Introduction duction in dairy herds in the UK and the Republic of

Livestock Production Science 64 2000 107–119 www.elsevier.com locate livprodsci The performance of Holstein Friesian dairy cows of high and medium genetic merit for milk production on grass-based feeding systems a,b b , b b a F. Buckley , P. Dillon , S. Crosse , F. Flynn , M. Rath a Department of Animal Science , Faculty of Agriculture, University College Dublin, Belfield, Dublin 4, Ireland b Dairy Husbandry Department , Teagasc, Moorepark Production Research Centre, Fermoy, Co. Cork, Ireland Received 24 July 1998; received in revised form 6 October 1999; accepted 29 October 1999 Abstract The effect of cow genetic merit on the performance of spring calving Holstein Friesian dairy cows in first, second and third lactation was investigated. The study contained 96 first lactation animals in 1995, 96 second lactation animals in 1996, and 72 third lactation animals in 1997. Half of the animals were of high genetic merit HG and half of medium genetic merit MG for milk production. Genetic effects for the traits of interest were estimated as the contrast between the two genetic groups. The HG cows produced significantly higher yields of milk, fat, protein and lactose when compared to the MG cows. During the grazing season the HG cows had significantly P , 0.001 higher grass DM intake GDMI. In very early lactation when cows were indoors, offered grass silage ad libitum plus 7.9 kg of concentrate DM daily, there was no difference in DM intake. During the non-lactating period the HG cows had significantly P , 0.01 higher silage DM intake SDMI. Cow genetic merit had no significant effect on live weight with the exception of pre-calving weight at the beginning of second lactation when the HG cows had significantly P , 0.05 higher live weight. At all stages of lactation the MG cows had significantly P , 0.001 higher condition score. In early lactation the HG cows had greater not significant live weight loss and significantly P , 0.05 greater condition score loss indicating greater negative energy balance. In the dry period the HG cows had significantly P , 0.01 greater live weight gain. The results of this study suggest that present day HG cows will produce high milk yields on a grass-based feeding system where an adequate quantity of high quality grass is available.  2000 Elsevier Science B.V. All rights reserved. Keywords : Dairy cows; Genetic merit; Grass; Milk production

1. Introduction duction in dairy herds in the UK and the Republic of

Ireland up to 1985 was relatively slow, particularly The rate of genetic improvement for milk pro- in contrast to that achieved in North America where genetic merit for milk production has increased by over 150 kg per year in the Holstein population Corresponding author. Tel.: 1353-25-42250; fax: 1353-25- Funk, 1993. However since then changes in EU 42340. E-mail address : fbuckleymoorepark.teagasc.ie P. Dillon legislation has allowed greater access to world 0301-6226 00 – see front matter  2000 Elsevier Science B.V. All rights reserved. P I I : S 0 3 0 1 - 6 2 2 6 9 9 0 0 1 6 7 - 0 108 F . Buckley et al. Livestock Production Science 64 2000 107 –119 genetics, and, in the past 10 years, has resulted in 2. Materials and methods rapid genetic improvement in UK and Irish dairy herds. This resulted in a rate of genetic improvement 2.1. Genetic groups of 2.2 per year between 1990 and 1994 Lindberg et al., 1998. Two groups, containing 48 cows each, initiated the A number of studies have investigated the per- study in 1995. The high genetic merit group HG formance of high genetic merit cows on feeding were imported from Holland and France as in-calf systems based on ensiled forages and relatively large heifers in 1994. The medium genetic merit group amounts of concentrates Veerkamp et al., 1994; MG were assembled from the Moorepark herd. Gordon et al., 1995. However, little information is Mean predicted differences PD and standard devia- available on the performance of present day high tion S.D. within each group for milk yield, fat genetic merit cows on seasonal calving, grass-based yield, protein yield, fat concentration and protein systems like those commonly in use in Ireland concentration were; 1 475 kg 76, 1 16.7 kg 2.4, Dillon et al., 1995. There are, for instance, con- 1 15.6 kg 1.3, 2 0.16 g kg 0.70 and 2 0.02 cerns that the negative energy balance found on other g kg 0. 25 for HG and 1 140 kg 68, 1 9.7 kg feeding systems is exacerbated on grass-based sys- 3.5, 1 7.0 kg 2.5, 1 0.84 g kg 0.68 and tems as these systems depend to a large extent on the 1 0.48 g kg 0.34 for MG. The PDs for each cow conversion of grazed grass to milk with little extra were calculated as 0.50 3 sire PDs, plus 0.25 3 concentrates fed. maternal grand sire PDs. The PDs of the sires and The term used for animals performing well in one the maternal grand-sires came from the August 1997 system of production, and not necessarily being able international proofs of the Animal Centre in Uppsala, to hold the same advantage in another feeding Sweden using the technique known as MACE Mul- system, is genotype 3 environment G 3 E inter- tiple-trait Across Country Evaluation Schaeffer and action Peterson, 1988; Graham et al., 1991. If there Zhang, 1993, with no Moorepark records included. is evidence of G 3 E, then there is no indication of The sires of cows in both the HG and MG had at how progeny of a particular sire will perform in a least 75 daughters in at least 70 Irish herds contribut- feeding system very different to that in which it is ing to their MACE proofs with a reliability of greater tested. This study contains three environments and than 90. two genetic groups high and medium genetic merit, Animals of similar genetic merit and lactation HG and MG, respectively. The grouping of cows in number replaced animals culled after the 1995 genetic groups is based on sires breeding values. The grazing season. Replacements were not available in sires of the cows had Interbull-breeding value-based 1997 to replace animals culled after the 1996 grazing large daughter groups outside Ireland and more than season. Therefore this study contained 96 first lacta- 75 daughters in Ireland itself. The environments tion animals in 1995, 96 second lactation animals in were three different grass based feeding systems 1996, and 72 third lactation animals in 1997. Buckley, 1998 carried out at Teagasc Moorepark over 3 years. It is important to establish the effects of 2.2. Grass-based feeding systems increased genetic merit on milk production, grass intake, condition score and live weight change on A permanent grassland site was used consisting of production systems based on grazed grass. We can a sward with almost 100 perennial rye grass thus establish possible benefits of using improved Lolium perenne. The grazing season extended from genetics, and to anticipate possible changes in man- early March until late November each year. Cows agement or feeding practices that may be necessary. were housed full time for the months of December, In this paper the effect of genetic merit on milk January and February. The breeding season each production, intake, live weight and condition score year was confined to 13 weeks. It started in late on production systems based on grazed grass will be April and ended in late July. Therefore most of the examined. cows calved from February to April. F . Buckley et al. Livestock Production Science 64 2000 107 –119 109 During the winter indoor period while animals respectively. In the second and third year the HG and were dry, animals were offered grass silage ad MG cows had similar mean calving dates of Feb- libitum. First lactation animals were given a 10-week ruary 22 and 24, respectively. dry period while in subsequent lactations 8 weeks was considered sufficient. Post-calving and prior to turnout to grass early March all animals were offered grass silage ad libitum and a standard 2.3. Silage and concentrate supplementation allowance of 7.9 kg of concentrate DM daily. On turnout to pasture, animals were grazed on a Two concentrates with different ingredient mix- rotational management system Dillon et al., 1995. tures were offered during the experiment. The in- Pre-grazing herbage yields were maintained at be- gredient composition kg t of the concentrate of- tween 1800 and 2200 kg DM ha . 4 cm. Daily fered immediately post-calving until mid-April was concentrate supplementation decreased to 5.3 kg DM unmolassed beet pulp 240, barley 200, maize gluten at turnout up until mid-April. In mid-April each year 350, rapeseed meal 100, fish meal 75, lard 20 and the cows were grouped into blocks of three within minerals and vitamins 15. The concentrate fed for each genetic group on the basis of calving date and the remainder of the year contained kg t unmollas- milk yield. Animals within each block were random- sed beet pulp 510, maize gluten feed 220, barley ly assigned to one of three feeding systems Buckley, 100, lard 10, soya 120 plus minerals and vitamins 1998. Feeding system A incorporated a high stock- 40. All concentrate feeding was offered in individual ing rate 3.0 cows ha, high nitrogen fertilization stalls in the milking parlour in two equal feeds each rate 380 kg N ha and a planned concentrate input day. of 500 kg cow over total lactation Dillon et al., During the first 2 years of the study much larger 1995. Feeding system B had a similar stocking rate levels of supplementation were required than had and nitrogen fertilization rate as system A, but had been envisaged. This was due to the very erratic twice the level of concentrate input. Feeding system grass growth rates experienced in 1995 and the very C had similar concentrate and nitrogen fertilization poor grass growth early in the grazing season in rate at all times as system A but grazed to a higher 1996. However in 1997 due to good grass growth post-grazing sward surface height. This was achieved early in the grazing season, concentrate supple- by reducing the occupancy time per paddock, thus mentation levels were lower than that targeted. Over grazing was more relaxed | 1 cm higher than the the total lactation in 1995, 1996 and 1997; 1056, 804 other two feeding systems. Each system had its own and 517 kg of concentrates were offered per cow. In farmlet consisting of 18 paddocks of on average 0.59 1995 and 1996 it was necessary to supplement cows ha. During the indoor period December–February, at pasture with high quality grass silage. This silage some grass silage from outside the three feeding was harvested from paddocks that were taken out of systems was required. the grazing rotation at herbage yields of greater than The cows remained on these feeding systems until 2500 kg DM ha. Silage supplementation in 1995 housing in mid-November for the first 2 years 1995 amounted to 72 kg DM cow during the grazing and 1996 i.e. as first and second lactation animals. season. Silage was offered from July 10 to July 30 In the third year 1997 when all animals were in owing to a short period of low grass growth rates and their third lactation the experiment terminated in from mid-August to late October due to a long early September 26 weeks in lactation because the period of soil moisture deficit. In 1996 silage supple- herd was slaughtered due to a disease outbreak. mentation was less, being required for a short period The animals were milked twice daily at 06:30 and from July 1 to August 2 when cows were sup- 16:00 h in the first half of lactation and at 07:00 and plemented with 2.6 kg DM cow daily, amounting to 16:00 h in the second half of lactation. The mean 39 kg DM cow. In 1997, from late March when calving date in the first year of the study was cows were on pasture day and night, no grass silage February 5 and 20 for the HG and MG cows, was offered. 110 F . Buckley et al. Livestock Production Science 64 2000 107 –119 2.4. Sward measurements was also measured on three other occasions during the 3-year experimental period. In 1996, individual When cows were outdoors full time, both geno- animal intake was estimated on 40 second lactation types were grazed separately within each feeding cows 20 HG and 20 MG in late December during system. Each paddock had a clearly defined 50:50 the non-lactating period while indoors on grass silage dividing line. Using a temporary electrified wire, it only. Individual animal intake was also estimated in was possible, based on previous post-grazing sward early lactation on 33 third lactation cows 13 HG and surface height, to allocate a different area to each 20 MG in early March, 1997, while cows were genetic group, while maintaining the same post- indoors fulltime and offered silage ad libitum plus grazing height. In each paddock a total of 40 pre- 7.9 kg DM of concentrates daily, and on 34 third and post-grazing sward surface heights were re- lactation cows 16 HG and 18 MG in late March, corded 20 in the HG and 20 in the MG section 1997, when cows were at pasture fulltime and using a sward stick Hutchings, 1991. supplemented with 5.3 kg DM of concentrates daily. Pre-grazing herbage yield above 4 cm horizon was determined on each grazing paddock based on 2.6. Chemical analysis four strips of grass cut with an Agria mower 0.95 m wide, 7 to 9 m long. The grass from each strip was The freeze-dried pre-grazing herbage samples weighed, sampled and a sub-sample was dried were composited for each treatment for each week of overnight at 90 8C for dry matter DM determi- the experiment and analysed for organic matter nation. The remaining herbage from the four samples digestibility OMD Morgan et al., 1989, Kjeldahl from each paddock was bulked and a sub-sample nitrogen and modified acid detergent fibre MADF taken. This sample ca. 100 g was freeze-dried and Clancy and Wilson, 1966. Similarly in periods of used for chemical analysis. silage supplementation, a composite grass silage sample for each treatment for each week was ana- 2.5. Animal measurements lysed for residual moisture, pH, dry matter diges- tibility DMD Tilley and Terry, 1963, Kjeldahl Throughout the 3 years, individual cow milk yield nitrogen, MADF and ash. was recorded on 5 consecutive days week. Milk fat, Concentrates were sampled weekly, bulked over protein and lactose concentration were determined in each 3-weekly period, and analysed for DM, total one successive morning and evening sample of milk nitrogen, crude fibre, neutral cellulase gammonase week using a Fos-let instrument AS N Foss Elec- determination NCGD AFRC, 1993, oil and ash. tric, Denmark. Live weights were recorded weekly and condition score Jefferies, 1961 once every 3 to 2.7. Statistical analysis 4 weeks. Individual animal intake was measured on all The animal production data were analysed by cows on 11 occasions while at pasture over the 3 procedures for a factorial arrangement of treatments years of the study using the n-alkane technique of using the statistical procedures of SAS Statistics Mayes et al. 1986, as modified by Dillon and Analysis Systems Institute, 1991. The model used Stakelum 1989. In 1995, intake estimates took was: place in early May, mid-June, late July and early Y 5 G 1 F 1 B 1 G 3 F 1 e ijkl i j k ij ijkl November, corresponding to 87, 129, 171 and 269 days in lactation, respectively. In 1996, estimates where G, F, B and G 3F were genetic group, took place in early June, late June, late August and feeding system, block and genetic group 3feeding late September, corresponding to 103, 131, 197 and system interaction effects, respectively. The sward 222 days in lactation, respectively. In 1997 estimates measurements taken were analysed using a model took place in late April, late May and late July. that had terms for genetic group, feeding system and These estimates corresponded to 61, 93 and 156 days block. For the purpose of the present study only, in lactation, respectively. Individual animal intake results pertinent to genetic group are presented. F . Buckley et al. Livestock Production Science 64 2000 107 –119 111 Table 1 Chemical composition of grass, grass silage and concentrate offered over the 3 years Grass Grass silage Concentrate a S.D. Silage 1 Silage 2 Conc. 1 Conc. 2 S.D. S.D. S.D. S.D. DM – – 195 25.2 294 88.6 875 0.6 880 4.2 pH – – 3.7 0.00 4.3 0.56 – – – – Composition of dry matter g kg Organic matter digestibility 824 33.7 – – – – – – – – Dry matter digestibility – – 759 35.8 803 27.0 – – – – Crude protein 209 32.4 159 11.0 198 27.2 201 0.6 169 6.1 Crude fibre – – – – – – 84 13.6 108 11.9 Modified acid detergent fibre 208 21.3 314 42.6 262 57.7 – – – – NCGD – – – – – – 822 8.5 841 2.5 Oil – – – – – – 53 3.0 30 3.5 Ash – – 77 0.6 88 8.3 74 2.7 87 2.1 a S.D., standard deviation. Table 2 The effect of cow genetic merit on pre- and post-grazing sward surface heights cm over the 3 years a HG MG S.E.D. Sig. Pre-grazing sward surface heights 20.0 20.0 0.35 NS Post-grazing sward surface heights 6.6 6.7 0.10 NS a S.E.D., standard error of difference; NS, not significant P ,0.05.

3. Results the silage offered while indoors and during periods