Genetic parameters for energy balance, feed efficiency, and related traits in Holstein cattle

Objectives of the current study were to estimate genetic parameters in Holstein cows for energy balance (EB) and related traits including dry matter intake (DMI), body weight (BW), body condition score (BCS), energy-corrected milk (ECM) production, and gross feed efficiency (GFE), defined as the ratio of total ECM yield to total DMI over the first 150d of lactation. Data were recorded for the first half of lactation on 227 and 175 cows in their first or later lactation, respectively. Random regression models were fitted to longitudinal data. Also, each trait was averaged over monthly intervals and analyzed by single and multivariate animal models. Heritability estimates ranged from 0.27 to 0.63, 0.12 to 0.62, 0.12 to 0.49, 0.63 to 0.72, and 0.49 to 0.53 for DMI, ECM yield, EB, BW, and BCS, respectively, averaged over monthly intervals. Daily heritability estimates ranged from 0.18 to 0.30, 0.10 to 0.26, 0.07 to 0.22, 0.43 to 0.67, and 0.25 to 0.38 for DMI, ECM yield, EB, BW, and BCS, respectively. Estimated heritability for GFE was 0.32. The genetic correlation of EB at 10d in milk (DIM) with EB at 150 DIM was -0.19, suggesting the genetic regulation of this trait differs by stage of lactation. Positive genetic correlations were found among DMI, ECM yield, and BW averaged over monthly intervals, whereas correlations of these traits with BCS depended upon stage of lactation. Total ECM yield for the lactation was positively correlated with DMI, but a negative genetic correlation between total ECM yield and EB was found. However, the genetic correlation between total ECM yield and EB in the first month of lactation was -0.02, indicating that total production is not genetically correlated with EB during the first month of lactation, when negative EB is most closely associated with diminished fitness. The genetic correlation between GFE and EB ranged from -0.73 to -0.99, indicating that selection for more efficient cows would favor a lower energy status. However, the genetic correlation between EB in the first month of lactation and GFE calculated from 75 to 150 DIM was not significant, indicating that the unfavorable correlation between GFE and EB in early lactation may be minimized with alternative definitions of efficiency. Thus, EB, GFE and related traits will likely respond to genetic selection in Holstein cows. However, the impact of selection for improved feed efficiency on EB must be carefully considered to avoid potential negative consequences of further reductions in EB at the onset of lactation.     

Heritability of gross feed efficiency and associations with yield, intake, residual intake, body weight, and body condition score in 11 commercial Pennsylvania tie stalls

The objectives of this study were to calculate the heritability of feed efficiency and residual feed intake, and examine the relationships between feed efficiency and other traits of productive and economic importance. Intake and body measurement data were collected monthly on 970 cows in 11 tie-stall herds for 6 consecutive mo. Measures of efficiency for this study were: dry matter intake efficiency (DMIE), defined as 305-d fat-corrected milk (FCM)/305-d DMI, net energy for lactation efficiency (NE_LE), defined as 305-d FCM/05-d NE_L intake, and crude protein efficiency (CPE), defined as 305-d true protein yield/305-d CP intake. Residual feed intake (RFI) was calculated by regressing daily DMI on daily milk, fat, and protein yields, body weight (BW), daily body condition score (BCS) gain or loss, the interaction between BW and BCS gain or loss, and days in milk (DIM). Data were analyzed with 3- and 4-trait animal models and included 305-d FCM or protein yield, DM, NE_L, or CP intake, BW, BCS, BCS change between DIM 1 and 60, milk urea nitrogen, somatic cell score, RFI, or an alternative efficiency measure. Data were analyzed with and without significant covariates for BCS and BCS change between DIM 1 and 60. The average DMIE, NE_LE, and CPE were 1.61, 0.98, and 0.32, respectively. Heritability of gross feed efficiency was 0.14 for DMIE, 0.18 for NE_LE, and 0.21 for CPE, and heritability of RFI was 0.01. Body weight and BCS had high and negative correlations with the efficiency traits (−0.64 to −0.70), indicating that larger and fatter cows were less feed efficient than smaller and thinner cows. When BCS covariates were included in the model, cows identified as being highly efficient produced 2.3 kg/d less FCM in early lactation due to less early lactation loss of BCS. Results from this study suggest that selection for higher yield and lower BW will increase feed efficiency, and that body tissue mobilization should be considered.     

Three-breed rotational crossbreds of Montbéliarde,Viking Red,and Holstein compared with Holstein cows for feed efficiency,income over feed cost,and residual feed intake

Rotational 3-breed crossbred cows of Montbéliarde, Viking Red, and Holstein (CB) were compared with Holstein (HO) cows for alternative measures of feed efficiency as well as income over feed cost (IOFC) and residual feed intake (RFI) during the first 150 d of first, second, and third lactations. Primiparous and multiparous CB (n = 63 and n = 43, respectively) and HO (n = 60 and n = 37, respectively) cows were fed the same total mixed ration twice daily with refusals weighed once daily. Feed was analyzed for dry matter content, net energy for lactation, and crude protein content. Body weight (BW) was recorded twice weekly. Daily production of milk, fat, and protein were estimated from monthly test days with best prediction. Measures of efficiency from 4 to 150 d in milk (DIM) were feed conversion efficiency (FCE), defined as fat plus protein production (kg) per kilogram of dry matter intake (DMI); ECM/DMI, defined as kilograms of energy-corrected milk (ECM) per kilogram of DMI; net energy for lactation efficiency (NE_LE), defined as ECM (kg) per megacalorie of net energy for lactation intake; crude protein efficiency (CPE), defined as true protein production (kg) per kilogram of crude protein intake; and DMI/BW, defined as DMI (kg) per kilogram of BW. The IOFC was defined as revenue from fat plus protein production minus feed cost. The RFI from 4 to 150 DIM for each lactation was the residual error remaining from regression of DMI on milk energy output (Mcal), metabolic BW, and energy required for change in BW (Mcal). Statistical analysis of measures of feed efficiency and RFI for primiparous cows included the fixed effects of year of calving and breed group. For multiparous cows, statistical analysis included breed as a fixed effect and cow as a repeated effect nested within breed group. Primiparous CB cows had higher means for FCE (+5.5%), ECM/DMI (+4.0%), NE_LE (+4.0%), and CPE (+5.2%) and a lower mean DMI/BW (–5.3%) than primiparous HO cows. Primiparous CB cows ($875) also had higher mean IOFC than primiparous HO cows ($825). In addition, mean RFI from 4 to 150 DIM was significantly lower (more desirable) for primiparous CB cows than HO cows. Likewise, multiparous CB cows had higher means for FCE (+8.2%), ECM/DMI (+5.9%), NE_LE (+5.8%), and CPE (+8.1%) and a lower mean for DMI/BW (–4.8%) than multiparous HO cows. Multiparous CB cows ($1,296) also had a higher mean for IOFC than multiparous HO cows ($1,208) and a lower mean for RFI from 4 to 150 DIM than HO cows.     

Comparison of 3-breed rotational crossbreds of Montbéliarde,Viking Red,and Holstein with Holstein cows fed 2 alternative diets for dry matter intake,production, and residual feed intake

The objective of this study was to compare 3-breed rotational crossbred (CB) cows of the Montbéliarde, Viking Red, and Holstein (HO) breeds with HO cows fed 2 alternative diets for dry matter intake (DMI), fat plus protein production (CFP), body weight (BW), body condition score (BCS), feed efficiency, and residual feed intake (RFI) from 46 to 150 days in milk (DIM) during first lactation. The CB cows (n = 17) and HO cows (n = 19) calved from September 2019 to March 2020. Cows were fed either a traditional total mixed ration diet (TRAD) or a higher fiber, lower starch total mixed ration diet (HFLS). The HFLS had 21% more corn silage, 47% more alfalfa hay, 44% less corn grain, and 43% less corn gluten feed than the TRAD. The 2 diets were analyzed for dry matter content, crude protein, forage digestibility, starch, and net energy for lactation. The BW and BCS were recorded once weekly. Daily milk, fat, and protein production were estimated from twice monthly milk recording with random regression. Measures of efficiency were CFP per kilogram of DMI and DMI per kilogram of BW. The RFI from 46 to 150 DIM was the residual error from regression of DMI on milk energy, metabolic BW, and the energy required for change in BW. Statistical analysis of all variables included the fixed effects of diet, breed group, and the interaction of diet and breed group. The CB cows fed HFLS had less DMI (?12%) and lower DMI/BW (?14%) compared with the HO cows fed TRAD. For CFP, CB and HO cows were not different when fed TRAD or HFLS. Furthermore, the CB cows fed HFLS had higher BW (+50 kg) compared with HO cows fed HFLS. The CB cows fed TRAD had higher BCS than HO cows fed TRAD and HO cows fed HFLS (+0.46 and +0.62, respectively). The HO cows fed TRAD had more DMI (+14%) and lower CFP per kilogram of DMI (?12%) compared with the HO cows fed HFLS. In addition, mean RFI from 46 to 150 DIM was lower and more desirable for CB cows fed HFLS (?120.0 kg) compared with HO cows fed TRAD (85.3 kg). Dairy producers may feed either TRAD or HFLS to CB cows without loss of CFP.     

Genetic heterogeneity of feed intake,energy-corrected milk,and body weight across lactation in primiparous Holstein,Nordic Red,and Jersey cows

In this study, we aimed to estimate and compare the genetic parameters of dry matter intake (DMI), energy-corrected milk (ECM), and body weight (BW) as 3 feed efficiency–related traits across lactation in 3 dairy cattle breeds (Holstein, Nordic Red, and Jersey). The analyses were based on weekly records of DMI, ECM, and BW per cow across lactation for 842 primiparous Holstein cows, 746 primiparous Nordic Red cows, and 378 primiparous Jersey cows. A random regression model was applied to estimate variance components and genetic parameters for DMI, ECM, and BW in each lactation week within each breed. Phenotypic means of DMI, ECM, and BW observations across lactation showed to be in very similar patterns between breeds, whereas breed differences lay in the average level of DMI, ECM, and BW. Generally, for all studied breeds, the heritability for DMI ranged from 0.2 to 0.4 across lactation and was in a range similar to the heritability for ECM. The heritability for BW ranged from 0.4 to 0.6 across lactation, higher than the heritability for DMI or ECM. Among the studied breeds, the heritability estimates for DMI shared a very similar range between breeds, whereas the heritability estimates for ECM tended to be different between breeds. For BW, the heritability estimates also tended to follow a similar range between breeds. Among the studied traits, the genetic variance and heritability for DMI varied across lactation, and the genetic correlations between DMI at different lactation stages were less than unity, indicating a genetic heterogeneity of feed intake across lactation in dairy cattle. In contrast, BW was the most genetically consistent trait across lactation, where BW among all lactation weeks was highly correlated. Genetic correlations between DMI, ECM, and BW changed across lactation, especially in early lactation. Energy-corrected milk had a low genetic correlation with both DMI and BW at the beginning of lactation, whereas ECM was highly correlated with DMI in mid and late lactation. Based on our results, genetic heterogeneity of DMI, ECM, and BW across lactation generally was observed in all studied dairy breeds, especially for DMI, which should be carefully considered for the recording strategy of these traits. The genetic correlations between DMI, ECM, and BW changed across lactation and followed similar patterns between breeds.     

An evaluation of production efficiencies among lactating Holstein-Friesian, Jersey, and Jersey × Holstein-Friesian cows at pasture

The objectives of this study were 1) to investigate production and energetic efficiencies among lactating dairy Holstein-Friesian (HF), Jersey (J), and Jersey × Holstein-Friesian (F₁) cows over a total lactation at pasture and 2) to measure the associations among efficiency variables and performance traits. Data from 110 cows were available (37 HF, 36 J, and 37 F₁). Breed groups were not balanced for parity; 16 HF, 10 J, and 9 F₁ were in parity 1, whereas the remainder were in parity 2. Milk production, body weight (BW), body condition score (BCS), and estimates of dry matter intake (DMI) corresponding to 51, 108, 149, 198, and 233 d in milk were available. Breed group had a significant effect on all the production parameters investigated: milk yield, solids-corrected milk (SCM), milk fat, protein and lactose concentrations, and milk solids (MLKS; fat + protein yield). Daily MLKS yield was similar for HF and J (1.33 and 1.28 kg/d, respectively). There was a tendency for F₁ (1.41 kg/d) to produce more MLKS compared with HF. The HF breed had higher BW throughout the study compared with F₁ and J. Mean BCS was higher for F₁ (3.00) and J (2.93) compared with HF (2.76). Mean DMI was similar with HF (16.9 kg) and F₁ (16.2 kg) and was lowest with J (14.7 kg). Breed group had a significant effect on all the efficiency parameters investigated: total DMI per 100 kg of BW, SCM per 100 kg of BW, MLKS per 100 kg of BW, and MLKS per total DMI, which tended to be highest for J. Production efficiency based on net energy intake per MLKS was most favorable for F₁ and J compared with HF [12.5, 13.0, and 14.1 UFL, respectively, where 1 UFL is defined as the net energy content of 1 kg of standard barley for milk production (O’Mara, 2000)]. Significant estimates of hybrid vigor were evidenced for milk yield, milk lactose content, SCM, MLKS, net energy for lactation, BW, BCS, and net energy intake per MLKS. The correlations examined indicated that production efficiency was positively associated with MLKS yield.     

Concentrate feeding strategy in lactating dairy cows: metabolic and endocrine changes with emphasis on leptin

This study aimed to evaluate metabolic and endocrine adaptations to energy intake in multiparous Holstein cows (n = 90; mean 9434 kg energy-corrected milk yield/305 d) over the first 20 wk postpartum and to assess the association of leptin with metabolic, endocrine, and zootechnical traits. Concentrates were fed automatically for 24 h at 30% (C30) or 50% (C50) of total dry matter intake (DMI) from wk 1 to 10 postpartum and at linearly reduced amounts thereafter. Roughage was fed for ad libitum intake. The DMI was measured over 24 h; milk yield and body weight (BW), twice/d; milk composition, 4 times/wk; and milk acetone, weekly. Blood samples for determination of metabolite, hormone, and electrolyte concentrations and enzyme activities were obtained at wk 2 prepartum, and at wk 1 to 16 and at wk 20 postpartum from 0730 to 0900. Body condition scores (BCS) and backfat thickness were measured postpartum and during wk 1, 4, 8, 12, 16, and 20. Energy balance (EB) was considerably lower, but milk yield only slightly lower, in C30 than C50. Metabolic stress was more marked in C30 than C50, expressed by lower, glucose, insulin, insulin-like growth factor-1 (IGF-1), triiodothyronine, milk protein, and lactose concentrations, higher nonesterified fatty acid, beta-hydroxybutyrate, growth hormone, and milk acetone concentrations, and an accelerated decrease in BCS and backfat thickness. Nevertheless, C30 adapted successfully and thus maintained high milk yields despite negative EB. Leptin concentrations were lower in C30 than in C50 over the first 20 wk postpartum and were positively associated with BCS, EB, BW, cholesterol, albumin, insulin, and IGF-1; negatively associated with DMI and triiodothyronine; and were higher in cows calving in spring than in fall. Leptin is one among several factors involved in the regulation of energy metabolism and may be important for overall homeostatic and homeorhetic control of metabolism and thus for maintenance of performance.     

Dietary restriction improved feed efficiency of inefficient lactating cows

The aim of this study was to reduce voluntary dry matter intake (DMI) to increase feeding efficiency of preclassified inefficient (INE) dairy cows through restricted feeding. We studied the effects of dietary restriction on eating behavior, milk and energy-corrected milk (ECM) production, in vivo digestibility, energy balance, and measures of feed efficiency [residual feed intake (RFI) and ECM/DMI]. Before the experiment, 12 pairs of cows were classified as INE. The 2 dietary treatments consisted of ad libitum feeding versus restricted feeding of the same total mixed ration containing 36.5% roughage. Inefficient cows fed the restricted total mixed ration had a shorter eating time and lower meal and visit frequency, but a similar rate of eating, meal size, and meal duration compared with INE cows fed ad libitum. Compared with the INE cows fed ad libitum, restricted INE cows had 12.8% lower intake, their dry matter and neutral detergent fiber digestibility remained similar, and their ECM yield was 5.3% lower. Feed efficiency, measured as RFI, ECM/DMI, and net energy retained divided by digestible energy intake, was improved in the restricted INE cows as compared with the ad libitum cows. Our results show that moderate DMI restriction has the potential to improve feed efficiency of preclassified INE cows.     

Effect of diets enriched in n-6 or n-3 fatty acids on dry matter intake,energy balance,oxidative stress,and milk fat profile of transition cows

The objective of this study was to determine the effect of dietary supplementation of n-3 polyunsaturated fatty acids (PUFA) and n-6 PUFA on dry matter intake (DMI), energy balance, oxidative stress, and performance of transition cows. Forty-five multiparous Holstein dairy cows with similar parity, body weight (BW), body condition score (BCS), and milk yield were used in a completely randomized design during a 56-d experimental period including 28 d prepartum and 28 d postpartum. At 240 d of pregnancy, cows were randomly assigned to one of the 3 isoenergetic and isoprotein dietary treatments, including a control ration containing 1% hydrogenated fatty acid (CON), a ration with 8% extruded soybean (HN6, high n-6 PUFA source), and a ration with 3.5% extruded flaxseed (HN3; high n-3 PUFA source). The HN6 and HN3 diets had an n-6/n-3 ratio of 3.05:1 and 0.64:1 in prepartum cows and 8.16:1 and 1.59:1 in postpartum cows, respectively. During the prepartum period (3, 2, and 1 wk before calving), DMI, DMI per unit of BW, total net energy intake, and net energy balance were higher in the HN3 than in the CON and NH6 groups. During the postpartum period (2, 3, and 4 wk after calving), cows fed HN3 and HN6 diets both showed increasing DMI, DMI as a percentage of BW, and total net energy intake compared with those fed the CON diet. The BW of calves in the HN3 group was 12.91% higher than those in the CON group. Yield and nutrient composition of colostrum (first milking after calving) were not affected by HN6 or HN3 but milk yield from 1 to 4 wk of milking was significantly improved compared with CON. During the transition period, BW, BCS, and BCS changes were not affected. Cows fed the HN6 diet had a higher plasma NEFA concentration compared with the CON cows during the prepartum period. Feeding HN3 reduced the proportion of de novo fatty acids and increased the proportion of preformed long-chain fatty acids in regular milk. In addition, the n-3 PUFA-enriched diet reduced the n-6/n-3 PUFA ratio in milk. In conclusion, increasing the n-3 fatty acids concentration in the diet increased both DMI during the transition period and milk production after calving, and supplementing n-3 fatty acids was more effective in mitigating the net energy balance after calving.     

Short communication: genetic relationships among daily energy balance, feed intake, body condition score, and fat to protein ratio of milk in dairy cows

Postpartum energy status is critically important to health and fertility, and it remains a major task to find suitable indicator traits for energy balance. Therefore, genetic parameters for daily energy balance (EB) and dry matter intake (DMI), weekly milk fat to protein ratio (FPR), and monthly body condition score (BCS) were estimated using random regression on data collected from 682 Holstein-Friesian primiparous cows recorded between lactation d 11 to 180. Average energy-corrected milk (ECM), EB, DMI, BCS, and FPR were 32.0 kg, 9.6 MJ of NE_L, 20.3 kg, 2.95, and 1.12, respectively. Heritability estimates for EB, DMI, BCS, and FPR ranged from 0.03 to 0.13, 0.04 to 0.19, 0.34 to 0.59, and 0.20 to 0.54. Fat to protein ratio was a more valid measure for EB in early lactation than DMI, BCS, or single milk components. Correlations between FPR and EB were highest at the beginning of lactation [genetic correlation (r_g) = −0.62 at days in milk (DIM) 15] and decreased toward zero. Dry matter intake was the trait most closely correlated with EB in mid lactation (r_g = 0.73 at DIM 120 and 150). Energy balance in early lactation was negatively correlated to EB in mid lactation. The same applied to DMI. Genetic correlations between FPR across lactation stages were all positive; the lowest genetic correlation (0.55) was estimated between the beginning of lactation and early mid lactation. Hence, to improve EB at the beginning of lactation, EB and indicator traits need to be recorded in early lactation. We concluded that FPR is an adequate indicator for EB during the energy deficit phase. Genetic correlations of FPR with ECM, fat percentage, and protein percentage showed that a reduction of FPR in early lactation would have a slightly negative effect on ECM, whereas milk composition would change in a desirable manner.     

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.     

Prepartum dietary management of energy intake affects postpartum intake and lactation performance by primiparous and multiparous Holstein cows

An experiment was conducted to determine the effect of plane of energy intake prepartum on postpartum performance. Primiparous (n = 24) and multiparous (n = 23) Holsteins were randomly assigned by expected date of parturition to 1 of 3 prepartum energy intakes. A moderate energy diet [1.63 Mcal of net energy for lactation (NE_L)/kg; 15% crude protein (CP)] was fed for either ad libitum intake (OVR) or restricted intake (RES) to supply 150 or 80% of National Research Council (2001) energy requirement, respectively, for dry cows in late gestation. To limit energy intake to 100% of NRC requirement at ad libitum dry matter intake (DMI), chopped wheat straw was included as 31.8% of dry matter (DM) in a control diet (CON; 1.21 Mcal of NE_L/kg of DM; 14% CP). Multiparous and primiparous cows assigned to OVR gained body condition during the dry period [initial body condition score (BCS) = 3.3], but were not overconditioned by parturition (BCS = 3.5). Multiparous cows in the OVR group lost more BCS postpartum than multiparous RES or CON cows. Primiparous cows lost similar amounts of BCS among dietary treatment groups postpartum. Addition of chopped wheat straw to CON diets prevented a large decrease in DMI prepartum in both primiparous and multiparous cows. During the first 3 wk postpartum, DMI as a percentage of BW was lower for multiparous OVR cows than for multiparous RES cows. Prepartum diet effects did not carry over through the entire 8-wk lactation period. Because of greater mobilization of body stores, OVR cows had greater milk fat percentage and greater 3.5% fat-corrected milk yield during the first 3 wk postpartum. Multiparous cows assigned to OVR experienced a 55% decrease in energy balance and primiparous cows a 40% decrease in energy balance during the last 3 wk before parturition, compared with CON or RES cows that had little change. Multiparous cows fed OVR had a greater contribution of energy from body energy reserves to milk energy output than either CON or RES cows. Overfeeding energy prepartum resulted in large changes in periparturient energy balance. Even in the absence of overconditioning, a large change in DMI and energy balance prepartum influenced postpartum DMI and BCS loss, especially for multiparous cows. Chopped wheat straw was effective at controlling energy intake prepartum, although primiparous cows did not achieve predicted DMI. Even so, controlling or restricting energy intake in primiparous cows was not detrimental to lactational performance over the first 8 wk of lactation.     

Neglect of lactation stage leads to naive assessment of residual feed intake in dairy cattle

Residual feed intake (RFI) is a candidate trait for feed efficiency in dairy cattle. We investigated the influence of lactation stage on the effect of energy sinks in defining RFI and the genetic parameters for RFI across lactation stages for primiparous dairy cattle. Our analysis included 747 primiparous Holstein cows, each with recordings on dry matter intake (DMI), milk yield, milk composition, and body weight (BW) over 44 lactation weeks. For each individual cow, energy-corrected milk (ECM), metabolic BW (MBW), and change in BW (ΔBW) were calculated in each week of lactation and were taken as energy sinks when defining RFI. Two RFI models were considered in the analyses; RFI model [1] was a 1-step RFI model with constant partial regression coefficients of DMI on energy sinks (ECM, MBW, and ΔBW) over lactation. In RFI model [2], data from 44 lactation weeks were divided into 11 consecutive lactation periods of 4 wk in length. The RFI model [2] was identical to model [1] except that period-specific partial regressions of DMI on ECM, MBW, and ΔBW in each lactation period were allowed across lactation. We estimated genetic parameters for RFI across lactation by both models using a random regression method. Using RFI model [2], we estimated the period-specific effects of ECM, MBW, and ΔBW on DMI in all lactation periods. Based on results from RFI model [2], the partial regression coefficients of DMI on ECM, MBW, and ΔBW differed across lactation in RFI. Constant partial regression coefficients of DMI on energy sinks over lactation was not always sufficient to account for the effects across lactation and tended to give roughly average information from all period-specific effects. Heritability for RFI over 44 lactation weeks ranged from 0.10 to 0.29 in model [1] and from 0.10 to 0.23 in model [2]. Genetic variance and heritability estimates for RFI from model [2] tended to be slightly lower and more stable across lactation than those from model [1]. In both models, RFI was genetically different over lactation, especially between early and later lactation stages. Genetic correlation estimates for RFI between early and later lactation tended to be higher when using model [2] compared with model [1]. In conclusion, partial regression coefficients of DMI on energy sinks differed across lactation when modeling RFI. Neglect of lactation stage when defining RFI could affect the assessment of RFI and the estimation of genetic parameters for RFI across lactation.     

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.     

Comparison of methane production,intensity, and yield throughout lactation in Holstein cows

Genetic selection to reduce methane (CH₄) emissions from dairy cows is an attractive means of reducing the impact of agricultural production on climate change. In this study, we investigated the feasibility of such an approach by characterizing the interactions between CH₄ and several traits of interest in dairy cows. We measured CH₄, dry matter intake (DMI), fat- and protein-corrected milk (FPCM), body weight (BW), and body condition score (BCS) from 107 first- and second-parity Holstein cows from December 2019 to November 2021. Methane emissions were measured using a GreenFeed device and expressed in terms of production (MeP, in g/d), yield (MeY, in g/kg DMI), and intensity (MeI, in g/kg FPCM). Because of the limited number of cows, only animal parameters were estimated. Both MeP and MeI were moderately repeatable (>0.45), whereas MeY presented low repeatability, especially in early lactation. Mid lactation was the most stable and representative period of CH₄ emissions throughout lactation, with animal correlations above 0.9. The average animal correlations of MeP with DMI, FPCM, and BW were 0.62, 0.48, and 0.36, respectively. The MeI was negatively correlated with FCPM (<−0.5) and DMI (>−0.25), and positively correlated with BW and BCS. The MeY presented stable and weakly positive correlations with the 4 other traits throughout lactation, with the exception of slightly negative animal correlations with FPCM and DMI after the 35th week. The MeP, MeI, and MeY were positively correlated at all lactation stages and, assuming animal and genetic correlations do not strongly differ, selection on one trait should lead to improvements in all. Overall, selection for MeI is probably not optimal as its change would result more from CH₄ dilution in increased milk yield than from real decrease in methane emission. Instead, MeY is related to rumen function and is only weakly associated with DMI, FPCM, BW, and BCS; it thus appears to be the most promising CH₄ trait for selection, provided that this would not deteriorate feed efficiency and that a system of large-scale phenotyping is developed. The MeP is easier to measure and thus may represent an acceptable alternative, although care would need to be taken to avoid undesirable changes in FPCM and BW.     

Milk production and feed intake of Holstein cows given short (30-d) or normal (60-d) dry periods

Eighty-four Holstein cows were utilized to evaluate effects of dry period (60 d vs. 30 d), with or without estradiol cypionate (ECP) injections to accelerate mammary involution, on prepartum and postpartum dry matter intake (DMI), body weight (BW), body condition score (BCS), and subsequent milk yield (MY). Treatments were arranged in a 3 x 2 x 2 factorial design that included dry period (30 d dry, 30 d dry + ECP, and 60 d dry), prepartum and postpartum bovine somatotropin (bST; 10.2 mg/d), and prepartum anionic or cationic diets. To accelerate mammary involution, ECP (15 mg) was injected intramuscularly at dry-off. No interaction of bST or prepartum diet with dry period length was detected on BW, BCS, or MY. No significant effects of dry period length on prepartum DMI, BW, or BCS were detected. Cows with shorter dry periods maintained postpartum BCS better and tended to have greater DMI immediately postpartum. Mean daily yields of milk for dry period groups did not differ during overall lactation period (1 to 21 wk). Injection of ECP at the onset of the 30-d dry period did not affect MY. No significant differences due to dry period length were detected for milk, 3.5% FCM, or SCM yields during first 10 wk of lactation. Data indicated that a short dry period protocol can be used as a management tool with no loss in the subsequent milk production of dairy cows.     

Effects of supplemental calcium salts of palm oil and chromium-propionate on insulin sensitivity and productive and reproductive traits of mid- to late-lactating Holstein × Gir dairy cows consuming excessive energy

This experiment compared insulin sensitivity, milk production, and reproductive outcomes in dairy cows consuming excessive energy during mid to late lactation and receiving in a 2 × 2 factorial design (1) concentrate based on ground corn (CRN; n = 20) or including 8% (DM basis) of Ca salts of palm oil (CSPO; n = 20), and (2) supplemented (n = 20) or not (n = 20) with 2.5 g/d of Cr-propionate. During the experiment (d 0–203), 40 multiparous, nonpregnant, lactating 3/4 Holstein × 1/4 Gir cows (initial days in milk = 81 ± 2; mean ± SE) were offered corn silage for ad libitum consumption, and individually received concentrate formulated to allow diets to provide 160% of their daily net energy for lactation requirements. From d ?15 to 203, milk production was recorded daily, blood samples collected weekly, and cow body weight (BW) and body condition score (BCS) recorded on d 0 and 203. For dry matter intake evaluation, cows from both treatments were randomly divided in 5 groups of 8 cows each, and allocated to 8 individual feeding stations for 3 d. Intake was evaluated 6 times/group. Glucose tolerance tests (GTT; 0.5 g of glucose/kg of BW) were performed on d ?3, 100, and 200. Follicle aspiration for in vitro embryo production was performed via transvaginal ovum pick-up on d ?1, 98, and 198. Mean DMI, net energy for lactation intake, as well as BW and BCS change were similar across treatments. On average, cows gained 40 kg of BW and 0.49 BCS during the experiment. Within weekly blood samples, CRN cows had lower serum concentrations of glucose, insulin, fatty acids, and insulin-to-glucose ratio compared with CSPO cows, suggesting increased insulin sensitivity in CRN cows. During the GTT, insulin-sensitivity traits were also greater in CRN versus CSPO cows. Supplemental Cr-propionate resulted in lower serum insulin concentrations and insulin-to-glucose ratio within CRN cows only, indicating that Cr-propionate improved basal insulin sensitivity in CRN but not in CSPO cows. During the GTT, however, Cr-propionate supplementation reduced hyperinsulinemia and insulin-to-glucose ratio across CSPO and CRN cows. Milk production, as well as number of viable oocytes collected and embryos produced within each aspiration, were not affected by treatments. Hence, replacing corn by Ca salts of palm oil in the concentrate did not improve insulin sensitivity in Holstein × Gir dairy cows consuming excessive energy during mid to late lactation, whereas Cr-supplementation was effective in improving basal insulin sensitivity in cows not receiving Ca salts of palm oil.     

Short communication: Use of lameness scoring to genetically improve claw health in Austrian Fleckvieh,Brown Swiss,and Holstein cattle

The specific objective of this study was to evaluate the use of lameness scoring to genetically improve claw health in Austrian Fleckvieh, Brown Swiss, and Holstein cows based on data from the “Efficient Cow” project. In 2014, a 1-yr data collection was carried out. Data from 6,519 cows kept on 161 farms were recorded. At each time of milk recording, lameness scores were assessed by trained staff of the milk recording organizations. Hoof trimming on these farms was documented and recorded as well. Veterinarian diagnoses and culling due to foot and leg problems from these farms were available from the routine recording system. As repeated lameness records per cow and lactation were available, an overall lactation lameness score was calculated. Estimated heritabilities for lameness were 0.11, 0.05, and 0.09 for Fleckvieh, Brown Swiss, and Holstein, respectively; however, only heritability estimates for Fleckvieh were significantly different from zero. Breeding values for lameness were obtained, reversed in sign, and cows were ranked according to their breeding value. A low breeding value for lameness resistance (the bottom 10% of the cows) was associated with a significantly higher frequency of trimmed cows, which indicates that the cows selected by the farmer to be trimmed are not completely random. Additionally, a high breeding value for lameness resistance (the top 10% of the cows) was associated with lower frequencies of claw diseases recorded at trimming, claw and leg diagnoses, and culling due to foot and leg problems, which highlights the usefulness of lameness scoring for genetic improvement of claw health. Overall, selecting for a better lameness score has the potential to reduce claw diseases, especially the frequency of severe claw diseases that lead to culling.     

Relationships among milk production, energy balance, plasma analytes, and reproduction in Holstein-Friesian cows

Associations were examined between components and indicators of early lactation energy balance (EB) and measures of fertility in Holstein cows. Milk production, dry matter intake (DMI), body condition score (BCS), and endocrine and metabolite data from 96 cows were analyzed using multivariate logistic regression and survival analysis. Fertility variables investigated were interval to commencement of luteal activity (C-LA), calving to conception interval (CCI), and conception rate to first service (CON1). Mean daily EB, milk protein content, and DMI during the first 28 d in milk were associated positively with CON1. Cows having poorer BCS (≤2.25) at first service had a lower CON1. Positive associations were identified among EB, milk protein content, DMI, and the likelihood of a shorter interval to C-LA. Cows having greater DMI and a more positive EB had an increased likelihood of a shorter CCI, whereas a lower nadir BCS was associated with an increased likelihood of a longer CCI. Milk yield was not associated with any of the fertility variables investigated. A greater plasma concentration of insulin-like growth factor I (IGF-I) during the first 2 wk of lactation was associated with a greater CON1 and an increased likelihood of a shorter interval to C-LA. In conclusion, we identified DMI as the principal component of EB influencing subsequent fertility. Furthermore, results indicate that milk protein content and plasma IGF-I concentration in early lactation may be useful indicators of reproductive efficiency.     

Three-breed rotational crossbreds of Montbéliarde,Viking Red,and Holstein compared with Holstein cows for dry matter intake,body traits,and production

Rotational crossbred cows of the Montbéliarde, Viking Red, and Holstein (HO) breeds (CB) were compared with HO cows for dry matter intake (DMI), body weight (BW), cow height, body condition score (BCS), and production during the first 150 d of first, second, and third lactations. Primiparous and multiparous CB (n = 63 and 43, respectively) and HO (n = 60 and 37, respectively) cows calved from September 2014 to June 2017. Cows were fed the same total mixed ration twice daily, with refusals weighed once daily. The BW was recorded twice weekly, and height at the withers and the hips was recorded monthly. The BCS was evaluated weekly. The fat plus protein production from 4 to 150 d in milk was calculated from monthly test days using best prediction. Primiparous and multiparous cows were analyzed separately. Statistical analysis for primiparous cows included the fixed effects of year of calving and breed group, and the analysis for multiparous cows included the fixed effect of breed group and the repeated effect of cow nested within breed group. Primiparous CB cows (2,807 kg) had lower mean DMI than HO cows (2,948 kg) from 4 to 150 d in milk of first lactation. Mean BW was not different for the CB (562 kg) and HO (556 kg) cows, but primiparous CB cows had mean wither height that was 4.0 cm shorter and mean hip height that was 2.0 cm shorter than that of HO cows. Primiparous CB cows (3.46) had higher mean BCS compared with HO cows (3.20). Mean fat plus protein production did not differ for the primiparous CB and HO cows (331 vs. 329 kg, respectively). Multiparous CB cows (3,360 kg) also had lower mean DMI than HO cows (3,592 kg) and did not differ (636 kg) from HO cows (644 kg) for mean BW. The CB cows had mean wither height that was 3.5 cm shorter than that of HO cows, but mean hip height did not differ for multiparous CB (145.2 cm) and HO (146.4 cm) cows. Mean BCS was higher for multiparous CB cows (3.25) than for HO cows (3.06), and mean fat plus protein production was not different for multiparous CB (445 kg) and HO (441 kg) cows. The lower DMI of the CB cows than HO cows resulted in less feed cost without loss of revenue from fat plus protein production.