Background
Demand for milk in Pakistan is rising due to an increasing human population and higher inclination towards consumption of milk and milk products. Milk is the largest commodity amongst dairy products, making Pakistan the 4th largest milk-producing country in worldwide. A total of 49.5 billion kg of milk was produced during the 2012-13 year [1]. Major sources of milk in Pakistan are cattle and buffaloes, as the country is blessed with suitable tropical breeds of dairy cattle. Sahiwal is one such renowned tropical dairy cattle breed due to its excellent heat and tick resistance [2, 3]. As such, the performance of this breed in a tropical environment is also better than other cattle breeds due its better resistance to tick-borne diseases [4].
Cow milking is considered to be one of the most laborious and time-consuming activities at livestock farms. Additionally, considerable cost goes into this major farm operation. As a result, machine milking was invented to improve labor efficiency due to growing costs [5]. Machine milking has been shown to have the potential to increase milk production by up to 12%, reduce labor by up to 18%, and improve dairy cow welfare.
Increasing milking frequency from twice to three times per day may correspondingly increase milk yield from 6 to 25% during complete lactation as well as improve udder health by reducing the somatic cell count (SCC) [6–8]. The chance of clinical mastitis has also been reported to be lower in cows milked three times or more than in those milked only twice per day [9]. Milk yield can be increased by machine milking, which has beneficial effects on udder health [10, 11]. Moreover, milking three times per day has been shown to increase milk yield by up to 14% compared to milking only twice per day [12]. The literature is limited regarding the effects of milking frequency as well as machine milking on milk yield, composition, and udder health of Pakistani cattle. Therefore, this study investigated the optimal milking frequency and milking method for improved production performance in Sahiwal cows.
Methods
The study was conducted at the Livestock Experiment Station Jahangirabad, Khanewal. This station is situated in south central irrigated Punjab, Pakistan. Its geographical coordinates are 30° 18' 0" North, 71° 56' 0" East. Jahangirabad town in Khanewal District is well known as the homeland of Sahiwal cows, a renowned tropical dairy cattle breed in Pakistan [2, 3, 13]).
Twenty-four lactating Sahiwal cows in their 3rd to 4th parity after parturition with similar average bodyweight, conditions, and production performance were separated into groups A, B, C, & D. Cow milking was carried out by the hand and machine milking methods twice or three times a day, as shown in Table 1. The animals were kept for a period of 90 days, excluding a 15-day adjustment period. The cows were also properly tagged and treated for internal and external parasites. All animals were kept in separate pens under identical conditions.
| Treatment groups | Replicates | Milking method | Frequency of daily milking |
|---|---|---|---|
| A | 6 | Manual | Twice |
| B | 6 | Manual | Thrice |
| C | 6 | Machine | Twice |
| D | 6 | Machine | Thrice |
Animals were given standard diet: daily green fodder (Maize) @ 40 kg per cow, wheat straw @ 4 kg per cow, and Anmol wanda (concentrate consisting of CP 16 and 68% TDN) @ 1.0 kg per 2.5 liters of milk produced by each cow. Composition of Anmol Wanda is given in Table 2. Clean premises were made available to the experimental cows, and animals had ad limitum access to fresh clean water.
*100 Kg minerals mixture included DCP 70.81 kg, NaCl 18.91 kg, MgSO4 8.64 kg, FeSO4 0.89 kg, MnSO4 0.49 kg, ZnSO4 0.22 kg, CuSO4 0.03 kg, KI 8.77 g, CoCl2 0.89 g, and NaSiO3 1.50 g.
Cows in groups A & B were subjected to the hand milking method, whereas cows in groups C & D were milked using a portable milking machine. However, groups A & C were milked twice per day at 12-hour intervals at 3:00 and 15:00 hours, whereas groups B & D were milked three times per day at 8-hour intervals at 2:00, 10:00, and 18:00 hours. Prior to milking, the udder of each cow was thoroughly washed with moderate warm water & dried properly. The milking machine was thoroughly washed with acid and alkali solutions in lukewarm water.
Feed intake of each experimental animal was recorded daily. Milk yields of all cows were recorded daily using a calibrated spring balance. To screen for mastitis, a few milk were tested prior to milking. Milk samples were collected from all cows every 2 weeks for milk composition analysis. The following parameters were studied to determine the response to different treatments.
Analyses were performed in the Food & Nutrition and Quality Operation Labs at the University of Veterinary and Animal Sciences (UVAS), Lahore. Dry matter content of feed samples was determined according to the procedures of [14]). Milk composition analysis was carried out using a Lactoscan-S Milk Analyzer (50 W, Milkotronic Ltd., Bulgaria) in WTO-Quality Operation Labs at the UVAS, Lahore for the following milk constituents: milk fat, non-fat solids, milk protein, lactose, and total solids.
Data were analyzed using ANOVA techniques [15] under a Completely Randomized Design (CRD) using SAS 9.1.3 portable software. Differences among treatment means were tested by DMRt. The mathematical model was:
where
Yij = each observation on ith treatment due to jth animal.
μ = overall mean.
τi = effect of ith treatment (Σ τi = 0 and i = 1, 2, 3, 4).
ϵij = random error associated with ith treatment and jth animal with the restriction that variance σ2 and mean zero.
Results and discussion
Dry matter intake (DMI) in cows is shown in Table 3. Cows milked three times daily showed higher DMI compared to those milked twice per day. However, DMI was not significantly different between hand and machine milking methods. The higher DMI consumption of cows milked three times per day can be attributed to higher milk yield, which increases nutrient demands. In support of the current results, [16] previously studied the effects of milking frequency on production efficiency in Holstein cows and found that milking three times daily increased milk yield and DMI. In another study, [17] asserted that DMI increases (p < 0.05) with greater milking frequency. The current results are also supported by previous works ([16, 18, 19]) in which increased DMI was shown to be accompanied by higher milk yield due to greater milking frequency. Milk yield is an indicator of feeding behavior as increased milk yield is positively correlated with DMI [20].
Different superscripts in same row differ significantly (P < 0.05).
Average daily milk yields are presented in Table 3. Milk yield was higher (P < 0.05) in cows milked three times daily compared to cows milked twice. Milk production between the machine and hand milking treatment groups was not significantly different (P > 0.05). However, higher milking frequency significantly (P < 0.05) enhanced milk yield.
Our observation of an association between enhanced milking frequency and greater milk yield has been substantiated by the literature. In a previous study, [7] reported that milk yield increased by up to 10.4% in cows milked three times per day compared to those milked twice per day. Similarly, [21] showed that milking three times daily increased milk yield in cows by up to 18%. In another study, [22] showed that the yield of energy corrected milk was higher in cows milked three times per day compared to those milked twice per day.
Similarly, [23] affirmed that milking three times per day rather than twice increased milk yield in crossbred (different blood ratios among Friesian, Hariana, Brown Swiss, and Jersey breeds) cows, but at the cost of their body condition. The higher milk yield in cows milked three times per day might be due to the fact that milk secretion is a continuous process resulting in gradual elevation of internal udder pressure. Thus, more frequent milking might reduce internal udder pressure and consequently stimulate milk-secreting cells to operate at full capacity for a longer time.
The impacts of milking frequency and method on milk composition in Sahiwal cows are shown in Table 4. Milk fat percentage was higher (P < 0.05) in cows milked twice compared to those milked three times per day. However, milking method did not influence fat percentage in milk. Similarly, the percentage of total solids was higher in milk from cows milked twice per day compared to those milked three times.
Different superscripts in same row differ significantly (P < 0.05).
However, the percentages of protein and lactose in milk were not significantly different (P > 0.05) among cows in the different treatment groups. Milk fat content has been shown to be affected by milking frequency [7, 24, 25]). Similarly, cows milked three times per day produce milk with a lower fat content compared to those milked once a day during early lactation [26]. The negative effect of frequent milking on fat content can be attributed to increased air exposure due to frequent milking, enzymatic activity of fatty acid syntethase, and increased production of short-chain fatty acids [7]. Another factor might be the shortened time for fat synthesis in the case of 8-hour intervals. The high percentage of total solids in milk from cows milked twice daily might be due to a high fat percentage.
