Graduate Thesis Or Dissertation


Ryegrass straw and whole corn plant pellets as alternative roughages for horses Public Deposited

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  • This study involved three separate experiments employing a total of 29 horses and 4 rabbits. The purpose of these studies was to investigate the use of various quantities and forms of ryegrass straw in horse rations, and to determine the use of whole corn plant pellets as an alternative roughage for horses and rabbits. In the first experiment, twenty head of mature (500 kg) mares and geldings were divided into two groups of ten fed Diet I (51% ryegrass straw and 49% concentrates), or Diet II (51% fescue hay and 49% concentrates). The rations were completely pelleted, isonitrogenous, and isocaloric containing 10.8% crude protein and 2.40 Mcal/kg digestible energy (DE). Apparent digestibilities (Mean ± SE) were calculated by utilizing an indicator ratio technique, chromic oxide. Results indicated that dry matter (DM) digestibility was less (P < . 05) for Diet I than for Diet II (DM 56.00 ± 1.8 and 66.0 ± 1.3). There were no differences (P >. 05) between the two diets for acid detergent fiber (ADF 18.5 ± 1. 5 and 21.0 ± 1. 5), or cell wall constituents (CWC 30.8 ± 5 and 36.0 ± 1.7), Apparent crude protein (CP) digestibility in Diet I (76.2 ± .8) was greater (P < .01) than Diet II (70,3 ± 1.0). During a 60-day maintenance trial, body appearance improved considerably. However, considerable wood chewing was noted with most horses during the initial three weeks of the feeding period. Both groups maintained body weight during the trial with average weight gains of 10kg and 1 kg, respectively, for Diet I and Diet H. However, horses fed Diet I consumed 7.9 kg of feed whereas horses on Diet II consumed 7.5 kg. The maintenance and gain in weight, improved appearance and apparent excellent health of the animals in this trial indicated that complete light horse diets can be based upon poor quality roughages such as ryegrass straw. Although the ration based on ryegrass straw was the cheaper per ton, the increased intake made daily feed costs equal. In the second experiment, four mature (500 kg) horses were used in a 4 x 4 Latin square experiment to determine diet preference for a variety of physical forms of ryegrass straw on the basis of nutrient digestibility, consumption and side effects. All forms of straw were similar in composition, varying only in form (longstem, pelleted, cubed or briquetted). Addition of 5% molasses was used both as a binder and to aid palatability. All horses adapted to the compressed straws, but individual horses were hindered initially by the compactness and density of the cubed and briquetted forms. Greater chewing and consumption time of these forms was necessary for splitting and ingesting the straw. Mean voluntary consumption of the densified forms of straw was greater (P <. 01) than for longstem straw (5. 5, 6.4, 6. 0 and 5.9 kg for longstem, pelleted, cubed and briquetted, respectively). Considerable wood chewing was noted among all animals regardless of diet; however, horses consuming the pelleted diet tended to chew even after ingesting the diet. No digestive disturbances, health impairments or choking was noted. Digestibility coefficients indicated that all horses digested equally the CP and ash fractions regardless of diet form. Digestibility of ADF, CWC and DM was lower for pelleted straw than longstem straw (P <. 01) and, furthermore, was lower for the pellets than for the four other diet forms. A possible explanation for this decreased digestibility of pellets may be a faster rate of passage. Data indicate that the mature horse will accept different physical forms of straw. Straw fed as the only source of nutrients will not meet the horses' needs for maintenance over time. Additional research is necessary to determine if concentrates can be incorporated into one of the densified forms to form a complete package feedstuff that might help solve the bulkiness, storage, and transportation problems of conventional hay and grain rations. In the third experiment, whole corn plant pellets (WCPP) contain ing 6. 2% CP, 30.8% ADF and 64. 8% CWC were fed to five mature horses (500 kg) as a completely pelleted total ration (no supplementation). Apparent digestibilities were calculated by utilizing conventional total fecal collection techniques or the acid insoluble ash (ALA) method. Results of the total collection vs. AIA techniques, respectively, were not different (P >. 05) for CP, ADF and CWC, but were different for EE. Similar trials with rabbits indicated higher CP digestibility, but lower ADF and CWC digestibility as compared to horses. Results from total collection and AIA techniques were not different in rabbits (P >. 05). A three month maintenance trial indicated that mature horses could be maintained by feeding 6. 2 kg per day (1. 8% of body weight), but considerable appetite depravity and excessive coprophagy were observed. Supplementation of the WCPP with soybean meal to increase dietary protein content to 10% CP eliminated all coprophagy within five to seven days. Subsequent removal of the supplemental protein source initiated coprophagy again within seven to ten days. Horses fed WCPP alone, practising coprophagy, had higher (P < 05) CP digestibility than when coprophagy was inhibited. Similarly, when WCPP are fed and coprophagy is allowed but not practised during protein supplementation, CP digestibility is significantly higher (P < .05) than when coprophagy is allowed and practised with no protein supplementation. Furthermore, when protein is supplemented to the WCPP, there is a significantly higher (P < . 01) CP digestibility than when WCPP are fed alone with coprophagy inhibited and no protein supplemented. Irrespective of whether or not coprophagy was practiced or protein supplemented, DM, ADF and CWC digestibilities were not different (P > . 05). Data indicate that the mature horse may be maintained on WCPP if supplemented with an adequate protein source. Utilizing the ALA technique for determining apparent digestibilities in horses offers another indicator technique that may be more convenient and easier to use than conventional total fecal collection techniques.
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