Table 5. Intake and performance of dairy cows fed diets containing long chop grass silage (LG); short chop grass silage (SG); long chop grass and maize silages (LM), or short chop grass and maize silages (SM).


Treatments LG


DM intake (kg/day) Milk yield (kg/day) Milk fat (g/kg) Milk fat (kg/day) Milk protein (g/kg) Body condition score NDF digestibility (kg/kg) Eating (h/d)


Eating (min/kg DMI) Rumination (h/d)


Rumination (min/kg DMI)


20.0 37.3 40.1 1.49 30.9 2.41 0.61 5.8


17.3 9.3


28.1 SG


20.5 39.1 38.5 1.50 30.7 2.52 0.67 4.9


14.5 10.0 29.2


LM


22.8 41.1 39.5 1.60 32.3 2.51 0.42 4.6


12.2 10.1 26.8


SM


24.0 40.5 38.6 1.55 32.4 2.74 0.41 4.0


10.3 10.0 25.3


SED 0.56 0.63 0.93


0.044 0.28


0.060


0.0290 0.30 0.96 0.23 0.79


C


0.035 0.179 0.090 0.477 0.738


<0.001 0.323 0.003 0.021 0.084 0.709


Tayyab et al. (2019) C = chop length; F = forage mix; C x F = interaction between chop length and forage mix


cows fed diets containing maize compared to the grass silage only diets (Figure 2). It was concluded that there was little benefit to rumen pH from feeding a longer chop length grass silage, and there may be a reduction in animal performance. In a second study Tayyab (2019) examined the effect of starch


concentration in diets with a very short grass silage for the UK (particle length of 23 mm) or a grass/maize silage based ration. Total dietary starch concentrations ranged from 90 g/kg DM to 320 g/kg DM, which is considerably higher than the maximum of 237 g/kg DM reported in the survey of Tayyab et al. (2018; Table 6). There were improvements in performance with a higher inclusion


rate of maize silage, but the effect of dietary starch levels on rumen pH was surprisingly small, with a mean value across all diets of approximately pH 6.15, and a minimum of pH 5.7. One important aspect of this study was that cows were individually fed ad libitum, with fresh feed delivered four times per day, resulting in little opportunity for diet selection. When taken in combination with the survey results of Tayyab


Table 6. Production performance of cows fed diets containing a high grass:maize silage ratio (82:18) with a high NDF content (GF), high grass:maize silage ratio (82:18) with a high starch content (GS), low grass:maize silage ratio (18:82) with a high NDF content (GF) or a low grass:maize silage ratio (18:82) with a high starch content (MS).


Treatments GF DMI, kg/d


Milk yield, kg/d 4% FCM, kg/d Fat, g/kg Fat, kg/d


Protein, g/kg Protein, kg/d Mean pH Min pH


23.1 40.9 40.7 39.7 1.63 30.3 1.23 6.19 5.72


GS


23.1 40.6 41.4 41.2 1.66 30.8 1.24 6.20 5.84


MF


24.9 44.5 40.7 36.5 1.63 31.5 1.40 6.08 5.71


MS


24.1 41.9 40.4 38.7 1.62 32.0 1.34 6.11 5.69


SED 0.67 1.15 0.99 0.79 0.04 0.34


0.046 0.055 0.112


F


0.047 0.038 0.531 0.007 0.531 0.007 0.015 0.607 0.552


F = forage source, C = concentrate composition, F × C = interaction between F and C, FCM = fat corrected milk FEED COMPOUNDER MAY/JUNE 2019 PAGE 43 P value C


0.436 0.161 0.753 0.033 0.753 0.107 0.476 0.087 0.380


F × C 0.450 0.239 0.504 0.584 0.504 0.837 0.308 0.796 0.461


Figure 2. Hourly reticular pH in cows fed diets containing long chop grass silage (LG; -●-); short chop grass silage (SG; ▲ ); long chop grass and maize silages (LM; --o--), or short chop grass and maize silages (SM; --▲--). (SED, 0.042; Time, P<0.001; forage ratio, P=0.003; Time×F, P<0.001). Tayyab et al. (2019)


P-value F


<0.001 <0.001 0.560 0.012


<0.001 <0.001 <0.001 <0.001 <0.001 0.013


<0.001


C × F 0.335 0.011 0.418 0.376 0.461 0.138 0.140 0.463 0.520 0.029 0.026


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