The existence of a dry period in late pregnancy is essential for a dairy cow, helping to regenerate the mammary gland secretory epithelium (Church et al., Reference Church, Fox, Gaskins, Hancock and Gay2008). The dry period is usually 51–60 d for lactating cows (Bachman and Schairer, Reference Bachman and Schairer2003; Gulay et al., Reference Gulay, Hayen, Bachman, Belloso, Liboni and Head2003). However, studies have been conducted to investigate the effect of shortening the dry period on health, milk production and its composition (Bachman and Schairer, Reference Bachman and Schairer2003; Church et al., Reference Church, Fox, Gaskins, Hancock and Gay2008). Starting lactation by rapidly increasing milk production whilst not increasing feed intake causes the cow to enter a physiological state of negative energy balance (NEB: Esposito et al., Reference Esposito, Irons, Webb and Chapwanya2014) and, as a result, estrus and ovulation may not occur (lactational anoestrus: Dupont et al., Reference Dupont, Reverchon, Bertoldo and Froment2014). Reducing the dry period can decrease postpartum milk production and improve energy balance conditions in high-producing cows (Bachman and Schairer, Reference Bachman and Schairer2003; Gulay et al., Reference Gulay, Hayen, Bachman, Belloso, Liboni and Head2003). Therefore, Gumen et al. (Reference Gümen, Rastani, Grummer and Wiltbank2005) reported that by shortening or eliminating the dry period, the first ovulation occurs sooner, and reproductive status improves.
Fertility in dairy cows with a high BCS at parturition (BCS > 3.5) is compromised due to reduced dry matter intake before parturition, Also, these cows need more time after parturition to increase their appetite, which exacerbates the NEB compared to cows with a moderate BCS (Pedron et al., Reference Pedron, Cheli, Senatore, Baroli and Rizzi1993). Barletta et al. (Reference Barletta, Maturana Filho, Carvalho, Del Valle, Netto, Rennó, Mingoti, Gandra, Mourão and Fricke2017) showed that the concentration of NEFA and BHBA in cows that lost less BCS after calving is lower than other cows. It has been reported that the loss of BCS has a negative effect on reproductive performance (Bachman and Schairer, Reference Bachman and Schairer2003). Wathes et al. (Reference Wathes, Fenwick, Cheng, Bourne, Llewellyn, Morris, Kenny, Murphy and Fitzpatrick2007) showed that mobilization of adipose tissue during NEB damages oocyte quality and therefore increases parturition distance to first ovulation (the puerperium period), reduces pregnancy rate and decreases embryonic development. Whilst the major effects of change in BCS are postpartum. Chebel et al. (Reference Chebel, Mendonça and Baruselli2018) have also reported that loss of BCS during the dry period is associated with a higher incidence of uterine disease, reduced fertility and reduced production of milk, fat, and protein. We hypothesized that the dry period may have different effects on energy balance and reproductive efficiency in high-producing dairy cows with moderate or high pre-calving BCS. Therefore, the study aimed to determine the effects of the dry period and BCS on colostrum and milk yield and quality, blood parameters and reproduction efficiency in high-producing dairy cows.
Materials and methods
This research was conducted in a dairy farm research station consisting of 4000 dairy cows (FKA Co., Isfahan, Iran). The Animal Care Advisory Committee of the Isfahan University of Technology approved the implementation of this experiment (Iranian Council of Animal Care, 2015).
Animals and management
Multiparous Holstein dairy cows in late lactation (n = 120, parity 3.5 ± 1.5, average 305-day milk yield 12 321 ± 341 kg) were randomly allocated to 2 experimental groups of 60 blocked for production and parity. Sixty cows were dried off to enter the experiment about 50 d before parturition (normal dry period) and another 60 about 28 d before parturition (short dry period). In both groups, cows were drying gradually by reducing milking times from 3 to 2 times. Therefore, the average milk of cows at the beginning of drying was below 20 kg. When the cows entered the experiment, the thickness of the back fat was measured using ultrasonography (4.5–8.5 MHz frequency, Easi-Scan ultrasound scanner, BCF Technology Ltd., Livingston, UK). Then, each group was divided into two sub-groups of 30 cows with a body score of moderate (2.75 ≤ 3.5) and high (≥ 3.5). Therefore, there were 4 experimental treatments: normal dry period with high BCS (NH), normal dry period with moderate BCS (NM), short dry period with high BCS (SH) and short dry period with moderate BCS (SM). Cows were kept in individual pens with free access to water before and after calving and milked three times a day after calving (07:00, 15:00, and 23:00 h). Cows were fed a total mixed ration formulated according to the NRC (2001) recommendations (online Supplementary Table S1).
Sampling and measurements
Colostrum samples were taken from the first postpartum milking of cows and the amount of colostrum in the first milking was recorded for each cow. The samples were diluted at a ratio of 1: 3 with phosphate-buffered saline and then were homogenized. Colostrum composition (fat, protein, lactose, solid-not-fat and total solids) were measured with a Milk-O-Scan (Milk-O-Scan 4000, Foss Electric) with conversion to their true value according to Li-Chan et al. (Reference Li-Chan, Kummer, Losso, Kitts and Nakai1995). The Brix index was measured with a refractometer. The amount of milk production was recorded monthly until 120 d after caving, and milk samples were taken monthly to measure the percentage of milk fat and protein with a Milk-O-Scan.
Blood samples were collected from the coccygeal vein of 10 randomly-selected cows in each group on days 0, 14, 28, and 56 after calving. Blood samples were immediately transferred to a dairy laboratory and centrifuged at 2500 × g for 15 min. Serum samples were frozen for blood analysis at −60 °C and used for analysis of non-esterified fatty acids (NEFA), beta-hydroxy butyrate (BHBA), insulin, glucose, alanine aminotransferase (ALT) and aspartate transaminase (AST) using standard kits as detailed in the online Supplementary File.
Data of clean test (healthy or infected uterus) and incidence of ovarian cysts was recorded by the ultrasound machine. To investigate the reproductive parameters of cows, the estrous cycle of all cows was synchronized using the Pre-Synch-Ovsynch protocol (Buhecha et al., Reference Buhecha, Dhami, Hadiya, Patel, Parmar and Killedar2015; Borakhatariya et al., Reference Borakhatariya, Panchal, Dhami, Hadiya and Kalasariya2017) from day 35 postpartum. This protocol lasted about 5 weeks and 16 h after the injection of the last hormone, the cows received artificial insemination. Then, data on the reproductive parameters of cows including parturition interval to first insemination, open days, number of insemination per pregnancy, and percentage of pregnancy at first insemination were recorded.
Statistical analysis
Data were analyzed using a completely randomized design with the factorial method. SAS software (SAS software, version 9.1.3, SAS Institute Inc., Cary, NC) with the mixed procedure and repeated measurements method was used to analyze data of colostrum, milk, blood parameters, BCS changes, open days, parturition interval to first insemination, number of insemination per pregnancy and percentage of pregnancies at first insemination. The analysis of data of clean test and cystic ovarian was used of the Genmod method. The statistical model was:
$$\eqalign{Y_{{\rm ijklm}}\,{\rm} &= {\rm \mu }\,{\rm} + D_{\rm i}\,{\rm} + B_{\rm j}\,{\rm} + D_{\rm i}\,\times \,B_{\rm j}\,{\rm} + T_{\rm k}\,{\rm} + P_{\rm l}\,{\rm} + {\rm Animal}\,{\rm} + {\rm \beta }_ 1\,{\rm} \cr & \quad + e_{{\rm ijklm}}}$$Where Y ijklm is the dependent variable, μ is the overall mean, D i is the effect of the dry period, D i × B j is the interaction of the dry period and BCS, T k is the effect of sampling time, P l is the effect of parity, Animal is the random effect of cows, β1 is the regression coefficient of previous milk yield (305 DIM), and e ijklm is the random residual effect. A significant effect was declared at P ≤ 0.05 by the Tukey–Kramer test.
Results
Colostrum production and composition
The results for the volume and composition of the first colostrum are shown in Table 1. Overall, short dry period cows produced significantly less colostrum of a lower fat content. There was an interaction between dry period and BCS whereby NH cows performed better than NM cows, but SH cows had lower colostrum yield and fat content than SM. Dry period, BCS, and their interactions had no significant effect on the other colostrum quality parameters (protein, lactose, solids-not fat, total solids and Brix index).
Table 1. Effects of shortening the dry period in cows of different body condition score on the volume and composition of colostrum and mature milk in Holstein cows
NH, normal dry period and high BCS; NM, normal dry period and moderate BCS; SH, short dry period and high BCS; SM, short dry period and moderate BCS; N, normal dry period; S, short dry period.
Values are mean ± se
Values are expressed as mean ± se, Different letters (a, b) indicate significant differences (P ≤ 0.05).
Milk production and composition
Results of milk production and composition are reported in Table 1. Short dry periods cows produced significantly less milk but both fat and protein contents were increased relative to normal dry period cows. The highest and lowest milk production values were associated with NM and SH cows, respectively.
Blood parameters
Serum concentrations of insulin, glucose, NEFA, BHBA, ALT, and AST are shown in Table 2 and online Supplementary Fig. S1. The only overall differences between short and normal dry periods were in NEFA and BHBA, both of which were higher after a normal dry period. NEFA (but not BHBA) was higher in moderate BCS cows irrespective of dry period length and the lowest concentrations of NEFA and BHBA were found in SH and |SM cows, respectively. In addition, there were some other differences at individual time points. Insulin concentration at day 14 after calving was significantly (P < 0.05) higher in the groups with a short dry period compared to those with a normal dry period and was higher (P < 0.05) in SM than NM throughout the study. Blood glucose was affected by the treatments only on the 28th day of lactation when SM had higher values (P < 0.05) than NM. There was no significant difference between the concentrations of ALT and AST on any of the sampling days or overall.
Table 2. Effects of shortening the dry period in cows of different body condition score on blood metabolites in Holstein cows
NH, normal dry period and high BCS; NM, normal dry period and moderate BCS; SH, short dry period and high BCS; SM, short dry period and moderate BCS; N, normal dry period; S, short dry period.
aNEFA, non-esterified fatty acids; BHBA, beta hydroxy butyric acid; ALT, alanine aminotransferase; AST, aspartate transaminase.
Values are mean ± se.
Values are expressed as mean ± se, Different letters (a, b) indicate significant differences (P ≤ 0.05).
BCS changes
Data related to BCS changes are shown in Table 3. During the dry period, NH and SH cows showed little change in BCS whereas NM and SM cows both gained condition (significant difference between H and M, P < 0.01) This would have diluted the difference between the groups at parturition. The loss of BCS in early lactation (to day 28) and throughout the measurement period (to day 56) was less in short dry period cows and least in SM. This difference between H and M was only observed after a short dry period. Considering the entire period from drying off to 56 d postpartum, cows that started with high BCS lost more condition, as did cows that had a normal dry period.
Table 3. Effects of shortening the dry period in cows of different body condition score on body condition score changes in Holstein cows
NH, normal dry period and high BCS; NM, normal dry period and moderate BCS; SH, short dry period and high BCS; SM, short dry period and moderate BCS; N, normal dry period; S, short dry period.
Values are mean ± se
Values are expressed as mean ± se, Different letters (a, b) indicate significant differences (P ≤ 0.05).
Reproductive parameters
Results of reproductive parameters are shown in Table 4. Short dry period significantly decreased days open, interval to first estrus and number of insemination per pregnancy. Days open and services per conception were also numerically lower in both NM and SM compared to their respective high BCS group.
Table 4. Effects of shortening the dry period in cows of different body condition score on reproductive parameters in Holstein cows
NH, normal dry period and high BCS; NM, normal dry period and moderate BCS; SH, short dry period and high BCS; SM, short dry period and moderate BCS; N, normal dry period; S, short dry period.
Values are mean ± se.
Values are expressed as mean ± se, Different letters (a, b, c) indicate significant differences (P ≤ 0.05).
Discussion
Our results showed that reducing the length of the dry period reduced the volume of colostrum and percentage of colostrum fat. According to previous studies, this reduction can be caused by the reduction of secretory cell number and functionality as a consequence of less time for mammary redevelopment (Annen et al., Reference Annen, Collier, McGuire and Vicini2004; Rastani et al., Reference Rastani, Grummer, Bertics, Gümen, Wiltbank, Mashek and Schwab2005). In agreement with our results, Amini (Reference Amini2006) showed that reducing the length of dry period decreased the volume of colostrum. The amount of colostrum immunoglobulin production varies considerably among cows. However, it has been shown that there is no relationship between the volume of colostrum and the concentration of its immunoglobulins (Amini, Reference Amini2006). Therefore, in the present study, unlike colostrum volume, the Brix index was not affected by the treatments. Lactose is the major osmolar component in milk and hence its concentration is relatively stable once lactation is established. During the colostrum phase, mammary tight junctions (TJ) are leaky and lactose will be lost by passive diffusion from the alveolar space into the circulation, so its concentration in colostrum is not directly related to secretion. This explains why it was unaffected by the treatments (Davis and Drackley, Reference Davis and Drackley1998). Stott et al. (Reference Stott, Fleenor and Kleese1981) showed that high concentration of colostrum protein is due in large part to the presence of immunoglobulins, once again as a consequence of paracellular flux through the leaky TJ. Variation in the secretory capacity of the mammary epithelium will not influence this passive movement, so once again the lack of treatment difference is to be expected. In general, it can be concluded that a short dry period, due to the reduction in amount of colostrum and reduction in its fat percentage, probably improves NEB at the beginning of lactation (Nogalski et al., Reference Nogalski, Wroński, Lewandowska and Pogorzelska2013).
Differences in milk production were relatively modest, although the lowest milk production was observed in SH cows. Previous studies have shown that decreasing the length of the dry period decreases milk production after calving, however, when cows are dried off later the economic loss of milk production at the beginning of milking will be compensated by the additional revenue from selling late lactation milk. Chebel et al. (Reference Chebel, Mendonça and Baruselli2018) showed that increased loss of BCS can lead to uterine diseases and decreased milk production and in this regard the loss of condition was greater in SH than in SM. Intensification of NEB and reduction of blood glucose concentration can be another factor for the observed reduction of milk yield in the SH group. In addition to decreased milk yield, SH cows also had the highest protein content. In line with this result, Grummer and Rastani (Reference Grummer and Rastani2004) reported that there is an inverse relationship between milk production and milk protein content in cows with a short dry period.
Glucose and insulin were numerically (non-significantly) higher in SM than in other cows. Initial changes may have been due to the reduction in volume of colostrum (and hence NEB) seen in this group, but that cannot explain the longer term changes: these cows did not have reduced milk yield. Andersen et al. (Reference Andersen, Madsen, Larsen, Ingvartsen and Nielsen2005) reported that blood concentrations of insulin and glucose in cows with the normal dry period (7 weeks) in first 5 weeks of lactation were lower than in cows that had no dry period. Weber et al. (Reference Weber, Losand, Tuchscherer, Rehbock, Blum, Yang, Bruckmaier, Sanftleben and Hammon2015) also showed that plasma concentration of glucose was higher in cows with a 28-day dry period than cows with a 90-day dry period. On the other hand, in the study of Meikle et al. (Reference Meikle, Kulcsar, Chilliard, Febel, Delavaud, Cavestany and Chilibroste2004), it was found that condition score did not have a significant effect on blood insulin concentration. It has been reported that high BCS through leptin secretion can exacerbate NEB and decrease insulin and glucose (León et al., Reference León, Hernández-Cerón, Keisler and Gutierrez2004). Our findings are broadly in agreement with the overall consensus from these earlier studies.
NEFA and BHBA concentrations were higher after a normal dry period than a short one. Although the SH group had the lowest concentration of NEFA, the lowest concentration of BHBA was observed in cows with a short dry period and a moderate BCS. In this way, it can be said that cows with short dry periods and moderate BCS had a better state of energy balance. These results are consistent with findings of van Knegsel et al. (Reference van Knegsel, van der Drift, Čermáková and Kemp2013) who showed cows without dry periods or short dry periods had lower concentrations of NEFA after calving than cows with a normal dry period. Andersen et al. (Reference Andersen, Madsen, Larsen, Ingvartsen and Nielsen2005) reported that the concentration of NEFA and BHBA in cows with the normal dry period (7 weeks) was higher than in non-dry period cows. Barletta et al. (Reference Barletta, Maturana Filho, Carvalho, Del Valle, Netto, Rennó, Mingoti, Gandra, Mourão and Fricke2017) showed that the increase in BCS loss after calving causes an increase in the concentration of NEFA and BHBA. Finally in terms of metabolism, we measured ALT and AST as a precaution since they are indicative of liver damage (Nogalski et al., Reference Nogalski, Wroński, Lewandowska and Pogorzelska2013). The lack of difference would suggest that liver function remained normal in all cows.
The results showed that reducing the dry period decreased postpartum BCS loss, which suggests that NEB was improved. These results are consistent with the results of reduced concentration of NEFA and BHBA after a short dry period. Interpretation of differences in postpartum loss of BCS relative to the starting BCS is not straightforward, since both NM and SM cows gained condition during the dry period. Whilst NM lost as much condition as NH in the early postpartum period, SM lost numerically (non-significantly) less than SH, which may relate to the prepartum deposition of reserves being less in this group (almost inevitably, given that it was a shorter dry period). Overall, and based on changes in metabolic indices as well as BCS, it can be said that shortening the dry period had beneficial effects on postpartum energy balance. This is consistent with findings of Rastani et al. (Reference Rastani, Grummer, Bertics, Gümen, Wiltbank, Mashek and Schwab2005) who reported cows without dry periods or with short dry periods had a NEB lower than cows whit normal dry periods.
In agreement with our results, some researchers have stated that a NEB delays the first ovulation and the first estrus postpartum (Canfield and Butler, Reference Canfield and Butler1991; De Vries et al., Reference De Vries, Van Der Beek, Kaal-Lansbergen, Ouweltjes and Wilmink1999). Watters et al. (Reference Watters, Wiltbank, Guenther, Brickner, Rastani, Fricke and Grummer2009) reported that a short dry period reduced the parturition interval to first ovulation and increased fertility in cows. A short dry period and moderate BCS improved reproductive status, which was associated with improved energy balance by lowering the concentration of NEFA and BHBA and increasing the concentration of glucose and insulin in blood, and decreasing the loss of BCS during the experiment. Cows with high BCS may need more inseminations per pregnancy (Ruegg et al., Reference Ruegg, Goodger, Holmberg, Weaver and Huffman1992). Grummer (Reference Grummer2007) showed cows without dry periods had a higher percentage of pregnancy at first insemination and a lower number of inseminations per pregnancy, as well as fewer open days compared to cows with a normal dry period.
In conclusion, reducing the length of the dry period decreased the amount of colostrum and milk after calving. Comparison of postpartum changes in metabolic parameters and BCS support the notion that NEB was improved after a short dry period, perhaps as a result of the reduced yield. Improvements were greater in cows that had a lower starting BCS and there was some evidence of this feeding through into improved reproductive success.
Supplementary material
The supplementary material for this article can be found at https://doi.org/10.1017/S0022029923000766
Acknowledgments
The authors express their kind appreciation to FKA Dairy Co. and its management team for facilitating this study.
