rapidly from the rumen (approx. +16%), (v) more organic matter (OM) and acid detergent fibre were digested in the stomach and in the alimentary tract as a whole (+8-16%), (vi) more non-ammonia nitrogen (NAN) flowed into the intestines (+13%) and this NAN had a higher content of sulfur amino acids (+ 17%), (vii) a greater quantity of NAN was digested in the intestines per unit of digestible OM intake (+ 12%), (viii) the concentrations of various amino acids in venous blood were substantially lower, and (ix) fungal activity in the rumen was higher. The number of bites performed on each rumination bolus was inversely related to fungal activity in the rumen, but the latter was not related to OM digestibility or to the sulfur amino acid content of the NAN flowing into the intestines. The OM digestibility was inversely related to the rate of clearance of markers from the rumen with the low S diet but not the high S diet. Voluntary feed consumption was similar with both diets, and in the low S diet it was inversely related to OM digestibility and positively related to marker clearance rate from the rumen. Digestible OM intake under conditions of ad libitum feeding was higher with the high S diet (+11%) and positively related to fungal activity in the rumen and to the sulfur amino acid content of the NAN flowing into the intestines. The data indicate that an inadequate amount of S in the low S diet impaired the metabolism of the rumen microbiota which in turn affected variables relating to digestion and metabolism. A quantitatively significant role for the anaerobic fungi in the structural degradation of fibre is suggested and attention is drawn to the need for studies on both feed consumption regulation with low S diets and the relation between herbage S status and the sulfur amino acid content of the rumen microbiota.

Utilization of clover diets by sheep. 2. Intake, digestion and utilization of nitrogen and sulfur

Nine mature Merino wethers were fed three clover diets at 95% of previously measured intake under steady state conditions. The diets were mature subterranean clover (MSC), green subterranean clover (GSC) and persian clover (PC). The utilization of dietary N and S was studied for each feed.The ratios of digestible organic matter (DOM) to crude protein (CP) in the diets ranged from 3.9 to 5.5 : 1. The flow of microbial crude protein (MCP) from the abomasum was only 34 g day-1 in sheep given MSC compared to 77 g day-1 for GSC and 85 g day-1 for PC. However, the calculated efficiencies of MCP synthesis were 230-250 g MCP per kg OM apparently digested in the rumen for the three clovers. Despite the similar efficiencies of MCP synthesis, the ammonia-N (30 mg l-1) and sulfide-S (220 8g l-1) concentrations in the rumen of sheep fed MSC were low. The concentrations for the the other clovers were ammonia-N 90-110 mg l-1 and sulfide-S 730-1770 8g l-1. The amount of CP apparently digested in the intestines (DCPi) was only 31 g day-1 in sheep given MSC compared to 100 g day-1 and 81 g-1 in those fed GSC and PC, respectively. While this indicates that protein insufficiency in the tissues may have limited the intake of MSC, the DCPi values per unit of DOM intake were 150,210 and 150 g kg DOM-1 for MSC, GSC and PC, respectively. Sheep excreted more N and S (% of intake) in faeces when given MSC compared to GSC or PC.The sheep were in positive apparent balance for N and S when fed GSC or PC, but were mobilizing these nutrients from tissues at the low intakes of DOM, N and S with MSC. The wool growth rates and amounts of N and S incorporated into wool when MSC was fed were about half the other two feeds.These results are discussed in relation to other work on the utilization of N and S by sheep and likely effects of this on the intake of the feeds.

Studies on the growth and carcass composition in Daldale wether lambs. 2. The effect of dietary protein/energy ratio

Two experiments on the effect of dietary protein/energy ration on growth and carcass composition in Daldale wether lambs were carried out.In experiment 1, two groups of eight lambs in each group were fed in pens at a restricted intake (30 g air-dry feed per kg liveweight) either on a high protein/high energy diet (HP/HER) (20.7% crude protein) or on a low protein/high energy diet (LP/HER) (10.3% crude protein). The lambs were grown from 24.8 kg liveweight until slaughter at 37.5 kg. In experiment 2, two groups of eight lambs in each group were fed in pens a pelleted diet ad libitum, either on a high protein/high energy ration (HP/HEA) or on a low protein/high energy ratio (LP/HEA). The lambs were grown from 22.0 � 0.8 kg liveweight until slaughter at 37.5 kg. Those lambs on the HP/HE diets grew significantly faster than their counterparts on the LP/HE diets. Accordingly, animals given the HP/HE diets showed a superior feed conversion ratio than animals given the LP/HE diets. Despite these differences, there was no overall differences between treatments either at restricted or at ad libitum intake in the weight of carcass, the dressing percentage, and in the chemical composition of the carcass. In general, the carcasses produced contained a similar amount of fat (30.6%-32.9% of carcass). It was concluded that varying protein to energy ratio in diets affected liveweight gain and feed conversion ratio, but did not affect carcass composition.An experiment was conducted on the diets to investigate some aspects of digestion in the stomach and intestines at the two levels of crude protein.Dietary crude protein level had little effect upon the apparent digestibility of organic matter (OM) and neutral detergent fibre in the whole tract, the proportion of NDF digested in the stomach, the total volatile fatty acid concentration (VFA) in the rumen and the proportions of individual VFA.The flow of rates of digesta from the rumen and abomasum were also similar for the two diets. However, the proportion of the total digestion of OM occurring in the stomach decreased, while the flow of total N and crude protein (CP) (total N minus ammonia N x 6.25) to the intestines and the amounts of N and CP digested therein was higher on the HP diet.The data from the digestion experiment showed that the amount of digestible CP in the intestines per unit of digestible OM intake did not affect carcass composition.

The utilization of nitrogen and sulfur by weaner and mature merino sheep

The intake, excretion, and retention of nitrogen and sulfur were measured in weaner (liveweight 15-17 kg) and mature (40-45 kg) Merino sheep offered ad libitum amounts of three pasture hays. The hays (H, M and L) varied in their content of digestible organic matter (71, 59 and 45%), of nitrogen (2.84, 0.72 and 1.20%), and of sulfur (0.20, 0.13 and 0.09%). When given the most-digestible hay (H), the weaners retained more nitrogen than did the mature sheep (0.97 v. 0.81 g per l00g digestible organic matter intake (DOMI), but there was no difference in retention of sulfur (79 v. 74 mg per l00g DOMI)). However, on the basis of metabolic liveweight, the weaners incorporated more of both nutrients into tissues, while the mature wethers incorporated more nitrogen and sulfur into wool. The retention of nitrogen and of sulfur per unit of DOMI were similar for each age group of sheep when the medium quality hay (M) was given. Mature sheep again incorporated more of each nutrient into wool. With the poorest quality hay (L), the weaners excreted more nitrogen and sulfur as a proportion of the amounts consumed than did the mature sheep. This resulted in a lower retention of nitrogen (-1.45 v. -0.74 g per l00g DOMI) and sulfur (-77 v. -14 mg per l00g DOMI) by the weaners. There was a lower incorporation of nitrogen into tissues per unit of metabolic liveweight by the weaners, and the mature sheep incorporated more nitrogen and sulfur into wool. The weaners grew wool less efficiently (g per l00g DOMI) than the adult sheep on all diets, the difference being greatest when the poorest quality hay was given. These results are discussed in relation to the nature of tissue energy reserves in weaner sheep.

Digestion of a ground and pelleted diet in the stomach and intestines of young sheep from two breeds

Some aspects of digestion were studied in small groups of fistulated wether lambs from two breeds, Dorset Horn and Corriedale. The Iambs were given a ground and pelleted diet of equal parts hay and concentrates once daily at two levels of intake. At the same liveweight (25 kg), the higher intake was associated with reduced digestion of organic matter (OM) and fibre in the whole gastro-intestinal tract; rumen mean retention times were also reduced, as was the proportion of OM digestion which occurred in the rumen. An increase in the amount of protein entering the intestines appeared to be composed of both undegraded dietary protein and microbial protein. Despite a reduction in the digestibility of non-ammonia nitrogen in the intestines, more crude protein was digested there per unit of digestible OM intake (25.9 v..23.6%; P &lt; 0.05). Differences between the breed groups were smaller than those associated with level of feeding. Nevertheless, particularly at lower relative intakes, rumen mean retention times were longer, rumen digesta content was greater, and rumen OM and fibre digestion tended to be greater in the Dorset Horn lambs; crude protein digestion in the intestines per unit of digestible OM intake also tended to be less at the low intakes. More than three-quarters of the cellulose digestion but less than half the hemicellulose digestion occurred in the rumen. The proportion of the urea synthesized that was degraded in the gastrointestinal tract (0.24-0.30) was consistently lower in these lambs than has been reported for adult sheep.