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Item Investigating the pathogenesis of catastrophic humeral fractures in dairy heifers in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Science at Massey University, Palmerston North, New Zealand(Massey University, 2022) Wehrle Martinez, Alvaro SebastianCatastrophic outbreaks of spontaneous humeral fractures in dairy heifers in New Zealand have given rise to animal welfare problems and resulted in significant economic losses to the New Zealand dairy industry. Preliminary small sample size studies have identified potential causes and/or factors associated with the occurrence of humeral fractures including periods of protein-calorie malnutrition, increased osteoclastic bone resorption related to lactation, and low liver and/or serum copper concentration (suggestive of periods of copper deficiency). Nevertheless, outbreaks of humeral fractures still occur throughout New Zealand with devastating consequences. Therefore, the main objective of this thesis was to investigate the likely causes and/or major risk factors associated with the occurrence of spontaneous humeral fractures in dairy heifers in New Zealand and propose a likely pathogenesis of the condition. For this, a large cohort of bone samples (humerus and ribs), as well as liver and blood/serum samples were collected from 2-year-old dairy heifers that suffered spontaneous humeral fracture post calving (affected heifers) for comparison with age-matched post-calving heifers with no bone fractures (control heifers). Blood/serum samples, used for the determination of biochemical profile in affected heifers, showed increased B -hydroxybutyrate and decreased creatinine concentration indicative of negative energy balance and/or periods of undernutrition. Bone samples were used for gross, histologic, histomorphometric, Raman and Fourier transform infrared spectroscopic analysis as well as for the measurement of the collagen and collagen crosslink content in bones from affected heifers compared with control heifers. Histologically affected humeri had osteoporosis (reduction in trabecular volume with abnormal trabecular architecture, thicker growth plates with abnormal architecture, increased resorption in the distal humerus, and a thinner cortex with increased and abnormal resorption. Abnormal cortical resorption increased the probability of fracture 54.2 times and reduced trabecular density 249.5 times. Spectroscopic analysis indicated decreased bone quality in the humeri from affected heifers with a reduced amount of bone organic and mineral components, lower mineralisation, lower carbonate substitutions, increased bone remodelling, and reduced mineral crystallinity. Analysis of collagen content and collagen crosslinking using liquid chromatography indicated reduced total collagen content and increased collagen crosslinking in the humeri from affected heifers. Finally, a survey was conducted using farms that have and have not had a case of humeral fractures showed Holstein-Friesian Jersey cross breed was a possible risk factor. The likely causes and/or major risk factors associated with the occurrence of spontaneous humeral fractures in dairy heifers in New Zealand include breed, protein-calorie undernutrition during important bone growth periods (which significantly affected the bone chemical composition and architecture) and increased abnormal bone resorption. These factors have significantly compromised bone mechanical strength and led to the spontaneous humeral fracture.Item Broken shoulders in dairy heifers in New Zealand : investigating the relationship between live weight and bone morphology in the bovine forelimb : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand(Massey University, 2021) Gibson, MichaelaSpontaneous humeral fractures in first lactation dairy heifers are a significant economic and welfare issue in the New Zealand dairy industry. With approximately 4% of dairy farms being affected and, within farm, up to 25% of replacement heifers lost, the cost to the dairy industry is estimated to be over $10 million. Preliminary observations from Dittmer et al. (2016), showed the presence of growth arrest lines in bones from affected heifers, indicating a period of malnutrition in the heifer’s life. However, with little known about how heifer’s bones grow within the New Zealand pastoral system, it is difficult to identify developmental time periods that have the greatest impact on long bone growth and, therefore, greatest potential to affect the risk of fracture. Therefore, the aim of this thesis was to investigate the relationship between live weight and bone morphology in the bovine forelimb to identify potential risk periods for spontaneous humeral fractures in first-lactation dairy heifers. In this thesis, the metacarpus and humerus were opportunistically collected from cattle from a variety of experiments carried out at Massey University and from samples submitted from farms throughout New Zealand. Measures of bone morphology in the metacarpus were highly correlated with the same measure in the humerus (R²=0.89-0.98). Measures of the humerus and metacarpus were also highly correlated with live weight at all ages. However, the relationship between bone and live weight changed over time demonstrating differences in bone maturity. Distal regions of the forelimb such as the metacarpus matured by one year of age as indicated by a different relationship between live weight and pQCT measures of the humerus at 24 months compared with 8-12 months of age. However, proximal regions of the forelimb such as the humerus continued to grow after a year of age. Differences in proximal and distal bone growth were reflected in the pattern of stature growth. A cohort of dairy heifers (Holstein Friesian, Jersey, and Holstein-Friesian cross Jersey) were measured for live weight, height, wither-rump length, girth, and distal and proximal forelimb length (stature) from birth to 15 months of age. As live weight increased, the contribution of the distal limb to increases in height decreased, which is consistent with knowledge that physeal closure in cattle occurs earlier in distal limb bones, such as the metacarpus, than in proximal limb bones, such as the humerus. Finally, bones collected from heifers affected and unaffected by spontaneous humeral fractures were compared and the effect of copper status on bone measures was examined. The mid diaphysis of the humerus of the affected group had reduced cortical bone mineral density (p<0.05) and a trend for reduced cortical content and total bone content which contributed to a reduced stress-strain index. A trend for reduced bone length in affected humeri provides additional support for the hypothesis of inhibited humeral growth. Heifers with low liver copper concentration had reduced humeral length and reduced cortical bone mineral density (p<0.05). Growth and fracture data presented in this thesis support the hypothesis that the most likely developmental period in which inadequate bone growth occurs in heifers subsequently affected by humeral fracture is in the months leading up to the event, which coincides with the animal’s second winter.Item Determining the utility of adolescent live weight data to predict two-year-old live weight in New Zealand dairy cattle : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science, Master of Science in Animal Breeding and Genetics at Massey University, A L Rae Centre for Animal Breeding and Genetics, Waikato, New Zealand(Massey University, 2019) Stephen, Melissa AnneThe purpose of this research was to establish the utility of adolescent live weight data measured across cohorts of growing animals for predicting live weight in first lactation. Live weight is associated with the growth and maintenance feed requirements of a cow. Selection that simultaneously takes account of milk income and feed requirements of dairy cattle can increase future farm profitability. Estimated breeding values (EBVs) for mature cow live weight are currently predicted using Live weight phenotypes measured during actation. Breeding companies in NZ actively measure the first lactation live weight of a small proportion of the nation’s dairy cows—the daughters of their bulls—to improve their ability to identify superior bulls. Accurate EBVs obtained at an earlier age can allow reliable selection of superior young bulls which would shorten the generation interval, increasing the rate of genetic progress. The purpose of this research was to determine the utility of adolescent live weight (i.e. live weight prior to first lactation) for predicting variation in live weight measured in first lactation. We completed two studies. In the first study (Section 4), we produced the (co)variance parameters for live weights measured at four ages, from six months old through to first lactation. Our hypothesis for this study was that live weight measured through adolescence would share a strong positive genetic relationship with live weight measured during lactation. Our results support this hypothesis, as estimates of genetic correlations between weights at different ages ranged from 0.79 to 0.97. In the second study (Section 5), we produced live weight EBVs using live weight measured though adolescence. For comparison, we produced EBVs using just live weight measured during first lactation. Our hypothesis was that the accuracy of the live weight EBVs would be improved by including adolescent live weight. Our results showed that including adolescent live weight phenotypes improved the accuracy of the live weight EBVs for animals with adolescent live weights, and their progeny. We concluded that adolescent live weights are a useful predictor of live weight later in life, and should be incorporated as a predictor trait for the national live weight EBV in NZ.Item The growth and development of dairy heifers fed a low, high and ad libitum allocation of milk replacer : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University, Manawatū, New Zealand(Massey University, 2019) Groenendijk, MattesFeeding calves more milk has been shown to increase their pre-weaning growth rate and is associated with improved lifetime performance, but few studies have determined the effect of providing greater milk allowance on the feed intake and growth of heifer calves in New Zealand dairy farming systems. The objective of this study was to determine the effect of 3 different milk replacer (MR) allowances when allocated via automated feeding machines on the feed intake, growth, mammary gland development and grazing behaviour of dairy heifers (Holstein- Friesian x Jersey) in a pastoral system. Calves were allocated MR at either a low allowance, fed at 10% of initial body weight (BW) (LA; n = 67), a high allowance, fed at 20% of initial BW (HA; n = 65) or an ad libitum allowance (ADLIB; n = 66). Weaning began after 69 days on the study by gradually reducing MR allowance over 14 days, so that weaning was concluded by 83 days. All calves had free access to pelleted calf starter via automatic feeders until 121 days, and to ryegrass hay from 21 to 91 days. Calves were put outdoors and given access to pasture at 91 days. Calves that were fed more MR had greater total dry matter intake and greater growth rate before weaning (ADLIB > HA > LA; P < 0.01), but ADLIB calves had lower intake of calf-starter and lower growth rate in the first 5-weeks after weaning than HA and LA calves (P < 0.01). At 6 months of age, ADLIB and HA calves were heavier than LA (P < 0.05), but there was no difference in BW at 10 months of age. Pre-weaning growth rate was positively associated with BW at 6 months of age (R2 = 0.37; P < 0.01) but was not related to post- weaning growth rate. Pre-weaning growth of the mammary parenchyma, as measured by ultrasonography, was greater in LA than ADLIB calves (P < 0.05) but there was no difference in the mammary fat pad or total gland growth. A subset of calves (n = 28) had their behaviour monitored on 4 occasions over a 5-week period, beginning a day after being given access to pasture. One day after being given access to pasture, ADLIB calves spent more time grazing than LA calves, and LA calves spent more time ruminating than HA and ADLIB calves (P < 0.05). There was no difference among treatments in grazing behaviour at subsequent observations. This study demonstrates that group-housed crossbred heifer calves have greater pre-weaning growth rates when fed more milk (10% of initial BW vs 20% of initial BW vs ad libitum feeding), and maintain this weight advantage to 6 months, but not to 10 months of age when grazing pasture. The impact of increased pre-weaning growth rate and the effect of differences in pre-weaning mammary gland development on future lactation performance of heifers in a pastoral system require further investigation.Item Live weight and growth of dairy heifers are important for subsequent milk production and reproductive performance : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science, Massey University, Turitea, Palmerston North, New Zealand(Massey University, 2019) Handcock, Rhiannon ClareIn the pasture-based farming systems that occur in New Zealand, dairy heifers tend to follow a seasonal pattern of growth in response to pasture quality and availability. The industry recommended liveweight-for-age targets for dairy heifers are 30% of mature liveweight (LWT) at 6 months of age, 60% at 15 months of age and 90% at first calving. Target growth rates are calculated by linear interpolation, thereby creating a mostly linear planned trajectory of growth from three to 22 months of age. The general aim of this thesis was to investigate the effects of LWT and growth on dairy heifer performance in the New Zealand pasture-based system. In this thesis, LWT records from 189,936 spring-born dairy heifers were provided by Livestock Improvement Corporation to model growth curves from three to 22 months of age. Holstein-Friesian (F) heifers were heavier than Jersey (J) heifers from three to 22 months of age, and FxJ crossbred heifers were heavier than the mean of the purebreds due to positive heterosis effects. Additional data of calving dates and milk production records were provided by Livestock Improvement Corporation. Live weight between three and 21 months of age had significant impacts on milk production and reproductive performance. As LWT of heifers increased, milk production and probability of calving and calving early increased up to a maximum. Further increases in LWT past the maximum point did not result in increases in milk production, and for reproduction (stayability and calving rate) resulted in a decline in probability. For heifers that were below average in LWT, significant improvements to milk production and reproductive performance would be expected by increasing LWT. For example, the mean LWT of 15-month-old Holstein-Friesian-Jersey crossbred (FJ) heifers was 301.5 kg. These “average” heifers were estimated to produce 436 and 1,477 kg more energycorrected milk (ECM) than “below average” 250 kg heifers in first-lactation and threeparity accumulated yields, respectively. Additionally, stayability to first, second and third calvings were superior for “average” heifers (93.6 vs 89.3% for first, 78.2 vs 70.6% for second and 64.7 vs 57.5% for third) and first calving 21-day calving rate (C21_2yo; 81.9 vs 78.0%) compared with “below average” heifers. For heifers that were above average in LWT, significant improvements to milk production would be expected by increasing LWT, however, at the heaviest LWTs a reduction in reproductive performance would be expected. For example, FJ heifers that were 375 kg at 15 months of age were estimated to produce 554 and 1,434 kg more ECM than “average” 300 kg heifers in first-lactation and three-parity accumulated yields, respectively. However, stayability and C21_2yo were similar for 375 kg (93.4%, 78.9%, 63.8% and 79.8% for stayability to first, second, third calving and C21_2yo, respectively) and 300 kg FJ heifers. Heifers that were at the heaviest LWTs, for example, 425 kg at 15 months of age were estimated to have the greatest ECM yields, but had a lower stayability and C21_2yo compared with “average” heifers (88.4%, 72.5%, 55.3% and 76.8% for stayability to first, second, third calving and C21_2yo, respectively). The greatest benefits to both reproduction and milk production would be expected by increasing LWT of the lightest heifers at each age studied. In a prospective study, milk production did not differ between heifers that grew in a seasonal manner (slow then fast) compared with the target growth trajectory (linear) between six and 15 months of age. There was a difference in the age at which puberty was attained, such that heifers that grew to the target growth trajectory were younger at puberty compared with those grown in a seasonal manner, however, there was no difference between treatments in the date of first calving or first lactation milk production. These results indicate that there were limited disadvantages to growing heifers slower over their first winter, provided they caught up to target LWT by first mating. Overall the results of this thesis indicate that having heifers heavier through the precalving rearing phase (three to 21 months of age) has the potential to improve reproductive success and milk production, with the greatest advantage seen by increasing LWT of the lightest heifers. This information can be used to develop guidelines which may improve productivity and survival of dairy cattle in New Zealand.Item Effect of differing forages on the early growth and behaviour development of dairy heifers during pre- and post weaning periods : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand(Massey University, 2017) Ullah, ZakaThe objective of this study was to evaluate the effects of different forage diets fed to young calves on early growth, behaviour development and long term milk performance. In experiment 1, 60 calves were randomly allocated to one of three diets, fed starter diet with no forage (PS), PS with additional moist alfalfa (PSA) or PS with additional pasture hay (PSH). In experiment 2, 108 calves were randomly allocated to one of three diets, PSH, PS with low (LF) or high (HF) moist alfalfa based total mixed rations. In Experiment 1, greater dry matter intake and liveweights were observed in PSH followed by PSA and then PS during the pre- and post-weaning periods. Longer time eating and ruminating behaviours were observed in PSA and PSH than PS during pre- and post-weaning periods. In Experiment 2, greater dry matter intake and liveweights were observed in PSH than LF and HF diets during the pre- and post-weaning periods. Greater numbers of incidents of allo-grooming were observed in the HF and PSH diets and calves spent longer time eating than LF calves. During post-weaning period, HF and PSH fed calves spent more time lying than LF fed calves. After turning out to pasture, no behaviour differences were observed among treatments in both experiments. While monitoring long term performance, no differences were observed in animals from Experiment 1 in terms of liveweight, milk yield, protein or fat production. From Experiment 2, greater liveweight gains were observed in HF and PSH fed animals than LF fed animals till first lactation. During first lactation, greater milk yield was observed in HF fed animals than PSH or LF fed animals. Greater fat production was observed in LF fed animals than HF or PSH fed animals during third lactation. The effects of diets on the long term performance of the animals should be repeated with sufficient animal numbers per treatment.Item Compudose, its effects on Hereford X Friesian heifers : a thesis presented in partial fulfilment of the requirement for the degree of Master of Applied Science (in Animal Science) at Massey University(Massey University, 1997) Burke, Jennifer LCompudose is an oestrogenic growth promotant that improves liveweight gain and feed conversion efficiency in steers. In the past it has not been recommended for use in breeding heifers because of the adverse effects of oestrogen treatment on reproductive performance. The effects of Compudose on liveweight gain, skeletal development, lactational performance, carcass characteristics and offspring performance in heifers at pasture are unknown. However, the expected increase in liveweight gain from Compudose treatment may allow target growth rates to be attained in heifers at critical times of the year, without lactational performance being affected. This study investigated the effect of treating Hereford x Friesian (H x F) once-bred heifers (OBH) with Compudose 400 at 3 months (90 days) of age (Compudose 90) and 7 months (210 days) of age (Compudose 210) compared to non-treated heifers (Control). Compudose 90 heifers (n = 14) gained 0.63 kg/day compared with Control heifers (n = 17) which gained 0.59 kg/day for 385 days from the time of implantation (6.8% increase, P < 0.05). Subsequently Compudose 90 heifers achieved greater liveweights than Control (P > 0.05) and Compudose 210 (n = 17) heifers (P < 0.05) at pre-mating (by 17.7 kg and 16.9 kg, respectively), pre-calving (by 13.7 kg and 25.3 kg, respectively), weaning (by 13.9 kg and 32.8 kg, respectively) and slaughter (by 23.1 kg and 39.9 kg, respectively). Liveweight gain between Control and Compudose 210 heifers did not differ over the 383 day period of implantation. Carcasses of Compudose 90 heifers were 10.5 kg heavier than carcasses of Control (P > 0.0.5) and 19.2 kg heavier than carcasses of Compudose 210 heifers (P < 0.05). Wither height, girth, hip height, hip width, pelvic height and pelvic area did not differ significantly between treatment groups, but pelvic width of Compudose-treated heifers was significantly smaller than that of Control heifers (P < 0.01). Compudose 90 and Compudose 210 heifers had an average calving date 8 days (P < 0.10) and 10 days (P < 0.05), respectively, later than the average calving date of Control heifers, and more compact calving spreads. There were no treatment differences in calf birthweight, however calves born to Control heifers were 15.3 kg and 16.2 kg heavier at weaning than calves born to Compudose 90 and Compudose 210 heifers (P < 0.05). Compudose treatment and associated higher growth rates did not affect milk yield, as determined by the weight-nurse-weigh (WNW) method, at 4 and 8 weeks of lactation; udder volder volume at 4 weeks, 8 weeks and 12 weeks of lactation (weaning), and at pre-slaughter; or udder weight at slaughter. There were no significant differences in carcass quality characteristics between treatment groups. However, carcasses of Compudose-treated heifers tended to be shorter (P < 0.10) and have a greater rib-eye area. No significant differences in fat content, as determined by the weight of kidney and pelvic fat and fat depth, were detected between treatment groups. Implanting heifers with Compudose at 3 months of age is more beneficial than implanting heifers with Compudose at 7 months of age, but the small liveweight gain advantage would not be economically advantageous. It is concluded that Compudose is not a practical solution for improving the rearing of beef or dairy heifers, despite lactational performance not being affected.Item Effects of monensin delivered by a slow release device on aspects of performance in dairy heifers : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy in Veterinary Clinical Sciences at Massey University(Massey University, 1993) Arias Navarro, Gerardo AugustoTwo series of trials (from August 1991 to February 1992 and from April to July 1992) were conducted to evaluate the effect of monensin on the growth, reproductive performance and Eimeria oocyst counts of dairy heifers in New Zealand. Two hundred heifers were divided according to their weight into two groups at the beginning of the trials. Heifers with similar weights were assigned randomly to either of two treatments: with or without monensin boluses that delivered 200 mg of monensin per day. Monensin had no effect on weight gains in both parts of the trial. A significant increase in height was observed during the second part of the trial. Monensin significantly decreased (p<0.05) the oocyst counts in both parts of the trial and plasma progesterone levels 100 days after the first administration of boluses. Although conception rates and age of heifers at calving were not affected by monensin, the weight of calves was significantly increased by the ionophore. These results indicate that monensin can influence reproductive performance of heifers without affecting their body weight. In addition, its properties as a coccidiostat were confirmed.Item Influence of plane of nutrition on the productivity of Angus heifers : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Animal Science at Massey University(Massey University, 1977) Anderson, Warren JamesThis experiment was designed to study the influence of autumn live weight and nutritionally-enforced live weight change on calf birth weight and the subsequent productivity of three-year-old, primiparous Angus heifers, calving in the spring of 1975. All heifers were pasture fed on "Tuapaka", No. 3 sheep farm, Massey University, and the treatments imposed followed those normally experienced by cattle on hill country. This was achieved by altering pasture intake by the manipulation of stocking rate during first pregnancy. The research herd of 54 heifers was comprised of animals reared to two-and-a-half-years-of-age at three different origins, namely Massey (Tuapaka), Hawke's Bay and Wairarapa, which consequently gave the three autumn live weight groups. On 1 May, 1975, a switchover design for pre-calving nutritional plane was initiated by allocating heifers within origin to one of three treatment groups. The first group of 19 heifers was fed at a high plane continuously to calving. A second group of 18 heifers was fed at a high plane of nutrition for 70 days (to 10 July, 1975) until three weeks before the start of calving (30 July, 1975). The third group of 17 heifers was fed on a low plane of nutrition from 1 May to 10 July, 1975, when it was switched to a high plane. The three groups were identified as HP-HP, HP-LP and LP-HP, respectively. The least squares means for the live weight of the groups at the start of the experiment, at switchover 70 days later, and at the last weighing date before calving were: 1 May, 1975: HP-HP, 382.4kg; HP-LP, 382.0kg; LP-HP, 380.1kg (NS). 10 July, 1975: HP-HP, 381.3kg; HP-LP, 382.1kg; LP-HP, 362.2kg (p<0.01). 25 July, 1975: HP-HP, 395.7kg; HP-LP, 376.0kg; LP-HP, 375.0kg (p<0.01). The live weight of the heifers, as classified by origin at the last weighing date before calving (25 July, 1975), did not differ from that at the start of the experiment (1 May, 1975) by more than 1.7kg. The least squares means for the weight of the heifers of the origin groups at 25 July was: Massey, 367.8kg; Hawke's Bay, 407.4kg; Wairarapa, 371.7kg, The Hawke's Bay heifers were significantly (p<0.01) heavier than those from the other two origins. The first order interaction between winter nutritional regime and autumn live weight was not significant. The birth weight of the calf was not significantly influenced by the plane of nutrition of the dam or her autumn starting weight. Within treatments, the least squares means for birth weight were: HP-HP, 27.8kg; HP-LP, 25.7kg; LP-HP, 25.9kg. The maximum difference was 2.1 kg. (0.05Item Relationships between behavioural traits, residual feed intake, and average daily gain in growing dairy heifers fed lucerne cubes : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University, Palmerston North, New Zealand(Massey University, 2012) Green, Talia CorinaResidual feed intake (RFI) is a measure of an individual’s efficiency in utilising feed for maintenance and production during growth or lactation. It can be defined as the difference between the actual and predicted feed intake of that individual. Efficient animals eat less than predicted for their body weight and level of performance, and inefficient animals eat more. The objective of this study was to investigate possible relationships between RFI and behavioural traits, such as feeding behaviour, social dominance, and activity in young dairy heifers. The intakes and liveweights of 1049 growing dairy heifers (6-8 months of age, 195 ± 25.8 kg liveweight) in five cohorts were measured for 42-49 days to ascertain individual RFI. Animals were housed in an outdoor feeding facility comprising 28 pens, each with eight animals and one feeder per pen, and were fed a dried, cubed lucerne diet. An electronic feed monitoring system measured the intake and feeding behaviour of individuals. Intake was moderately to strongly correlated with RFI for individual cohorts (r = 0.54-0.74; p < 0.001), indicating that efficient animals ate less than inefficient animals. Several other feeding behaviour traits were related to RFI, but the relationships were weak (r = 0.14-0.26; p < 0.05) suggesting that feeding behaviour is not a reliable predictor of RFI in growing dairy heifers. Statistical comparison of the extremes of RFI (104 most and 104 least efficient) showed that the most efficient animals (low-RFI) had similar liveweight and average daily gain to the least efficient (high-RFI) (p > 0.05) but ate less (mean ± SED; 6.97 v 8.75 ± 0.10 kg cubes), had fewer meals (6.3 v 8.2 ± 0.61/d), shorter daily feeding duration (2.71 v 2.85 ± 0.07 h), ate longer meals (35.6 v 30.6 ± 1.54 min/meal), and ate more slowly (45.4 v 53.0 ± 1.36 g cubes/min) than the least efficient animals (all p < 0.05). These groups also differed in their feeding patterns over 24 h. Video recordings of 32 animals showed that daily activity included (mean ± SEM) 15.4 ± 0.5 h lying, 4.8 ± 0.5 h standing, and 2.9 ± 0.1 h feeding. However, neither social status nor activity were related to RFI in this study (p > 0.05). Feeding behaviour explained only a small proportion of the variation in RFI in dairy heifers. Selecting animals for low RFI (efficient) is unlikely to affect social dominance and activity, although these results should be confirmed in a grazing environment representative of most New Zealand dairy farms.