Physiological characteristics of high genetic merit and low genetic merit dairy cows: a comparison

1998 ◽  
Vol 1998 ◽  
pp. 4-4
Author(s):  
A. Sorensen ◽  
M. Alamer ◽  
C. H. Knight
Keyword(s):  
Dairy Cows ◽  
Research Effort ◽  
Genetic Selection ◽  
Plasma Samples ◽  
Major Research ◽  
Genetic Merit ◽  
Casting Technique ◽  
Biological Variables ◽  
Holstein Friesian ◽  
Key Enzyme

Genetic selection has greatly improved individual cow productivity. A high genetic merit Holstein Friesian cow will produce 10,000 of litres of milk in a 305 day lactation, those of lower genetic merit half this amount. Despite major research effort in generating these differences, quantitative biological description of what has been achieved is lacking. The aim of this study was to compare biological variables of relevance to milk synthesis in well defined high genetic merit and lower genetic merit dairy cows.12 cows of high genetic merit (HGM: top 5% of UK national herd) and 12 of lower genetic merit (LGM: close to UK average) were purchased from the Blythbank and Langhill herds; the ontogeny of these selection lines has been described elsewhere (Woolliams et al, 1993). Mean parity was 3.7±0.3 and was balanced between HGM and LGM. Management of the two groups was identical. Measurements were made over a period of two weeks close to peak lactation. Milk yield was recorded at each milking. Plasma samples were collected and analysed for a variety of hormones by radioimmunoassay and metabolites by established spectrophotometric assays. Udder size was determined by a casting technique (Dewhurst et al., 1993) and mammary biopsies for key enzyme activities were obtained as described by Knight et. al. (1992). Differences between lines were analysed by analysis of variance (ANOVA).

Physiological characteristics of high genetic merit and low genetic merit dairy cows: a comparison

1998 ◽  
Vol 1998 ◽  
pp. 4-4 ◽  
Author(s):  
A. Sorensen ◽  
M. Alamer ◽  
C. H. Knight
Keyword(s):  
Dairy Cows ◽  
Research Effort ◽  
Genetic Selection ◽  
Plasma Samples ◽  
Major Research ◽  
Genetic Merit ◽  
Casting Technique ◽  
Biological Variables ◽  
Holstein Friesian ◽  
Key Enzyme

Genetic selection has greatly improved individual cow productivity. A high genetic merit Holstein Friesian cow will produce 10,000 of litres of milk in a 305 day lactation, those of lower genetic merit half this amount. Despite major research effort in generating these differences, quantitative biological description of what has been achieved is lacking. The aim of this study was to compare biological variables of relevance to milk synthesis in well defined high genetic merit and lower genetic merit dairy cows.12 cows of high genetic merit (HGM: top 5% of UK national herd) and 12 of lower genetic merit (LGM: close to UK average) were purchased from the Blythbank and Langhill herds; the ontogeny of these selection lines has been described elsewhere (Woolliams et al, 1993). Mean parity was 3.7±0.3 and was balanced between HGM and LGM. Management of the two groups was identical. Measurements were made over a period of two weeks close to peak lactation. Milk yield was recorded at each milking. Plasma samples were collected and analysed for a variety of hormones by radioimmunoassay and metabolites by established spectrophotometric assays. Udder size was determined by a casting technique (Dewhurst et al., 1993) and mammary biopsies for key enzyme activities were obtained as described by Knight et. al. (1992). Differences between lines were analysed by analysis of variance (ANOVA).

The influence of cow genetic merit for milk production on response to level of concentrate supplementation in a grass based system

2003 ◽  
Vol 2003 ◽  
pp. 57-57 ◽  
Author(s):  
P. Dillon ◽  
J. Kennedy ◽  
P. Faverdin ◽  
L. Delaby ◽  
F. Buckley ◽  
...  
Keyword(s):  
Dairy Cows ◽  
Milk Production ◽  
Milk Yield ◽  
Yield Potential ◽  
Genetic Merit ◽  
Concentrate Supplementation ◽  
Holstein Friesian

Pre-1990 published responses to supplementation at pasture ranged from 0.4 to 0.6kg milk/kg concentrate fed. However since 1990 higher responses to concentrate supplementation at pasture have been published (Delaby 2001). The objective of this study was to determine if milk production responses of Holstein-Friesian dairy cows to concentrate supplementation at pasture are influenced by genetic merit (milk yield potential) in a spring calving grass based system of milk production.

The response by high genetic merit dairy cows to source and concentration of protein in the concentrate

1997 ◽  
Vol 1997 ◽  
pp. 90-90
Author(s):  
I.M. Carrick ◽  
D.C. Patterson ◽  
F.J. Gordon
Keyword(s):  
Dairy Cows ◽  
Crude Protein ◽  
Dairy Herd ◽  
Genetic Merit ◽  
Grass Silage ◽  
Holstein Friesian ◽  
Ruminant Diets ◽  
Feed Utilisation ◽  
Metabolisable Energy ◽  
Ad Libitum

Dairy cow genetic merit continues to increase in the dairy herd. These animals require a higher level of nutritional input than lower genetic merit cows if higher performance levels are to be sustained. The high cost of ingredients for ruminant diets highlights the need for greater precision in ration formulation in order to improve the efficiency of feed utilisation. This experiment was carried out to assess the effect of DUP supplementation on the performance of dairy cows with ad libitum access to grass silage.An experiment was conducted to investigate the response by high genetic merit Holstein Friesian dairy cows (PTA90 fat plus protein = 61 kg) to both source and concentration of protein in the concentrate, given in addition to ad libitum grass silage (metabolisable energy (ME) = 10.9 MJ/kg DM; crude protein (CP) = 166 g/kg DM). Twenty-four cows, including 12 first parity animals (mean days calved 37.5, s.d. 22.3), were blocked according to milk yield, calving date and parity. The experimental design was a balanced changeover with four 4-week periods.

Consequences for immune function of metabolic adaptations to load

1999 ◽  
Vol 24 ◽  
pp. 113-118 ◽  
Author(s):  
M. C. Sinclair ◽  
B. L. Nielsen ◽  
J. D. Oldham ◽  
H. W. Reid
Keyword(s):  
Antibody Response ◽  
Immune Function ◽  
Dairy Cows ◽  
Genetic Selection ◽  
Test Sample ◽  
Protein Yield ◽  
Selection Line ◽  
Control Line ◽  
Genetic Merit ◽  
One Year

AbstractProlonged periods of stress have been associated with impaired immune function; the experiment reported here investigates a potential link between level of metabolic load and immune function in lactating dairy cattle. A group of 111 Holstein-Friesian dairy cows was used. The cows belonged to one of two genetic lines: a selection line (S) with high genetic merit for fat plus protein yield and an unselected control line (C). The cows were offered one of two silage-based total mixed diets containing either 200 g (LC) or 450 g (HC) of concentrate per kg dry matter. Combination of genetic selection and food gave four groups: S-LC, S-HC, C-LC and C-HC. All cows were inoculated with a live attenuated BHV-1 vaccine soon after parturition and the primary antibody response in whey monitored. The number of BHV-1 antibody positive cows was not significantly different between the four groups; but, the initial antibody response was lower in cows of high genetic merit which were given a low concentrate diet. Statistical analysis demonstrated that the contribution of diet to this effect was highly significant. One year later, again after parturition, the experiment was repeated, this time using serum as the test sample. The average antibody response of the BHV-1 antibody positive cows was not significantly different between the four groups but the number of antibody positive cows was group-dependent. In conclusion, diet type but not genetic merit for high fat plus protein yield made a highly significant contribution to the antibody response of dairy cows to BHV-1 vaccination, both initially and a year later.

An examination of the metabolizable energy requirements of lactating dairy cows

1998 ◽  
Vol 1998 ◽  
pp. 197-197 ◽  
Author(s):  
S.B. Cammell ◽  
M.S. Dhanoa ◽  
D.E. Beever ◽  
J.D. Sutton ◽  
J. France
Keyword(s):  
Dairy Cows ◽  
Animal Studies ◽  
Research Effort ◽  
Metabolizable Energy ◽  
Energy Requirements ◽  
Mathematical Treatment ◽  
Lactating Dairy Cows ◽  
Holstein Friesian ◽  
The Uk ◽  
Friesian Cows

The last 4 decades has seen considerable research effort directed towards quantifying the energy requirements of dairy cows. The partitioning of food energy and the efficiencies with which it is used for maintenance (km) and milk production (kl) have been subjected to scrutiny through either individual animal studies or mathematical treatment of data pools, and in consequence several rationing systems have been proposed. Since 1992, CEDAR has undertaken research involving a series of rations fed to lactating Holstein-Friesian cows where energy and nitrogen balances have been conducted simultaneous with gaseous exchange. The purpose of this study was to consider this data in order to establish if either the cows or diets currently being used in the UK have any effect on maintenance metabolizable energy [ME] requirements or the efficiency with which ME is utilised to support milk synthesis.

scholarly journals Effect of Genetic Merit and Concentrate Supplementation on Grass Intake and Milk Production with Holstein Friesian Dairy Cows

2003 ◽  
Vol 86 (2) ◽  
pp. 610-621 ◽  
Author(s):  
J. Kennedy ◽  
P. Dillon ◽  
L. Delaby ◽  
P. Faverdin ◽  
G. Stakelum ◽  
...  
Keyword(s):  
Dairy Cows ◽  
Milk Production ◽  
Genetic Merit ◽  
Concentrate Supplementation ◽  
Holstein Friesian

The weight and concentration of body components in high genetic merit Holstein-Friesian dairy cows managed on four different grassland-based feeding regimes

2005 ◽  
Vol 81 (1) ◽  
pp. 179-184 ◽  
Author(s):  
V. B. Woods ◽  
C. P. Ferris ◽  
F. J. Gordon
Keyword(s):  
Dairy Cows ◽  
Milk Production ◽  
Body Tissue ◽  
Genetic Merit ◽  
Holstein Friesian ◽  
Feeding Regimes ◽  
Body Components ◽  
Cow Performance ◽  
Direct Measures ◽  
Effect Of Feeding

AbstractIt is well established that the genetic merit of the Holstein-Friesian dairy cow for milk production has increased over the past 20 years. Previous studies have examined the effect of feeding system on indices of body tissue reserves of medium genetic merit Holstein-Friesian dairy cows. The aim of the current study was to examine the weight and concentration of body components in high genetic merit Holstein-Friesian dairy cows, managed on four different grassland-based feeding regimes, using direct measures of body composition. Results indicate that there was no significant effect of different grassland-based feeding regimes on the weight or composition of body components of high genetic merit cows. Therefore, high levels of cow performance can be sustained from very different grassland-based systems of milk production without having a detrimental effect on body tissue reserves.

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