Amir Balakhial2, Abasali Naserian1*, Alireza Heravi moussavi2, and Reza Valizadeh1
1 Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
2 Excellence Center for Animal Science, Ferdowsi University, Mashhad, Khorasan Razavi, Iran
* Corresponding author: Abasali Naserian, Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran. Email: abasalin@gmail.com
ABSTRACT
Introduction: Providing good quality forage in dairy cattle diet is vital for the dairy farm industry. Canola forage was newly added to dairy cows’ diet in Iran. The present study aimed to determine the effects of replacing corn silage with canola silage on feed intake, apparent digestibility, milk yield, milk composition, and thyroid hormone levels of dairy cattle in Mashhad, Iran.
Materials and methods: Nine Holstein cows were used in this study and were allocated in a 3×3 change over Latin square design study. The trial consisted of 3 periods, each lasting for 20 days. The first 15 days were considered an adaptation period. Experimental diets were formulated to provide 33% of the total dry matter (DM) as forage. Canola silage was substituted with corn silage at levels of 0, 50, and 100% of DM.
Results: Dietary concentrations of neutral detergent fiber (NDF) and acid detergent fiber increased when corn silage was replaced by canola silage. Replacing corn silage with canola silage caused a significant decrease in DMI. The apparent digestibility of DM and crude protein were not affected by dietary replacement of corn silage with canola silage; however, organic matter and digestibility of NDF decreased significantly. When corn silage was replaced by canola silage, there were no significant changes in milk yield, fat corrected milk, and milk composition in the investigated cattle, but milk protein changed
significantly. The results indicated that 50% substitution of canola silage caused higher milk protein. Rumen fluid pH and its ammonia nitrogen concentration increased significantly in experimental animals. The concentrations of T3 and T4 decreased, whereas blood urea nitrogen concentration increased by dietary replacement of corn silage with canola silage.
Conclusion: Canola silage can be substituted with corn silage, and feeding canola silage can be beneficial in some aspects.
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Introduction
Providing good quality forage in dairy cattle diet is vital for the dairy farm industry 1. In some semitropical countries, such as Iran, low rain in the last decade has led to a decline in forage production2. On the other hand, Iran’s government planned to increase vegetable oil production2,3, which has increased canola cultivation over the past decade. Canola is one of the oilseed plants that belong to the Brassica species4. Decrease in environment temperature or acute damage by pests makes canola cultivation difficult5. In this situation, most farmers eliminate damaged canola forage by burning or burying it in the ground. In this condition, there is a question about the possibility of utilizing canola forage in ruminant nutrition. Some studies indicated the nutrient composition of canola silage and its positive effects on dairy cattle performance6-8. Moreover, a study on the effects of adding different levels of rapeseed (canola seed) silage on the diet of beef cattle indicated that tract digestibility and NDF were greater in high glucosinolate rapeseed varieties9. Given the above-mentioned, the current study aimed to determine the effects of substituting corn silage with canola silage on feed intake and apparent digestibility of nutrients, milk yield, and milk composition.
2. Materials and Methods
2.1. Ethical approval
All animals were treated in accordance with the regulations on the guidelines of the Iranian Council of Animal Care (1995), and the experiment was approved by the Iranian Ministry of Agriculture (experimental permission no. 1828).
2.2. Experimental design
In the current study, 9 Holstein dairy cows with a mean parity of 2.5 (mean ± SD), mean body weight of 556 kg (mean ± SD), days in milk (DIM) of 89.3 ± 21.19 (mean ± SD), and milk yield of 41.7 ± 4.0 kg/ d (mean ± SD) were allocated in a 3×3 change over Latin square design study. This study contained three periods, each lasting 20 days. The first 15 days of each period were the adaptation period. Every 5 days, a composite diet sample was collected (4 times during each period). Both
corn (Agratech 787, Agra Tech Seeds, Inc., Ashburn GA) and Canola (Hyola-308) were plated in the sandy soil on
April 6, 2019, and irrigation was provided to supplement natural rainfall. Corn was chopped and stored in a concrete silo on August 11, 2019, and canola was mown on August 4, 2019, and allowed to wilt to approximately 20% DM before being chopped and stored in a concrete stave silo. Diet was offered twice daily as a total mixed rations (TMR) at 1000 hours and 1500 hours. Forage was 33% DM of the diet (Table 1). In the present study, the experimental diet was substituted for 0, 50, and 100% with corn silage DM. Samples of diet (0.5 kg) were collected during the experiment and stored at -20°C until analysis. The DM content of the experimental diet was determined by drying in the oven at 55°C for 48 hours10.
