MISCELLANEOUS REPORTS 73 ISSN 0253-6749 THE EFFECTS OF MILKING COWS THREE TIMES DAILY ON MILK YIELD, MILK COMPOSITION AND PROFITABILITY COMPARED TO TWO TIMES DAILY MILKING S. Economides AGRICULTURAL RESEARCH INSTITUTE MINISTRY OF AGRICULTURE, NATURAL RESOURCES AND THE ENVIRONMENT NICOSIA CYPRUS SEPTEMBER 1999
Editor - in Chief Dr A.P. Mavrogenis, Agricultural Research Institute, Nicosia, Cyprus. All responsibility for the information in this publication remains with the author(s). The use of trade names does not imply endorsement of or discrimination against any product by the Agricultural Research Institute. 2
THE EFFECTS OF MILKING COWS THREE TIMES DAILY ON MILK YIELD, MILK COMPOSITION AND PROFITABILITY COMPARED TO TWO TIMES DAILY MILKING S. Economides SUMMARY Two trials were carried out to study the effects of three milkings per day on the total yield and composition of milk in Friesian cows. In the first trial 18 cows in early lactation were allocated to two groups; one group was milked two times (2x) daily and the other three times (3x) daily. The trial lasted 70 days and was divided in three periods. In period I (42 days), cows milked 3x daily produced 6.85 kg more milk daily than cows milked 2x but with lower fat content (3.26 vs 3.58%). In this period, cows milked 3x daily consumed 15.23 MJ day of metabolisable energy more than those milked 2x daily. In period II (43 to 56 days), cows in both treatments were offered the same energy intake, and continued to be milked either 3x or 2x daily as in period I. During this period cows milked 3x daily produced 5.63 kg more milk than those milked 2x daily but of similar fat content. In period III (57 to 70 days), all cows were milked 2x daily. There was a sharp decline in milk yield of cows changed from 3x to 2x milking daily. Milk yield/cow was similar in both treatments. The income minus costs of 3x milking daily in periods I+II together was 76 cent/cow/day more than cows milked 2x daily. trial 2 was carried out in a private farm and used 126 cows in mid lactation. One group was milked 2x daily and the other 3x daily. Cows milked 3x daily produced 2.42 kg/day more milk than cows milked 2x daily. Fat content was significantly lower and lactose content higher, in cows milked 3x compared to those milked 2x daily. The income minus costs of 3x milking daily was 28 cent/cow/day more than cows milked 2x daily. ΠΕΡΙΛΗΨΗ Μελετήθηκε σε δύο πειράµατα η επίδραση του αρµέγµατος 3 φορές την ηµέρα στη γαλακτοπαραγωγή και τη χηµική σύσταση του γάλακτος. Επίσης µελετήθηκε το οικονοµικό όφελος από άρµεγµα 3 ή 2 φορές την ηµέρα. Στο πρώτο πείραµα, 18 αγελάδες, 82 µέρες µετά την έναρξη της γαλακτοπαραγωγής, χωρίστηκαν τυχαία σε 2 οµάδες µε βάση την ηµερήσια γαλακτοπαραγωγή, τη λιποπεριεκτικότητα, τις µέρες γαλακτοπαραγωγής, το βάρος και την ηλικία τους. Η µια οµάδα συνέχισε να αρµέγεται 2 φορές και η άλλη οµάδα αρµεγόταν τρεις φορές την ηµέρα. Το πείραµα διάρκεσε 70 µέρες και χωρίστηκε σε τρεις περιόδους. Στην πρώτη περίοδο (42 µέρες) η ηµερήσια παραγωγή γάλακτος των αγελάδων που αρµέγοντο 3 φορές την ηµέρα ήταν 6.85 χλγ/ζώο µεγαλύτερη από την παραγωγή αγελάδων που αρµέγονταν 2 φορές, αλλά µε χαµηλότερο λίπος (3.26 vs 3.58%). Στην ίδια περίοδο οι αγελάδες που αρµέγονταν 3 φορές την ηµέρα κατανάλωσαν περισσότερη τροφή, ισοδύναµη µε 15.23 MJ µεταβολιστέας ενέργειας την ηµέρα. Στη δεύτερη περίοδο (43 έως 56 µέρες) δόθηκε στις δύο οµάδες αγελάδων η ίδια ποσότητα τροφής, αλλά συνέχισαν να αρµέγονται 3 ή 2 φορές, όπως στην πρώτη περίοδο. Στη δεύτερη περίοδο οι αγελάδες που αρµέγοντο 3 φορές την ηµέρα έδωσαν 5.63 χλγ γάλα/ζώο περισσότερο από τις αγελάδες που αρµέγονταν 2 φορές, µε την ίδια χηµική σύσταση γάλακτος. Στην τρίτη περίοδο (57-70 µέρες) όλες οι αγελάδες αρµέγονταν 2 φορές την ηµέρα. Σ αυτή την περίοδο υπήρξε µια απότοµη πτώση της γαλακτοπαραγωγής στις αγελάδες που προηγούµενα αρµέγονταν 3x την ηµέρα. Και οι δύο οµάδες έδωσαν περίπου την ίδια µέση ηµερήσια παραγωγή γάλακτος (29.10 vs 29.54 χλγ). Οικονοµική σύγκριση µεταξύ αγελάδων που αρµέγονταν 2 ή 3 φορές την ηµέρα για τις δύο πρώτες περιόδους µαζί (εισόδηµα από το γάλα µείον έξοδα εργασίας+έξοδα διατροφής+έξοδα στο αρµεκτήρι) έδειξε ότι το οικονοµικό όφελος από τα ζώα που αρµέγονταν 3x την ηµέρα ήταν 76 σεντ περισσότερα ανά αγελάδα από τις αγελάδες που αρµέγονταν 2 φορές την ηµέρα. Το δεύτερο πείραµα έγινε σε µεγάλη ιδιωτική µονάδα και χρησιµοποιήθηκαν 126 αγελάδες στην µέση της γαλακτοπαραγωγής. Τα ζώα χωρίστηκαν τυχαία σε δύο οµάδες ανάλογα µε την παραγωγή γάλακτος, τη λιποπεριεκτικότητα και το στάδιο της γαλακτικής περιόδου. Μια οµάδα αρµεγόταν 3 φορές την ηµέρα ενώ η άλλη οµάδα συνέχισε να αρµέγεται 2 φορές την ηµέρα. Οι αγελάδες που αρµέγονταν 3 φορές την ηµέρα 3
έδωσαν 2.42 χλγ περισσότερο γάλα την ηµέρα από εκείνες που αρµέγονταν 2 φορές. Η περιεκτικότητα του γάλακτος σε λίπος ήταν χαµηλότερη και της λακτόζης ψηλότερη στις αγελάδες που αρµέγονταν 3 φορές την ηµέρα σε σύγκριση µε εκείνες που αρµέγονταν 2 φορές την ηµέρα. Το οικονοµικό όφελος από το άρµεγµα 3 φορές την ηµέρα ήταν 28 σεντ περισσότερο ανά ζώο την ηµέρα, σε σύγκριση µε αγελάδες που αρµέγοντο 2 φορές την ηµέρα. INTRODUCTION Increasing milking frequency of dairy cows increases daily milk yield. But the magnitude of the yield response to 3 times compared to 2 times daily milking is variable. A review study showed that increasing the milking frequency from 2x to 3x daily resulted in increased milk yield, which was on average 3.5 kg/cow/day (Erdman and Varner, 1995). Gisi et al. (1986) compared milk production of 28 California Holstein dairy herds that were changed from 2x to 3x daily milking. Milk yield increased 12% above the previous production on 2x daily milking. Allen et al. (1986) compared the milk yield of seven California Holstein dairy herds milked 3x daily to seven herds milked 2x daily located in the same area in California. Percentage increases in milk yield with 3 daily milkings were 19.40, 13.50, 11.70 and 13.40% for first, second, third and fourth or higher lactation, respectively. Complete lactation studies showed increases in milk yield of 15 and 6% (DePeters et al., 1985) and 19 and 25% (Amos et al., 1985) for older cows and first lactation cows, respectively, with 3x milking compared to 2x milking. Poole (1982) observed an increase of 19 and 13% in milk yield of cows and 1st lactation heifers during the first 20 weeks of lactation, whereas from calving to 150 days postpartum cows milked 3x produced 20% more milk than cows milked 2x daily (Pearson et al., 1979). Generally increasing frequency of udder emptying increased milk production. There are few reports concerning the persistency of effects after cows return from 3x to 2x milking daily. After 20 and 14 weeks of milking 2x daily carry-over effects were 9 to 11%, respectively (Pearson et al. 1979; Poole, 1982) which were not statistically significant. Although 3x milking compared to 2x milking daily increases milk yield, the dairy producer may be reluctant to apply 3 milkings, because of increased feed, labor and parlor supplies, unless he is certain of the magnitute of the yield response. The objectives of the present work were to measure the response of cows to three daily milkings compared to 2x daily, its effect on milk composition and on the persistency of milk yield after been switched from three to two milkings daily. MATERIALS AND METHODS Trial 1 Animals. Eighteen lactating Friesian cows, 12 multiparous and 6 primiparous, were randomly allocated to two groups of 9 cows (6 multiparous and 3 primiparous in each group), on the basis of milk yield, fat content of milk, live weight and days in lactation (Table 1). One group of cows continued to be milked two times daily (2x milking) while the other group was milked three times daily thereafter (3x milking). The trial lasted 70 days. The first period lasted 42 days (13 February to 26 March, 1997). Cows were milked 3x daily and consumed more feed than cows milked 2x daily. In the second period that lasted from 43 to 56 days (27 March to 9 April, 1997) cows continued to be milked as in period I, but daily feed offered was similar for both groups. From 57 to 70 days (10 April to 23 April, 1997) cows milked 3x daily were changed to 2x milking daily, while average daily feed offered per treatment was similar as in period II. Feeding and management. Till the commencement of the tial all cows were housed in the same pen, were milked twice daily, had similar management and were fed the same kind of roughages and concentrate mixture, but on the basis of requirements (NRC, 1989). With the commencement of the trial all cows were offered 2 kg of alfalfa hay and 5 kg of cereal hay per head daily and a concentrate mixture, containing 18% crude protein on as fed basis. The ingredients of the concentrate mixture was the following (kg/t finished feed). Barley grain 613, corn grain 100, soybean meal 236, wheat bran 25, dicalcium phosphate 2.5, limestone 18, salt 3.5 and vitamin and trace element mixture 2.0. The vitamin and trace element mixture 4
Table 1. Initial milk yield, fat content and days post-partum of dairy cows milked to 2 or 3 times daily 2x milking 3x milking SE Agricultural Research Institute No of cows 9 9 - Initial milk yield (kg/cow/day) 33.53 33.80 2.06 Initial fat content (%) 2.96 3.06 0.16 Days post-partum 85 82 13.82 Live weight (kg/cow) 546 534 25.52 Private Dairy Farm No of cows 63 63 - Initial milk yield (kg/cow/day) 24.77 24.33 2.12 Initial fat content (%) 3.03 3.11 0.14 Days post-partum 169 170 34.35 provided 8000 I.U. vitamin A, 600 I.U. vitamin D, 15 I.U. vitamin E, 25 mg Mn, 30 mg Fe, 1.5mg I, 1.5 mg Co, 45 mg Zn and 60 mg Mg per kg of finished feed. The average amount of concentrates offered daily was 15.38 or 15.16 kg for cows milked 3x or 2x daily, respectively. The daily allowance of the concentrate mixture was offered individually in 5 meals (08:00, 12:00, 16:00, 20:00 and 24:00 h) via a computerized feeding system. Any concentrate residues were offered in a 6th meal at 04:00 h. The daily allowance of metabolisable energy (ME) intake for each cow was based on live weight, parity and the energy secreted in milk (NRC, 1989). The average daily ME intake derived from roughage was subtracted from the recommended ME intake and the daily allowance of concentrates was calculated from published values of the ME content of feeds (Hadjipanayiotou et al., 1983; NRC, 1989). Feed offered was adjusted every two weeks for cows milked 2x daily. However, cows milked 3x daily increased their daily milk yield considerably from the first 3 days of the trial and this prompted the increase of their daily feed intake by 1.0 kg cereal hay and 0.5 kg of concentrates, by the 5th day from the commencement of the trial. Feed intake was then adjusted at 2-week intervals, increasing daily roughage intake to 8 kg (to keep similar roughage to concentrate ratios in the 2x or 3x milking cows) and concentrates according to energy requirements (NRC, 1989). In period II cows in both groups were offered 5 kg of cereal hay and 2 kg alfalfa hay. Concentrates were reduced by 2.28% in the 3x milking group and increased by 3.52% for the 2x milking group compared to the previous period, since daily intake of concentrates had to be similar in both groups i.e. 15 kg/cow. In the third period (57 to 70 days), feed offered per cow was kept constant as in Period II and all cows were milked 2x daily. All animals had free access to water. The time at which milking began and the milking intervals (h) are given in Table 2. Trial 2 Animals. One hundred and twenty six Friesian cows, at a private farm of 450 milking cows, were used. The individual milk yield of cows ranged from 14 to 40 kg, with 21% of the cows producing between 30 and 40 kg, 53% from 20 to 30 kg, 19% from 15 to 20 kg and 7 % less than 15 kg. Animals were randomly allocated to two groups of 63 cows each, on the basis of milk yield, fat content of milk and days postpartum (Table 1). One group of cows continued to be milked two times daily (2x milking) and the other group was milked three times daily (3x milking) after the commencement of the trial. The time milking becan and the milking intervals (h) are given in Table 2. The trial lasted 35 days. Feeding and management. From calving to the commencement of the trial all cows were milked twice daily. At the commencement of the trial, cows were placed in two adjacent pens and energy and protein requirements were calculated based on the previously recorded individual milk yield, fat content of milk and an assumed mean live weight of 600 kg, since live weights were not available (NRC, 1989). Feed ingredients and the concentrate mixture were those used by the dairy farmer (Table 3). Feed was offered using a mixing wagoon. Half the quantity of the prepared feed was given to cows milked 5
Table 2. Time at which milking began and milking intervals 2x milking 3x milking Time of Milking Time of Milking milking (h) interval (h) milking (h) interval (h) Agricultural Research Institute Morning milking 04.45 14 04.30 7.30 Afternoon milking 14.45 10 13.30 9.00 Night milking - - 21.00 7.30 Private Dairy Farm Morning milking 08.30 12 05.00 7.30 Afternoon milking 08.30 12 12.30 7.30 Night milking - - 21.30 9.00 3x daily, and the other half to those milked 2x daily. The mean daily consumption per cow was 160 MJME and 2540 g of crude protein during the 35 day experimental period. Feed intake was adjusted 2 weeks after the commencement of the trial. Animals had free access to water. The cows were milked in a computerized milking parlour providing information on the cow, the quantity of milk milked, the cluster take-off at the end of the milking and milk samples for chemical analysis (AFIMILK SYSTEM, Kibbutz AFI- KIM, Israel). Milk yield was recorded daily as a group, and individually on days 14 and 28 of the trial. The time at which milking began and milking intervals are given in Table 2. After the end of the 28-day experimental period, cows were kept for 7 more days in the same pens on the same feeding and management, but cows milked 2x daily were changed to 3x daily milking. Milk yield was recorded as a group for 3 consecutive days, on days the 33, 34 and 35 of the trial. Chemical analysis Milk samples were analysed for fat and protein in trial 1 and feed samples in both trials 1 and 2 for dry matter, crude protein and ash (MAFF, 1973). Milk samples in trial 2 were analysed for fat, protein, lactose and total solids (Milkoscan 4200, FOSS, Denmark). Statistical analysis The data in both trials were analyzed by one-way analysis of variance for each period separately and for periods I + II jointly in trial 1 (Steel and Torrie, 1960); differences among means were tested using Duncan s new multiple range test. RESULTS Health There were no cases of mastitis in trial 1. However, in trial 2, five cows in the group milked 3x daily and 4 from cows milked 2x Table 3. Dry matter and crude protein content of feeds and feed intake of cows in the private farm 6 Intake (kg/cow/day) Dry matter Crude protein (%) (%DM) As fed Dry matter Concentrates 88.0 17.50 11.0 9.68 Roughage Corn silage 29.0 8.50 1.50 0.43 Cereal silage (wheat + oats) 34.0 12.00 6.0 2.04 Citrus peels 15.0 7.00 3.70 0.55 Cereal hay (barley + oats) 87.5 10.00 1.00 0.87 Lucerne pellets 88.0 16.80 3.00 2.64 Total - - 26.20 16.21 The composition of the concentrate mixture was the following (kg/ton finished feed): Barley grain 237, corn grain 375, sunflower meal 150, soybean meal 92, wheat bran 114 and minerals plus vitamins and trace elements 32.
Table 4. Milk yield, milk composition, liveweight changes and feed intake of cows milked 2 or 3 times daily during period I (42 days) and period II (14 days) Period I Period II Trait 2x milking 3x milking SE 2x milking 3x milking SE Milk yield (kg/cow/day) 31.43b 38.28a 2.04 29.58 35.21 1.99 Fat (%) 3.58 3.26 0.13 3.70 3.68 0.16 Crude protein (%) 2.99 3.05 0.10 3.17 3.15 0.09 Initial live weight (kg) 546 534 25.52 562 553 24.19 Final live weight(kg) 562 553 24.19 557 543 23.62 Gain (kg/day) 0.39 0.46 0.11 0.35-0.77 0.28 Feed intake (kg/cow/day) Concentrate 14.49 15.35 0.63 15.0 14.96 0.59 Alfalfa hay 2.0 2.0-2.0 2.0 - Cereal hay 5.0 5.80-5.0 5.0 - Means in the same row followed by a different letter differ significantly based on Dunca s New Multiple Range test (P<0.05). daily got mastitis. Data on 3 cows (1milked 3x and 2 milked 2x daily) were discarded, because milk yield ceased or was reduced to very low levels. Hence, data reported refer to 62 cows milked 3x and 61 cows milked 2x daily. In trial 1, daily milk yield of cows milked 3x daily was significantly higher (P<0.05) than that of cows milked 2x daily in period I (Table 4). Fat content was 0.32% lower and protein 0.06% higher in cows milked 3x daily than those milked 2x daily (Table 3). Feed intake was higher in cows milked 3x daily (0.86 kg of concentrates and 0.8 kg of cereal hay, equivalent to 15.23 MJME per day, approximately); both groups of cows gained weight (Table 4). In period II feed intake was similar for both groups of cows, but cows milked 3x daily produced more milk (5.63 kg/cow/day) (Table 4). Fat and protein content of milk were similar, but cows milked 3x daily tended to loose more weight than those milked 2x daily (Table 4). When data of period I and period II were pooled (56 days), cows milked 3x daily produced significantly more milk (P<0.05), but of lower fat content (0.17%), consumed more feed daily and gained less weight than cows milked 2x daily (Table 5). When cows previously milked 3x daily were switched to 2x daily milking there was a sharp decline in milk yield (Fig. 1) and both groups produced similar milk yield (Table 6). Fat and protein per- Table 5. Milk yield, milk composition, liveweight changes and feed intake of cows milked 2 or 3 times daily during period I + II (56 days) Trait 2x milking 3x milking SE Milk yield (kg/cow/day) 31.0b 37.50a 2.02 Fat (%) 3.64 3.47 0.14 Crude protein (%) 3.07 3.10 0.09 Initial live weight (kg) 546 534 25.52 Final live weight (kg) 557 543 23.62 Gain (kg/day) 0.20 0.160 0.10 Feed intake (kg/cow/day) Concentrate 14.63 15.25 0.60 Alfalfa hay 2.0 2.0 - Cereal hay 5.0 5.6 - Roughage: Concentrate Ratio 32.4:67.6 33.2:66.8 - See footnote in Table 3. 7
Figure 1. Milk yield of cows milked 3 times (+...+...+) or 2 times (o---o---o) centages were also similar. Feed intake was slightly lower in cows switched to two milkings and lost significantly more weight than those milked continuously 2x daily (Table 6). Cows milked continuously 2x daily, reduced their milk yield during period I by 6.13% (6.31% for multipara and 5.76% for primipara), during period II by 5.75% (7.54% for multipara and 2.09% for primipara) and during period III by -0.18% (-0.41% for multipara and +0.27% for primipara). Cows switched from 2x to 3x daily milking increased milk yield during period I by 12.9% (11.74% for multipara and 15.26% for primipara) during period II reduced milk yield by 8.13% (8.54% for multipara and 7.33% for primipara) and during period III Figure 2. The effect of changing milking from two to three times daily on the daily milk yield of cows by 16.42% (17.42% for multipara and 14.43% for primipara). In trial 2, the daily milk yield of cows milked 3x daily was 2.42 kg or 11.68% higher (P<0.05) than that of cows milked 2x daily (Table 7). When the daily milk yield of the 20 higher producing cows in each group was considered, cows milked 3x produced 3.78 kg (13.38%) more milk (P<0.01) than cows milked 2x daily (Table 7). The remaining medium and low yielding cows milked 3x daily produced, 1.95 kg (11.38%) more milk (P<0.01) than cows milked 2x daily (Table 7). The daily milk yield of the two groups of cows is shown in Figure 2. The time when cows milked 2x daily were switched to 3x Table 6. Milk yield, milk composition, liveweight changes and feed intake of cows milked 2 or 3 times daily and changed to 2 times daily during period III (14 days) Trait 2x milking 3x to 2x milking SE Milk yield (kg/cow/day) 29.54 29.10 1.49 Fat (%) 3.31 3.39 0.13 Crude protein (%) 3.23 3.19 0.07 Initial live weight (kg) 557 543 23.62 Final live weight (kg) 568 538 24.45 Weight change (kg/day) +0.78a -0.30b 0.24 Feed intake (kg/cow/day) Concentrate 14.96 14.68 0.56 Alfalfa hay 2.0 2.0 - Cereal hay 5.0 5.0 - See footnote in Table 3. 8
Table 7. Milk yield (kg/day) and milk composition with two or three milkings daily in the private farm 2x milking 3x milking SD Milk Yield ALL COWS 61 62 1st +2nd recordings 20.72a 23.14b 7.15 High yielding cows 20 20 1st +2nd recordings 28.24a 32.02b 3.53 Low and medium yielding cows 41 42 1st +2nd recordings 17.13a 19.08b 4.45 Milk composition all cows 61 62 Fat (%) 3.27a 3.04b 0.50 Protein (%) 3.26 3.22 0.30 Lactose (%) 4.29a 4.53b 0.34 Total Solids (%) 11.47 11.44 0.80 Means in the same row followed by a different letter differ significantly based on Duncan s New Multiple Range test (Low case:p<0.05; Capital:P<0.01). Table 8. Income minus costs of labour, feed and other parlour utilities per cow milked 2x or 3x daily in trial 1 2x milking 3x milking Difference # 3x-2x Income Milk (l/cow) 30.10 36.41 Price (cent/l) 17.50 17.50 Income (cent/cow/day) 527 637 110 Expenses Labour (minutes/cow) 7.30 10.95 Labour cost (cent/cow) 45.41 68.11 22.70 Feed Concentrates (kg/cow) 14.63 15.25 Price (cent/kg) 7.8 7.8 Alfalfa (kg/cow) 2.0 2.0 Price (cent/kg) 11.0 11.0 Cereal hay (kg/cow) 5.0 5.6 Price (cent/kg) 7.5 7.5 TOTAL (cent/cow) 173.61 182.95 9.34 Parlour utilities (Water, washing towels, disinfectant, electricity) (cent/cow) 3.02 4.50 1.48 Total expenses (cent/cow/day) 222.04 255.56 33.52 Income-expenses (cent/cow/day) 304.96 381.44 76.48 # C =100 cent = 2 US$. daily is indicated by an arrow. The daily milk yield on day 28 was 23.13 and 20.50 kg (difference 2.63 kg daily) for cows milked 3x and 2x, respectively; seven days later when all cows were milked 2x daily, it was 22.51 and 22.01 kg (difference 0.5 kg daily). Cows milked 2x daily produced milk with significantly higher (P<0.01) fat, of similar protein and total solids, but of lower (P<0.01) lactose content than cows milked 3x daily (Table 8). 9
DISCUSSION It is well documented that daily milk yield increases with increasing milking frequency. In the present studies cows changed from 2 to 3 daily milkings in trial 1, produced 6.85 kg or 21.79%, in period I, 5.63 kg or 19.03% in period II and 6.50 kg or an average of 20.97% when periods I and II were pooled, more milk than those milked twice daily. In the second study, cows differences were smaller (2.42 kg or 11.68% more milk than cows milked 2x daily). However, the 20 highest producing cows milked 3x daily produced 3.78 kg or 13.38% more milk than those milked twice daily while lower producing cows milked 3x daily produced 1.95 kg or 11.38% more milk than cows milked 2x daily. The different response of cows in trial 1 to 3 daily milkings was mainly attributed to the higher initial milk yield (33 to 34 kg compared 24 to 25 kg and the earlier stage of lactation (82 vs 170 days). Milk increases due to increase with 3 milkings in trial 1 were higher than other reports (Poole, 1982; Gisi et al., 1986; Allen et al., 1986; Erdman and Varner, 1995). The latter agree more with the second study in the private farm. In addition to initial milk yield and stage of lactation, possible other factors contributing to the differences in response are the duration of the trial, the number of heifers and cows, and the milking interval. In trial 1, the milking interval was 10 and 14 h and although the rate of secretion of milk is linear up to 16 h, the yield level of the cows is one of the main factors which affect the decline in the rate of milk secretion with increasing interval (Elliot and Prumby, 1955; Elliot et al., 1960; O Brien et al., 1998). The average milk yield of the cows used in the present study was 8164±1586 (8784±1437 for cows and 6923±1113 for heifers cows). The response in milk yield to three daily milkings was higher in heifers (15.26%) compared to cows (11.74%) in trial 1. In other studies, responses were either similar (Erdman and Varner, 1995) or heifers had a greater response than cows (Amos et al., 1985; Allen et al., 1986) or had lower responses (Poole, 1982; DePeters et al., 1985). When cows were switched from 3 to 2 milkings (period III of trial 1), there was a sharp decline in the milk yield; the average milk yield of the two groups was similar in this period (29.10 vs 29.54 kg). The decline was lower in heifers (14.43%) than in cows (17.42%). Similar findings were reported by Pearson et al., 1979 and Poole (1982), but those studies showed also a positive carry over effect in daily milk yield, which was not observed in the present study. The fat content of milk produced from cows milked 3x daily was lower than that of cows milked 2x daily. Protein content was similar in both trials, irrespective of milking frequency. Total solids were also similar in trial 2, but lactose content was significantly higher (P<0.01) in milk produced from cows milked 3x daily in trial 2. Average fat content of milk was lower from cows milked 3x instead of 2x daily (Pearson et al., 1979; Erdman and Varner, 1995) and protein declined as milking frequency increased (Erdman and Varner, 1995). Others reported no effect of milking frequency on the fat content of milk (Poole, 1982; Gisi et al., 1986). Concerning the higher lactose content of milk in cows milked 3x daily in trial 2, it is possible that since lactose is derived from glucose, a higher uptake of glucose by the mammary gland was necessary to promote higher milk secretion (Linzell, 1968) resulting also in the higher lactose content. In trial 1 during period I cows milked 3x daily consumed more feed and, although milk yield was higher, they also gained more weight than cows milked 2x daily. During period II when feed intake of cows milked 3x daily was reduced, milk yield continued to be higher, but they lost weight. In other studies either dry matter intake was increased with frequent milking but it was insufficient to support enhanced milk production and the cows lost weight (Bar-Peled et al., 1995), or 3x milked cows consumed more concentrates produced more milk, but gained less weight than cows milked 2x daily (Poole, 1982). In some studies higher dry matter intake was associated with higher milk yield from higher milking frequencies, but in other studies the increase was too small to be measurable or non existent (Amos et al., 1985; DePeters et al., 1985). Improved nutrition, including better guality of forage and increased feeding frequency may be necessary to maintain the higher response in milk from 3x milking and minimize body weight loss during lactation. 10
Concerning udder health no cases of mastitis were observed in trial 1, and the frequency of incidence of mastitis was similar in both groups in trial 2. In other studies udder health was not affected by the frequency of daily milking daily (Pearson et al., 1979; Poole, 1982; Gisi et al., 1986). An additional advantage for cows milked 3x daily is the more frequent handling and observation of the dairy herd (ICBA, 1995). However, the dairy producer should only increase milking frequency, when the income above costs to produce this additional milk is positive. The major factor affecting profitability of 3x milking are increased labour costs (Culotta and Schmidt, 1988). In trial 1, additional labour compised 67.70% of the additional expenses of 3x milking, feed costs 27.90% and other expenses 4.40% (Table 10). In trial 2, feed expenses were similar in 3x or 2x milked cows, milking parlour expenses were about 0.50 higher in cows milked 3x and cows milked 3x daily required only 2 h more labour, because of some automation of the system and the organisation of labour. Other studies (Pearson et al., 1979) showed that milking time for 3x milked cows was 150% of that of 2x milked cows. The increase in milk yield with three milkings daily, may justify its use in large, highly automated milking facilities when labour can be managed successfully or with robotic attachment and take-off of milking units when labour is reduced without added labour cost (Pearson et al., 1979; Culotta and Schmidt, 1988). The use of three milkings is carried out regularly in shifts in all Kibbutzes in Israel, but material compensation is not linked to the effort made (ICBA, 1995). Other factors affecting the profitability of three milkings daily are the increased feed costs the level of increase of milk yield, the genetic potential of cows and the selling price of milk. In the present studies, profitability from milking cows 3x daily was 0.76/cow/day in trial 1 (Table 10) and 0.28/cow/day in trial 2 assuming that labour cost in the private farm was similar to that in trial 1. It may be concluded that three milkings increased daily milk yield/cow, fat content of milk was slightly reduced and profitability was higher than two daily milkings. ACKNOWLEDGEMENTS The author is grateful to G. Kyprianou, Ch. Vanezi, A. Photiou, Mary Karavia, Maria Theodoridou for skilled technical assistance and G. Psathas of the Cyprus Milk Industry Organization for the chemical analysis of milk from the private farm. I wish also to thank Lytras Bros, Ltd. for their kind cooperation in carrying out one of the studies in their farm at Athienou. REFERENCES Allen, D.B., E. J. DePeters, and R.C. Laben. 1986. Three times a day milking: Effects on milk production, reproductive efficiency, and udder health. Journal of Dairy Science 69:1441-1446. Amos, H.E., T. Kiset, and M. Lowenstein. 1985. Influence of milking frequency on productive and reproductive efficiencies of dairy cows. Journal of Dairy Science 68:732-739. Bar-Peled, U., E. Maltz, I. Bruckental, Y. Folman, Y. Kali, H. Gacitua, A.R. Leghrer, C.H. Night, B. Robinson, H. Voet, and H. Tagari. 1995. Relationship between frequent milking or suckling in early lactation and milk production of high producing dairy cows. Journal of Dairy Science 78:2726-2736. Culotta, C.P., and G.H. Schmidt. 1988. An economic evaluation of three times daily milking of dairy cows. Journal of Dairy Science 71:1960-1966. DePeters, E.J., N.E. Smith, and J. Acedo-Rico, 1985. Three or two times daily milking of older cows and first lactation cows for entire lactations. Journal of Dairy Science 68:123-132. Elliot, G.M., and J. Brumby. 1955. Rate of milk secretion with increasing interval between milkings. Nature 176:350. Elliot, G.M., F.H. Dodd, and P.J. Brumby. 1960. Variations in the rate of milk secretion in milking intervals of 2-24 hours. Journal of Dairy Research 27:293-308. Erdman, R.A., and M. Varner. 1995. Fixed yield responses to increased milking frequency. Journal of Dairy Science 78:1199-1203. 11
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