Influence of calf presence loose in a pen alongside the milking parlor on yield and fat content of milk from Brahman x Holstein cows

An experiment was carried out to evaluate the influence of three cow management strategies at milking on milk yield and composition and on live weight (LW) gain of the calves. Twenty four Brahman x Holstein cows were used for the following treatments:  (W) without calf stimulation at milking; (T) calf tied beside its mother during milking and (L) calf loose in a pen along the milking parlor. The cows were machine milked twice daily, at 06:30 and 15:30 h and suckling was allowed for 30 minutes after morning milking until weaning at 119 days.

On treatments W, T and L, average saleable milk yields until weaning were 5.6; 8.0 and 7.7 kg/day (P = 0.013) in the morning and 1.9; 4.2 and 3.2 kg/day (P = 0.001) in the afternoon, consumed milk was 2.8. 1.8 and 2.3 kg/day (P = 0.204) and calf  LW gains were 0.62, 0.40 and 0.41 kg/day (P=0.005). It was shown that calf presence during milking elevates total and saleable milk yield and reduces calf live weight gain. Results obtained tying the calves close to their dams or maintaining them loose in a pen alongside the milking parlor are similar, except a lower milk fat and yield of some L cows at the afternoon milking.

Untied calves allows group handling and appreciably facilitates management during milking in dual purpose herds.

Keywords: Cattle, milk production, milking management, suckling

Crossbred Bos indicus x Bos taurus cows used in dual purpose systems in the tropical American lowlands require the stimulation by the calf during milking, otherwise the proportion of saleable milk and its fat content is severely reduced (Sandoval-Castro et al 1995). The traditional stimulation practice is to allow a short period of suckling before milking until milk ejection occurs, but adequate installations are required for machine milking and the separation of the calf after suckling is difficult with heavy animals and can result in lesions. To overcome these inconveniences several options have been evaluated in a series of trials carried out at this institute, with the final objective to minimize calf handling without losing the milk let down stimulation (see Combellas and Tesorero 2003).

The main advance so far has been to tie the calf close to its dam and similar amounts of saleable milk yield were obtained between it and the traditional practice (Combellas et al 2003), facilitating management but still requiring the individual calf handling in the parlor. A further approach would be to avoid tying, locating the calf within its dam's vision range. The objective of this paper was to evaluate this strategy, holding the calves loose in a narrow pen alongside the milking parlor, so that their dams had a short contact with them on their way to the milking places and had visual contact during milking.

Location

The experiment was carried out at the Faculty of Agronomy, Maracay, between May 2005 and January 2006. Average annual rainfall in the nearby CENIAP station (INIA, Unidad de Agroclimatología) was 1048 mm and average maximum and minimum temperatures were 32.0 and 17.3 °C.

Cow management, experimental design and treatments

Twenty four 5/8 to 3/4 Holstein x Brahman cows of two or more parities were used from calving to weaning at 119 days. The year before all cows were milked without their calves being present at milking.  The animals grazed on paddocks of Cynodon nlemfuensis, Brachiaria mutica and Digitaria swasilandensis all day, except at machine milking that started at 06:30 and 15:30 h, with average standing forage offer; CP content and NDF content of 4.90 tonnes/ha; 7.1 % and 69.8 % (both in DM), and were supplemented with 2.5 kg/day of a commercial concentrate of 18 % CP at milking. At the end of the morning milking, all cows were taken to the calves' shed and allowed to feed their respective calves for approximately 30 minutes, after which they were returned to the field for grazing. After the afternoon milking all cows were returned to the field for grazing, without feeding their calves.

A completely randomized design was used to compare the following strategies of milking:

W - Without the presence of the calf at milking.
T - With presence of the calf tied near the head of the cow throughout milking.
L - With presence of the calf loose in a 1.2 m wide pen alongside the milking parlor throughout milking.

Measurements

Saleable milk was measured daily at each milking and a weekly sample was taken for fat analysis from a bucket where all milk from the machine milking bottle was transferred and thoroughly mixed. Milk consumed by calves after milking was estimated weekly until weaning, weighing them before and after suckling with a 50 g precision electronic balance (Ohaus, Model CW-11), and a milk sample was taken just after suckling started. Fat content of saleable and consumed milk samples was determined by the Babcock method (AOAC 1984). The cows were weighed at calving and every week until weaning. The lowest LW of cows was reached two weeks after calving on average and LW gain was estimated from the third week until weaning. The calves were weighed at birth and every week afterwards until weaning at 119 days.

Calf management

The calves were stalled in partially roofed 2 x 6 m2 individual pens with a concrete floor, except during the first three days after calving in which they were kept with their dams. Chopped forage was offered ad libitum from paddocks similar to those used for cows and a commercial concentrate (Purina, Criavaquina 18 % CP) was offered up to 1 kg/day in separate feeding troughs. The calves on T and L were taken to the milking parlor, located at 30 m from their pens, L calves of the cows to be milked were taken to the pen alongside the parlor and their dams were brought afterwards, allowing a quick contact between them on their way to the milking places, located at 0.80 m from the internal fence of the calves' pen. T calves were tied near their dam's head during milking. Both groups were returned to their individual pens for suckling.

Statistical analyses

An analysis of variance was carried out to evaluate the influence of treatments on milk yield and composition, and on cows' and calves' LW gain. LW gain was estimated as the slope of the linear regression of weight on time. Treatment means were compared by the Duncan's Multiple Range Test.

Total milk yield was higher in T and L with the calf present during milking than in W. LW change in the cows was nearly 0.2 kg/day higher in the latter treatment, indicating a higher partitioning of nutrients to body reserves in these animals (Table 1). Morning and afternoon saleable milk were higher in T and L and no statistical differences were observed in milk consumed between treatments, but tended to be higher in W and were significant (P=0.003) when expressed as percentage of total milk. Milk fat content was also influenced by calf stimulation in the parlor, increasing in all fractions in relation to W. There is an increasing gradient in fat milk content with milking and low values of fat milk are related to a low proportion of milk extracted. A comparison between T and W was carried out before (Combellas et al 2003) and these results confirm that tying the calf close to its dam stimulates let down during milking and affects milk fat and yield fractions.

Differences were not observed between L and T in consumed milk, but as a percentage of total milk yield and standard deviation (17.0 ± 6.0 and 12.8 ± 2.2 %) tended to be higher in L, indicating  stimulation by the "loose" calves on milk let down was low in some cows. It is known that olfactory and vision are equally effective in permitting calf identification by its dam, inhibiting luteinizing hormone secretion (Griffith and Williams 1996); and oxytocin (OT) release is also stimulated as shown by the observed milk yield differences between L and W in the present trial, but OT secretion intensity is variable depending on the stimulus applied (Bar-Peled et al 1995), affecting milk release from incompletely filled alveolus that require high myoepithelial cell contraction to press milk out (Bruckmaier 2001).

OT blood levels were not evaluated in this trial and the only known evidence with crossbred dual purpose animals (Negrão and Marnet 2002) has shown that machine milking is enough to increase blood OT levels during milking in ¼ Gir x ¾ Holstein cows to values similar to those of cows stimulated with their dams at milking. But suckling was not used at any time in the first treatment and Bar-Peled et al (1995) observed, in an experiment where suckling and milking were alternated every 4 h, that OT levels were much higher when suckling was used. In the present trial differences were found between T and L during afternoon milking, where lower milk yield was obtained because of the short interval of about 7 h from the morning calf suckling. L cows had lower milk fat and milk yield tended to be lower than in T cows and it could be related to differences in OT blood levels and their effects on myoepithelial cell contraction required to press milk out of incomplete filled alveolus at this milking.





Calves' live weight (LW) gain was higher in W than in T and L (Table 1), associated with a difference of 0.5 to 1.0 kg/day in milk consumed. Solid feed consumption was not measured in this trial, but former trials have shown an increment in these feeds as milk intake decreases, insufficient to compensate the fall in nutrient ingestion (Tesorero et al 2001). LW gains were similar in T and L, related to the small differences in consumed milk observed between these treatments.

• Handling calves in a group alongside the milking parlor appreciably facilitates management and these results have shown that it is enough to stimulate milk release, but the high variation in the consumed/total milk ratio shows that individual differences in cow stimulation still occur.

• This regime is an improvement over other management practises evaluated before, such as tying the calf close to its dam, and calves can be handled in a group, but it still requires a calf handling not easy to carry out in large herds.

The authors express their gratitude to FONACIT for the financial support (Project No. S1-2002000409)

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Tesorero M, Combellas J, Uzcátegui, W and Gabaldón L2001 Influence of suckling before milking on yield and composition of milk from dual purpose cows with restricted suckling; Livestock Research for Rural Development 13(1) http://www.cipav.org.co/lrrd/lrrd13/ 1/teso131.htm