Direct and Correlated Responses to Selection for Milk Yield: Results and Conclusions of Regional Project NC-2, “Improvement of Dairy Cattle through Breeding, with Emphasis on Selection”

Kelm, S.C.; Freeman, A.E.

doi:10.3168/jds.s0022-0302(00)75166-6

Cited by 27 publications

(27 citation statements)

References 26 publications

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“…In addition, selection for higher milk production has also Abbreviations: AUC = area under the curve for bacterial counts in milk in time, BCT = bacterial clearance time (< 1 cfu/mL), RMP = residual milk production (% of pre-infusion baseline in the three noninfused quarters); HP = high producing, LP = low producing, -c = fed according to requirements during the dry period, -o = overfed during the dry period. been a selection on a faster milk flow [11], which, together with increased mechanical pressure due to large volumes of milk, may cause increased leaking of milk in high producing cows [10]. The latter is associated with an increased risk of clinical mastitis [21].…”

Section: Discussionmentioning

confidence: 99%

The effect of milk production level on host resistance of dairy cows, as assessed by the severity of experimental Escherichia coli mastitis

et al. 2003

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-This study investigated the possible effects of milk production level on the host resistance of dairy cows. High (n = 18) and low (n = 18) producing cows on a research farm, which respectively produced 11 443 and 7 727 kg milk in their previous lactation, were compared. To enhance the possible differences in host resistance between high and low producing cows, the animals in both groups were metabolically stressed by overfeeding during the dry period or were fed according to requirements, resulting in four groups of nine cows. The metabolic status was monitored from two weeks pre-partum until 2.5-4.5 weeks post-partum. Host resistance was assessed by measuring the severity of experimentally induced Escherichia coli mastitis. Pre-partum blood glucose levels tended to be higher in overfed cows than in cows fed according to requirements. The post-partum energy balance was significantly more negative in high producing cows than in low producers, and tended to be more negative in overfed cows compared to cows fed according to the requirements. Post-partum plasma glucose, NEFA, β-OH-butyrate and urea concentrations were similar in the four groups. Plasma glucose concentrations were significantly lower and liver triacylglycerol concentrations were significantly higher in third than in second parity cows. Host resistance was not affected by the production level or feeding regimen. There were no significant correlations between the metabolic status and the severity of experimental E. coli mastitis, except for the relatively more severe mastitis in the cows with β-OH-butyrate concentrations above 1.4 mmol/L. In conclusion, milk production level did not affect host resistance in dairy cows, as measured by the severity of experimental E. coli mastitis. Even in a situation where cows were metabolically stressed by overfeeding, high producers were as able as low producers to cope with the demands of milk production, without consequences for host resistance. dairy cow / milk production / host resistance / metabolism / E. coli mastitis * Corresponding author: j.e.kornalijnslijper@vet.uu.nl 722 E. Kornalijnslijper et al.

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Section: Discussionmentioning

confidence: 99%

The effect of milk production level on host resistance of dairy cows, as assessed by the severity of experimental Escherichia coli mastitis

et al. 2003

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“…Wautlet et al (1990) reported no significant difference between the lines for udder edema, dystocia, and retained placenta in first-lactation cows. The regional project NC-2 also measured direct and correlated responses to single-trait selection for milk yield at various research stations (Kelm et al, 2000). The NC-2 project found selection for milk yield was effective for increasing milk production in selected lines compared with control lines (Kelm et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

“…The regional project NC-2 also measured direct and correlated responses to single-trait selection for milk yield at various research stations (Kelm et al, 2000). The NC-2 project found selection for milk yield was effective for increasing milk production in selected lines compared with control lines (Kelm et al, 2000). The project also reported that selection for milk yield caused delayed estrus and increased health problems and costs; however, there was an increase of net income per lactation in the NC-2 project herds (Kelm et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

“…Boettcher et al (1993) reported that cows selected for milk yield in the University of Minnesota experimental herd had significantly higher EBV for stature, body depth, angularity, rump width, leg set, rear-udder height and width, udder support, and udder depth than a control line. The NC-2 project reported that linear type traits in selected lines for increased milk yield did not drastically deteriorate compared with control lines; however, selected lines had cows with udders that were wider, longer, and slightly deeper (Kelm et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

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Genetic Parameters and Responses of Linear Type, Yield Traits, and Somatic Cell Scores to Divergent Selection for Predicted Transmitting Ability for Type in Holsteins

Degroot¹,

Keown²,

Vleck³

et al. 2002

Journal of Dairy Science

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The objective was to examine the direct and correlated responses of linear type, yield traits, and somatic cell scores (SCS) to divergent selection for predicted transmitting ability for type (PTAT) in Holsteins, while maintaining selection for yield traits across lines. For four generations, one-half of the University of Nebraska research Holstein herd was bred to Holstein sires with PTAT > 1.50 and the other half to sires with PTAT < 1.25, with nearly equal predicted transmitting abilities for yield traits for both groups. Estimates of genetic and residual correlations and heritabilities were obtained from REML estimates of (co)variance components. Model for type traits included fixed effect of date cows were classified, effects of age in days at freshening, and stage of lactation at classification. Year-season when cows freshened was fixed effect in model for yield and SCS. Animal genetic and residual effects were random. Final score, milk, fat, and protein yields, and SCS had heritability estimates of 0.38, 0.13, 0.22, 0.09, and 0.38, respectively. Heritability estimates for type traits ranged from 0.04 to 0.52. Estimates of genetic correlations of final score with SCS and milk, fat, and protein yields were −0.64, 0.01, −0.18, and 0.06, respectively. Estimates of genetic correlations among linear type traits ranged from −0.77 to 1.00. Means of estimated breeding values for final score, stature, strength, body depth, fore udder attachment, rear udder height and width, udder cleft, udder depth, and front teat placement were significantly different between lines in the third generation. Milk, fat, and protein yields were not significantly different between lines in third generation, whereas SCS was significantly different. Estimate of genetic correlation between final score and SCS sug-

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“…Artificial selection has resulted in livestock species that are typically more productive and (or) efficient than their ancestors (Wilson and Willham, 1986;Kelm et al, 2000;Chen et al, 2003). That is, modern livestock yield more output per head than did their predecessors.…”

Section: Introductionmentioning

confidence: 99%

Invited review: Genomic analysis of data from physiological studies

Garrick

Baumgard

Neibergs

2012

Journal of Dairy Science

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Physiology deals with the functions of living organisms and their systems, and its scientific endeavors can be viewed as having temporally occurred in 3 phases. The first phase of physiology studies focused on determining the functions of particular organs and tissues and their functional differences according to physiological status. The second phase of studies focused on characterizing differences in these functions according to the environment, or productivity. The third phase of studies focuses on determining the physiological causes of differences in productivity. Distinguishing cause from effect in physiological systems of inter-related processes is problematic, such that science has struggled to identify the root physiological mechanisms and their role in the network of genes leading to differences in productivity. Genomics is the study of the entire genome and provides powerful new tools that will accelerate third-phase discoveries of causal physiological processes. That research exploits information on DNA polymorphisms known as markers, complete DNA sequence, RNA sequence, and RNA expression in particular tissues at specific life stages. Physiologists can determine the genetic cause of mutant animals, identify genetic differences between cases and controls, and identify genes responsible for differences in performance between average and above-average animals. In some species, physiologists can leverage genomic data being used to predict genetic merit in elite seedstock populations, as a starting point to identify genes that will then motivate detailed physiological studies in the organs or tissues and stages of life in which those genes are expressed. Such work will increase our knowledge of biology and may lead to novel approaches to manipulate animal performance.

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Direct and Correlated Responses to Selection for Milk Yield: Results and Conclusions of Regional Project NC-2, “Improvement of Dairy Cattle through Breeding, with Emphasis on Selection”

Cited by 27 publications

References 26 publications

The effect of milk production level on host resistance of dairy cows, as assessed by the severity of experimental Escherichia coli mastitis

The effect of milk production level on host resistance of dairy cows, as assessed by the severity of experimental Escherichia coli mastitis

Genetic Parameters and Responses of Linear Type, Yield Traits, and Somatic Cell Scores to Divergent Selection for Predicted Transmitting Ability for Type in Holsteins

Invited review: Genomic analysis of data from physiological studies

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