Renata Klebaniuk
Effectiveness of glucogenic preparation in the diets containing grains with different ruminal starch degragation in high yielding dairy cows
High-yielding dairy cows, particularly at the periparturient period, need special nutritional management strategies having a positive effect on fertility and reproduction. The present study provides the insight into a choice of a glucogenic nutritional supplement for periparturient cows and its influence on feedstuff intake, digestibility of dietary rations employed, metabolic disorders incidence, milk production efficiency and its constituents and finally, chosen biochemical parameters of blood and urine. The effectiveness of this supplement was also evaluated in the diets, who different in degradability of gram starch in the rumen. 
The research material was constituted by the high producing cows in 2–5 lactation (experiment 1 included 40 animals, experiment 2–56 and experiment 3–60) fed individually. The rations contained maize silage, grass haylage, meadow hay and concentrate mixture. The objective of experiment i was to evaluate efficiency of three dietary glucogenic supplements and to choose one of them for further studies. The following glucogenic additives were applied: 1) propylene glycol (mixture of liquid and loose propylene glycol), 2) mixture of liquid propylene glycol and loose sodium propionate, 3) a glucogenic preparation formulated by the present author (GPM) comprising propylene glycol (40%), sodium propionate (40%), molasses (15%) and stabilizators (5%). The tested supplements were administered to cows for 4 weeks (1 week pre-calving until the end of 3rd week of lactation) in the dose 350 g/animal/day, (once a day with the morning meal). Experiment II aimed to establish the optimum content of one nutritional supplement selected in experiment i as well as to determine its optimum application period. In this experiment, the cows received the glucogenic preparation (GPM) at a varied level, i.e. 200, 350 or 500 g/animal/day for 4 weeks (beginning in a pre-calving week and continuing till the end of 3rd week post-calving) or for 7 weeks (1 week pre-calving until the end of 6th week of lactation). The full GPM dose was administered like in experiment 1. The third experiment focused on the efficiency of the supplement supply (in the quantity and duration recognized as most beneficial in experiment 2. (to the diets contained grains with different rate of starch degradation in the rumen). The cows from control groups (K 3.1, K 3.2 and K 3.3) received cereal-based mixtures of varied starch susceptibility to ruminal degradation (MI – maize as the only cereal, M2 – wheat and barley (50 : 50%); M3 – maize, wheat and barley (50 : 25 : 25%), without any glucogenic preparation. The cows from the experimental groups (G 3.1, G 3.2, G 3.3) were supplied with GPM in amount 500g/animal/day for 7 weeks (1 week pre-calving until the end of 6th lactation week). The concentrate were all the same like in the control groups.
During the experiments, feed intake, cow milk performance and a content of milk protein, fat and urea were evaluated as well as cow`s physical condition, digestibility of basic nutrients and some blood biochemical parameters. There was computation of dietary units used to produce 1 kg FCM and making up the energy reserve needed to build up the body condition.
The performance parameters and health benefits have confirmed superiority of the glucogenic preparation formulated by the present author (GPM) to pure glucogenic substances. GPM proved to be a supplement that enhances the glucose synthesis in the liver, increases its blood plasma concentration and stabilizes the biochemical changes in organism. The GPM efficiency was dependant on the preparation content, amount, application period and degradation rate of diets gram starch in the rumen.
The employed glucogenic additives are effective at increasing milk yield, minimizing a decline of cow body condition and decreasing energy unit use per 1 kg FCM production. The supplements were shown to affect the values of blood biochemical parameters (an increase of a glucose content but a decrease of beta-hydroxybutyric acid level, free fatty acids, uric acid and urea concentration, elevated AP activity along with concurrent growth of blood plasma phosphorus and AST and ALT activity) and urine (decreased glucose and BHM content).
Out of the investigated glucogenic preparations, the one formulated by the present author (GPM) (proved most efficient when supplied in the dose 500 g/day/animal for 7 weeks (1 week prepartum and continued for 6 weeks postpartum). GPM induced improvement of nutrient digestibility, promoted growth of cow milk yield as well as milk composition optimization. Milk from cows with GPM additive had a significantly higher phosphorus content (by 7,5%) and zinc (by 60%). Besides, in cow blood plasma elevated concentration of Ca (13%), P (15%), Zn (5%) and Fe (6,5%) was detected compared to the control groups.
Positive interaction has been demonstrated between GPM and the rations with grain of varied starch susceptibility to ruminal degradation with regard to the discussed parameters. The highest milk performance at the lowest cow energy input per milk production unit and the lowest body condition loss in the investigated period were established in the cows fed GPM added to the rations with concentrate based on maize, wheat and barley at 2 : 1 : 1 ratio. The animals from this group showed the highest percentage of HDL-Chol fraction in total cholesterol, increased phosphorus level in blood plasma as well as reduction of AST and ALT activity. Whereas, the cows supplied with GPM and rich ration comprising a wheat and barley content or both cereals with maize, were shown to have higher digestibility of total protein and starch.