P. Dillon

Influence of breed on bovine milk cis-9, trans-11-conjugated linoleic acid content

The influence of animal breed on the profile of fatty acids in milk and particularly on the concentration of cis-9, trans-11 octadecadienoic acid, a conjugated lineoleic acid (CLA) was investigated using four breeds of cows, Irish Holstein/Friesian (IH, n=23), Dutch Holstein/Friesian (DH, n=22), Montbeliardes (MB, n=29) and Normandes (NM, n=27), on pasture. All cows were grazed together in one group. Milk fat CLA concentration from MB were significantly higher (P<0.05) than from DH at one of the two sampling times, while the CLA content of milk fat from NM, IH and DH was not significantly different at either sampling time. Milk fat CLA concentrations between the four breeds ranged from 14.7 to 18.6 mg/g fat, while the variation in milk fat CLA between individual cows within the four breeds ranged from 4.8 to 35.6 mg/g fat. There were significant correlations between milk fat CLA concentrations of individual cows within NM (P<0.001), MB (P<0.001) and IH (P<0.001) and the correlation was close to being significant for DH cows (P=0.076) at two sampling dates. In terms of total fatty acid profiles, DH had higher (P<0.05) C16:0 concentrations than the other breeds. The IH had a higher (P<0.05) C16:0 than the MB. The C18:0 content was higher (P<0.05 at least) in milk fat from NM and MB than from DH and total C18:1 concentrations were close to being significantly higher (P=0.067) in the MB than in the IH. The data indicate that animal breed has some influence over the CLA content of milk and that cows yielding high levels of milk fat CLA sustain this production over time. While there were some significant differences between the breeds in the concentrations of C16:0, C18:0 and C18:1 it is unlikely that they are large enough to be of practical importance.

Dairy cattle breeding objectives combining yield, survival and calving interval for pasture-based systems in Ireland under different milk quota scenarios

Economic values in Irish pounds (IR£) were calculated for milk, fat and protein yields (IR£ cow−1 year−1 kg−1), survival (IR£ cow−1 year−1 % survival−1), and calving interval (IR£ cow−1 year−1 day−1) using a farm model for pasture-based systems in Ireland. Economic values for yield were calculated by changing one of these traits whilst keeping the other traits at the default level, i.e. the economic value for calving interval does not include the costs of higher culling due to a longer calving interval. Herd parameters (e.g. number of milking cows, replacements, youngstock and calving pattern), milk production, energy requirements, feeding ration, land use and labour requirements were re-adjusted to calculate economic performance. Three scenarios were simulated as follows: (S1) milk and fat% quota with a fixed number of cows per farm and quota leasing; (S2) non-quota scenario with a fixed number of cows per farm; and (S3) milk and fat% quota with a fixed output per farm. Sensitivity analysis showed that, with high quota costs and/or lower fat prices, the weighting of fat yield was close to becoming negative in the quota leasing scenario (S1). There was major re-rankings among the top 1000 bulls due to a negative weighting on fat. The results for S1 suggested that the economic values in profit per cow per year are −IR£0.06 per kg milk, IR£0.68 per kg butterfat, IR£4.49 per kg protein, IR£8.98 per % survival, and −IR£1.63 per day calving interval, and the corresponding values in additive genetic standard deviation units were −0.47, 0.19, 1.00, 0.56 and −0.21, respectively.

The effect of strain of Holstein-Friesian cow and feeding system on reproductive performance in seasonal-calving milk production systems

Three strains of Holstein-Friesian (HF) cows: high production North American (HP), high durability North American (HD) and New Zealand (NZ) were assigned, within strain, to one of three pasture-based feeding systems: Moorepark (MP), high concentrate (HC), and high stocking rate (HS). The effects of strain of HF, feeding system and parity on milk production, body condition score (BCS), live weight, energy balance and reproductive performance were studied using a repeated measures model with a factorial arrangement of strain ofHF and feeding systems. Associations between these variables and conception to first service (CONCEPT1), conception to first and second service (CONCEPTl_2), pregnancy rate at 6 weeks (PREG6) and overall pregnancy rate (PREG) were assessed using logistic regressions. When treatment means were compared, the NZ strain had a shorter gestation length and a higher CONCEPT1J2 than both the HP and HD strains. Similarly, the NZ strain had a higher PREG6 and PREG than the HP strain. Feeding system had no significant effect on reproductive performance. The HP strain had the highest milk yield at first AI and peak milk yield, the NZ strain had the lowest milk yield while the HD strain was intermediate. The energy balance of the NZ strain was higher than that of the HP and HD strains. The NZ strain had the lowest live weight and highest BCS; the HD strain had the highest live weight and the HP strain had the lowest BCS. The results show that dairy cows with superior genetic merit for fertility traits have better reproductive performance.

Effects of Breed and Feeding System on Milk Production, Body Weight, Body Condition Score, Reproductive Performance, and Postpartum Ovarian Function

The objective of this study was to investigate the potential differences among Holstein-Friesian (HF), Montbéliarde (MB), Normande (NM), Norwegian Red (NRF), Montbéliarde x Holstein-Friesian (MBX), and Normande x Holstein-Friesian (NMX) across 2 seasonal grass-based systems of milk production. The effects of breed and feeding system on milk production, body weight, body condition score, fertility performance, hormone parameters, ovarian function, and survival were determined by using mixed model methodology, generalized linear models, and survival analysis. The 5-yr study comprised up to 749 lactations on 309 cows in one research herd. The HF produced the greatest yield of solids-corrected milk, the MB and NM produced the least yields, and NRF, MBX, and NMX were intermediate. The NRF had the lowest body weight throughout lactation, the NM had the highest, and the other breeds were intermediate. Body condition score was greatest for MB and NM, least for HF, and intermediate for NRF, MBX, and NMX. The HF had a lower submission rate and overall pregnancy rate compared with the NRF. The NRF survived the longest in the herd, the HF survived the shortest, and the NM, MB, MBX, and NMX were intermediate. Breed of dairy cow had no effect on selected milk progesterone parameters from 5 d postpartum until 26 d after first artificial insemination. Breed of dairy cow did not influence insulin and insulin-like growth factor-1 around parturition or at the start of the breeding season. Animals offered a high-concentrate diet had greater milk yield, but they did not have improved reproductive performance. Differences observed between the different breeds in this study are a likely consequence of the past selection criteria for the respective breeds.

A comparison of different dairy cow breeds on a seasonal grass-based system of milk production: 1. Milk production, live weight, body condition score and DM intake

Abstract The objective of this study was to compare the performance of Dutch Holstein-Friesian (HF), upgraded Irish Holstein-Friesian (CL), French Montbeliarde (MB) and French Normande (NR) dairy cow breeds on a spring calving grass-based system of milk production. The HF cows produced the highest ( P P P P P P

The performance of Holstein Friesian dairy cows of high and medium genetic merit for milk production on grass-based feeding systems

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 ( , 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 ( , 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.

A comparison of different dairy cow breeds on a seasonal grass-based system of milk production: 2. Reproduction and survival

Reproduction and survival characteristics of Dutch Holstein-Friesian (HF), upgraded Irish Holstein-Friesian (CL), French Montbeliarde (MB) and French Normande (NR) cows were compared over a 5-year period (137 lactations per breed), in a seasonal grass-based milk production system. The HF had the highest (P<0.05) milk yield at first AI, and the NR had the lowest milk yield; the values for the other two breeds were intermediate. The MB and NR had higher (P<0.05) live weight and body condition scores at first AI than the HF and CL. Similarly, the MB and NR had higher (P<0.05) nadir live weights and nadir condition scores. The HF had greater (P<0.05) reduction in body condition score from calving to first AI than the other three breeds. At the end of the 14 weeks of breeding, significantly (P<0.05) more of the HF cows (26.3%) were not pregnant than the CL cows (16.1%); both of these non-pregnancy levels were higher than the corresponding MB (8.8%) and NR (8.1%) levels. Similarly, the pregnancy rate to first AI of the HF was lower (P<0.05) than the MB and NR. Furthermore, the HF cows had extra number of days from calving to conception than the other three breeds (P<0.05). Dairy cow breed had a significant effect on survival; 20.6, 39.7, 49.2 and 55.8% to day 2500 for the HF, CL, MB and NR, respectively. The results of the present study indicate that the reproductive performance and survival of HF with a large proportion of North American genes are low in a seasonal grass-based milk production system.

THE INFLUENCE OF COW GENETIC MERIT FOR MILK PRODUCTION ON RESPONSE TO LEVEL OF CONCENTRATE SUPPLEMENTATION IN A GRASS-BASED SYSTEM

The objective of this study was to investigate if there is a genotype ✕ feeding system interaction for milk production in Holstein-Friesian dairy cows. For this purpose, 48 high genetic merit (HM) and 48 medium genetic merit (MM) dairy cows, were used in a two (genotypes) ✕ three (levels of concentrate feeding) randomized-block design experiment in three consecutive years. In year 1, all animals were in their first lactation, while in year 2 and year 3, 18 and 12 first lactation cows replaced animals culled at the end of the previous lactation. A total of 66 cows remained in the study in the same feeding system for the 3-year duration of the study. Concentrate feeding levels were 376, 810 and 1540 kg per cow per lactation; these were identified as the LC, MC and HC feeding systems respectively. There was a separate farmlet for each feeding system; farmlets were managed so that pre-grazing and post-grazing herbage height were similar for all three feeding systems. When compared on treatment means there was a significant genotype ✕ feeding system interaction for fat yield, while for mean solid-corrected milk yield the interaction was close to statistical significance (P = 0·07). However, regression coefficients of both milk and protein yield on pedigree index for milk and protein yield were significantly different between the LC and the HC. The interaction between feeding system and the regression of both on pre-experimental milk and protein yield were close to statistical significance (P = 0·08 and P = 0·09 respectively). Outputs of milk, fat, protein and lactose were greater for the HM than the MM cows. Feeding system had a significant effect on milk, fat, protein and lactose yields. There was a significant genotype ✕ feeding system interaction for body condition score (BCS) at the end of lactation; the MM cows had a higher rate of body tissue repletion than the HM cows especially in the HC system. The results suggest that there is a genotype ✕ concentrate feeding level interaction and that feeding systems developed in the past for animals of lower genetic merit may require adaptation if they are to be optimal for higher genetic merit animals.

Body condition score and live-weight effects on milk production in Irish Holstein-Friesian dairy cows

The objective of the present study was to quantify the relationships among body condition score (BCS; scale 1 to 5), live weight (WT) and milk production in Irish Holstein-Friesian spring calving dairy cows. Data were from 66 commercial dairy herds during the years 1999 and 2000. The data consisted of up to 9886 lactations with records for BCS or WT at least once pre-calving, or at calving, nadir or 60 days post-calving. Change in BCS and WT was also calculated between time periods. Mixed models with cow included as a random effect were used to quantify the effect of BCS and WT, as well as change in each trait, on milk yield, milk fat concentration and milk protein concentration. Significant and sometimes curvilinear associations were observed among BCS at calving or nadir and milk production. Total 305-day milk yield was greatest in cows calving at a BCS of 4.25 units. However, cows calving at a BCS of 3.50 units produced only 68 kg less milk than cows calving at a BCS of 4.25 units while cows calving at 3.25 or 3.00 BCS units produced a further 50 and 114 kg less, respectively. Cows that lost more condition in early lactation produced more milk of greater fat and protein concentration, although the trend reversed in cows that lost large amounts of condition post-calving. Milk yield increased with WT although the marginal effect decreased as cows got heavier. Milk fat and protein concentration in early lactation also increased with WT pre-calving, calving and nadir, although WT did not significantly affect average lactation milk fat concentration.

Estimation of genotype×environment interactions, in a grass-based system, for milk yield, body condition score, and body weight using random regression models

Abstract (Co)variance components for milk yield, body condition score (BCS), body weight (BW), BCS change and BW change over different herd-year mean milk yields (HMY) and nutritional environments (concentrate feeding level, grazing severity and silage quality) were estimated using a random regression model. The data analysed included records from 7478 multiparous upgraded Holstein–Friesian dairy cows. There were G×E interactions for BCS across all environments and for BW change across different concentrate levels and silage quality environments. There was a three-fold increase in the genetic standard deviation (S.D.) for BCS change to day 60 of lactation (CS60-5) and a doubling of the genetic S.D. for BCS at day 5 (CS5) as silage quality improved. The genetic variance for CS60-5 increased as concentrate level increased and as grazing severity became tighter. There was significant re-ranking of animals for milk yield, CS5 and CS60-5 over the different HMY environments; genetic correlations fell to −0.60 between extreme HMY environments for CS60-5 and were as low as 0.41 for CS5 across different HMY environments.