The digestibility of crude nutrients in horses. 1. Methods of determining digestibility

The ascertainment of the digestibility of crude nutrients in rations for horses requires the inclusion of movement-based performance as influencing factor. Under the consideration of this requirement, indicator methods gain significance in comparison with the standard method of collecting faeces completely. In two experiments the digestion of the crude nutrients in rations for horses was tested according to the standard method (complete collection of faeces) and the indicator method 4 N HCl-insoluble ash). According to the indicator method the digestibility of crude nutrients was slightly higher, the differences to the values of the standard method were statistically insignificant. Under consideration of the inhomogeneity of horse faeces and the possibility of doing without the complete collection of faeces, the indicator method with 4 N HCl-insoluble ash is to be preferred to the standard method. The analysis of air-dried faeces connected with the indicator method resulted in improved reproducibility due to the significantly better homogeneity. A recommendation is made for carrying out digestibility experiments with horses, in which the 4 N HCl indicator method is used.     

The effect of a straw meal on the crude protein and amino acid metabolism and digestibility of the crude nutrients in broiler hen breeds. 2. Digestibility of crude nutrients of rations and 15N from a straw meal and wheat

In experiments with colostomized broiler hens apparent digestibility of the crude nutrients of the ration after straw meal supplements of 20, 30 and 40 g per animal was determined. In addition, the 15N digestibility of straw meal and wheat was ascertained on the basis of straw meal supplements. The digestibility of the crude nutrients of the rations decreased significantly (P less than 0.05) after the straw meal supplement. The adaptation of the test animals to the straw meal intake resulted, at a daily consumption of 20 g straw meal, in an increase of the apparent crude fat digestibility (P less than 0.05) in dependence on the time of straw meal feeding, in which the original values without straw meal supplement were not reached. The digestibility of the 15N excess (15N') of the wheat was, at 86 +/- 1%, largely independent of the straw meal intake. The apparent digestibility of the straw-15N excess in broiler hens of 42 +/- 8 to 55 +/- 2% is surprisingly high.     

Comparative study of blood coagulation tests in the horse and pony

The clotting times obtained with different assay procedures for routine coagulation tests were examined for horse and pony samples. The whole blood clotting time test and the activated coagulation test seemed to give similar results when both tests were done at 22 C. The results obtained for the activated partial thromboplastin time assay varied, depending on the commercial reagent used for the test. Consistent results were obtained for the one-stage prothrombin time assay with each reagent used.     

Hypertrophic osteopathy in three horses and a pony.

Hypertrophic osteopathy was diagnosed in 3 horses and in a pony, ranging in age from 8 to 21 years. There were 2 females, 1 sexually intact male, and 1 gelding. In 3 animals, hypertrophic osteopathy was associated with pulmonary abscesses, bronchogenic squamous cell carcinoma, and ovarian granulosa-cell tumor, respectively, and resulted in death or euthanasia. Duration of the condition ranged from 1 to 4 months. In 1 horse, hypertrophic osteopathy was believed to be secondary to pregnancy, and resolved following uncomplicated delivery of a live foal.     

The effect of very low food intake on digestive physiology and forage digestibility in horses

Equid digestion is often conceptualized as a high‐throughput/low‐efficiency system, in particular compared with ruminants. It is commonly assumed that ruminants have an advantage when resources are limited; the effect of low food intake on digestive physiology of horses has, however, not been explored to our knowledge. We used four adult ponies [initial body mass (BM) 288 ± 65 kg] in two subsequent trials with grass hay‐only diets [in dry matter (DM): hay1, mid‐early cut, crude protein (CP) 10.5%, neutral detergent fibre (NDF) 67.6%; hay2, late cut, CP 5.8%, NDF 69.5%], each fed subsequently at four different dry matter intake (DMI) levels: ad libitum and at 75, 55 and 30 g/kg^0.75/day. We particularly expected digesta mean retention times (MRT) to increase, and hence fibre digestibility to increase, with decreasing DMI. Ponies maintained BM on the first, but lost BM and body condition on DMI55 and DMI30. MRTs were negatively correlated to DMI and ranged (for particles <2 mm) from 23/31 h (hay1/2) on the ad libitum to 38/48 h on DMI30. Digestibilities of DM, nutrients and fibre components decreased from DMI75 to DMI30; apparent digestibilities of organic matter and NDF (hay1/2) dropped from 47/43% and 42/37%, respectively, on the ad libitum DMI to 35/35% and 30/28% on DMI30. Additional differences evident between the two hays included a higher estimated ‘true’ protein digestibility for hay1 and finer faecal particles on hay2; there were no differences in faecal particle size between intake levels. The results suggest that below a certain food intake threshold, the major digestive constraint is not fermentation time but nutrient supply to gut bacteria. The threshold for such an effect probably varies between feeds and might differ between ruminants and equids.     

The influence of various feedstuffs containing fat and protein on the digestibility of crude nutrients in young calves

Digestibility trials were carried out with calves, aged 3, 5, 7, 9, and 11 weeks, which were fed with feedstuffs of various energy and protein levels (various amounts of dried skim milk supplement with 146, 219, 323 g per day of the milk replacer Laktin) plus concentrate and hay. The purpose of the experiment was to find out what effect the amount of milk replacer varying daily had on the digestibility of the nutrients. The experiments confirm that the amount of milk replacer has a great influence on the digestibility of the crude fat. The amount of digestible crude fat consumed with the feed considerably influcenced the digestibility of the energy, it had little influence on the digestibility of the other nutrients, however. With increasing age the calves received more plant protein sources with a lower biologic value. Thus the digestibility of the protein in the complete ration was diminished as well. This shows that the digestibility was influenced by the protein quality, not, however, by the amount of crude protein. The digestibility of the dry matter andthe organic matter as well as of the N-free extractives in the feed ration diminished according to the changed composition with the increasing age of the animals; in constrast to this the digestibility of the crude fibres increased gradually.     

Differences in serum protein 2D gel electrophoresis patterns of Przewalski's (Mongolian wild horse) and thoroughbred horses

The objective of this study was to assess differences in serum protein expression profiles of Przewalski's (Mongolian wild horse) and thoroughbred horses using proteome analysis. The serum proteins were separated by two‐dimensional electrophoresis (2‐DE) and five different gene products were identified. Proteins represented by the five spots were identified by matrix‐assisted laser desorption ionization–time‐of‐flight (MALDI–TOF) mass spectrometry (MS)/MS technology. The identities of all proteins were deduced based on their similarity to proteins in the human plasma protein database. Three proteins (a haptoglobin‐2 alpha glycoprotein and two haptoglobin‐2beta glycoproteins with different accession numbers) were downregulated in Przewalski's horse sera compared to thoroughbred horse sera. Moreover, two proteins (tetraspanin‐18 and pM5) were upregulated in Przewalski's horses compared to thoroughbred horses. Haptoglobin‐2 alpha and haptoglobin‐2beta may serve as candidate molecules in future studies of inflammation, coagulation, immune modulation and pro‐oxidant and antioxidant activity with consequential effects on the entire metabolism of the horse.     

The effect of straw meal on the crude protein and amino acid metabolism and digestibility of crude nutrients in broiler hen breeds. 1. Problems, experimental review and N-excretion in the urine

The metabolization of the straw N and the influence of the straw on N excretion in urine were studied in 2 experiments with colostomized broiler hens and with 15N labelled wheat straw as well as 15N labelled wheat. In experiment 1 the test animals divided up into 4 groups received 0 g, 20 g, 30 g and 40 g straw meal per animal and day in addition to 120 g mixed feed. The daily 15N-excess (15N') intake from the straw was 18.4 mg, 27.5 mg and 36.7 mg. The amount of 15N' daily consumed with the labelled wheat in experiment 2 was 119.7 mg. 40 g straw meal resulted in a significantly increased amount of urine (p less than 0.05). The amounts of urine N and uric acid N were only increased as a tendency. On average the productive N decreased as a consequence of the straw meal supplement from 1070 mg/animal and day (control) to 764 mg/animal and day after 40 g straw meal supplement. The productive 15N' of the labelled wheat was not influenced by the straw meal supplement. The productive 15N' of the straw increased from 3.8 mg/animal and day (20 g straw) to 13.4 mg/animal and day (40 g straw). In contrast to 15N wheat, straw as a 15N source resulted in a lower labelling of uric acid N in comparison with urine N. It can be assumed that the changed metabolization of the straw N is influenced by microbial processes in the intestines.     

The effect of straw meal on the crude protein and amino acid metabolism and the digestibility of crude nutrients in broiler breeding hens. 3. Digestibility of amino acids

In two experiments with colostomized broiler hens the influence of a straw meal supplement on the apparent digestibility of the amino acids of the ration and the 15N labelled basic amino acids in wheat was studied. In experiment 1 the animals received 120 g mixed feed plus 0, 20, 30 and 40 g straw meal per animal and day. The digestibility of the amino acids decreased on average from 86% to 83%, 80% and 79% with the growing straw intake. In contrast to the control variant, 20 g straw meal intake resulted in a significant decrease of digestibility for lysine, histidine, glycine, tyrosine, phenylalanine, cystine and methionine. 30 and 40 g straw meal reduced significantly the digestibility of all amino acids with the exception of arginine. The amino acid composition of the crude protein in faeces changed only very slightly due to the straw supplement. In experiment 2 15N labelled wheat was a component of the ration. Of the 15N labelled amino acids lysine, histidine and arginine, 88, 90 and 95% were apparently digested. The adaptation of the animals to straw meal intake did not change the digestibility of the amino acids.     

Effects of high-intensity exercise on plasma catecholamines in the thoroughbred horse.

In Study 1, a single speed test of 6 to 12 m/sec was performed for 2 mins at an incline of 5 degrees on a high-speed treadmill (single-step test). Only one speed was performed per session and blood samples were taken before and after the test. In Study 2 horses cantered for 1 min at increasing speeds of 6 to 13 m/sec on an incline of 3 degrees (multiple-step test). Blood samples were taken before exercise, throughout the test and during recovery. In the single-step test plasma concentrations of adrenaline and noradrenaline both increased at speeds of 9 m/sec, as did blood lactate. Mean concentrations of adrenaline and noradrenaline at the end of the 12 m/sec test were 153 and 148 nmol/litre, respectively. Plasma concentrations were similar over all speeds although there was a tendency for the increase in noradrenaline to be greater than that of adrenaline at the lower speeds. The multiple-step test resulted in smaller increases in both adrenaline and noradrenaline. Although again closely correlated, increases in adrenaline were 20-30% greater than those for noradrenaline. In both exercise models, changes in plasma adrenaline and noradrenaline values with exercise showed an exponential relationship to plasma lactate. A plasma half-life of less than 30 secs was indicated during recovery from the multiple-step test. Changes in adrenaline and noradrenaline were much greater than previously recorded in man and emphasise the importance of catecholamines in mediating the physiological response of the horse to exercise.     

The risk of severity of limb injuries in racing thoroughbred horses.

A retrospective study was carried out to identify factors which predisposed Thoroughbred horses to severe injuries, as compared to less severe injuries, while racing on New York Racing Association (NYRA) tracks during the period of January 1986 to June 1988. A severe injury was defined as an injury which led to humane destruction of the horse. A less severe injury was defined as a horse which didn't race within 6 months following a muscular, ligament, tendon, or skeletal injury on the racetrack. The data were obtained from the Horse Identification Department records kept by the Chief Examining Veterinarian of NYRA and included 55 severely injured horses and 245 less severely injured horses. Multiple logistic regression analysis was used to identify factors associated with the risk of severe injuries compared to less severe injuries in those horses. There was a significant association between track and the risk of severe injury (horses raced on Belmont and Saratoga were more likely to develop a severe injury compared to horses raced on Aqueduct Main). The track surface was also associated with the risk of severe injury (horses raced on a firm turf had a significantly lower risk of severe injury associated with the track was significantly modified by the track condition (horses raced at Belmont when it was muddy had a significantly increased risk compared to Aqueduct dirt). Horses were more likely to experience severe injury in the early part of the race (less than or equal to 6 furlongs) than the latter part of the race (greater than 6 furlongs). The risk of severe injury decreased with the age of the horse.     

The effect of reduced drinking water supply on feed absorption, apparent digestibility of crude nutrients and rumen fermentation of sheep

Based on the fact that the insufficient supply of agricultural domestic animals with drinking water in tropical and subtropical regions is often the factor limiting their performance, the effect of different drinking water supply of sheep (ad libitum, 54% of ad libitum and 27% of ad libitum) on various parameters was studied. A water supply reduced to 54 and 27% resp. diminished dry matter intake to 84% and 45% resp. A water supply reduced to 54% improved the digestibility of organic matter, crude fibre, crude cellulose and N-free extractives, it was, however, not significant. A reduction to 27% of the ad libitum water supply improved the digestibility of all crude nutrients, significantly, however, only that of organic matter, crude fibre, crude cellulose and N-free extractives. In comparison with a supply of water reduced to 54%, a water supply reduced to 27% also resulted in an improvement of the digestibility of all crude nutrients. Both the reduction of the ad libitum water supply and the increasing time interval for the sampling of rumen fluid resulted in an increased concentration of volatile fatty acids in the rumen fluid, which was sampled 15 min, 1 hour and 2 hours after feeding.     

The effect of different high doses of field peas on the digestibility of their crude nutrients in colostomized laying hens

Five groups of five colostomized laying hens each received 0 g, 15 g, 30 g, 45 g and 60 g peas of the variety Grapis per animal and day with Triticum rations. The apparent digestibility of the crude nutrients of the rations and the peas was determined, ascertained according to the difference method in dependence on their quotas in the rations. The digestibility of the N-free extracts of the peas increases by 3 digestion units each under the influence of the increasing intake of peas, so that the digestibility of the organic matter of the peas increases with the growing quota. On an average of the 20 individual values the following digestion values for the pea variety Grapis are indicated: organic matter 66.9%, crude protein 78.5%, crude fat 48.7%, N-free extracts 70.3%. Energy concentration amounts to 572 EFU-hen/kg dry matter.     

Comparative study of muscle fiber type composition in the middle gluteal muscle of andalusian, thoroughbred and arabian horses

Samples were taken from the right middle gluteal muscle of 25 Andalusian horses, 20 Thoroughbreds and 10 Arabian horses, all aged between 5-and 12-years-old and not involved in training. Histochemical analysis was carried out using myosin ATPase after acid preincubation (pH 4.4) and NADH-tr in order to determine the percentage of different fiber types. Statistical analysis showed highly significant differences (P<0.001) in the proportion of type 1 and type 2 fibers between breeds. The Thoroughbred was found to have a significantly higher proportion of type 2A fibers (P<0.001) than the other 2 breeds, although differences in the proportion of type 2B fibers in different breeds were not found to be statistically significant. The Andalusian horse was found to have a higher proportion of fast-twitch fibers of low oxidative capacity (type FT) than the other 2 breeds (P<0.001). These results not only confirm those obtained in previous studies of different breeds of horses, but highlight the histochemical differences in the skeletal muscle of breeds of great commercial and sporting interest in Spain.     

Second-intention repair in the horse and pony and management of exuberant granulation tissue.

Second-intention repair is faster in ponies than in horses and faster in body wounds than in limb wounds. To a large extent, the differences between horses and ponies can be explained by differences in the local inflammatory response, which are a result of the functional capacity of leukocytes. In ponies, leukocytes produce more inflammatory mediators,resulting in better local defense, faster cellular debridement, and a faster transition to the repair phases, with more wound contraction. In horses,leukocytes produce fewer mediators, initiating a weak inflammatory response, which becomes chronic. This inhibits wound contraction and gives rise to the formation of exuberant granulation tissue. The anatomic environment that influences the inflammatory response and wound contraction most probably determines the differences between body and limb wounds. In body wounds, better perfusion results in faster initiation of the inflammatory phase. The weaker local resistance results in a greater degree of contraction. In limb wounds, particularly of horses, the initial inflammatory response is weak and wound contraction is restricted. Both factors give rise to chronic inflammation, which further inhibits wound contraction and promotes exuberant granulation tissue. The high incidence of exuberant granulation tissue in limb wounds of horses can thus be explained by the chronicity of the inflammatory response as well as by the common use of bandages during treatment. Chronic inflammation is often not recognized as a cause of exuberant granulation tissue. It must be prevented and treated to promote the healing process. Bandages and casts stimulate the formation of exuberant granulation tissue; however, they are advantageous in many respects and play an important role in support of the overall healing process.     

Evidence of heredity of cribbing,weaving and stall-walking in thoroughbred horses

The investigation involved 1035 Thoroughbred horses aged 3–8 years and raised in Italy. Eighty trainers were interviewed on the occurrence of anomalous behaviour. The incidence of cribbing, weaving and stall-walking in the horses was 2.4, 2.5 and 2.5%, respectively. The incidence of behavioural defects in families containing identified anomalous horses (“probands”) was much higher than in the surveyed population: 30% for cribbing, 26% for weaving and 13% for stall-walking. This would suggest the involvement of a genetic component in the three vices, but due to the limited data available it was not possible to ascertain the inheritance patterns. Imitation of mares by foals was excluded as a main cause of the vices.     

Possibilities of prediction the digestibility of crude nutrients by fullgrown and growing sheep from the crude nutrient content of the rations. 2. Rations with a higher content of crude fibers (mixtures of straw and concentrated feed as sole feed]

Eight variants of recipes for mixtures of straw and concentrated feed with 10 to 60 per cent straw more or less finely ground (86 to 314 g crude fibre per kg dry matter) and fattening feed for lambs (50 g crude fibre per kg dry matter) were checked concerning the digestibility of crude nutrients for fullgrown wethers and 60 to 80-, 80 to 100-and 100 to 120-day-old lambs which had been ablactated at an age of 60 days. The digestibility for wethers was significantly higher than for lambs, between the age groups of which there were no significant differences concerning the digestibility. In accordance with the results with rations on the basis of concentrated feed as checked and described in the first piece of information, the content of crude fibres in the rations had a negative influence on the digestibility of organic matter, NFE and energy whereas there was a positive relation with the digestibility of crude fibres. The regression functions established for mixtures of straw and concentrated feed concerning the dependence of the digestibility on the content of crude fibres showed a relatively good coincidence in the range of a low content of crude fibres with the corresponding regression functions which were described in the first piece of information for rations of concentrated feed. The equations for the digestibility of crude fibres were an exception. In contrast to this, the quantitative relations between crude fibres and the digestibility as established in the first piece of information for rations with a low content of crude fibres cannot be transferred to rations with a higher content of crude fibres.     

The effect of different levels of soybean extract meal on the apparent digestibility of crude nutrients and amino acids in colostomized laying hens

Four colostomized laying hens per group were given a ration of barley and soya bean oil meal (SBM) with 12.5, 25.0 and 37.5% SBM resp. The crude protein intakes were 14.0, 17.7 and 21.4 g per animal and day. The lysine intake raised from 681 mg (group 1) to 1275 mg (group 3) per animal and day. The digestibility of dry matter and of the N-free extracts of the ration decreased with the rising SBM portion in the ration. The digestibility of crude protein remained constant. The investigated amino acids (Lys, His, Arg, Cys, Met) were higher digested in the 37.5% SBM ration than in the 12.5% SBM ration. The following digestibility values for SBM were found by means of the difference method: Dry matter 52.5%, crude protein 83.1%, crude fat 51.7%, crude fibre 5.5%, N-free extracts 50.6%. The level of the SBM did not influence the digestibility of the crude nutrients. The apparent digestibility of lysine from SBM depended on the level of intake and was found to be 82.3, 83.4 and 89.0%, resp. There were no differences in the digestibility of other amino acids.