Praca oryginalna Original paper
Properly supervised reproduction within a herd of cows beneficially influences milk production profitability, course of breeding works, selection acuity, and determi-nes the level of milk performance. Taking into considera-tion lactaconsidera-tion yield and fertility it was demonstrated that high producing cows require at least a 100-120-day inter-pregnancy period (20). There is a common belief that the inter-calving period should last about 400 days (10). Cur-rently in Holland, an index of economical efficiency (EJR economischjaarresultaat) is used. It is a measure of the economical value of a herd that combines features con-nected with the milk yield of cows in a full lactation and those connected with the length of inter-calving period; with the elongation of this period the value of EJR index decreases (1, 16).
According to Swanson (21), in the case of high produ-cing cows the activity of the mammary gland has a priori-ty over the reproductive tract. However, there is a general conviction that symptoms of estrus are relatively poorly expressed in the case of high producing cows (15). One of the most important reasons for the decrease in fertility of cows is a silent estrus leading to some considerable economical losses caused by the elongation of inter-pre-gnancy period. From the research by Weller et al. (24) it may be concluded that fertilization before 60 days after
calving negatively influences milk yield not only in the current but in the consecutive lactation as well. More-over, it was demonstrated that in the case of high produ-cing cows there is a phenomenon of the spontaneous elon-gation of the interval to the occurrence of the first estrus after calving, caused by the energy deficiency during the period of increasing milk yield, that is in some manner a form of self-defense against premature pregnancy (4, 7). In the hierarchy of energy utilization after parturition, nutrients are destined to a larger degree for living needs and growth, especially in the case of younger cows, and for secretion of milk, than for the occurrence of the estrus cycle or the initiation of a new pregnancy (18).
The requirement for a good cow fertility is an early recognition of the periodical ovaries function after partu-rition. Its external manifestations are the occurrence of estrus and then fecundation. It is commonly emphasized that the reason for the deterioration of fertility indices in high producing cows are, on the one hand, nutritional mistakes made during the transient period, and the high milk yield and its consequences for health, on the other hand (4, 9).
The purpose of the present study was to compare the more important reproduction factors during the first five calvings of cows of Polish Holstein-Friesian breed of
Influence of the genotype of cows
on their fertility and economical value
MARIAN KUCZAJ, ROBERT KUPCZYÑSKI*, TADEUSZ STEFANIAK**, TADEUSZ SZULC Institute of Animal Breeding, *Department of Animal Hygiene and Ichtiology
University of Environmental and Life Sciences, Che³moñskiego 38C, 51-630 Wroc³aw, Poland **Department of Immunology and Veterinary Prevention, University of Environmental and Life Sciences,
C. K. Norwida 31, 50-375 Wroc³aw, Poland
Kuczaj M., Kupczyñski R., Stefaniak T., Szulc T.
Influence of the genotype of cows on their fertility and economical value
Summary
The research involved 432 cows, with an average yield of about 10 000 kg of milk in 305-day lactation, kept on a dairy cattle farm in south-western Poland. The aim of the work was a comparison of reproductive and economical features (EJR index economischjaarresultaat from Dutch) of Polish Holstein-Friesian breed cows of Black- and Red-White variety with a different contribution of genes of Holstein-Friesian (HF) breed cattle, after the first five calvings. The genotype of cows had a statistically significant influence (p £ 0.05, p £ 0.01) on the value of sexual rest, inter-pregnancy and inter-calving periods, and also the economical value expressed as the EJR index. It also significantly differentiated the magnitude of the fecundation index and sexual rest period, and economic value of the analyzed groups of cows. In cow herds, especially of Black-White breeds with a high contribution (> 87.5%) of HF cattle genes, the elongated sexual rest, inter-pregnancy and inter-calving periods, poorer survivability until subsequent calvings, and higher economical value (in euro) than in the case of their Red-White age mates should be expected. In heifer cows of high milk yield, lower reproductive feature indices (inter-pregnancy and inter-calving periods, fecundation index) and poorer economical value (EJR index) than in multiparous cows should be expected.
black- and red-white variety with different contributions of genes of Holstein-Friesian breed cattle. The cows analyzed came from a private farm and were utilized in identical environmental conditions.
Material and methods
The research material included data on the reproduction features of 432 cows of average milk yield at a level of about 10 000 kg in a 305-day lactation kept on a farm of dairy cattle situated in south-western Poland. The study covered cows that calved for the first time in the period between 1996-1999 and were utilized until March 2007. Information about reproduc-tion features and about the first five full lactareproduc-tions of the cows were obtained from farm breeding documentation and from the OBORA (COWHOUSE) computer system.
Cows of Black- and Red-White color were kept together in technological (nutritional) groups. Identical maintenance and management conditions and proper welfare were assured. The cows were kept indoors, in a free stall system, in the same feeding conditions based on TMR (Total Mixed Ration). Cows were milked three times a day (< 150 day of lactation) or two times (> 150 day of lactation), in two milking parlors of the side to side type.
The cows under analysis were divided into two breed sub-groups colored as follows: Black-White HO and Red-White RW, and into three genetic groups with different tions of Holstein-Friesian (hf) breed genes: 1 low contribu-tion (< 75%), 2 medium contribucontribu-tion (from 75.1 to 87.5%), 3 high contribution (> 87.5%).
The assessment of herd fertility was conducted based on chosen reproductive features of cows after the first five cal-vings, i.e. length of the following periods: sexual rest (SRP), inter-pregnancy (IPP) and inter-calving (ICP) and on fecunda-tion index (FI), i.e. the number of inseminafecunda-tion treatments re-quired for successful impregnation. The survivability of cows until particular calvings (%), that is at the same time the pictu-re of the dynamics of their culling, was calculated on the basis of the animals survival until the end of the first 305-lactation assumed as 100%.
The economical value was expressed as an index of the eco-nomical efficiency of cows (EJR), also called the Annual Eco-nomical Result (in euro), which is inseparably connected with cow fertility, according to a formula commonly used in Hol-land (1, 16):
EJR (euro) = (X1) + (X2) + (X3) where: X1 = kg of milk/ICP × 365 × (0.06 euro/kg),
X2 = kg of fat/ICP × 365 × 2.70 euro/kg, X3 = kg of protein/ICP × 365 × 5.85 euro/kg.
The index was calculated by dividing the yield of milk, fat and protein (in kg) obtained in full lactations by the length of inter-calving periods, and then by multiplying the obtained results by 365 days. Thus obtained results, separately for milk, fat and protein, were multiplied by the adequate economical value (used in Holland), and then summed up. This way the economical values of cows (in euro) after five subsequent calvings were calculated.
The data were analyzed statistically using Statistica PL soft-ware. The significance of differences between mean values was verified using the Duncan test. Differences between analyzed groups were expressed as absolute and relative values. The dynamics of changes (in %) in research groups after particular calvings (reproduction cycles) was determined in relation to the value of reproductive and economical features of cows after first calving that were assumed as 100%.
Results and discussion
Table 1 presents the mean values of reproductive and economical features (EJR) of Black- and Red-White cows after the first five calvings.
Statistically significant differences were observed be-tween breed sub-groups of cows (with p £ 0.05, p £ 0.01) in the case of values of II inter-calving period (the dif-ference was 24.0 days, relative value 5.6%), II inter--pregnancy period (22.0 days, 14.5%) II sexual rest period (16.3 days, 18.9%), III sexual rest period (12.2 days, 13.6%). The economical value of cows (EJR) was statistically significant differentiated after consecutive calvings: II (280.4 euro, relative value 10.5%), III (338.2 euro, 12.1%) and IV (358.1 euro, 13.3%).
There were no statistically significant differences in the case of the fecundation index and the length of pregnan-cy between groups of cows in the five consecutive repro-duction cycles.
Black-White cows were characterized by longer (less profitable) inter-calving periods (except for IV ICP), and inter-pregnancy periods than their Red-White age mates. Heifer cows of both breed sub-groups were characterized by slightly longer ICP and IPP than multiparous cows. With respect to Black-White heifer cows, the lowest ICP values (of 3.7%) and IPP (of 1.7%) were noted after III calving. In turn, Red-White cows after the IV calving sur-passed heifer cows in terms of values of inter-calving (of 3.1%) and inter-pregnancy periods (of 7.8%). The ten-dency for the occurrence of shorter inter-calving periods in the case of Red-White cows (411.7 days) compared to their black-white age mates (426.1 days) has also been observed in another research project (12). ICP values ob-served in this research were considerably higher than ones observed in research of other scholars (6). In the cited work, the authors concluded that with the yield exceeding 7000 kg of milk from a cow during a lactation period, the mean length of IPP in the case of heifer and multiparous cows was 417 and 423 days, respectively. It was obser-ved in Polish conditions (17) that cows whose first inter-calving period lasted 461-490 days used to live the lon-gest. They were also utilized for the longest time, and the greatest amount of milk was obtained during their lifetime. Results obtained in the current research concerning the length of inter-pregnancy periods in the case of Black-and Red-White cows were close to values considered as optimal (2, 11, 20, 25). In Polish conditions (11) it has been reported that the elongation of IPP even to 160 days did not negatively influence either the milk yield, or the content of its main components during 305-day lactation. It was observed in present research that sexual rest pe-riod in both groups of cows was longer than that believed to be optimal; it should last from 40 to 70 days (19). This analyzed feature in the case of Black-White cows in all 5 reproduction cycles was longer than in the case of their Red-White age mates. The sexual rest period in multi-parous cows was considerably longer compared to heifer cows. In relation to I calving, the longest sexual rest periods were observed for Black-White cows after III (of 14.8%), and in Red-White after IV (of 13.0%) calving.
In the analyzed cows, the observed value of the fecun-dation index (2.1-2.8) in particular reproduction cycles
was not sufficient (the ideal value is 1.0). In the case of Black-White cows, the biggest amount of insemination treatments for one successful fecundation (2.8) was ob-served after I, and the lowest (2.1) after III calving. In the case of their Red-White age mates the highest value of this index (2.7) was after IV, and the lowest (2.4) after III and V calving. With respect to heifer cows (as 100%), the poorest fecundation index was noted in the case of Red--White cows after II (104.0%) and IV (108.0%) calving, while the best ones for Black-White cows after III cal-ving (75.0%). The results of numerous authors research (6, 10, 22) point the common occurrence of unbeneficial insemination indices in dairy cattle breeding. In condi-tions of intensive milk production, the average number of insemination treatments required to obtain a pregnancy in heifer and multiparous cows was 2.4 and 2.6, respecti-vely (6).
The length of pregnancy periods of analyzed cows was in a range considered as appropriate. The values of this feature, in the case of Black-White heifers (277.7 days) and Red-White ones (278.7 days), and also in multiparous cows were similar. The last pregnancy in Red-White cows was longer by 3.0 days (1.1% of relative value) compared to their Black-White age mates.
Higher economical value (EJR index) in five subse-quent reproductive cycles was obtained by Black-White cows as compared to their Red-White age mates. The least differences in EJR index were observed in heifer cows (the difference was 94.2 euro, relative value 4.2%), and the highest after IV calving (358.1 euro, 13.3%). The smallest EJR index values were noted for Black-White (2218.5 euro) and Red-White (2124.3 euro) heifer cows. The values of this index increased with the age of cows until III calving, and then slowly decreased. In relation to I calving, the peak values were obtained by Black-White (of 25.9%) and Red-White cows (15.6%) after III calving. Economic values of analyzed cows in Poland are a bit lower than ones observed in Holland. The first position in the 2004/2005 season in a ranking of Dutch cowhouses
classified according to EJR index was obtained by a herd with a result of 3132 euro (16).
The survivability of cows until particular calvings, re-presenting the dynamics of their culling, was more profit-able in the group of Red-White cows. Until the fifth cal-ving, the survival of Black- and Red-White cows was 10.2% and 13.1%, respectively. The intensive rate of both groups of cow culling, especially after II and III calving, forces the farmer to incur considerable costs in herd re-placement. The positive side of this phenomenon is the opportunity to achieve bigger genetic progress (the sub-sequent generation has a higher genetic value as a result of selection). However, the negative side of a high repro-duction percentage in cow foundation stock is the incre-ase in costs of milk production resulting from the costs of the rearing (purchase) of replacement heifers. In the rese-arch by Dorynek et al. (5) the highest contribution among culling cows of HF breed was presented by animals that were culled from a herd in the first lactation (26.0%), in the second (24.7%) and third lactation (20.1%). There is a common opinion that milk producers should necessari-ly tend towards the decrease in the replacement level of a herd below 30%, thus leading to an elongation of cow utilization time (23).
Table 2 presents the mean values of analyzed repro-ductive traits and the EJR index of different genotype cows in five subsequent reproductive cycles. The statistically significant influence of the contribution of HF cattle ge-nes on the range of differences in reproductive trait values (sexual rest period and fecundation index) and EJR index was observed. No statistically significant differences were noted in the case of pregnancy length, inter-pregnancy and inter-calving periods.
Statistically significant differences (with p £ 0.01) in the values of sexual rest were determined after the follo-wing calvings: II between groups 1-3 (the difference was 14.0 days, relative value 19.0%) and 2-3 (13.0 days, 17.4%); III between groups 1-3 (16.5 days, 21.3%) and 2-3 (11.2 days, 13.5%), and V between groups 1-3 (23.3
Tab. 1. Mean values of reproductive features (x, ± s) and EJR index and survavibality of Black- and Red-White cows until subsequent calvings (%) e r u t a e F g n i v l a c f o r e b m u N I II III IV V O H 1 RW2 HO RW HO RW HO RW HO RW d o ir e p g n i v l a c -r e t n I ) s y a d ( xs 49351..18 49174..86 48320..51 48036..01 46166..30 47077..27 47275..65 47257..24 47320.9.1 47095..06 y c n a n g e r p -r e t n I ) s y a d ( d o ir e p xs 19544..87 19377..86 18501..63 18229..73 16348..59 17370..35 17499..17 17448.6.3 17533.3.4 17286..72 x e d n i n o it a d n u c e F xs 21..98 22..05 21..76 22..60 21..31 21..46 21..56 12..67 21..65 21..43 f o h t g n e L ) s y a d ( y c n a n g e r p xs 2757.6.7 257.83.7 2768.0.3 2758.1.2 2757.3.4 2758.9.0 2678.2.1 267.70.7 274.78.0 2850.4.0 d o ir e p t s e r l a u x e S ) s y a d ( xs 3708..41 7312..34 86.4 a A 2 . 2 3 70.1 b B 7 . 3 2 89.7 a A 7 . 4 3 77.5 b B 9 . 3 2 8255..74 8211..07 2827..56 7159..91 ) o r u e ( x e d n i R J E xs 2526188..85 2513254..83 2675392..76Aa 2367597..34Bb 2769143..17Aa 2475152..99Bb 2668375..59Aa 2362395..48Bb 2860079..62 2447191..05 li t n u y ti li b a v i v r u S g n i v l a c t n e u q e s b u s %n 110906.0 120306.0 6193.79 6196.31 4709.3 4140.55 1398.4 2547.1 1200.2 1331.1
days, 30.9%) and 2-3 (20.7 days, 26.6%), and also in the case of fecundation index after I calving between groups 1-2 (0.4, 16.7%) and 1-3 (0.5, 20.8%). The statistically significant differences (with p £ 0.05, p £ 0.01) in the economic value of cows (EJR) were observed after follo-wing calvings: I between groups 1-3 (difference was 268.3 euro, relative value 12.9%), 2-3 (201.4 euro, 9.4%), II between 1-2 (324.4 euro, 14.2%), 1-3 (533.0 euro, 23.4%) and III between groups 1-2 (208.9 euro, 8.5%) and 1-3 (326.0 euro, 13.2%).
With the increasing contribution of HF cattle genes in cow genotypes, the statistically insignificant decrease in ICP and IPP was observed. The longest inter-calving and inter-pregnancy periods in subsequent reproductive cy-cles were noted for cows of the 3rd genetic group (except
for IV calving). However, the shortest (more beneficial) ICP and IPP in particular reproductive cycles were deter-mined in the case of cows from the 1st genetic group
(except for II calving). The suggestions made by some authors (3, 8, 14) concerning poorer fertility of crossbred cows, especially those of high HF cattle genes contribu-tion compared to their White-Black age mates with the low contribution of HF genes, were confirmed in the pre-sent research.
As regards the inter-calving periods, the biggest diffe-rence was observed in the IV reproduction cycle between groups 1-2 (difference was 30 days, relative value 7.2%), and the smallest in the III cycle between groups 1-2 (4 days, 1.0%). In relation to I ICP (assumed as 100%) the extreme values of the analyzed parameter were noted
for the 2nd genetic group after II (96.6%) and IV (104.8%)
calving.
In values of the inter-pregnancy period, the biggest dif-ference was determined after V calving between groups 1-3 (31.1 days, 24.4%), and the lowest one after III cal-ving between groups 1-2 (3.6 days, 2.8%). With respect to I IPP (assumed as 100%) the highest value of analyzed parameter occurred after IV calving in group 2 (113.1%), and the lowest after II and III calving in groups 2 (90.2%) and 3 (90.2%). The values of IPP obtained in the present study are similar to results obtained by Litwiñczuk et al. (14), and higher than that observed by Strza³kowska et al. (20). The authors of the latter work noted that the opti-mum length of IPP in the case of cows producing about 9000 kg of milk in lactation should be 110 days, as this decreases problems with high producing cows drying off, and contributes to their welfare improvement.
The shortest periods of sexual rest were noted in group 1, a bit longer ones in group 2, while the longest (the least profitable) in the 3rd genetic group. The length of sexual
rest period increased with the age of cows. The shortest periods were observed in the case of heifer cows in all three groups (except for group 1 after II and V calving). With respect to I calving, the longest periods of the featu-re under discussion wefeatu-re noted in the 1st genetic group (of
8.5% after IV calving), in 2nd group (of 13.4% after III
calving) and in 3rd group (of 28.9% after V calving). It
was observed in another research project (13) that the best value of fecundation index (1.87) was obtained in the case of cows with the shortest sexual rest period (to 60 days).
Tab. 2. Mean values of reproductive features (x, ± s) and EJR index of different genotype cows in subsequent calvings
e r u t a e F Genotype g n i v l a c f o r e b m u N I II III IV V x s x s x s x s x s g n i v l a c -r e t n I ) s y a d ( d o ir e p 1 414.1 92.8 414.2 83.5 406.9 80.2 414.1 65.0 407.1 75.9 2 423.7 99.7 409.4 76.1 410.9 61.7 444.1 96.7 416.9 89.9 3 435.2 99.4 429.3 89.8 420.7 69.2 433.7 67.5 436.5 65.3 y c n a n g e r p -r e t n I ) s y a d ( d o ir e p 1 136.9 92.9 136.5 82.9 130.1 80.1 135.2 64.6 127.5 76.7 2 146.8 99.9 132.4 76.7 133.7 60.9 166.1 96.2 141.4 89.2 3 158.3 99.1 151.1 86.2 142.8 67.4 158.7 69.6 158.6 64.4 n o it a d n u c e F x e d n i 1 2.4Bb 1.9 2.7 1.9 2.3 1.5 2.4 1.3 2.3 1.3 2 2.8abA 2.0 2.5 2.0 2.3 1.5 2.9 1.8 2.6 1.4 3 2.9Aa 2.0 2.6 1.7 2.1 1.3 2.8 1.9 2.7 1.6 h t g n e L y c n a n g e r p f o ) s y a d ( 1 278.7 5.5 278.5 5.8 277.8 6.1 277.9 5.6 279.6 5.5 2 277.9 5.0 278.2 5.8 277.8 5.3 277.5 6.6 278.7 5.3 3 277.8 5.8 277.8 5.0 277.7 5.1 277.7 6.9 277.2 4.8 t s e r l a u x e S ) s y a d ( d o ir e p 1 75.4 32.1 73.5Bb 27.8 77.4Bb 28.4 81.8 20.8 75.3Bb 20.0 2 72.9 33.8 74.5Bb 24.6 82.7ABb 19.9 81.8 27.2 77.9Bb 17.9 3 76.5 26.1 87.5Aa 32.9 93.9Aa 37.9 88.3 22.2 98.6Aa 19.2 x e d n i R J E ) o r u e ( 1 2076.9Bb 540.5 2279.1Bc 684.3 2465.9Ab 739.7 2303.2 666.8 2473.7 635.1 2 2143.8Bb 531.6 2603.5Ab 636.3 2674.8Aab 663.8 2653.8 600.5 2577.4 569.1 3 2345.2Aa 556.6 2812.1Aa 665.8 2791.9Aa 562.6 2635.7 625.5 2427.5 726.9 Explanations: Mean values of analysed features differ significantly within the columns (a, b p £ 0.05, A, B p £ 0.01)
The number of insemination treatments required to ob-tain a pregnancy (2.1-2.9) during the analyzed period of the cows lifetime, was quite differentiated within analy-zed groups of animals; however, the observed differences were statistically insignificant (except for I calving). The highest values of insemination index were noted after the following calvings: I in group 3 (2.9) and IV in group 2 (2.9), while the lowest ones after III calving in group 3 (2.1). In numerous research (8, 10) any strict relationship between fertility indices and a contribution of HF cattle genes in their genotypes was observed. However, in the research by Litwiñczuk et al. (14), all analyzed reproduc-tion features deteriorated with the increase in HF cattle genes contribution. Larsson and Berglund (13) report that the number of insemination treatments for one pregnancy was lower if the length of inter-calving period was 15 months, compared to a period of 12 months.
The economic value of cows rose with the increase in HF cattle genes contribution in their genotypes (except for V calving). After V calving, the smallest (the worst) economical value was obtained in the case of cows from group 3; the difference between the groups 1-3 was only 46.2 euro (1.9% of relative value). Heifer cows of the three genotypes were characterized by a considerably lower economical value comparing to multiparous cows (2076.9, 2143.8 and 2345.2 euro, respectively). Compa-ring to the I calving, the EJR index obtained a maximum growth of economical value in following genetic groups: 1 (of 19.1% after V, and of 18.7% after III calving), 2 (of 24.8% after III calving), and in 3 (of 19.9% after II, and of 19.0% after III calving).
The survivability of cows of different genotypes to particular calvings is presented in table 3. It may be con-cluded that among analyzed groups of animals until V calving, the lowest survivability (8.7%) was in the case of cows with the high contribution of HF cattle genes (> 87.5%), while the highest one (14.8%) was for cows with lower contribution of HF cattle genes (< 75.0%). Results obtained by other authors (8) likewise prove the distinct increase in percentage of culled cows with the increase of HF cattle genes contribution in their genotype.
Conclusions
1. Genotype of cows had a statistically significant in-fluence (p £ 0.05, p £ 0.01) on the value of sexual rest, inter-pregnancy and inter-calving periods, and also on the economical value expressed as EJR index. It likewise significantly differentiated the magnitude of the
fecunda-tion index and sexual rest period, and economic value of analyzed groups of cows.
2. In a herd of cows especially Black-White with a high contribution (> 87.5%) of hf genes, more elonga-ted periods of sexual rest, pregnancy and inter--calving, and also higher economical value (EJR index) comparing to red-white age mates should be expected.
3. In the case of heifer cows of high milk yield, the poorer indices of reproductive (pregnancy, inter--calving periods, fecundation index), and economic features (EJR index) should be expected compared to multiparous cows after subsequent calvings.
4. The survivability until subsequent lactations was more profitable in red-white cows than in their black-white age mates.
5. The use of EJR index (in euro) in Polish conditions is justified, as it allows an assessment of economic value of cows in subsequent production cycles, taking into account values of milk performance features and the length of inter-calving periods at the same time.
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Authors address: dr hab. Marian Kuczaj, prof. nadzw., ul. Che³moñ-skiego 38c, 51-630 Wroc³aw, Poland; e-mail: marian.kuczaj@up.wroc.pl Tab. 3. Survivability of cows with different contribution of hf
cattle genes until subsequent calvings
g n i v l a C ) % ( s e n e g f h f o n o it u b ir t n o C 0 . 5 7 < 75.1-87.5 >87.5 n % n % n % 1 1961 100.01 1211 100.01 1151 100.01 2 1411 71.9 78 64.5 81 70.4 3 89 45.4 52 43.0 43 37.4 4 48 24.5 26 21.5 21 18.3 5 29 14.8 12 19.9 10 18.7
