Levels of pasture substitution when concentrates are fed to grazing dairy cows in northern Victoria

2000 ◽  
Vol 40 (7) ◽  
pp. 913 ◽  
Author(s):  
C. R. Stockdale
Keyword(s):  
Dairy Cows ◽  
Milk Production ◽  
Body Condition ◽  
Background Information ◽  
Feeding Strategies ◽  
Paspalum Dilatatum ◽  
Regression Relationship ◽  
Key Variables ◽  
Grazing Dairy Cows ◽  
Marginal Returns

This paper aims to provide information for farmers and their advisers to predict levels of substitution that might be occurring under various feeding conditions in northern Victoria. The approach taken involved compiling data from research conducted in northern Victoria and subjecting these to multiple regression analysis to define the key variables affecting substitution and marginal responses in milk production when concentrates are fed. A significant relationship was obtained between level of substitution (kg DM reduction in pasture intake/kg DM of concentrates eaten) and unsupplemented pasture intake (PI, kg DM/100 kg liveweight) when concentrates are fed. The regression relationship also included species composition of the sward being grazed (species: +1 grass, 0 clover), season of the year (season: +1 spring, 0 summer, –1 autumn) and concentrate intake (kg DM/cow.day). The equation is: Substitution = –0.34 + 0.16 ( 0.035) PI + 0.16 ( 0.053) species + 0.11 ( 0.024) season+ 0.03 ( 0.014) concentrate intake [100R 2 = 50.9 (P<0.01); r.s.d. = 0.14; CV = 37.7%]. Substitution increased by 0.16 kg DM/kg DM for each increment of pasture intake. At any pasture intake, grass-dominant pastures, regardless of whether the grass was perennial ryegrass (Lolium perenne) or paspalum (Paspalum dilatatum), resulted in 0.16 kg DM/kg DM more substitution than white clover (Trifolium repens)-dominant pastures. In addition, substitution was 0.11 kg DM/kg DM higher in spring than in summer, and 0.11 kg DM/kg DM higher in summer than in autumn. Finally, substitution increased by 0.03 kg DM/kg DM for each additional kg DM of concentrates offered. Marginal returns in milk production (MR, kg extra milk/kg DM of concentrates eaten) were negatively related to substitution according to the following regression equation: MR = 2.62 – 0.80 ( 0.216) substitution – 0.28 ( 0.084) season – 0.34 ( 0.086) body condition[100R2 = 62.9 (P<0.01); r.s.d. = 0.23; CV = 29.6%]. Marginal responses were 0.28 kg/kg DM lower in spring than in summer and autumn (season: +1 spring, 0 summer–autumn), and each unit improvement in body condition reduced expected marginal returns by 0.34 kg/kg DM. These relationships, together with those developed to aid estimates of unsupplemented pasture intake, can be used as background information in decision support systems to help farmers and their advisers make more informed decisions about feeding strategies when supplements are fed than has hitherto been possible.duct

Effect of length of the period of supplementation with concentrates on pasture intake and performance of grazing dairy cows

1999 ◽  
Vol 39 (7) ◽  
pp. 803 ◽  
Author(s):  
C. R. Stockdale
Keyword(s):  
Dairy Cows ◽  
Body Condition ◽  
Body Condition Score ◽  
The Body ◽  
The Other ◽  
Continuous Treatment ◽  
Short Term ◽  
Grazing Dairy Cows ◽  
Marginal Returns

Summary. The hypothesis tested in the experiment reported here was that levels of substitution would be lower and marginal responses to supplementation higher in grazing dairy cows that were subjected to long, compared with short, treatment periods. Forty cows were fed irrigated perennial pasture which contained ryegrass (Lolium perenne), white clover (Trifolium repens), paspalum (Paspalum dilatatum) and weeds at a herbage allowance of about 40 kg dry matter (DM)/cow.day. Of the 40 cows, 20 were under continuous treatment for 6 months (2 October 1995 to 24 March 1996, inclusive) (long term), while treatments were applied to the remaining 20 cows every second month (short term). The second group of cows, therefore, commenced 4 weeks of treatment on 3 occasions, 31 October, 1 January and 26 February. The cows in the short-term treatments were re-randomised for each of their 3 periods in the experiment. There were 2 long-term treatments, one where pasture was fed alone and the other where the same amount of pasture was supplemented with 5 kg DM/cow.day of a 75% barley –25% wheat grain pellet. There were 2 replicates of each treatment and 5 cows per group. The second set of 20 cows was allocated to the same treatments on a short-term basis. When not under treatment, all cows in this second group were offered about 40 kg DM of pasture/cow.day plus 5 kg DM of barley–wheat. Cows ate less pasture when concentrates were fed although total DM intake increased (P<0.05). The level of substitution averaged 0.4 kg DM reduction in pasture intake for each kg DM of concentrates consumed, and this was not affected (P>0.05) by the length of time for which the cows were supplemented. Milk yield declined from November to March and concentrates increased production, but the interaction between period of the year and use of supplements was not significant (P>0.05). However, the milk responses associated with length of time under supplementation appeared to be different in March relative to the other periods. Although the marginal returns to concentrates in March were 0.9 and 1.3 kg milk/kg DM for short- and long-term supplementation, the marginal returns to feeding concentrates for short or long periods during November and January were the same (0.9 kg/kg DM). However, in terms of total DM intake, the average marginal response was lower (1.4 v. 1.9 kg milk/kg of additional total DM) for the short-term treatments. The trends in body condition for the long-term treatments through the experiment indicated that divergence between unsupplemented and supplemented cows occurred consistently throughout, resulting in 0.8 units difference in body condition score after the 6 months of treatment. It is suggested that it was the differences in body condition that were responsible for the variation in milk response towards the end of the experiment. It was concluded that, while the length of time under supplementation had no effect on intake variables or substitution, marginal responses to the long term use of concentrates eventually diverged from those obtained from their use for short periods, principally due to changes in the body condition of animals in the long-term treatments.

Differences in body condition and body size affect the responses of grazing dairy cows to high-energy supplements in early lactation

2000 ◽  
Vol 40 (7) ◽  
pp. 903 ◽  
Author(s):  
C. R. Stockdale
Keyword(s):  
Body Size ◽  
Dairy Cows ◽  
Protein Content ◽  
Milk Production ◽  
Body Condition ◽  
High Energy ◽  
High Body ◽  
Urea Content ◽  
Milk Urea ◽  
Grazing Dairy Cows

Two experiments of 5-weeks duration, using Friesian cows, were conducted at the Kyabram Dairy Centre during September–October (experiment 1) and November–December (experiment 2), 1998. The aim of the research was to determine whether the level of substitution with the feeding of concentrates to grazing dairy cows would be increased by thinner body condition (3.4 v. 5.2 units) and by larger body size (618 v. 486 kg) because both these factors would be expected to increase the level of unsupplemented pasture intake. In both experiments, there were 2 pasture allowances (targets of 25 and 50 kg DM/cow. day) and 2 weeks of supplement (0 and 5 kg DM/cow. day). In experiment 1, pasture intake increased significantly (P<0.05) with the increase in pasture allowance and decreased with supplementation. Levels of substitution averaged 0.56 and 0.47 kg DM/kg DM when concentrates were fed to cows with low and high body condition, respectively. However, variation in the data meant that body condition did not have a significant (P>0.05) influence on the positive relationship between substitution and unsupplemented pasture intake. The only effects of body condition on animal production were that the high body condition cows produced milk with a higher fat content, and they lost more body condition, than the low body condition cows (P<0.05). The increase in pasture allowance significantly (P<0.05) increased milk production and milk urea content, and decreased the loss in body condition. Feeding concentrates significantly (P<0.05) increased milk production and prevented any losses in body condition, but milk urea content declined with supplementation. In experiment 2, heavy cows ate more pasture than light cows (P<0.05), and increasing the pasture allowance increased pasture intake while providing cows with concentrates reduced pasture intake (P<0.05). When substitution was considered relative to unsupplemented pasture intake (kg DM/cow.day), light cows exhibited significantly (P<0.05) more substitution than heavy cows, but when pasture intake was expressed as a percentage of liveweight, there were no significant (P>0.05) differences in substitution between light and heavy cows at common intakes. Heavy cows produced more (P<0.05) milk with a lower protein content than light cows. Increasing the pasture allowance and supplementation with concentrates both significantly (P<0.05) increased milk production and milk protein content, while the higher pasture allowance reduced body condition loss and supplementation increased (P<0.05) liveweight. Feed conversion efficiencies were the same for light and heavy cows, at 1.68 kg FCM/kg DM of total intake in both cases. The hypothesis that substitution would increase as intake increased was supported by the results obtained for both body condition and body size, since body condition affected neither intake nor substitution while liveweight influenced both.

The effects of level of winter feeding and buffer-feeding during the grazing season on the milk production of January/February calving dairy cows.

1997 ◽  
Vol 1987 ◽  
pp. 29-29
Author(s):  
C.S. Mayne ◽  
S.C.P. Woodcock ◽  
A.J. Clements
Keyword(s):  
Dairy Cows ◽  
Milk Production ◽  
Animal Performance ◽  
High Animal ◽  
Grazing Season ◽  
Grazing Dairy Cows ◽  
Winter Feeding

Buffer-feeding of grazing dairy cows, by allowing cows access to forage for a few hours each day, has been widely advocated as a means of maintaining high animal performance whilst enabling efficient sward utilization. However, in practice, responses to buffer-feeding with January/February calving cows have been extremely variable. The objective of this study was to examine if part of the variability in response could be explained by differences in the level of nutrition during the winter feed period.

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