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Item Feed intake capacity and reproductive performance in Holstein-Friesian cows differing genetically for body weight : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Animal Science, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand(Massey University, 2000) Caicedo Caldas, AlfredoThe work outlined in this study was intended to evaluate some differences between cows from two genetic lines of Holstein-Friesian (HF) cows, which have been selected for either heavy or light live weight, but are of similar high genetic merit for milk production. The two aspects studied in this thesis were, feed intake capacity and their reproductive performance because these characteristics can have important effects on efficiency of the cow, and they may be affected by selection for live weight. In both 1998 and 1999, 16 and 24 pregnant non-lactating high genetic merit Holstein-Friesian cows, which differed genetically in size and weight, were selected from the high (H) and low (L) breeding value for live weight (LW) herd at DCRU Massey University, with eight and 12 animals for each line in 1998 and 1999 respectively. These were fed to appetite on hay (7.52 MJ ME/kg DM in 1998) and on pasture (11.1 MJ MD/kg DM in 1999) in order to measure the maximum voluntary feed intake capacity. The difference between the strains in DMI per cow per day was highly significant (P<0.01) in both years. The heavy cows ate 12.52 kg DM of hay and 13.10 kg DM of pasture in 1998 and 1999 respectively, while the light cows consumed 11.11 kg DM of hay and 11.63 kg DM of pasture in 1998 and 1999 respectively. The regression coefficients generated show that for each 100 kg increase in LW, daily dry matter intake per cow increased by 1.43 and 1.81 respectively in 1998, and 1999, a positive correlation between DMI/cow/day and live weight. Overall least squares means values for DMI/cow/day in 1998 and 1999 were 11.81 and 12.36 which indicates that cows in the first year ate 4.4% less hay DM/cow/day than cows on pasture in the second year. Similarly, the overall least squares means values for DMI/cow/day for H and L cows were 12.81 and 11.37, which indicates that H cows ate 11.2% more DM than L cows. The relation between metabolizable energy intake (MEI)/cow per day and LW was also significant (P<0.01) and (P<0.05) for both years 1998 and 1999 respectively. Least squares means for MEI by line as a treatment and after adjustment by parity number were 94.5 and 144.7 MJ ME/cow per day for the H cows, and 83.9 and 128.4 MJ ME/cow per day for the L cows, in experiment one and two respectively. Regression analysis of the data after conversion into log10, showed that DMI increased in proportion to LW0.66 and LW0.65 in 1998 and 1998 respectively. These results indicate that lighter cows are not disadvantaged relative to the heavier cows in their capacity to eat feed in excess of their maintenance requirement, which are generally assumed to increase in proportion to LW0.75. The reproductive performance of Holstein-Friesian cows differing genetically for live weight at Massey University was evaluated for the 1998-1999 period. The aim of the study was to evaluate and compare the reproductive performance of the heavy (H) and light (L) cows two year old, three year & older and all age groups. Differences between genetic lines were evaluated for calving intervals: three week calving rate, calving to first service (CFS), planned start of mating to first service (PSMFS), calving to conception (CC), planned start of mating to conception (PSMC), first service to conception (FSC) and calving interval (CI) and percentage of induced cows. In addition, 21 days submission rate (SR), conception rate to first service (CRFS), percentage of cows treated with CIDRs and empty rate were also evaluated. Light cows showed a more concentrated calving pattern than the H cows, and a higher percentage of L cows calved in the first 3 weeks than H cows (72% and 62% respectively). Cows in the H line had a higher proportion of induced calvings. There were no significant differences between H and L cows in CFS, CC, PSMC, FSC and CI. However, the difference in PSMFS between the strains was significant (P<0.01): H cows had shorter intervals than L cows (8 days and 13 days respectively). Submission rate at 21 days was significantly higher (P<0.001) for H cows than L cows (96% and 85% respectively), and H cows had lower CRFS than L cows (50% and 74% respectively; P<0.05). Similarly H cows tended to have a higher proportion of empty rates and CIDRs than the L cows. The combination of lower conception rate at the first insemination and the later calving extended the conception and calving pattern for the H cows and at the same time increased the probability of an induced calving. These results indicate that light cows had higher CRFS, achieved a more concentrated calving pattern and fewer needed to be induced to calve than heavier cows.Item Uterine involution in Holstein-Friesian cows genetically selected for high or low mature body weights :|ba thesis presented in partial fulfilment of the requirements for the Master of Veterinary Science at Massey University, Palmerston North, New Zealand(Massey University, 2008) Daoud, Fadi ZakiThe main objective in dairy herds is to produce milk as economically and efficiently as possible. To achieve maximum production, cows must calve regularly; hence the fertility of the herd affects the productivity of the farm dramatically. High fertility requires early uterine involution, early onset of oestrous cycles postpartum and optimal oestrus detection and conception rates (Pelssier 1976). The modern high producing, lactaling dairy cow in North America is subfertile (Thatcher et al., 2006) as managed under current production systems. However, whether such subfertility occurs in high-producing cows under our pastoral system in New Zealand is not fully known. However, recent movement of genetic material across the globe, in the form of semen or frozen embryos might suggest that New Zealand herds could be drifting in a similar direction in subfertility. The main objective of the present study was to investigate the effect of genetics on uterine involution in the context of a pastoral system by comparing two strains Holstein/Friesian cows that had been genetically selected for high (H) or low (L) mature body weight. Involution was studied through the following measurements: (i) cervical diameter, as assessed by measurement per rectum, (ii) plasma concentrations of the prostaglandin F2α metabolite, 15-keto-13,14-dihydro-prostaglandin F2α (PGFM), (iii) urinary concentrations of the collagen breakdown product pyridinoline and (iv) bacteriology of the cervical canal. From the results, it was concluded that, whilst H cows exhibited similar physical involution characteristics to those of L cows (P>0.5), they had higher levels of post-calving bacterial contamination (P<0.05). On Days 4, 7 and 10 post partum, the anaerobic bacterial load was significantly (P<0.05) greater in H than L cows. On Day 10, both strains peaked with mean anaerobic bacterial counts of 23.4 x 105 cfu and 0.41 x 105 in H and L cows, respectively. Similarly, on Days 7 and 10, the total bacterial load (aerobic plus anaerobic) was also greater (P<0.05) in H than L cows. On Day 7 mean total bacterial counts were 2.27 x 106 cfu in H cows. Peak numbers of bacteria in H cows were attained on Day 10 (3.39 x 106 cfu). Values in L cows were maximal on Day 7 (1.18 x 106 cfu). PGFM Concentrations in L cows were significantly (P<0.05) higher than in H cows on Days 17, 28 and 35. Although total pyridoline and deoxypyridoline /creatinine ratio concentrations differed between strains and times, the strain.time interaction term was not significant. However, on Day 11, values in L cows tended (P=0.07) to be higher than in H cows. Simple correlations established that different parameters e.g cervical diameter; PGFM, PYD and bacterial contamination are highly correlated and moving simultaneously together and are not independent of each other. Accordingly, the relationships between actual and predicted intervals between calving and; first oestrus, first insemination and conception, were calculated based on principle component and partial regression analyses of parameters of uterine involution. Indices calculated from these parameters as predictors of reproductive outcomes, were significantly correlated with intervals between calving and first oestrus (P<0.05) and calving and first insemination (P<0.01), but not significant with conception rate (P>0.5). Taken together, these data show that uterine involution is impaired in H compared to L strain cows, inasmuch as there is a greater degree of bacterial contamination and a more sluggish pattern of PFGM secretion in H cows. Collagen remodelling may also be attenuated in H than L cows, although differences between strains only tended towards significance. More work need to be carried out to further investigate the reason for these differences whether it is genetically based or higher production is negatively affecting the above mentioned traits at a cellular level.Item The characterisation of a longevity QTL in the New Zealand Holstein Friesian population : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Genetics at Massey University, Palmerston North, New Zealand(Massey University, 2002) Anderson, Jennifer MarieA large scale genome scan analysis to identify QTL relevant to commercial dairy cattle in New Zealand was undertaken using 7 large grandsire families. From this experiment a QTL site situated on bovine chromosome 23 (BTA23) for longevity was identified. The present study investigated this QTL in the subsequent generations. The addition of more markers to the region under question and the addition of grandsons to the analysis helped support the evidence that a QTL for longevity was indeed present within the region. However a more precise location was not identified. Although this is not helpful for marker assisted selection it will not affect the candidate gene search until the bovine genome sequence is available. This is due to the large inversion event within the BTA23 which means the target region in a comparative map search with HSA6 must still include the entire chromosome. Analysis of the granddaughters within these families confirmed a link between the speculative QTL site and variation in herd life but could not identify a cause for this variation at a phenotypic level despite a data set of over 800,000 animals. This result indicates that the variation in longevity is most likely the product of a variation in disease resistance at a sub clinical level. As ill health would impact on all production traits, animals affected would be removed for a variety of reasons. Because the only check of health in dairy cattle is their ability to be productive and remain in the herd it is impossible to identify these problems unless animals die from them. The MHC gene cluster lies within QTL identified and was the prime candidate for linked genes. Analysis of the DRB3 region in the two grandsire families showed a similar genotype in both grandsires. Genotype 1201 /090_ was common to both grandsires. Further analysis of the DRB3 by restriction endonuclease digest in the sons and grandsons showed that allele 1201 or alleles similar to 1201 were common in the population whilst alleles 090_ were not seen as often. Variation in phenotype for the 090_ allele suggested a more complex model than a simple inferior/superior allele relationship.Item Some effects of genotype on the conversion of pasture to milk by Friesian cows : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University(Massey University, 1982) Grainger, ChristopherThe New Zealand Dairy Industry has been aiming to bring about genetic improvement of dairy cattle by the use of genetically superior (progeny tested) bulls in the Artificial Breeding Scheme. There is evidence to show that there has been a genetic improvement in the level of milk fat production per cow, but little evidence to show the mechanisms by which the increase has been achieved. At present the genetic merit of a New Zealand cow for milk or milk fat production is measured by her breeding index (BI). The main objective of the work was to determine the mechanisms whereby cows of high BI produce more milk than cows of low BI. A total of 40 Friesian cows with high BI (approximately 125) or low BI (approximately 100 which is equivalent to the average cow in 1960) were identified and purchased from New Zealand dairy farmers. Experiments were carried out to determine the performance of high and low BI cows; when grazed as one group; when fed cut pasture individually in stalls at two levels of feeding; and when subjected to complete energy and nitrogen balances whilst lactating and non-lactating. Over the whole lactation, high BI cows produced more milk fat and gained less liveweight than low BI cows. The difference between BI groups in milk fat production was in close agreement with the expected differences based on BI's. Differences in liveweight changes between genotypes were not measurable in the short term (approximately five weeks) feeding experiments. One exception was in late lactation when high BI cows partitioned significantly (P <0.10) more metabolisable energy to milk at the expense of body tissue than the low BI cows. The two genotypes had similar intakes of fresh cut pasture offered ad libitum in stalls. However high BI cows ate, on average, 7% more pasture per unit metabolic liveweight than low BI cows, but the differences between genotypes in intake were significant only in two of the four indoor feeding experiments (P<0.05, P<0.10). There were no significant differences between BI groups in their ability to metabolise feed energy and in their efficiency of use of metabolisable energy (as measured by heat production at a given energy intake). There was one anomalous result during restricted feeding in early lactation when high BI cows produced less heat (P <0.05) at a common energy intake than low BI cows. Differences in nitrogen balance between genotypes were small and inconsistent. The feed required to maintain body condition and to promote a gain of body condition during the dry period was similar for both genotypes. The statistical methods developed in the course of analysing the experimental data were outlined in detail because it was considered that the analyses were more appropriate than those normally used. It was concluded that high BI cows produced more milk fat because they ate more and partitioned a higher proportion of their metabolisable energy intake to the synthesis of milk rather than to liveweight gain, than the low BI cows. The implications of the results were considered by making some preliminary predictions about the likely effect of genetic merit on farm productivity.Item Effects of crossbreeding and selection on the productivity and profitability of the New Zealand Dairy Industry : 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, 1998) López-Villalobos, Nicolás; López-Villalobos, NicolásThis aim of this thesis was to evaluate some effects of crossbreeding on the New Zealand dairy industry. The study started with a review of crossbreeding parameters, followed by the development of two models. A farm model was developed to evaluate the productivity and profitability (net income per hectare) of mating strategies involving the main breeds farmed in New Zealand; Holstein-Friesian (F), Jersey (J) and Ayrshire (A). Under current production costs and values for milk and beef, dairy herds using rotational crossbreeding systems had higher net income per hectare than straightbred herds. The ranking of mating strategies on profitability altered with changes in the relative values of fat and protein (1:4, 1:2.2 and 4:1) but rotational FJ and FJA herds had higher net incomes than straightbred herds across three values for the fat to protein ratio and two values for meat (current and 50% higher than current). An industry model was constructed to evaluate the effects of mating strategies on the rate of genetic gain and the productivity (yields of milk, fat and protein) of the dairy industry over 25 yr. The mating strategies simulated were upgrading to F (UPGF), upgrading to J (UPGJ), upgrading to A (UPGA), rotational crossbreeding using two or three breeds, and use of best bulls (UBB) irrespective of breed. Upgrading to either J or F increased the number of potential bull mothers from 0.27 million to 2.03 and 2.15 million and resulted in genetic gains of 0.27 genetic SD/yr, for both options. Rotational FJ decreased the number of potential bull mothers to 0.17 million and resulted in a genetic gain of 0.24 genetic SD/yr. Upgrading to F and UPGJ resulted in divergent averages of live weight and yields of milk, fat and protein per cow. On the basis of production per hectare, UPGF resulted in lower stocking rate, higher milk yield, and less fat and protein than UPGJ. Effects of the rotational FJ strategy on live weight per cow, and yields of milk per cow and per hectare, were slightly different from the average values for UPGJ and UPGF, due to the effects of heterosis. The farm and industry models were combined to calculate industry profit for the different mating strategies for 25 yr. Industry yields of standardised whole milk powder, butter and casein were calculated from industry yields of milk and its components. Profitability was calculated as income from dairy products and salvage animals less on-farm costs of production and off-farm costs of milk collection, manufacture and marketing. The ranking of the different mating strategies was affected by the value for butter. When marginal butter sales (above the total industry yield in the base year) were worth only NZ$0.45/kg, UPGF resulted in the highest industry net income (NZ$1119 million) followed by straightbreeding (NZ$1086 million) and rotational FJ (NZ$1076 million). However, if the marginal value of butter production was assumed to be equal to the average base value, then UPGJ resulted in the highest industry net income (NZ$1185 million) followed by rotational FJ (NZ$1177 million) and UBB (NZ$1173 million). Despite the widely different mating strategies used for 25 yr, the largest difference in net income was only 10%. Rotational crossbreeding systems can increase the profitability of commercial herds, but wide implementation of crossbreeding in the dairy industry reduces the number of active cows (bull mothers) and therefore penalises the rate of genetic gain of the entire population. Future values of dairy products have a major impact on the relative value of breeds and are therefore important to any decisions about mating strategies.Item A study of the interactions between Holstein-Friesian genotypes and feeding systems, with emphasis on system performance and cow grazing ability : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, New Zealand(Massey University, 2006) Rossi, José LuisImported genetic material of the Holstein-Friesian breed from overseas (OS), mainly from North America, has been used in New Zealand (NZ) since the late 1960's. This has diluted the genetic base of the former NZ Friesian genotype selected under intensive seasonal pasture-based systems. As a result, increased concerns have been raised about the negative influence of these overseas genes on the modern NZ Holstein- Friesian, as it is apparent that the OS Holstein-Friesian has a lower capacity to perform on grazed pasture. The objective of the present thesis was to investigate differences in production performance between three Holstein-Friesian genotypes farmed at different feed allowances (FA) on pasture-based systems; in addition, to investigate differences in the grazing process between strains under contrasting managements and sward conditions, and so to identify animal and pasture factors that affect the herbage intake (DMIH) and performance of the grazing cow. An accurate procedure was also established to estimate DMIH for cows fed forage and maize supplements, grazing in groups. Two modern high breeding worth (BW) Holstein-Friesian strains from NZ (NZ90) or overseas (OS90) origin and a low BW 1970's NZ Friesian genotype (NZ70) were farmed in two field experiments: (1) a long-term 'system' study that compared the yield performance of these genotypes in a range of systems with different feed allowance (FA) per cow, and a (2) a short-term 'component' study that compared the grazing capacity of the strains under contrasting sward conditions but at a common daily herbage allowance. The differences in productive performance between genotypes increased as the study progressed in the system study, with the largest observed in the last season. The mean milksolids (MS) yield per cow and per hectare were higher in NZ90 (395 kg cow-1 and 1,236 k ha-1) than in the NZ70 (336 kg cow-1 and 1,093 kg ha-1) and the OS90 (377 kg cow-1 and 1,154 kg ha-1). The higher production of NZ90 cows was supported by their higher mean daily MS yield than the NZ70 (1.45 vs. 1.21 kg MS cow-1 day-1) and more days in milk than OS90 cows (271 vs. 257 DIM). The lower lactation length of the OS90 strain occurred due to its lower body condition score (BCS) in late lactation, which determined an early dry-off for these cows. The lowest BCS of OS90 at the nadir (irrespective of FA), during lactation and at dry-off indicate these cows mobilised greater amount of body reserves and partitioned most of the energy ingested to yield. Genotype by FA interactions for milk and lactose yields, protein content in the milk and BCS were observed in the second and third seasons of the 'system' study. Milk yield increased as FA increased to a greater extent in OS90 than in the two NZ strains, whereas the content of solids in milk, particularly protein, increased to a greater extent for NZ90 than in both OS90 and NZ70. During lactation DMIH was higher for NZ90, intermediate in OS90 and lower in NZ70 (14.5, 13.9 and 12.6 kg DM cow-1 day-1 respectively for NZ90, OS90 and NZ70, as measured with nalkanes), and declined as lactation progressed, with a smaller difference for the total intake achieved (15.5, 15.2 and 13.1 kg DM cow-1 day-1 respectively) due to the increased supplement consumption. These results indicate that the OS90 needs more feed with a higher proportion of supplement in the diet to improve productive performance on pasture-based systems; the NZ90 would perform better when cow nutrition is mainly supported by grazing pasture, although further increments in performance could be expected from strategic supplementation, but requiring more feed than NZ70. The DMIH per unit of live weight (DMIH/LW) was highest in NZ90 strain in both the 'system' and in the short sward of the 'component' study (31.5 and 31.1 g DM kg-1 DM in NZ90 vs. 28.9 and 28.6 g DM kg-1 DM for OS90 in 'system' and 'component' studies respectively). The higher intake of NZ90 on pasture was sustained by a higher capacity to graze short swards than NZ70 and OS90, and to deal with the herbage of higher bulk density and lower quality present at the base of taller swards. The NZ90 can maintain DMIH in swards with different structures, indicating higher flexibility to perform under different managements and sward conditions. The size of the jaw is smaller in NZ90 than OS90 (88.4 vs. 92.4 mm) with effects on bite area and bite size, and this flexibility to adapt the size of the bite to swards of different structure may improve bite penetration under constraining sward conditions. The reduced ability of the OS90 to adjust ingestive behaviour to different swards would limit the capacity of this strain to perform on pasture. The fact that OS90 cows increased DMIH and DMIH/LW substantially in a leafy and taller sward (up to 21.6 kg cow-1 and 40.8 g DM kg-1Lw vs. 19.2 kg cow-1 and 41.0 g DM kg-1Lw in NZ90 during early lactation) suggests that yield performance can be improved in these cows even on pasture, by fine-tuning pasture management.Item Phenotypic relationships between milk protein percentage, reproductive performance and body condition score in Irish dairy cattle : a thesis presented in partial fulfilment of the requirements for the degree of Master of Sciences (MSc) at Massey University, Palmerston North, New Zealand(Massey University, 2009) Yang, LinnaA positive phenotypic correlation between milk protein percentage and reproductive performance in dairy cattle, especially during early lactation has been recently reported. The objective of this study was to quantify the relationship between milk protein percentage and different measures of fertility in Irish, seasonal calving, dairy cattle using data from experiments comparing strains of Holstein-Friesian cows under different feeding systems. The relationships between body condition score, milk production and fertility were also investigated. The data used in this study consisted of 584 lactation records over a 5-yr period. Principal component analysis and logistic regression was used to study the relationship between milk protein percentage and fertility performance of the cow. Greater milk protein percentage during the first 60 days post-calving was associated with better reproductive performance. The probability of a cow being submitted in the first 21 days of the breeding season increased with increased milk protein percentage during early lactation. Similarly, the probability of a cow becoming pregnant to its first service or to the whole breeding season also increased. Cows were classified as either high or low milk protein percentage based on their protein percentage over the whole lactation. Cows in the high milk protein group had a 7% greater conception rate compared to cows in the low protein percentage group. In conclusion, cows with higher protein percentage, especially during early lactation are submitted earlier in the breeding season, and have a higher conception rate. Physiologically, the shortage of glucose caused by negative energy balance restricts the synthesis of milk protein in the udder. On the other side, negative energy balance also causes the reduction of IGF-I, LH and oestradiol, which consequently delay the ovarian follicular development and finally reduces fertility. Therefore, there is a biological explanation for the association between milk protein percentage and fertility performance.