Abstract
Feeding high levels of concentrated materials to dairy cows reduces ruminal pH. Cows can resist the decrease in ruminal pH by reducing feed intake, changing feeding patterns, increasing rumination, and enhancing acid absorption from the rumen wall. However, feeding high-energy materials eventually leads to acidosis. In this study, the effect of using different levels of Magnesmax and sodium bicarbonate buffers on dry matter intake, milk yield, and composition in Holstein dairy cows was investigated. Forty Holstein dairy cows, with two to three lactations and an average milk yield of 30±1.5 kg and a weight of 680±23 kg, were fed experimental diets for 60 days in a completely randomized design. The experimental diets included: 1) 0.8% sodium bicarbonate, 2) 0.6% Magnesmax Chitika, 3) 0.8% Magnesmax Chitika, and 4) 1% Magnesmax. Milk fat and milk yield were affected by the experimental treatments. Raw milk produced in the group fed 0.4% Magnesmax was significantly lower than the other groups, and the milk fat was also lower in this group (p≤0.05). Solids-not-fat in the first period (first month of the experiment) in the group receiving 1% Magnesmax was higher than the other groups and had a significant difference with the 0.4% Magnesmax group (p≤0.05). Feed efficiency throughout the rearing period in the groups fed 0.4% Magnesmax, 0.8% sodium bicarbonate, and 0.8% and 1% sodium bicarbonate were 1.49, 1.52, 1.54, and 1.54, respectively, which was a significant difference (p≤0.05). Overall, the use of magnesium oxide had positive effects on milk production and quality.
Introduction
The dairy cattle industry is under great pressure to meet the demand for milk and dairy products. As a result, the size and capacity of dairy farms are constantly expanding, utilizing advanced technologies to improve productivity and efficiency. However, researchers face the challenge of maintaining milk quality while increasing production. Higher milk production requires a greater proportion of concentrate in the diet, but a higher percentage of concentrate can be harmful to the rumen environment, posing challenges to the efficiency of the livestock. To prevent these adverse effects and the occurrence of subclinical rumen acidosis, various additives, particularly buffers, are used. [1] Studies on the etiology, pathogenesis, occurrence, importance, diagnosis, and prevention of ruminal acidosis, with special attention to subclinical ruminal acidosis (SARA), concluded that metabolic acidosis appears to manifest in the feces. In an effort to manage and reduce SARA, feed additives are added to the diet of dairy cows, with buffers being the most commonly used compounds. These can be provided either endogenously (through saliva) or via dietary buffers, with sodium bicarbonate being the most widely used in the industry. Buffers are highly effective in preventing SARA. [2] Mineral buffers are regularly added to the diet to prevent acidosis, especially in diets with low fiber content. [3] Buffers may prevent the overgrowth of acid-resistant Lactobacillus and also prevent the potential drop in rumen pH. However, buffers should not routinely be used to compensate for poor nutritional management. Buffers are compounds that neutralize excess acid in the cow’s digestive system. Grasses that grow rapidly in the spring often lack sufficient magnesium levels, and their consumption can lead to magnesium deficiency and grass tetany. Fresh forages are rich in carbohydrates and simple proteins but are considered poor sources of minerals. [4] The effects of magnesium deficiency are evident in two conditions: milk fever and grass tetany. This deficiency often occurs in older, overweight cows shortly after calving when milk production is high. One of the most important factors in preventing and alleviating these issues is the use of magnesium supplements in the diet. Magnesium oxide is produced through the calcination of magnesium carbonate or magnesium hydroxide or by processing magnesium chloride using lime and heat. Scientific evidence shows that when corn silage is used as the main forage source in the diet, certain buffers and alkaline compounds, such as sodium bicarbonate and magnesium oxide, alone or in combination, increase dry matter intake, milk production, milk fat percentage, milk fat kilograms, and fat-corrected milk yield. Researchers [5] conducted an experiment examining the effect of sodium bicarbonate and magnesium oxide on the performance of dairy cows fed a corn silage-based diet and found that the addition of buffers had no effect on dry matter intake, milk yield, and its components. However, there was a tendency for increased milk fat percentage in buffer-consuming groups, with the highest milk fat percentage recorded in the group receiving the combination of magnesium oxide and sodium bicarbonate [4]. These findings were consistent with those of other researchers. In this study, the effect of different levels of Magnesmax (a processed magnesium oxide product by Chitika) on dry matter intake, milk yield, and composition in Holstein dairy cows was examined.
Materials and Methods
This experiment was conducted in a completely randomized design on 40 lactating Holstein dairy cows, 30±5 days in milk, with two to three lactations, an average daily milk yield of 30±1.5 kg, and an initial weight of 680±23 kg over a 60-day period. Every 5 cows were randomly assigned to one treatment. The feeding program was formulated using the NRC 2001 software. The experimental diets included: 1) 0.8% sodium bicarbonate, 2) 0.6% Magnesmax Chitika, 3) 0.8% Magnesmax Chitika, 4) 1% Magnesmax Chitika. The Magnesmax product, used in this experiment, is a magnesium oxide processed multiple times, produced by Chitika. The experimental diets are shown in Table 1.
Sampling and Data Collection
Since the cows in each treatment (5 cows) were housed in separate pens, the amount of feed added to the trough for each repetition was recorded daily, and the feed leftovers were collected and weighed every morning. To monitor body weight, the cows were weighed at the start of the experiment and again on the final day. Milk yield was measured for five days at the end of each month (three times a day), and the average yield over these five days was recorded for each cow. Milk samples were collected twice a day on the last two days of each month, and after mixing the samples for each cow, they were analyzed separately to determine milk components (fat percentage, protein, lactose, and solids-not-fat) using an Ecomilk device (Model 09064/01, France). Feed conversion ratio was calculated for each repetition by dividing dry matter intake by the kilograms of milk produced.
Statistical Analysis
All data were entered into Excel and organized. Normality tests were performed using JAMP software, and statistical analysis was conducted using the GLM procedure in SAS-9.3 software. Duncan’s multiple range test was used to compare means at a significance level of 0.05.
Results
The effect of using different levels of Magnesmax (processed magnesium oxide by Chitika) on dry matter intake, milk yield, and composition in Holstein dairy cows is presented in Table 2. The results showed that the dietary treatments significantly affected raw milk yield, milk fat, solids-not-fat, dry matter intake, and feed efficiency. Raw milk produced in the first period (first month) in the group fed 0.4% processed magnesium oxide (Magnesmax) was significantly lower than the group fed 1% Magnesmax (p≤0.05), and in the second period (second month), the group fed 0.8% Magnesmax had significantly higher milk production than the groups fed sodium bicarbonate and 0.4% Magnesmax (p≤0.05). Over the entire research period, milk production in the 0.8% and 1% Magnesmax groups was significantly higher than in the 0.4% Magnesmax group (p≤0.05). Milk fat yield during the entire experimental periods was lower in the 0.4% Magnesmax group compared to other groups, with no significant differences among the other groups. Solids-not-fat were significantly higher in the first period in the 1% Magnesmax group compared to the sodium bicarbonate group (p≤0.05). Milk lactose and protein were not affected by the experimental treatments. Dry matter intake in the second period of the experiment was significantly higher in cows fed 0.4% Magnesmax compared to the other groups (p≤0.05). Feed efficiency in the first period was higher in the sodium bicarbonate and 1% Bentomax groups compared to the 0.4% Bentomax group. Over the entire study period, feed efficiency in the 0.4% Magnesmax group was lower than in the other groups (p≤0.05). Body weight changes were not affected by the dietary treatments.
Discussion
In animal diets, buffers are considered neutralizers of excess acid in the digestive system of animals, similar to the animal’s saliva, providing buffering compounds (bicarbonates) and increasing the animal’s ability to overcome the negative effects of excessive acid in the digestive system. Milk production was affected by the experimental treatments, with the lowest milk production observed in the group receiving the lowest amount of buffer (0.4% Magnesmax). Researchers examined the metabolic and dietary effects of using different levels of sodium bicarbonate and magnesium oxide in cow diets and reported that using higher levels of buffers increased milk yield, dry matter intake, and milk composition.
