The effect of crop maturity on the nutritional value of maize silage for lactating dairy cows. 3. Food intake and milk production

Abstract

Fifty-five multiparous Holstein-Friesian cows were used in a 20-week continuous design study to determine the effect of maize silage maturity on food intake and milk production. Forage maize (cv. Hudson) was harvested and ensiled at target dry matter (DM) contents of 230 (T23), 280 (T28), 330 (T33) and 380 (T38) g per kg fresh weight (FW). The mean values for volatile-corrected DM (VCDM), starch, neutral-detergent fibre (NDF), crude protein and predicted metabolizable energy (ME) content of the four maize silages were 226, 290, 302 and 390 g/kg FW, 114, 274, 309 and 354 g/kg VCDM, 574, 447, 431 and 448 g/kg VCDM, 96, 80, 74 and 75 g/kg VCDM and 10·3, 11·5, 11·6 and 11·2 MJ/kg DM, respectively. Grass silage containing 296 g VCDM per kg FW was produced from the primary growth of a perennial ryegrass sward. At week 3 of lactation cows were allocated to one of five forage treatments offered ad libitum. The forage treatments were either grass silage alone (TGS) or a 3 : 1 DM ratio of maize and grass silage designated as T23, T28, T33 and T38. All cows also received 8·7 kg DM per day of a dairy concentrate. Forage VCDM intake for TGS was lower (P < 0·001) than for T23 to T38. Increasing maize silage DM content from 226 (T23) to 290 (T28) g/kg increased (P < 0·05) forage VCDM intake from 10·9 to 13·3 kg/day but a further increase to 390 (T38) g/kg tended to reduce VCDM intake. When compared with TGS, the inclusion of maize silage increased milk yield from 28·0 kg/day to 29·4, 32·7, 33·0 and 30·8 kg/day for T23 to T38, respectively, the increases being significant for T28 to T38. However, milk yield was reduced (P < 0·05) when the DM content of the maize silage increased from 302 to 390 g/kg. Increasing maize silage DM content from T23 to T33 reduced (P < 0·05) milk fat content from 45·8 to 41·8 g/kg, which was also lower (P < 0·05) than for TGS. The inclusion of maize silage increased fat yield with a significant difference (P < 0·05) between TGS and T28. The inclusion of maize silage increased milk protein content (P < 0·05) and protein yield (P < 0·001) when compared with TGS. While increasing maize silage maturity did not affect (P > 0·05) milk protein content, protein yield was higher (P < 0·05) for the two intermediate DM contents. There were no treatment effects on body condition score. It is concluded that the changes in composition of maize silage with increasing maturity, which are associated with increased starch and reduced NDF content, resulted in large increases in food intake and yield of milk and protein as crops matured from T23 to T33. However, when crop maturity increased further to T38 there was a tendency for DM intake and yield of milk and protein to decline.

Effects of replacing grass silage with maize silages differing in inclusion level and maturity on the performance, meat quality and concentrate-sparing effect of beef cattle

“…In the current study, the high DM maize was harvested at the optimum stage of maturity, as determined by Phipps et al (2000), Keady (2005) from a review of the literature and Keady et al (2008a) to improve animal performance. Replacing grass silage with the low and high DM maize silage altered ME intake by 20.03 and 10.11 and carcass gain by 20.04 and 0.31, respectively.…”

“…As maize crops mature, major changes occur in the chemical composition of the plants; ADF, NDF and CP concentrations decline, whereas starch and DM concentrations increase (Phipps et al, 2000;Keady et al, 2008a). Although the optimum stage of maturity to harvest grass silage for feeding to finishing beef cattle and lactating dairy cows is at the leafy immature stage (Gordon, 1980;Keady et al, 1999Keady et al, , 2003Keady et al, , 2008aKeady et al, and 2008b, for maize silage the intention is to increase starch concentration and consequently harvest as a mature crop.…”

“…Although the optimum stage of maturity to harvest grass silage for feeding to finishing beef cattle and lactating dairy cows is at the leafy immature stage (Gordon, 1980;Keady et al, 1999Keady et al, , 2003Keady et al, , 2008aKeady et al, and 2008b, for maize silage the intention is to increase starch concentration and consequently harvest as a mature crop. Previous studies have shown that the optimum stage of maturity, for milk output of dairy cows, to harvest maize for ensiling is at a DM concentration of ,300 g/kg (Phipps et al, 2000;Keady, 2005;Keady et al, 2008a). From a review of the literature, Keady (2005) reported a quadratic effect of maturity of maize at harvest on subsequent dairy cow performance and concluded that milk yield differed by 0.…”

Effects of silage from maize crops differing in maturity at harvest, grass silage feed value and concentrate feed level on performance of finishing lambs

“…The concentrations of ADF and CP decline, whereas starch concentration increases (Phipps et al, 2000;Keady et al, 2003 and2008b) owing to the fact that the proportion of plant weight accounted for by the cob increases with maturity. Whilst the optimum stage to harvest grass to be ensiled for feeding to lactating dairy cows, finishing beef cattle or pregnant ewes is at the leafy immature state the optimum state , to harvest maize for ensiling is when the plant approaches maturity.…”

Effects of replacing grass silage with either maize or whole-crop wheat silages on the performance and meat quality of beef cattle offered two levels of concentrates

“…These different responses may have been due to variations in the feed value of both the grass and maize silages offered in these studies. More recently, Phipps et al (2000) and Keady et al (2002b) using dairy cows concluded that the optimum stage to harvest maize for improved animal performance was at approximately 300 g/kg.…”