Abstract Thirty-two multiparous Holando argentinocows in mid lactation were randomly assigned to twotreatments: control or HFF (hydrogenated fish fat) at Rafaela, 31° 11’ South, during summer 1997/1998, toevaluate the effect of using HFF as a supplement undergrazing conditions. Animals in both treatments grazed analfalfa pasture, and were confined from 1000 hours to1700 hours daily in a shaded pen where water was pro-vided ad libitum. During each milking, animals in thecontrol group received 3.73 kg dry matter per cow eachday (DM cow–1 day–1) concentrate (15% crude protein;8.69 MJ energy for location/kg DM). Cows in the HFFgroup received 3.25 kg DM cow–1 day–1 concentrate,plus 0.200 kg DM cow–1 day–1 HFF. Both diets presentedsimilar energy, protein and neutral detergent fibre con-tents. The trial was performed during a strong “El Niño”event, which resulted in a total rainfall of 396.3 mm(80% higher than normal). The mean temperature was23.7 (SD 3.2)°C and the mean temperature humidity index was 72.9 (SD 4.96).

Production data were analysed using a completelyrandomised design with analysis of covariance. Supple-mentation with HFF produced an increase in daily milkproduction (26.4 (SD 2.46) l/cow compared to 23.9 (SD2.68) l/cow for the controls; P<0.05). Milk fat produc-

tion was higher for HFF (P<0.05): 941 (SD 96) g cow–1

day–1 as compared to controls, which yielded 846 (SD 95) g cow–1 day–1. Milk protein yields also differedsignificantly (P<0.05), the respective values for HFF and controls being 795 (SD 72) g cow–1 day–1 and 715(SD 83) g cow–1 day–1. It was concluded that hydroge-nated fish fat could be a good ingredient to sustain highyields and elevated maintenance requirements in a graz-ing system during hot conditions.

Keywords Milk yield · Hydrogenated fish fat · Environmental stress · El Niño event · Dairy cows

Introduction

Heat stress results from an animal’s inability to dissipatesufficient heat to maintain homeothermy. Two sources ofheat impact the cow: the environment and the internal pro-duction from nutrient metabolism. As milk yield and feedintake increase, more heat is produced from nutrient metabolism, thus adding to the environmental heat load(Ingram and Mount 1975; Linn 1997). Therefore, obviousadvantages of reducing metabolic heat production in thecow during hot weather are improved metabolic efficiencyand less heat to be dissipated (West 1999). Identifying dietary modifications to reduce heat production and im-prove efficiency of energy use are important to achievethis reduction in metabolic heat. Greater dietary nutrientdensity is required if milk yield is to be maintained duringperiods of heat stress. The addition of fat to the diet of lactating dairy cows has become a common practice, andthe greater energy density and the potential to reduce theheat increment of high-fat diets may be particularly bene-ficial during hot weather (West 1999). In this context, auseful technology is the addition of by-pass lipids to thediet. There are different by-pass lipid supplements avail-able in the feed market. These supplements are producedfrom either vegetable or animal sources, via industrialprocesses to deactivate their ruminal degradation, as wellas their utilisation at the duodenal level (Eastridge 1996).

M.R. Gallardo · J.A. MaizteguiSchool of Veterinary Sciences National University of Littoral,Santa Fe, Argentina

S.E. Valtorta (✉ ) · P.E. Leva · H.C. CastroSchool of Agricultural Sciences, National University of Littoral,R.P. Kreder 2805 (3080) Esperanza, Santa Fe, Argentina

S.E. ValtortaNational Council for Scientific and Technological Research, Esperanza, Santa Fe, Argentina

M.R. Gallardo · H.C. CastroSchool of Agricultural Sciences National University of Littoraland Department of Animal Production, Rafaela Experimental Station, National Institute of Agricultural Technology (INTA), EEA Rafaela – INTA, CC 22, Ruta 34, km 227 2300 Rafaela, Santa Fe Province, Argentina

Int J Biometeorol (2001) 45:111–114 © ISB 2001

O R I G I N A L A RT I C L E

M.R. Gallardo · S.E. Valtorta · P.E. LevaH.C. Castro · J.A. Maiztegui

Hydrogenated fish fat for grazing dairy cows in summer

Received: 15 March 2000 / Revised: 12 March 2001 / Accepted: 21 March 2001

Different sources of fat have been evaluated in Argen-tina under grazing conditions (Gagliostro 1997) and inother areas of the world (Bines et al. 1978; Grummer1992). The results have shown an increase in milk yieldand, sometimes, a trend to an increase in butterfat. Hydrogenated fish fats are among the lipid supplements,but have not been extensively used for dairy cows. Norhave there been any significant effects on the digestionof dietary carbohydrates, regardless of their presentation:hydrogenated, unsaturated or encapsulated in casein(Sutton et al. 1975; Doreau et al. 1989). However, inChile, one of the main fish-meal producing countries,hydrogenated fish fats have been used to supplementdairy cow diets. The analysis of the effects of this ingre-dient on diet digestibility and milk production and com-position has shown good results (Avila et al. 1992;Franulic et al. 1992; Carrasco et al. 1992).

In Argentina, many dairy farms have gone through aprocess of intensification, leading to higher levels of pro-duction with yields sometimes higher than 8000 l/lacta-tion (peaks above 35 l cow–1 day–1) and heat stress effects have become much more evident. The responsesof milk production and composition to artiflcial shadingand energy concentrate supplementation have been re-ported (Valtorta et al. 1996; Gallardo 1998; Valtorta andGallardo 1998). The inclusion of lipid supplements couldbe an important tool to improve nutritional managementduring hot weather. Therefore, the present work was un-dertaken to evaluate the effect of using hydrogenatedfish fat as a supplement for highly producing dairy cowsunder summer grazing conditions, in the central milksupply area of Santa Fe, Argentina.

Material and methods

Experimental design and cows

The trial was performed at Rafaela Experimental Station, locatedat 31° 11’ South from 23 December 1997 until 23 February 1998.Thirty-two multiparous Holando argentino cows in mid lactation –132 (SD 19) days in milk – were randomly assigned to one of twotreatments: control or hydrogenated fish fat (HFF). The averagemilk production for the previous lactation was 7,200 l/cow. Cowswere grazed on midbloom alfalfa pasture, supplemented by con-centrates during milkings. Every day, from 1000 hours to 1700hours, all animals were sent to a confinement pen where shade andwater were provided.

Pasture and total diet

A rotational grazing system was used, the two groups of cows being rotated to a new paddock on a daily basis. Alfalfa yieldsranged from 2,300 to 2,800 kg dry matter (DM) ha–1. The size ofthe paddock strips were adjusted on the basis of the desired pas-ture level in the total diet. Once each week, both strips were di-vided so that each animal grazed an individual plot so that pastureconsumption could be estimated by the difference method (Meijs et al. 1981). The procedure sequence was as follows: day 1, strip division and estimation of herbage mass by cutting 15–0.25-m2

samples to the 5 cm level with a mower; day 2, individual plotgrazing; day 3, similar to day 1, to estimate leftover herbagemass.

During each milking, cows in the control group received 3.73 kg DM cow–1 day–1 energy concentrate based on corn grainand soybean (15% crude protein; 8.69 MJ energy for lactation/kgDM). Cows in the HFF group, on the other hand, were fed 3.25 kgDM cow–1 day–1 energy concentrate, plus 0.200 kg DM/cow day–1

Chilean hydrogenated fish fat (Zamrog). Both diets were formu-lated in a way such that they had similar levels of energy, proteinand neutral detergent fibre. The total dietary ingredients and thechemical composition are shown in Table 1.

Data collection and analysis

Individual milk yield was recorded every day. Milk samples werecollected every week from each of two consecutive recorded mil-kings (p.m. and a.m.) to determine fat and protein with an infraredanalyser (Milkoscan; Foss Electric, Hillerød, Denmark).

Meteorological data, including mean, maximum and minimumtemperatures, relative humidity and rainfall, were obtained fromthe Agrometeorological Station located at Rafaela ExperimentalStation, about 500 m away from the dairy farm. The daily tem-peratue/humidity index (THI) was calculated, according to Thom(1958).

Pasture consumption data were analysed in a split/plot design,and production data analysed in a completely randomised continu-ous design with analysis of covariance, in accordance with thegeneral linear models procedure of SAS (1988). The covariateswere milk production and milk fat and protein contents 15 daysprior to the beginning of the trial.

Results and discussion

The average estimated daily alfalfa grazing presented nosignificant response to treatment. Consumption estimateswere 11.44 (SD 2.3) kg DM cow–1 day–1 for animals inthe control group and 11.96 (SD 2.04)kg DM cow–1

day–1 for cows receiving HFF.The mean temperature during the trial was 23.7

(SD 3.2)°C, the mean maximum being 29.7 (SD 3.9)°Cand mean minimum 17.3 (SD 2.3)°C. The average THIwas 72.9 (SD 4.96), the maximum and minimum valuesbeing 77.3 (SD 5.31) and 63.14 (SD 3.27) respectively.The total rainfall was 396.3 mm, which is 80% higherthan the normal for that period. The monthly rainfall was

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Table 1 Ingredients and chemical composition, on a dry-matterbasis, of total diets offered to animals in the control (C) and hydrogenated fish fat (HFF) groups. NEL (net energy for lactation)

Ingredient Content (kg dry matter cow–1 day–1)

C HFF

Alfalfa grazing 11.50 11.50Corn grain 3.66 3.23Sorghum grain 1.31 1.13Soybean grain 1.33 1.16Wheat bran 1.16 0.98Hydrogenated fish fat – 0.20

Chemical compositionProtein (%) 20.9 20.9Fat (%) 3.17 3.78Neutral detergent fiber (%) 32.33 32.35NEL(MJ/kg) 6.59 6.68

113.3%, 103.3% and 30.7% higher than normal duringDecember, January and February respectively. The trialwas carried out during a very strong “El Niño” event(Wolter 1998). Table 2 shows the meteorological datacorresponding to December 1997 and January and February 1998, as well as the normal climatological data corresponding to each element (SMN 1986,1992).

The relative humidity was higher than normal becauseof the greater rainfall. As a consequence, THI was slightly higher than expected for the hot period, evenwhen air temperatures were a little lower than the clima-tological means. Minimum summertime THI values havebeen found to be more closely related with the dry matterintake of Jersey cows (Holter et al. 1996) and with milkproduction of Holando argentino cows (Valtorta et al.1988). According to Holter et al. (1996) dry matter in-take began to reduce when the minimum THI reached 56to 57 in the less-heat-sensitive Jerseys.

These meteorological conditions, together with muddy confinement pen conditions resulting from theunusually high precipitation levels, could negatively affect dairy production, especially in highly producingHolando argentino cows (Valtorta et al. 1996). Theseconditions, however, affected both groups equally.

Adding hydrogenated fish fat to the diet resulted in asignificant (P<0.05) increase in milk yield (Table 3). Ithas been reported that fats can be incorporated into thediet of cows in early post-partum in order to minimizedifferences between energy intake and energy output(Staples et al. 1992), and that absorption of total fatty ac-ids by ruminants is linear up to 1,200 g/day (Storry1988), which is about 6% of the dry matter intake. In thepresent trial the fat concentration of the diet was 4%.When animals are in mid lactation, the response to die-tary supplements decreases (Kellaway and Porta 1993),and the milk yield and dry matter intake of cows in mid-

lactation are reduced by hot weather conditions (Maustet al. 1992). The significant increase in milk yield ob-served in the present experiment could be due to the factthat increased intake of dry matter with added fat leadsto a lower heat increment during periods of heat stressand/or reduction in propionate inhibition when fat is substituted for grain (Allen 2000).

Although there are no references to the addition ofhydrogenated fish fat to the diet of dairy cows under heatstress in grazing systems, the present results could be ex-plained according to Skaar et al. (1989), who found thatcows fed fat-supplemented diets had improved lactationperformance during warm weather but not during coolweather. Despite the weather conditions, the levels ofproduction for both groups are considered to be high forour grazing production system.

Other supplements also have been reported to showbenefits. For example, Knap and Grummer (1991) re-ported that diets containing 5% added fat (60% prilledfatty acids, 40% tallow) fed to cows held in thermoneu-tral (20.5°C, 38% relative humidity) or hot environmen-tal conditions (31.8°C, 56% relative humidity) resultedin a non-significant increase in milk yield of 1.1 kg and0.3 kg in the cool and hot environments. Fat-correctedmilk increased by 2.7 kg/day and 1.8 kg/day. No interac-tions between diet and environment were detected. InArizona, Huber (1993) reported that adding 2.8% fat tothe diet during heat stress periods resulted in a small in-crease in milk production (average 0.76 kg/day).

In agreement with these results, Gonzalez Munizaga(1992) found no effect on milk protein contents whenhydrogenated fish fat was added to the diet. On the otherhand, Shaver (1990) observed a decrease in milk protein.

The utilization of other fat sources led to no detect-able changes in milk fat when palm-oil fatty acid calci-um salt supplements were given to dairy cows in Argentina under non-stressful conditions (Gagliostro1997), in accordance with the present results. Studies in other regions of the world also have shown similarresponses, in some cases with a positive effect on milkfat (Bines et al 1978; Gagliostro and Chilliard 1992;Grummer 1992).

Milk fat and protein yields were significantly in-creased by adding hydrogenated fish fat to the diet (Table 3). Similar results were found by Gonzalez Munizaga (1992).

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Table 2 Mean, maximum and minimum temperature, mean relative humidity, mean temperature humidity index (THI) and monthlyrainfall for December 1997, January and February 1998. The corresponding normal climatological data are also included

Parameter December January February

1997 Normal 1998 Normal 1998 Normal

Mean temperature (°C) 23.6 23.4 24.3 24.7 23.5 23.5Max. temperature (°C) 29.3 30.1 30.9 31.4 30 29.9Min. temperature (°C) 15.7 16.7 17.6 18.1 17.0 17.4Relative humidity (%) 74 67 78 69 80 72Mean THI 72.1 71.2 73.6 73.3 72.5 71.6Total rainfall (mm) 256 120 250 123 136 104

Table 3 Milk, fat and protein yields for cows in control (C) andhydrogenated fish fat (HFF) groups

Yields C HFF

Milk (kg cow–1 day–1) 23.9 (SD 2.3) 26.4 (SD 2.4)*Fat (g cow–1 day–1) 846 (SD 96) 941 (SD 95)*Protein (g cow–1 day–1) 715 (SD 83) 795 (SD 72)*

*Significant difference (P<0.05) within the row

It was concluded that hydrogenated fish fat could be a good ingredient to sustain high production yields andelevated maintenance requirements in a grazing systemduring hot weather.

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