Effects of alfalfa and cereal straw as a forage source on nutrient digestibility and lactation performance in lactating dairy cows

Abstract

This study was conducted to investigate the nutrient digestibility and lactation performance when alfalfa was replaced with rice straw or corn stover in the diet of lactating cows. Forty-five multiparous Holstein dairy cows were blocked based on days in milk (164 ± 24.8 d; mean ± standard deviation) and milk yield (29.7 ± 4.7 kg; mean ± standard deviation) and were randomly assigned to 1 of 3 treatments. Diets were isonitrogenous, with a forage-to-concentrate ratio of 45:55 [dry matter (DM) basis] and contained identical concentrate mixtures and 15% corn silage, with different forage sources (on a DM basis): 23% alfalfa hay and 7% Chinese wild rye hay (AH), 30% corn stover (CS), and 30% rice straw (RS). The experiment was conducted over a 14-wk period, with the first 2 wk for adaptation. The DM intake of the cows was not affected by forage source. Yield of milk, milk fat, protein, lactose, and total solids was higher in cows fed diets of AH than diets of RS or CS, with no difference between RS and CS. Contents of milk protein and total solids were higher in AH than in RS, with no difference between CS and AH or RS. Feed efficiency (milk yield/DM intake) was highest for cows fed AH, followed by RS and CS. Cows fed AH excreted more urinary purine derivatives, indicating that the microbial crude protein yield may be higher for the AH diet than for RS and CS, which may be attributed to the higher content of fermentable carbohydrates in AH than in RS and CS. Total-tract apparent digestibilities of all the nutrients were higher in cows fed the AH diet than those fed CS and RS. The concentration of rumen volatile fatty acids was higher in the AH diet than in CS or RS diets, with no difference between CS and RS diets. When the cereal straw was used to replace alfalfa as a main forage source for lactating cows, the shortage of fermented energy may have reduced the rumen microbial protein synthesis, resulting in lower milk protein yield, and lower nutrient digestibility may have restricted milk production.

Effect of dietary energy source and level on nutrient digestibility, rumen microbial protein synthesis, and milk performance in lactating dairy cows

“…An increase in digestibility of DM and OM when diets are supplemented with SFC rather than GC has also been reported (Cooke et al, 2009), as has the fact that feed intake was reduced with lowered digestibility of DM (Faverdin et al, 1999). Moreover, with a diet high in digestible energy, the energy intake ceased to increase with ration digestibility (Conrad et al, 1964;Wang et al, 2014). In the current study, HE diets increased the total-tract digestibility of DM, OM, CP, NDF, ADF, and starch, but no such differences were observed between the HE/GC-and HE/SFC-based diets.…”

“…In the present study, both MCP and IADP values were higher in cows fed HE diets, which we propose are associated with greater MP supply and milk protein yield. Previous research has shown that a greater concentration of dietary NFC is positively correlated with MCP yield (Nocek and Russell, 1988;Lascano and Heinrichs, 2011;Wang et al, 2014). In the HE diets, in contrast to the LE diets, CS was replaced with corn silage, thereby increasing the dietary energy level and improving DMI.…”

“…Milk protein secretion in dairy cows is closely associated with their dietary supply of CP, rumen fermentable carbohydrates, and MP (NRC, 2001;Zhu et al, 2013;Wang et al, 2014), whereas energy supply also plays an important role in MCP and MP synthesis. In the present study, both MCP and IADP values were higher in cows fed HE diets, which we propose are associated with greater MP supply and milk protein yield.…”

“…Two 50-mL aliquots of milk were collected during each milking, and these were pooled in a proportion of 4:3:3 (Zhu et al, 2013;Wang et al, 2014). To one subsample, Bronopol (milk preservative, D&F Control Systems, San Ramon, CA) was added as a preservative, and this subsample was then stored at 4°C for future analysis of protein, fat, lactose, TS, and SCC content by infrared analysis (Laporte and Paquin, 1999) with a Foss-Milkoscan Minor (MilkoScan FT120, Foss Electric …”

Biomarker and pathway analyses of urine metabolomics in dairy cows when corn stover replaces alfalfa hay

“…Forage quality greatly affects dairy cow performance [1, 2]. Using traditional nutritional methods, it is difficult to discern metabolic alterations and characterize alterations in key metabolic pathways when dairy cows are fed diets differing in forage quality.…”