Feed and Nutrient Intake:
The feeding TMR supplemented with 40g/day RPC resulted in daily significantly lower intake of 2.44 kg dry matter (DM), 1.46 kg total digestible nutrients (TDN), 0.35 kg crude protein (CP) and 0.07 kg ether extract (Table.2) of cows compared to control. The dry matter intake-DMI of cows on periodical basis (Fig. 1) shown trend of increase and declining was sharp in control and milder in RPC supplemented group. DMI of cows of RPC group remained lower throughout experimental periods.
The dry matter intake of RPC group cows was low (13.57 ± 0.26 vs. 16.01 ± 0.27kg/day; P = 0.039) and body condition score was high (3.47 ± 0.05 vs. 3.23 ± 0.08; P = 0.012) in present experiment, this finding was in accordance with Hartwell et al. (2020) who reported significantly lower post-partum dry matter intake in high BCS cows compared to low BCS cows. The efficient liver function by reducing fatty liver condition during peri-partum period on supplementation of RPC (Cooke et al., 2007) in dairy cows might be the reason for lower DMI. As during transition period of dairy cows has fatty liver and RPC supplementation reduce deposition of fat and increase VLDL mobilization genes expression (Abbasi et al., 2017), mobilized fat can be utilized for energy required by body and milk synthesis.
Contrary to present study, non-significant influence on dry matter intake was reported on daily feeding rumen protected choline (Elek et al., 2008; Potts et al., 2020; Hartwell et al., 2020) in dairy cows. The meta-analysis revealed RPC did not impact DMI and appetite in dairy cows (Jayaprakash et al., 2016) in dairy cows. The study of Zom et al. (2011) and meta-analysis of Arshad et al. (2019) indicated higher dry matter and net energy intake on choline supplementation in lactating cows. DMI reported in present experiment was of whole 294 days lactation while most researches referred only measured DMI during RPC feeding period. So, it is interesting to investigate effect on intake for total lactation.
Milk and Component:
The yield of milk, 4% FCM and milk components are presented in Table 2. Whole milk yield during entire lactation (1–21 Bi-weekly period) and initial period (1–8 Bi-weekly period) and well as 4% FCM yield during initial period (1–8 Bi-weekly period) has shown numerical (P > 0.05) improvement on 40 g/day RPC supplementation. The daily 40 g supplementation of RPC resulted in significantly (P < 0.05) higher residual whole milk yield (9–21 Bi-weekly period), 4% FCM yield during entire lactation (1–21 Bi-weekly period) and residual period (9–21 Bi-weekly period) by 1.69, 1.19, 1.85 kg/day, respectively. This was also reflected in Fig. 2. A significant (P < 0.05) improvement was also noted in yield of milk solid not fat and total solid of cows daily fed 40g RPC, while yield of milk fat, milk lactose and milk protein was also better (P > 0.05). The milk fat, SNF, TS, lactose and protein content (%) was not influenced (P > 0.05) by supplemental feeding of RPC to dairy cows.
Table 2
An intake, milk and components yield and feed efficiency of cows
Parameter
|
T1 Control
|
T2 RPC
|
P Value
|
Intake
|
DM kg/day
|
16.01 ± 0.27
|
13.57 ± 0.26
|
0.039
|
TDN kg/day
|
9.07 ± 0.17
|
7.61 ± 0.13
|
0.040
|
CP kg/day
|
1.91 ± 0.04
|
1.56 ± 0.03
|
0.034
|
EE kg/day
|
0.46 ± 0.01
|
0.39 ± 0.01
|
0.043
|
Milk yield
|
Whole milk kg/day (1–21 Biweekly period)
|
9.71 ± 0.48
|
10.61 ± 0.32
|
0.118
|
Initial whole Milk kg/day (1–8 Bi-week)
|
13.59 ± 0.67
|
13.20 ± 0.37
|
0.609
|
Residual whole Milk kg/day (9–21 Bi-week)
|
7.33 ± 0.53
|
9.02 ± 0.39
|
0.011
|
4% FCM kg/day (1–21 biweekly period)
|
9.80 ± 0.48
|
10.99 ± 0.33
|
0.042
|
Initial 4% FCM kg/day (1–8 B-week)
|
13.63 ± 0.66
|
13.73 ± 0.36
|
0.893
|
Residual 4% FCM kg/day(9–21 Bi-week)
|
7.45 ± 0.54
|
9.30 ± 0.41
|
0.007
|
Milking days
|
273.25 ± 14.39
|
282.13 ± 11.31
|
0.635
|
Fat yield kg/day
|
0.401 ± 0.02
|
0.446 ± 0.01
|
0.056
|
SNF yield kg/day
|
0.853 ± 0.04
|
0.953 ± 0.03
|
0.048
|
TS yield kg/day
|
1.254 ± 0.06
|
1.399 ± 0.04
|
0.049
|
Lactose yield kg/day
|
0.472 ± 0.02
|
0.520 ± 0.02
|
0.080
|
Protein yield kg/day
|
0.309 ± 0.01
|
0.344 ± 0.01
|
0.055
|
Milk components
|
Fat%
|
4.28 ± 0.27
|
4.25 ± 0.17
|
0.911
|
SNF%
|
8.88 ± 0.14
|
9.02 ± 0.11
|
0.461
|
TS%
|
13.17 ± 0.39
|
13.26 ± 0.26
|
0.845
|
Lactose%
|
4.91 ± 0.06
|
4.93 ± 0.05
|
0.895
|
Protein%
|
3.23 ± 0.05
|
3.26 ± 0.04
|
0.650
|
Where RPC = Rumen protected choline, DM = Dry matter, TDN = Total digestible nutrients, CP = Crude protein, EE = Ether extract, FCM = Fat corrected milk, SNF = Solid not fat, TS = Total solid |
The feeding of 55 g/d RPC form − 30 days to + 60days of calving to Karan Fries cows resulted in significantly increased milk yield, 4% fat corrected milk yield, milk fat, and total solid content and effect on milk protein, lactose, and solids not fat (SNF) content was non-significant (Acharya et al., 2020). The milk yield improvement also reported by Potts et al. (2020), Soltan et al. (2012) and Mohsen et al., (2011) on supplementation rumen-protected choline in the diet of lactating cows. Holstein cows produced higher milk and non-significant effect on milk composition (Xu et al., 2006; Pinotti et al., 2004) on feeding rumen protected choline. Meta-analysis on choline supplementation (Arshad et al., 2019) shown 1.6 and 1.7 kg/d increase in milk and energy corrected milk, respectively as well as increase yield of milk fat and milk protein on supplementation of choline 12.9 g/d in dairy cows while milk fat, protein and lactose content (%) was not significantly affected. The report of research mentioned above were in line with present finding. The improvements in yield in present research, was attributed to more milking days of cows supplemented with rumen protected choline. An improvement in milk yield with RPC supplementation may be attributed to higher TVFA and lower NH3-N concentration in the rumen, improved nutrient digestibility, improved lipid metabolism and export from liver metabolism (Mohsen et al., 2011) and RPC acted as a methyl group donor sparing the methionine which can be utilized for the more milk production in dairy cows (Acharya et al., 2020). Contrary to present finding, Hartwell et al. (2020), Pawar et al. (2015) and Leiva et al. (2015) reported non-significant effect on milk production when Holstein cows fed supplemental RPC during variable peri-partum period.
Reproductive Performance:
The feeding of rumen protected choline to dairy cows resulted in significant (P < 0.05) reduction in number of artificial insemination (0.429) to conception and also significant (P < 0.05) reduction of service period by 69.25 days compared to control group of cows. The calf weight was only 1.321 kg lower in rumen protected choline group than control even though having higher ratio of female to male in supplemental group.
The supplemental choline supports cow to minimized the negative energy, improves follicular development and fertility (Pirestani and Aghakhani, 2018) and improved hormones production like follicular stimulating hormone-FSH and luteinizing hormone-LH (Evans et al., 2006) leads to improve reproduction parameters.
Similarly, Ardalan et al. (2010) indicated significant (P < 0.05) reduction in open day (115.4 vs. 106.6) and service per conception (3.0 vs. 2.4) in Holstein dairy cows on feeding 18g/day rumen protected choline from − 4 to 20 weeks of calving. Pirestani and Aghakhani (2018) also reported lesser service/conception (1.79 ± 0.6 vs. 2.50 ± 0.6), days open (82.21 ± 14.0 vs. 90.07 ± 17.8) in Holstein cows fed 60g/d rumen protected choline for period of -1 to 4 weeks calving.
Body Conditions Score (BCS) and Milk Yield:
The decline in body condition score-BCS of cows (Fig. 2) was sharp up to 14 days post-partum and then milder decline was noticed up to 49 days post-partum in control group. BCS of cows of RPC supplemented group showed milder decline in comparison to control group. BCS of RPC group cows remained on higher side throughout experiment. The milk yield curve (Fig. 3) of RPC group cows showed higher persistency compared to the cows of control group. Residual milk yield of RPC group cows after supplementation was higher than control group cows.
The supplemental RPC experienced only milder declines in BCS, higher persistency of milk yield that might have diverted the more energy to reproductive need as indicated by lower AI/conception and service period. The loss of BCS has more consequences on reproduction than of the absolute value and loss below one point has modest effect on reproduction (Souissi and Bouraoi, 2019). The higher loss of BCS also results in lower milk production (Souissi and Bouraoi, 2019) of dairy cows. The efficient utilization of nutrients for milk production during initial lactation and more deposition of fat during later lactation shown in this experiment owing better liver function which central to optimum metabolism in dairy cows. Similarly, Elek et al. (2008) reported rapid loss of BCS from 7 to 35 days after calving, which were 0.83 and 0.68 in the control and RPC groups of Holstein cows, respectively with non-significant higher BCS of cows of RPC supplementation group (25 and 50g during pre and postpartum period, respectively) with higher daily milk yield (41.6 vs. 37.2 kg). The meta-analysis of choline supplementation 0 to 12.9 g/d by Arshad et al. (2019) also revealed positive and linear effect (P = 0.008) on postpartum BCS and 0.09 units increase in body condition score in dairy cows.
Feed efficiency and feed economics:
The feed conversion efficiency (Table 3) of cows fed rumen protected choline was improved significantly (P < 0.05) compared to control group. The cows consumed 0.633 and 0.576 kg less dry matter to produce one kg of whole and 4% fat corrected milk, respectively. The requirement of total digestible nutrients was 0.326 and 0.299 kg less for the same. The daily feeding cost of cows fed supplemental rumen protected choline was 7.361 Rs. lower (P < 0.05) to produce each kilogram of milk. The daily feed cost was 16.06 Rs. lower in RPC supplemented group compared to control. The return over feed cost was Rs. 44.81/cow higher on feeding RPC and same on per cent basis was 39.48% higher.
Table 3
Reproductive performance and feeding economic of cows
Parameter
|
T1 Control
|
T2 RPC
|
P Value
|
BCS
|
3.23±0.08
|
3.47±0.05
|
0.012
|
Reproduction
|
AI/conception
|
2.286±0.18
|
1.857±0.14
|
0.008
|
Service period days
|
177.38±20.92
|
108.13±20.73
|
0.024
|
Calf weight kg
|
29.150±1.91
|
27.838±1.12
|
0.194
|
Female to male ratio
|
5:3
|
7:1
|
|
Feeding Economics
|
Feed cost Rs./kg milk
|
25.228±0.699
|
17.867±0.258
|
0.002
|
Milk value Rs./cow/day
|
293.13±51.23
|
321.88±36.47
|
0.650
|
Feed cost Rs./cow/day
|
179.63±15.60
|
163.57±10.81
|
0.342
|
Return over feed cost (ROF) Rs./cow/day
|
113.50±41.78
|
158.31±27.34
|
0.462
|
Feed cost to Milk income ratio
|
1.00:1.63
|
1.00:1.97
|
|
ROF Over control Rs./cow/day
|
|
+44.81
|
|
% ROF over control
|
|
39.48
|
|
Feed efficiency
|
Kg DM/kg milk
|
2.032±0.06
|
1.399±0.08
|
0.033
|
Kg DM/kg FCM
|
1.921±0.03
|
1.345±0.08
|
0.014
|
Kg TDN/kg milk
|
1.133±0.09
|
0.807±0.06
|
0.042
|
Kg TDN/kg FCM
|
1.071±0.01
|
0.772±0.01
|
0.015
|
Where RPC= Rumen protected choline, AI= Artificial insemination, ROF= return over feed cost, DM= Dry matter, TDN= Total digestible nutrients, FCM= Fat corrected milk |
Amrutkar et al. (2015) reported improved feed efficiency in terms of dry matter (0.66 ± 0.02 vs. 0.80 ± 0.02 kg/kg FCM), crude protein (100.68 ± 3.77 vs. 130.18 ± 1.75 g/kg FCM) and metabolizable energy (1.61 ± 0.03 vs. 2.00 ± 0.03 Mcal/kg FCM) of crossbred (Karan-Fries) cows fed RPC 40 g/d from − 40 to + 120days of calving. Similarly, feeding of 30g/d rumen protected choline from calving to 12 weeks in milk resulted in improved milk to feed ratio (1.60 ± 0.01 vs. 1.56 ± 0.28) in Holstein cows (Soltan et al., 2012). Meta-analysis on choline supplementation (Arshad et al., 2019) also shown improved milk yield efficiency (1.96 ± 0.07 vs. 1.84 ± 0.07 ECM/DMI, P = 0.001) on supplementation of choline 12.9 g/d in dairy cows. Lower intake of nutrients and better milk production in current experiment, resulted in improved feed efficiency for milk production in dairy cows.