Lactating Holstein Heifers Research Articles

Genetic analysis of subclinical mastitis in early lactation of heifers using both linear and threshold models

Subclinical mastitis (SCM) causes economic losses for dairy producers by reducing milk production and leading to higher incidence of clinical mastitis and premature culling. The prevalence of SCM in first-lactation heifers is highest during early lactation. The objective of this study was to estimate genetic parameters for SCM in early lactation in first-parity Holsteins. Somatic cell count test-day records were collected monthly in 91 Canadian herds participating in the National Cohort of Dairy Farms of the Canadian Bovine Mastitis Research Network. Only the first test-day record available between 5 and 30 d in milk was considered for analysis. The final data set contained 8,518 records from first lactation Holstein heifers. Six alternative traits were defined as indicators of SCM, using various cutoff values of SCC, ranging from 150,000 to 400,000 cells/mL. Both linear and threshold animal models were used. Overall prevalence of SCM using the 6 traits ranged from 13 to 24%. Heritability estimates (standard error) from linear and threshold models ranged from 0.037 to 0.057 (0.015 to 0.018) and from 0.040 to 0.051 (0.017 to 0.020), respectively. We found strong genetic correlations (standard error) among alternative SCC traits, ranging from 0.90 to 0.99 (0.013 to 0.069), indicating that these 6 traits were genetically similar. Despite low heritability, based on estimated breeding values (EBV) predicted from both models, we noted exploitable genetic variation among sires. Higher EBV of SCM resistance corresponded to sires with a higher percentage of daughters without SCM. Based on a linear model (all 6 traits), percentage of daughters with SCM ranged from 5 to 13% and from 19 to 33% for the top 10% and worst 10% of 69 sires with minimum 20 daughters in at least 5 herds, respectively. Spearman's rank correlations among EBV of sires predicted from linear (from 0.75 to 0.95) and threshold (from 0.74 to 0.95) models were moderate to high, respectively. Very high rank correlations (0.98 to 0.99) between EBV predicted for the same trait from linear and threshold model indicated that reranking of sires based on model used was minimal. In conclusion, despite low heritability, we found utilizable genetic variation in early lactation of heifers. Hence, genetic selection to improve genetic resistance to SCM in early lactation of heifers was deemed possible.

Effects of housing and intake of methionine on the growth and wear of hoof horn and the conformation of the hooves of first-lactation Holstein heifers

This study investigated the effects of housing primiparous lactating Holstein heifers either in cubicles with butyl rubber mats, cubicles with thicker mattresses filled with chopped rubber, or straw yards, and...

Hock injuries in cattle kept in straw yards or cubicles with rubber mats or mattresses

Hock damage is one of the most common traumatic injuries suffered by dairy cows, but most hock injuries should be avoidable. This study investigated the effect of housing system on...

The effect of whole cottonseed and processing of canola on the milk production and composition of first lactation Holstein heifers

Extracted from text ... The effect of whole cottonseed and processing of canola on the milk production andcomposition of first lactation Holstein heifersL.J. Erasmus 1# , P.C. Haasbroek 1 and J.B.J. van Ryssen 21 Agricultural Research Council ? ANPI, Private Bag X2, Irene, 00622 Dept Animal and Wildlife Sciences, University of Pretoria, Pretoria, 0001# e-mail:lourens@idpi1.agric.zaIntroductionThe use of whole oilseeds such as whole cottonseed (WCS) to increase the energy density of dairy cattlediets is common practice today. Research has shown that certain varieties of canola (previously called rapeseed)are well adapted to the Western Cape and the area planted is expanding fast. Canola has a similar ..

Genetic Evaluation of Body Weight of Lactating Holstein Heifers Using Body Measurements and Conformation Traits

Genetic and phenotypic parameters of body weight (BW), hip height, heart girth, and linear conformation traits were estimated from field data for 7344 lactating Holstein heifers from 560 herds. Mean BW was around 540kg at calving, decreased to a minimum of 514kg by wk 6, and increased to >590kg by wk 45 of lactation. The statistical model for BW included month of recording, lactation stage, pregnancy stage, proportion of Holstein genes, parity of the dam, calving age, herd, and animal. Variation between herds accounted for 33% of the phenotypic variation of BW. Estimated heritability was 0.33 for BW and ranged from 0.32 to 0.54 for heart girth, hip height, and conformation traits. Genetic correlations of BW with heart girth, hip height, body depth, rump width, and muscularity ranged from 0.48 to 0.77. The accuracy of a selection index was 0.90 for direct selection and 0.83 for indirect selection using information on those conformation traits of 50 daughters. Genetic variation of BW is considerable, and genetic evaluation of BW can be based on data for conformation traits from a field recording system with only a limited loss of accuracy.

Degradabilidade ruminal de alimentos em vacas secas e lactantes, recebendo 70% ou 50% de MS das rações como volumosos

Oito novilhas holandesas, quatro secas e quatro em lactacao, receberam os seguintes tratamentos, visando medir degradabilidade ruminal dos alimentos, farelo de soja, farelo de arroz, feno coast cross e cana-de-acucar, pelo processo de sacos de nailon in situ: A - 70% de volumosos; vacas secas; B - 70% de volumosos; vacas em lactacao; C - 50% de volumosos, vacas secas e D - 50% de volumosos, vacas em lactacao. O delineamento foi em blocos ao acaso e os tratamentos foram aplicados em quatro periodos consecutivos. Vacas secas degradaram melhor farelo de soja, feno coast cross e cana-de-acucar que as em lactacao. As femeas lactantes consumiram 40% mais materia seca que as nao- lactantes e apresentaram maior turn-over do liquido ruminal. Os alimentos feno de coast cross e cana-de-acucar foram melhor degradados nas dietas com 70% de volumosos em relacao as com 50%.

Hepatic lipidosis in anorectic, lactating holstein cattle: a retrospective study of serum biochemical abnormalities.

The association between hepatic lipidosis (HL) and disease in 59 anorectic, ketotic, lactating Holstein heifers and cows was investigated. Severe HL, as determined by histologic evaluation of liver tissue, was present in 46 animals; only half of these animals required intensive treatment for ketosis, and only half had serum biochemical evidence of liver disease, as determined by the presence of a last value of 2-fold or greater than the upper limit of the reference ranges for at least 2 of the 4 serum tests: gamma-glutamyl transferase, aspartate aminotransferase, and sorbitol dehydrogenase activities and bile acid concentrations. Most cattle with biochemical evidence of liver disease and severe HL had been lactating for 14 or more days. Cows that required intensive treatment inconsistently had serum biochemical evidence of liver disease. Although cattle with severe HL had significantly higher serum bilirubin concentrations and aspartate aminotransferase and sorbitol dehydrogenase activities than cattle with less severe lipidosis, the specificity of abnormally high serum sorbitol dehydrogenase activity or bilirubin concentration for severe lipidosis was only 8%. Abnormally high serum aspartate aminotransferase activity was 83% sensitive and 62% specific for severe lipidosis. Serum glucose and total carbon dioxide concentrations were significantly lower in cattle with severe lipidosis than in those with mild or moderate lipidosis, and low serum glucose or total carbon dioxide concentrations were rare in cattle without severe lipidosis. From these data, we conclude that the use of a single biochemical or histopathologic criterion to define severity of disease or degree of liver compromise in anorectic, ketotic cows results in the misidentification of many animals.

Comparison of daughters of Canadian and New Zealand Holstein sires for first lactation efficiency of production in relation to body size and condition

Sixty-five first lactation Holstein heifers, 31 sired by one of 19 top Canadian AI proven sires and 34 sired by one of 19 top New Zealand AI proven sires were compared for production, feed intake, energetic efficiency, body weight and condition. Heifers were fed free choice a high-, medium- and low-energy complete feed for the first 140 d, 141–240 d and 241–305 d of lactation, respectively. The Canadian-sired heifers averaged 6097 ± 177 kg, 231 ± 6 kg, 226 ± 6 kg and 310 ± 9 kg of milk, fat protein, and lactose while the New Zealand sired heifers produced 5469 ± 169 kg, 226 ± 6 kg, 189 ± 6 kg and 273 ± 9 kg. Net energy consumption and gross energy production of the Canadian-sired heifers was 7783 Mcal and 4515 Mcal, and for New Zealand-sired heifers was 7310 Mcal and 4248 Mcal, resulting in feed efficiencies of 0.59 ± 0.01 and 0.58 ± 0.01 for Canadian- and New Zealand-sired heifers. Feed efficiencies, body weight gain and change in body condition score from week 2 of lactation to the end of lactation did not differ significantly between the Canadian- and New Zealand-sired heifers. Canadian-sired heifers had a lower body condition score (P < 0.05) than their New Zealand-sired counterparts in early lactation. Canadian-sired Holsteins had, on average, 7.4% higher returns per lactation with Ontario milk prices and 2.2% higher returns under New Zealand milk pricing, but neither difference was statistically significant. Key words: Strain comparison, energetic efficiency, dairy cow

Teat stimulation-induced oxytocin and catecholamine release in pregnant and lactating holstein heifers

The effect of manual teat stimulation (milking paradigm) on release of oxytocin, epinephrine and norepinephrine was studied in (1) 15 heifers at 100, 150, 200 and 250 d of gestation and at 30 and 90 d of lactation (during machine milking) and (2) simultaneously in six heifers at <100 d and in six heifers at >200 d of gestation. Oxytocin responses to teat stimulation, including peak heights and area under the response curves, at 150, 200 and 250 d or at >200 d of gestation were similar and were significantly greater than responses at 100 d or at <100 d. Responses to milking were lower at 90 d compared to responses at 30 d. Catecholamines were measured only during gestation and were generally not affected by teat stimulation. Epinephrine levels were significantly higher at 200 and 250 d compared to levels at 100 and 150 d. Baseline oxytocin concentrations and responses to teat stimulation were greatest at 150 d of gestation when epinephrine levels were still low, suggesting that stimulatory mechanisms responsible for the release of oxytocin develop and/or are expressed prior to the development of inhibitory sympathetic mechanisms. For norepinephrine, linear analyses did not show significant responses to teat stimulation overall. However, elevated norepinephrine responses (>.2 pmol/ml) following teat stimulation were seen in 28 of 51 trials, and large oxytocin responses (>75 pg/ml/min) were seen predominantly only when norepinephrine responses were low (<=.2 pmol/ml).

Regulation of Bovine Adipose Tissue Metabolism During Lactation. 5. Relationships of Lipid Synthesis and Lipolysis with Energy Intake and Utilization1,2

The effects of energy utilization during lactation on adipose tissue metabolism were determined in 51 first lactation Holstein heifers producing between 5950 and 10,246kg milk in 305 d. Net energy intake ranged from 18.3 to 40.6 Mcal/d during 28 to 140 d of lactation. Milk yield ranged from 13.5 to 47.4 kg/d and fat percent from 1.49 to 4.60 during 28 to 140 d, providing a range of 8.2 to 32.6 Mcal/d milk energy secretion. Calculated energy balance ranged from −16.4 to 11.5 Mcal/d. Weight change ranged from −70 to 143kg during that 112-d period. Subcutaneous adipose tissue was biopsied nine times from 30 d prepartum to 15 d after lactation ceased. Adipose lipid synthesis measured prepartum was negatively related to subsequent milk energy secretion. Net energy intake, body weight, and body weight change were related positively to adipose lipid synthesis rates from 28 to 56 d, but those rates were related negatively to milk energy secretion. Lipolysis was positively related to milk energy secretion and body weight and negatively related to NE intake. At d 60 of lactation, adipose tissue lipid synthesis rates were a function of body weight, weight gain, and net energy intake. However, catecholamine-stimulated lipolysis rates were a function of body weight and milk energy secretion. After 140 d, lipid synthesis and lipolysis were elevated and more closely related to the previous peak rather than to concomitant milk energy secretion. These relationships demonstrate the effects of dietary energy content and genetic selection for milk production on adipose tissue metabolism.

Influence of Variations in Ruminal Contents upon Estimates of Body Weight Change of Dairy Cattle during Restricted Feeding

Three common methods of estimating live weight change in ruminants and relationships between ruminal contents and live weights of dairy cattle were studied, using 13 lactating Holstein heifers, two with rumen fistulas. Live weights were obtained immediately after each milking for 105 consecutive days in one trial and 61 days in another. Ruminal contents from fistulated heifers were removed, weighed, sampled, and replaced periodically. Body weight changes estimated from single weighings after 14 hr without feed or water at the beginning and end of a period were shown to be more accurate than changes estimated either from means of three live weights taken at the beginning and end of a period, or from a regression of daily live weights on time. It was shown that estimation of body weight change from shrunk live weights could greatly reduce variations in ruminal fill, one of the largest sources of error in dairy cattle feeding experiments.