Studies of method of conserving grass herbage and frequency of feeding in cattle. 2. Eating behaviour, rumen motility and rumen fill

Review of Livestock Welfare Indicators Relevant for the Australian Live Export Industry

Animal welfare is an important issue for the live export industry (LEI), in terms of economic returns, community attitudes and international socio-political relations. Mortality has traditionally been the main welfare measure recorded within the LEI; however, high mortality incidents are usually acted upon after adverse events occur, reducing the scope for proactive welfare enhancement. We reviewed 71 potential animal welfare measures, identifying those measures that would be appropriate for use throughout the LEI for feeder and slaughter livestock species, and categorised these as animal-, environment- and resource-based. We divided the live export supply chain into three sectors: (1) Australian facilities, (2) vessel and (3) destination country facilities. After reviewing the relevant regulations for each sector of the industry, we identified 38 (sector 1), 35 (sector 2) and 26 (sector 3) measures already being collected under current practice. These could be used to form a 'welfare information dashboard': a LEI-specific online interface for collecting data that could contribute towards standardised industry reporting. We identified another 20, 25 and 28 measures that are relevant to each LEI sector (sectors 1, 2, 3, respectively), and that could be developed and integrated into a benchmarking system in the future.

Diurnal patterns in rumen volume and composition of digesta flowing into the duodenum

Rate of passage of digesta out of the rumen is generally assumed to follow first order kinetics but this assumption may not hold within 24-h feeding cycles. Four lactating cows offered a mixed forage/concentrate diet ad libitum from 08.00 h to 00.00 h and a protein-rich meal at either 08.30 or 00.30 h were used to investigate diurnal patterns in rumen volume and composition of digesta flowing into the duodenum. Cows were fitted with large rumen cannulae to permit complete emptying of rumen digesta and T-piece duodenal cannulae with inserts to enable collection of representative samples of digesta. Chromium-mordanted lucerne hay manually dosed to the rumen at 2-h intervals and a continuous infusion of cobalt-EDTA were used as digesta flow markers. Duodenal digesta was sampled over three alternate days to obtain samples representing every hour of the 24-h day, which were analysed individually. Use of either of the two markers gave similar results for mean daily flow but not for hourly flow and thus hourly flow data were not considered reliable. The content of crude protein in duodenal digesta varied within one feeding cycle from 200 to 320 g/kg in cows offered protein at 08.30 (‘day’) and from 240 to 300 in cows offered protein at 00.30 h (‘night’). On a daily basis, fractional passage rates (calculated from duodenal flow divided by rumen pool size) were significantly (P = 0·016) lower for protein for ‘night’ (0·0750 per h) versus ‘day’ (0·0824 per h) cows. The observation that marked diurnal patterns in the composition of protein flowing into the duodenum can apparently be ‘smoothed’ simply by altering feeding sequence, which was correlated with an increased milk fat yield, suggests there is potential for improving production through manipulating the way in which dietary components are offered within a day.

Rate of passage of digesta out of the rumen is generally assumed to follow first order kinetics but this assumption may not hold within 24-h feeding cycles. Four lactating cows offered a mixed forage/concentrate diet ad libitum from 08.00 h to 00.00 h and a protein-rich meal at either 08.30 or 00.30 h were used to investigate diurnal patterns in rumen volume and composition of digesta flowing into the duodenum. Cows were fitted with large rumen cannulae to permit complete emptying of rumen digesta and T-piece duodenal cannulae with inserts to enable collection of representative samples of digesta. Chromium-mordanted lucerne hay manually dosed to the rumen at 2-h intervals and a continuous infusion of cobalt-EDTA were used as digesta flow markers. Duodenal digesta was sampled over three alternate days to obtain samples representing every hour of the 24-h day, which were analysed individually. Use of either of the two markers gave similar results for mean daily flow but not f or hourly flow and thus hourly flow data were not considered reliable. The content of crude protein in duodenal digesta varied within one feeding cycle from 200 to 320 glkg in cows offered protein at 08.30 day’) and from 240 to 300 in cows offered protein at 00.30 h (‘night’). On a daily basis, fractional passage rates (calculated from duodenal flow divided by rumen pool size) were significantly (? = 0·016) lower for protein for ‘night’ (0·0750 per h) versus ‘day’ (0·0824 per h) cows. The observation that marked diurnal patterns in the composition of protein flowing into the duodenum can apparently be ‘smoothed’ simply by altering feeding sequence, which was correlated with an increased milk fat yield, suggests there is potential for improving production through manipulating the way in which dietary components are offered within a day.

Relationship between dry matter, fibre and nitrogen degradation characteristics of silage and silage intake of steers

A study was carried out to examine the relationship between silage intake and rumen degradability characteristics of silage. The dry matter (DM), neutral-detergent fibre (NDF), acid-detergent fibre (ADF), hemicellulose and nitrogen (N) degradability characteristics of 136 silages were determined using polyester bags in three rumen fistulated beef cross steers. The bags were incubated for 0, 6, 12, 24, 48 and 72 h. Intakes of these silages, by steers, were reported by Steen et al., 1998. The relationships between silage DM intake (g/kg metabolic live weight) and DM, fibre and N degradability characteristics of the silages were poor (R2 < 0·32). Degradability characteristics of the silages were highly negatively correlated with fibre concentration of the silages (R < –0·82) and highly positively correlated with the soluble N minus ammonia concentration (R < 0·77). Some of the degradability characteristics were highly correlated with organic matter digestibility, particularly the proportion of DM, fibre and N degraded after 72 h (R = 0·75 to 0·85). In view of the poor relationship between silage intake and degradability, the results of this study question the rôle of degradation characteristics of DM, fibre and N in the rumen on silage intake.

Meal patterns of dairy cows consuming mixed foods with a high or a low ratio of concentrate to grass silage

With the aim of testing the effects of food quality on meal patterns 127 213 visits by 22 lactating cows to 12 computerized feeders supplying two foods, high forage (HF) and high concentrate (HC) consisting of grass silage and concentrate were analysed. The foods were composed of the same ingredients but the proportion of concentrate dry matter (DM) in the food DM differed between HC (0·59) and HF (0·27). Each of the foods was offered ad libitum to 11 cows from the start of lactation until 156 (s.e. 9) days after calving. Mean daily fresh food intake (49·2 kg) was not affected by treatment. Mean daily intake of DM differed between HC (23·6 kg) and HF (17·8 kg). After estimating individual meal criteria, visits were grouped into meals. The mean daily number of meals was 6·6, the mean fresh food intake per meal was 7·6 kg and neither was affected by treatment. Cows consuming HF had longer meals (41·4 v. 31·3 min) but a lower feeding rate than cows consuming HC (233 v. 337 g of fresh food per min and 78 v. 156 g DM per min). Pre- and post-prandial correlation coefficients were sometimes statistically significant but always low (R2from 0 to 0·05) and not affected by treatment. Food intake per hour of the feeding cycle (defined as the intake during a meal divided by length of the meal plus the duration of the preceding between-meal interval) showed a diurnal pattern in the shape of a sine-wave with low values of about 1·5 kg/h for cycles starting just after midnight and high values of more than 3·0 kg/h for cycles starting just after noon. Neither the mean, nor the amplitude, nor the shift of the sine-wave were affected by treatment. The data suggest that similar mechanisms are responsible for the short-term intake regulation of HC and HF. No evidence was found to suggest that the diurnal meal pattern of cows consuming HF deviated from that of cows consuming HC as a result of differences between foods in constraints related to their physical properties.

A comparison of five methods that estimate meal criteria for cattle

In data collected for feeding behaviour analysis, feeding events are generally separated by many very short to very long intervals during which no feeding occurs. When feeding is clustered in bouts, a meal criterion (that is the longest non-feeding interval accepted as part of a meal) must be estimated before events can be grouped into meals. Until recently, three methods that estimate quantitative meal criteria were available. These methods consist of fitting a ‘broken-stick’ (two straight intersecting lines, both with a negative slope) to the frequency distribution (method 1), the loge-transformed cumulative frequency distribution (the log-survivorship curve; method 2) or the loge-transformed frequency distribution (method 3) of intervals between events. Recently, new methods have been proposed that fit either two (method 4) or three (method 5) Gaussians to the frequency distribution of loge-transformed interval length (log-normal models). We compare the estimates obtained with these five methods when applied to a data set of 79575 intervals between visits to food dispensers. These were recorded with 16 lactating cows during an average period of 156·6 (s.d. 51·5) days per cow. Meal criteria were estimated as 1·9, 6·0, 7·5, 32·4 and 49·1 min by methods 1 to 5, respectively. Estimated daily number of meals ranged from 5·7 to 12·1 per cow and estimated average meal size from 4·0 to 8·4 kg. The observed probabilities of cows initiating feeding in relation to time since feeding last showed best agreement with the predictions of the log-normal models. We conclude that the first three methods do not, while log-normal models do, have an adequate biological basis for a clear interpretation of the estimated meal criteria. Log-normal models are, therefore, the most promising for estimating meal criteria in cattle and probably in other species as well.

The effect of silage fermentation characteristics on dry-matter intake of steers

Juke was expressed from two silages of contrasting fermentation type with either high (H) or low (L) levels of lactic acid and reconstituted either with the silage from which it had been expressed or the other silage. This procedure produced four dietary treatments (HH, HL, LL, LH) each differing in fermentation characteristics. The dietary treatments HH, HL, LL, and LH contained 81, 71, 59, and 49 g lactic acid per kg dry matter (DM) and 101, 133, 193 and 159 g ammonia-N per kg total nitrogen (TN) respectively. The four diets were offered to four steers (mean live weight 679 (s.e. 49) kg) in a four-period change-over design experiment. Each period was of 17 days duration. DM intakes were recorded daily, with intakes on days 8 to 17 used in the statistical analysis of data. On day 12 of each experimental period, rumen fluid samples were taken throughout a 24-h period. The rates of disappearance of DM, nitrogen (N), modified acid-detergent fibre (MADF) and neutral-detergent fibre (NDF) in the rumen were determined on days 14 to 17 using the polyester bag technique. DM intakes were 7·2, 6·9, 6·0 and 6·0 (s.e. 0·50) kg/day (P = 0·08) for HH, HL, LL and LH dietary treatments respectively. Diet had no significant effect on eating behaviour, rumen fermentation parameters or degradability of DM, N, MADF and NDF fractions (P > 0·05). Silage L increased rumen fluid pH (P < 0·05), reduced buffering capacity (P < 0·05) and increased the molar proportion of propionic acid and n-butyric acid (P < 0·05 and P < 0·01) compared with silage H. Silage L also had a lower DM apparent digestibility, D-value and DM, (P < 0·001), N and MADF (P < 0·05) degradabilities than silage H. The higher DM intake of dietary treatment HH compared with dietary treatments LL and LH could not be explained by any single constituent of the silages although it was apparent that physical characteristics of the silage were more important in determining intake than the chemical characteristics.

Effects of feeding ratio of beet pulp to alfalfa hay or grass hay on ruminal mat characteristics and chewing activity in Holstein dry cows

The influence of the feeding ratio of a non-forage fiber source and hay on ruminal mat characteristics and chewing activity was evaluated in dairy dry cows. Cows were fed four different diets: the ratios of alfalfa hay (AH) to beet pulp (BP) were 8:2 (dry matter basis, A8B2) and 2:8 (A2B8), and those of grass hay (GH) to BP were 8:2 (G8B2) and 2:8 (G2B8). Total eating time was decreased with increasing BP content (P < 0.01). Total rumination time for AH was shorter than that for GH (P < 0.01), and it decreased with increasing BP content (P < 0.01). The ruminal mat was detected by using a penetration resistance test of the rumen digesta. Penetration resistance value (PRV) of ruminal mat was highest with the G8B2 diet and PRV decreased with increasing BP content (P < 0.05) and feeding AH (P < 0.05). Thickness of the ruminal mat was greater for increasing BP content (P < 0.05). Simple linear regression of ruminal mat PRV on total rumination time resulted in a high positive correlation (r = 0.744; P < 0.001; n = 16). The results demonstrated that increasing the PRV of the ruminal mat stimulated rumination activity and a ruminal mat could be formed, although it was soft even when cows were offered a large quantity of BP.

The effect of protein degradation products in grass silages on feed intake and intake behaviour in sheep

The effects of NH3 and amines on grass-silage intake, intake behaviour and rumen characteristics were studied in sheep. From a single sward, two direct-cut grass silages were prepared, either untreated (WAS) or with 4·51 formic acid/tonne (FAS). Four experimental diets: WAS, FAS, FAS with addition of 2·9 g NH3/kg DM (FAS + N) and FAS with 2·8 g amines/kg DM (FAS + A), were offered ad lib. once daily to four rumen-cannulated wethers in a 4 × 4 Latin square design. Daily DM intake (DMI) tended to be influenced by dietary treatment (P = 0·09). Compared with FAS, DMI was lower for WAS. Addition of NH3 did not alter DMI, whereas amine addition slightly lowered daily DMI. Reduced DMI resulted from lower intake rates during both the principal meal and the subsequent small meals. Lower initial intake rate during the principal meal suggested reduced palatability of WAS and FAS + A. Amines and NH3, however, did not influence chewing efficiency. No treatment effects were observed on total rumen pool size, DM and neutral-detergent fibre content. Furthermore, NH3, and amines did not alter rumen pH, NH3, and volatile fatty acid concentrations to the extent that they could act on chemostatic intake regulation. Amine addition, however, lowered osmolality of the rumen liquid. No treatment effects on rumen motility were observed. In conclusion, daily DMI was not reduced by the addition of NH3, suggesting that NH3per se is not the causal factor in the negative correlations between silage NH3 content and intake observed by other authors. Amines, however, tended to reduce DMI only by their effect at the oro-pharyngeal level of intake control.

Flow paths of plant tissue residues and digesta through gastrointestinal segments in Spanish goats and methodological considerations1

A sequence of eight twice-daily meals, each marked with different rare earth elements, was fed to 24 Spanish goats (BW = 20.6 +/- 1.94 kg) to produce meal-based profiles of rare earth markers within segments of the gastrointestinal digesta on subsequent slaughter. Accumulative mean residence time and time delay of rare earths and segmental and accumulative mean residence times of indigestible NDF (IDF) were estimated for each sampled segment. Diets consisted of ad libitum access to bermudagrass hay with a limit feeding of one of four supplements: 1) minerals (basal, B); 2) B + energy (E); 3) B + CP (CP); or 4) B + E + CP for 84 d. Mean daily intake (g/kg of BW) during the 5 d before slaughter differed (P < 0.05) via diet for DM but not for IDF (8.0 +/- 0.35 g/kg of BW). Larger estimates of cumulative mean residence time for IDF vs. rare earths were suggested to be the consequence of a meal-induced bias in the single measurement of IDF pool size by anatomical site. The rare earth compartment method was considered more reliable than the IDF pool dilution method because it yielded flow estimates based on the flux of eight meal-dosed rare earth markers over 4 d and was independent of anatomical definitions of pool size. Statistically indistinguishable estimates for gastrointestinal mean residence times for IDF and rare earths conform to assumed indelibility for the specifically applied rare earths and indigestibility of IDF. The potentially digestible NDF (PDF):IDF ratio of dietary fragments (0.8) progressively decreased in the following order: caudodorsal reticulorumen (0.390) > crainodorsal reticulorumen (0.357) approximately reticulum (0.354) > mid-dorsal reticulorumen (0.291) approximately ventral reticulorumen (0.286), to that within the omasal folds and in the abomasum (0.259). Such a gradient of progressively aging mixture of plant tissue fragments is consistent with age-dependent flow paths established in the reticulorumen and flowing to the omasum and abomasum. Such heterogeneity of fragment ages within the reticulorumen is also indicated by the superior fit of marker dose site double dagger marker sampling site model assumptions. Additionally, cyclic meal- and rumination-induced variations in escape rate occur. Estimates of mean escape rates over days, needed for the practice of ruminant nutrition, must consider the complex interactions among plant tissues and the dynamics of their ruminal digestion of PDF.

Influence of maturity of grass silage and flaked corn starch on the production and metabolism of volatile fatty acids in dairy cows

An experiment employing a Latin square design was used to quantify the effects of two stages of maturity of grass silage (early cut and late cut) and three concentrations of flaked corn starch (0, 2, and 4 kg) on the molar proportion of rumen volatile fatty acids (VFA), the production of rumen VFA, and the net fluxes of VFA in the splanchnic tissue of cows. The molar proportions of VFA in rumen fluid were similar for cows fed both silages. When the silage diets were supplemented with starch, the proportion of propionic acid increased for cows fed diets containing early cut grass silage, but no effects were found for cows fed diets containing late cut grass silage. Estimated gastrointestinal production of acetate, propionate, butyrate, and branched-chain fatty acids plus valerate was related to intake of metabolizable energy and organic matter fermented into VFA. The portal release of acetate was approximately 14% lower than the estimated production of acetate by cows fed diets containing early cut grass silage, but cows fed diets containing late cut grass silage showed a variable difference between estimated production and portal release (31, 24, and 15%, respectively) as starch supplementation increased. The portal release of butyrate plus beta-hydroxybutyrate and the release of branched-chain fatty acids plus valerate were approximately 70 and 25%, respectively, of the estimated gastrointestinal production. Propionate production was similar to the portal release of propionate. Net flux measurements in splanchnic tissue in combination with gastrointestinal digestion and kinetics provide information that increases the knowledge of pathways and metabolism and quantifies the availability of individual nutrients for milk production in dairy cows.

Studies of method of conserving grass herbage and frequency of feeding in cattle. 1. Voluntary feed intake, digestion and rate of passage

The effect of method of conserving grass herbage and the frequency of feeding on digestion in and passage from the rumen was studied in growing cattle. A single sward of perennial ryegrass (Lolium perenne cv. Endura) was cut on 1 d and conserved as silage or hay. These forages were offered as the only feed to twelve rumen-cannulated Friesian steers (average initial live weight (LW) 128 kg) either at a restricted level of intake (20 g dry matter (DM)/kg LW; Expt 1) or ad lib. (Expt 2). In Expt 1 the forages were offered either once or eight times daily. When fed once or eight times daily, in vivo digestibility of DM was very similar for hay and silage (0.771 and 0.783 respectively), while the fractional rate of digestion measured by incubation in Dacron bags was significantly (P less than 0.05) higher for silage (0.069) than hay (0.057). The rate of passage of mordanted feed out of the rumen was significantly (P less than 0.01) faster for silage when determined from concentrations of marker in the rumen (0.034 v. 0.028/h). The volume of liquid in the rumen was lower (P less than 0.01) for animals consuming silage (27.51) compared with hay (37.11), while the fractional rate of passage of liquid from the rumen was higher (0.141 v. 0.098/h, P less than 0.05). The volume of liquid in the rumen was also lower (P less than 0.05) in steers offered feed eight times daily (29.5 l), compared with once daily (35.1 l), but frequency of feeding had no significant effect either on total digestibility or on rate of digestion in the rumen. The ad lib. intake of silage was significantly (P less than 0.01) lower than that of hay (4.53 v. 5.16 kg DM/d) in Expt 2.