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PubMed1989

The effects of dietary fat or fiber addition on yield and composition of milk from sows housed in a warm or hot environment.

Sixty sows were individually penned in a thermoneutral (20 degrees C) or hyperthermal (32 degrees C) environment and fed a basal (corn-soybean meal), high-fiber (48.5% wheat bran) or high-fat (10.6% choice white grease) diet from d 100 of gestation through a 22-d lactation. The diets were determined to contain 3.28, 2.76 and 3.75 Mcal ME/kg, respectively. All pigs received 8.0 Mcal of ME and 17.5 g of lysine daily prior to parturition and were allowed to consume their respective diets ad libitum after parturition. Litter size was standardized at 9 to 10 pigs by d 2 postpartum. Milk yields were determined for five, 4-d periods from about d 2 through 22 of lactation via a D2O dilution technique. Daily milk yield and litter weight gain began to plateau, and the efficiency of utilizing milk DM and milk energy for gain was depressed (P less than .01), in the latter stages of the lactation. Heat exposure (32 degrees C) reduced (P less than .05) voluntary ME intake and milk energy yield of the sow and increased (P less than .05) the sow's weight loss during lactation. In the hot environment, increasing dietary energy concentration resulted in a linear (P less than .08) increase in milk fat content and milk energy yield over the duration of the 22-d lactation. In the latter stages of lactation, pigs consuming high-fat milk required more (P less than .09) milk and milk energy per unit of weight gain. In the warm environment, milk energy yield was increased by dietary fat or fiber additions in early lactation, but not in late lactation. These results indicate that the effects of thermal heat stress on sow milk energy yield and litter weight gain are aggravated by dietary fiber addition and minimized by dietary fat addition.

Animals↗
PubMed1985

Multivariate analysis of the factors associated with the yield and purity of human monocyte isolation by countercurrent centrifugal elutriation (CCE).

Substantial variability in the purity and yield of human monocytes following countercurrent centrifugal elutriation (CCE) has been reported for some time; the factors influencing this variability have not been rigorously studied in the past. Utilizing 50 normal donors, we examined several dozen preprocedural variables possibly influencing 174 separate CCE experiments, and we determined the impact of these variables on the yield and purity of monocytes obtained following cytapheresis and CCE. Donor age was not correlated with CCE monocyte yield or purity; male gender correlated with higher monocyte purity following CCE purification. The major correlates of the yield and purity of monocytes obtained by CCE were the numbers and concentration of monocytes found in the leukocyte population entered into the elutriator apparatus. Fifty-eight percent of all donors gave a very consistent yield of monocytes by CCE, with a standard error from the mean of less than 15% over the 3 years of this study. All donors consistently gave fractions with a high percentage of monocytes, with the standard error of the mean CCE monocyte purity being less than 5% over the duration of the study. Thus, while the purity of monocytes collected by CCE is highly reproducible, the yield of monocytes by this procedure is somewhat less so. These monocyte purification endpoints are affected by a number of preprocedural variables centering mainly around the percentage, concentration, and total numbers of monocytes in the cytapheresis cell population.

Analysis of Variance↗
PubMed2000

Genetic correlation between days until start of luteal activity and milk yield, energy balance, and live weights.

The objective of this study was to estimate genetic correlations among fertility and measures of energy balance, dry matter intake, and live weight (change). Data from 622 first lactation cows (fed ad libitum a complete ration) included milk, fat, and protein yields; energy balance; and live weights for the first 15 wk of lactation. For a subset of the heifers (n = 329) and 91 contemporaries, progesterone values were measured in the milk twice a week and were used to determine the interval between calving and first luteal activity (CLA). To obtain correlations, a series of bivariate animal model analyses was performed. The heritabilities for CLA and energy balance were 0.16 and 0.33, respectively. Heritability for live weights were 0.48 to 0.61 and for live weight changes were 0.17 and 0.24. Genetic correlations of CLA with milk, fat, and protein yields were high and unfavorable (0.51, 0.65, and 0.48, respectively), whereas energy balance, live weight during lactation, and weight gain all had a favorable genetic correlation with CLA (range -0.40 to -0.80). When genetic variation in CLA was adjusted genetically for milk, fat, and protein yields, the correlation with feed intake became -0.49 and explained approximately half of the genetic variance in CLA. This supports that increasing genetic merit for feed intake, at a common genetic merit for yield, improved CLA. Furthermore, selection on an index including protein yield and energy balance or live weight (change) allowed 0.71 to 0.80 of the maximum response in protein yield without a negative selection effect on CLA.

Animals↗
PubMed2000

Biochemical markers of bone formation and resorption around parturition and during lactation in dairy cows with high and low standard milk yields.

Substantial changes occur in skeletal metabolism during lactation. These dynamic changes are monitored with biochemical bone markers. The goal of the present study was to follow these changes in lactating cows and to investigate whether cows with a higher milk yield have a higher mobilization rate of calcium from bone. Hydroxyproline, deoxypyridinoline, pyridinoline, and the carboxyterminal telopeptide of type I collagen (ICTP) were chosen as markers for bone resorption, whereas osteocalcin was used as a bone formation marker. Urine and blood samples were collected from cows with a mean standard milk yield of 4900 and 6500 kg, respectively, 14 d before, and 14 d, 1 mo, 1.5 mo, and monthly after parturition. Urinary hydroxyproline, deoxypyridinoline, and pyridinoline concentrations increased with time, but no differences between the two groups were evident. Concentrations of 1,25-dihydroxy vitamin D and ICTP of the two groups showed an increase 14 d after parturition. Furthermore, using multivariate regression models with age and milk yield as covariates, ICTP concentrations were higher in the group with a higher milk yield. In contrast, osteocalcin concentrations decreased 14 d after parturition and returned to prepartum values 1 mo after parturition. The increase of ICTP concentrations in both groups indicates that bone was substantially resorbed. At the same time, probably less Ca was embedded in bone, as indicated by the decrease of the osteocalcin concentrations. In conclusion, cows showed increased bone resorption around parturition, and cows with higher milk yield mobilize calcium more actively from bone than cows with lower milk yield.

Animals↗
PubMed2001

Genetic correlations among body condition score, yield, and fertility in first-parity cows estimated by random regression models.

Twenty type classifiers scored body condition (BCS) of 91,738 first-parity cows from 601 sires and 5518 maternal grandsires. Fertility data during first lactation were extracted for 177,220 cows, of which 67,278 also had a BCS observation, and first-lactation 305-d milk, fat, and protein yields were added for 180,631 cows. Heritabilities and genetic correlations were estimated using a sire-maternal grandsire model. Heritability of BCS was 0.38. Heritabilities for fertility traits were low (0.01 to 0.07), but genetic standard deviations were substantial, 9 d for days to first service and calving interval, 0.25 for number of services, and 5% for first-service conception. Phenotypic correlations between fertility and yield or BCS were small (-0.15 to 0.20). Genetic correlations between yield and all fertility traits were unfavorable (0.37 to 0.74). Genetic correlations with BCS were between -0.4 and -0.6 for calving interval and days to first service. Random regression analysis (RR) showed that correlations changed with days in milk for BCS. Little agreement was found between variances and correlations from RR, and analysis including a single month (mo 1 to 10) of data for BCS, especially during early and late lactation. However, this was due to excluding data from the conventional analysis, rather than due to the polynomials used. RR and a conventional five-traits model where BCS in mo 1, 4, 7, and 10 was treated as a separate traits (plus yield or fertility) gave similar results. Thus a parsimonious random regression model gave more realistic estimates for the (co)variances than a series of bivariate analysis on subsets of the data for BCS. A higher genetic merit for yield has unfavorable effects on fertility, but the genetic correlation suggests that BCS (at some stages of lactation) might help to alleviate the unfavorable effect of selection for higher yield on fertility.

Animals↗
PubMed2002

The impact of clinical lameness on the milk yield of dairy cows.

This paper investigates the impact of lameness on milk yield. The dataset includes approximately 8000 test-day milk yields from 900 cows on five farms in Gloucester, UK, collected over 18 mo from 1997 to 1999. The data were structured to account for repeated measures of test-day yield (1 to 10 per cow) and analyzed to account for this autocorrelation. Factors affecting milk yield included: farm of origin, stage of lactation, parity, and whether a cow ever became lame. In clinically lame cows, milk yield was reduced from up to 4 mo before a case of lameness was diagnosed and treated and for the 5 mo after treatment. The total mean estimated reduction in milk yield per 305-d lactation was approximately 360 kg. We conclude that clinical lameness has a significant impact on milk production. This is important information for assessing the economic impact of clinical lameness and its impact on cow health. It adds weight to the importance of early identification of clinical lameness and the urgency of techniques to improve the definition of this highly subjective diagnosis.

Animals↗
PubMed2002

Impact of low concentration factor microfiltration on milk component recovery and Cheddar cheese yield.

The effect of microfiltration (MF) on the composition of Cheddar cheese, fat, crude protein (CP), calcium, total solids recovery, and Cheddar cheese yield efficiency (i.e., composition adjusted yield divided by theoretical yield) was determined. Raw skim milk was microfiltered twofold using a 0.1-microm ceramic membrane at 50 degrees C. Four vats of cheese were made in one day using milk at lx, 1.26x, 1.51x, and 1.82x concentration factor (CF). An appropriate amount of cream was added to achieve a constant casein (CN)-to-fat ratio across treatments. Cheese manufacture was repeated on four different days using a randomized complete block design. The composition of the cheese was affected by MF. Moisture content of the cheese decreased with increasing MF CF. Standardization of milk to a constant CN-to-fat ratio did not eliminate the effect of MF on cheese moisture content. Fat recovery in cheese was not changed by MF. Separation of cream prior to MF, followed by the recombination of skim or MF retentate with cream resulted in lower fat recovery in cheese for control and all treatments and higher fat loss in whey when compared to previous yield experiments, when control Cheddar cheese was made from unseparated milk. Crude protein, calcium, and total solids recovery in cheese increased with increasing MF CF, due to partial removal of these components prior to cheese making. Calcium and calcium as a percentage of protein increased in the cheese, suggesting an increase in calcium retention in the cheese with increasing CF. While the actual and composition adjusted cheese yields increased with increasing MF CF, as expected, there was no effect of MF CF on cheese yield efficiency.

Animals↗
PubMed2003

Genotype by environment interaction for yield and somatic cell score with alternative environmental definitions.

Differential genetic expression in high and low opportunity Sicilian Holstein-Friesian and Brown Swiss herd environments was investigated using endogenous and exogenous variables in a set of three definitions. Results of genetic by environmental interaction were compared using alternative environmental definitions: within herd-year standard deviation for mature equivalent milk yield (HYSD), detectable incidence of normal vs. abnormal (peakless) lactation and herds clustered by causal relationships from high and low frequency use of nutrition, milking, health and animal handling practices. Data for genetic analysis consisted of first-lactation standardized yields of milk, fat and protein, and weighted somatic cell score for 8897 daughters of 825 Holstein-Friesian sires and 1143 daughters of 220 Brown Swiss sires. Components of covariance, heritabilities, and genetic correlations were estimated using bivariate and multivariate sire models for average and contrasting environments for each definition. Sire variances for yields were consistently smaller in the low opportunity environments of both breeds. Except for differential incidence of abnormal lactation in Friesian herds, correlated yield response in less privileged environments was 0.41 to 0.81 as much as in high opportunity environments, a substantial loss. Genetic correlations between HYSD environments for yield traits of Friesian were 0.48 to 0.66 but exceeded 0.80 for other definitions. Less correlated response in somatic cell score was also predicted for environments with low use of yield-enhancing practices (0.66 for Friesian and 0.61 for Brown Swiss), which may have resulted from less health care and poorer milking management. Therefore, unfavorable management interactions likely foster unequal gains from selection in contrasting environments defined exogenously or by incidence of peakless lactation. Conversely, greater genetic as well as phenotypic response is expected from additional inputs of nutrition, health care and milking management.

Analysis of Variance↗
PubMed2004

Hot topic: effects of frequent milking in early lactation on milk yield and udder health.

A field study was conducted to evaluate the influence of milking frequency (3 or 6 times/d [3x or 6x, respectively]) during the initial 21 d of lactation on milk and milk component yield and mammary gland health as indicated by somatic cell count. During 2 seasons, spring and fall, multiparous cows were milked 6 times/d until d 21 of lactation and then returned to the 3 times/d frequency for the remainder of lactation (6x; n = 9). Multiparous cows milked 3 times/d from the beginning of lactation served as a control group (3x; n = 17). With the exception of milking frequency, all other aspects of management, including housing, milk harvesting, and feeding, were identical between the groups and were consistent with industry norms. Retrospective analysis of Dairy Herd Improvement Association records was used to evaluate milk yield, milk component yield, and somatic cell scores. As expected, 6x cows produced more milk on the first test day than 3x cows. Compared with 3x cows, higher milk yields persisted for 6x cows from test day 2 through 6, indicating a persistent effect of early lactation milking frequency on milk yield potential for that lactation. Milk component yield followed a similar pattern: 6x cows produced significantly more protein, fat, and total solids than did control cows throughout the study. With regard to udder health, 6x cows had lower somatic cell counts at the first test day relative to 3x cows and had reduced somatic cell scores for the first 3 mo of lactation, which suggests that early lactation milking frequency influences the mammary gland capacity to resist infection in addition to improving milk production efficiency.

Animals↗
PubMed2006

Effect of automatic milking systems on milk yield in a hot environment.

A comparative study was performed to evaluate differences in milk yield between an automatic milking system (AMS) and a conventional herringbone milking parlor system. Two herds of Italian-Friesian cows were reared in the same barn, located in the Po Valley in northern Italy. Twenty-five primiparous cows and 10 multiparous cows were milked with an AMS, while at the same time 29 primiparous and 9 multiparous were milked twice daily in a milking parlor on the other side of the barn. A selection gate allowed cows to access the AMS only if the interval from last milking was >5 h. Multiparous cows in the AMS yielded more milk than multiparous cows in the milking parlor (34.2 +/- 0.7 vs. 29.4 +/- 0.6 kg/d). There was no difference in milk yield between primiparous cows in the AMS and in the milking parlor (28.9 +/- 0.4 vs. 28.8 +/- 0.3 kg/d). Milking frequency in the AMS was significantly higher in primiparous (2.8 +/- 0.03) than in multiparous cows (2.5 +/- 0.04). The hot season negatively affected milk yield; the milk yield reduction was higher for cows milked with the AMS (-4.5 +/- 0.6 kg/d) than in the milking parlor (-3.0 +/- 0.8 kg/d). In the AMS, milking frequency decreased during the hot season in primiparous cows (-0.3 +/- 0.1). We concluded that a positive AMS effect on milk yield is possible, but that steps must be taken to alleviate the discomfort involved with attracting cows to the AMS.

Animals↗
PubMed2007

Effects of genotype by environment interactions on milk yield, energy balance, and protein balance.

Increases in genetic merit for milk yield are associated with increases in mobilization of body reserves. This study assessed the effects of genotype by environment (GxE) interactions on milk yield and energy and protein balances. Heifers (n = 100) with high or low genetic merit for milk yield were milked 2 or 3 times a day and received rations of low or high caloric density. The management factors were selected to induce substantial differences in milk production levels and model different management strategies. The 2 x 2 x 2 factorial arrangement enables the assessment of the effects of genotype, environment, and GxE interactions. Mean daily energy-corrected milk production in the first 100 d in milk varied between 21.8 and 35.2 kg among the groups. The experimental factors affected milk production in the presumed direction. Ration was the most determinant factor on milk production. Effects of milking frequency and genetic merit were significant only in the groups that were fed rations with high caloric density. Signs for severe negative energy balances, protein balances, and low body condition scores, all of which may be indicative of health risks, were not concentrated in the highest producing cows. Feed caloric density and milking frequency had stronger effects on energy balances and protein balances, with unfavorable effects of low caloric density feed and an extra milking. This emphasizes the possible effect of mismanagement on animal health risks. High genetic merit cows had significantly lower postpartum body condition scores. Genotype x environment interactions existed, but more information is needed to determine if cows of different genetic merit for milk yield are differently at risk for disease under specific conditions. High milk production levels per se will increase allostatic load, but need not compromise the health status of relatively young cows. Ongoing one-sided selection for high yield may be combined with good animal health, but because high genetic merit for milk yield seems intrinsically connected to the allocation of resources from maintenance toward milk, this puts increasing demands on farmers' time and management skills.

Animals↗
PubMed1978

Relationship between milk yield and mammary gland development in mice.

Female mice from four lines exhibiting different nursing ability (as measured by mean 12-day weight of eight offspring within a nursed litter) were used to examine milk yield, body size, feed intake, and cellular development of mammary glands and liver. Three selected lines exceeded the control line in milk yield and mammary gland and liver weights. They had more total deoxyribonucleic acid, ribonucleic acid, and protein contents in both mammary gland and liver tissues than the control. Phenotypic correlations between milk yield and deoxyribonucleic acid contents of mammary glands and liver were .39 and .35, while correlations between milk yield and protein to deoxyribonucleic acid ratio of mammary glands and livers were .04 and .11. Milk yield was correlated closely with body size .57 and with feed intake .55. Milk yield was related more to cell number than to cell size of the mammary glands and liver, and large amounts of milk were produced by heavy dams with substantial feed intake.

Animals↗
PubMed1985

Multitrait estimation of relationships of first-lactation yields to body weight changes in Holstein heifers.

An experimental population of 994 Holstein heifers from 56 sires was used to estimate simultaneously heritabilities and genetic and phenotypic correlations between first-lactation yields and prepartum and postpartum weight changes. Variance and covariance components were estimated by the multitrait restricted maximum likelihood method. Heritability estimates were .09, .15, and .32 for first-lactation milk, protein, and fat yields. Heritability estimates ranged from .20 to .34 for prepartum and postpartum body weights and weight changes of first lactation. Weight gain from 350 to 462 d of age was highly correlated, genetically and phenotypically, with first-lactation milk, protein, and fat yields. Genetic and phenotypic correlations between first-lactation yields and body weights at calving and at 56, 112, 168, 224, and 280 d postpartum were positive, suggesting that the larger heifers had higher lactation yields. In contrast, genetic and phenotypic correlations between yields and weight gains during the first lactation were negative, indicating that high-producing heifers gained less weight during lactation than low-producing heifers. Heifers lost an average of 23 kg from calving to 56 d postpartum and gained weight thereafter. On genetic and phenotypic scales, larger heifers at first calving lost more weight from calving to 56 d postpartum and gained less weight from 56 d postpartum onward than smaller heifers.

Animals↗
PubMed1986

Estimating daily yields of cows milked three times a day.

Factors to estimate daily yield from one or two sampled milkings of cows milked three times a day were derived with data for 21 mo from seven Pennsylvania herds and data for 1 yr from five Utah herds. Accuracy of estimation increased with number of milkings weighed; standard deviation of error was nearly halved when information was included from two milkings instead of one. Fat yield did not increase as much as milk yield with increased time between milkings (interval); therefore, fat percentage factors increased with interval. If fewer milkings were sampled than weighed, fat yield was estimated by adjusting sample-day fat percentage. Effect of interval on protein yield was nearly the same as on milk yield. Therefore, milk factors are recommended for protein, and no adjustment to protein percentage is necessary if fewer milkings are sampled than weighed. Factors derived for milk were tested on records from 53 California and Oregon herds. Standard deviations of errors were similar to those from Utah and Pennsylvania data.

Animals↗
PubMed1988

Phenotypic and genetic relationship between linear functional type traits and milk yield for five breeds.

Lactation records of cows first calving between 18 and 35 mo were combined with linear type ratings assigned during the same lactation if before 43 mo. Phenotypic relationships were examined between final score and 13 type appraisal traits and first lactation milk yield from 2935 Ayrshire, 3154 Brown Swiss, 13,110 Guernsey, 50,422 Jersey, and 924 Milking Shorthorn records. Most phenotypic correlations between type and milk yield were low. Linear correlations of final score with first lactation milk yield were .18 to .38. Of the linear functional type traits, correlations with first lactation yield had greatest absolute values for dairy character (.19 to .53), udder depth (-.26 to -.30), and rear udder width (.20 to .31). Multiple correlations of all type appraisal traits with first lactation milk yield ranged from .41 to .59. Herd-year-season components of variance averaged 25% for type traits. Herd-year-season with sire interaction averaged 4%. Heritability estimates for final score from paternal half-sib analysis were from .11 to .21. Heritability estimates for linear traits ranged from .01 to .37. Genetic correlation between milk and final score was positive for Guernseys (.25) and Jerseys (.21). Genetic correlations between yield and most linear type traits were low to moderate except for dairy character (.53 to .77).

Animals↗
PubMed1989

Rumen-protected methionine and lysine: effects on animal performance, milk protein yield, and physiological measures.

Eight midlactation Holstein cows were used in a three-period (28 d) switchback design to evaluate addition of a combination of ruminally protected methionine (15 g/d) and lysine (40 g/d) on animal performance, milk protein yield, and physiological measures. Cows were fed for ad libitum intake a total mixed diet consisting of 50% corn silage and 50% concentrate (DM basis) or a similar diet to include the addition of the amino acids. Plasma methionine and lysine were elevated with the addition of amino acids. There were no differences between treatments in DM intake, milk yield, fat yield, milk fat percentage, or 4% FCM yield. Addition of amino acids increased milk protein percent (3.15 vs. 3.25). The quantities of alpha- caseins and beta-casein were increased while the quantity of kappa-caseins was decreased. Analysis of the major whey proteins revealed a decrease in serum albumin. Nutrient digestibility and nitrogen balance did not differ. Addition of methionine and lysine to a corn-based diet increased milk protein percentage and yield, plasma methionine and lysine concentrations, and increased yield of the casein proteins in milk.

Animal Feed↗
PubMed1991

Effect of dietary energy and previous bovine somatotropin on milk yield, mastitis, and reproduction in dairy cows.

Thirty multiparous lactating Holstein cows were blocked according to time of calving and assigned to a 2 x 3 factorial arrangement of treatments in a randomized complete block design to evaluate the effects of two dietary energy concentrations either without or with bST (20.6 mg/d per cow) administered to cows that had not or had received bST during the preceding lactation. Subcutaneous injection of bST began 28 to 35 d postpartum and continued for 39 wk. The dietary energy concentration x bST interaction was not significant for any response variable. Compared with DMI of control cows, DMI was higher for cows receiving bST, being 1.6 and 2.4 kg/d higher for cows receiving bST for one and two lactations, respectively. Milk, fat, and protein yields were higher for cows receiving bST than for controls. Those receiving bST for a second lactation also produced more milk than controls until wk 20; thereafter, milk yields were similar to those of controls. Somatotropin administration had no adverse effect on udder health. Cows receiving bST tended to ovulate less regularly than controls, which may be attributed to their higher milk yield. However, BW gains during lactation were similar for all treatments, indicating that bST-treated cows built energy reserves for the subsequent lactation. Although energy concentrations of the diets had no significant impact on yield, the higher energy diet tended to depress milk fat concentration. Administration of bST to dairy cows for a second, consecutive lactation yielded responses similar for the first 20 wk of the study to those receiving bST for the first time. However, after wk 20, milk yield was less than that by cows receiving bST for the first lactation but similar to that of control cows.

Animals↗
PubMed1992

The importance of maternal lineage on milk yield traits of dairy cattle.

Maternal lineage effects on milk yield traits, considered indicative of cytoplasmic inheritance, were evaluated with animal models. Cattle were from a selection experiment begun in 1968. Maternal pedigrees were traced to the first female member in the Holstein-Friesian Herdbook; purchased cows entering the herd, considered foundation females, were assigned to maternal lineage groups. All models accounted for year-season of calving, parity, and selection lines. Maternal lineage effects were included in a repeated records model with cow effects and preadjustment for sire and maternal grandsire transmitting abilities. Maternal lineage accounted for 5.2, 4.1, and 10.5% of phenotypic variation of preadjusted records of milk yield, fat yield, and fat percentage, respectively. Maternal lineage was evaluated as a fixed effect in an animal model including random animal and permanent environmental effects. Maternal lineage significantly affected fat percentage but not milk yield. Maternal genetic (nuclear) effects and their covariance with additive animal effects did not significantly account for additional variation nor did they influence maternal lineage estimates. Maternal lineage affected calculated net energy of milk but was not important for SNF yield or concentration. Maternal lineage influenced fat percentage, energy concentration, and, to a lesser extent, fat yield in milk of dairy cattle.

Animals↗