The effects of concentrate energy source on milk composition of lactating dairy cattle offered grass silage

Two partially balanced change-over design experiments were undertaken to examine the effects of concentrate energy source on milk yield and composition of lactating diary cows offered a diverse range of grass silages. A total of nine silages differing in fermentation digestibility and intake characteristics were produced in experiments 1 and 2. Silage dry matter (DM) concentration ranged from 170 to 473 g/kg, ammonia nitrogen ranged from 58 to 356 g/kg nitrogen, digestible organic matter in the DM ranged from 551 to 724 g/kg and silage DM intake potential ranged from 57 to 103.8 g/kg w0.75 respectively. In experiment 1, 5 concentrates were formulated to contain similar concentrations of crude protein (CP), effective rumen degradable protein (ERDP), metabolizable energy (ME) and digestible undegradable protein (DUP) while three concentrates were formulated in experiment 2 to contain similar concentrations of CP, ME and DUP. The concentrates were prepared using barley, wheat, sugar beet pulp and citrus pulp as energy sources and formulated to achieve a wide range of starch concentrations. Starch concentrations ranged from 50 to 384 g/kg DM and 22 to 273 g/kg DM in experiments 1 and 2 respectively. There were no concentrate energy source by silage type interactions for silage intake, milk yield and composition. It is concluded that increasing starch intake resulted in positive and negative linear relationships for milk protein (P<0.001, R2 = 0.96) and fat (P<0.001, R2 = 0.85) concentrations respectively. Concentrate energy source had no effect on silage DM intake or milk yield.

The effects of energy source and level of digestible undegradable protein in concentrates on silage intake and performance of lactating dairy cows offered a range of grass silages

The effects of energy source and level of digestible undegraded protein (DUP) in concentrates on silage intake and performance of lactating dairy cows, offered one of a range of grass silages differing in digestibility and intake characteristics, were evaluated in a partially balanced change-over design experiment involving 48 cows. Four silages were prepared using differing management practices prior to and during ensiling. All silages were treated with an inoculant additive. For silages A, В, С and D, dry matter (DM) concentrations were 199, 320, 313 and 223 (s.e. 4.6) g/kg, pH values 3.82, 4.03, 4·03 and 5·27 (s.e. 0.056), ammonia nitrogen (N) concentrations 58, 122, 66 and 356 (s.e. 13.2) g/kg total N and in vivo DM apparent digestibilities 077, 0.75 , 0.60 and 0.60 (s.e. 0·013) respectively. When offered as the sole diet to 12 dairy cows in a partially balanced change-over design experiment, silage DM intakes were 14.7, 14.7, 12.7 and 10.5 (s.e. 0·36) kg/day respectively for silages А, В, С and D. Six concentrates containing three starch concentrations, each at two levels of DUP, were formulated to have similar concentrations of crude protein, metabolizable energy (ME) and fermentable ME. For the low and high starch concentrates and low and high levels of DUP, starch concentrations were 22·5 and 273 g/kg DM and DUP levels were 44 and 60 g/kg DM respectively. Silages were offered ad libitum supplemented with 10 kg fresh concentrate per head per day. For silages А, В, С and D, DM intakes were 10.8, 11.2, 10·7 and 9·1 (s.e. 0·26) kg/day and milk yields 29.0, 27.6, 27.1 and 25.7 (s.e. 0.69) kg/day respectively. With the exception of milk protein concentration there were no significant (P> 0.05) silage type by concentrate energy source and/or level of DUP interactions on silage intake, milk output or composition. Concentrate energy source had no effect (P> 0.05) on silage DM intake, the yields of milk, fat, protein or fat plus protein or milk fat concentration. However, increasing starch concentration increased milk protein concentration (P< 0·001), urinary allantoin concentration (P< 0·01) and diet apparent digestibility (P< 0·001). Altering concentrate DUP level had no effect (P> 0·05) on silage DM intake, yields of milk, protein, fat or fat plus protein, milk f at concentrations or diet apparent digestibility. Increasing the level of DUP decreased milk protein (P< 0·05) concentration. It is concluded that with silages of varying digestibility, fermentation and intake characteristics, there were no concentrate energy source and/or level of DUP by silage type interactions on silage intake, milk yield or composition, or diet apparent digestibility with the exception of a silage type by concentrate level of DUP interaction on milk protein concentration. With out-of-parlour feeding of concentrates the results of the present study suggest that there is no evidence to justify the formulation of concentrates differing in energy source or level of DUP to complement individual silage types.

An examination of the effect of concentrate energy source on rumen fermentation characteristics of dairy cattle offered grass silages of differing intake characteristics

Recent dairy cow production studies (Keady et al, 1998a, b) have indicated that energy source (starch v fibre) in the concentrate did not alter silage intake or milk yield of lactating dairy cattle offered a range of grass silages. However in both studies increasing the level of starch in the concentrate increased milk protein concentration and tended to decrease milk fat concentration. The present study was undertaken to examine the effects of concentrate energy source on rumen fermentation characteristics of dairy cattle offered three grass silages.Three silages were produced from predominantly perennial ryegrass swards after 39 day regrowth intervals. Silages A and C were ensiled from primary regrowths treated with an inoculant while silage B was ensiled from a secondary regrowth untreated. Silage A was wilted for 24 hours prior to ensiling while silages B and C were ensiled direct. Two concentrates, 0s and 100s were formulated to contain different starch concentrations but similar concentrations of crude protein, metabolisable energy, digestible undegradable protein and effective rumen degradable protein.

The effects of concentrate energy source on silage feeding behaviour and energy utilization by lactating dairy cows offered grass silages with differing intake characteristics

The effects of concentrate energy source on feeding behaviour and energy utilization, when offered with grass silages of differing intake characteristics, were studied in lactating dairy cows. A total of five silages, which differed in fermentation and intake characteristics, were prepared. Silages A, B and D and silages C and E were harvested from primary regrowths and secondary regrowths respectively of predominantly perennial ryegrass swards. Herbage was ensiled either pre-wilted or unwilted and either untreated or treated with a bacterial inoculant or formic acid based additives. Five concentrates (0s, 25s, 50s, 75s and 100s) were formulated to contain similar concentrations of crude protein, effective rumen degradable protein and metabolizable energy (ME) but using different carbohydrate sources to achieve a wide range of starch concentrations. The silages were offered ad libitum, supplemented with 10 kg concentrates per head per day. In experiment 1, a partially balanced change-over design experiment involving 50 lactating dairy cows was undertaken to examine the effects of concentrate energy source on silage feeding behaviour. Silages A, B, C, D and E were each supplemented with concentrates Os, 25s, 50s, 75s and 100s. Concentrate energy source did not alter (P > 0·05) silage feeding behaviour. The number of meals per day decreased (P < 0·01) as silage dry-matter concentration increased. Experiment 2, a completely randomized experiment involving 18 lactating dairy cows, was undertaken to examine the effects of concentrate energy source on energy utilization with cows offered silages B, C and D. These were supplemented with 10 kg/day of concentrates Os, 50s and 100s. Concentrate energy source had little effect (P > 0·05) on ME intake, energy output or on the efficiency of utilization of ME for lactation (k1). In experiment 3, the effect of concentrate energy source on silage preference was examined in a factorial design experiment involving 12 lactating dairy cows. Silages B, C and D were supplemented with concentrates Os, 50s and 100s. Concentrate energy source did not alter (P > 0·05) silage preference. It is concluded that with silages of differing fermentation and intake characteristics but of similar digestibility, concentrate energy source had no effect on feeding behaviour, silage preference or energy utilization. Furthermore there was no evidence of concentrate energy source by silage type interactions on silage feeding behaviour and preference, or energy utilization.

The effects of concentrate energy source on silage intake and animal performance with lactating dairy cows offered a range of grass silages

A partially balanced change-over design experiment was made to examine the effects of concentrate energy source on the voluntary food intake and animal performance of 50 lactating dairy cows offered a diverse range of grass silages. The silages were also offered as the sole diet to 10 dairy cows in a partially balanced change-over design experiment. A total of five silages were prepared. Silages A, B and D and silages C and E were harvested from primary regrowths and secondary regrowths respectively of predominantly perennial ryegrass swards. Herbage was ensiled either pre-wilted or unwilted and either untreated or treated with a bacterial inoculant or formic acid based additives. For silages A, B, C, D and E, dry matter (DM) concentrations were 473, 334, 170, 170 and 256 (s.e. 4·0) g/kg, pH values 4·42, 4·01, 4·88, 4·46 and 3·91 (s.e. 0·059), ammonia-nitrogen (N) concentrations 86, 88, 289, 182 and 135 (s.e. 10·6) glkg total N and in vitro DM apparent digestibilities 0·76, 0·76, 0·75, 0·73 and 0·75 (s.e. 0·009) respectively. When offered as the sole diet DM intakes were 14·1,14·7,10·5,10·1 and 11·5 (s.e. 0·50) kg/day. Five concentrates were formulated to contain similar concentrations of crude protein, effective rumen degradable protein (ERDP), metabolizable energy (ME) and fermentable ME (FME) but using different carbohydrate sources to achieve a wide range of starch concentrations. For the low and high starch concentrates, starch concentrations were 50 and 384 g/kg DM, and acid-detergent fibre concentrations were 128 and 75 g/kg DM respectively. The silages were offeredad libitumsupplemented with 10 kg concentrate per head per day. For silages A, B, C, D and E silage DM intakes were 10·6, 10·5, 8·5, 8·6 and 9·0 (s.e. 0·37) kg/day and milk yields 23·9, 28·1, 26·2, 26·1 and 25·0 (s.e. 0·76) kg/day respectively. Concentrate energy source did not influence (P > 0·05) silage DM intake, diet apparent digestibility or the yields of milk or fat plus protein. For concentrates containing 50, 131, 209, 310 and 384 g starch per kg DM, milk protein concentrations were 32·0, 32·2, 32·5, 33·0 and 33·6 (s.e. 0·13) glkg, milk fat concentrations were 44·5, 43·9, 43·8, 43·3 and 43·1 (s.e. 0·35) glkg and urinary allantoin concentrations 15·2,15·4, 17·0, 1.7·6 and 18·0 mmolll respectively. Increasing starch intake resulted in positive and negative linear relationships for milk protein (P< 0·01, R2 = 0·96) and fat (P< 0·01, R2 = 0·96) concentrations respectively. There were no significant concentrate energy source × silage type interactions on silage intake or yields of milk or fat plus protein (P > 0·05). However there was a concentrate energy source × silage type interaction on milk fat yield (P > 0·05). It is concluded that, with silages of varying fermentation and intake characteristics but similar apparent digestibility, there were no concentrate energy source × silage type interactions on food intake, milk composition or milk yield. Also concentrate energy source had no effect on silage DM intake or milk yield. However increasing starch intake linearly increased milk protein concentration, probably due to increased microbial protein synthesis and decreased milk fat concentration.

The effects of concentrate composition on silage intake and feeding behaviour of lactating dairy cattle offered a range of grass silages differing in intake characteristics

A previous study at this Institute (Keady and Mayne, 1997) indicated that concentrate energy source did not alter silage intake or feeding behaviour of lactating dairy cattle offered one of a diverse range of grass silages differing in fermentation and intake characteristics, but of similar digestibility. Digestibility is the most important variable in grass silages at farm level and also has a considerable influence on silage intake. The aim of the present study was to examine the effects of concentrate energy source and effective rumen degradable protein (ERDP):digestible undegradable protein (DUP) ratio on silage intake and feeding behaviour of lactating dairy cows offered a range of grass silages differing in digestibility and intake characteristics.

The effects of concentrate composition on silage intake and feeding behaviour of lactating dairy cattle offered a range of grass silages differing in intake characteristics

A previous study at this Institute (Keady and Mayne, 1997) indicated that concentrate energy source did not alter silage intake or feeding behaviour of lactating dairy cattle offered one of a diverse range of grass silages differing in fermentation and intake characteristics, but of similar digestibility. Digestibility is the most important variable in grass silages at farm level and also has a considerable influence on silage intake. The aim of the present study was to examine the effects of concentrate energy source and effective rumen degradable protein (ERDP):digestible undegradable protein (DUP) ratio on silage intake and feeding behaviour of lactating dairy cows offered a range of grass silages differing in digestibility and intake characteristics.

An examination of the effect of concentrate energy source and changes in eRDP:DUP ratio on milk production of dairy cows offered grass silages differing in digestibility and intake characteristics

Results from a previous study at this Institute indicated that concentrate energy source did not alter silage intake or animal performance of lactating dairy cows offered a range of grass silages of similar digestibility but differing in intake characteristics. Digestibility is probably the single most important variable affecting animal performance from grass silage. The present study was undertaken to examine the effects of concentrate energy source and effective rumen degradable protein (eRDP):digestible undegradable protein (DUP) ratio in the concentrate on the silage intake of, and animal performance from, lactating dairy cows offered a diverse range of grass silages differing in digestibility and intake characteristics.

An examination of the effect of concentrate energy source on milk production of dairy cows offered grass silages with differing intake characteristics

Considerable progress has been made recently at this Institute in improving the accuracy of prediction of silage intake when offered as the sole diet. However in most farm situations, silage is usually supplemented with varying levels and types of concentrate when offered to dairy cattle. The aim of the present study was to examine the effects of concentrate energy source on the voluntary food intake and milk yield and composition of lactating dairy cattle when offered a diverse range of grass silages.A total of five grass silages were used in the study, silages A, B and D were produced from primary regrowths, while silages C and E were produced from second regrowths of perennial ryegrass swards. Silages A, B, C, D and E were ensiled after 48, 24, 0, 0 and 24 hour wilting periods. Silages A and C were ensiled untreated, B and D treated with an inoculant, and silage E treated with a formic acid based additive.