Relationships among milk yield,body condition,cow weight,and reproduction in spring-calved Holstein-Friesians

Relationships among milk production, body condition score (BCS), body weight (BW), and reproduction were studied using logistic regression on data from 6433 spring-calving Holstein-Friesian dairy cows in 74 commercial herds. Multivariate models were adjusted for herd, breeding value for milk yield, proportion of Holstein-Friesian genes, lactation number, calving period, and degree of calving assistance. Significant associations between reproductive measures and components of energy balance were identified. Higher 200-d milk protein content and higher protein-to-fat ratio at start of breeding were associated with increased likelihood of submission for breeding in the first 21 d of the breeding season (SR21). High 100-d cumulative milk yield as a proportion of estimated 305-d milk yield (low persistency) was associated with a lower likelihood of pregnancy to first service (PREG1), whereas cows reaching peak milk yields earlier tended to have higher PREG1. Cows that reached nadir milk protein content relatively late in lactation had lower PREG1. Milk yield at first service and 305-d milk protein content were positively associated with the likelihood of pregnancy after 42 d of breeding (PR42). Higher 305-d milk lactose content was associated with increased PREG1 and PR42. Mean BCS at 60 to 100 d of lactation was positively associated with both SR21 and PR42, whereas nadir BCS was positively associated with PREG1. Cows with precalving BCS > 3.0 that also lost > 0.5 BCS unit by first service had lower PR42. More BW gain for 90 d after start of breeding was associated with higher SR21 and PREG1; more BW gain for 90 d after first service was associated with higher PR42. Milk protein and lactose content, BCS, and BW changes are important tools to identify cows at risk of poor reproduction.     

Relationships among body condition score, body weight, and milk production variables in pasture-based dairy cows

The objective of the present study was to identify and quantify relationships among dairy cow body condition score (BCS) and body weight (BW) and production variables in pasture-based, seasonal-calving herds. More than 2,500 lactation records from 897 spring-calving Holstein-Friesian and Jersey dairy cows were used in the analyses. Six variables related to BCS and BW, including observations precalving, at calving, and nadir as well as days to nadir and change precalving and between calving and nadir were generated. An exponential function was fitted within lactation to milk and 4% fat-corrected milk (FCM) yield data to model lactation curves. The milk production variables investigated were the parameters of the fitted function as well as accumulated yield of milk and FCM at 60 and 270 days in milk and average milk composition. Mixed models were used to identify BCS and BW variables that significantly affected milk production. After adjusting for the fixed effect of year of calving, parity, and days dry, milk and FCM yields were nonlinearly associated with calving and nadir BCS, increasing at a declining rate up to BCS 6.0 to 6.5 (10-point scale; approximately 3.5 in the 5-point scale) and declining thereafter. However, there was very little increase in milk and FCM yields above a calving BCS of 5.0 (approximately 3.0 in the 5-point scale). Average milk fat content over 60 and 270 days in milk was positively correlated with increasing calving and nadir BCS. In comparison, milk protein percentage was not influenced by calving BCS but was positively associated with nadir BCS and negatively associated with BCS lost between calving and nadir. The effect of BW and changes in BW were similar to the effect of BCS, although the scale of the effect was breed-dependent. For example, milk and FCM yield increased linearly with increasing calving BCS, but the effect was greater in Holstein-Friesians compared with Jersey cows. The results are consistent with the literature and highlight the important role that BCS and BW loss has on milk production, irrespective of the system of farming.     

Effects of dry period length and concentrate protein content in late lactation on body condition score change and subsequent lactation performance of thin high genetic merit dairy cows

Improving body condition score of thin cows in late lactation is necessary, because cows that are thin at drying off exhibit decreased fertility postpartum and are at increased risk of disease and of being culled in the subsequent lactation. Offering a diet low in crude protein (CP) content in late lactation may help to improve body condition score (BCS) at drying off, whereas imposing an extended dry period (EDP) has been advocated as another way to increase BCS at calving. To test these hypotheses, 65 thin cows (mean BCS 2.25 at 14 wk precalving) were managed on 1 of 3 treatments between 13 and 9 wk prepartum: normal protein control {NP; grass silage + 5 kg/d of a normal protein concentrate [228 g of CP/kg of dry matter (DM)]}, low protein [LP; grass silage + 5 kg/d of a low-protein concentrate (153 g of CP/kg of DM)], or EDP (cows dried off at 13 wk precalving and offered a grass silage-only diet). Both NP and LP cows were dried off at wk 8 prepartum, after which all cows were offered a grass silage-only diet until calving. After calving, all cows were offered a common diet (supplying 11.1 kg of concentrate DM/cow per day) for 19 wk. Between 13 and 9 wk prepartum, LP cows had lower DM intake, milk yield, and body weight than NP cows. Whereas EDP cows had lower serum β-hydroxybutyrate and fatty acid concentrations than those of NP cows, BCS at wk 9 prepartum did not differ between treatments. Cows on the LP treatment continued to have lower DMI and BW than those of NP and EDP cows between 8 wk prepartum and calving, but only EDP cows had a higher BCS at calving. Treatment did not affect calving difficulty score or calf birth weight. Although all cows were offered a common diet postpartum, cows on the LP treatment had lower DM intake and milk fat + plus protein yield than cows on any other treatment during the 19-wk period postpartum, but we found no differences in any postpartum indicator of body tissue reserves. The treatments imposed from wk 13 to 9 prepartum had no effect on any fertility or health parameters examined postpartum. Extending the dry period for thin cows improved their BCS at calving but did not allow these cows to achieve the target BCS of 2.75, and we found no beneficial effects of this treatment on cow performance postpartum. Offering a lower-protein diet to thin cows in late lactation did not improve BCS at calving above that of cows on a normal protein diet, but had unexplained long-term negative effects on cow performance.     

Associations among patterns in daily body weight, body condition scoring, and reproductive performance in high-producing dairy cows

The objective was to investigate the associations between body condition scores (BCS) and daily body weight (BW) in the first 150 d of lactation (DIM) and reproductive performance in high-producing dairy cows. Data included automated daily BW measurements and BCS of 2,020 Israeli Holstein cows from 7 commercial farms. Individual BW series were smoothed using penalized cubic splines, and variables representing BW patterns were generated. The presence of 7- and 21-d cycles in BW was determined using time-series analysis. Associations between BW and BCS and conception at first artificial insemination (AI) were analyzed using generalized estimating equations. Multivariate survival analysis was used for associations between BW and BCS and the calving-to-first AI interval, first AI-to-conception interval, and calving-to-conception interval. First-parity cows that lost ≥12% and second-parity cows that lost ≥15% of their BW from calving to nadir BW were less likely to conceive at first AI. Cows without 7-d cycles in BW were 1.48 times more likely to conceive at first AI relative to cows with 7-d cycles. The odds of conceiving at first AI increased by 53% for each additional unit in BCS from 40 to 60 DIM. In the multivariate survival analysis, a BCS of ≤2.5 between 40 and 60 DIM, the percentage of BW lost from calving to nadir BW, and a BW loss of ≥7% from calving to 10 DIM were associated with reduced reproductive performance. The presence of 21-d cycles in BW was associated with high reproductive performance in first-parity [odds ratio (OR) = 1.18] and second-parity cows (OR = 1.22). The presence of 7-d cycles in BW was associated with low reproductive performance in first-parity cows (OR = 0.77), but not in older cows. Based on previous findings and on the associations found in this study, we postulate that 21-d cycles are probably related to the sexual cycle and could be used as a proxy for assessing ovarian activity. Variables representing relative BW loss (%) were better predictors for impaired reproductive performance than those representing absolute BW loss (kg) and may be more suitable for estimating individual adaptation to negative energy balance in herds for which automated daily BW is available.     

Complete-lactation milk and component yields following a short (35-d) or a conventional (60-d) dry period management strategy in commercial Holstein herds

A total of 850 cows distributed among 13 commercial Holstein herds were involved in this study to compare the effects of 2 different dry period (DP) management strategies on milk and component yields as well as body condition score (BCS) over complete lactations. Within each herd and every 2 mo, cows were assigned to a short (35 d dry; SDP) or conventional (60 d dry; CDP) DP management based on previous lactation 305-d milk yield, predicted calving interval, and parity: primiparous (n = 414) and multiparous (n = 436). Cows assigned to CDP were fed a far-off dry cow ration from dry-off until 21 d prepartum, and were then switched to a precalving ration. Cows assigned to SDP were fed the precalving ration throughout their DP. Rations were different across herds, but the late-lactation, precalving, and early lactation rations were identical for both treatment groups within each herd. Additional milk was obtained at the end of lactation from cows assigned to SDP due to the extended lactation. Average daily milk yield in the following lactation was not different between treatments for third- or greater-lactation cows, but was significantly decreased in second-lactation SDP cows. However, when expressed as energy-corrected milk, this difference was not significant. Although lower for primiparous than multiparous cows, body weight and BCS were not affected by DP management strategy. Milk production and BCS responses to treatments varied among herds. Results from the present study suggest that a short DP management strategy could be more appropriate for today's dairy cows, although not suitable for all cows or all herds.     

Associations among body condition score, body weight, somatic cell count, and clinical mastitis in seasonally calving dairy cattle

The objective of this study was to determine if an association existed among body condition score (BCS), body weight (BW), and udder health, as indicated by somatic cell score (SCS) and cases of clinical mastitis (CM). The data consisted of 2,635 lactations from Holstein-Friesian (n = 523) and Jersey (n = 374) cows in a seasonal calving pasture-based research herd between the years 1986 and 2000, inclusive. Increased BCS at calving was associated with reduced SCS in first- and second-parity cows, and greater SCS in cows of third parity or greater. This relationship persisted for most BCS traits throughout lactation. Body weight was positively associated with SCS, although the effect was greater in Jersey cows than in Holstein-Friesians. Increased BCS and BW loss in early lactation were associated with lower SCS and a reduced probability of a high test-day SCC. Body condition score was not significantly related to CM with the exception of a curvilinear relationship between the daily rate of BCS change to nadir and CM in early lactation. Several BW variables were positively associated with a greater likelihood of CM. Nevertheless, most associations with udder health lacked biological significance within the ranges of BCS and BW generally observed on-farm. Results are important in assuring the public that modern dairy systems, where cows are subjected to substantial amounts of BCS mobilization in early lactation, do not unduly compromise cow udder health.     

Holstein-Friesian strain and feed effects on milk production, body weight, and body condition score profiles in grazing dairy cows

Data from 113 lactations across 76 cows between the years 2002 to 2004 were used to determine the effect of strain of Holstein-Friesian (HF) dairy cow and concentrate supplementation on milk production, body weight (BW), and body condition score (BCS; 1 to 5 scale) lactation profiles. New Zealand (NZ) and North American (NA) HF cows were randomly allocated to 1 of 3 levels of concentrate supplementation [0, 3, or 6 kg of dry matter (DM)/cow per d] on a basal pasture diet. The Wilmink exponential model was fitted within lactation (Y_DIM = a + b e(^{−0.05 × DIM)} + c × DIM). The median variation explained by the function for milk yield was 86%, between 62 and 69% for milk composition, and 80 and 70% for BW and BCS, respectively. North American cows and cows supplemented with concentrates had greater peak and 270-d milk yield. Concentrate supplementation tended to accelerate the rate of incline to peak milk yield, but persistency of lactation was not affected by either strain of HF or concentrate supplementation. No significant strain by diet interaction was found for parameters reported. New Zealand cows reached nadir BCS 14 d earlier and lost less BW (22 kg) postcalving than NA cows. Concentrate supplementation reduced the postpartum interval to nadir BW and BCS, and incrementally increased nadir BCS. New Zealand cows gained significantly more BCS (i.e., 0.9 × 10⁻³ units/d more) postnadir than NA cows, and the rate of BCS replenishment increased linearly with concentrate supplementation from 0.5 × 10⁻³ at 0 kg of DM/d to 0.8 × 10⁻³ and 1.6 × 10⁻³ units/d at 3 and 6 kg of DM/d concentrates, respectively. Although there was no significant strain by diet interaction for parameters reported, there was a tendency for a strain by diet interaction in 270-d BCS, suggesting that the effect of concentrate supplementation on BCS gain was, at least partly, strain dependent.     

The effect of left displacement of abomasum corrected by toggle-pin suture on lactation,reproduction, and health of Holstein dairy cows

Our objectives were to evaluate the effect of left displacement of abomasum (LDA) after correction by toggle-pin suture (TPS) on lactation performance, reproduction and health in Holstein dairy cows in a commercial dairy farm. Cows diagnosed with LDA and corrected by the TPS procedure (188 cows) during the first 70 d postpartum were matched with control herd-mates (186 controls) according to lactation number, calving date, and previous lactation 305-d mature equivalent milk yield. Cows were grouped according to parity and days in milk and fed the same total mixed ration throughout a 321-d lactation. Data collected included yields of milk and 3.5% fat-corrected milk (FCM), concentration and yields of milk fat, somatic cell count, incidence of mastitis, abortion, death and culling, in addition to reproductive measures. Cows affected with LDA corrected by the TPS procedure produced less milk and tended to produce less 3.5% FCM than control cows, but the decrease in production occurred only during the first 4 mo of lactation. Left displacement of abomasum did not affect the interval from calving to conception and conception rates, but it extended the period from calving to first postpartum artificial insemination. Incidences of abortions and mastitis were not influenced by LDA. Cows affected with LDA remained in the study for a shorter period than their control herdmates, and higher proportions of cows with LDA were sold or died. Death and culling were more pronounced immediately after the diagnosis of LDA and the TPS procedure.     

Genetic relationships among body condition score,body weight,milk yield,and fertility in dairy cows

Genetic (co)variances between body condition score (BCS), body weight (BW), milk production, and fertility-related traits were estimated. The data analyzed included 8591 multiparous Holstein-Friesian cows with records for BCS, BW, milk production, and/or fertility from 78 seasonal calving grass-based farms throughout southern Ireland. Of the cows included in the analysis, 4402 had repeated records across the 2 yr of the study. Genetic correlations between level of BCS at different stages of lactation and total lactation milk production were negative (-0.51 to -0.14). Genetic correlations between BW at different stages of lactation and total lactation milk production were all close to zero but became positive (0.01 to 0.39) after adjusting BW for differences in BCS. Body condition score at different stages of lactation correlated favorably with improved fertility; genetic correlations between BCS and pregnant 63 d after the start of breeding season ranged from 0.29 to 0.42. Both BW at different stages of lactation and milk production tended to exhibit negative genetic correlations with pregnant to first service and pregnant 63 d after the start of the breeding season and positive genetic correlations with number of services and the interval from first service to conception. Selection indexes investigated illustrate the possibility of continued selection for increased milk production without any deleterious effects on fertility or average BCS, albeit, genetic merit for milk production would increase at a slower rate.     

Effects of different transition diets on dry matter intake,milk production,and milk composition in dairy cows

The primary objective of this study was to evaluate the effect on dry matter intake (DMI), milk yield, milk composition, body weight (BW), and body condition score (BCS) change of cows offered diets differing in energy density in the last 4 wk of gestation and in the first 8 wk of lactation. Three diets (grass silage:straw, 75:25 on a dry matter basis (SS), grass silage (S), and grass silage + 3 kg concentrate daily (C)) precalving, and two diets (4 kg [LC] or 8 kg [HC] concentrate daily + grass silage ad libitum) postcalving were combined in a 3 x 2 factorial design. Sixty Holstein-Friesian cows entering their second lactation were blocked according to expected calving date and BCS into groups of six and were then allocated at random to the treatments. Individual feeding started 4 wk prior to the expected calving date and measurements were made until the end of the 8th wk of lactation. Mean DMI differed between each of the precalving treatments (7.4, 8.1, and 9.9 kg/d for SS, S, and C, respectively) in the precalving period. The DMI also differed between SS and C for wk 1 to 8 (13.5 and 14.2 kg/d) postcalving. Postcalving, milk (24.2, 26.2, and 28.2 kg/d), fat (933, 1063, and 1171 g/d), and protein (736, 797, and 874 g/d) yields differed between SS, S, and C, respectively. The BCS changes differed between SS and C (-0.09 and 0.12 of a BCS) in the precalving period and between SS and S compared with C (0.02, 0.06, and -0.26 of a BCS) for wk 1 to 8 postcalving. The BW change differed between SS and S compared with C in both wk 1 to 4 (-0.23, -0.37, and -1.25 kg/d) and wk 1 to 8 (0.18, 0.10, and -0.58 kg/ d) postcalving. The BW and BCS were lower at calving for cows on SS compared with C. The greater amount of concentrate supplement postcalving increased DMI, yields of milk, fat, and protein and decreased BW loss in the first 8 wk of lactation. In conclusion, these results indicate that a greater energy density diet in the final 4 wk of the dry period improves cow production in early lactation.     

Effects of body condition score at calving on indicators of fat and protein mobilization of periparturient Holstein-Friesian cows

The objective was to study the effects of body condition score (BCS) at calving on dairy performance, indicators of fat and protein mobilization, and metabolic and hormonal profiles during the periparturient period of Holstein-Friesian cows. Twenty-eight multiparous cows were classed according to their BCS (0 to 5 scale) before calving as low (BCS ≤2.5; n = 9), medium (2.75 ≤ BCS ≤ 3.5; n = 10), and high (BCS ≥3.75; n = 9), corresponding to a mean of 2.33, 3.13, and 4.17 points of BCS, and preceding calving intervals of 362, 433, and 640 d, respectively. Cows received the same diets based on preserved grass to allow ad libitum feed intake throughout the study, and lactation diet contained 30% of concentrate (dry-matter basis). Measurements and sampling were performed between wk −4 and 7 relative to calving. No significant effects were observed of BCS group on dry matter intake (kg/d), milk yield, BCS loss, plasma glucose, and insulin concentrations. The high-BCS group had the lowest postpartum energy balance and the greatest plasma concentrations of leptin prepartum, nonesterified fatty acids and β-hydroxybutyrate postpartum, insulin-like growth factor 1, and milk fat content. Milk fat yield was greater for the high- than the low-BCS group (1,681 vs. 1,417 g/d). Low-BCS cows had the greatest concentration of medium-chain fatty acids (e.g., sum of 10:0 to 15:0, and 16:0), and the lowest concentration and secretion of preformed fatty acids (e.g., cis-9 18:1) in milk fat. Milk protein secretion was lowest in the low-BCS group, averaging 924, 1,051, and 1,009 g/d for low-, medium-, and high-BCS groups, respectively. Plasma 3-methylhistidine was greater in wk 1 and 2 postpartum compared with other time points, indicating mobilization of muscle protein. Plasma creatinine tended to be lower and the 3-methylhistidine: creatinine ratio was greater in low- compared with medium- and high-BCS cows, suggesting less muscle mass but more intense mobilization of muscle protein in lean cows. High-BCS cows were metabolically challenged during early lactation due to intense mobilization of body fat. Conversely, limited availability of body fat in low-BCS cows was associated with increased plasma indicators of body protein mobilization during the first weeks of lactation, and lower milk protein secretion. These results should be confirmed using an experimental approach where calving BCS variation would be controlled by design.     

Analysis of daily body weight of high-producing dairy cows in the first one hundred twenty days of lactation and associations with ovarian inactivity

The objective of this study was to investigate, describe, and quantify daily body weight (BW) changes in the first 120 d of lactation in high-producing dairy cows. Data included 255,287 daily BW measurements from 2,167 Israeli Holstein dairy cows originating from 7 commercial dairy farms. Individual series of measurements were first smoothed using cubic splines for generating variables representing BW changes in early lactation and further analysis of the data. To construct standard BW curves stratified by parity and adjusted for farm, mixed models for repeated measurements were fit to the smoothed data, and least squares means for day in lactation were plotted. Time-series analysis techniques using polynomial functions of day in lactation and pairs of sine and cosine functions representing 7- and 21-d cycles were performed separately on each individual series of measurements. Additionally, generalized estimating equations were used to perform similar analysis on the data set as a whole. Mean days from calving to nadir BW increased significantly from first to later parities, as did mean BW loss from calving to nadir. The first-parity cow lost 6.5% of her BW from calving to d 29 in lactation, and second-parity and greater-parity cows lost 8.5 and 8.4% of their BW to d 34 and 38 in lactation, respectively. After nadir BW was reached, first-parity cows regained relative BW at a greater rate than did older parity cows. The trend in BW was nonlinear. A 7-d cycle was present in 247 cows (11.4%) and a 21-d cycle was present in 715 cows (33.0%). Presence of a 21-d cycle was associated with a 33% reduction in the risk of being diagnosed with inactive ovaries. Fewer days from calving to nadir BW and smaller BW loss from calving to nadir, coupled with a faster post-nadir increase in relative BW in first-parity cows compared with older cows indicated a smaller energy deficit in early lactation. Association between 21-d cycles in BW and ovarian activity suggest that these cycles were physiological and related to the estrous cycle. Therefore, monitoring them could be useful for indirectly assessing ovarian activity in a herd.     

Heritability and correlations among body condition score loss,body condition score,production and reproductive performance

The objectives of this study were to estimate the heritability of body condition score loss (BCSL) in early lactation and estimate genetic and phenotypic correlations among BCSL, body condition score (BCS), production, and reproductive performance. Body condition scores at calving and postpartum, mature equivalents for milk, fat and protein yield, days to first service, and services per conception were obtained from Dairy Records Management Systems in Raleigh, NC. Body condition score loss was defined as BCS at calving minus postpartum BCS. Heritabilities and correlations were estimated with a series of bivariate animal models with average-information REML. Herd-year-season effects and age at calving were included in all models. The length of the prior calving interval was included for all second lactation traits, and all nonproduction traits were analyzed with and without mature equivalent milk as a covariable. Initial correlations between BCS and BCSL were obtained using BCSL and BCS observations from the same cows. Additional genetic correlation estimates were generated through relationships between a group of cows with BCSL observations and a separate group of cows with BCS observations. Heritability estimates for BCSL ranged from 0.01 to 0.07. Genetic correlation estimates between BCSL and BCS at calving ranged from -0.15 to -0.26 in first lactation and from -0.11 to -0.48 in second lactation. Genetic correlation estimates between BCSL and postpartum BCS ranged from -0.70 to -0.99 in first lactation and from -0.56 to -0.91 in second lactation. Phenotypic correlation estimates between BCSL and BCS at calving were near 0.54, whereas phenotypic correlation estimates between BCSL and postpartum BCS were near -0.65. Genetic correlations between BCSL and yield traits ranged from 0.17 to 0.50. Genetic correlations between BCSL and days to first service ranged from 0.29 to 0.68. Selection for yield appears to increase BCSL by lowering postpartum BCS. More loss in BCS was associated with an increase in days to first service.     

Associations among body condition score, body weight, and reproductive performance in seasonal-calving dairy cattle

The objective of the present study was to identify and quantify relationships between body condition score (BCS) and body weight (BW) in dairy cows with reproduction variables in pasture-based, seasonal-calving dairy herds. Over 2,500 lactation records from 897 spring-calving Holstein-Friesian dairy cows were used in the analyses. Eleven BCS- and 11 BW-related variables were generated, including observations at calving, nadir, planned start of mating (PSM), and first service, as well as days to nadir and the amount and rate of change between periods. The binary reproductive variables were cycling by PSM, mated in the first 21 d from PSM, pregnant to first service, and pregnant in the first 21, 42, and 84 d of the seasonal mating period. Generalized estimating equations were used to identify BCS and BW variables that significantly affected the probability of a successful reproductive outcome. After adjusting for the fixed effect of year of calving, parity (for cycling by PSM only), and the interval from calving to either first service or PSM, reproductive performance was found to be significantly affected by BW or BCS at key points, and by BCS and BW change during lactation. All reproductive response measures were negatively affected when BCS and BW measures indicated an increased severity and duration of the postpartum negative energy balance. In particular, cycling by PSM was positively associated with calving BCS, whereas pregnancy at 21, 42, and 84 d post-PSM were positively associated with nadir BCS and BW gain post-PSM, and negatively associated with BCS loss between calving and nadir. The results highlight the important role that BCS and BW loss has on reproductive performance, especially in seasonal-calving dairy systems because of the short period between calving and PSM.     

Consequences of dietary energy source and energy level on energy balance,lactogenic hormones,and lactation curve characteristics of cows after a short or omitted dry period

Omitting the dry period (DP) generally reduces milk production in the subsequent lactation. The aim of this study was to evaluate the effect of dietary energy source—glucogenic (G) or lipogenic (L)—and energy level—standard (std) or low—on milk production; energy balance (EB); lactogenic hormones insulin, insulin-like growth factor 1 (IGF-1), and growth hormone (GH); and lactation curve characteristics between wk 1 and 44 postpartum in cows after a 0-d or 30-d DP. Cows (n = 110) were assigned randomly to 3 transition treatments: a 30-d DP with a standard energy level required for expected milk yield [30-d DP(std)], a 0-d DP with the same energy level as cows with a 30-d DP [0-d DP(std)], and a 0-d DP with a low energy level [0-d DP(low)]. In wk 1 to 7, cows were fed the same basal ration but the level of concentrate increased to 6.7 kg/d for cows fed the low energy level and to 8.5 kg/d for cows fed the standard energy level in wk 4. From wk 8 postpartum onward, cows received a G ration (mainly consisting of corn silage and grass silage) or an L ration (mainly consisting of grass silage and sugar beet pulp) with the same energy level contrast (low or std) as in early lactation. Cows fed the G ration had greater milk, lactose, and protein yields, lower milk fat percentage, greater dry matter and energy intakes, and greater plasma IGF-1 concentration compared with cows fed the L ration. Dietary energy source did not affect EB or lactation curve characteristics. In cows with a 0-d DP, the reduced energy level decreased energy intake, EB, and weekly body weight gain, but did not affect milk production or lactation curve characteristics. A 30-d DP resulted in a greater total predicted lactation yield, initial milk yield after calving, peak milk yield, energy intake, energy output in milk, days to conception [only when compared with 0-d DP(low)], plasma GH concentration [only when compared with 0-d DP(std)], and decreased weekly body weight gain compared with a 0-d DP. A 30-d DP decreased both the increasing and the declining slope parameters of the lactation curve and the relative rate of decline in milk yield (indicating greater lactation persistency) compared with a 0-d DP, and decreased plasma insulin and IGF-1 concentration, and EB. In conclusion, feeding a G ration after wk 7 in milk improved energy intake and milk production, but did not affect EB compared with an L ration. For cows without a DP, a reduced dietary energy level did not affect milk production and lactation curve characteristics, but did decrease EB and weekly body weight gain. A 30-d DP increased milk yield and lactation persistency, but decreased milk fat and protein content, EB, and plasma insulin and IGF-1, compared with a 0-d DP.     

Genetic parameters of feed intake, production, body weight, body condition score, and selected type traits of Holstein cows in commercial tie-stall barns

The objectives of this study were to determine the feasibility of measuring feed intake in commercial tie-stall dairies and infer genetic parameters of feed intake, yield, somatic cell score, milk urea nitrogen, body weight (BW), body condition score (BCS), and linear type traits of Holstein cows. Feed intake, BW, and BCS were measured on 970 cows in 11 Pennsylvania tie-stall herds. Historical test-day data from these cows and 739 herdmates who were contemporaries during earlier lactations were also included. Feed intake was measured by researchers once per month over a 24-h period within 7 d of 6 consecutive Dairy Herd Information test days. Feed samples from each farm were collected monthly on the same day that feed intake was measured and were used to calculate intakes of dry matter, crude protein, and net energy of lactation. Test-day records were analyzed with multiple-trait animal models, and 305-d fat-corrected milk yield, dry matter intake, crude protein intake, net energy of lactation intake, average BW, and average BCS were derived from the test-day models. The 305-d traits were also analyzed with multiple-trait animal models that included a prediction of 40-wk dry matter intake derived from National Research Council equations. Heritability estimates for 305-d intake of dry matter, crude protein, and net energy of lactation ranged from 0.15 to 0.18. Genetic correlations of predicted dry matter intake with 305-d dry matter, crude protein, and net energy of lactation intake were 0.84, 0.90, and 0.94, respectively. Genetic correlations among the 3 intake traits and fat-corrected milk yield, BW, and stature were moderate to high (0.52 to 0.63). Results indicate that feed intake measured in commercial tie-stalls once per month has sufficient accuracy to enable genetic research. High-producing and larger cows were genetically inclined to have higher feed intake. The genetic correlation between observed and predicted intakes was less than unity, indicating potential variation in feed efficiency.     

Events of elevated somatic cell counts in high-producing dairy cows are associated with daily body weight loss in early lactation

The objective of this study was to determine associations between body weight (BW) and body condition score (BCS) variables indicating a more severe negative energy balance in early lactation and events of somatic cell counts (SCC) >250,000 cells/mL and SCC >400,000 cells/mL in dairy cows. We studied lactations from 634 primiparous and 1,086 multiparous Israeli Holstein dairy cows originating from 7 commercial dairy farms. Generalized mixed models with a random herd effect were used to quantify the effects of BW and BCS variables in early lactation on events of elevated SCC. Data were analyzed using 2 different approaches. In the first approach, only first events in a lactation were taken into account, whereas in the second approach, all events in a lactation were analyzed and repeated events from the same cow were accounted for. Although no associations were found between the different BW and BCS variables and first events of elevated SCC, associations were present between these variables and events of elevated SCC when all events were analyzed. The cumulative incidence of a lactation with multiple events of SCC >250,000 cells/mL was 8.8 and 27.7% for primiparous and multiparous cows, respectively. The odds of an event of SCC >250,000 cells/mL were 25% greater for cows belonging to the upper quartile in relative BW loss from calving to nadir BW (loss >12.3, 15.0, and 15.7% for first-, second-, and third- parity and greater cows, respectively) compared with cows losing less relative BW. Odds of an event were 44% greater for cows with ketosis when compared with cows without. The cumulative incidence of a lactation with multiple events of SCC >400,000 cells/mL was 4.1 and 14.3% for primiparous and multiparous cows, respectively. The odds of an event of SCC >400,000 cells/mL were 43% greater for cows belonging to the upper quartile in relative BW loss from calving to nadir BW compared with cows losing less relative BW. Odds of an event were 33% greater for cows with ketosis when compared with cows without. Assuming that extreme BW loss and ketosis in early lactation indicate a more severe negative energy balance, our findings support the hypothesis that greater negative energy balance in early lactation predisposes dairy cows to udder inflammation. Considering the fact that many of the events were recurring, we stress the importance of including all events in the analysis and postulate the possibility of long-term detrimental effects of negative energy balance on udder health.     

The effect of nutritional management in early lactation and dairy cow genotype on milk production,metabolic status,and uterine recovery in a pasture-based system

High levels of milk production coupled with low feed intake cause negative energy balance in early lactation, especially in the first month postpartum (PP). Therefore, specific nutritional management at this time may improve nutritional and metabolic status with the possibility of contrasting genotypes responding differently. Thus, the objective of this study was to compare the effects of nutritional management strategies and dairy cow genotype on milk production, metabolic status, and some fertility parameters during early lactation in a pasture-based system. Sixty Holstein Friesian cows were blocked on parity and genotype [low-fertility high-milk (LFHM) and high-fertility low-milk (HFLM)] and were randomly assigned to 1 of 2 treatments in a 2 × 2 factorial arrangement, in a randomized complete block design based on calving date, previous 305-d milk yield, and precalving body condition score (BCS). The nutritional management treatments were: (1) ad libitum access to fresh pasture plus an allowance of 3 kg of concentrates per day (CTR, n = 30); and (2) ab libitum access to a tailored total mixed ration (TMR, n = 30). These diets were offered for the first 30 d PP. Following the first 30 d PP, cows fed TMR joined the CTR treatment and were managed similarly until 100 d PP. Blood samples were taken at d 7, 14, 21, and 28 PP to determine metabolic status. Milk samples for composition analysis were collected weekly and BCS assessed every 2 wk. Genotype had a significant effect on milk output, whereas LFHM had increased fat (+0.28 kg/d) and fat-plus-protein (+0.17 kg/d) yield in the first 30 d PP compared with HFLM cows. The LFHM group also exhibited higher protein and lactose yields over the first 100 d PP. Nutritional management did create significant differences in milk composition in the first 30 d: TMR cows had lower protein, milk urea nitrogen, and casein concentration and higher lactose concentration than CTR cows. Over the first 100 d PP, TMR cows had higher fat-plus-protein and lactose yields. Feeding TMR reduced concentrations of nonesterified fatty acids (?0.12 mmol/L) and β-hydroxybutyric acid (?0.10 mmol/L) compared with the CTR group. Cows fed TMR had smaller BCS losses from calving to 60 d PP. There was no effect of any treatment on uterine recovery. Cows in the LFHM group demonstrated greater milk production in the first 30 and 100 d in milk. These results demonstrate that feeding cows a TMR for the first month of lactation has positive effects on milk output, metabolic status, and BCS profile.     

Prenatal maternal effects on body condition score, female fertility, and milk yield of dairy cows

In this study, maternal effects were described as age of dam at first and second calving, first-lactation body condition score (BCS) of the dam during gestation, and milk yield of the dam. The impact of these effects on first-lactation daughter BCS, fertility, and test-day milk yield was assessed. The effect of milk yield of dam on daughter 305-d yield in the latter's first 3 lactations was also investigated. The proportion of total phenotypic variance in daughter traits accounted for by maternal effects was calculated. Dams calving early for the first time (18 to 23 mo of age) had daughters that produced 4.5% more first-lactation daily milk, had 7% higher BCS, and had their first service 3 d earlier than cows whose dams calved late (30 to 36 mo). However, daughters of dams that calved early had difficulties conceiving as they needed 7% more inseminations and had a 7.5% higher return rate. Cows from second calvings of relatively young (36 to 41 mo) dams produced 6% more first-lactation daily milk, had 2% higher BCS, and showed a significantly better fertility profile than cows whose dams calved at a late age (47 to 55 mo). High maternal BCS during gestation had a favorable effect on daughter BCS, nonreturn rate, and number of inseminations per conception. However, it was also associated with a small decrease in daughter daily milk yield. Changes in dam BCS during gestation did not affect daughter performance significantly. Maternal effects of milk yield of the dam, expressed as her permanent environment during lactation, adversely affected daughter 305-d milk, fat, and protein yield. However, although the effect was significant, it was practically negligible (<0.3% of the mean). Finally, overall maternal effects accounted for a significant proportion of the total phenotypic variance of calving interval (1.4 ± 0.6%) and nonreturn rate (1.1 ± 0.5%).     

Short communication: Genetic relationship between calving traits and body condition score before and after calving in Canadian Ayrshire second-parity cows

The objective of this study was to investigate the genetic relationship between body condition score (BCS) and calving traits (including calving ease and calf survival) for Ayrshire second-parity cows in Canada. The use of random regression models allowed assessment of the change of genetic correlation from 100 d before calving to 335 d after calving. Therefore, the influence of BCS in the dry period on subsequent calving could be studied. Body condition scores were collected by field staff several times over the lactation in 101 herds from Québec and calving records were extracted from the official database used for Canadian genetic evaluation of calving ease. Daily heritability of BCS increased from 0.07 on d 100 before calving to 0.25 at 335 d in milk. Genetic correlations between BCS at different stages ranged between 0.59 and 0.99 and indicated that genetic components for BCS did not change much over lactation. With the exception of the genetic correlation between BCS and direct calving ease, which was low and negative, genetic correlations between BCS and calving traits were positive and moderate to high. Correlations were the highest before calving and decreased toward the end of the ensuing lactation. The correlation between BCS 10 d before calving and maternal calving ease was 0.32 and emphasized the relationship between fat cows before calving with dystocia. Standards errors of the genetic correlations estimates were low. Genetic correlations between BCS and calf survival were moderate to high and favorable. This indicates that cows with a genetically high BCS across lactation would have a greater chance of producing a calf that survived (maternal calf survival) and that they would transmit genes that allow the calf to survive (direct calf survival).