Comparative digestibility of feedstuffs by sheep and cows

In vivo digestibility of a range of silages in cattle compared with sheep

Context Ensuring accuracy of feed testing is becoming increasingly important as livestock industries seek to maximise efficiency of producing animal products to meet world requirements. Aim Twenty-four silages were fed to sheep and cattle to test the validity of using sheep-derived digestibility estimates for cattle. Method The silages tested included temperate and subtropical forages, and differed in level of maturity and weed contamination at harvest: several of the forage crops were grown with irrigation. In vivo comparisons were made for digestibility of dry matter (DMD), organic matter (OMD), and organic matter in the dry matter (DOMD) across two experiments. Intake was restricted to 16.5 g/kg liveweight and those silages with low nitrogen (N) contents were supplemented with urea to meet minimum dietary crude protein requirements. Key results DMD, OMD and DOMD ranged from 0.538 to 0.773, 0.550 to 0.810, 0.505 to 0.762 and 0.551 to 0.749, 0.584 to 0.786, 0.539 to 0.702 for cattle and sheep respectively. DMD, OMD and DOMD determined in sheep explained 88.7, 86.3 and 78.4% of the variation of DMD, OMD and DOMD in cattle respectively. In Experiment 1, DOMD was higher in cattle than sheep but for two silages (Silage 1, Subterranean clover: 0.631 vs 0.589; Silage 5, Annual ryegrass/oats, early cut: 0.761 vs 0.702) whereas in Experiment 2 DOMD was lower for cattle than sheep for one silage (silage 21, maize: 0.645 vs 0.691, s.e.d. = 0.019). Conclusions and Implications Since there was no clear trend for sheep to digest higher quality feeds better than cattle or for cattle to digest lower quality feeds better than sheep, we conclude that, at least for silages made from forage, sheep-derived values for digestibility should, in most instances, be applicable to cattle.

Are dietary strategies to mitigate enteric methane emission equally effective across dairy cattle, beef cattle, and sheep?

The digestive physiology of ruminants is sufficiently different (e.g., with respect to mean retention time of digesta, digestibility of the feed offered, digestion, and fermentation characteristics) that caution is needed before extrapolating results from one type of ruminant to another. The objectives of the present study were (1) to provide an overview of some essential differences in rumen physiology between dairy cattle, beef cattle, and sheep that are related to methane (CH₄) emission; and (2) to evaluate whether dietary strategies to mitigate CH₄ emission with various modes of action are equally effective in dairy cattle, beef cattle, and sheep. A literature search was performed using Web of Science and Scopus, and 94 studies were selected from the literature. Per study, the effect size of the dietary strategies was expressed as a proportion (%) of the control level of CH₄ emission, as this enabled a comparison across ruminant types. Evaluation of the literature indicated that the effectiveness of forage-related CH₄ mitigation strategies, including feeding more highly digestible grass (herbage or silage) or replacing different forage types with corn silage, differs across ruminant types. These strategies are most effective for dairy cattle, are effective for beef cattle to a certain extent, but seem to have minor or no effects in sheep. In general, the effectiveness of other dietary mitigation strategies, including increased concentrate feeding and feed additives (e.g., nitrate), appeared to be similar for dairy cattle, beef cattle, and sheep. We concluded that if the mode of action of a dietary CH₄ mitigation strategy is related to ruminant-specific factors, such as feed intake or rumen physiology, the effectiveness of the strategy differs across ruminant types, whereas if the mode of action is associated with methanogenesis-related fermentation pathways, the strategy is effective across ruminant types. Hence, caution is needed when translating effectiveness of dietary CH₄ mitigation strategies across different ruminant types or production systems.

The combined effects of animal species (sheepversuscattle) and level of feeding on digestible and metabolizable energy concentrations in grass-based diets of cattle

A total of 317 dairy and beef cattle, offered grass silage-based diets, have been subjected to energy metabolism measurements in calorimetric chambers in 11 feeding experiments at this Institute. In addition the silages (no. = 33) were also given individually to sheep as a sole food at maintenance feeding level for measurement of energy intake and outputs (faeces and urine). The digestible (DE) and metabolizable (ME) energy concentrations of mixed diets for sheep at maintenance were estimated using these measured silage data, predicted silage methane energy output and tabulated energy values of concentrates. The objective of the present study was to use treatment mean data (no. = 59), derived from the cattle (production level) (MEprod or DEprod) and the sheep (maintenance level) (MEmaint or DEmaint), to evaluate the combined effects of animal species and level of feeding on dietary ME or DE concentration. The mean-square prediction error technique and the sensitivity test both indicated that there was little bias derived from the deviation of the slope (line bias) when relating MEprod (DEprod) with cattle to MEmaint (DEmaint) with sheep. Relating feeding level to the decline in ME or DE concentration (from maintenance to production level) revealed that the constant had no significant effect on the relationship, suggesting that there was little difference in dietary ME or DE concentration between sheep and cattle when given food at maintenance. ME d and DE d were significantly related to MEmaint and DEmaint (P < 0001) respectively. These two relationships were however influenced (P < 0001) by level of feeding above maintenance (FL-1). There was little effect of silage DM proportion in the total diets (S/T) on the depression of ME concentration from maintenance to production levels, while this effect on the depression of DE concentration was significant (P < 0001). Therefore, the following two equations are recommended to calculate MEprod and DEprod concentrations respectively for cattle using data obtained with sheep at maintenance. Alternatively, with each unit increase in feeding level above maintenance, dietary ME and DE concentrations respectively were reduced by proportionately 0016 and 0025 for grass silage-based diets, irrespective of the effect of forage proportion on the latter. MEprod = [1 068 - 0019 ✕ (FL-1)] ✕ MEmaint - 0·755 DE d = [0·891 + (-0027 + 0018 ✕ S/T) ✕ (FL-1)] ✕ DEmaint + 1·355

Effect of donor animals and their diet on in vitro nutrient degradation and microbial protein synthesis using grass and corn silages

Two nonlactating cows and two wether sheep, all fitted with a permanent cannula into the rumen, were fed either hay plus concentrate, grass silage or corn silage to study the effect of the donor animal and its diet on in vitro fermentation and microbial protein synthesis. Rumen inoculum was obtained before the morning feeding. Grass silage or corn silage was incubated in a semi-continuous rumen simulation system for 14 days. Four replicated vessels were used per treatment. Degradation of crude nutrients and detergent fibre fractions as well as microbial protein synthesis and the production of volatile fatty acids were studied. Additionally, total gas and methane production was measured with a standard in vitro gas test. Gas production and methane concentration was higher when the inoculum used was from sheep than that from cows. The donor animal also affected the degradation of organic matter and ether extract as well as the amount of propionate and butyrate, and the acetate-to-propionate ratio. The effect of the diet fed to the donor animal on fermentation was much greater than the effect of the donor animal itself. Feeding hay plus concentrate resulted in higher gas production and degradation of acid detergent fibre, but in lower degradation of ether extract and reduced microbial protein synthesis. Additionally, the pattern of volatile fatty acids changed significantly when the diet of the donor animals was hay plus concentrate or one of the silages. These results show that in vitro fermentation and microbial protein synthesis is different when based on inoculum from either cattle or sheep. The diet fed to the donor animal is more important than the animal species and is probably mediated by an adjusted microbial activity. With regard to standardized feed evaluations, these results further support the need to harmonize in vitro approaches used in different laboratories.

Short Communication: Effects of Feeding Level on Energy Concentration in Grass Silage-Based Diets Offered to Dairy Cattle

Twelve grass silages were offered to sheep as a sole diet at maintenance and to lactating dairy cows ad libitum as mixed silage and concentrates diets (n = 13 diets). Fecal and urinary energy outputs were measured for silages and mixed diets. Digestible energy (DE) and metabolizable energy (ME) concentrations for mixed diets with sheep at maintenance were estimated based on the silage dry matter (DM) proportion obtained in the cattle trials, the silage energy utilization values (methane energy-predicted) determined using sheep, and tabulated concentrate values. A comparison of dietary mean data (n = 13) indicated that concentrations of ME (P < 0.01) and DE (P < 0.001) in mixed diets were significantly lower for cows at production feeding level than for sheep at maintenance. The reductions were proportionately 0.015 and 0.020 with each unit increase in feeding level above maintenance, respectively. These ME and DE data were also used to evaluate the feeding level correction factors previously proposed by Van Es (1975) (ME, 0.018) and Yan et al. (2002) (ME, 0.016; DE, 0.025) using the mean square prediction error technique. The ME correction factor proposed by Yan et al. (2002) had a greater prediction accuracy than that proposed by Van Es (1975) for the prediction of ME concentration in mixed diets offered to dairy cattle at production feeding level.

Comparative digestion in cattle and sheep fed wheat silage diets at low and high intakes

Winter wheat (Triticum aestivum L.), harvested at late milk, early dough, and hard dough stages of maturity was ensiled for nutritive comparisons. Diets were adjusted to 13% CP with a soy protein concentrate and fed to six ruminally fistulated growing steers and nine adult wethers in a repeated 3 x 3 Latin square design to study the effects of maintenance and ad libitum intakes on digestibility of different feed fractions. At both intakes, digestion values for the steers were greater than or equal to those for the sheep for all feed fractions except CP. Wethers achieved greater intake per unit of BW than steers during ad libitum intake. Voluntary OM intakes of steers only differed between the milk stage diet and the dough stage diets. At low intake, the diets containing the more mature silage were more digestible. At high intake, the OM of diet containing the early dough stage silage ws most digestible. Increased intake caused a depression in digestibility of different feed fractions. The magnitude of the depression varied among diets and fractions. Data indicated that the nutritive value of diets based on whole crop wheat silage is affected by stage of maturity, animal species, and amount of intake. The assessment of the nutritive value of diets based on whole crop wheat silage should therefore be made with the animal species and at the amount of intake for which the diets are intended.

[Comparative studies of the parameters of rumen fermentation and the digestibility of feed rations in cattle and sheep. 2. The digestibility of feed rations]

The results from 283 comparisons of digestibility in cattle (ox, cow, male and female young cattle) and sheep (adult wether) are presented. The crude protein content of the applied rations ranged from 90 to 340 and the crude fibre content from 80 to 430 g/kg DM. Within the range of rations with 200-350 g crude fibre per kg DM the differences between adult cattle and wether in the digestibility of energy and organic matter don't exceed 1%-unit (mean -0.5 +/- 2.5), that of crude protein is 5%-units lower in adult cattle than in adult wether. In young cattle digestibility is altogether lower than in wether; in young cattle with 120 to 200 kg live weight 4 to 6 and in more developed cattle 3 to 4 digestibility units for energy. In the metabolizability of the energy in comparison between adult wether and the different animal categories of cattle the difference don't exceed 1.5%-units. Relations between the live weight of cattle, the crude fibre of the rations as well as the nutrition level and the amount of difference of digestibility between cattle and sheep are considered.

Effect of virginiamycin on in vivo digestibility, rumen fermentation and nitrogen balance

Three experiments were conducted to investigate the effect of virginiamycin. Digestibility was determined with wethers, fed a diet of 0.65 maize silage and 0.35 concentrate on a dry matter basis (Experiment I) or a complete dry feed (Experiment II) at maintenance, and with growing bulls fed a maize silage diet ad libitum supplemented with 7.5 g concentrate per kg live weight (Experiment III). Virginiamycin was incorporated at 0 or 65 ppm in the concentrate and 0 or 25 ppm in the complete dry feed. No significant effect on dry or organic matter digestibility was observed, although digestibilities of protein and ether extract were reduced by virginiamycin in experiments I and II, respectively. Rumen fermentation was studied in experiments I and II. Virginiamycin increased acetic acid concentration and reduced butyric acid concentration in experiment I, but exerted no significant effect in experiment II. An interaction between diet type and virginiamycin was found for the C2/C3 ratio. Nitrogen balance, measured in experiment III, was not affected by virginiamycin.

Comparative digestion in sheep and cattle fed different forage to concentrate ratios at high and low intakes

Effect of maintenance and ad libitum intakes on digestibility of different feed fractions was studied with six ruminally fistulated cows and six ruminally fistulated wethers to validate the use of sheep as a model for cattle. Complete diets were made up of ratios of alfalfa:cracked corn and soybean meal of 80:20, 55:45, and 30:70. The regression coefficient of the line relating organic matter digestibility with proportion of concentrate in the diet was smaller for the cows at ad libitum intake than for the other groups. Increasing the intake caused a decrease in digestibility of different fractions. The depression in digestibility was greater for the 30:70 forage:concentrate diet than for the others. At high intake, digestion values in the cows were less than those in the sheep for all diets. An increase in intake depressed the digestion of cell wall fractions and cell solubles including starch in cows, whereas in sheep, an increase in intake reduced cell wall digestion and to a lesser extent cell solubles, without affecting starch digestion. The digestive physiology of these species is sufficiently different to preclude the use of sheep data in formulating nutrient requirements for cows.