Effects of milking frequency on feed intake, body weight and haemato-biochemical changes in crossbred cows

Abstract

An experiment was conducted to compare the effects of two times and three times daily milking frequencies on feed intake, body weight and haemato-biochemical changes in crossbred cows. Twenty-four cows of second to fourth parity were distributed into two groups on the basis of genetic makeup and parity. The cows of control group (T1) were hand milked twice a day with 12 hours interval and of the other group (T2) thrice daily with 8 hours interval. All the animals were housed under tie stall system of housing. The parameters were recorded from 7th to 104th day of lactation on individual animal. No significant difference was observed for total dry matter intake between the groups. The gain in body weight per cow was 20.00 and 8.75 kg in T1 and T2, respectively without significant difference. Body condition score change was 0.02 and −0.06 units in cows of T1 and T2, respectively. Haemoglobin, packed cell volume, albumin, calcium and T₃ values were found significantly (P<0.05) higher in T1 than in T2. It is concluded that more frequently milked cows produced more milk at the cost of their body reserves, expressed by their comparative poor body condition, and had lower values of some blood metabolites.

Keywords:

• body weight
• crossbred cows
• feed intake
• haemato-biochemical
• milking frequency

1. Introduction

Traditionally, the cows have been milked twice daily. Frequent milking (three or more times daily) of dairy cows has emerged as an effective management tool for dairy farmers to increase milk production efficiency (Wall and Mc Fadden 2008). With increased milking frequency, the physiological capacity of the udder is utilised more effectively and milk yield can be increased by 5–25%. The best overall response of increased milking frequency was reported from the cows in early to mid lactation. The primary cause of increased milk yield is reduced intra-mammary pressure, due to more frequent milk removal. Wilde et al. (1995) hypothesised that increased milk yield, as a result of increased milking frequency was due to the removal of a whey protein, referred to as the feedback inhibitor of lactation, from the mammary gland.

The transition from pregnancy to lactation is marked by metabolic, hormonal and immunological changes that have an impact on the incidence of infectious and metabolic diseases (Loiselle et al. 2009). Murphy et al. (2005) found that cows milked once daily were in less (P<0.05) negative energy balance than cows milked thrice daily in the early lactation, while Barnes et al. (1990) did not observe significant change in mean body weight upon alteration in milking frequency. Possible negative effects of three times milking for cows would be the greater loss in body weight and depletion of metabolites throughout the lactation. Keeping these views in mind, the experiment was planned to study the effects of different milking frequencies on growth performance and haemato-biochemical changes in crossbred cows.

2. Materials and methods

The present study was conducted at Livestock Production Management section, Indian Veterinary Research Institute, Izatnagar. Twenty-four crossbred (Holstein Friesian×Hariana, Holstein Friesian×Brown Swiss×Hariana and Holstein Friesian×Jersey×Hariana) cows were distributed into two groups, having 12 animals in each group on the basis of genetic makeup and parity. The milk yield of these cows varied between 2710 and 2906 kg during previous lactation (305 days basis). The cows were introduced into the experiment after three days of colostrum milking. One group (T1) was milked twice a day and the other (T2) thrice a day. Milking intervals were kept similar within the group, that is, 12 hours intervals in T1 (milking at 4 am and 4 pm) and 8 hours in T2 (milking at 4 am, 12 noon and 8 pm). Two experienced milkers with almost equal efficiency and age were selected for milking. All the cows were hand milked in their own shed. These animals were housed in tail to tail arrangement, under tie stall system of housing. Each cow was accommodated in 4.5 sq.m. floor space of covered area. The animals were kept in open paddock during night hours and two times in the day for heat detection. The cows were offered green fodder (maize and sorghum) ad libitum in weighed quantity (approximately 50 kg/day/animal). Concentrate mixture (crude protein-21%, TDN-70%) was given as per recommendations of ICAR (1998). Green fodder was offered twice daily, that is, at 11.00 am and 4.00 pm. The concentrate mixture was also offered twice daily, before morning milking and at 10.00 am in both the groups. Fresh and clean potable water was offered thrice during the day time (morning, noon and evening) and was free in access to all the animals during night. Recording of parameters was done from seventh day of their lactation after 3 days of adjustment period up to seventh fortnight. The milk produced by individual cow was weighed on digital electronic balance at every milking throughout the experimental period. The samples of feed (roughage and concentrate) offered and of residues were collected fortnightly, and dried at 96±5°C temperature in the hot air oven for 24 hours to determine dry matter intake (DMI). The body weight of each cow was recorded after milking and before feeding and watering in the morning at weekly interval. These animals were weighed on cattle weigh bridge having 1500 kg capacity with least count of 5 kg. All the animals were assessed for their body condition by using body condition scoring technique developed for crossbred cows by Prasad et al. (2008). Scoring (1–6 point) of body condition was performed fortnightly by considering the following points:

1.	Vertebral column (chine, loin and rump region)
2.	Transverse process of lumbar vertebra
3.	Ribs
4.	Overhanging shelf-effect
5.	Pelvis
6.	Tail head region

The blood samples were collected in 2nd, 8/9th and 15th week of lactation. The separated serum and plasma samples were preserved at −20°C temperature. The haemoglobin (Hb) concentration by cyanmet-haemoglobin, glucose by glucose oxidase/peroxidase, total protein by biuret, albumin by bromo-cresol green dye binding, calcium by orthocresolphthalin complexon, phosphorous by gomorri, total tri-iodothyronine (T₃) and total thyroxine (T₄) by radioimmunoassay method were estimated. The data generated were analysed using T-test (Snedecor and Cochran 1994).

3. Results and discussion

The total milk produced was 15.63% higher (P>0.05) from cows milked three times daily over cows milked two times daily. The mean daily milk yield during experimental period was 11.02±0.87 and 12.74±0.80 kg for the cows in T1 and T2, respectively (Figure 1). Present findings of higher milk yield by cows milked frequently agreed with other studies (Allen et al. 1986; Hale et al. 2003; Eslamizad et al. 2010).

Figure 1.  Weekly means of daily milk yield (kg).

The means of daily DMI are presented in Figure 2. Average DMI through roughage increased from 4.63±0.58 and 4.20±0.43 kg in first fortnight to 8.05±0.47 and 7.53±0.45 kg in seventh fortnight of the experiment by the cows of T1 and T2, respectively. Similarly, daily DMI through concentrate increased from 5.67±0.33 and 5.68±0.34 kg in first fortnight to 6.03±0.40 and 6.64±0.34 kg in seventh fortnight. The average daily DMI through concentrate and total DMI did not differ (P>0.05) between the groups. However, during fourth and sixth fortnight, the DMI through roughage was higher (P<0.01 and P<0.05, respectively) in the cows of T1. No significant difference was observed for DMI of concentrate between two groups. Total DMI was 13.07±0.43 and 13.03±0.37 kg per day per cow in T1 and T2, respectively.

Figure 2.  Fortnightly means of daily dry matter intake (DMI) (kg).

An increasing trend was observed for total DMI in both groups, but it was not affected by milking frequency, agreeing with previous reports (Amos et al. 1985;Barnes et al. 1990). Even though cows were allowed ad libitum DMI, the T2 cows did not respond to the increased energy demand associated with increased yield by consuming more ration. However, Pearson et al. (1979) reported a slightly higher but non-significant feed intake, for cows in early lactation milked two times daily compared with cows milked three times daily.

Weekly mean body weight changes are presented in Figure 3. The mean initial body weight per cow was 393.75±15.51 and 392.92±16.15 kg in T1 and T2, respectively. Whereas, the mean body weight gain per cow was 20.00±6.06 and 8.75±5.04 kg in T1 and T2, respectively, without significant difference at the end of the experiment.

Figure 3.  Weekly body weight (kg) changes.

The body weight changes of the animals were observed in decreasing order in T1 up to seventh week and in T2 up to eighth week of their lactations and later these animals started gaining significantly in their body weight. The study revealed less body weight gain in T2 in comparison to T1 and the fact might be due to more body tissue catabolisation for higher milk production in T2. Body weight of mature cows (two times and three times milked daily) decreased for the first four weeks of lactation and then increased steadily to the end of 43 weeks (Amos et al. 1985). Thus, in agreement with prior reports, it appeared that increasing milking frequency resulted in either preferential utilisation of nutrients for milk production or a higher rate of tissue catabolisation (Barnes et al. 1990), resulting in higher body weight loss. Rao and Ludri (1984) recorded significant increase in body weight of 18.1 kg in two times milked cows, when compared with slight increase in body weight of 8.23 kg in three times milked cows for 81 days of experiment in early lactation.

Table 1 demonstrates fortnightly changes of body condition scores (BCS). The cows under T1 and T2 reached their lowest BCS of 3.01±0.18 and 2.91±0.16 units in the forth fortnight of experiment, after which they started to gain the BCS. There was a net change of 0.02±0.06 and −0.06±0.05 units in the BCS of T1 and T2, respectively without any significant difference. Similar pattern was recorded by Wildman et al. (1982), who observed an initial fall in BCS during early lactation and then a slower recovery from approximately peak lactation. Recovery rate in group T2 was slower in comparison to T1. It can be inferred from these results that the cows that were milked three times daily had a slight deterioration in body condition because of more body tissue catabolisation for increased milk production. These findings were in agreement with the statements of Fournier (1997) and Dolezal et al. (1999).

Table 1. Fortnightly changes in body condition score.

	Groups
Fortnights	T1 (milked twice daily)	T2 (milked thrice daily)	SEM
1	3.14±0.22	3.08±0.15	0.13
2	3.13±0.21	2.92±0.19	0.14
3	3.05±0.20	2.92±0.17	0.13
4	3.01±0.18	2.91±0.16	0.12
5	3.09±0.20	2.93±0.16	0.13
6	3.14±0.21	2.95±0.16	0.13
7	3.16±0.20	3.02±0.15	0.12
SEM, Mean of standard errors.

Haemato-biochemical variables at the different stages of lactation are presented in Table 2. All the values of Hb and packed cell volume (PCV) were within the normal physiological range in both the groups. The mean Hb and PCV values were significantly (P<0.05) higher in T1 than in T2 in 15th week of lactation. The concentration of Hb increased (P<0.05) in T1 but decreased (P<0.05) in T2 towards mid lactation. The mean plasma glucose concentration increased from 2.32 to 2.63 m mol/L in T1 and from 2.33 to 2.54 m mol/L in T2 from first to seventh fortnight of experiment. Mean values of serum total proteins were falling within the normal physiological range in both the groups without any significant difference. Mean serum albumin value in T1 cows was significantly (P<0.05) higher than in the T2 cows in 15th week of lactation. But, mean serum globulin values did not show any trend on increasing milking frequency. Plasma calcium level was towards lower physiological limit, whereas phosphorus was within the normal physiological range in both of the groups. The mean plasma T3 value ranged from 0.99 to 1.32 n mol/L in T1 and 0.93 to 1.17 n mol/L in T2. Total T₃ value was found significantly (P < 0.05) higher in the cows of T1 during 15th week of lactation. No significant difference was found for T₄ between both the groups.

Table 2. Haemato-biochemical variables at different stages of lactation.

	Groups
Attributes and stages of sampling	T1 (milked twice daily)	T2 (milked thrice daily)	Significance
Haemoglobin (g/dL)
I	107.92±2.572	114.00±2.908	NS
II	119.58±3.700	113.50±3.016	NS
III	120.17±3.821^a	106.00±4.187^b	P < 0.05
Packed cell volume (%)
I	0.37±0.007	0.38±0.011	NS
II	0.42±0.012^a	0.39±0.012^b	P<0.05
III	0.39±0.013^a	0.35±0.010^b	P < 0.01
Glucose (m mol/L)
I	2.32±0.087	2.33±0.158	NS
II	2.58±0.051	2.53±0.109	NS
III	2.63±0.097	2.54±0.082	NS
Albumin (g/L)
I	33.83±1.353	33.17±0.968	NS
II	35.17±0.976	33.67±0.801	NS
III	35.50±1.098^a	31.67±1.305^b	P < 0.05
Globulin (g/L)
I	28.25±2.419	29.00±2.440	NS
II	25.83±1.466	26.92±1.807	NS
III	25.33±1.427	29.67±2.057	NS
Calcium (m mol/L)
I	2.26±0.062	2.27±0.044	NS
II	2.24±0.027^a	2.17±0.023^b	P<0.05
III	2.18±0.034	2.16±0.043	NS
Phosphorous (m mol/L)
I	2.20±0.115	2.03±0.094	NS
II	2.19±0.084	2.05±0.096	NS
III	1.91±0.088	1.82±0.099	NS
T3 (n mol/L)
I	0.99±0.06	0.93±0.04	NS
II	1.27±0.07	1.17±0.08	NS
III	1.32±0.08^a	1.08±0.07^b	P < 0.05
T4 (n mol/L)
I	30.63±3.69	26.76±3.28	NS
II	38.83±3.07	33.57±4.26	NS
III	32.17±4.00	32.79±3.51	NS
Stage I = 2nd week, II = 8th/9th week, III = 15th week of lactation.
NS, Non-significant.
Means bearing different superscripts within a row differ significantly.

There are very few reports on metabolic profile test with respect to increased milking frequency in the cows. Increasing the daily milking frequency creates a higher metabolic imbalance in early lactation. Cows milked three times daily had a 6% lower plasma glucose concentration compared with cows milked two times daily (Andersen et al. 2004). Albumin, glucose and Hb values decreased in early lactation with increasing the milk yield while calcium and globulin showed the reverse trend (Rowlands et al. 1975). In the present study, decrease in Hb was found as reported by earlier workers. According to Sivaraman et al. (2004), Hb and PCV were inversely related to milk production at significant level. However, Blum et al. (1983) found no association between milk yield and Hb or PCV. The differences between groups at three stages were not significant, however, increasing rate of glucose level was found slower in T2 than in T1. The plasma glucose concentration was lower in more frequently milked cows (Mc Namara et al. 2008; Loiselle et al. 2009). High milk yield probably drained plasma glucose into mammary gland for lactose production whereas DMI was not increased to the same extent as milk yield to replace drained glucose during the first three months post-partum, resulting in more severe negative energy balance in more frequently milked cows. The mean higher values of tri-iodothyronine (T₃) and thyroxine (T₄) in twice daily milked than in thrice daily milked cows showed negative association between such values and milk yield. Similar findings of associations were also reported by Blum et al. (1983). It might be due to more excretion of thyroid hormones by the mammary gland in the high milk producing cows (Vanjonack and Johanson 1975).

The present study revealed that the cows milked thrice daily produced more milk at the cost of their body reserves. They could not utilise more nutrients for compensating the high quantity of milk produced. This was expressed by their comparative lower body weight gain and lower body condition score at the end of experiment. Hb, PCV, albumin, calcium and T₃ values decreased significantly in more frequently milked crossbred cows. The results of this research work will be useful in further studies to establish frequent milking in cows for long term, without any adverse effect on health.

Acknowledgements

The authors are thankful to the Director, Indian Veterinary Research Institute, Izatnagar for providing necessary funds and facilities during the study.